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