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Effect of drought stress on proteolytic activities in Phaseolus and Vigna leaves from sensitive and resistant plants
Author(s) -
RoyMacauley H.,
ZuilyFodil Y.,
Kidric M.,
Thi A. T. Pham,
Silva J. Vieira
Publication year - 1992
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1992.tb05268.x
Subject(s) - phaseolus , vigna , cultivar , biology , botany , horticulture , chemistry
Although much information is available concerning the effect of senescence on cell proteolytic activities, few reports are devoted to the impact of drought stress. Our aim was to study the influence of water deficit on the cell proteolytic potential, and to determine whether or not it could be used as a physiological parameter for screening varieties for tolerance to drought. We have used Phaseolus and Vigna species differing in their senstivity to water deficit: V. unguiculata L. Walp. cv. EPACE (resistant), V. unguiculata L. Walp. cv. IT83D (moderately senstive) and P. vulgaris L. cv. Carioquinha (sensitive). The plants were subjected to controlled water conditions. Proteolytic activities were assayed using azocasein in the case of leaf extracts and [ 14 C]‐methylated casein in the case of cell compartments: soluble fraction, membrane fraction and isolated, purified chloroplasts. The results indicate that the leaf extracts contained 3 groups of proteinases with optimum pH at 4.5, 5‐6 and 8.5 for the Vigna cultivars and 5.0, 6.5 and 9.0 for the Phaseolus cultivar. The sensitive P. vulgaris Carioquinha showed higher caseinolytic activities than the other tow cultivars in response to water deficit. As regards cell fractions, proteolytic activities were determined for pH values of 4.5, 6.0 and 9.0. In soluble fractions of stressed plants, proteolytic activities increased at all the pH values tested; this clearly correlated with the drought sensitivity level of the plants, especially at pH 4.5. The same phenomenon was observed in the case of membranes and purified chloroplasts of the sensitive cultivar. Under drought stress, the proteolytic potential of the cell increased especially in the vaculoar sap (soluble fraction). The higher activities observed for all the cell compartments in the sensitive cultivar could be responsible, at least partly, for the rapid degradation of leaf and chloroplast proteins under drought. The use of [ 14 C]‐methylated casein and soluble cell fractions seem to allow a clear differentiation between cultivars with respect to the drought tolerance at the cellular level.