Alpha-Particles and 60Co y-Rays Have Different Biological Effects on Upland Cotton (Gossypium hirsutum L.) Pollen Grains

To compared the irradiation effects by y-rays and alpha-particles on the structure and function of upland cotton pollen grains during pollination, pollen grains from Gossypium hirsutum L. cultivar “Lumian 21†were irradiated by alpha-particles (1, 10, 30, 40 and 100 Gy) and y-rays (20, 30 and 40 Gy). We looked for changes in the ultrastructure of the exine and interior walls of the pollen grains. After germinating the irradiated pollen grains in liquid medium, we looked for changes in germination rate, the number of pollen tubes in styles after pollination and F-actin distribution in the pollen tubes. Alpha-particles penetrated and etched the exine and interior walls of the pollen grains and also damaged the organelles in the pollen grains. More pollen grains were destroyed as the alpha-particles dose increased. y-rays had no effects on the exine walls of the pollen grains but had stronger effects on the interior structure of the pollen grains than those induced by alpha-particle irradiation. The pollen grain germination rate, the number of pollen tubes in the styles and the average length of the pollen tubes in pollen grains treated with y-ray irradiation were decreased and shortened with increased y-rays irradiation dose, compared with that of control. However, under alpha-particle irradiation, these features initially increased at a low level of irradiation (1 Gy) and then decreased as the dose was increased. There was evident damage to F-actin structures in pollen tubes induced by the two kinds of mutagens. The mechanisms underlying the biological effects induced by alpha-particles and y-rays were different. The function and structure of pollen tubes in pollination and fertilization may be affected by the ultrastructure of pollen grains.