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The development of the three celled male gametophyte prior to dehiscing has evolved multiple times and is present in about a third of angiosperm species allowing for faster fertilization after pollination. [20] Once pollination occurs, the tube cell grows in size and if the male gametophyte is only 2 cells at this stage, the single sperm cell ...
However, the parent sporophyte may be monoecious, producing both male and female gametophytes or dioecious, producing gametophytes of one gender only. Seed plant gametophytes are extremely reduced in size; the archegonium consists only of a small number of cells, and the entire male gametophyte may be represented by only two cells. [27]
There are two key differences between mammalian and plant gametogenesis. First, there is no predetermined germline in plants. Male or female gametophyte-producing cells diverge from the reproductive meristem, a totipotent clump of developing cells in the adult plant that creates all the flower's features (both sexual and asexual structures).
In heterosporous seedless vascular plants, modified leaves called microsporophylls bear microsporangia containing many microsporocytes that undergo meiosis, each producing four microspores. Each microspore may develop into a male gametophyte consisting of a somewhat spherical antheridium within the microspore wall.
In the most common type of megagametophyte development in flowering plants (the Polygonum type), three mitotic divisions are involved in producing the gametophyte, which has seven cells, one of which (the central cell) has two nuclei that later merge to make a diploid nucleus.
Microsporangia occur in all vascular plants that have heterosporic life cycles, such as seed plants, spike mosses and the aquatic fern genus Azolla. In gymnosperms and angiosperm anthers , the microsporangia produce microsporocytes, the microspore mother cells , which then produce four microspores through the process of meiosis .
Microgametogenesis is the process of the formation of the male gametophyte. During pollination, the female gametophyte communicates with the pollen tube to ensure that it comes in contact with the ovule. [6] When contact is made, the pollen tube grows through the micropyle opening into a synergid cell, that dies when this occurs.
In order for fertilization to occur, there is rapid tip growth in pollen tubes which delivers the male gametes into the ovules. A pollen tube consists of three different regions: the apex which is the growth region, the subapex which is the transition region, and the shank which acts like normal plant cells with the specific organelles.