什么是菊目
显花植物的一目。仅菊科一科,是显花植物最大的科,一千一百多属,约有两万种,种数之多仅兰科可与相比。其最显着特点是头状花序,每个花序看似一朵花,形状有舌型、辐射型、盘型和圆型等类型。多为虫媒花,许多属(如蝶须属)和某些种可行无融合生殖。果实是瘦果,葵花子实为瘦果。许多菊目植物的瘦果一端有绒毛,靠风散布,其他还有种种散布方式,如瘦果边缘扩展成翅,或瘦果具钩或刺,藉风或动物散布等。菊目的习性和生境要求多样。多为一至多年生草本,生长於温带和亚热带的向阳处。分布范围从北极到南极,从海岸到树木线以上的高山。各种土质均见本目植物,少数水生,还有的生於热带林中。菊目植物种类最多的地区是墨西哥高原及地中海-中东地区。在温带,10%以上的被子植物属菊目,在热带百分比略低。菊目的最大经济价值是用作园林观赏植物,如紫菀属、雏菊属、菊属、大波斯菊属、向日葵属和万寿菊属等。最重要的食用植物是原产欧洲的莴苣和原产美国的向日葵。向日葵种子用作家禽饲料,所提炼的油用於烹调、制沙拉油、人造黄油、肥皂、涂料、清漆,油渣饼可作家畜饲料。某些花可作红色和黄色染料。
Asterales
Family Compositae, one of the largest plant families (also known as Asteraceae, daisy family, and aster family), which contains more than 1,100 genera and almost 20,000 species of herbaceous plants, shrubs, and trees, found throughout the world. Though diverse in habit and habitat, composites tend to grow in sunlit places in temperate and subtropical regions. The family includes many garden ornamentals, including ageratums, asters, chrysanthemums, cosmos, dahlias, marigolds, and zinnias. Some genera include weeds such as dandelion, ragweed, and thistle. Artemisia, artichoke, endive, safflower, salsify, lettuce, and sunflower are important for the products derived from their flowers, seeds, leaves, roots, or tubers. Flower heads in this family are composed of many small flowers (florets) surrounded by bracts. Bell-shaped disk florets form the center of each head; strap-shaped ray florets extend out like petals from the center and are sometimes reflexed (bent back). Some species have flowers with only disk or only ray florets.
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