Effect of nitrogen nutrition and water regime on abscisic, phaseic and dihydrophaseic acid metabolism in leaves of field‐grown kale (Brassica oleracea): Consequences for plant growth and crop yield

Abstract

AbstractRelationships between yield and the accumulation and metabolism of abscisic acid were examined on a kale (Brassica oleracea L) crop grown during a dry summer in the UK under different degrees of water and/or N stress. Measurements were made on both irrigated and unirrigated plants given three rates of N fertiliser, incorporated in up to three different ways in the soil. Growth of the crop was severely restricted in all treatments where irrigation and N fertiliser were withheld.Substantial production and metabolism of abscisic acid occurred in all treatments during growth, with dihydrophaseic acid the major product. Irrigation treatments had no consistent significant effect on the concentrations of either abscisic acid or any of its metabolites, although individual N treatments did show small concentration increases for some of the compounds on the unirrigated plots. By comparison, the N treatments had large effects on the accumulation of abscisic acid and of dihydrophaseic acid (both as free acid and as its glucoside). The concentrations of each of these forms increased significantly with the amount of N applied, the response being modified by a small but significant effect of method of fertiliser incorporation due mainly to its influence on the pattern of N availability during the growing season. However, the concentrations of abscisic acid and some of the metabolites were only correlated with yield in the irrigated treatment.These results suggest that neither the accumulation of abscisic acid nor the ability of the plants to metabolise it were major factors in restricting the growth of kale under either water‐ or N‐stressed conditions in the U K.