pollen tube


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Fig. 255 Pollen tube . Section of grain, showing tube.

pollen tube

a slender structure produced from a POLLEN GRAIN after POLLINATION. The tube protrudes from a pore in the EXINE and grows down through the stigma, style and ovary of the CARPEL, entering the ovule usually by the micropyle. See Fig. 255 . Within the tube, the haploid generative nucleus divides by MITOSIS to give two MALE GAMETE NUCLEI which have an important function in the double FERTILIZATION process of higher plants (see EMBRYO SAC). The growth of the tube appears to be controlled by the tube nucleus and there is some evidence that the tube shows negative AEROTROPISM. The stimulus for the original germination of the pollen grain comes from a sugary fluid secreted by the stigma. Sometimes, however, germination is prevented by SELF-INCOMPATIBILITY factors in the stigma cells and pollen grain, which prevent self-pollination in some plants.
References in periodicals archive ?
The entire process, from the deposition of pollen on the micropyle, followed by pollen tube growth and fertilization of the egg, takes considerably longer in cycads and other gymnosperms than in angiosperms.
Self-pollination at bud stage aims to enable self-fertilization before the glycoproteins reach levels that prevent the development of the pollen tube (ROBERTS et al., 1979).
There are six phenotypic classes of pollen tube, five of them mutagen namely, balloon, wavy, branch, swollen, thin and only one is normal namely wildtype [43].
Hoshikawa et al., "Characterization of fruiting and pollen tube growth of apple autotetraploid cultivars showing self-compatibility," Journal of the Japanese Society for Horticultural Science, vol.
The pollen attributes namely pollen viability; pollen size, pollen germination, and pollen tube length were measured with the help of microscope and micrometer.
Though a number of existing teaching activities deal with in vitro pollen tube growth on medium, didactically prepared visualization of pollen tube growth in vivo is more ambitious and usually needs fixed material and advanced equipment (e.g., fluorescence microscopy).
Pollen viability and germination was assessed in vitro and in vivo as well as pollen tube growth rate and velocity within the .floral gynaecium, in order to detect possible malfunctions in the pollination process that could explain disorders such as lack of fruit set and excessive nubbin formation.