Mgc. Franca et al., Differences in growth and water relations among Phaseolus vulgaris cultivars in response to induced drought stress, ENVIR EXP B, 43(3), 2000, pp. 227-237
Relatively little ecophysiological research has been conducted to determine
the responses to drought of Phaseolus vulgaris. Four bean cultivars (cvs.)
from Brazil, A320, Carioca, Ouro Negro and Xodo were submitted to an impos
ed water deficit in order to evaluate the importance of some adaptive mecha
nisms of drought resistance through the analysis of growth parameters, wate
r status, gas exchange and indicators of tolerance mechanisms at the cellul
ar level. During the drought treatment, relative growth rates were more red
uced for A320 and Xodo than Carioca and Ouro Negro. A320 closed its stomata
very rapidly and complete stomatal closure eras obtained at Psi(w) = - 0.6
MPa, in contrast to the other cvs. where stomata were fully closed only at
Psi(w) = - 0.9 MPa. Net assimilation rates were closely related to stomata
l conductances. Mechanisms at the cellular level appeased to be mostly impo
rtant for higher tolerance. Carioca and Ouro Negro, when compared to A320 a
nd Xodo, were characterized by having better drought tolerance mechanisms a
nd higher tissue water retention capacity leading to a better growth under
water deficits. The leaf dehydration rates of those cvs. were slow whereas
those of the drought sensitive cvs. were rapid. The results were confirmed
by the electrolyte leakage test and leaf osmotic potential measurements, wh
ich indicated higher membrane resistance and osmotic adjustment in the two
tolerant cvs. Carioca and Ouro Negro. It appears from this study that despi
te being cultivated in the same geographical region, the four cvs. of P. vu
lgaris displayed somewhat different drought adaptive capacities for prolong
ed drought during the vegetative phase. (C) 2000 Elsevier Science B.V. All
rights reserved.