What is "pollen tube"

Spermatophyta \Sper`ma*toph"y*ta\, n. pl. [NL.; spermato- + Gr. ? plant.] (Bot.) A phylum embracing the highest plants, or those that produce seeds; the seed plants, or flowering plants. They form the most numerous group, including over 120,000 species. In general, the group is characterized by the marked development of the sporophyte, with great differentiation of its parts (root, stem, leaves, flowers, etc.); by the extreme reduction of the gametophyte; and by the development of seeds. All the Spermatophyta are heterosporous; fertilization of the egg cell is either through a

pollen tube emitted by the microspore or (in a few gymnosperms) by spermatozoids.

Note: The phrase ``flowering plants'' is less distinctive than ``seed plants,'' since the conifers, grasses, sedges, oaks, etc., do not produce flowers in the popular sense. For this reason the terms Anthrophyta, Ph[ae]nogamia, and Panerogamia have been superseded as names of the phylum by Spermatophyta.

n. the tube that develops from the wall of a pollen grain and, in seed plants, provides a passage through which the male nuclei reach the embryo sac to effect fertilization

n. slender tubular outgrown from a pollen grain that penetrates the ovule and releases male gametes

A pollen tube is part of the male gametophyte of seed plants. It acts as a conduit to transport the male gamete cells from the pollen grain, either from the stigma (in flowering plants) to the ovules at the base of the pistil, or directly through ovule tissue in some gymnosperms. In maize, this single cell can grow longer than 12 inches to traverse the length of the pistil.

Pollen tubes were first discovered by Giovanni Battista Amici.