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The stigma, together with the style and ovary (typically called the stigma-style-ovary system) comprises the pistil, which is part of the gynoecium or female reproductive organ of a plant. The stigma itself forms the distal portion of the style, or stylodia, and is composed of stigmatic papillae , the cells of which are receptive to pollen.
The stigma (from Ancient Greek στίγμα, stigma, meaning mark or puncture) is usually found at the tip of the style, the portion of the carpel(s) that receives pollen (male gametophytes). It is commonly sticky or feathery to capture pollen. The word "pistil" comes from Latin pistillum meaning pestle.
Dichogamy: Pollen and stigma of the flower mature at different times to avoid self-pollination. Self-incompatibility: In same plants, the mature pollen fall on the receptive stigma of the same flower but fail to bring about self-pollination. Male sterility: The pollen grains of some plants are not functional. Such plants set seeds only after ...
Some flowers may self-pollinate, producing seed using pollen from a different flower of the same plant, but others have mechanisms to prevent self-pollination and rely on cross-pollination, when pollen is transferred from the anther of one flower to the stigma of another flower on a different individual of the same species.
The stigma plays a role in guiding the sperm to a receptive ovule, in the case of many ovules. [11] Only compatible pollen grains are allowed to grow as determined by signaling with the stigma. In the pollen grain, the generative cell gives rise to the sperm, whereas the vegetative cells have a tube cell that grows the pollen tube.
Diagram of a blooming flower showing the position of the style. In botany, the style of an angiosperm flower is an organ of variable length that connects the ovary to the stigma. [1] The style does not contain ovules; these are limited to the region of the gynoecium (female organs of the flower) called the "ovary".
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The stigma sits at the apex of the column in the front but is pointing downwards after resupination (the rotation by 180 degrees before unfolding of the flower). [ citation needed ] This stigma has the form of a small bowl, the clinandrium , a viscous surface embedding the (generally) single anther.