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United States Department of Agriculture

Agricultural Research Service

Title: Water Content-Temperature Interactions Regulate Seed Aging

Authors
item Walters, Christina
item Hill, Lisa
item Wheeler, Lana
item Rao, N.K. - ICRISAT, PATANCHERA, INDI
item Hu, X - CAAS, BEIJING, CHINA
item Engels, J.M.M. - BIOVERSITY INTERNATIONAL

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: July 6, 2008
Publication Date: July 6, 2008
Citation: Walters, C.T., Hill, L.M., Wheeler, L.J., Rao, N.K., Hu, X., Dulloo, M.E., Engels, J.M.M. 2008. Water content-temperature interactions regulate seed aging. 9th International Conference on Seed Biology. July 6-11, 2008. Olsztyn, Poland. pp. 280. Meeting Abstract

Interpretive Summary: Water content and temperature are important factors that influence the duration of seed survival in storage. The interacting effect of these two factors and the consequences on seed longevity is rarely recognized. An experiment to quantify the interaction was begun in 1994, using lettuce (Lactuca sativa) seed and a multifactorial design that was replicated in three national laboratories. The data from this experiment explain differences in research results that generated a controversy about ‘ultra-dry technology.’ The maximum half-life of lettuce seeds stored at 50, 35 and 20C is about 700, 5000 and near 9000 days, respectively. Maximum half-lives were observed in seeds containing < 0.01, < 0.03, and < 0.055 g H2O/g dry mass, and correspond to 18 to 22% relative humidity, at the three respective storage temperatures. Only beneficial effects of drying were observed at 50C; no detrimental effects of drying were observed at 35C; and it is too early to determine whether extremely dry seeds aged more rapidly at 20C. Achieving RH between 18 and 20% at the storage temperature required drying seeds at room temperature to < 0.5, 10 and 28% RH for 50, 35 and 20C storage, respectively. Water contents at which maximum half-lives were observed were well below water contents at which glass transitions occurred, perhaps indicating relaxation events in addition to glassy transitions measured using differential scanning calorimetry. These events and the recognized plasticizing effect of water on glasses within seeds is further evidence of a water content-temperature interaction.

Technical Abstract: Water content and temperature are important factors that influence the duration of seed survival in storage. The interacting effect of these two factors and the consequences on seed longevity is rarely recognized. An experiment to quantify the interaction was begun in 1994, using lettuce (Lactuca sativa) seed and a multifactorial design that was replicated in three national laboratories. The data from this experiment explain differences in research results that generated a controversy about ‘ultra-dry technology.’ The maximum half-life of lettuce seeds stored at 50, 35 and 20C is about 700, 5000 and near 9000 days, respectively. Maximum half-lives were observed in seeds containing < 0.01, < 0.03, and < 0.055 g H2O/g dry mass, and correspond to 18 to 22% relative humidity, at the three respective storage temperatures. Only beneficial effects of drying were observed at 50C; no detrimental effects of drying were observed at 35C; and it is too early to determine whether extremely dry seeds aged more rapidly at 20C. Achieving RH between 18 and 20% at the storage temperature required drying seeds at room temperature to < 0.5, 10 and 28% RH for 50, 35 and 20C storage, respectively. Water contents at which maximum half-lives were observed were well below water contents at which glass transitions occurred, perhaps indicating relaxation events in addition to glassy transitions measured using differential scanning calorimetry. These events and the recognized plasticizing effect of water on glasses within seeds is further evidence of a water content-temperature interaction.

Last Modified: 4/17/2014
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