Response of Four Grain Legumes to Water Stress in South-Eastern Queensland. I Physiological Response Mechanisms

摘要

The response of soybean (Glycine max CPI 26671), black gram (Vigna mungo cv. Regur), green gram n(V, radiata cv. Berken) and cowpea (V. unguiculta CPI 28215) to water stress was evaluated in the nfield at Dalby in south-east Queensland. Three stress response mechanisms were identified in each nspecies but the degree of expression varied substantially. nThe Vigna spp. cultivars exhibited a measure of escape through faster development in response nto stress, particularly in the flowering to maturity phase. Black gram and cowpea revealed additional ndevelopmental plasticity in terms of the ability to produce new flushes of flowering when stress was nrelieved late in the life cycle. Variation in phenology of the soybean cultivar in response to stress nwas small. nTwo mechanisms served to avoid dehydration through reduced water loss, viz. (i) stomata1 nclosure in response to falling leaf water potential, and (ii) paraheliotropic leaf movement. Stomata1 nclosure occurred at higher leaf water potentials and the expression of paraheliotropy under stress was nstrongest in Vigna spp. cultivars. Reduced leaf conductances were associated with higher leaf ntemperatures, particularly in soybean where paraheliotropy under stress was small. nThe inter-relationships between stress mechanisms, and some implications of cultivar differences nfor acclimatization to drought, are discussed.