关键词: 油菜, 小麦, 盐碱胁迫, Na⁺含量, 活性氧

Abstract:

Utilizing the crops which can produce economic benefits to improve the saline-alkali land is an important mean to expand potential resource of farming land in China. Different plants respond differently to saline-alkali stress and have different mechanisms of saline-alkali stress resistance. Identifying the physiological characteristics responding to salt and alkali stress of rapeseed and wheat, can provide theoretical foundations for using rapeseed and wheat as forage and enlarging the application potential of rapeseed and wheat in the improvement and utilization of saline-alkali land. In this study, saline-alkali soils from Jilin province were used for pot experiments; normal soils in Wuhan were used as CK and saline-alkali soils from Jilin with the final salt concentration of 0.2% and 0.4%, respectively, which were prepared in proportion to normal soils from Wuhan. One saline-alkali tolerant and one sensitive variety of rapeseed and wheat were selected, respectively, as research materials. We systematically compared the different salt-alkali tolerance mechanisms of rapeseed and wheat at the germination stage by measuring and analyzing growth indicators, osmotic regulation, ion balance, antioxidant enzymes, H₂O₂, $\mathrm{O}^{\bar{.}}_{2}$ and other indicators. The results showed that: (1) Under saline-alkali stress, in petiole, Na⁺ content was highest among petiole, leaf, stem and root, up to 88.40 mg g^-1. However, in wheat, Na⁺ concentration in root was the highest, up to 33.45 mg g^-1. Na⁺ accumulation in all parts of rapeseed was higher than that of wheat, and under the same treatment, especially, the Na⁺ accumulation in leaves was 2-8 times higher than that of wheat. (2) The decrease of K⁺ and the ratio of K⁺/Na⁺ of salt-tolerant rapeseed and wheat were higher than those of salt-sensitive varieties, while the rate of increase of Na⁺ concentration was lower than that of salt-sensitive varieties. The inhibition effect of Na⁺ depressing K⁺ uptake in the aboveground part of rapeseed is significant higher than those in the root, while it is opposite in wheat. (3) Under saline-alkali stress, the sugar content, antioxidant enzyme activity and $\mathrm{O}^{\bar{.}}_{2}$ scavenging ability in saline-alkali tolerant rapeseed and wheat were higher than those in the sensitive varieties. The content of H₂O₂ and $\mathrm{O}^{\bar{.}}_{2}$ increased by the increasing of salt concentration in the soil, while the tolerant variety showed a smaller increase than the sensitive one. The saline-alkali-tolerant rapeseed variety respond faster to the saline-alkali stress at the seedling stage, and the SOD, POD, and CAT activities in leaves and petioles can respond rapidly and increase gradually. While in the leaves of salt-tolerant wheat, the SOD and POD variety were the main antioxidant enzymes at the tillering stage, but POD and CAT in the leaves at the jointing stage were the main antioxidant enzymes, and with the advancement of the growth stage, the soluble sugar of the leaves and the scavenging ability of $\mathrm{O}^{\bar{.}}_{2}$ were significantly reduced. Rapeseed mainly distributed Na⁺ into petioles and stems through “sodium storage”, but wheat mainly reduced Na⁺ absorption through “sodium rejection” and accumulated more Na⁺ in the root system. And varieties with strong saline-alkali tolerance had better ability to maintain sodium and potassium ion homeostasis. Furthermore, the salt-alkali tolerance of rapeseed increased gradually with the advancement of growth period, while the salt-alkali tolerance of wheat decreased gradually with the advancement of growth period.

Key words: rapeseed, wheat, saline-alkali stress, Na⁺ content, ROS