Methanol Accumulation in Maturing Seeds

During in vitro growth and maturation of soybean seeds, cessation of embryo growth and dry weight accumulation occurred in the presence of abundant C and N nutrients. Axis followed by cotyledon tissues changed from green to yellow, and post-harvest germination potential declined if cultured after yellowing of axis tissues. A tissue specific accumulat;on of methanol occurred during the in vitro culture of immature seeds (i.e. initially 50 to 70 mg fresh weight) to maturity in liquid medium. Methanol accumulated to 3.0 g m−3 or 50 µg seed−1 in the medium, while methanol decreased from 37 to about 3.0 ∧µg g−1 fresh weight in cotyledons. By contrast, axis tissues increased 20-fold in methanol concentration to 90 µg g−1 during 20 d in culture. Ethanol was present only in trace amounts in axis tissues and medium. Addition of exogenous methanol vapour to in situ grown seeds during precocious maturation decreased subsequent seedling vigour and germination with increasing levels of exposure. Methanol accumulation in axis tissues during the germination phase was not correlated with high temperature and tissue water content treatments which simulated pre-harvest deterioration of seeds. However, the accumulation of methanol during in vitro seed development and maturation in liquid culture may contribute to reduced post-harvest germination performance.