ABSTRACT

Salinity inhibits growth and development of most plants. Inhibition of shoot and root development is the primary response to the stress. Growth, morphology, anatomy, and physiology of roots are affected by salinity. Changes in water and ion uptake and production of hormonal signals that communicate information to the shoot might induce changes in development. Since root growth is usually less sensitive to salt stress than shoot growth, an increased root/shoot ratio is often observed when plants are subjected to saline conditions (Cheeseman, 1988; Rawson et al., 1988; Cruz and Cuatreno, 1990). Root growth of halophytes may be affected differently (Waisel, 1972, 1989). The underlying mechanisms involved in the inhibition processes of root growth are not clearly established. Restriction of root growth by salinity reduces the soil volume that can be explored by the root and hence the availability and uptake of water and essential minerals. The diminished supply of nutrients to the shoot may contribute to growth reduction (Delane et al., 1982; Pitman, 1984; Bernstein et al., 1993a,b; Lazof and Bernstein, 1998). The increase in root/shoot ratio under stress which might diminish the demand for element supply to the shoot has a potential to increase the ability of the root to supply those elements, and hence might present an adaptive advantage (Cheeseman, 1988). A potentially negative effect of such a change is the decreased ability of the shoot to supply assimilates to the roots and the growing tissues, which is likely to affect plant development and survival particularly under long-term salinization (Munns and Termaat, 1986; Cheeseman, 1993).