Effect Of Hydration-Dehydration Cycles On Seed Vigor Of Metasequoia Glyptostroboides

Seed vigor is affected by the combination of heredity and environment,which directly affects seed germination and emergence,and then may affect the reproduction of a species.Under natural conditions,mature seeds often suffer from hydration-dehydration cycles resulted from repeated changes in dry and wet weather caused by such as rainfall and sunny weather.If the seeds fail to germinate in time during absorption,what is the effect of these hydration-dehydration cycles on their vigor? It remains unclear.In the present study,Metasequoia glyptostroboides(a rare and endangered relict plant protected at the national level)seeds were used as experimental materials,a field semi-control experiment and a control experiment in the laboratory were designed and carried out.The semi-control experiment consisted of rain-shading and open-air treatment,and the absorption time(2 and 4 hour,corresponding to unsaturated sbsorption and saturated absorption respectively)and hydration-dehydration cycles in the control experiment,which aimed at investigating the influence of different degree and number of hydration and dehydration cycle in the laboratory and under field natural onditions on the seed vigor of M.glyptostroboides.By a series of plant physiological and biochemical experiments such as germination test,conductivity determination of seed soaking solution,content determination of malondialdehyde,hydrogen peroxide and non-enzymatic antioxidants,and test of antioxidant enzyme activity,following conclusions were drawn:1.under the field semi-control conditions,the seeds treated in the open-air lost vigor and viability faster than the rain-shading treatment,and the antioxidant defense system also changed accordingly.2.for artificial hydration-dehydration cycle treatments,compared with the dehydration treatment after unsaturated absorption,the dehydration treatment after saturated absorption gave rise to worse damages and lost vigor and vitality faster.This was probably due to the dehydration treatment after unsaturated absorption failed to make the antioxidant defense system more effective.3.According to the results of the artificial hydration-dehydration cycletreatments and the filed semi-control experiment,the rapid loss of vigor and vitality of M.glyptostroboides seeds treated through a open-air in field was probably caused by the frequent rainfall and sunny.