Responses to drying of recalcitrant seeds of Quercus nigra L

It has been suggested that rate of desiccation can influence the expression of recalcitrant behaviour in seeds, thus complicating the task of determining which seeds are truly recalcitrant. The objective of this study was to see if variable rates of desiccation influenced such behaviour in Quercus nigra L., a tree seed known to be recalcitrant. Acorn moisture content, leachate conductivity, and germination were determined at various times during desiccation at three rates at 27 and 40 degrees C. Moisture contents and germination decreased as the severity of desiccation increased. Leachate conductivity increased slightly but was not a sensitive indicator of loss of viability. The critical (lethal) moisture content for these acorns was 10-15%, although rehydration within 48 h of reaching this level prevented death in about 25% of the acorns. At 27 degrees C any desiccation treatment that produced losses of 30-50 mg of moisture per g of acorn dry weight per day should be suitable as a test for recalcitrance in the genus. Apparent physiological or fungal damage at 40 degrees C rules out the higher temperature for such a test. (C) 1996 Annals of Botany Company