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仙人掌原产热带和亚热带干旱地区,在酷热干燥的环境下,它的叶片变成了体积最小的针刺状,而茎却变成了肉质掌状,代叶片营光合作用。这种变态茎的外层是甲胄模样的栅状组织,且外表皮光滑浓绿,内部富含胶质的海绵组织,是水分和养分的贮存库。气孔隐藏在针刺基部的茸毛之中,白天高温时紧闭气门,不许体内的水分蒸发掉。光合作用所需的二氧化碳,由气孔中吸入。夜晚,敞开气孔呼吸,把二氧化碳与体内的有机酸化合,变成一种特殊的含碳有机酸,贮存
Cactus native tropical and subtropical arid regions, in a hot and dry environment, its leaves into the smallest acupuncture-like, but the stem has become a fleshy palm, leaf photosynthesis. The outer layer of this metamorphic stem is a mesocarp-like gridlike structure, and the outer skin is smooth and green, rich in glial sponge tissue, is a reservoir of water and nutrients. Stomata hidden in the acupuncture at the base of the hair, the high temperature during the day closed the valve, not allowed to evaporate the body of water. Carbon dioxide required for photosynthesis, inhaled by stoma. Night, open stomata breathing, the carbon dioxide and the body of organic acids combined, into a special carbon-containing organic acids, storage