DROUGHT ENHANCES STOMATAL CLOSURE IN RESPONSE TO SHADING IN SORGHUM (SORGHUM-BICOLOR) AND IN MILLET (PENNISETUM-AMERICANUM)

When field-grown sorghum (Sorghum bicolor (L.) Moench) and millet (Pen nisetum americanum (L.) Leeke) plants are subjected to drought, the sp eed of stomatal closure in response to darkness is enhanced in compari son with the speed observed in well-irrigated control plants. This sha de-induced closure is most apparent at early stages of desiccation and is not rapidly reversible. These results need to be considered when d eveloping protocols for the measurement of photosynthetic light respon se curves in the held. The sensitivity to crop water status of this st omatal closure response potentially provides a very valuable means for detection of the early stages of soil drying, and may also provide op portunities for screening different varieties for their adaptation to drought conditions.