Effects of kinetin on the growth and development of barley and its interaction with root size

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Abstract
Summary In some plants the roots have been shown to be major sites of cytokinin production. The part they play in controlling growth and development of cereals was studied by spraying barley with kinetin solution and by changing the size of the root system. Two varieties of barley were grown in culture solution and kinetin was applied and root sexcised at the second-, third- or fifth-leaf stage. The kinetin in aqueous solution was sprayed on the leaves, and either most of the root-tips, or an equivalent weight of entire root strands, were removed. Kinetin increased both shoot apex development and the final ear size. The weights of the main shoot and the whole plant also wore increased, particularly by the later treatments. Removing entire root strands decreased the whole plant dry weight more than removing most of the root apices, but the main shoot weight was less affected. Kinetin interacted with root removal, though neither the interaction nor the main effect of root removal showed unequivocally that cereal roots are the site of cytokinin synthesis, possibly because new root tips were regenerated.