DELAY OF SENESCENCE IN WHEAT LEAVES BY CYTOKININS, NICKEL, AND OTHER SUBSTANCES

Abstract

Single-drop applications of nickel salts, cobalt salts, or kinetin induced similar patterns in the delay of the rapid senescence of detached wheat leaf tissue (Triticum aestivum compactum 'Little Club'). Tissues near treatment sites remained green as more distant parts of the leaves became chlorotic. Yeast extract, coconut milk, and benzimidazole also preserved the green pigment but the activity of the last two was sometimes displaced away from treatment sites. Total nitrogen content increased markedly in the portions of detached leaves treated with nickel sulfate or kinetin, indicating that nitrogenous substances moved from senescing tissues into the green tissues at treatment sites. The green tissues increased in dry weight and stained heavily with I–KI.The slowly senescing tissues of attached leaves were kept green by high concentrations of either kinetin or benzimidazole in treatment drops but not by nickel sulfate. However, moderate concentrations of nickel sulfate or kinetin increased the dry weight and retarded the slow natural loss of nitrogen content of attached leaf tissue, indicating that both substances induced a temporary senescence delay.