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The pollen wall protects the sperm while the pollen grain is moving from the anther to the stigma; it protects the vital genetic material from drying out and solar radiation. The pollen grain surface is covered with waxes and proteins, which are held in place by structures called sculpture elements on the surface of the grain.
SEM image of pollen tubes growing from lily pollen grains. A pollen tube is a tubular structure produced by the male gametophyte of seed plants when it germinates. Pollen tube elongation is an integral stage in the plant life cycle.
Diagram of an anther in cross section. 1: Filament; 2: Theca; 3: Connective (the conducting vessels in red); 4: Pollen sac (also called sporangium) The androecium is one of the fertile cycles of flowers. The parts that make up the androecium are called stamens whose function is the generation of male gametophytes or pollen grains.
It begins when a pollen grain adheres to the stigmatic surface of the carpel, the female reproductive structure of angiosperm flowers. The pollen grain begins to germinate (unless a type of self-incompatibility that acts in the stigma occurs in that particular species and is activated), forming a pollen tube that penetrates and extends down ...
Tapetum is important for the nutrition and development of pollen grains and a source of precursors for the pollen coat. [1] The cells are usually bigger and normally have more than one nucleus per cell. As the sporogenous cells undergo mitosis, the nuclei of tapetal cells also divide.
Each theca contains two microsporangia, also known as pollen sacs. The microsporangia produce the microspores, which for seed plants are known as pollen grains. If the pollen sacs are not adjacent, or if they open separately, then no thecae are formed. In Lauraceae, for example, the pollen sacs are spaced apart and open independently.
A pollinium (pl.: pollinia) is a coherent mass of pollen grains in a plant that are the product of only one anther, but are transferred, during pollination, as a single unit. [1] [2] This is regularly seen in plants such as orchids and many species of milkweeds (Asclepiadoideae). Usage of the term differs: in some orchids two masses of pollen ...
Microgametogenesis is the process in plant reproduction where a microgametophyte develops in a pollen grain to the three-celled stage of its development. In flowering plants it occurs with a microspore mother cell inside the anther of the plant.