Effects of Mineral Nutrition on Endogenous Cytokinins in Plants of Sunflower (Helianthus annuusL.)

Abstract

The effects of inorganic nutrients on the levels of endogenous cytokinins in plants of sunflower (Helianthus annuus L.) grown in sand culture were studied. Low levels of nitrogen resulted in rapid decreases in the levels of cytokinins extracted from leaves, buds, roots, and root exudates. Similar effects were observed with phosphorus deficiency, but the effects of potassium deficiency on the cytokinin content of leaves was less marked. The cytokinin content was higher in plants supplied with nitrogen as nitrate than in those supplied with ammonium sulphate or ammonium nitrate. The decline in cytokinin levels in derooted shoots and detached leaves could be reversed by supplying them with nutrient solution. Although leaves on intact plants may normally be dependent upon the supply of cytokinins from the roots, isolated leaves have the capacity for cytokinin production when supplied with inorganic nutrients.