The effect of temperature on the production and abscission of flowers and pods in snap bean (Phaseolus vulgaris l.)

The effect of temperature on production and abscission of flower buds, flowers and pods was studied in a determinate snap-bean cultivar (cv. Tenderette). Under moderate temperature (e.g. 27/17 °C) the onset of pod development was associated with cessation of flower bud production and with enhanced abscission of flower buds. Raising night temperature from 17 °C to 27 °C strongly reduced pod production, mature pod size and seeds per pod, while an increase in day temperature from 22 °C to 32 °C had smaller and less consistent effects. Pod production under high night temperature was not constrained by flower production since 27 °C at night promoted branching and flower bud appearance. Under 32/27 °C day/night temperature the large reduction in pod set was due to enhanced abscission of flower buds, flowers and young pods (< 3 cm) Flowers had the highest relative abscission followed by young pods and flower buds. Therefore, the onset of anthesis and of pod development were the plant stages most sensitive to night temperature. Pods larger than 3 cm did not abscise but usually aborted and shrivelled under high night temperature. The effects of 32/27 °C were not due to transient water stresses and were observed even under continuous irrigation and mist-spraying.