Effects Of Low Temperature Stress On Physiological And Biochemical Characters Of Different Wheat Genotype

The experiments were conducted at Dayangdian test base of Anhui Agricultural Uniwersity in2011-2013. The effects of low temperature stress on cell structure of leaf and tillering node, photosynthetic performance of leaf, endogenous protective enzyme system and endogenous hormones of leaf and root were studied among different wheat genotypes (spring wheat cultivars:yangmai18and huaimai30, semi-spring wheat cultivar:zhengmai9023, and semi-winter wheat cultivar:yannong19) at tillering and elongation stages. The main results were as follows:1. Effects of low temperature stress on penultimate cell structure of different wheat genotypes at tillering and elongation stagesThe mesophyll cells of three wheat genotypes after the seedlings were exposed to low temperature stress at tillering and elongation stages were different dgree of contraction, and intercellular space of them increased. At tillering stage, the arrangement of the mesophyll cells of spring wheat cultivar (huaimai30) and semi-spring cultivar (zhengmai9023) were more irregular than semi-winter wheat cultivar (yannong19), while the vessel and sieve tube of huaimai30tillering node ruptured after low temperature stress. At elongation stage, the dgree of cell contraction of spring wheat cultivar (huaimai30) was more obvious than that of other cultivars.2. Effects of low temperature stress on photosynthetic performance of different wheat genotypes at tillering and elongation stagesTthe photosynthetic parameters which contained net photosynthetic rate (Pn), stomata conductance (Gs) and intercellular CO2concentratio (Ci), and chlorophyll fluorescence parameters which contained minimal fluorescence (Fo), maximum quantum yield of PSII (Fv/Fm), photochemical quenching (qp), non-photochemical quenching coefficient (NPQ) and acyclic photosynthetic electron transfer rate of PSII (ETR) were all significant differences among three wheat genotypes after the seedlings were exposed to low temperature stress at tillering and elongation stages. Results showed that Pn, Gs, Fv/Fm, qp, NPQ and ETR of yangmai18and huaimai30were low, but C{and Fo were high, while Pn, Gs, FJFm, q?, NPQ and ETR of yannong19were high, but Ci and Fo were low. Namely, photosynthetic performance of semi-winter wheat cultivar (yannong19) affected by low temperature stress was minimized, followed by semi-spring cultivar (zhengmai9023) and spring wheat cultivar (yangmai18and huaimai30).3. Effects of low temperature stress on endogenous protective enzyme system and endogenous hormones of different wheat genotypes leaf at tillering and elongation stagesThe superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) activity and MDA content of leaf were all significant differences among three wheat genotypes after the seedlings were exposed to low temperature stress at tilleringand elongation stages. SOD, POD and CAT activity of yangmai18and huaimai30decreased, while MDA content of them increased. SOD, POD and CAT activity of zhengmai9023and yannong19increased, while MDA content of them decreased. The increase range of SOD, POD and CAT activity of yannong19was higher than zhengmai9023, while the decrease range of MDA content of yangnong19was higher than zhengmai9023.The abscisic acid (ABA), auxin (IAA) and gibberellin (GA3) content of leaf were all significant differences among three wheat genotypes after the seedlings were exposed to low temperature stress at tillering stage. ABA content increased, while the increase range of ABA content of yannong19was highest, followed by zhengmai9023and huaimai30. IAA content of huaimai30decreased. The increase range of IAA content of yannong19was higher than zhengmai9023. The decrease range of GA3content of huaimai30was higher than zhengmai9023, whlie GA3content of yannong19increased. ABA, IAA and GA3content of leaf were all significant differences among three wheat genotypes after exposure to low temperature stress at stem elongation stage. The decrease range of ABA content of huaimai30was higher than zhengmai9023, while ABA content of yannong19increased. The decrease range of IAA content of zhengmai9023was higher than huaimai30, while IAA content of yannong19increased. The decrease range of GA3content of huaimai30was higher than zhengmai9023, while GA3content of yannong19increased.4. Effects of low temperature stress on endogenous protective enzyme system and endogenous hormones of different wheat genotypes root at tillering and elongation stagesSOD, POD, CAT activity and MDA content of root were all significant differences among three wheat genotypes after the seedlings were exposed to low temperature stress at tilleringand elongation stages. SOD and CAT activity of yangmai18and huaimai30decreased, while POD activity and MDA content of them increased. SOD, POD and CAT activity of zhengmai9023and yannong19increased, while MDA content of them decreased. The increase range of SOD and CAT activity of yannong19was higher than zhengmai9023, whlie the decrease range of MDA content of yangnong19was higher than zhengmai9023. The increase range of POD activity of yannong19was highest, followed by zhengmai9023, and yangmai18and huaimai30.ABA, IAA and GA3content of root were all significant differences among three wheat genotypes after the seedlings were exposed to low temperature stress at tillering stage. ABA content decreased, but ABA content of yannong19was higher than that of other cultivars. IAA content of huaimai30decreased. The increase range of IAA content of yannong19was higher than zhengmai9023. GA3content increased, and the increase range of GA3content of yangnong19was highest, followed by zhengmai9023and huaimai30. ABA, IAA and GA3content of root were all significant differences among three wheat genotypes after exposure to low temperature stress at stem elongation stage. ABA content of huaimai30decreased. The increase range of ABA content of yannong19was higher than zhengmai9023. The decrease range of IAA content of huaimai30was higher than zhengmai9023, whlie IAA content of yannong19increased. GA3content increased, and the increase range of GA3content of yangnong19was highest, followed by huaimai30and zhengmai9023.