Three-week-old nodulated faba bean plants were subjected to two levels of water stress (0.5 and 0.25 field capacity; soil water content of 20 and 10%) for five weeks. Half of the stressed plants was treated with potassium chloride (KC1) at 10 (K1) and 150 mg (K2)/kg soil at the beginning of water deficit. Nodulation was examined and some nodule activities were assayed. Nodulation, nitrogenase activity, total nitrogen (N), and dry matter yield were significantly decreased by increasing stress but were significantly higher with the two levels of potassium (K) supply. Leghaemoglobin and protein contents of cytosol as well as nodule protease and invertase were severely depressed by drought stress. Soluble carbohydrate contents of nodules, however, was significantly increased. Protein and leghaemoglobin contents and enzyme activities were greater with K fertilization but less soluble carbohydrate was accumulated. The results indicate that K supply, particularly at the 150 mg/kg soil level, increased faba bean resistance to water stress.

Abstract: Bean seedlings 7-days old were left to grow for 10 days in hydroponic cultures containing 0, 5, 15 ppm Nickel as NiCl2 Calcium was added (1 mM or 5 mM) in combination with Nickel. Growth criteria, mineral contents, nickel distribution and metal-binding proteins were investigated. The fresh and dry weights of roots and shoots were sharply reduced especially at the higher dose (15 ppm Ni+2). The content of some elements (K, Na , Ca, Mg and Mn) of roots and shoots were variably affected in presence or absence of calcium. Nickel was accumulated in roots more than in shoots. Fractionation of roots and shoot of bean plants revealed that the accumulation of Nickel was in the insoluble form (cell wall), while the remainder (the soluble form) was bound to proteins in the form of metalloproteins. Calcium reduced the toxic effect of nickel especially at the low dose (5 ppm). It was found that calcium reduced the uptake of nickel by roots and enhanced the synthesis of proteins, which form metal-binding proteins.