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

Abstract

Sedgley, M., 1977. Reduced pollen tube growth and the presence of callose in the pistil of the male floral stage of the avocado. Scientia Hort., 7 : 27--36.Pollen tube growth was studied in the pistil of the male floral stage of the avocado. Selfpollination 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 occured 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.

Effect of low temperatures during flowering on floral cycle and pollen tube growth in nine avocado cultivars

“…The female-stage flowers also overlapped with the male stages of the type B cultivars so that cross pollination could occur. It has been reported previously that pollen tube growth is poorer in male-stage than female-stage avocado flowers (Sedgley, 1977b). The flowers are hermaphrodite, so female and male organs are present in both sex stages, but the female organs have reduced fertility by the time the flower opens in the male stage.…”

Inter-varietal pollen tube growth and ovule penetration in the avocado

“…Pistils wereremoved from the plant 24 h after pollination as preparations from pistils collected up to 48 h after pollination did not differ from those taken at 24 h (SEDGLEY, unpublished data). The single ovule was dissected from each pistil and both ovule and pistil were processed for fluorescence microscopy as described by SEDGLEY (1977b). Preparations were observed using a Zeiss Photomicroscope with reflected light from an HBO 50 mercury vapour lamp and Zeiss 48 77 05 filter combination.…”

Pollen-Pistil Interactions

“…For example, in the avocado, Persea americana, the flower opens twice. The first occasion is the female phase, when pollination of the stigma results in fertilization; in contrast, on the second occasion, anther dehiscence occurs, but if the stigma receives pollen, it mostly fails to germinate and fertilization does not occur (SEDGLEY 1977(SEDGLEY , 1979. Structural changes have been defined in the stigma and style, in terms of starch depletion and callose deposition, which occur in both pollinated and unpollinated pistils, but there has been a marked absence of any evidence for cellular changes to account for the changed stigma response.…”