DRYING RATE ALTERS SOLUBLE CARBOHYDRATES, DESICCATION TOLERANCE, AND SUBSEQUENT SEEDLING GROWTH OF SOYBEAN (GLYCINE-MAX L. MERRILL) ZYGOTICEMBRYOS DURING IN-VITRO MATURATION

In vitro culture of soybean (Glycine max [L.] Merr.) seeds and zygotic embryos is used to study factors affecting seed growth, maturation, d esiccation tolerance, and germination. While germination of in vitro m atured zygotic embryos is usually greater than 80%, seedling growth is often lower than that of seeds matured in planta. Soluble carbohydrat es in axis and cotyledon tissues of soybean zygotic embryos at 0-32 da ys of in vitro culture were assayed before drying, after fast drying, and after slow drying and related to changes in germination and axis g rowth of seedlings. Germinability was improved by slow drying. A low m ass ratio of sucrose to raffinose plus stachyose was associated with g erminability but was not sufficient for the maintenance of high seedli ng growth after prolonged culture in vitro. The loss of seedling growt h as a function of days in culture correlated (r(2) = 0.94) with a dec line in stachyose concentration in axis tissues after slow drying. Tot al pinitol did not exceed that present in embryos before culture, and accumulation of galactopinitols and fagopyritol B1 was limited in embr yos gown in vitro. Responses of zygotic embryos to in vitro culture ma y be useful in understanding problems associated with the conversion o f soybean somatic embryos to plantlets and vigorous growth of plantlet s. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.