• 耕作栽培·生理生化 •

### 小麦幼苗从低光到强光适应过程中光合和抗氧化酶变化

1. 中国科学院遗传与发育生物学研究所植物细胞与染色体工程国家重点实验室，北京100101
• 收稿日期:2009-09-25 修回日期:2010-01-09 出版日期:2010-03-12 网络出版日期:2010-01-22
• 通讯作者: 李振声,E-mail:zsli@genetics.ac.cn,Tel:010-64889381
• 基金资助:

本研究由国家自然科学基金项目（30330390），国家重点基础研究计划（973计划）项目（2002CB111304，2009CB118506），中国科学院知识创新工程（KSCX1-YW-03，KSCX2-YW-N-046）和引进国际先进农业科学技术计划（948计划）项目（2006G2）资助。

### Variation in Photosynthetic Traits and Antioxidant Enzyme Activities of Wheat Seedlings Transferred from Low to High Light Growth Condition

LI Hong-Wei,LI Bin,ZHENG Qi,LI Zhen-Sheng*

1. State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
• Received:2009-09-25 Revised:2010-01-09 Published:2010-03-12 Published online:2010-01-22
• Contact: LI Zhen-Sheng,E-mail:zsli@genetics.ac.cn,Tel:010-64889381

Abstract:

When plants absorb excessive light energy, a large number of reactive oxygen species is generally produced resulting in the degradation of DNA, proteins, and pigments in plants. For wheat (Triticum aestivum L.) grown in North China, the photooxidation induced by high light (HL) during grain-filling period usually causes great losses in grain yield. It is important to understand the mechanism of wheat plant in response to HL for HL-tolerant breeding in wheat. Xiaoyan 54, a wheat cultivar with high resistance to HL, is an ideal material to disclose photosynthesis characteristics of wheat when exposed to HL. In this study, the third-leaf seedlings of Xiaoyan 54 were grown under the condition low light to HL in a growth chamber. The seedlings were sampled at 0, 1, 3, 8, 24, and 48 h of HL treatment. Simultaneously, the net photosynthetic rate (Pn), chlorophyll content (Chl), and fluorescence parameters were measured with the second leaf. The activities of antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR), were also determined. In addition, expression pattern of the pigment binding protein related genes were evaluated. The results showed that Pn increased in the photosynthetic induction stage that was from 0 h to 8 h of HL treatment, but decreased continuously during the photoinhibition stage that was from 8 h to 48 h of HL treatment. The maximum Pn value of 18 μmol CO2 m-2 s-1 was observed at the 8 h timepoint of HL treatment. The parameters Gs, Ci, and Tr changed similarly to Pn and reached the peaks at the 8 h timepoint of treatment. The contents of total chlorophyll and chlorophyll a only changed slightly during the 48 h of HL treatment. In contrast, chlorophyll b reduced significantly from 24 h to 48 h of treatment, and the ratio of chlorophyll a/b increased from 8 h to 48 h of HL treatment. At one hour of HL treatment, the maximum quantum efficiency of PSII (Fv/Fm), the maximum fluorescence (Fm), and variable fluorescence (Fv) were down-regulated significantly, when the heat dissipation was enhanced. The activities of SOD, CAT, APX, and GR were induced to higher levels with the highest value at 24 h timepoint of HL treatment. From 8 h to 48 h of HL treatment, the Talhcb genes, encoding LHCII subunits, were down-regulated at the RNA levels. At the early stage of HL treatment (0–3 h), TaELIP1 and TaELIP3 were induced, but repressed from 8 h to 48 h. As key enzymes in xanthophyll cycle, the transcripts of TaVDE and TaZEP responded differently to HL treatment. The expression of TaVDE decreased remarkably at 8 h of HL treatment and maintained a rather low level till 48 h. However, the expression of TaZEP showed an increase trend from 3 h to 24 h, and decreased at 48 h. In conclusion, when wheat seedlings exposed to continuous HL for 48 h, photooxidative stress occurred resulting in reductions of Pn, Fv/Fm, Chl b, and the expressions of pigment binding protein genes, but activation of the antioxidantenzymes.