Ethylene binding during leaf development and senescence and its inhibition by silver nitrate.

Ethylene binding in situ was tested in leaves of tobacco (Nicotiana tabacum L. var. Xanthi) and of gynoecious and monoecious genotypes of cucumber (Cucumis sativus L.) during their development and senescence. Ethylene binding per gm fresh leaf remained constant during early stages of tobacco leaf development. It decreased in fully expanded leaves and during senescence of detached tobacco leaves. On a per leaf basis, ethylene binding increased as the leaf developed. The pattern for changes in ethylene binding by gynoecious and monoecious cucumber leaves were different from each other. Short-term treatment of detached tobacco and cucumber leaves with a solution of AgNO(3) (50 μM) markedly decreased their ability to bind ethylene concomitant to an inhibition in chlorophyll breakdown. The data support the hypothesis that ethylene-induced chlorophyll breakdown during leaf senescence may require the binding of ethylene to its receptor in vivo.