成琥珀酸,再运到线粒体,进行T℃CA循环,产生苹果酸。苹果酸运到胞质,转 化成蔗糖,蔗糖是可运输的碳源。 (2) Lipid mobilization. Lipid mobilization requires the involvement of three organelles and the cytoplasm. In the oil body, lipids are hydrolyzed into glycerol and fatty acids fatty acids are then transferred into glyoxysome, where they are converted to succinate: succinate is then moved to mitochondria to be converted to malate via TCA cycle, malate is moved to the cytoplasm, where it is converted to sucrose Sucrose is a readily transportable form of carbon source (3)蛋白质的代谢 有三类蛋白酶参与蛋白质的代谢。蛋白内切酶随机水解蛋白质的肽键产生许 多小肽。蛋白外切酶从蛋白质的C-端或N-端逐个水解氨基酸。肽酶将小肽水解 成氨基酸。种子进入自养过程之前只能利用种子内储存的物质作为能量来源。 Polypeptides Amino acids Carboxypeptidase Endopeptidases Small polypeptides_Peptidases Amino acids 3)Potein mobilization. There are three types of proteinases that are involved in protein mobilization. Endopeptidases cleave proteins randomly on the peptide chain to eld smaller polypeptides Exopeptidases remove amino acids from the c-terminus (carboxypeptidases)or N-terminaus(aminopeptidases)of a pro mo the hydrolyze smaller oligopeptides to amino acids. Seeds keep using their storage reserves until they start autotropic growth 3.植物器官的发育 微管植物器官的形成并不是局限于生命的早期,根茎叶的形成最早出现于胚 胎发生过程,而后在植物整个生命周期中重复出现。这一小节我们将讨论植物根 茎叶的发育 Plant organ formation In vascular plants, organ formation(organogenesis) is not confined to early life and the processes of shoot, root, and leaf formation that occur first in the embryo are repeated throughout the life of the plant. In this section, we will discuss the development of root, shoot and leaf. 根的发育 根有一个流线型的轴,顶端分生组织不产生侧根。侧 根只能从停止生长的成熟区域内部产生。根毛也只能在成 熟区形成,根毛能促进水分和矿质营养的吸收。根毛长形 的丝状细胞大大地增加了根毛与土壤接触的表面积。根从 末端进行生长发育。跟的尖端有四个界限不是十分明显的 发育区域:根冠,分生区,伸长区和成熟区。根冠主要是 保护根尖避免其在土壤中延伸时受到机械损伤。分生区只 产生初生根而不形成次生根。伸长区的细胞进行着快速和 大幅度的延伸。成熟区的细胞进行着细胞的分化。虽然这 四个发育区域只是根的很小一部分,根的生长仅局限于这 个区域。 Root development Roots have a streamlined axis, and no lateral organs are produced by the apical meristem Branch roots arise internally and form only in mature, nongrowing regions成琥珀酸，再运到线粒体, 进行 TCA 循环，产生苹果酸。苹果酸运到胞质，转 化成蔗糖，蔗糖是可运输的碳源。 (2) Lipid mobilization. Lipid mobilization requires the involvement of three organelles and the cytoplasm. In the oil body, lipids are hydrolyzed into glycerol and fatty acids; fatty acids are then transferred into glyoxysome, where they are converted to succinate; succinate is then moved to mitochondria to be converted to malate via TCA cycle, malate is moved to the cytoplasm, where it is converted to sucrose. Sucrose is a readily transportable form of carbon source. （3）蛋白质的代谢 有三类蛋白酶参与蛋白质的代谢。蛋白内切酶随机水解蛋白质的肽键产生许 多小肽。蛋白外切酶从蛋白质的 C-端或 N-端逐个水解氨基酸。肽酶将小肽水解 成氨基酸。种子进入自养过程之前只能利用种子内储存的物质作为能量来源。 (3) Potein mobilization. There are three types of proteinases that are involved in protein mobilization. Endopeptidases cleave proteins randomly on the peptide chain to yield smaller polypeptides. Exopeptidases remove amino acids from the C-terminus (carboxypeptidases) or N-terminaus (aminopeptidases) of a protein. Peptidases hydrolyze smaller oligopeptides to amino acids. Seeds keep using their storage reserves until they start autotropic growth. 3. 植物器官的发育 微管植物器官的形成并不是局限于生命的早期，根茎叶的形成最早出现于胚 胎发生过程，而后在植物整个生命周期中重复出现。这一小节我们将讨论植物根 茎叶的发育。 Plant organ formation In vascular plants, organ formation (organogenesis) is not confined to early life, and the processes of shoot, root, and leaf formation that occur first in the embryo are repeated throughout the life of the plant. In this section, we will discuss the development of root, shoot and leaf. 根的发育 根有一个流线型的轴，顶端分生组织不产生侧根。侧 根只能从停止生长的成熟区域内部产生。根毛也只能在成 熟区形成，根毛能促进水分和矿质营养的吸收。根毛长形 的丝状细胞大大地增加了根毛与土壤接触的表面积。根从 末端进行生长发育。跟的尖端有四个界限不是十分明显的 发育区域：根冠，分生区，伸长区和成熟区。根冠主要是 保护根尖避免其在土壤中延伸时受到机械损伤。分生区只 产生初生根而不形成次生根。伸长区的细胞进行着快速和 大幅度的延伸。成熟区的细胞进行着细胞的分化。虽然这 四个发育区域只是根的很小一部分，根的生长仅局限于这 个区域。 Root development Roots have a streamlined axis, and no lateral organs are produced by the apical meristem. Branch roots arise internally and form only in mature, nongrowing regions