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Pollen itself is not the male gamete. [4] It is a gametophyte, something that could be considered an entire organism, which then produces the male gamete.Each pollen grain contains vegetative (non-reproductive) cells (only a single cell in most flowering plants but several in other seed plants) and a generative (reproductive) cell.
Pollen tube elongation is an integral stage in the plant life cycle. The pollen tube 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.
Diagram of flower parts. In botany, floral morphology is the study of the diversity of forms and structures presented by the flower, which, by definition, is a branch of limited growth that bears the modified leaves responsible for reproduction and protection of the gametes, called floral pieces.
The tapetum is a specialised layer of nutritive cells found within the anther of flowering plants, located between the sporogenous tissue and the anther wall. Tapetum is important for the nutrition and development of pollen grains and a source of precursors for the pollen coat. [ 1 ]
Plant anatomy or phytotomy is the general term for the study of the internal structure of plants. Originally, it included plant morphology , the description of the physical form and external structure of plants, but since the mid-20th century, plant anatomy has been considered a separate field referring only to internal plant structure.
The tissue between the locules and the cells is called the connective and the parenchyma. Both pollen sacs are separated by the stomium. When the anther is dehiscing, it opens at the stomium. The outer cells of the theca form the epidermis. Below the epidermis, the somatic cells form the tapetum. These support the development of microspores ...
During pollination, pollen grains are physically transferred between plants from the pollen cone to the ovule. Pollen is usually moved by wind or insects. Whole grains enter each ovule through a microscopic gap in the ovule coat called the micropyle. The pollen grains mature further inside the ovule and produce sperm cells.
In some pollen grains, the exine around the apertures is either thicker or thinner. In pores, this border is termed an annulus. Certain flowers have ring-like constrictions at the mouth of the flower, e.g. in Huernia and Aristolochia. 2. A ring of specialized cells on the sporangium. anterior Positioned in front of, toward the apex. Compare distal.