The influence of 2,3,5-triiodobenzoic acid (TIBA) on vegetative and reproductive growth of legumes

Abstract

Trials were conducted in 1968 with two legumes grown under irrigation on a fertile red loam at Redland Bay, near Brisbane, to determine the effects of foliar application of 2,3,5-triiodobenzoic acid (TIBA). TIBA, applied at 20, 40, and 80 g an acre to Phaseolus atropurpureus c.v. Siratro, and 30 and 6Og an acre to Vigna sinensis (cowpea, C.V. Caloona), produced dark-green foliage and distortion of young leaves and stem tips. Elongation of stems and expansion of young leaves present at the time of spraying were stopped. The development of axillary shoots was increased. In general, the effects of TIBA were more severe at higher concentrations, and the plants receiving such treatments were slow to produce new growth. More weed growth occurred in treated plots of Siratro. On Siratro, TIBA reduced the ratio of leaf dry weight to stem dry weight and significantly increased numbers of nodes, axillary branches, inflorescences, and the yield of seed. Flower production was restricted largely to a short concentrated period in treated plots, and canopies were more suitable for seed production. Application of TIBA to cowpea four weeks after planting delayed commencement of flowering by about eight days. Application of 60 g TIBA an acre at early flowering resulted in a 78 per cent increase in inflorescence numbers but no significant increase in seed yield. Some implications of TIBA responses in seed production are discussed.