RESPONSES TO DRYING OF RECALCITRANT SEEDS OF QUERCUS-NIGRA L

It has been suggested that rate of desiccation can influence the expre ssion of recalcitrant behaviour in seeds, thus complicating the task o f determining which seeds are truly recalcitrant. The objective of thi s study was to see if variable rates of desiccation influenced such be haviour in Quercus nigra L., a tree seed known to be recalcitrant. Aco rn moisture content, leachate conductivity, and germination were deter mined 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 bu t was not a sensitive indicator of loss of viability. The critical (le thal) moisture content for these acorns was 10-15%, although rehydrati on within 48 h of reaching this level prevented death in about 25% of the acorns. At 27 degrees C any desiccation treatment that produced lo sses 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 physiol ogical or fungal damage at 40 degrees C rules out the higher temperatu re for such a test. (C) 1996 Annals of Botany Company