ABSTRACT
Lack of oxygen due to flooding results in reduced auxin transport. Flooding substantially increases Indoleacetic acid (IAA) level in the shoots which results in enhanced ethylene production, while the build up of ethylene disrupts IAA transport. Significant positive correlations have been found between several rice cultivars relative to ethylene production and elongation growth. Rhizosphere oxygen deficiency enhances ethylene biosynthesis in roots. S. Y. Hwang and T. T. Van Toai report that the roots of young maize plants pretreated with abscisic acid resulted in seedlings that exhibited a 10-fold increase in tolerance to anoxia. Root hypoxia also increases ethylene synthesis in shoots. Ethylene most likely plays a significant part in the responses of roots at or near the soil surface where some oxygen from the air may be available for growth reactions to ethylene and for ethylene biosynthesis. Excessive moisture reduces productivity of crops such as soybean, millet, corn and cabbage by as much as 50 – 75 per cent.
