Effect of 2,3,5‐triiodobenzoic acid on calcium level in sunflower plants and incidence of bract necrosis

Abstract

Experiments were conducted with sunflower (Helianthus annuus, L.) of two inbred lines and eight cultivars grown in the field, in pots in the greenhouse or growth chamber and in nutrient solution. Water solutions of 2,3,5‐triiodobenzoic (TIBA) were sprayed over the top of the plants or added to the nutrient solution TIBA treatment resulted in induction of bract necrosis in some plants, increasing the bract necrosis index with higher TIBA concentration. TIBA had little effect on element concentration in leaves but it decreased the levels of Ca, Mg and B in bracts of plants. At a low TIBA concentration (25 μM) in the nutrient solution, young plants growing in hydroponic solution at a low Ca level, the levels of Ca and Mg of young leaves were decreased but TIBA treatment did not affect significantly the levels of these elements in roots. Since TIBA produces both bract necrosis and lower Ca content in bracts, it is suggested that bract necrosis is a physiological disorder related with lower Ca levels existing in the bracts when plants are grown under stress conditions.