The effect of autoregulated ipt gene expression, exogenous cytokinins and nitrate on cytokinin metabolism and leaf senescence

coNcLUsroNs l. ttre iptexpressionundeÍthesenescence-specificSÁGí2 promoterresultedin de|ayof |eaÍ senescence,increaseof contentof bioactivecytokininsand nitratereductaseactivityin leavesas wellas to enhancementof nitrateinfluxin plantsgrownunderlimitedN supply. However,the SAG12::iptplantsdid not differfromWT plantsin grainyield components includingthe numberof grainsand grainweight.Resultssuggestthatdelayof leafsenesce of wheat plantsalso delays translocationof nutrientsand metabolitesfrom leaves to developinggrainsafteranthesisand in this way interfereswiththe reproductivestrategy wheatas strictlymonocarpicplantwhichis basedon a programmedfast translocationof metabolitesand nutrientsfrom senescingleavesto the reproductivesinks shortlyafter anthesis. ll. Respondingto the mostlyvaguestatementsthatthe physiologicaleffectsof cytokininsare dependenton plantgenotypeandaffectedbyvariousinternalfactorswe testedtheefficiency of andaromatic(3OHBAR)andan isoprenoid (t-ZR)cytokininon retentionof chlorophyllin detachedoat and wheatleafapices.The efficiencyof thetwocytokininsin preservationof chlorophyllwas differentin the oat and wheatdependingon local or whole adaxialleaf surfacecytokininapplication.The oat and wheatleafpiecesdifferedin the ratesof uptake and the dynamicsof ["H]t-ZRand [JH]3OHBARtranslocationwhichwas..