The Mechanism Of Polyamine Enhanc Ing Of The Tolerance Of Maize(Zea Mays L.)Seedlings To Osmotic Stress

The research aimed to probe into the mechanism of polyamine enhancing the tolerance of plants to drought stress. Nongda 108 (drought-tolerant) and Xundan 13 (drought-sensitive) under osmotic stress with exogenous Spd treatment after 7 days later,which effect on seeding growing, photosynthesis, respiration, antioxidant capacity and organic osmolyte,the stress adapt protein in maize seeding leaf was also researched, result as follows:1. Under normal conditions,the relative water content relative dry weight increase rate and chlorophyll content were little changed in two maize cultivars seedling leaves.At the same time,there is a dynamic balance between MDA content,H2O2 content,activity of PM-NADPH oxidase and antioxidant enzymes(SOD,CAT, APX)of activity,and the Protein content,organic osmolyte in maize seedling leaves.2. The results showed that water content in leaves, relative dry weight increase rate, chlorophyll content and protein content of two maize cultivars were rapidly declined compared with control treatment under osmotic stress, on the contrary, MDA content in leaves and H2O2 content were increased dramatically, and organic osmolyte content was not significantly changed. The results means that drought stress destroyed the balance of active oxygen species production and elimination between enzymatic system and non-enzymatic system, which endangered the growing of maize seeding.3. The relative water content(RWC) reduction, relative dry weight increase rate, chlorophyll content reduction, MDA content and H2O2 content increasing rate in maize seeding leaf were restrained after supplying exogenous Spd under osmotic stress, while the activity of antioxidant enzyme(SOD,CAT,APX) , Organic osmolytes and protein content were increased, which all increased the maize osmotic regulation ability and maintained lower osmotic potential, therefore maize drought resistance was increased.4. The SDS―PAGE showed that Xundan20 has showed protein belt, only showed in Nongda 108, near 20.1KDa under the co-treatment of PEG+Spd, which means Xundan20 and Nongda 108 exhibit Consistency, This further shows that Spd can increase the plants drought resistance in many ways, and the possible reason is that combined action of Spd with other factors, which affected the transcription and the translation of DNA, and then guided the synthesis of the stress adapt protein .5. Polyamines improve the mechanism of drought resistance of maize is, the polyamine restrained the water retaining capacity and decreased chlorophyll content, at the same time, MDA content, hydrogen peroxide content and plasmalemma NADPH oxidase activity had been increased in maize seeding, the antioxidant enzyme activity in maize seeding leaf was increased, promoted the cumulated of organic osmotic matter, induced the stress adapt protein expression in maize seeding, and promoted maize seeding growth and metabolism, therefore enhanced the drought resistance ability in many ways.