应。有氧呼吸为萌发过程的种子提供能量来源,而有氧呼吸必须有氧气的参与。 因为代谢反应需要酶的参与,而酶必须在一定的温度范围内才有活性。 Environmental requirements for seed germination Appropriate conditions are needed for a seed to germinate: which includes sufficient water, enough oxygen, and appropriate temperature. The uptake of water is an essential, initial step toward germination. Many seeds have thick and hard seed coat. With water uptake, the seed coat is softened so that more oxygen penetrates the seed coat; aerobic respiration of the seed therefore increases. Secondary, after taking up water, the gel-like cytoplasm will be switched to soluble state, so that molecular can move freely, and biochemical reactions can take place. Also, the dehydrated enzymes in the day seeds are rehydrated after imbibition and can be use for biochemical reactions. And also water can assist soluble materials to be transported to the growing seedling. Oxygen is needed for aerobic respiration, which is the source of energy. Termperature is also important, because the metabotic reactions need the involvement or participation of enzymes. Enzymes are only active at a certain temperature range 储藏物质的代谢 种子萌发完成之后,储藏物降解为小分子物质,为种苗的发育提供养分。 (1)淀粉的代谢。淀粉有直链淀粉和支链淀粉两种,直链淀粉由葡萄糖单体通 过α-1,4糖苷键连接而成,支链淀粉则含有α-1,6糖苷键连接的支链。淀粉的降 解需要三类酶的参与。α-淀粉酶是内切酶,随机水解淀粉内的α-1,4糖苷键;脱 支酶特异性地水解连接的支链的α-1,6糖苷键;β-淀粉酶是外切酶,它从淀粉的 非还原端开始,按顺序水解α-1,4糖苷键产生麦芽糖。淀粉在这三种酶的作用下 最终水解为葡萄糖和麦芽糖为种苗的发育提供碳源 000 Storage reserve mobilization After the completion of germination, the storage reserves are degraded into small units to provide nutrition for the young seedling 0 Starch mobilization. There are two types of下/= chains of (1-4)a-linked glucose units; amylopectin branched by (1, 6)o-linkages. Three classes of enzyme are involved in the degradation of starch. a-Amylase is an endohydrolases, which cleaves randomly along the polymeric chain; the branched chains are hydrolyzed by a debranching enzyme, which specifically removes the a-1, 6 linked side chains. Another enzyme B-amylase sequentially removes maltose units from the reduced end of amylose chains. Starch is eventually degraded into glucose and maltose to be transferred to the growing seedling as carbon source (2)脂肪的代谢。脂肪的代谢需要细胞质和三种细胞器的参与。在圆球体 中,脂肪分解成甘油和脂肪酸:脂肪酸进入乙醛酸循环体通过乙醛酸循环途径形应。有氧呼吸为萌发过程的种子提供能量来源，而有氧呼吸必须有氧气的参与。 因为代谢反应需要酶的参与, 而酶必须在一定的温度范围内才有活性。 Environmental requirements for seed germination Appropriate conditions are needed for a seed to germinate: which includes: sufficient water, enough oxygen, and appropriate temperature. The uptake of water is an essential, initial step toward germination. Many seeds have thick and hard seed coat. With water uptake, the seed coat is softened so that more oxygen penetrates the seed coat; aerobic respiration of the seed therefore increases. Secondary, after taking up water, the gel-like cytoplasm will be switched to soluble state, so that molecular can move freely, and biochemical reactions can take place. Also, the dehydrated enzymes in the day seeds are rehydrated after imbibition and can be use for biochemical reactions. And also water can assist soluble materials to be transported to the growing seedling. Oxygen is needed for aerobic respiration, which is the source of energy. Termperature is also important, because the metabotic reactions need the involvement or participation of enzymes. Enzymes are only active at a certain temperature range. 储藏物质的代谢 种子萌发完成之后，储藏物降解为小分子物质，为种苗的发育提供养分。 （1）淀粉的代谢。淀粉有直链淀粉和支链淀粉两种，直链淀粉由葡萄糖单体通 过-1,4 糖苷键连接而成，支链淀粉则含有-1,6 糖苷键连接的支链。淀粉的降 解需要三类酶的参与。-淀粉酶是内切酶，随机水解淀粉内的-1,4 糖苷键；脱 支酶特异性地水解连接的支链的-1,6 糖苷键；-淀粉酶是外切酶，它从淀粉的 非还原端开始，按顺序水解-1,4 糖苷键产生麦芽糖。淀粉在这三种酶的作用下 最 终 水 解 为 葡 萄 糖 和 麦 芽 糖 为 种 苗 的 发 育 提 供 碳 源 。 Storage reserve mobilization After the completion of germination, the storage reserves are degraded into small units to provide nutrition for the young seedling. (1) Starch mobilization. There are two types of starch: amylose and amylopectin; amylose is a long, unbranched chains of (1-4) -linked glucose units; amylopectin is branched by (1,6) -linkages.Three classes of enzyme are involved in the degradation of starch. -Amylase is an endohydrolases, which cleaves randomly along the polymeric chain; the branched chains are hydrolyzed by a debranching enzyme, which specifically removes the -1,6 linked side chains. Another enzyme -amylase sequentially removes maltose units from the reduced end of amylose chains. Starch is eventually degraded into glucose and maltose to be transferred to the growing seedling as carbon source. （2）脂肪的代谢。脂肪的代谢需要细胞质和三种细胞器的参与。在圆球体 中，脂肪分解成甘油和脂肪酸；脂肪酸进入乙醛酸循环体通过乙醛酸循环途径形