Reduced pollen tube growth and the presence of callose in the pistil of the male floral stage of the avocado

Abstract

Pollen tube growth was studied in the pistil of the male floral stage of the avocado. Self-pollination of the male stage occurred but pollen tubes did not reach the ovary. When female and male stages were hand pollinated, fewer pollen tubes were present in the pistil of the male than in the female stage. A tube reached the ovary in only 1 of 110 male stage pistils, as compared with all female stage pistils observed. Flowers pollinated in the female stage were retained on the plant for longer than flowers pollinated in the male stage. Aniline blue-positive and resorcin blue-positive material (callose) was not present in the pistil of flowers in the female stage but occurred in 46% of the aniline blue-stained and 30% of the resorcin blue-stained pistils in the male floral stage. By 42 h after first opening, callose was present in every pistil observed, in association with the cell walls of the stigmatic papillae, the transmitting tissue, the vascular tissue or the cortex and epidermis or a combination of these tissues. Callose occurred earlier in pollinated than in unpollinated pistils, particularly in the transmitting tissue. It is suggested that reduced pollen tube growth in the pistil of the male floral stage of the avocado is associated with the presence of callose.