Influence of cytokinins on the methyl jasmonate-promoted senescence in Helianthus annuus cotyledons

Abstract

Cotyledons of seven-day-old sunflower seedlings were pretreated with cytokinins prior to exposure to methyl jasmonate (MeJA). The rate of senescence was then followed by measuring chlorophyll loss, electrolyte leakage, ethylene production, and 1-aminocyclopropane-1-carboxylase (ACC) oxidase activity. MeJA promoted all these senescence parameters and the MeJA effects were partially blocked by cytokinin pretreatment. 8-azaguanine, which has been reported to have anticytokinin activity, blocked the ability of benzyl adenine (BA) to reverse the effect of MeJA on senescence. MeJA also increased SOD and catalase activity, decreased protein content. However, while the cytokinin BA more than overcame the MeJA effect on protein content and SOD activity it did not antagonize the effect of MeJA on catalase.