Effect of Heat Stress on Calcium Distribution in Pepper Anther Development

Potassium antimonate was used to locate loosely bound calcium in the pepper (Capsicum annuum L.) anther under normal and heat stress environments.(i) In microspore mother cell,a few calcium precipitates deposited on the surface of the cell,few in cytoplasm,and nearly no precipitates in the nucleus.After 12 h 40℃ heat stress,antimonate calcium deposits increased in the cytoplasm and the nucleus,and many emerged on the inner surface of vacuole membrane.After 24 h heat stress,some cells partly deformed,numerous calcium precipitates appeared in the cytoplasm,and deposited on the surface of vacuole membrane and in the vacuoles.(ii) Compared to pollen mother cell,there was a significant increase in calcium deposits quantities on the tetraspore surface and in the cytoplasm.By heat stressing 24 h,precipitates obviously increased in the cytoplasm and nucleus of tetraspore contrast to the control.(iii) In microspore,many calcium precipitates deposited on the baculae,inner surface of plasma membrane,vacuole membrane,with only a few in the cytoplasm and nucleus.After 12 h exposure,precipitates on plasma membrane became abundant,a few in the cytoplasm and the peripheral nucleus,while no precipitates were seen on the vacuole membrane.As for the anthers treated with 24 h-heat stress,precipitates increased on the inner surface of plasma membrane,cytoplasm and nucleus.(iv) In mature pollen,there was a layer of calcium-induced precipitates on the pollen wall,but few in cytoplasm and plasma membrane.No obvious calcium changes occurred on mature pollen by 12 h or 24 h heat exposure.