Strategic difference in drought resistance between haricot beans (Phaseolus vulgaris L.) and chick pea (cicer arietinum L.): stomatal regulation and root growth
2004
Tilahun Amede (International Centre for Tropical Agriculture (CIAT)/African Highlands Initiative (AHI), Awassa (Ethiopia). Systems Agronomist);Sven Schubert (Justus-Liebig University, Giessen (Germany). Institute Fuer Pflanzen-emaehrung))
Earlier research works conducted to identify mechanisms of drought resistance in Phaseolus Vulgaris L. and Cicer arietinum L. under soil water stress of -0.6 Map showed that drought resistance (maintenance of turgor) in check pea was due to a significant decrease in osmotic potential (osmotic adjustment) while in haricot bean it was due to maintenance of high leaf water potential, but not due to osmotic adjustment. Green house experiments were conducted in the University of Hohenheim, Germany to determine whether maintenance of high plant water potential in haricot bean under stress was the function of stomatal regulation and/or root growth. Seven days mild drought (-0.15 Mpa) decreased the water potential to -0.35 and -0.89 Map. Accompanied by a dry matter decrease of 25 and 15% in haricot bean and Chickpea, respectively' higher dry matter decrease in haricot bean was due to reduced CO2 - fixation, whereby photosynthesis was reduced by 75% in haricot bean but only by 20% in chickpea. Significant decrease in the rate of photosynthesis decreased the sugar reserve (glucose, fructose and sucrose) of haricot bean significantly, which could be responsible for the reduced biomass synthesis. Decrease in the rate of photosynthesis was attributed to significant decrease in stomatal conductance. However, water-use-efficiency was significantly higher in haricot bean than in chickpea regardless of water regimes. A rhizotrone experiment showed that root length density of haricot beans was higher than that of chickpea (by a factor of two), accompanied by higher root weight. It was concluded that high plant water potential of haricot beans under stress was not due to osmotic adjustment but it was the function of effective stomatal regulation and robust root system. tion.
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