Table of Content

12 January 2006, Volume 32 Issue 01

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ORIGINAL PAPERS

Ill-conditioned Matrix and Its Improvement in Regression

MO Hui-Dong

Acta Agron Sin. 2006, 32(01):  1-6. 

Abstract ( 2190 )   PDF (402KB) ( 1318 )   Save

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in regression analysis, the information matrix X'X is an important factor because of b=(X'X)^-1 X'Y. If the determinant value of X'X, det(X'X), is close to zero ,the inverse of the X'X, (X'X)^-1, will extremely inflate, the error mean square for regression coefficient will largely increase, and in consequence the regression fitting will be poor robustness and low precision. Thus the matrix X'X of det(X'X)≈0 is called “ill-conditioned matrix”. In this paper the determinant value of correlative matrix R of x variables, det(R), is used as a synthetic index for ill-conditioning, i.e. if the det(R) lies in the intervals [-0.01,0.01] and [-0.0001,0.0001] but nonzero, the corresponding matrix X'X can be regarded as ill-conditioned and seriously ill-conditioned, respectively. The ill-conditioned results from the linear dependency among columns in matrix. Three diagnostic criteria, including linear correlation coefficient, multiple determination coefficient and condition index, can measure the degree of the column dependency. In order to improve or eliminate the ill-conditioning of , four methods, i.e. (1) to reduce the original regression model, (2) to collect the new data, (3) to add the restrictive condition for regression coefficients and (4) to adopt the non –customary regression procedure such as the ridge regression and the generalized inverse regression, are suggested. The importance of diagnosing the ill-conditioning and the evaluation for improved ill-conditioning are also discussed briefly.

QTL Analysis of Maize (Zea mays L.) Embryo Culturing Capacity

PAN Guang-Tang;ZHANG Zhi-Ming;WEI Xin;SONG Yun;ZHAO Mao-Jun;XIA Yan-Li;RONG Ting-Zhao

Acta Agron Sin. 2006, 32(01):  7-13. 

Abstract ( 1930 )   PDF (527KB) ( 1160 )   Save

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The good acceptors for maize transgenic engineering are insufficient in our country, especially in the southwest mountain areas of China. The hereditary variation regularity of maize culture capacity is not very clear. The efficiency of embryonic callus induction and the number of regenerated plantlet were used as the characters of the maize culture capacity in this research. A genetic linkage map was constructed using 88 simple sequence repeat (SSR) markers on a maize (Zea mays L.) population consisting of 202 F2 individuals derived from the cross between the inbreds 18-599 (red) (higher culture capacity) and R15 (lower culture capacity). The SSR map covers 1 636.6 cM over the ten chromosomes, with an average interval length of 18.60 cM (Fig.3) with software MAPMAKER version 3.0b. The immature embryos from the population of 202 F₂﹕3﹕4 lines were evaluated in two traits which were in a normal distribution based on the investigated values (Table 1, Fig.1 and Fig.2). With the method of composite interval mapping (CIM) described in QTL Cartographer V2.0 procedure, 5 quantitative trait loci (QTL) were identified for efficiency of embryonic callus induction, on chromosomes 1, 3, 7 and 8 respectively, accounting for phenotypic variation from 5.25% to 23.4% (Table 2); one QTL was revealed for number of regenerated plantlet on chromosome 3 and explained the phenotypic variation of 13.42%. Combining the marker assisted selection (MAS) method, the necessity and possibility will be enhanced greatly to transferring the high-culture capacity as well as to accurately location, clone and transformation of the main effect QTL of these two characters.

Stable Expression of QTL for AC and PC of Milled Rice (Oryza sativa L.) Using a CSSL Population

WENG Jian-Feng;WAN Xiang-Yuan;WU Xiu-Ju;WANG Hai-Lian;ZHAI Hu-Qu and WAN Jian-Min

Acta Agron Sin. 2006, 32(01):  14-19. 

Abstract ( 2150 )   PDF (432KB) ( 1058 )   Save

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A chromosome segment substitution lines population, derived from Asominori/IR24 with Asominori as the recurrent parent, was planted and phenotyped for amylose content (AC) and protein content (PC) of milled rice in two successive years and four sites. QTL for AC and PC were characterized and stability of their expression was investigated. The phenotypic value for AC and PC showed a continuous distribution and some transgressive lines were also observed. Additionally, a total of 8 QTL for two quality traits were identified, and two of them were consistently detected in the eight different environments. Phenotypic values were different significantly (P<0.01) between Asominori and the CSSLs harboring any of the two QTL alleles. Otherwise， the significant QTL by environment interactions were observed for qAC-8 and qPC-8 in two of the eight environments. Therefore, these results indicated that the two QTL, qAC-8 for AC and qPC-8 for PC, were stably expressed in different environments. Since QTL qAC-8 and qPC-8 were both mapped in the G1149–R727 interval, the two RFLP markers, namely G1149 and R727, would be useful markers for further fine mapping of QTL and marker-assisted selection (MAS) through marker conversion in rice quality improvement.

Response of Fertility of Different Generational TGMS Lines 96-5-2S to Low Temperature in Rice

XU Meng-Liang; KANG Gong-Ping; LIANG Man-Zhong and CHEN Liang-Bi

Acta Agron Sin. 2006, 32(01):  20-24. 

Abstract ( 1910 )   PDF (399KB) ( 1019 )   Save

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In order to explore the genetic stability of critical temperature inducing male sterility of TGMS(thermo-sensitive genic male sterile) line , the response differences of fertility of consecutive 6 generational TGMS lines of 96-5-2S (developed from Pei’ai64S) to low temperature were studied in rice. The results were as follows: (1) All generational 96-5-2S lines were sterile with zero of selfed seed set setting rate and 0–0.9% of stainable pollen grains when they were treated with artificial cold water of constant 23.5℃(water depth 20 cm about) for 10 days or met natural cold air of average daily mean temperature 22.9–23.1℃(average daily minimum temperature 21.7–22.0℃) for 2–3 days at their thermo-sensitive stages inducing male fertility alternation(Table 1 and 2). (2) All generational 96-5-2S lines were fertile with 0.2%–7.1% of selfed seed setting rate and 1.1%–19.5% of stainable pollen grains when they were treated with artificial cold water of constant 21℃ and 22℃ for 10 days or natural cold air of average daily mean temperature 22.9℃(average daily minimum temperature 20.7℃) for 4 days at the same thermo-sensitive stages, but the selfed seed setting rate and stainable pollen grains percentage are different among different generations. As the multiplication generation increased, the bagged seed set and stainable pollen grains got more, and those of the 5th or 6th generation were significantly high than those of the first generation. (3) The selfed seed setting rate and stainable pollen grains percentage of Pei’ai64S (control) were much significantly higher than those of all generational 96-5-2S lines under the same low temperature condition. Based on above results, it is confident that the critical temperature of TGMS lines of 96-5-2S is genetically changeable slowly with the multiplication generation increase ,and this change will be obviously shown on the percentages of stainable pollen grains and selfed seed setting when 96-5-2S multiplicate to 5th or 6th generation respectively. However, the difference of critical temperature of 96-5-2S among different generations caused by genetically drift is less than that between 96-5-2S and Pei’ai64S. Therefore, it is a very important effective way to decrease critical temperature through pureline selection from the TGMS line population, which has relatively higher critical temperature.

Dynamic Changes of Plant Hormones in Developing Grains at Rice Filling Stage under Different Temperatures

WANG Feng; CHENG Fang-Min; LIU Yi; ZHONG Lian-Jin and ZHANG Guo-Ping

Acta Agron Sin. 2006, 32(01):  25-29. 

Abstract ( 2155 )   PDF (342KB) ( 1333 )   Save

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Temperature at grain filling stage has great impact on grain development. It has been well known that high percentage of chalky grains, poor cooking and eating quality may be caused by high temperature during the filling period, which is probably attributed to the shortened duration of grain filling, the low photosynthesis rate and activity changes of some enzymes relevant to grain filling. However, little information has been known about the effect of temperature on main endogenous hormones in developing grains at filling stage, which commonly play an important role in grain development as a growth signal. In this paper, two temperature treatments, i.e. daily average temperature 32℃(High) and 22℃(Optimum), were established to compare the difference in the endogenous hormone levels between two temperature treatments with two early indica rice cultivars applied, aiming to recognize the relationship between the effect of temperature on grain development and the response of endogenous hormone in grains to temperature. The results showed that by higher temperature, grain development was accelerated at early grain-filling stage, and the grain filling duration was shortened (Fig.1). The contents of IAA, ZR, and GA₃ in developing rice grains were dramatically reduced at early grain filling stage when the plants were exposed to higher temperature, while a little difference was found in their contents between two temperature treatments at later stage (Fig.2–4). Compared with optimum temperature treatment, there was much higher ABA content in developing grains throughout the whole filling stage in high temperature treatment in spite of remarkable difference between cultivars (Fig.5). Considering effect of temperature on grain filling process and its relation with hormones levels in developing grain, it could be deduced that the acceleration of grain development and the shortening of grain filling duration should be ascribed to the reduction in IAA, ZR, GA3 contents and the increase in ABA content in developing grains at early grain-filling stage when rice plants exposed to high temperature.

Creation of Novel Wheat-rye 1BS/1RS Translocation Lines and Characterization by Molecular Cytogenetics

WANG Jing; WANG Xian-Ping; JI Jun; WANG Zhi-Guo; AN Diao-Guo; LI Jun-Ming and ZHANG Xiang-Qi

Acta Agron Sin. 2006, 32(01):  30-33. 

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The wheat-rye 1RS/1BL translocation has made a great contribution to the wheat production in the world since the Green Revolution. The 1RS/1BL translocations, for the existence of the short arm of rye(Secale cereale L．) chromosome 1R, often have many good traits such as high yield potential, multi-resistance to diseases and good adaptation to acid soil. Many studies also illustrated that 1RS carries a lot of rust resistance genes (Sr31, Lr26, Yr9) and powdery mildew resistance gene (Pm8). As a result, the short arm of 1R is frequently used as alien chromatin in wheat (Triticum aestivum L．) improvement.
But one major concern about this translocation recently is its single origin, with the consequence being loss of resistances to new races of stripe rust and powdery mildew. The other concern is that most of wheat cultivars carrying this chromosome arm were shown a defective grain quality, in particular, sticky dough and a reduction in dough strength. The reduction in dough strength was thought to be due to the presence of monomeric secalins from rye (Sec-1) and the substitution of glutenins and gliadins (Glu-3 and Gli-1).
In order to develop new potentially usable disease resistant alien germplasm and improve the quality of 1RS/1BL translocations, cross was carried out between the Triticum aestivum L．cv．“Xiaoyan 6” and Secale cereale L．cv．“German White”. “German White” is a winter rye cultivar which is immune from stripe rust and powdery mildew. “Xiaoyan 6” is an elite winter wheat cultivar derived from the cross common wheat × Thinopyrum ponticum (2n=70). It possesses the characteristics of good processing quality, high yield potential, earliness, good stress tolerance and wide adaptation.
Wheat-rye hybrids between “Xiaoyan 6” and “German White” were obtained in 1994. The F₁ were treated with colchicines. The F₂ and the subsequent generations were self-crossed and planted in the field. Each individual plant was selected with the qualities of seed set, wheat-like plant type and good resistance to rust and powdery mildew. A set of wheat-rye germplasm with resistances to rust and powdery mildew were bred. In order to identify genetic basis of these resistant lines, sequential C-banding–GISH (genomic in situ hybridization) was employed to analyze the chromosome compositions in somatic cells. As a result, two 1RS/1BL homozygous translocation lines BC152-1-1 and BC01-89-1 were selected. One of them, BC152-1-1 had a chromosome number of 2n=42 in somatic cell and its chromosome composition were 40 normal wheat chromosomes and one pair of 1RS/1BL Robertsonian translocation chromosomes (PlateⅠ-A,B). The other one, BC01-89-1 (2n=43) was a 1RS/1BL Robertsonian translocation line added one 3R chromosome with both terminal deletions (PlateⅠ-C,D). In addition, the high-molecular-weight glutenin subunits (HMW-GS) in endosperm and major quality characteristics of “Xiaoyan 6”, BC152-1-1 and BC01-89-1 were analyzed. The results showed that BC152-1-1 and BC01-89-1 carried HMW-GS 14+15 derived from “Xiaoyan 6” (Fig.1), and their grain protein content, wet gluten content and SDS sedimentation value were greatly improved.

Acquired Chlorophyll Concentration of Cotton Leaves with Technology of Machine Vision

WANG Ke-Ru;LI Shao-Kun;WANG Chong-Tao;YANG Lei;XIE Rei-Zhi;GAO Shi-Ju and BAI Jun-Hua

Acta Agron Sin. 2006, 32(01):  34-40. 

Abstract ( 1987 )   PDF (472KB) ( 1112 )   Save

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The technology of machine vision monitoring crop morphological and physiological status has been tremendous potential by applied with its advantage of simple, convenient, quick, nondestructive and no-site measurement. The color characteristics of leaf as better indexes have been used to diagnose the nutrition status of wheat and rice in field condition. A field study was conducted at the Experiment Station of Institute of Crop Sciences, CAAS in 2004, with cotton. The study aimed at predicting chlorophyll concentration under field conditions using the machine vision technology, establishing the foundation to make the portable field diagnosed instruments of measuring chlorophyll. The images of leaf were taken by digital camera at the boll forming and the beginning of boll opening stage, respectively. The color characteristics of leaf images were extracted with the image processing software. The data showed that the significant positive correlations were found between the B, B/R, b, b/r and chlorophyll concentration (Table 1 and Fig.1) in the RGB system and between the saturation(S) and chlorophyll concentration (Fig.2) in the HIS color system, which were highly consistent (Table 4) for both sides of leaf. The correlated degree with chlorophyll was higher when the color parameters were transformed. The B, B/R, B, b/r and S of cotton leaf could be used as an easy and fast tool to predict chlorophyll content. Furthermore, 12 sets statistic correlation model with color characteristics were developed (Table 2, 3), and six of them were chosen according to the determination coefficients. The predicted accuracy of six sets model were tested, the related error was from 7.8 to 13.65% (Table 5). The predicated accuracy is higher than that of SPAD in the whole leaf level. These influenced factors on predicted accuracy such as camera condition, cotton variety, water and nutrition were discussed. How the applications of the method are extended from single leaf to canopy level needs to be studied farther.

QTL Mapping for Kernel Yellow Pigment Content in Common Wheat

ZHANG Li-Ping;YAN Jun;XIA Xian-Chun;HE Zhong-Hu and Mark W. Sutherland

Acta Agron Sin. 2006, 32(01):  41-45. 

Abstract ( 2269 )   PDF (336KB) ( 1040 )   Save

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Flour yellowness b* is a major criterion to estimate flour colour, which is basically determined by yellow pigment content in wheat grains. A doubled haploid (DH) population with 71 lines derived from a cross between Zhongyou 9507 with lower flour yellowness b* and CA9632 with higher flour yellowness b*, was sown for two years in 5 locations. A total of 173 loci including 122 SSR, 4 STS of storage protein genes and 10 AFLP markers were used to construct a linkage map, covering 2 881 cM of whole genome at 21 linkage groups. With the method of composite interval mapping (CIM), 8 putative major QTL of yellowness b* were detected on chromosomes 1DS, 2DL, 3A, 4D, 5D, 6AL, 6D and 7AL (Table 2), and 5 putative QTL of yellow pigment content were detected on chromosome 2DL, 3DL, 4A, 5A and 7AL (Table 3), respectively. The QTL on 7AL was common for yellowness b* and yellow pigment content, accounting for 12.9%–37.6% and 12.1%–33.9% of the phenotypic variance across different environments, respectively, which was closely linked to Xgwm264b. The genetic distance between Xgwm264b and the QTL of flour yellowness b* and grain yellow pigment on chromosome 7AL were 0–3.9 cM and 0–0.9 cM, respectively. It can be used as a molecular marker in wheat breeding program.

Cloning and Sequences Analysis of M Locus Protein Kinase Gene from Brassica oleracea

ZHAO Yong-Bin;ZHU Li-Quan and WANG Xiao-Jia

Acta Agron Sin. 2006, 32(01):  46-50. 

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The DNA and cDNA fragments of M locus encoding protein kinase were initially amplified from genomic DNA and stigma cDNA in Brassica oleracea by using PCR , RT-PCR and other molecular methods. Their lengths were 1 615 bp and 1 294 bp respectively. For the first time, sequence analysis indicated that there was 98% identity of MLPK cDNA between Brassica oleracea and Brassica rapa. In Brassica oleracea, the MLPK gene contained four introns, which were three introns less than those in Brassica rapa. Moreover, in two ends of introns of MLPK gene from Brassica oleracea, there were new base sequences which didn’t comply with typical GU-AG rule: TA and CG existed in the 5′ end of the third and the fourth intron of MLPK gene; CAGG and GT were found respectively in the 3’ end of the sequences. So we speculated that these new base sequences may have relation to a new splice process. These results provided some new insight into the molecular mechanism of self-incompatibility in Brassica oleracea.

Maximum Likelihood Method for Mapping QTL in Four-way Cross Design

AO Yan and XU Chen-Wu

Acta Agron Sin. 2006, 32(01):  51-56. 

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In recent years, there has been a great deal of interests in the development of methodology to map quantitative trait loci (QTLs) relative to known marker map in population derived from inbred line crosses. However, mapping populations that can be handled by most of developed methods must be derived from the cross of two inbred lines. The drawback of these designs is that the statistical inference space is quite narrow and thus results from one cross cannot be generalized to other crosses derived from different inbred lines. Xu first proposed the four-way cross design of QTL mapping intended to increase the statistical inference space and the opportunity for detecting more QTL. Four-way cross design is a mating design that is derived from the cross of four inbred lines. Although iteratively reweighted least squares (IRWLS) method for mapping QTL in four-way cross design has been proposed, low efficiency of this method was predicted due to neglecting the mixture distribution of QTL genotypes within flanking marker genotypes. In this paper, based on the quantitative genetic model of four-way cross design and the mixture distribution theory, a new method of QTL mapping for four-way cross design was proposed. At first, the conditional probability of QTL genotype at a putative QTL position on chromosome was calculated jointly by using all of marker genotypes on this chromosome; and then a maximum likelihood method implemented via EM algorithm was proposed. The effects of the power of detection, accuracy and precision of QTL mapping in different QTL heritabilities, sample size and molecular marker polymorphism information contents on the proposed method were studied based on simulated data. The results showed: (1) In the power of QTL detection, four-way cross with incomplete genotypic information of DNA molecular markers is slightly lower than that complete marker information. (2) The accuracy and precision of estimates of QTL position and effects will be enhanced as the increasing of QTL heritability, sample size and polymorphism information content of molecular marker.

Estimation of Regional Cotton-Rice and Rice-Cotton Rotation Periods Based on Satellite Remote Sensing Methodology

ZHU Ze-Sheng and SUN Ling

Acta Agron Sin. 2006, 32(01):  57-63. 

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The objective of this paper was to estimate rotation periods of cotton-rice and rice-cotton from 2001 to 2004 in forty-two towns of XinHua City of JiangSu province of China, belonging to Lixiahe agriculture region, using satellite-based remote sensing (RS) data and geographic information system (GIS) tools. The vegetation in this region comprises mainly rice, cotton, soybean, sweet potato and vegetables. On an average from 2001 to 2004, the cotton land made up 12 488 ha/year, while the rice land area 83812 ha/year, i.e. 9.61% and 64.47% of total arable land area of XinHua City respectively. On the basis of data availability and accuracy requirements, four Landsat Thematic Mapper (TM) satellite images dated on 26/07/2001, 29/07/2002, 24/07/2003 and 26/07/2004 were selected as the data sources for the interpretation of rice and cotton. The satellite data were geographically registered onto the map. By using the knowledge about the temporal growth pattern of various crop types in this region, based on our field observations of various land cover classes, a supervised classification approach was followed to classify the scene into various land cover classes. The rice and cotton of vegetation in the images were classified by using the classification approach. The GIS was then used to integrate large amounts of interpreted image data and other related geographic details about the region to analyze the changes of land covers from cotton to rice or vice versa by the spatial polygon analysis model. The phenomenon of cotton-rice and rice-cotton rotation was found from the interpreted images. The rotation periods of cotton-rice and rice-cotton periods were supposed to obey the stationary stochastic process. The first and second models were built for estimation of cotton-rice and rice-cotton periods of each town, which was derived by cotton and rice coverage data provided by GIS that processed the interpreted images. The third model was built for computing the arithmetic average value of cotton-rice and rice-cotton rotation periods. The data provided by the models were used for analysis of cotton-rice and rice-cotton rotation periods of all the towns (Table 1 and Table 2). The results showed that the cotton-rice and rice-cotton were major rotation styles in this region. Among all the towns in XinHua City, there are obvious differences among the rotation levels or periods. The three average rotation periods of cotton-rice of all the towns from 2001 to 2004 were respectively 2.01, 3.42 and 3.01 years with an average of 2.81 year. The three average rotation periods of rice-cotton of all the towns from 2001 to 2004 were respectively 2.61, 2.70 and 3.35 years with an average of 2.89 year. The difference between the average values was very small or about 2.85%, indicating clearly that the result obeys the basic law that the cotton-rice rotation period should be statistically equal to the rice-cotton one, the models or formulas for estimation of the rotation periods are reasonable. The average rotation period of cotton-rice and rice-cotton rotation of all the towns was 2.85 year. The interpretation precision of remote sensing images arrived at the experimental requirement by validation from observations on the ground. In comparison with the traditional conclusion of 2–5 year in the past more than 400 years, the rotation period of 2.85 year given in the study is more scientific and precision.

Molecular Marker-assisted Selection for Improving Cooking and Eating Quality in Teqing and Its Hybrid Rice

LIU Qiao-Quan;CAI Xiu-Ling;LI Qian-Feng;TANG Shu-Zhu;GONG Zhi-Yun;YU Heng-Xiu;YAN Chang-Jie;WANG Zong-Yang and GU Ming-Hong

Acta Agron Sin. 2006, 32(01):  64-69. 

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“Teqing”, both an elite conventional cultivar with high yields and a male parent for two-line indica hybrid rice production, had a great contribution to rice production at the end of last century in China. However, the amylose content (AC) in the endosperm of Teqing seeds is high, resulting in poor cooking and eating quality of the milled rice. The amylose in rice endosperm is synthesized by the granule-bound starch synthase (GBSS), which is encoded by the waxy (Wx) gene. Our previous researches showed that AC was correlated with the ability of excising intron 1 from the leader sequence of the Wx transcript, and a single nucleotide polymorphism (G or T) located at the first nucleotide of splice donor site of Wx intron 1 might be the key factor responding for the alterative splicing. Thus, a CAPS (Cleaved amplified polymorphic sequence) molecular marker, named as PCR-AccI, was subsequently developed to identify whether the nucleotide in this site is G or T, which preferred to easily infer the AC in a genetic or breeding material (Fig.1). In this study, by using the developed molecular marker and its assisted selection, the AC in Teqing was successfully down-regulated for improving its cooking and eating quality by introgressing the Wx locus from an indica rice line (Wx-TT genotype) with intermediate AC and good quality. Three elite improved Teqing lines, Teqing-TT-1, Teqing-TT-2 and Teqing-TT-3, were selected after four backcrosses and two selfinges (Table 1); in each generation the molecular marker-assisted selection was applied to select the individuals carrying Wx locus with GT or TT genotype (Fig.1). In the selected lines, the AC in endosperm was reduced to a relative low level of about 15% from 28.5% of their original (Table 3). Consequently, the two-line hybrids derived from the selected lines and Pei’ai 64S also showed a reduced amylose level (Table 3). The northern blot analysis showed that the reduction of amylose synthesis in selected lines and their hybrids resulted from the lower expression of the introduced Wx gene compared with in the originals (Fig.2). In the field trials, the agronomic performance in the improved lines and their hybrids was examined to be comparable as the originals except for a negative impact on grain weight (Table 1 and Table 2). Simultaneously, the other key factor involved in rice cooking and eating quality, gel consistency (GC), was also improved by the effect of reduced AC in the selected lines and their hybrids (Table 3), but the gelatinization temperature (GT) showed a little increase in the selected lines by comparison with the original one. The selected Teqing lines would have a great potential for the production of both conventional and hybrid indica rice with high quality and yielding.

Stomatal Characteristics of Different Green Organs in Wheat under Different Irrigation Regimes

ZHANG Yong-Ping; WANG Zhi-Min; WU Yong-Cheng and ZHANG Xia

Acta Agron Sin. 2006, 32(01):  70-75. 

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Stomata are the channel of CO₂ and water vapour exchange between the plant and atmosphere, and contributing to photosynthesis, transpiration and temperature fitness of plant. There have been many reports about the stomatal structure and characteristics focused on the leaf blades, the major photosynthetic organs, in wheat but only a few reports about stomatal distribution on the ear（especially on the awn）, whereas, no any report on stomatal structure characteristics and their relations to photosynthetic rate and transpiration rate of various non-leaf green organs in wheat under different water condition. In current study, a field experiment was conducted with two cultivars (Lumai 21 and SJZ 8) and three irrigation treatments[No irrigation, Two irrigations (1 500 m³&#8729;hm^-2) and Four irrigations (3 000 m³&#8729;hm^-2) in the growing period of wheat], in order to asses differences in stomatal structure characteristics and their response to irrigation between flag leaf blade and non-leaf green organs (flag leaf sheath, peduncle, glume, lemma, palea and awn). Stomatal structure and distribution on leaf blade and non-leaf green organs in winter wheat were observed, and the stomatal conductance, transpiration rate and photosynthetic rate were also measured in response to different supplemental irrigation treatments. It was showed that under different irrigation treatments, stomata could be found on all surfaces of flag leaf blade , sheath and peduncle, and also on the surface of awn and abaxial surface of glume in ear. However, for lemma, stomata appeared only on the adaxial (not on the abaxial )side under both two and four irrigation treatments, and only on the abaxial side under water stress(no irrigation). In size, stomat apparatus on the ear（glume, lemma, palea and awn）was smaller than that on other organs. With the decrease of water supply, the width of stomatal aperture was also decreased, while both stomat frequency and stomatal aperture length of various organs were increased. Compared with flag leaf blade, non-leaf green organs (flag leaf sheath, peduncle and ear) was less sensitive to supplemental irrigation, and showed higher stability in stomatal conductance, transpiration rate and photosynthetic rate during the later filling period. There was a positive correlation between stomatal conductance and transpiration rate in various organs, while the coefficient of correlation in non-leaf green organs was lower than that in leaf blade. The results suggested that with the decrease of water supply, transpiration rates were declined for both the leaf blades and non-leaf green organs, then, photosynthetic rates might be remarkably decreased in leaf blades, however, relatively stable in non-leaf green organs, which may lead to higher water use efficiency (WUE) in non-leaf green organs than in leaf blades.

Identification for Cold Tolerance at Different Growth Stages in Rice (Oryza sativa L.) and Physiological Mechanism of Differential Cold Tolerance

LI Xia; DAI Chuan-Chao; CHEN Yu; CHEN Ting and JIAO De-Mao

Acta Agron Sin. 2006, 32(01):  76-83. 

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To elucidate the physiological mechanism of differential cold tolerance in rice, japonica rice cultivars 9516, H45, WuyuJing, PEPC transgenic rice, Kitaake, Su huxiangjing; indica rice cultivars Yangdao 6, Xiangxian, IR64, Peiai64S and hybrid rice cultivars Yueyou 938, Shanyou63, X07S/Zihui 100, Liangyou Peijiu, 14 rice cultivars were appraised for cold tolerance at early seedling stage, seedling stage( 3 blade) and booting stage, respectively(Table 1). At the same time, the identification of cold tolerance in rice in natural chilling condition was conducted in Nanjing(Fig.1). Results showed that the method for identifying cold tolerant rice cultivars at bud stage, seedling stage and booting stage is feasible and bud livability, seedling mortality and seed-setting rate of rice are reliable indexes for cold tolerance identification which are correlated with some physiological parameters in different rice cultivars under chilling treatment. Furthermore, photosynthetic rate(Fig.3), PSⅡ photochemical efficiency(F_v/F_m)(Fig.4), the composition of fatty acid(Table 2), the changes of active oxygen index(MDA, H₂O₂ and O₂^．- ) and anti-photooxidative substance(ascorbate and glutathione) (Table 3) of cultivars with a different tolerance to chilling were studies before and after chilling treatment. The results showed that photosynthetic rate and PSⅡ photochemical efficiency(F_v/F_m) in leaves of tolerant cultivar Wuyujing were kept stable, while those in the sensitive one, Xiangxian, decreased more and in the middle one, Shanyou 63, kept in a middle range. And the index of unsaturated fatty acid was higher in tolerant cultivars, while the recycle of ascorbate and glutathione in leaves, particularly the turnover of glutathione in leaves in the middle tolerant cultivar Shanyou63 activated highly as compared with the sensitive one, Xiangxian. It is indicated that the cold tolerance rice cultivars keep higher index of unsaturated fatty acid and capacity for turnover of glutathione, which exhibited stable photosynthetic rate and primary PSⅡ photochemical efficiency(F_v/F_m) in leaves after chilling treatment.

Ultrastructural Localization of Cellulase Acitvity in Lytic Root Cortical Cells during Aerenchyma Formation of Flooded Maize

WEI He-Ping;LI Rong-Qian;WANG Jian-Bo;WU Gan-Lin and WU Yan

Acta Agron Sin. 2006, 32(01):  84-87. 

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Cellulase activity in adventitious roots of maize during aerenchyma formation induced by flooding was located through the reaction of Benedict’s reagent with reducing sugars liberated by hydrolysis of carboxymethylcellulose (CMC). The electron-dense deposits, indicating the presence of cellulase activity, were firstly observed in a few cortical cells 4 mm behind root tips. In the root zones 4 to 10 mm behind tips, the cortical cells containing deposits gradually increased in number, and the deposits located in these cells showed remarkably increased in density. Meanwhile, the deposits also altered significantly in pattern of distribution. At the earlier stage, the deposits were mainly located along the cell wall, and across the cell wall at the later stage. With the complete degeneration of some cortical cells, aerenchyma was formed in the cortex 11 mm behind tips. The present results support the hypothesis that an enhanced cellulase activity is involved in the lysis of cortical cells leading to aerenchyma formation under a waterlogged condition.

Development of a Series of Single Segment Substitution Lines in Indica Background of Rice (Oryza sativa L.)

ZENG Rui-Zhen;SHI Jun-Qiong;HUANG Chao-Feng;ZHANG Ze-Min;DING Xiao-Hua;LI Wen-Tao and ZHANG Gui-Quan

Acta Agron Sin. 2006, 32(01):  88-95. 

Abstract ( 2040 )   PDF (545KB) ( 988 )   Save

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Single segment substitution line (SSSL) is a power tool for mapping, cloning and functional analysis of genes. In this study, A SSSL population was developed using a Indica cultivar “Huajingxian 74” as recipient and 12 accessions including 8 Indica and 4 Japonica as donors (Table 1 and Fig.1). Five hundreds and forty-nine SSR markers with an average marker interval about 2.8 cM on the rice microsatellite map were used to survey the polymorphism between parents. The polymorphisms between the 12 donors and the recipient were varied from 33.0% to 70.7% with an average of 50.0% (Table 2). By backcrossing four or five times, a series of candidate SSSLs were selected. The genetic backgroud in the candidate SSSLs was examined in BC₄F₁, BC₄F₂, BC₅F₁ or BC₅F₂. The samples with residual segments from the candidate SSSLs were 1.07% (Table 3). Discarding the candidate SSSLs with residual segments, a total of 260 SSSLs were developed, of which 74 SSSLs were selected from BC₄F₂, 134 SSSLs from BC₄F₃ and other 52 from BC₅F₂ (Table 4). Each SSSL contained a single defined homozygous chromosome substituted segment from one of the twelve donors in the Huajingxian 74 genetic background. The estimated lengths of the substituted segments ranged from 0.2 cM to 109.9 cM with an average of 19.9 cM (Fig.2 and Table 4). Total length of the substituted segments in the SSSL population was 5166.0 cM, which was about 3.4 times of the rice genome. The substituted segments in the SSSLs were distributed on 12 chromosomes (Fig.3 and Table 5) and provided a coverage of 83.8% of the rice genome (Table 4). These SSSLs will play an important role in the study of functional genomics and molecular breeding in rice.

Effects of Low Temperature during Grain Filling on the Structure of Endosperm in Hybrid Rice

YUAN Li-Min;CHANG Er-Hua;XU Wei;WANG Zhi-Qin and YANG Jian-Chang

Acta Agron Sin. 2006, 32(01):  96-102. 

Abstract ( 1649 )   PDF (3626KB) ( 1146 )   Save

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The structure of endosperm is closely related with the grain quality of rice and is believed to be mediated by environmental conditions. The objectives of this study were to investigate the structure of rice endosperm and the grain quality by a scanning electron microscope. Using four hybrid rice combinations, Liangyoupeijiu, 103S/Zhengjing 2, Fengyouxiangzhan and Shanyou 63, grown in pot and treated with low temperature at 18℃ during 0–10 days(T₁), 11–20 days(T₂), and 21–30 days(T₃) after flowering respectively，and the control temperature 24–27℃. The results showed that the grain was abnormal in exterior shape, the area of chalkiness increased, and the size of the amyloplast, either complex or single, decreased, the difference in the size between complex and single amyloplast increased, their arrangements loosened, and resulted in more complex and fewer single amyloplast by the low temperature treatments. The earlier the low temperature treatment was, the more serious the effect was on the endosperm structure. If plants were subjected to low temperature at early grain filling stage and then grown under a normal temperature at late stages, effects of the low temperature on the grain shape, structure of endosperm and the chalkiness area for inferior grains were serious, whereas those for superior grains were not obvious. The results suggest that the structure of endosperm is deteriorated by low temperature during the grain filling period, leading to poor grain quality of rice.

Difference in Chalky Characters of the Grains at Different Positions within a Rice Panicle

DONG Ming-Hui; SANG Da-Zhi; WANG Peng; ZHANG Wen-Jie and YANG Jian-Chang

Acta Agron Sin. 2006, 32(01):  103-111. 

Abstract ( 1985 )   PDF (567KB) ( 1149 )   Save

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Chalkiness of the grain is one of the most important quality indexes of rice，affecting badly the milling，apparent，cooking and taste qualities of rice. In order to study and document the reasons and influencing factors，much researches，such as physical and chemical properties，cellular features of chalkiness formation as well as the factors influencing chalkiness formation including source-sink relation and grain-filling characteristics，have been done recently，the difference between dynamic changes of chalkiness formation in vigorous and weak grains during filling stage and the differences in the chalk degree of the grains in various parts in a same panicle were also preliminarily studied. Thus，the endosperm starch structure characteristics such as starch grain shape, size, developing degree and arrange pattern in chalky milled grains，the relations between chalkiness formation and dynamic variations of grain filling such as dry matter accumulation in grain，filling velocity and dehydrating velocity during filling stage were preliminarily investigated. In addition，correlative researches also indicate that it is remarkable differences in the chalk degree of the grains in various parts in a same panicle and the chalk degree of the vigorous grains are usually smaller than that of the weak grains.
The objective of this study was investigate the distribution of chalkiness degree (CD) and chalky grain percentage (CGP) for different grains on a panicle in two rice cultivars Yangdao 6 (indica rice) and Wuyujing 3 (japonica rice) in the yield, three levels of nitrogen, 0, 120 kg/ha, and 240 kg/ha, were applied at pre-planting and topdressing. All primary branches on a panicle were evenly divided into three parts of the upper, middle and basal. The grains were numbered as 1 to 6 on a primary branch and 1 to 3 or 4 on a secondary branch from the top to base. Generally, CD and CGP for the grains on a secondary branch were greater than those on a primary branch at the same part of a panicle. The grain 6 showed the greatest CD and the grain 1 the least on a primary branch. On a secondary branch, the grain 1 had the greatest CD and the grain 3 or 4 the least. CGP on the branches at the upper parts of a panicle exhibited the greatest, at the middle part the middle, and at the basal part the least. CGP was the greatest for the grain 2 and the least for the grain 1 or 6 on a primary branch, and the grain 1 on a secondary branch. Application of fertilizer-nitrogen reduced CD and CGP when amount of nitrogen was between 0 and 240 kg/ha.

Effect of Dry-Cultivation Patterns on the Yield and Quality of Rice

XU Guo-Wei; WANG Peng; TANG Cheng; WANG Zhi-Qin; LIU Li-Jun; YANG Jian-Chang

Acta Agron Sin. 2006, 32(01):  112-117. 

Abstract ( 1789 )   PDF (411KB) ( 983 )   Save

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Rice dry-cultivation is a new technology in paddy rice production. An indica hybrid rice combination, Shanyou 63, was used to investigate the grain yield and quality of rice cultivated with different methods. Three treatments, dry-cultivation mulched with straw (DCMS, the field covered with rice straw before transplanting and not flooded), dry-cultivation mulched with film (DCMF, the field covered with plastic film before transplanting and not flooded), and moist-cultivation (MC, the field kept flooded, control), were established. Grain yield and its components, grain quality, starch profile characters, root dry weight and activity were determined. The results showed that there was no significant difference in the grain yield between DCMS and MC, but the grain yield of DCMS was significantly higher than that of DCMF. Under dry-cultivation, the panicles per square meter were significantly increased, but spikelets per panicle, grain setting percentage and 1 000-grain weight were decreased. More effective panicles by DCMS were produced than by DCMF, which attributed to higher grain yield for the former than the latter. The differences in the milling quality, appearance quality, and cooking and nutrient quality of rice were not significant between DCMS and MC, indicating that DCMS has no bad effect on the grain quality. Grains from DCMF had higher chalkiness, smaller gel consistency and alkali spreading value, when compared with those from MC. Peak viscosity and breakdown value were decreased and setback value of the starch profile of rice endosperm were increased by dry-cultivation, specially by DCMF, suggesting that the eating quality of the rice grown under DCMS is better than that under DCMF. Dry matter accumulation of shoot was reduced, but root dry weight, remobilization of assimilates from stems to grains and harvest index were increased by both DCMS and DCMF. Root activities under both DCMS and DCMF were higher than those under MC at heading and early grain filling stage, but decreased faster during the mid and late grain filling period. In comparison, DCMS exhibited a slower decrease in root activity and leaf senescence than DCMF. The results suggest that the grain yield and quality of rice under DCMS are better than those under DCMF, and all the dry-cultivation of rice do not produce low grain yield and poor rice quality. Reasons for the differences in the formation of grain yield and quality between DCMS and DCMF were discussed in the paper.

Effect of Free-air CO₂ Enrichment on Root Activity of Japonica Rice (Oryza sativa L.) Cultivar Wuxiangjing 14

YANG Hong-Jian; YANG Lian-Xin; LIU Hong-Jiang; HUANG Jian-Ye; DONG Gui-Chun; ZHU Jian-Guo; WANG Yu-Long

Acta Agron Sin. 2006, 32(01):  118-124. 

Abstract ( 1732 )   PDF (519KB) ( 1109 )   Save

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A free-air CO₂ enrichment experiment was conducted at Anzhen city, Wuxi，Jiangsu, China, to study the effect of free-air CO₂ enrichment [FACE, 200 μmol·mol^-1 higher than Ambient(AMB)] on root growth dynamics, using the Japonica cultivar Wuxiangjing 14. Results showed that：(1) The peak value of total absorption area per unit dry weight of root and active absorption area per unit dry weight of root under FACE reached 10 days earlier than those at ambient air; and FACE treatment significantly decreased the total absorption area per unit dry weight of root, active absorption area per unit dry weight of root and the amount of a-NA per unit dry weight of root at 18 days after transplanting and its followed different stages, while little effects of FACE were detected on root activity per hole.(2)Root activity per unit dry weight of root negatively correlated with the number of adventitious roots per hole, total length of adventitious roots per hole, roots volume and dry weight of root per hole at 28 days after transplanting and its followed different stages. The larger the root production, the lower the root activity per unit dry weight. (3) For the most part，root activity per unit dry weight of root positively correlated with N content of rice plant, and negatively correlated with C/N ratio. According to available study results, the authors speculated that the largeness of biomass accumulated at early growth stages, lower N content in rice plant and higher C/N ratio appear to be the primary causes of significant decrement of root activity per unit dry weight of root under FACE condition.

Intercropping of Different Silage Maize Cultivars and Alfalfa

LIU Jing-Hui; ZENG Zhao-Hai; JIAO Li-Xin; HU Yue-Gao; WANG Ying; LI Hai

Acta Agron Sin. 2006, 32(01):  125-137. 

Abstract ( 2053 )   PDF (417KB) ( 1402 )   Save

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Intercropping has been studied and practiced widely for crop production, but it has seldom studied in the forage production. In this paper, intercropping system of different silage maize cultivars and alfalfa was studied in regard to physiological ecology of the system, yield and quality of products. Results showed that magrginal utility of silage maize was remarkable, and it changed with silage maize cultivars and growth stage. As compared with monocropping of silage maize, at male tatrad, light intensity and light transmission of intercropping silage maize was increased by 15.3%－88.1% and 15.1%－89.0% respectively at bottom of plants population, and 52.1%－74.1% and 51.2%－73.0% at middle layer of plant population; average light transmission for whole growth stage was increased by 49.5%－62.1% at bottom, and 40.7%－56.6% for middle part; average temperature of five centimeters soil layer at whole growth stage increased by 1.0%－1.8%. At the harvest period, plant height, stalk thickness and green leaf area of cultivars Keduo 4, Keduo 8, Keqing 1 in intercropping system were 2.3%－20.9%,0.4%－7.6% and 2.2%－19.6% greater than those for monocropping. Crude protein and crude fat contents in plant intercropping system were increased by 30.8%－59.1% and 99.4%－137.5% respectively compared with those for monocropping maize. The yields of green forage and hey for intercropping system were decreased by 22.7%－32.3% and 17.6%－28.2% as compared with monocropping maize, and increased by 156.7%－202.4% and 176.5%－197.5% as compared with monocropping alfalfa. Crude protein and crude fat contents, green forage and hey yields of alfalfa in intercropping system were slightly decreased at early flowering stage, but there were not significant difference between two cropping systems. Integrated analysis indicates that intercropping system can take advantage of light, temperature resources of local fields sufficiently. In addition, alfalfa is perennial legume, which can cover the fields, fix and fertilize soil, therefore protect soil from wind erosion. The harvest of alfalfa from May to June next year not only solves the problem of forage shortage for livestock husbandry in Inner Mongolia but also provide bigger space for the growth of intercropping silage maize.

Effects of Water Stress of Soil on Rice Yield and Quality

WANG Cheng-Ai; WANG Bo-Lun; ZHANG Wen-Xiang; ZHAO Lei; ZHAO Xiu-Zhe; GAO Lian-Wen

Acta Agron Sin. 2006, 32(01):  131-137. 

Abstract ( 1903 )   PDF (488KB) ( 1151 )   Save

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With Nongda 3 as a material, the effects of soil water stress (soil water potential) on the development, grain yield and quality of rice plants grown in the pots by manual rigorously controlling soil potential with tension-meter were studied. The results indicated that the yield and quality were affected in different degree when the soil water potential (SWP) was reduced to －75 kPa during the different growing period. The lengths of three leaves from the top, grains per panicle, biomass and grain yield of the plant, rate of brown rice, length/width of the kernel, and taste for eating were decreased by the water stress at middle booting stage. The panicle number, biomass and grain yield of the plant were reduced by soil water stress at the beginning of tillering period. The leaf turned to shrink and yellow，and leaf area index declined because of soil water stress after heading. Meanwhile, the percentage of ripened grain, 1 000-grain weight and head rice rate were decreased by soil water stress at the milk and filling stages, the percentage of chalky kernel and chalkiness were increased at the filling stage, and the chlorophyll content, gel consistency and protein content were declined at the wax period.

REVIEW

Induction and Improvement of Cytoplasmic Male Sterility in Oilseed Brassica by Somatic Hybridization

HU Qiong and LI Yun-Chang

Acta Agron Sin. 2006, 32(01):  138-143. 

Abstract ( 1962 )   PDF (558KB) ( 1013 )   Save

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Cytoplasmic male sterility (CMS) has been widely used as an efficient pollination control system for oilseed rape hybrid production. The natural occurrence of CMS, however, has rarely been found in Brassica species，with Polima CMS as the only useful one for hybrid production. Hence the transfer and induction of new male sterile cytoplasm is very important for the application of heterosis in Brassica crops. Somatic hybridization as an approach for the transfer and induction of CMS is highly efficient because it bypasses sexual incompatibility and recombines the cytoplasmic genomes of two parental lines. It is reviewed in this paper that the transfer and induction of CMS trait within species or between species and genera by protoplast fusion methodology establish valuable CMS in agriculturally important species or varieties of oilseed Brassica. The perspective of somatic hybridization and the potential of the established novel CMS systems for oilseed rape hybrid improvement are also discussed.

RESEARCH NOTES

Cross-compatibility between Maize and Maize Relatives

TANG Qi-Lin;YANG Ke-Cheng;ZHENG Zu-Ping and RONG Ting-Zhao

Acta Agron Sin. 2006, 32(01):  144-146. 

Abstract ( 1799 )   PDF (243KB) ( 896 )   Save

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The cross-compatibility (seed set and pollen viability) between maize (inbred and hybrid) and it relatives (including annual and perennis) as well as its introgression hybridization progenies were investigated. The results shown that maize relatives of genus Zea can be directly crossed with maize, and grained F1 seeds. Maize relatives and their interspecies hybrids have strong heterosis photoperiod response. The cross-compatibility of their interspecies hybrid was affected remarkable by different female parent. Furthermore, For the introgression of desirable characters from maize relatives into maize, there are considerable genetic and breeding materials were achieved.

Effect of Chemical-sand Priming on Seed Vigor of Super Sweet Corn and Their Physiological Changes

ZHAO Guang-Wu; SUN Qun and WANG Jian-Hua

Acta Agron Sin. 2006, 32(01):  147-151. 

Abstract ( 2086 )   PDF (600KB) ( 1076 )   Save

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Effect of seed priming combined with chemical treatment on improving seed vigor of super sweet corn (Zea mays L. saccharata Sturt) was investigated. Results showed that seed vigor of super sweet corn “Green Superman” was significantly enhanced by all four methods. The electrolyte leakage of seeds treated by sand priming plus chemical was significantly decreased and the slowest electrolyte leakage was observed in the seeds treated by sand priming plus riboflavin. And the CAT and SOD activities of seedlings treated were significantly increased and their degradation was alleviated in low temperature stress. On this basis, further research was done on effect of sand priming plus riboflavin on seed vigor of other seven super sweet corns. Results suggested that their percentage of seedling emergence, speed of seedling emergence, membrane system integrality or SOD activity of different hybrids were significantly improved.

Effect of Silicon on the Growth of Test-tube Potato Plantlets and the Cell Wall Formation

FANG Jiang-Yu and MA Xue-Long

Acta Agronomica Sinica. 2006, 32(01):  152-154. 

Abstract ( 2018 )   PDF (475KB) ( 1097 )   Save

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During the investigation of the acceleration effect of silicon on the growth of potato, silicate acid was added to the medium of the plantlet cultured in the test-tube. The results showed that under the treatment of silicon, the shoots were taller and weighted more and roots more and longer. The better result came from 5 mmol/L silicate acid. The ratio of bound water to free water was increased, the chlorophyll content enhanced, the respiration rate decreased significantly, the cell wall extraction rate significantly increased, the cellulose content increased and the pectin separated with chelating agent decreased by the silicon treatment.

Effects of Stubble Height and Clipped Plant Height on Yield and Forage Quality of Euchlaena mexicana

WANG Yong-Jun;WANG Kong-Jun;DONG Shu-Ting;HU Chang-Hao;ZHANG Ji-Wang and LIU Peng

Acta Agron Sin. 2006, 32(01):  155-158. 

Abstract ( 1845 )   PDF (283KB) ( 926 )   Save

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A field experiment was carried out to study the effects of stubble height and clipped plant height on yield and forage quality of Euchlaena mexicana. The crude nutrient analysis method was used to evaluate the forage nutritive quality. The results showed that the yield of the treatment with 30 cm stubble (treatmentⅡ)was the highest as compared with those with 20 cm and 10 cm stubble. The fresh and dry matter yields of the treatment were 14.1 kg·m^-2 and 1.90 kg·m^-2, respectively. The contents of crude protein (CP) and crude fiber (CF) were higher and those of crude ashes (CA) and nitrogen-free extract (NFE) were lower when the stubble height was 30 cm. The yield of treatment Ⅳ (the plant was clipped at 130 cm height) and the control (the plant was clipped at 95cm height) was not significantly different, however, the content of CP and NFE was lower and CA and CF was higher in treatment Ⅳ than in control. The CP and NFE content of treatment Ⅲ (the plant was clipped at 60 cm height) was the highest and its CA and CF content was the lowest, while its yield was lower than that of control significantly. According to the yield of five forage nutritive indexes (CP, CA, EE, NFE and CF) and the gross energy (GE), the treatment with 30cm stubble and 95cm clipped plant height was the ideal cutting pattern for Euchlaena mexicana, providing higher yield and quality.