Inbotany, thestyle of anangiosperm flower is an organ of variable length that connects theovary to thestigma.[1] The style does not contain ovules; these are limited to the region of thegynoecium (female organs of the flower) called the "ovary".
The style is a narrow extension of the ovary, usually pointing upwards, connecting the ovary to thestigmatic papillae. It may be absent in some plants; in this case, it is referred to as asessile stigma. Styles generally resemble more or less long tubes. The style can be open (with few cells occupying the central part, or even none), featuring a central canal that may be filled withmucilage. Alternatively, the style can be closed (completely filled with cells). Most plants withsyncarpous pistils (monocotyledons and someeudicotys) have open styles, whereas many eudicots and grasses have closed (solid) styles containing specialized secretory tissues, which connect the stigma to the center of the ovary. These tissues form a nutrient-rich cord for the growth of the pollen tube.[2]
When thepistil consists of severalcarpels, each of them may have a distinctstylodium (sometimes seen as a pseudo-style[3]) or share a common style. InIris and other species of theIridaceae family, the style divides into three "petaloid branches" (resembling petals), sometimes also called stylodiums,[2] almost at the origin of the style and is called "tribrachiate". These are strips of tissue emerging from the perianth tube above the sepal. The stigma is a ridge or edge on the lower surface of the branch, near the tip of the lobes.[4] Branched styles also appear in the generaDietes,Pardanthopsis, and in most species of the genusMoraea.[5]
InCrocus species, the style is branched into three "branches," forming a tube.[6] Plants of the genusHesperantha have a spread-out branched style. The style can also be lobed rather than branched. Plants of the genusGladiolus have a bilobed style. In the generaFreesia,Lapeirousia,Romulea,Savannosiphon, andWatsonia, the style has bifurcated and curved branches.[7][8]
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May be terminal (apical), subapical, lateral, gynobasic, or subgynobasic. Terminal (apical) style position refers to attachment at the apex of the ovary and is the most common pattern. In the subapical pattern, the style arises to the side slightly below the apex. A lateral style arises from the side of the ovary and is found inRosaceae. The gynobasic style arises from the base of the ovary, or between the ovary lobes and is characteristic ofBoraginaceae. Subgynobasic styles characteriseAllium.[9]
Pollen tubes grow the length of the style to reach theovules, and in some casesself-incompatibility reactions in the style prevent full growth of the pollen tubes. In some species, includingGasteria at least, the pollen tube is directed to themicropyle of the ovule by the style.[10]