Exogenous ABA as a Modulator of the Response of<i>Sorghum</i>to High Salinity

Abstract

Treatment of &lt;it&gt;Sorghum bicolor&lt;/it&gt; (L.) Moench, cv. 610, with abscisic acid (ABA) during the first week of sahnization with 150 mol m−3 NaCl induced enhancement of growth and accelerated adaptation to high salinity (300 mol m−3 NaCl) Adaptation is defined as the development of the ability of the plant to survive, grow, and set seeds upon exposure to a NaCl concentration which is lethal for the unadapted plant In the absence of ABA the saline pretreatment requires 20 d for the development of adaptation (Amzallag &lt;it&gt;et al.,&lt;/it&gt; 1990), with ABA treatment the same result is achieved within approximately one week The exposure of the plants to non-lethal salinity (150 mol m−3 NaCl) apparently triggers a transient sensitivity to ABA lasting for about 8 to 10 d following the beginning of sahnization This period coincides with an increase in leaf PEP carboxylase activity which seems to occur faster if the plants are treated with ABA. Exogenous ABA-induced enhancement of growth and control of shoot Na+ concentration, occur at a lower ABA concentration (&amp;ap;10 mmol m−3) than the induction of adaptation to salinity which oc curs at &amp;ap;40 mmol m−3 or above. The lowered shoot Na+ concentration which is induced by a low ABA concentration is not sufficient to induce survival of the plants in high salinity (300 mol m−3 NaCl).