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)