Effect Of Drought Stress On Physiological And Microstructure In Soybean Seedlings

This test used the breed variety Heinong No. 48 as test material. This work was carried out in the gardening experimental center's greenhouses of NEAU in 2008, we had three different treatments: normal water supply(80%-85% of field capacity), mild drought (65%-70% of the field capacity) and moderate drought (50%-55% of field capacity). We treated soybean seedings under drought stress, then discussed the effects on morphological characters , physiological indexes and microstructures of soybean seedlings by combining biochemical measurement and structural analysis. The results showed that:1. Under mild and moderate drought stress,growth was depressed and differences were extremely significant between three treatments. While the root-shoot ratio increased, differences were extremely significant when we compared with three treatments. And the leaf relative water content of soybean seedlings decreased, the leaf relative water content differences were significant when we compared with three treatments.2.Under mild and moderate drought stress, proline content, soluble sugar content and malondialdehyde content all showed a tendency to increasing ,while the chlorophyll content and soluble protein content of soybean seedlings got lower and lower. Under mild and moderate drought stress, proline content showed differences were extremely significant when it was the third, fifth and seventh days compared with the control. Soluble sugar content differences were extremely significant under moderate stress compared with the other two treatments. Under mild stress chlorophyll content differences were extremely significant compared with the other two treatments. Under mild and moderate stress, soluble protein level differences were extremely significant compared with the control at later stage of stress.3.The drought stress enhanced the the activity of superoxide dismutase in soybean seedlings leaves ,the drought stress deepen the activity enhanced.And the activity of peroxidase enhanced first decreased with the passage of time .The activity of catalase increased. Soybean tender seedling leaf blade SOD activity showed differences were extremely significant every treatment day under mild and moderate drought stress compared with the control. Soybean tender seedling leaf blade POD activity differences were extremely significant under moderate stress condition compared with the other two treatments. leaf blade CAT activity differences were extremely significant every treatment day compared with three treatments.4. Microstructure study showed that under drought stress, leaf of soybean seedlings showed this phenomenon that at the initial stage palisade tissue cells became shorter and was in an orderly manner and at later stage cells lost water, were unshaped and disordered situation; drought stress exert an influence on the root that following stress heighten the whole cross section shape of root contained central cylinder generate cells smaller, shrinked and unshaped and cortex parenchyma cells atrophied and not full.