Cytokinin metabolism in tomato plants. II. Metabolites of kinetin and benzyladenine in decapitated roots

Abstract

Decapitated tomato plants were supplied via the roots with [8-14 C]-kinetin or [8-14 C]-benzyladenine in a nutrient solution for a period of 24h . After this time the root material, the root sap produced during the 24h period and the nutrient solution remaining at the end of the experiments were analysed for cytokinins . HPLC techniques and chemical treatments were used to tentatively identify radioactive metabolites formed . Uptake of kinetin and benzyladenine by the roots was found to be limited but once within the root tissues metabolism was both rapid and extensive .

The in vitro metabolism of [8-14C]benzyladenine by excised organs of tomato plants

“…Notwithstanding, the metabolites detected coincide with those recovered earlier [8,25] . The major metabolite detected in all tissues had a retention time of 48 min .…”

“…This indicates therefore, that degradative metabolism while greatest in the root is not confined to this organ . Furthermore, the presence of a small amount of radioactivity coincident with BARMP in the roots corresponds with Forsyth and Van Staden's [8] report but contrasts with the accounts of other researchers [11,13,24] where BARMP was the major BA metabolite detected in the systems studied . A recent report comparing extraction techniques for cytokinin nucleotides suggests that this discrepancy need not be due to extraction procedures [22] .…”

“…In previous work, the metabolism of [ 14 C]BA by rootless shoots, decapitated roots and intact tomato plants was rapid and complete within 6 h [8,25] . In the current study with excised organs, the metabolism and uptake of this synthetic cytokinin was slower.…”

“…This limitation arises partly from the fact that applied cytokinins are apparently rapidly metabolised, often in a degradative manner [1,6,18,23] . The speed of metabolic assimilation and the range of metabolites produced vary between cytokinins and the plant systems to which they are applied [7,8,12,17,26] . Clarification is needed as to what the metabolic fate of a particular cytokinin in a particular plant or plant organ is, and how the situation changes depending on the method of application employed and the physiological status of the plant .…”

“…In a recent study [8] [8-14 C]BA applied to decapitated tomato roots was metabolised rapidly, partially in a degradative manner but predominantly to ribosylated and glucosylated forms . In a further investigation [25] where [8-14C]BA was applied to rootless shoots and intact tomato plants the results obtained for the roots of the intact and decapitated plants were similar .…”