PHYSIOLOGICAL AND MORPHOLOGICAL MECHANISMS OF DROUGHT RESISTANCE IN SORGHUM AND PEARL MILLET. I. EFFECTS OF LEAF TREATMENT WITH ABSCISIC ACID. II. SEED PRE-TREATMENT WITH ABSCISIC ACID. III. COMPARATIVE SHOOT AND ROOT DEVELOPMENT. IV. LEAF SURFACE MORPHOLOGY (WATER USE EFFICIENCY, EPICUTICULAR WAX, CUTICULAR TRANSPIRATION, STOMATA)

TL;DRAbstract

The differential effects of exogenously applied abscisic acid (ABA) on leaves of stressed and non-stressed sorghums was investigated. In general, root to shoot ratios were increased by the treatment in well-watered plants. Shoot heights, rooting depth, and total shoot and root dry weights were nearly unaffected in water stressed plants, while grain yield and seed number were increased. Application of gibberellic acid and kinetin counteracted the effects of the ABA. A technique was also developed for treating sorghum seeds with ABA solutions which induced greater drought resistance. The ABA seed treatment increased plant heights and grain yields in droughted plants. With well-irrigated plants, the effects of the seed treatment were variable in that it increased yields in some genotypes and markedly decreased them in others. A comparative study of shoot and root development in sorghum and pearl millet showed the millets to have smaller leaf areas and a larger number of main adventitious

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