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Abstract Experiments in which Phaseolus vulgaris seeds were germinated and transplanted in Hoagland nutrient solution (1/4 -strength) either singly or supplied with decreasing concentrations ofK or P were conducted. A third experiment was carried out in which seedlings and plants were stressed with NaCl. 2- All these experiments were designed to investigate the possible effects of stresses on growth, pigment content, metabolite content and activities of some related enzymes in seedlings and adult plants of Phaseolus vulgaris. ” 3- It became apparent that K-, P- deficiency and NaCI in the culture solution induced significant decreases in all growth parameters determined. (except for root length in Phaseolus seedlings and plants treated with decreasing concentrations of either K or P). 4- In relation to control seedlings and plants, Na, K and Fe contents were significantly decreased whereas Ca, Mg and P contents were increased significantly in K- deficient seedlings and plants. In P- deficient plants Na, K and P contents were significantly decreased whereas Ca++,Mg++ and Fe+++ contents were significantly increased. NaCI-stressed Phaseolus seedlings and plants showed significant increase in Na, Mg, P and Fe contents whereas K+ and Ca++ contents were significantly decreased. 5- Phaseolus vulgaris seedlings and plants stressed with either K-, Pdeficiency or salinity appeared to show significant changes in the total amount and in the relative composition of the nitrogen and carbohydrate pools. -In K_ and P- deficient as well as in NaCI- stressed Phaseolus seedlings .and plants, Chl.a, Chl.b, anthocyanin and xanthophyll pigment contents were significantly decreased whereas carotenoid content was found either to increase significantly (with K- and P- deficiency) or to decrease significantly (with NaCl- stress), as compared with unstressed seedlings and plants. 7- In relation to control (unstressed plants), K-, P- and NaCI- stressed Phaseolus seedlings and plants exhibited pronounced significant changes in the total amount and in the relative composition of organic and amino acid pools. 8- Compared with control Phaseolus seedlings and plants, the activities of both invertase, a-amylase and nitrate reductase appeared either to increase significantly (with P-deficiency and NaCI stress) or to decrease significantly (with K- deficiency). PFK activity was found to increase significantly (with K- and NaCl- stress) or to decrease significantly (with p, stress) whereas G3PDH activity was increased significantly (with K- stress) or decreased significantly (with P- and NaC!- stress). 9- The present results are discussed in relat,ion to the mechanisms of action of K-, p; and NaCI- stresses put forward for plarit metabolism and the associated effects maintained on growth of Phaseolus seedlings and plants. |