Several acidic gibberellin-like substances were detected in methanolic extracts from the vege tative shoot and inflorescences of S. sisymbrifolium by thin layer chromatography and two bioassays. Plants with a relatively low but not a deficient content of potassium were shown to contain higher levels of the GA-like substances in both tissues than those having a higher K content. Also qualitative changes in the spectrum of the biologically active substances are affected by varying the K content of the plant. The changes in the GA-like substances are found to correlate with the previously reported morphogenetic effects induced by varying the K content. INTRODUCTION Growth and morphogenesis in several species have been reported to be influenced by changes in the potassium content in a range appreciably above the deficiency level (Haworth and Cleaver, 1963, 1964; Semeniuk, 1964; Wakhloo, 1965a, 6, 1970). In S. sisymbrifolium, which shows deficiency symptoms at foliar K content below 1-5 per cent dry weight, an increase in the K level from 2-7 to 4-6 per cent produces morphogenetic effects including a decrease in flowering which preferentially affects the female sterile flowers characteristic of plants with the lower K content. The K level in this range does not influence the content of other major mineral elements (Ca and N) nor the ratio of organic X to dry weight (Wakhloo, 1975a). The latter suggests that the metabolic changes underlying the morphogenetic effects of the large quantities of K taken up without any evidence of toxic effects do not involve the influence on the levels of carbohydrates and protein known to be produced under conditions of K deficiency (Evans and Sorger, 1966). The higher levels of K in the plant, on the other hand, have been reported to influence significantly the effects of various growth regulators supplied. The evidence that GA3 not only enhances the effects of a low K level, but also simulates the morphogenetic effects in the high-K plants (Wakhloo, 19756), while the growth retardants chlormequat chloride and daminozide additively enhance the effects of a high K content and counteract the effects of a low K level (Wakhloo, 1975c), This content downloaded from 157.55.39.137 on Fri, 27 May 2016 04:28:28 UTC All use subject to http://about.jstor.org/terms WaJchloo—Gibberellin in Solanum sisymbrifolium 795 suggests that higher levels of K may effect processes involving growth regulation. Therefore, an attempt was made to investigate the acidic GA-like activity in the vegetative shoot before flowering, and in the inflorescences in S. sisymbrifolium in relation to the K content of the plant. MATERIALS AND METHODS Plant Material Seedlings of S. sisymbrifolium were raised from seed in soils supplied with two levels of K as reported (Wakhloo, 1975a). At various stages during growth and before extracting for the GA-like substances, samples from the youngest fully developed leaf were analysed for K, Ca, and organic N content as described (Wakhloo, 1975a). The results are given in Table 1. Table 1. Effect of two soil K levels on the content of K, Ca, and organic N in leaves of S. sisymbrifolium Mean of 12 samples from the fourth leaf from 12 plants each. Level of K (mg per 100 g dry soil) Mineral content (g per 100 g dry wt.)