Effect of supplemental Ca2+ on NaCl-stressed castor plants (Ricinus communis L.)

Abstract

Effect of supplemental Ca2+on NaCl-stressed castor plants (Ricinus communisL.)Greenhouse experiments were conducted to assess the effects of supplemental Ca2+in salinised soil on germination and plant growth response of castor plant (Ricinus communisL. Var. Avani-31, Euphorbiaceae). NaCl amounting to 390 g was thoroughly mixed with soil of seven lots, of 100 kg each, to give electrical conductivity of 4.1 dS m-1. Further, Ca(NO3)2x 4H20 to the quantity of 97.5, 195, 292.5, 390, 487.5, and 585 g was separately mixed with soil of six lots to give 1:0.25, 1:0.50, 1:0.75, 1:1, 1:1.25, and 1:1.50 Na+/Ca2+ratios, respectively. The soil of the seventh lot contained only NaCl and its Na+/Ca2+ratio was 1:0. Soil without addition of NaCl and Ca (NO3)2x 4H20 served as control, with a 0:0 Na+/Ca2+ratio. Salinity significantly retarded seed germination and plant growth, but the deleterious effects of NaCl on seed germination were ameliorated and plant growth was restored with Ca2+supply at the critical level (1:0.25 Na+/Ca2+ratio) to salinised soil. Supply of Ca2+above the critical level further retarded seed germination and plant growth due to the increased soil salinity. Salt stress reduced N, P, K+and Ca2+content in plant tissues, but these nutrients were restored by addition of Ca2+at the critical level to saline soil. In contrast, Na+content in plant tissues significantly increased in response to salinity, but significantly decreased with increasing Ca2+supply to saline soil. The results are discussed in terms of the beneficial effects of Ca2+supply on the plant growth ofRicinus communisgrown under saline conditions.