Effects of radiation and growth hormones on pollen germination, pollen tube growth and modulation of radiation responses of Pinus kesiya Royle ex Gord

The present investigation deals with the effects of γ-radiation (5-500 Gy) and growth hormones (IAA, GA and kinetin, 10, 25 and 50 ppm) on pollen germination and pollen tube elongation in P. kesiya Royle ex Gord. The effects of combination treatments of γ-rays (500 Gy) and 10 and 50 ppm of growth hormones (IAA, GA and kinetin) were also investigated to find out if radiation effects could be modified by growth hormones. The study revealed that 7.5-40 Gy γ-rays stimulated pollen germination and tube growth, but radiation doses 50-500 Gy were inhibitory. Development of longer pollen tubes was favored by lower doses of γ-rays while higher doses favored development of smaller pollen tubes. 10 ppm of IAA and GA promoted both pollen germination and pollen tube elongation, 25 and 50 ppm of IAA and GA and all the concentrations of kinetin (10-50 ppm) inhibited pollen germination and tube growth. In combination treatments 10 ppm of IAA and GA could ameliorate radiation injury but 25 and 50 ppm of IAA and GA as also 10-50 ppm of kinetin further enhanced radiation damage. Thus in the present study 10 ppm of IAA and GA were radioprotective while 25 and 50 ppm of IAA and GA and 10-50 ppm of kinetin functioned as radiosensitiser.