GROWTH AND ION UPTAKE OF 4 BRASSICA SPECIES AS AFFECTED BY NA/CA RATIO IN SALINE SAND CULTURE

The influence of supplemental Ca2+ in saline nutrient solutions on germination, growth, and ion uptake of four Brassica species, B. campestris L., B. carinata, A.Br., B. juncea (L) Czern. and Coss., and B. napus L. was studied in sand culture. The addition of 11.25 mM CaCl2 to nutrient solution containing 225 mM NaCl improved percentage of germination of B. napus and B. juncea. but had no significant effect on the germination speed of the four species. There was no significant effect of additional amount of Ca2+ in the saline medium (150 mM NaCl) on the shoot biomass and seed yield of B. carinata and B. campestris. By contrast, shoot dry matter of B. napus and B. juncea increased significantly with the increased in Ca2+ concentration of the growth medium, but their seed yield remained unaffected. Decreased Ca2+ concentrations of the saline growth medium reduced percent oil content in B. carinata, B. juncea, and B. campestris. Increasing Na/Ca ratio of the external medium affected ion uptake differently in different species. In B. carinata, a relatively salt-tolerant species, the concentrations of Ne and K+ in the shoots remained unaffected, but the Cl- concentration was reduced linearly with the increase in external Na/Ca ratios. Root K+ and Ca2+ of the species decreased with the decrease in Ca2+ supply. In B. campestris increasing Na/Ca ratios of the saline medium had no effect on the concentrations of Na+, Cl-, and Ca2+ in the shoots and Na+, Cl-, and K+ in the roots. Only shoot K+ and root Ca2+ decreased consistently. In the highly salt-sensitive species, B. napus, the shoot Na+ was reduced by the addition of Ca2+ in the salt treatment, whereas the Cl- and Ca2+ uptake was promoted by supplemental Ca2+. The root K+ concentrations decreased with the increase in Na/Ca. In B. juncea, which was similar to B. napus in biomass production, high Ca2+ concentration in the salt treatment reduced the shoot Na+ and root Cl- concentratiOns and promoted the K+ uptake. Shoot Na/Ca and Na/K ratios were increased in B. napus and B. juncea at the highest Na/Ca ratio of the growth medium. Shoot K+ selectivity, S(K,Na) (determined as molar ratio of K: Na in tissue to molar ratio of K:Na in external medium) of all species remained unaffected except for B. juncea in which it decreased significantly at the highest Na/Ca ratio. The root K+ selectivity increased in B. carinata.