| Ultra-dried seed storage is a technique used to reduce the seed moisture content to less than 5%, which is the lowest limit for seed to be safely stored at ambient temperature according to traditional opinion.This technology can greatly reduce the cost of constructing and maintaining seed banks and has a potential positive economic effect and promising application in germplasm conservation. Pinus tabulaeformis seeds, Platycladus orientalis seeds, Robinia pseudoacacia seeds and Caragana microphylla seeds which are several important afforestation species in arid and semiarid areas were studied using the method of ultra-drying and accelerated aging. It can support vegetation restoration in arid and semiarid areas of northwest China. Further more, it may benefit the storage of these kinds of seeds.With the method of drying by silica gel, Pinus tabulaeformis seeds were dried from 6.4% to 5.3%, 4.1%, 3.2% and 2.5% moisture content, Platycladus orientalis seeds were dried from 6.8% to 5.1%, 4.4%, 3.7% and 2.2% moisture content, Robinia pseudoacacia seeds of Yan'an City and Wuqi City were dried from 6.9% to 5.9%, 4.8%, 4.2% and 3.6%, and from 7.4% to 6.3%, 5.1%, 4.3% and 3.8% moisture content, Caragana microphylla seeds of Wuqi City were dried from 6.7% to 5.5%, 4.6%, 4.1% and 3.7% moisture content, respectively, the germination energy, germination percentage, germination index, vigor index, relative conductivity, dehydrogrnase activity andα-amylase activity were measured. After drying the seeds were accelerated aged (50℃, 30d), and some physiological indices, including the electrical conductivity, dehydrogenase activity andα-amylase activity were tested. The results are as follows:1 The order of seed drying velocity is Pinus tabulaeformis>Platycladus orientalis>Robinia pseudoacacia>Caragana microphylla.2 Seed germination energy, germination percentage, germination index, vigor and index activities of dehydrogenase andα-amylase kept the high level with Pinus tabulaeformis seed moisture content no less than 3.2%, Platycladus orientalis seed moisture content no less than 3.7%, Robinia pseudoacacia seed from Yan'an City moisture content no less than 4.8%, Robinia pseudoacacia seed from Wuqi City moisture content no less than 4.3%, Caragana microphylla seed moisture content no less than 4.6%. It is feasible for all the tested seeds drying to below 5%.3 After aging 30 d in temperature of 50℃, seeds with various moisture contents have different ability of deterioration-resisting. And seeds with low moisture contents have stronger ability of deterioration-resisting than seeds with high moisture contents have. For Pinus tabulaeformis seeds with 3.2% moisture content, Platycladus orientalis seeds with 3.7% moisture content, Robinia pseudoacacia seeds from Yan'an City with 4.8% moisture content, Robinia pseudoacacia seeds from Wuqi City with 4.3% moisture content, Caragana microphylla seeds with 4.6% moisture content, after aging, their germination percentage, vigor and activities of dehydrogenase andα-amylase are higher than those of seeds with initial moisture contents, and their relative conductivity is lower than the latter's.4 After moisture content drying under 5%, four kinds of seeds keep high level of germination percentage and vigor, their ability of deterioration -resisting is stronger than that of seeds with initial moisture content,and their physiological characteristics are not changed compared to seeds with initial moisture content. So it is frasible for four tested seeds and their optimum moisture contents are 3.2% for Pinus tabulaeformis,3.7% for Platycladus orientalis,4.8% for Robinia pseudoacacia from Yan'an City, 4.3% for Robinia pseudoacacia from Wuqi City and 4.6% for Caragana microphylla. 5 Robinia pseudoacacia seeds harvested in Yan'an City and Wuqi City have different quality. They have different optimum moisture content more or less, indicating that seed source and seed quality have certain effects on the ability of dry-resisting. |
