Cytokinins in Ecklonia maxima and the effect of seaweed concentrate on plant growth.

Abstract

The endogenous cytokinin levels in the brown alga Ecklonia maxima (OSBECK) PAPENF., and the effect of applications of the seaweed concentrate (Kelpak 66) prepared from this alga, on the growth and yield of various plants was investigated. Tentative identification of the cytokinins present in Ecklonia maxima using High Performance Liquid Chromatography revealed the presence of cis and trans-ribosylzeatin, trans-zeatin, dihydrozeatin and isopentenyladenosine. Seasonal and lunar variations in the endogenous cytokinin levels in fresh and processed Ecklonia maxima material were investigated. Lamina, stipe and holdfast regions of one, two and three metre plants harvested from February 1981 until January 1982 together with samples of processed material from the normal production run, collected over the same period were used in this investigation. Analysis revealed both qualitative and quantitative changes in the cytokinin levels which were closely correlated to the seasonal patterns of growth of Ecklonia maxima. During summer zeatin, ribosylzeatin and their dihydroderivatives were responsible for most of the detected activity. The cytokinin glucosides increased above the levels of free cytokinins during winter. The lunar cycle study of material harvested on a daily basis during April - May 1983 revealed marked fluctuations in the cytokinin levels in the various tissues of two metre plants which were closely correlated with the phases of the moon. Greenhouse trials were conducted to determine the effects of the commercially available seaweed concentrate (Kelpak 66) on the growth of Lycopersicon esculentum MILL. plants in nematode infested soil. Kelpak 66 at a dilution of 1 : 500 improved the growth of treated plants significantly, irrespective of whether it was applied as a foliar spray at regular intervals, or whether the soil in which the plants were grown was flushed once with the diluted seaweed concentrate. Root growth was significantly improved whenever the seaweed concentrate was applied. Associated with this improved root growth was a reduction in the infestation of Meloidogyne incognita (KOIFORD and WHITE) CHITWOOD. Finally, the effect of seaweed concentrate and fertilizer applications on the growth and endogenous cytokinin content of Beta vulgaris L. and Phaseolus vulgaris L. plants was investigated. Seaweed concentrate at a dilution of 1 : 500 applied as a foliar spray improved the growth of treated plants significantly, irrespective of whether it was applied on its own or together with a chemical fertilizer. Root growth and the endogenous cytokinin content of these roots increased with seaweed concentrate application. Increases were also detected in the cytokinin content of fruits of Phaseolus vulgaris plants treated with seaweed concentrate. Associated with this increase in the cytokinin content was an increase in the dry mass of the fruit from treated plants. The significance of these findings and the possible relationship between the endogenous cytokinins present in Ecklonia maxima and the effect of the seaweed concentrate on plant growth is discussed.