Reproductive development and pollen-stigma interaction in sunflower plants receiving boron deficient and toxic supply

To study the effect of boron deficiency and toxicity on the reproductive development and pollen-stigma interaction in sunflower (Helianthus annuus var. Sungold), plants were raised in sand culture under glass house condition till maturity at 0.033 (deficient), 0.33 (sufficient) and 3.3 (toxic) mg B L-1 supply. The effect of deficiency and toxicity of boron on the number, size and weight of inflorescence, anther size, pollen producing capacity (PPC) of an anther and pollen viability were determined. Enzymes peroxidase, acid phosphatase and esterase and protein were cytochemically localized on the stigmatic surface of disk floret. As compared to control plants (0.33 mg B L-1 supply) development of inflorescence was not only delayed but also poor under boron deficiency and toxicity. Pollen grains produced under boron deficiency and toxicity had reduced size with low viability. Histochemical localization of proteins showed marked decrease in concentration on the stigmatic surface of plants receiving deficient and toxic boron supply. Cytochemical localization of peroxidase enzymes on the stigmatic surface showed increased activity whereas a decrease in acid phosphatase and esterase activity was observed suggesting poor pollen stigma interaction under boron stress condition which might be the cause of poor fertilization.