Effects Of PEG Pretreatment On Physiology Characteristic Of Rice Seeding Under Salt Stress

Hydroponic experiments were carried out to study the effects of10%PEG inenhancing rice (Oryza sative L.) Liaoxing1and Shennong265resistance to salt stress.Data were collected on leaf and root relative water content, chlorophyll (Chl) content,hydrogen peroxide (H2O2) content, antioxidant enzyme activities, such as catalase(CAT), superoxide dismutase (SOD), guaiacol peroxidase (POD), osmoregulationsubstances, such as proline, soluble sugar and soluble protein, and malondialdehyde(MDA) content. The test results are as the followings：The leaf relative water content of Liaoxing1and Shennong265decreasedgradually with stress time prolongation under salinity stress. The root relative watercontent of Liaoxing1was in agreement with that of its leaf, but the root relative watercontent of Shennong265was kept on first declining and then increasing. Under10%PEG pretreatment, the leaf and root water-holding capacities of Liaoxing1improved insignificantly and that of Shennong265enhanced gradually with timeincreasing, especially root water-holding capacities enhanced significantly.Chlorophyll content of Liaoxing1was marked lower than that of the controls.However, there was no significant difference in chlorophyll content of Shennong265,when compared with the controls. Chlorophyll content of Liaoxing1and Shennong265enhanced compared to that of non pretreatment under10%PEG pretreatment.Photosynthetic products increase was benefit for enhancing resistance. The rootactivities of Liaoxing1and Shennong265appeared first a decreasing and thenincreasing (24h-72h). Under10%PEG pretreatment, the root activities of Liaoxing1was higher than that of the controls, but decreased with time prolongation. However,the root activities of Shennong265enhanced gradually.Under salinity, hydrogen peroxide (H2O2) contents in all treatments were higherthan that of the controls, except the root of Liaoxing1. The leaf and root H2O2contentof Liaoxing1and Shennong265were lower than that of non pretreatment under10% pretreatment, which indicated that10%pretreatment enhanced resistance byincreasing root activities. MDA content of Liaoxing1and Shennong265increasedwith time prolongation under salinity stress. But MDA content decreased under10%PEG pretreatment.Under salinity stress, SOD activity of Liaoxing1and Shennong265enhanced withtreatment time prolongation. CAT activity of Liaoxing1appeared first an increasingand then decreasing, but CAT activity of Shennong265showed increasing trend alltime. However, the trend of POD activity was opposite. POD activity of Liaoxing1showed increasing tend all time, but POD activity of Shennong265appeared first anincreasing and then decreasing trend. Under10%PEG pretreatment, the activities ofSOD, CAT, POD of Liaoxing1and Shennong265kept increasing, which increasedresistance and partially protected the seedlings from salinity stress during thefollowing growth period.Under salinity stress and10%PEG pretreatment, proline content of Liaoxing1andShennong265appeared increasing trend. Soluble sugar content were kept on anincreasing trend, especially, they were all kept at a high level at the end of thetreatment. However, soluble protein content appeared a gradual decreasing trend. Thisshowed that the action of proline, soluble sugar and soluble protein were difference.Proline and soluble sugar played an effective regulating role for these two speciesseedlings．...