Response of cereals to cycocel application (Review article)

ABSTRACT Growth retardants are natural or synthetic chemical substances which are directly applied to crops to alter some structural processes. It is expected that these alterations modify hormonal balance and growth leading to increased yield, improved crop quality or facilitated harvesting. Cycocel (CCC) or chlormequat chloride (2chloro ethyl trimethyl ammonium chloride) as a synthetic growth retardant has been recommended for wheat since 1960s. Cycocel inhibits gibberellin biosynthesis via blocking entkaurene synthesis in the metabolic pathway of gibberellin production, resulting in reduced amounts of active gibberellins and consequent reduction in stem elongation. The stem shortening effect of cycocel in such cereals as wheat seems to be less important, due to release of many dwarf and semi dwarf wheat cultivars. However, using cycocel in cereal fields would be inevitable if its effect on grain yield is definite and this area needs further investigation. Importance of cycocel is greater under environmental stress conditions, and more research needs to be focused on cycocelinduced stress tolerance. In this paper, the current knowledge and possible applications of cycocel, which can be used to improve the growth and yield of cereals, have been reviewed and discussed. The role of cycocel to mitigate the harmful effects of drought and salt stresses in cereals is also examined. Furthermore, various biochemical and physiological processes leading to improved cereal crop production under the influence of cycocel are discussed.