In vitro germination and pollen tube growth of maize (Zea mays L.) pollen. X. Pollen source genotype and gibberellin A3 interactions

Pollen grains from four pollen source genotypes (H55, Oh43, K64 x K55, Ky49 x Ky27) were cultured on an artificial medium (15% sucrose, 0.6% bacto-agar, 0.03% calcium nitrate, 0.01% boric acid) supplemented with four concentrations (0, 5, 25, 100 ppm) of gibberellin A3 (GAj). At 1, 2, and 3 h after inoculation, germination percent and pollen tube length were measured. A highly significant concentration x pollen source genotype interaction for germination percent was obtained. Depending on the pollen source genotype, increasing GAj concentrations either substantially increased or did not alter germination percent. For pollen tube length, a highly significant concentration x pollen source genotype interaction was also obtained. However, depending on the pollen source genotype, increasing GAj concentrations either increased, decreased, or had no effect on pollen tube length. Any stimulatory effect of GA3 on pollen tube length was expressed early in the germination process or between inoculation and one h after inoculation. The results suggested that heterozygosity level could be a contributing factor in the GA3 response and within each pollen source genotype, the effects of GA3 on germination percent and pollen tube length were independent.