Foreign pollen tube growth in maize after chemical treatments

In maize x sorghum and maize x pearl millet crosses, pollen germination and entry of pollen tube in maize silk were normal. The foreign pollen tube grew only to a few millimeter in length and did not reach embryo sac to allow fertilization. To overcome this barrier, various treatments of chemical viz., 2, 4-D, GA₃ and salicylic acid were tried. Growth hormones mostly had favourable effect on pollen tube growth, whereas, the immunosuppressant had inhibitory effect over the control. The treatment of 2,4-D @ 100 ppm was found to be the best, which improved the foreign pollen tube growth significantly over the control. The sorghum pollen tube growth was better than that of pearl millet. Although certain chemical concentrations improved the tube growth of sorghum and pearl millet, it was not sufficient for the foreign pollen tubes to reach maize embryo sac.