Marine algal seaweed species are often regarded as an underutilized bioresource, many have been used as a source of food, industrial raw materials, and in therapeutic and botanical applications for centuries. Moreover, seaweed and seaweed-derived products have been widely used as amendments in crop production systems due to the presence of a number of plant growth-stimulating compounds. However, the biostimulatory potential of many of these products has not been fully exploited due to the lack of scientific data on growth factors present in seaweeds and their mode of action in affecting plant growth. This article provides a comprehensive review of the effect of various seaweed species and seaweed products on plant growth and development with an emphasis on the use of this renewable bioresource in sustainable agricultural systems.

Seaweed Extracts as Biostimulants of Plant Growth and Development

Seaweed concentrate prepared fromEcklonia maxima (Osbeck) Papenfuss, when applied as a soil drench, significantly improved the growth of tomato seedlings. Application as a foliar spray had no effect on young plants. In a second experiment SWC-treated plants exhibited early fruit ripening and a total fruit fresh weight increase of 17%. The number of harvested fruit were improved by about 10%. In this instance foliar applied SWC was more beneficial than SWC applied to the soil. The significance of these findings is discussed.

Effect of seaweed concentrate on the establishment and yield of greenhouse tomato plants

9 – Cytokinins and Senescence

Previous investigations have shown the feasibility of increasing pod number on legumes by the application of 6-benzylaminopurine (BA) directly to the raceme. These investigations were designed to determine what reproductive parameter was affected by cytokinin application, and if these applications were overcoming a deficiency in root-produced cytokinins during late flowering. Five individual main stem racemes on greenhouse grown soybeans (Glycine max L. Merr.) were treated with 2 millimolar BA. A single application of BA when pods appeared at 25 to 50% of the proximal floral positions resulted in a 58% increase in pod set due primarily to a 33% reduction in floral abscission. Applications of BA at later intervals also resulted in significant reductions in total abscission. When three applications of BA were imposed on the upper five nodes of field grown soybeans, total pod number and seed weight were significantly increased in this section of the canopy by 27 and 18%, respectively. Throughout the flowering period, root pressure exudate was sampled for the subsequent separation and quantification of zeatin, dihydrozeatin, zeatin riboside, dihydrozeatin riboside, and isopentenyladenine. Total cytokinin flux peaked from 0 to 9 days after flowering began, and then dropped to one-half of this level by 15 days postanthesis. The probability that a flower would initiate a pod was directly related to the concentration of total cytokinins present in the exudate when the flower opened.

The Physiological Basis for Cytokinin Induced Increases in Pod Set in IX93-100 Soybeans.

M. J. Hutton

Papers

An Efficient Column Chromatographic Method for Separating Cytokinins

Cytokinins in Germinating Seeds of Phaseolus vulgaris L. II. Transport and Metabolism of 8[14C]t-Zeatin Applied to the Radicle

Transport and Metabolism of Labelled Zeatin Applied to the Stems of Phaseolus vulgaris at Different Stages of Development

Metabolism of 8[14C]t-Zeatin in Soybean Callus

Cytokinins in Germinating Seeds of Phaseolus vulgaris L. I. Changes in Endogenous Levels Within the Cotyledons