Cytokinin concentration in relation to mineral nutrition and benzyladenine treatment in Plantago major ssp. pleiosperma

Abstract

Cytokinins in shoot and root tissue were studied in plants of Plantago major L. ssp. pleiosperma (Pilger) grown on a concentrated and on a dilute nutrient solution. Cytokinins of plants transferred from the concentrated to the dilute solution were compared with plants treated similarly but with 10−8M benzyladenine (BA) added to the dilute solution. Cytokinin concentrations were also measured in plants that had been grown throughout on one of the two nutrient solutions. A restricted supply of minerals was correlated with low cytokinin concentrations. Transfer from a concentrated nutrient solution to a dilute solution depressed the cytokinin concentration by 50% within two days of transfer. This decline did not appear if similar plants were supplied with 10−8M BA in the dilute solution. The glucosides were the only major cytokinins enhanced by mineral shortage. This effect of low mineral supply was retarded but not entirely prevented by exogenous BA. The increased synthesis of glucosides in the BA‐treated plants was accompanied by lowered concentrations of free bases and their ribosides and of nucleotides. The sum of cytokinins in BA‐treated plants was thus similar to that in plants grown at the high mineral level. The results are discussed in relation to a possible role of cytokinins in regulating growth responses to changes in mineral nutrition.

Avaliação de plantas transgênicas de Petunia x hybrida contendo o gene Psag12 - ipt cultivadas sob deficiência nutricional.

“…Cytokinin acts stimulating chloroplast development and maintenance (SALISBURY & ROSS, 1992). Similar results have been observed in plants grown under nutritional deficient solution containing cytokinin, where the nutritional deficiency symptoms were alleviated (KUIPER et al, 1989). At the other fertilizer concentrations, P SAG12 -ipt lines had a similar amount of chlorophyll in leaves as wild-type plants ( Table 2).…”

“…Cytokinin exogenous applications alleviate symptoms of restricted mineral supply (KUIPER et al, 1989;HARE et al, 1997). The plant gene that encodes the first enzyme involved in the cytokinin synthesis process has not been identified yet; however, an Agrobacterium tumefaciens gene that encodes the same enzyme was identified and isolated, the isopentenyl transferase (ipt) gene (GAN & AMASINO, 1996).…”

Plants and Hormones: An Ecophysiological View on Timing and Plasticity

“…Root tips, as sites of cytokinin pro duction, react rapidly upon alterations in mineral supply. Work with various plant species showed that a reduction in mineral supply to the root tips induced a decrease in internal cytokinin concentrations in roots, shoots and xylem sap (Kuiper et al 1989 and references herein). The strongest reductions in cyto kinin levels were induced by nitrogen, the effects of phosphate were less pronounced (Coleman et al 1990).…”

Nitrate-Regulated Growth and Cytokinin Responses in Seminal Roots of Barley

“…Although these views do not imply direct roles for plant hormones, it is well known that changes in N availability strongly affect hormone levels, with cytokinins as a prime example. Cytokinin concentrations of roots, shoots, and xylem sap decrease at low N supply (10,12,26,29), and a role for cytokinins from roots in the control of R:T at nutrient limitation has been suggested (12)(13)(14). Exogenous application of cytokinins delay the growth retardation caused by N limitation (12,13,29).…”

“…Cytokinin concentrations of roots, shoots, and xylem sap decrease at low N supply (10,12,26,29), and a role for cytokinins from roots in the control of R:T at nutrient limitation has been suggested (12)(13)(14). Exogenous application of cytokinins delay the growth retardation caused by N limitation (12,13,29). Cytokinins are also important moderators during lateral root initiation, whereas auxin is considered promotive (30).…”