Determination of optimum storage conditions for orthodox seeds.

摘要

Plant genetic resources play a vital role in the breeding of new crop varieties. Consequently, maintenance of plant biodiversity has become a global concern. Storage of orthodox seeds in genebanks is a simple and cost-effective means to conserve germplasm. Seed moisture content (MC) and temperature (T) are the most important factors controlling seed longevity during storage. Obtaining a better understanding of the interaction of these two factors, along with storage time, is the principle objective of this study.; Seeds of cucumber, lettuce, maize, onion, pea, and watermelon were equilibrated over 12 relative humidities (RH) at T from 5 to 50°C to determine the interactive effect of RH and T on MC. Best-fit subset models were selected from a complete third order model. All six best subset models had the same functional form. These models indicated that seed MC increased as RH increased and decreased as T increased but RH had the greater influence.; A second experiment involved lettuce and soybean seeds equilibrated over 12 RH at T of 5 to 50°C to determine the interaction of storage duration, T, and RH on seed quality. The best-fit subset models were selected from a complete third order model. All best-fit subset models had different functional forms. The selected models showed accelerated aging in both species when they were dried to extremely low MC. Optimum RH for storage was about 20--22%. Based on the models, D, T, RH, and their interaction are all important factors which determine seed longevity.; A third experiment involved lettuce and soybean seeds equilibrated at approximately 1%, 25% and 75% RH at 35°C to determine the physiological reactions occurring at low MC and their effects on seed quality during storage. Seed MC, germination, root length, volatile production, leachate conductivity, and dehydrogenase activity were assayed at approximately two month intervals during storage. This experiment showed maximum seed germination and vigor during storage when lettuce and soybean seeds were stored at optimum MC (4--5%). Storage at extremely low MC resulted in reduced germination and vigor. However, seed germination and vigor were improved greatly at extremely low MC when lettuce seeds were stored in N2.; In conclusion, greater deterioration was observed not only at high MC but also under over-dry conditions. The detrimental effect was minimized when seeds were stored at 20--22% RH. These models can be used as a guide in estimating levels of deterioration of orthodox seeds during storage periods given storage T and RH.