Abstract

Alkalinity is likely the most important factor that adversely affects plant growth and development. In this study two sorghum (Sorghum bicolor L.) cultivars (alkalinity sensitive cultivar Giza 15 and alkalinity tolerant one ICSR 92003) were subjected to various alkaline salt concentrations of 0 (control), 25, 50, and 75 mM Na2CO3 and compared in terms of growth vigor of root, shoot and flag leaf as well as flag leaf anatomical features of both cultivars. The experiment was conducted in pots to evaluate the beneficial effect of grain presoaking in sodium meta-silicate (Na2Sio3.5H2O at 1.5 mM) on the two sorghum cultivars. In general, alkalinity stress caused noticeable reduction in almost all growth criteria of root, shoot and flag leaf which was consistent with the progressive alteration in flag leaf natomical features of both cultivars during grain filling. In relation to sorghum cultivar, the sensitive was more affected by alkalinity stress than the tolerant one. Generally, the application of silicon induced marked increase in growth vigor of root, shoot and flag leaf Moreover, the anatomical features in alkalinized plants were stimulated by silicon in both sorghum cultivars since silicon induced marked increase in conducted canals (xylem area and phloem tissue area), leaf thickness, ground tissue thickness, number of vascular bundle tissues, proto-xylem vessel area as well as meta-xylem vessel area and tracheids area of both sorghum cultivars either exposed or not exposed to alkalinity stress.