Poaceae Stock Video Footage


poaceae

Diagram of a typical lawn grass plant. Grasses may be annual or perennial herbs,:10 generally with the following characteristics (the image gallery can be used for reference): The stems of grasses, called culms, are usually cylindrical (more rarely flattened, but not 3-angled) and are hollow, plugged at the nodes, where the leaves are attached. Grass leaves are nearly always alternate and distichous (in one plane), and have parallel veins.:11 Each leaf is differentiated into a lower sheath hugging the stem and a blade with entire (i.e., smooth) margins.:11 The leaf blades of many grasses are hardened with silica phytoliths, which discourage grazing animals some, such as sword grass, are sharp enough to cut human skin. A membranous appendage or fringe of hairs called the ligule lies at the junction between sheath and blade, preventing water or insects from penetrating into the sheath.:11 Flowers of Poaceae are characteristically arranged in spikelets, each having one or more florets.:12 The spikelets are further grouped into panicles or spikes. The part of the spikelet that bears the florets is called the rachilla. A spikelet consists of two (or sometimes fewer) bracts at the base, called glumes, followed by one or more florets.:13 A floret consists of the flower surrounded by two bracts, one external—the lemma—and one internal—the palea. The flowers are usually hermaphroditic—maize being an important exception—and mainly anemophilous or wind-pollinated, al...




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