植物的生长和发育 Plant growth and development 本章学习目标 理解植物生长、分化和发育的概念 2.掌握植物生长、分化和发育等过程在细胞水平,生化水平和分子水平的调 控机制。 3.理解植物发育过程不同阶段(胚胎发生;种子萌发:根、茎、叶的形成) 细胞水平的特点 4.理解植物运动的类型和机制 Objectives of this chapte 1. Understand the distinction of cell growth, differentiation, and devision 2. Appreciate the principle means of regulations on the processes of growth differentiation, and development at the cellular, biochemical, and molecular 3. Understand celular events that take place during different stages (embryogeneis; seed germination; root, shoot and leaf formation) of plant 4. Understand the categories and mechanisms of plant movements 植物的发育过程贯穿于植物的生命周期;伴随着一系列发育程序精确而有序 地进行。在植物的个体发育过程中,细胞分裂,生长,分化,组织和器官的产生 是自然发展的过程。随着发育的进行,植物最终进入成熟期,开始生殖生长,然 后衰老,死亡。植物生命周期中的这些过程,以及调控这些过程的细胞学,生物 化学,和分子生物学机制构成了植物发育的概念。 The vegetative phase of plant development continues throughout the life of a plant. Plant development requires a precise and highly ordered succession of events Plant cells divide, grow, and differentiate. These ongoing processes generate the plant body with increasingly complex tissues and organs. In the end, these events gve rise to the compex organization of a mature plant that flowers; bears fruit, senesces, and eventually dies. These events, along with their underlying biochemistry and the factors that either impose or modulate an unfailing and orderly progression tho any the life cycle, constitute development 第一节细胞的分裂、生长和分化 在生命周期中,生物的细胞、组织和器官的数目、体积或干重的不可逆增加 过程称为生长。它通过原生质的增加、细胞分裂和细胞体积的扩大来实现,其中 最重要的因素是膨压引起的细胞的膨大。植物的生长是建立在器官生长的基础上 的,而器官的生长的基础,则是细胞分裂、生长和分化。 Cell division, expension and differentiation and enlargement of cell volumn. The largest component of plant growl/ sion y Growth in plants is defined as an irreversible increase in number, volume and weight of cells, tissues and organs. It is caused by increase in plasma, cell divi expansion driven by turgor pressure. During this process, cells increase in volume manyfold. Plant growth is based on organ growth, Organs are generated by cell division and expansion and differentiation 1.细胞分裂 细胞分裂的概念 细胞分裂是一个细胞分裂为两个细胞的过程。分裂前的细胞称母细胞,分裂 后形成的新细胞称子细胞。植物细胞在分裂过程中子细胞之间形成新的细胞壁;
植物的生长和发育 Plant growth and development 本章学习目标: 1. 理解植物生长、分化和发育的概念. 2. 掌握植物生长、分化和发育等过程在细胞水平，生化水平和分子水平的调 控机制。 3. 理解植物发育过程不同阶段（胚胎发生；种子萌发；根、茎、叶的形成） 细胞水平的特点。 4．理解植物运动的类型和机制。 Objectives of this chapter: 1. Understand the distinction of cell growth, differentiation, and devision. 2. Appreciate the principle means of regulations on the processes of growth, differentiation, and development at the cellular, biochemical, and molecular levels. 3. Understand celular events that take place during different stages (embryogeneis; seed germination; root, shoot and leaf formation) of plant development. 4. Understand the categories and mechanisms of plant movements. 植物的发育过程贯穿于植物的生命周期；伴随着一系列发育程序精确而有序 地进行。在植物的个体发育过程中，细胞分裂，生长，分化，组织和器官的产生 是自然发展的过程。随着发育的进行，植物最终进入成熟期，开始生殖生长，然 后衰老，死亡。植物生命周期中的这些过程，以及调控这些过程的细胞学，生物 化学，和分子生物学机制构成了植物发育的概念。 The vegetative phase of plant development continues throughout the life of a plant. Plant development requires a precise and highly ordered succession of events. Plant cells divide, grow, and differentiate. These ongoing processes generate the plant body with increasingly complex tissues and organs. In the end, these events gve rise to the compex organization of a mature plant that flowers; bears fruit, senesces, and eventually dies. These events, along with their underlying biochemistry and the any factors that either impose or modulate an unfailing and orderly progression through the life cycle, constitute development. 第一节 细胞的分裂、生长和分化 在生命周期中，生物的细胞、组织和器官的数目、体积或干重的不可逆增加 过程称为生长。它通过原生质的增加、细胞分裂和细胞体积的扩大来实现, 其中 最重要的因素是膨压引起的细胞的膨大。植物的生长是建立在器官生长的基础上 的，而器官的生长的基础，则是细胞分裂、生长和分化。 Cell division, expension and differentiation Growth in plants is defined as an irreversible increase in number, volume and dry weight of cells, tissues and organs. It is caused by increase in plasma, cell division and enlargement of cell volumn. The largest component of plant growth is cell expansion driven by turgor pressure. During this process, cells increase in volume manyfold. Plant growth is based on organ growth, Organs are generated by cell division and expansion and differentiation. 1．细胞分裂 细胞分裂的概念 细胞分裂是一个细胞分裂为两个细胞的过程。分裂前的细胞称母细胞，分裂 后形成的新细胞称子细胞。植物细胞在分裂过程中子细胞之间形成新的细胞壁；
最后,母细胞一分为二,形成两个子细胞。子细胞获得一套母细胞复制的基因组。 细胞分裂周期是分裂细胞的生命周期,包括分裂期和分裂间期。分裂期在细胞周 期中只是一个相对很短的过程,它与相对长很多的分裂间期交替进行。分裂间期 分为三个阶段:G1期,S期,和G2期.在这三个阶段,细胞通过蛋白质的合成 和细胞器的产生进行生长。染色体只有在S期复制。细胞分裂周期中的所有时期 都受到十分有序的调控,这些调控主要通过蛋白质的作用实现 Definition of cell division Cell division is the process by which a parent cell divides into two or more daughter cells, each with a replica of the original genome. In plant cells, the daughter cells will construct a new dividing cell wall between each other. Eventually, the parent cell will be split in half, giving rise to two daughter cells. The daughter cell is capable of dividing again. The cell cycle is the life cycle of a dividing cell. It includes Interphase and the Mitotic phase. The mitotic phase is a relatively short period of the cell cycle. It alternates with the much longer interphase, where the cell prepares itself for cell division. Interphase is divided into three phases: Gl(first gap), S(synthesis) and G2(second gap)(Figure ) During all three phases, the cell grows by producing proteins and cytoplasmic organelles. However, chromosomes are replicated only during the s phase. All these phases in the interphase are highly regulated, mainly via proteins. The phases follow one another in strict order and there are"checkpoints that give the cell the cues to proceed from one phase to another 细胞周期不同阶段的生化变化 染色体DNA在G1期通过形成复制前复合体为S期的DNA复制作准备。DNA 在S期完成复制,G2期为有丝分裂做准备。G1的早期是细胞周期调控的关键时 间点,细胞一旦经过在该时间点就将不可逆地进入DNA合成和细胞分裂周期的 程序。细胞周期完成后,细胞可能进入下一轮的细胞周期,也可能离开细胞周期 进行分化。和动物细胞不同,植物细胞既可以在DNA复制前(G1期),也可以在 DNA复制后(G2期)离开细胞周期。所以,动物细胞一般都是二倍体,而植物 细胞经常出现四倍体的情况,如果再进行一轮只有DNA复制而不进行有丝分裂 的细胞周期,还会产生多倍体细胞 Biochemical changes in each phase of the Cell Cycle During Gl phase, nuclear DNA is prepared for replication by the assembly of a prereplication complex. DNA is replicated during the s phase, and g2 cells prepare for mitosis. Early in Gl of the cell cycle is a key regulatory point, when it is irreversibly committed to initiating DNA synthesis and completing the cell cycle After the cell has completed mitosis, it may initiate another complete cycle, or it may leave the cell cycle and differentiate. Unlike animal cells, plant cells can leave the cell division cycle either before or after replicating their DNA (i.e, during Gl or G2).As a consequence, whereas most animal cells are diploid (having two sets of chromosomes), plant cells frequently are tetraploid(having four sets of chromosomes) or even polyploidy(having many sets of chromosomes), after going through additional cycles of nuclear DNA replication without mitosis 蛋白激酶对细胞周期的调控 控制细胞周期的关键酶是依赖于细胞周期蛋白的蛋白激酶CDK)。蛋白激酶 是利用ATP是蛋白质磷酸化的酶。细胞有几种蛋白激酶,它们依靠细胞周期蛋白 ( cyclin)的调节亚基去活化细胞周期的不同时期。蛋白质CDK活性的调控在由G- 到-S和由G2-到-M期两个转变过程起了关键的作用。CDK的活性有很多调控方 式,其中两条最主要的调节途径是:(1) cyclin的合成与降解;(2)CDK内关键
最后，母细胞一分为二，形成两个子细胞。子细胞获得一套母细胞复制的基因组。 细胞分裂周期是分裂细胞的生命周期，包括分裂期和分裂间期。分裂期在细胞周 期中只是一个相对很短的过程，它与相对长很多的分裂间期交替进行。分裂间期 分为三个阶段：G1期, S 期, 和 G2 期. 在这三个阶段，细胞通过蛋白质的合成 和细胞器的产生进行生长。染色体只有在 S 期复制。细胞分裂周期中的所有时期 都受到十分有序的调控，这些调控主要通过蛋白质的作用实现。 Definition of cell division Cell division is the process by which a parent cell divides into two or more daughter cells, each with a replica of the original genome. In plant cells, the daughter cells will construct a new dividing cell wall between each other. Eventually, the parent cell will be split in half, giving rise to two daughter cells. The daughter cell is capable of dividing again. The cell cycle is the life cycle of a dividing cell. It includes Interphase and the Mitotic phase. The mitotic phase is a relatively short period of the cell cycle. It alternates with the much longer interphase, where the cell prepares itself for cell division. Interphase is divided into three phases: G1 (first gap), S (synthesis), and G2 (second gap) （Figure）. During all three phases, the cell grows by producing proteins and cytoplasmic organelles. However, chromosomes are replicated only during the S phase. All these phases in the interphase are highly regulated, mainly via proteins. The phases follow one another in strict order and there are "checkpoints" that give the cell the cues to proceed from one phase to another. 细胞周期不同阶段的生化变化 染色体DNA在G1期通过形成复制前复合体为S期的DNA复制作准备。DNA 在S期完成复制， G2 期为有丝分裂做准备。G1的早期是细胞周期调控的关键时 间点，细胞一旦经过在该时间点就将不可逆地进入DNA合成和细胞分裂周期的 程序。细胞周期完成后，细胞可能进入下一轮的细胞周期，也可能离开细胞周期 进行分化。和动物细胞不同，植物细胞既可以在DNA复制前（G1期），也可以在 DNA复制后（G2期）离开细胞周期。所以，动物细胞一般都是二倍体，而植物 细胞经常出现四倍体的情况，如果再进行一轮只有DNA复制而不进行有丝分裂 的细胞周期，还会产生多倍体细胞。 Biochemical changes in each phase of the Cell Cycle During G1 phase, nuclear DNA is prepared for replication by the assembly of a prereplication complex. DNA is replicated during the S phase, and G2 cells prepare for mitosis. Early in G1 of the cell cycle is a key regulatory point, when it is irreversibly committed to initiating DNA synthesis and completing the cell cycle. After the cell has completed mitosis, it may initiate another complete cycle, or it may leave the cell cycle and differentiate. Unlike animal cells, plant cells can leave the cell division cycle either before or after replicating their DNA (i.e., during G1 or G2). As a consequence, whereas most animal cells are diploid (having two sets of chromosomes), plant cells frequently are tetraploid (having four sets of chromosomes), or even polyploidy (having many sets of chromosomes), after going through additional cycles of nuclear DNA replication without mitosis. 蛋白激酶对细胞周期的调控 控制细胞周期的关键酶是依赖于细胞周期蛋白的蛋白激酶(CDK)。蛋白激酶 是利用ATP是蛋白质磷酸化的酶。细胞有几种蛋白激酶，它们依靠细胞周期蛋白 (cyclin)的调节亚基去活化细胞周期的不同时期。蛋白质CDK活性的调控在由G1- 到-S和由G2-到-M期两个转变过程起了关键的作用。CDK的活性有很多调控方 式，其中两条最主要的调节途径是：（1）cyclin的合成与降解；（2）CDK内关键
氨基酸残基的磷酸化和区磷酸化。然后被降解。CDKs只有与 cyclin结合才具有活 性。大部分的 cyclin能很快转换。 Cyclin在细胞周期的特殊转变位点被合成,然后 被降解。由Gl-到-S需要 Gl cyclins来激活CDKs:由G2-到M需要G2 cyclins来激 活CDKs。CDKs有两个酪氨酸的磷酸化位点:其中一个引起该酶的活化,另一个 引起该酶的失活。激活和抑制CDKs酶活的磷酸化均由特异的蛋白激酶催化。与 CDKs磷酸化类似,蛋白磷酸酶能使CDKs去磷酸化,磷酸所处的位置决定去磷酸 化使CDKs激活还是失活。CDKs的磷酸化和去磷酸化是控制细胞周期进程的重要 调控机制。 Regulation of cell cycle by protein kinases The key enzymes that control the transitions between the different states of the cell cycle are the cyclin-dependent protein kinases, or CDKs(Figure). Protein kinases are enzymes that phosphorylate proteins using ATP. Cells use several protein kinases which activate different phases of the cell cycle depending on regulatory subunits called cyclins for their activities. The regulated activity of CDKs is essential for the transitions from Gl to S and from g2 to M. cdk activity can be regulated in various ways, but two of the most important mechanisms are(1)cyclin synthesis and destruction and (2)the phosphorylation and dephosphorylation of key amino acid residues within the CDK protein CDKs are inactive unless they are associated with a cyclin. Most cyclins turn over rapidly. They are synthesized and then actively degraded at specific points in the cell cycle. The transition from Gl to S requires G1 cyclins to activate the CDKs; the transition from G2 to mitosis requires another set of cylins(known as mitotic cyclins)to activate CDKs(see Figure). CDKs possess two tyrosine phosphorylation sites: One causes activation of the enzyme, the other causes inactivation. Specific kinases carry out both the stimulatory and the inhibitory phosphorylations. Similarly, protein phosphatases can remove phosphate from CDKs, either stimulating or inhibiting their activity, depending on the position of the phosphate. The addition or removal of phosphate groups from CDKs is highly regulated and an important mechanism for the control of cell cycle progression(see Figure) 激素对细胞分裂的调控 激素能显著影响细胞分裂,细胞分裂素对维持分生组织的分裂具有重要的作 用。GA能促进G1到S的过程,CTK能促进S期中DNA的合成,所以CTK和 GA都对细胞分裂起促进作用 Regulation of cell cycle by hormones Certain hormones can affect cell cycle significantly. Ga plays important role in maintaining cell division capability of meristem. GA stimulates the process from Gl to S; CTK promotes DNA synthesis during S phase, both CTK and Ga stimulate cell division 2.细胞生长 细胞生长的概念 体积的增大是细胞生长的主要因素。而水分是细胞体积构成的主要成份,所 以细胞必须吸水才能使体积增大。细胞体积增大的促进因素是细胞吸水。细胞的 水势主要是通过膨压的变化,也就是不断增大的原生质对细胞壁产生的压力的变 化来调节的。细胞能产生很大的膨压。为了抵拒这种压力,细胞壁必须足够坚固。 细胞体积增大最关键的限制因素是由细胞壁的强度和刚性。所以,细胞壁的存在 阻碍着细胞体积的增长。克服这种阻碍有两种方式:一种是增加膨压,因为只有
氨基酸残基的磷酸化和区磷酸化。然后被降解。CDKs只有与cyclin结合才具有活 性。大部分的cyclin能很快转换。Cyclin在细胞周期的特殊转变位点被合成，然后 被降解。由G1-到-S需要G1 cyclins来激活CDKs；由G2-到-M需要G2 cyclins来激 活CDKs。CDKs有两个酪氨酸的磷酸化位点：其中一个引起该酶的活化，另一个 引起该酶的失活。激活和抑制CDKs酶活的磷酸化均由特异的蛋白激酶催化。与 CDKs磷酸化类似，蛋白磷酸酶能使CDKs去磷酸化，磷酸所处的位置决定去磷酸 化使CDKs激活还是失活。CDKs的磷酸化和去磷酸化是控制细胞周期进程的重要 调控机制。 Regulation of cell cycle by protein kinases The key enzymes that control the transitions between the different states of the cell cycle are the cyclin-dependent protein kinases, or CDKs (Figure). Protein kinases are enzymes that phosphorylate proteins using ATP. Cells use several protein kinases; which activate different phases of the cell cycle depending on regulatory subunits called cyclins for their activities. The regulated activity of CDKs is essential for the transitions from G1 to S and from G2 to M. CDK activity can be regulated in various ways, but two of the most important mechanisms are (1) cyclin synthesis and destruction and (2) the phosphorylation and dephosphorylation of key amino acid residues within the CDK protein. CDKs are inactive unless they are associated with a cyclin. Most cyclins turn over rapidly. They are synthesized and then actively degraded at specific points in the cell cycle. The transition from G1 to S requires G1 cyclins to activate the CDKs; the transition from G2 to mitosis requires another set of cylins (known as mitotic cyclins) to activate CDKs (see Figure). CDKs possess two tyrosine phosphorylation sites: One causes activation of the enzyme; the other causes inactivation. Specific kinases carry out both the stimulatory and the inhibitory phosphorylations. Similarly, protein phosphatases can remove phosphate from CDKs, either stimulating or inhibiting their activity, depending on the position of the phosphate. The addition or removal of phosphate groups from CDKs is highly regulated and an important mechanism for the control of cell cycle progression (see Figure). 激素对细胞分裂的调控 激素能显著影响细胞分裂，细胞分裂素对维持分生组织的分裂具有重要的作 用。GA 能促进 G1到 S 的过程，CTK 能促进 S 期中 DNA 的合成，所以 CTK 和 GA 都对细胞分裂起促进作用。 Regulation of cell cycle by hormones Certain hormones can affect cell cycle significantly. GA plays important role in maintaining cell division capability of meristem. GA stimulates the process from G1 to S; CTK promotes DNA synthesis during S phase, both CTK and GA stimulate cell division. 2. 细胞生长 细胞生长的概念 体积的增大是细胞生长的主要因素。而水分是细胞体积构成的主要成份, 所 以细胞必须吸水才能使体积增大。细胞体积增大的促进因素是细胞吸水。细胞的 水势主要是通过膨压的变化，也就是不断增大的原生质对细胞壁产生的压力的变 化来调节的。细胞能产生很大的膨压。为了抵拒这种压力，细胞壁必须足够坚固。 细胞体积增大最关键的限制因素是由细胞壁的强度和刚性。所以，细胞壁的存在 阻碍着细胞体积的增长。克服这种阻碍有两种方式：一种是增加膨压，因为只有
当膨压超过细胞壁的抗张程度时细胞才能生长;另一种是让细胞壁松弛,减弱壁 的强度。 Cell growth Definition of cell growth An irreversible increase in volumn is the main factor of cell growth. Since most of the volumn of any cell is water, it follows that for a cell to increase its volumn it must take up water. The driving force for cell enlargement is water uptake. Water potential of a cell is regulated primarily by changes in turgor, the pressure generated by the expanding protoplast against the cell wall. Turgor pressures developed in cell can be quite large. In order to resist such pressures, cel walls must be very strong and rigid. The critical restriction on the capacity of plant cells to grow is imposed by the strength and rigidity of the cell wall. Thus, in order for a cell to increase in size, turger pressure has to increase until it exceeds the resistance of cell wall; another way for a cell to increase in size is to weaken the strength and rigidity of the cell wall 细胞生长方向的调控 细胞生长过程,使得松弛的细胞壁得以延伸的原动力是膨压。膨压产生的向 外的张力是均等地向各个方向的。如果没有壁的束缚,在膨压的作用下,细胞应 向各个方向均衡地生长,呈射线状扩展成球状。然而,植物细胞都有各自的形态, 因为细胞壁的结构,尤其是微纤丝在细胞壁中的取向决定细胞的生长方向(图) 微纤丝在细胞壁中的取向又是由微管在质膜内侧面的排列方向控制。有些激素 (例如:赤霉素,乙烯等)和一些外界因素因能影响微管在质膜内侧的排列方向, 从而影响微纤丝在细胞壁中的沉积方向,进而影响到细胞的伸长和植株的形态。 Regulation of cell growth directionality During growth, the loosened cell wall is extended by physical forces generated from cell turgor pressure. Turgor pressure creates an outward-directed force, equal in all directions. If there is no restriction of the cell wall, the cell would grow equally in all directions, expanding radially to generate a sphere. However, plant cells have all different shapes, because the structure of the cell wall--in particular, the orientatio of cellulose microfibril orientation determines growth directionality of cells. The orientation of newly deposited cellulose microfibrils is determined by the orientation of microtubules in the cortical cytoplasm. Certain hormones, (i.e, GA and ethylene and some environmental factors can influence the orientation of microtubules in cortical cytoplasm; therefore influence the direction of orientation of newly de cellulose microfibrils, and eventually affect cell expansion and plant shape 生长素的酸生长学说 生长中的细胞壁的一个重要特性是在酸性环境下延伸速度比中性环境下要 快很多,这种形象被称为酸生长。根据酸生长学说,生长素的功能之一是能通过 激活质膜上的ATP酶诱导细胞可将细胞质中的H分泌到细胞壁中。生长素诱导 的质子排出有两种可能的机制:激活已经存在的质子泵,或促进质膜上的ATP 酶的合成。而低pH值一方面通过激活膨胀素降低壁中多糖间氢键的结合程度 另一方面通过提髙壁中适于酸化条件的水解酶的活性,使壁发生松驰。壁一旦松 驰,在膨压的作用下,细胞就得以伸展。在质子排出的同时,长时间的酸生长效 应还包括溶质的吸收和一些新合成的成壁物质会填充于壁中。 he acid growth hypothesis for auxin action An important characteristic of growing cell walls is that they extend much faster at acidic pH than at neutral pH. This phenomenon is called acid growth. According to
当膨压超过细胞壁的抗张程度时细胞才能生长；另一种是让细胞壁松弛，减弱壁 的强度。 Cell growth Definition of cell growth An irreversible increase in volumn is the main factor of cell growth. Since most of the volumn of any cell is water, it follows that for a cell to increase its volumn it must take up water. The driving force for cell enlargement is water uptake. Water potential of a cell is regulated primarily by changes in turgor, the pressure generated by the expanding protoplast against the cell wall. Turgor pressures developed in cells can be quite large. In order to resist such pressures, cel walls must be very strong and rigid. The critical restriction on the capacity of plant cells to grow is imposed by the strength and rigidity of the cell wall. Thus, in order for a cell to increase in size, turger pressure has to increase until it exceeds the resistance of cell wall; another way for a cell to increase in size is to weaken the strength and rigidity of the cell wall. 细胞生长方向的调控 细胞生长过程，使得松弛的细胞壁得以延伸的原动力是膨压。膨压产生的向 外的张力是均等地向各个方向的。如果没有壁的束缚，在膨压的作用下，细胞应 向各个方向均衡地生长，呈射线状扩展成球状。然而，植物细胞都有各自的形态， 因为细胞壁的结构，尤其是微纤丝在细胞壁中的取向决定细胞的生长方向(图)。 微纤丝在细胞壁中的取向又是由微管在质膜内侧面的排列方向控制。有些激素 （例如：赤霉素，乙烯等）和一些外界因素因能影响微管在质膜内侧的排列方向， 从而影响微纤丝在细胞壁中的沉积方向，进而影响到细胞的伸长和植株的形态。 Regulation of cell growth directionality During growth, the loosened cell wall is extended by physical forces generated from cell turgor pressure. Turgor pressure creates an outward-directed force, equal in all directions. If there is no restriction of the cell wall, the cell would grow equally in all directions, expanding radially to generate a sphere. However, plant cells have all different shapes, because the structure of the cell wall—in particular, the orientation of cellulose microfibril orientation determines growth directionality of cells. The orientation of newly deposited cellulose microfibrils is determined by the orientation of microtubules in the cortical cytoplasm. Certain hormones, (i.e., GA and ethylene) and some environmental factors can influence the orientation of microtubules in the cortical cytoplasm; therefore influence the direction of orientation of newly deposited cellulose microfibrils; and eventually affect cell expansion and plant shape. 生长素的酸生长学说 生长中的细胞壁的一个重要特性是在酸性环境下延伸速度比中性环境下要 快很多，这种形象被称为酸生长。根据酸生长学说，生长素的功能之一是能通过 激活质膜上的 ATP 酶诱导细胞可将细胞质中的 H +分泌到细胞壁中。生长素诱导 的质子排出有两种可能的机制：激活已经存在的质子泵，或促进质膜上的 ATP 酶的合成。而低 pH 值一方面通过激活膨胀素降低壁中多糖间氢键的结合程度， 另一方面通过提高壁中适于酸化条件的水解酶的活性，使壁发生松驰。壁一旦松 驰，在膨压的作用下，细胞就得以伸展。在质子排出的同时，长时间的酸生长效 应还包括溶质的吸收和一些新合成的成壁物质会填充于壁中。 The acid growth hypothesis for auxin action An important characteristic of growing cell walls is that they extend much faster at acidic pH than at neutral pH. This phenomenon is called acid growth. According to
the acid growth hypothesis, one of the important actions of auxin is to induce cells to transport protons into the cell wall by stimulating the plasma membrane H+-ATPase Two mechanisms have been proposed for auxin-induced proton extrusion: direct activation of the proton pump and enhanced synthesis of the plasma membrane H+-ATPase. The ability of protons to cause cell wall loosening is mediated by a class of proteins called expansins. Expansins loosen the cell wall by breaking hydrogen bonds between the polysaccharide components of the wall. With loosened cell wall cell is able to extend under turger pressure. In addition to proton extrusion, long-term auxin-induced growth involves the uptake of solutes and the synthesis and deposition of polysaccharides 赤霉素促进细胞壁的伸展 赤霉素和生长素都能影响细胞壁的特性。生长素的作用主要是通过诱导细胞 壁的酸化引起细胞壁松弛。然而赤霉素的作用机制和生长素的不同。关于赤霉素 促进细胞伸长的机制有多种假说,例如:有实验证据显示赤霉素通过提高木葡聚 糖内转糖基酶的活性促进细胞伸长。木葡聚糖内转糖基酶的功能可能是促进膨胀 素进入细胞壁,该酶还能引起细胞壁成分的重新排列。赤霉素诱导的细胞伸长过 程可能需要膨胀素和木葡聚糖内转糖基酶的共同参与。 Gibberellins Enhance Cell Wall Extensibility Both gibberellin and auxin seem to exert their effects by modifying cell wall properties. In the case of auxin, cell wall loosening appears to be mediated in part by cell wall acidification. However, this does not appear to be the mechanism of ibberellin action. Various suggestions have been made regarding the mechanism of gibberellin-stimulated cell elongation. For example, there is evidence that Ga stimulate the enzyme activity of xyloglucan endotransglycosylase (XET). The function of XET may be to facilitate the penetration of expansins into the cell wall XET is also involved in the reorganization of cell wall. Both expansins and XET may be required for gibberellin-stimulated cell elongation 3细胞分化 细胞分化的概念 从一种同质的细胞类型转变成形态结构和功能与原来不相同的异质细胞类 型的过程称为分化。例如:从受精卵细胞分裂转变成胚的过程就是分化。植物细 胞的分化常常是可逆的特别是当已经完成分化过程的细胞处于离体状态,在组 织培养的条件下,细胞就会发生脱分化(失去其分化后的特性,重新开始细胞分 裂。如果给脱分化的细胞提供合适的养分和激素,这些细胞能发育成一株完整的 植株 Cell differentiation Definition of cell differentiation Cell Differentiation is the process by which a cell acquires metabolic, structural, and functional properties that are distinct from those of its progenitor cell. fe example: Embryogenesis that transforms a single-celled zygote into a multicellular, microscopic, embryonic plant; the development of meristematic cells to tracheary elements; are processes of cell differentiation. Differentiated plant cells retain all the genetic information required for the development of a complete plant, a property termed totipotency. This totipotency property can be demonstrated by cell dedifferentiation. Plants cell differentiation is frequently reversible, particularly when differentiated cells are removed from the plant and placed in tissue culture. Under these conditions, cells dedifferentiate (i.e, lose their differentiated characteristics)
the acid growth hypothesis, one of the important actions of auxin is to induce cells to transport protons into the cell wall by stimulating the plasma membrane H+-ATPase. Two mechanisms have been proposed for auxin-induced proton extrusion: direct activation of the proton pump and enhanced synthesis of the plasma membrane H+-ATPase. The ability of protons to cause cell wall loosening is mediated by a class of proteins called expansins. Expansins loosen the cell wall by breaking hydrogen bonds between the polysaccharide components of the wall. With loosened cell wall, cell is able to extend under turger pressure. In addition to proton extrusion, long-term auxin-induced growth involves the uptake of solutes and the synthesis and deposition of polysaccharides. 赤霉素促进细胞壁的伸展 赤霉素和生长素都能影响细胞壁的特性。生长素的作用主要是通过诱导细胞 壁的酸化引起细胞壁松弛。然而赤霉素的作用机制和生长素的不同。关于赤霉素 促进细胞伸长的机制有多种假说，例如：有实验证据显示赤霉素通过提高木葡聚 糖内转糖基酶的活性促进细胞伸长。木葡聚糖内转糖基酶的功能可能是促进膨胀 素进入细胞壁，该酶还能引起细胞壁成分的重新排列。赤霉素诱导的细胞伸长过 程可能需要膨胀素和木葡聚糖内转糖基酶的共同参与。 Gibberellins Enhance Cell Wall Extensibility Both gibberellin and auxin seem to exert their effects by modifying cell wall properties. In the case of auxin, cell wall loosening appears to be mediated in part by cell wall acidification. However, this does not appear to be the mechanism of gibberellin action. Various suggestions have been made regarding the mechanism of gibberellin-stimulated cell elongation. For example, there is evidence that GA stimiulate the enzyme activity of xyloglucan endotransglycosylase (XET). The function of XET may be to facilitate the penetration of expansins into the cell wall； XET is also involved in the reorganization of cell wall. Both expansins and XET may be required for gibberellin-stimulated cell elongation 3 细胞分化 细胞分化的概念 从一种同质的细胞类型转变成形态结构和功能与原来不相同的异质细胞类 型的过程称为分化。例如：从受精卵细胞分裂转变成胚的过程就是分化。植物细 胞的分化常常是可逆的,特别是当已经完成分化过程的细胞处于离体状态, 在组 织培养的条件下, 细胞就会发生脱分化(失去其分化后的特性), 重新开始细胞分 裂。如果给脱分化的细胞提供合适的养分和激素, 这些细胞能发育成一株完整的 植株。 Cell Differentiation Definition of cell differentiation Cell Differentiation is the process by which a cell acquires metabolic, structural, and functional properties that are distinct from those of its progenitor cell. For example: Embryogenesis that transforms a single-celled zygote into a multicellular, microscopic, embryonic plant; the development of meristematic cells to tracheary elements; are processes of cell differentiation. Differentiated plant cells retain all the genetic information required for the development of a complete plant, a property termed totipotency. This totipotency property can be demonstrated by cell dedifferentiation. Plants cell differentiation is frequently reversible, particularly when differentiated cells are removed from the plant and placed in tissue culture. Under these conditions, cells dedifferentiate (i.e., lose their differentiated characteristics)
reinitiate cell division, and in some cases, when provided with the appropriate nutrients and hormones, even regenerate whole plants 极性是细胞分化的前提 极性是指细胞(也可指器官和植株)内不同区域在形态结构和生理生化上存 在差异的现象。极性的建立会引发不均等分裂,使两个子细胞的大小和内含物不 等,由此引起分裂细胞的分化。例如:胚胎发生在初期就建立了轴向极性。受精 卵在第一次分裂前已经极化。受精卵顶端含有较浓的细胞质成分,而基端主要含 个大的中央液泡。第一次分裂产生的两个细胞朝着不同的方向进行分化 Cell Polarity is a prerequisite of cell differentiation Cell Polarity refers to spatial differences in the shape, structure, and function of cells. Polarity establishment cause asymmetric cell division, thus the two daughter cells have differences in size and cell content which leads to the differentiation of the daughter cells. For example: Axial polarity is established very early in embryogenesi The zygote becomes polarized before its first division. The apical end of the zygote is densely cytoplasmic, but the basal half of the cell contains a large central vacuole The first division of the zygote creates two cells that carry out differentiation toward different directions 细胞分化受环境条件诱导 光照、温度、营养、pH、离子和电势等环境条件都能影响细胞的分化。如 短日照处理,可诱导苍耳提前开花;低温处理,能使小麦通过春化而进入幼穗分 化;对作物多施氮肥,则能使其延迟开花。 Environmental factors induce cell differentiation Environmental factors including light, temperture, nutrition, pH, ion, and electric potential can influence cell differentiation. For example: short day treatment can induce early flowering of Siberia Cocklebur: Low temperature treatment promotes wheat to start spike differentiation through velenization; nitrogen fertilizer causes delayed blossom of crop 植物激素调节细胞分化 植物激素能诱导细胞的分化,IAA有诱导维管组织分化的作用。培养基中生 长素和细胞激动素的比例影响愈伤组织的分化。当细胞分裂素相对浓度高,当生 长素的相对浓度高时,则有利于根的形成,而抑制芽的分化;反之,IAA与CTK 的比值低时,则有利于芽的形成,而抑制根的分化 Plant hormones regulate cell differentiation Certain hormones can induce cell differentiation One of the iaa functions is to induce vascular tissue differentiation. Root or bud differentiation depends on the ratio of IAA and cytokinin. High IAA/CTK stimulates root differentiation, but inhibits bud differentiation: while low IAA/CTK stimulates bud differentiation: but inhibits root differentiation 组织培养 植物组织培养是指植物的离体器官、组织或细胞在人工控制的环境下培养发 育再生成完整植株的技术。植物组织培养的理论基础建立在植物细胞全能性的概 念上。植物细胞的全能性是指植物的每个细胞在一定的条件下可以分裂、分化产 生植物体的各种细胞,最终发育成完整的植株。组织培养的过程主要包括脱分化 和再分化。组织培养技术已经广泛地应用于科学研究和生产实践。 Tissue culture tissue from a plant are transferred to an artificial environment in which they calor Tissue culture is a method of biological research in which cells or fragments
reinitiate cell division, and in some cases, when provided with the appropriate nutrients and hormones, even regenerate whole plants. 极性是细胞分化的前提 极性是指细胞(也可指器官和植株)内不同区域在形态结构和生理生化上存 在差异的现象。极性的建立会引发不均等分裂，使两个子细胞的大小和内含物不 等，由此引起分裂细胞的分化。例如:胚胎发生在初期就建立了轴向极性。受精 卵在第一次分裂前已经极化。受精卵顶端含有较浓的细胞质成分，而基端主要含 一个大的中央液泡。第一次分裂产生的两个细胞朝着不同的方向进行分化。 Cell Polarity is a prerequisite of cell differentiation Cell Polarity refers to spatial differences in the shape, structure, and function of cells. Polarity establishment cause asymmetric cell division, thus the two daughter cells have differences in size and cell content, which leads to the differentiation of the daughter cells. For example: Axial polarity is established very early in embryogenesis. The zygote becomes polarized before its first division. The apical end of the zygote is densely cytoplasmic, but the basal half of the cell contains a large central vacuole. The first division of the zygote creates two cells that carry out differentiation toward different directions. 细胞分化受环境条件诱导 光照、温度、营养、pH、离子和电势等环境条件都能影响细胞的分化。如 短日照处理，可诱导苍耳提前开花；低温处理，能使小麦通过春化而进入幼穗分 化；对作物多施氮肥，则能使其延迟开花。 Environmental factors induce cell differentiation Environmental factors including light, termperture, nutrition, pH, ion, and electric potential can influence cell differentiation. For example: short day treatment can induce early flowerling of Siberia Cocklebur；Low temperature treatment promotes wheat to start spike differentiation through velenization; nitrogen fertilizer causes delayed blossom of crops. 植物激素调节细胞分化 植物激素能诱导细胞的分化，IAA 有诱导维管组织分化的作用。培养基中生 长素和细胞激动素的比例影响愈伤组织的分化。当细胞分裂素相对浓度高，当生 长素的相对浓度高时，则有利于根的形成，而抑制芽的分化; 反之，IAA 与 CTK 的比值低时，则有利于芽的形成，而抑制根的分化。 Plant hormones regulate cell differentiation Certain hormones can induce cell differentiation. One of the IAA functions is to induce vascular tissue differentiation. Root or bud differentiation depends on the ratio of IAA and cytokinin. High IAA/CTK stimulates root differentiation, but inhibits bud differentiation; while low IAA/CTK stimulates bud differentiation; but inhibits root differentiation. 组织培养 植物组织培养是指植物的离体器官、组织或细胞在人工控制的环境下培养发 育再生成完整植株的技术。植物组织培养的理论基础建立在植物细胞全能性的概 念上。植物细胞的全能性是指植物的每个细胞在一定的条件下可以分裂、分化产 生植物体的各种细胞，最终发育成完整的植株。组织培养的过程主要包括脱分化 和再分化。组织培养技术已经广泛地应用于科学研究和生产实践。 Tissue culture Tissue culture is a method of biological research in which cells or fragments of tissue from a plant are transferred to an artificial environment in which they can
continue to survive and develop to a new plant. Tissue culture technique is established based on the concept of totipotency. Totipotency is the ability of a single cell to divide and produce all the differentiated cells in a plant, and thus can develop into a new plant under appropriate conditions. Plant tissue culture is used widely in plant science it also has a number of commercial applications 第二节植物的营养生长 植物的营养生长从胚胎发育开始,贯穿于植物的整个生命周期。受精卵如 何发育成胚?胚如何发育成幼苗?植物的根茎叶是如何发育的?在下面的小节 中,我们将从胚胎发育开始就目前已知的关于以上问题的答案进行讨论。 Plant vegetative development The vegetative phase of development begins with embryogenesis, but development continues throughout the life of a plant. How does a zygote give rise to an embryo, an embryo to a seedling? How do new plant struc preexisting structures? In the following sections, we will explore what is known about these questions, beginning with embryogenesis 1植物的胚胎发育 植物的生命周期是从单细胞受精卵发育成多细胞胚体开始的。该过程被称为 胚胎发生。胚胎发生过程在胚珠的胚囊中进行,被子植物的受精卵经生长发育成 为具有胚芽、胚轴、子叶和胚根的胚,胚珠本身发育成种子。胚是种子的一个部 分。初生分生组织也在胚胎发生过程形成。成年植物的 主要结构都是在胚胎发生后由分 生组织发育而来。虽然这些初生分生组织在胚胎发生过程已形成,只有到了种子 萌发过程它们才具有活力开始产生植物的组织和器官。 Embryogenesis Plant life cycle starts with a single-celled zygote transforming into a multicellular microscopic, embryonic plant. This process is known as embryogenesis Embryogenesis occurs within the embryo sac of the ovule Angiosperm embryogenesis forms a rudimentary plant body, typically consisting of an embryonic axis, bud radicle and cotyledon(s). while the ovule develops into the seed, and the embryo part of the seed. Embryogenesis also establishes the primary meristems. Most of the structures that make up the adult plant are generated after embryogenesis through the activity of meristems. Although these primary meristems are established during embryogenesis, only upon germination will they become active and begin to generate the organs and tissues of the adult 2种子萌发 种子的萌发的概念 种子能否迅速萌发以及萌发的质量与作物的收成关系密切相关。种子萌发的 定义是:干种子从吸水膨胀开始到胚轴伸长为止的这个过程是种子萌发。种子萌 发完成的可见标志是胚根从包裹胚的结构中伸出。随后的过程,包括储藏物质的 降解代谢都属于种苗发育的过程
continue to survive and develop to a new plant. Tissue culture technique is established based on the concept of totipotency. Totipotency is the ability of a single cell to divide and produce all the differentiated cells in a plant, and thus can develop into a new plant under appropriate conditions. Plant tissue culture is used widely in plant science; it also has a number of commercial applications. 第二节 植物的营养生长 植物的营养生长从胚胎发育开始， 贯穿于植物的整个生命周期。受精卵如 何发育成胚？胚如何发育成幼苗？植物的根茎叶是如何发育的？在下面的小节 中，我们将从胚胎发育开始就目前已知的关于以上问题的答案进行讨论。 Plant vegetative development The vegetative phase of development begins with embryogenesis, but development continues throughout the life of a plant. How does a zygote give rise to an embryo, an embryo to a seedling? How do new plant structures arise from preexisting structures? In the following sections, we will explore what is known about these questions, beginning with embryogenesis. 1.植物的胚胎发育 植物的生命周期是从单细胞受精卵发育成多细胞胚体开始的。该过程被称为 胚胎发生。胚胎发生过程在胚珠的胚囊中进行，被子植物的受精卵经生长发育成 为具有胚芽、胚轴、子叶和胚根的胚，胚珠本身发育成种子。胚是种子的一个部 分 。 初 生 分 生 组 织 也 在 胚 胎 发 生 过 程 形 成 。 成 年 植 物 的 主要结构都是在胚胎发生后由分 生组织发育而来。虽然这些初生分生组织在胚胎发生过程已形成，只有到了种子 萌发过程它们才具有活力开始产生植物的组织和器官。 Embryogenesis Plant life cycle starts with a single-celled zygote transforming into a multicellular microscopic, embryonic plant. This process is known as embryogenesis. Embryogenesis occurs within the embryo sac of the ovule Angiosperm embryogenesis forms a rudimentary plant body, typically consisting of an embryonic axis, bud, radicle and cotyledon(s). while the ovule develops into the seed，and the embryo is part of the seed. Embryogenesis also establishes the primary meristems. Most of the structures that make up the adult plant are generated after embryogenesis through the activity of merisstems. Although these primary meristems are established during embryogenesis, only upon germination will they become active and begin to generate the organs and tissues of the adult. 2 种子萌发 种子的萌发的概念 种子能否迅速萌发以及萌发的质量与作物的收成关系密切相关。种子萌发的 定义是:干种子从吸水膨胀开始到胚轴伸长为止的这个过程是种子萌发。种子萌 发完成的可见标志是胚根从包裹胚的结构中伸出。随后的过程，包括储藏物质的 降解代谢 都 属 于 种 苗 发 育 的 过 程
(修正) Seed germination Definition of seed germination Germination speed and quality are closely related to the yield of definition, germination commences when the quiescent dry seed begins to take up water(imbibitions) and is completed when the embryonic axis elongates. The visible sign that germination is completed is usually the penetration by the radical of structures surrounding the embryo. Subsequent events, including the mobilization of the major storage reserves, are associated with growth of the seedling 种子萌发过程的生理生化变化 成熟的干种子吸水可分为三个阶段,急剧地吸水(阶段Ⅰ),迟缓吸水(阶段 I),胚根伸出后重新迅速吸水(阶段Ⅲ),第三阶段属于萌发完成后的过程。种 子吸水后的变化之一是恢复呼吸活力,这种变化在种子吸水后几分钟就可以检测 到。在萌发初期氧气的消耗急剧上升,然后下降直到胚根开始延伸。这时, 急剧的呼吸上升再一次出现。种子吸水后,编码种子成熟和干燥过程必需蛋白质 的 mRNAs很可能迅速降解,而编码萌发过程必需蛋白质的 mRNAs开始合成 蛋白质的合成在种子吸水后也很快恢复,因为在成熟的干种子中含有新蛋白质合 成所需要的所有成分。胚根从包裹胚的结构中伸出标志着种子萌发过程的结束和 种苗发育过程的开始。这里需要强调的是:储藏物质的降解和转化是属于萌发后 事件,在种苗发育过程十分重要,但不属于萌发过程的事件。 Cellular events during germination Uptake of water by a mature dry seed is triphasic(Figure D); with a rapid initial uptake(phase I)followed by a plateau phase(phase II). A further increase in water uptake occurs only after germination is completed, as the embryonic axes elongate One of the first changes upon imbibition is the resumption of respiratory activity which can be detected within minutes. After a steep initial increase in oxygen consumption, the rate declines until the radicle penetrates the surrounding structures At this time, another burst of respiratory activity occurs. rapidly upon imbibiti messages encoding proteins that are important during seed maturation and drying are ikely to be degraded. Conversely, new transcripts encoding proteins required during early germination are synthesized, Resumption of protein synthesis take place soon after imbibition, for all of the components necessary for protein synthesis are present within the cells of mature dry seeds. Radicle extension through the structures surrounding the embryo is the event that terminates germination and marks the commencement of seedling growth. It is cautioned here that mobilization and conversion of the major stored reserves are postgerminative events that are important during seedling growth, but they are unrelated to germination 种子萌发需要的环境条件 种子萌发需要合适的环境条件:包括足够的水分,充足的氧气和适当的温度 种子吸水是完成萌发过程关键的第一步。因为很多种子有厚和硬的种皮。吸水后 种皮才会软化,氧气得以穿过种皮进入,种子的有氧呼吸增强。同时,种子吸水 后,胶状的细胞质变成流动状,分子可以在细胞内自由运动,生化反应才可能进 行。种子吸水后,细胞内的酶由非水合状态变为水合状态,恢复活力参与生化反
（修正） Seed germination Definition of seed germination Germination speed and quality are closely related to the yield of crops. By definition, germination commences when the quiescent dry seed begins to take up water (imbibitions) and is completed when the embryonic axis elongates. The visible sign that germination is completed is usually the penetration by the radical of structures surrounding the embryo. Subsequent events, including the mobilization of the major storage reserves, are associated with growth of the seedling. 种子萌发过程的生理生化变化 成熟的干种子吸水可分为三个阶段，急剧地吸水（阶段 I），迟缓吸水 (阶段 II)，胚根伸出后重新迅速吸水（阶段 III）,第三阶段属于萌发完成后的过程。种 子吸水后的变化之一是恢复呼吸活力，这种变化在种子吸水后几分钟就可以检测 到。 在萌发初期氧气的消耗急剧上升， 然后下降直到胚根开始延伸。 这时， 急剧的呼吸上升再一次出现。种子吸水后，编码种子成熟和干燥过程必需蛋白质 的 mRNAs 很可能迅速降解，而编码萌发过程必需蛋白质的 mRNAs 开始合成。 蛋白质的合成在种子吸水后也很快恢复，因为在成熟的干种子中含有新蛋白质合 成所需要的所有成分。胚根从包裹胚的结构中伸出标志着种子萌发过程的结束和 种苗发育过程的开始。这里需要强调的是：储藏物质的降解和转化是属于萌发后 事件，在种苗发育过程十分重要，但不属于萌发过程的事件。 Cellular events during germination Uptake of water by a mature dry seed is triphasic (Figure I); with a rapid initial uptake (phase I) followed by a plateau phase (phase II). A further increase in water uptake occurs only after germination is completed, as the embryonic axes elongate. One of the first changes upon imbibition is the resumption of respiratory activity, which can be detected within minutes. After a steep initial increase in oxygen consumption, the rate declines until the radicle penetrates the surrounding structures. At this time, another burst of respiratory activity occurs. Rapidly upon imbibition, messages encoding proteins that are important during seed maturation and drying are likely to be degraded. Conversely, new transcripts encoding proteins required during early germination are synthesized, Resumption of protein synthesis take place soon after imbibition, for all of the components necessary for protein synthesis are present within the cells of mature dry seeds. Radicle extension through the structures surrounding the embryo is the event that terminates germination and marks the commencement of seedling growth. It is cautioned here that mobilization and conversion of the major stored reserves are postgerminative events that are important during seedling growth, but they are unrelated to germination. 种子萌发需要的环境条件 种子萌发需要合适的环境条件：包括足够的水分，充足的氧气和适当的温度。 种子吸水是完成萌发过程关键的第一步。因为很多种子有厚和硬的种皮。吸水后 种皮才会软化，氧气得以穿过种皮进入，种子的有氧呼吸增强。同时，种子吸水 后，胶状的细胞质变成流动状，分子可以在细胞内自由运动，生化反应才可能进 行。种子吸水后，细胞内的酶由非水合状态变为水合状态，恢复活力参与生化反
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
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