第十一章植物的生殖生理 Chapter 1l Plant re In their life cycle, plants enter juvenile vegetative phase after germination and then transition to an adult vegetative phase before producing reproductive structures. The juvenile phase is the time of life characterized by differences in appearance from the adult in which the plant lacks the ability to respond to flower-inducing stimuli. During its development, plant shoots progresses from a juvenile to an adult phase of vegetative growth and from a reproductively incompetent to a reproductively competent state. The acquisition of competence, which is the first development stage plants have to pass through for floral evocation, enables plants to sense and respond to signals that induce flowering. The next stage that a competent vegetative bud goes through is determination. Environmental signals can induce a state of floral determination in competent plants. A bud is said to be determined if it progresses to the next developmental age(flowering) even after being removed from its normal context. The two major signals for inducing light (photoperiod) and temperature(cold treatment). In this chapter, we will examine juvenility, vernalization, photoperiodism, and floral organ morphogenes 植物在其生长周期中经历了种子萌发,幼年期,成年期,以及生殖器官的发生等阶段。幼年期的 植株与成年期的形态不同,且对成花诱导无应答。随着不断生长,植株从幼年期转变为成年期,从无 生殖能力转变为性成熟状态。生殖能力的获得是成花诱导的第一步,之后植株便可以感知并应答诱导 开花的信号。接下来是花芽的出现,这对成花诱导起决定性作用。外界信号可促使发育完全的植株进 入成花决定状态。当花芽生长到即将开花的阶段时,其分化命运已被决定,即使从正常生长环境中被 移除,结果也不会改变。诱导开花的两个主要信号是光(光周期)和温度(低温)。本章将对幼年期 春化作用,光周期现象,以及花器官的形成展开研究 111 Juvenility(幼年期) The character and timing of the juvenile-to-adult transition vary widely between species. In annual plants, this transition occurs soon after germination and usually involves relatively minor me hanges, whereas in trees and other perennial woody plants it occurs after months or years and can major changes in shoot architecture 植株从幼年期转变到成年期的特点及时机因种类而异。对于一年生植物,这种转变发生在种子萌 发后的较短时间内,且伴随着较小的形态变化:然而对于树木以及大部分木本植物而言,这种转变发 生在种子萌发后的几个月甚至几年后,且在植株建成过程中发生较大的形态变化。 In the juvenile phase, a young seedling plant displays one or more distinctive characteristics of both a morphological and physiological nature. These distinguish a juvenile plant from an adult. There are numerous substantive phenotypic traits associated with juvenility, but they vary considerably among pecies. Commonly the leaves on young plants are of a different shape than those on mature parts and may be simple rather than compound. Juvenile leaves may also have a special type of cuticle and be arranged with a distinct phyllotaxy. The juvenile plant also exhibit different physiological features such as higher rates of photosynthesis, respiration, and growth. 幼年期的植株在形态及生理方面均有显著特征,与成年期植株明显不同。植株在幼年期拥有众多 表型特征,但均存在较大的种间差异。一般而言,幼苗的叶片与成熟植物的叶片有着不同的形状且前 者更为简单。幼叶有着特殊类型的表皮以及独特的叶序。与成年植株相较,幼年植株也展现出不同的 生理特征,如较高的光合速率,呼吸速率及生长速率等。 When a plant is juvenile, it puts on juvenile growth. When a plant is sufficiently old and large, it goes through phase change and develops adult characteristics. These characteristics will manifest themselves on the newest growth. Therefore, the outside and higher portion of a mature tree is the most adult. The lower and older portion of the plant retains their juvenile characteristics. There can be a transition region between
第十一章 植物的生殖生理 Chapter 11 Plant reproductive physiology In their life cycle，plants enter juvenile vegetative phase after germination and then transition to an adult vegetative phase before producing reproductive structures. The juvenile phase is the time of life characterized by differences in appearance from the adult in which the plant lacks the ability to respond to flower-inducing stimuli. During its development, plant shoots progresses from a juvenile to an adult phase of vegetative growth and from a reproductively incompetent to a reproductively competent state. The acquisition of competence, which is the first development stage plants have to pass through for floral evocation, enables plants to sense and respond to signals that induce flowering. The next stage that a competent vegetative bud goes through is determination. Environmental signals can induce a state of floral determination in competent plants. A bud is said to be determined if it progresses to the next developmental stage (flowering) even after being removed from its normal context. The two major signals for inducing flowering are light (photoperiod) and temperature (cold treatment). In this chapter, we will examine juvenility, vernalization, photoperiodism, and floral organ morphogenesis. 植物在其生长周期中经历了种子萌发，幼年期，成年期，以及生殖器官的发生等阶段。幼年期的 植株与成年期的形态不同，且对成花诱导无应答。随着不断生长，植株从幼年期转变为成年期，从无 生殖能力转变为性成熟状态。生殖能力的获得是成花诱导的第一步，之后植株便可以感知并应答诱导 开花的信号。接下来是花芽的出现，这对成花诱导起决定性作用。外界信号可促使发育完全的植株进 入成花决定状态。当花芽生长到即将开花的阶段时，其分化命运已被决定，即使从正常生长环境中被 移除，结果也不会改变。诱导开花的两个主要信号是光（光周期）和温度（低温）。本章将对幼年期， 春化作用，光周期现象，以及花器官的形成展开研究。 11.1 Juvenility（幼年期） The character and timing of the juvenile-to-adult transition vary widely between species. In annual plants, this transition occurs soon after germination and usually involves relatively minor morphological changes, whereas in trees and other perennial woody plants it occurs after months or years and can involve major changes in shoot architecture. 植株从幼年期转变到成年期的特点及时机因种类而异。对于一年生植物，这种转变发生在种子萌 发后的较短时间内，且伴随着较小的形态变化；然而对于树木以及大部分木本植物而言，这种转变发 生在种子萌发后的几个月甚至几年后，且在植株建成过程中发生较大的形态变化。 In the juvenile phase, a young seedling plant displays one or more distinctive characteristics of both a morphological and physiological nature. These distinguish a juvenile plant from an adult. There are numerous substantive phenotypic traits associated with juvenility, but they vary considerably among species.Commonly, the leaves on young plants are of a different shape than those on mature parts and may be simple rather than compound. Juvenile leaves may also have a special type of cuticle and be arranged with a distinct phyllotaxy. The juvenile plant also exhibit different physiological features such as higher rates of photosynthesis，respiration，and growth. 幼年期的植株在形态及生理方面均有显著特征，与成年期植株明显不同。植株在幼年期拥有众多 表型特征，但均存在较大的种间差异。一般而言，幼苗的叶片与成熟植物的叶片有着不同的形状且前 者更为简单。幼叶有着特殊类型的表皮以及独特的叶序。与成年植株相较，幼年植株也展现出不同的 生理特征，如较高的光合速率，呼吸速率及生长速率等。 When a plant is juvenile, it puts on juvenile growth. When a plant is sufficiently old and large, it goes through phase change and develops adult characteristics. These characteristics will manifest themselves on the newest growth. Therefore, the outside and higher portion of a mature tree is the most adult. The lower and older portion of the plant retains their juvenile characteristics. There can be a transition region between
the juvenile and adult portion of the plant. Leaf drop or abscission in deciduous plant occurs mainly in the adult parts of a tree, juvenile parts of the tree usually hold their senescence leaves throughout the winter 幼年期的植株按这一时期所特有的生长规律进行生长,转入成年期后,逐步发展出成熟植物的特 点,这些特点表明植株处于一个新的生长期。因此,一棵成熟树木的顶端是其最成熟的部位,基部仍 然保留着幼年期的特点,中部则为过渡型。到了冬季,落叶植物处于成年期的叶片脱落而幼年期的叶 片仍存于树上。 112 Vernalization春化作用 112. Definition of vernalization春化作用的概念 Vernalizaiton refers specifically to the promotion of flowering in an imbibed seed or a growing plant by a period of low temperature. Vernalization occurs most commonly in winter annuals and biennials. Plants differ considerably in the age at which they become sensitive to vernalization. Winter annuals, such as the winter forms of cereals, which are sown in the fall and flower in the following summer, have the capacity to perceive a vermalizaiton treatment as an imbibed seed. Other plants, including most biennials, which grow as rosettes in the first season, bolt and flower in the following summer, must advance through the juvenile stage into an adult stage before they have the capacity to perceive a venalizaiton treatment. 春化作用特指用一段时间的低温诱导吸胀的种子或生长中的植物开花的过程,主要发生于冬性 年生植物及一些二年生植物上。不同植物在不同的生长期感知春化作用。冬性一年生植物,如冬小麦, 在头一年秋季播种,第二年夏季开花,其在种子吸胀萌动时就可感知春化作用。其他大部分二年生植 物,在第一年只长莲座状的叶丛,第二年夏季抽薹开花,它们必须从幼年期转化为成年期才能感知春 化作用。 The range of temperatures effective and duration of exposure in vemaliation varies widely depending on the species. In general, vermalizaiton can occur at temperatures ranging from just below freezing to about The effect of cold is proportional to the duration of the cold treatment until the response is saturated he response usually requires several weeks of exposure to low temperature, but the precise duration varies widely with species and variety. For instance, Lunaria biennis L. requires nine week, Secale cereale L. (winter rye)requires six week. In contrast, vernalization time can be as short as 6-8 days for R sativus Chinese jumbo radish Scarlet 有效温度及低温持续时间 春化作用的有效温度和低温持续时间的范围取决于植物种类。一般而言,0-14°C下可发生春化, 大多数种类植物的最适温度介于1~7°之间。 在春化过程结束前,低温效应与低温持续时间成比例关系。春化时通常需要将植物低温处理几周, 但具体持续时间随植物种类而定。例如,缎花(银扇草)需要9周,冬黑麦需要6周,而萝卜短至6~8 日 1123 Devernalization(脱春化作用) The reversal of vernalization by environmental conditions is referred to as'devernalozation'. The period between the completion of a vernalization treatment and flower initiation can be divided into two phases. Phase I is a period immediately after vernaliation when vernalization can be lost as a result of Il is that period after phase I when flower induction is stable and reversed(是否应该为 irreversible?) 由外界条件变化引起的春化作用的逆转称为脱春化作用。从春化过程结束到开始开花前的这段时 间可被分为两个阶段。第一阶段紧随春化作用的结束,这个阶段中春化作用会被诸如高温、低辐照、 短日照等条件消除。第二阶段在第一阶段之后,此时成花诱导是稳定且不可逆转的
the juvenile and adult portion of the plant. Leaf drop or abscission in deciduous plant occurs mainly in the adult parts of a tree, juvenile parts of the tree usually hold their senescence leaves throughout the winter. 幼年期的植株按这一时期所特有的生长规律进行生长，转入成年期后，逐步发展出成熟植物的特 点，这些特点表明植株处于一个新的生长期。因此，一棵成熟树木的顶端是其最成熟的部位，基部仍 然保留着幼年期的特点，中部则为过渡型。到了冬季，落叶植物处于成年期的叶片脱落而幼年期的叶 片仍存于树上。 11.2 Vernalization 春化作用 11.2.1 Definition of vernalization 春化作用的概念 Vernalizaiton refers specifically to the promotion of flowering in an imbibed seed or a growing plant by a period of low temperature. Vernalization occurs most commonly in winter annuals and biennials. Plants differ considerably in the age at which they become sensitive to vernalization. Winter annuals, such as the winter forms of cereals, which are sown in the fall and flower in the following summer, have the capacity to perceive a vernalizaiton treatment as an imbibed seed. Other plants, including most biennials, which grow as rosettes in the first season, bolt and flower in the following summer, must advance through the juvenile stage into an adult stage before they have the capacity to perceive a vernalizaiton treatment. 春化作用特指用一段时间的低温诱导吸胀的种子或生长中的植物开花的过程，主要发生于冬性一 年生植物及一些二年生植物上。不同植物在不同的生长期感知春化作用。冬性一年生植物，如冬小麦， 在头一年秋季播种，第二年夏季开花，其在种子吸胀萌动时就可感知春化作用。其他大部分二年生植 物，在第一年只长莲座状的叶丛，第二年夏季抽薹开花，它们必须从幼年期转化为成年期才能感知春 化作用。 11.2.2 Effective temperature and required duration of exposure The range of temperatures effective and duration of exposure in vernaliation varies widely depending on the species. In general, vernalizaiton can occur at temperatures ranging from just below freezing to about 14°C, there is an optimal temperature usually between about 1 and 7°C for most species. The effect of cold is proportional to the duration of the cold treatment until the response is saturated. The response usually requires several weeks of exposure to low temperature, but the precise duration varies widely with species and variety. For instance, Lunaria biennis L. requires nine week, Secale cereale L. (winter rye) requires six week. In contrast, vernalization time can be as short as 6-8 days for R. sativus ‘Chinese Jumbo Radish Scarlet’. 有效温度及低温持续时间 春化作用的有效温度和低温持续时间的范围取决于植物种类。一般而言， 0~14°C下可发生春化， 大多数种类植物的最适温度介于1~7°C之间。 在春化过程结束前，低温效应与低温持续时间成比例关系。春化时通常需要将植物低温处理几周， 但具体持续时间随植物种类而定。例如，缎花（银扇草）需要9周，冬黑麦需要6周，而萝卜短至6~8 日。 11.2.3 Devernalization（脱春化作用） The reversal of vernalizarion by environmental conditions is referred to as ‘devernalozation’. The period between the completion of a vernalization treatment and flower initiation can be divided into two phases. Phase I is a period immediately after vernaliation when vernalization can be lost as a result of exposure to devernalizing conditions, such as high temperature, low irradiance, and/or SD conditions. Phase II is that period after phase I when flower induction is stable and reversed（是否应该为irreversible？）. 由外界条件变化引起的春化作用的逆转称为脱春化作用。从春化过程结束到开始开花前的这段时 间可被分为两个阶段。第一阶段紧随春化作用的结束，这个阶段中春化作用会被诸如高温、低辐照、 短日照等条件消除。第二阶段在第一阶段之后，此时成花诱导是稳定且不可逆转的
112.4 Perception of vernalization(春化作用的感知) The site of perception of vernalization is the shoot apical meristem. Studies conducted where different portions of the plant were cooled relative to the rest of the plant indicate that the shoot apical meristem is solely capable of perception 感知春化刺激的部位是茎尖端分生组织。有研究通过低温处理植物的不同部位来探究其对其他部 位的影响,结果表明:唯有茎尖端分生组织具有感知低温刺激的能力。 112.5 The nature of the vernalization stimulus(春化刺激的本质) When a vernalized Hyoscyamus plant is grafted to an unvernalized plant, both will flower under long days. Experiments such as this suggested the existence of transmissible verbalization stimulus, which called'vernalin', but attempts to isolate vernalin have never been successful. No conclusive picture has so far emerged 将已春化的天仙子叶片嫁接到未春化植物的砧木上,一段时间后,两者均会开花。类似的实验证 明春化过程中形成一种可传导的剌激物质,这种物质称为春化素,目前还未能将其从植物体中分离出 来。因此,对于春化素至今仍没有定论 112.6 Molecular aspects of vernalization(春化作用的分子机理) Recent studies have revealed some of the molecular mechanisms involving downregu protein FLOWERING LOCUS C(FLC), which would otherwise prevent flowering, through epigenetic modification. This hypothesis was first generated from the studies on Arabidopsis. The key epigenetic hanges accompanying vernalization in this species is the trimethylation of lysine 27(K27me3)in histone 13 that repress FLC. The H3K27me3 modification is responsible for the epigenetic downregulation of FLC. The absence of the repressor protein FLC following vemalization then activates the expression of two other genes, FLOWERING LOCUS T (FT)and SUPPRESSOR OF OVER EXPRESSION OF CONSTANS (SOC1), and the activity of their gene products triggers the genes that control flower development. It has DNA methyltion. The cold treatment results in demethyltion of the promoter regions and subsequent actiation of a gene or genes critical for initiating reproductive developmen 近期的研究通过表观遗传修饰的方法揭示了开花阻抑蛋白 FLOWERING LOCUS C(FLC)的下调 机理,该理论是在对拟南芥的研究中首次被发现的。研究表明,伴随着拟南芥的春化而产生的关键性 遗传改变是H3上K27的三甲基化,这导致了FLC被抑制,即H3K27me3与FCL的下调直接相关。 春化时阻抑蛋白FCL的减少激活了另外两个基因 FLOWERING LOCUS T(FT)和 SUPPRESSOR OF OⅤ ER EXPRESSION OF CONSTANS(SOC1)的表达,其基因产物进而触发了开花控制基因的活化 另外,拟南芥及其他植物的春化反应也受DNA甲基化/去甲基化的调节。由低温处理而导致的基因增 强子区的去甲基化以及随后引发的一系列其他基因的活化对植物生殖生长的启动十分重要。 13 Photoperiodism光周期现象 113.1 Definition of photoperiodism(光周期现象的概念) Photoperiod is the duration of daily period of light and dark. In most latitudes there are seasonal changes in the length of the photoperiod, photoperiodism is the developmental responses of plants to the relative lengths of the light and dark periods, Plant responses controlled by photoperiodism are numerous, dormancy. Photoperiodism is primarily associated with longer-lived species that survive for at least a single growing season. Development of such species can often depend on photoperiod to synchronize flowering to ensure that flowering occurs at a specific time of year in order to allow successful seed set and maturation along with cross-pollination. 光周期是指一昼夜的光暗交替。地球上大多数纬度地区存在昼夜长短的季节性变化,光周期现象
11.2.4 Perception of vernalization（春化作用的感知） The site of perception of vernalization is the shoot apical meristem. Studies conducted where different portions of the plant were cooled relative to the rest of the plant indicate that the shoot apical meristem is solely capable of perception. 感知春化刺激的部位是茎尖端分生组织。有研究通过低温处理植物的不同部位来探究其对其他部 位的影响，结果表明：唯有茎尖端分生组织具有感知低温刺激的能力。 11.2.5 The nature of the vernalization stimulus（春化刺激的本质） When a vernalized Hyoscyamus plant is grafted to an unvernalized plant, both will flower under long days. Experiments such as this suggested the existence of transmissible verbalization stimulus, which is called ‘vernalin’, but attempts to isolate vernalin have never been successful. No conclusive picture has so far emerged. 将已春化的天仙子叶片嫁接到未春化植物的砧木上，一段时间后，两者均会开花。类似的实验证 明春化过程中形成一种可传导的刺激物质，这种物质称为春化素，目前还未能将其从植物体中分离出 来。因此，对于春化素至今仍没有定论。 11.2.6 Molecular aspects of vernalization（春化作用的分子机理） Recent studies have revealed some of the molecular mechanisms involving downregulation of the protein FLOWERING LOCUS C (FLC), which would otherwise prevent flowering, through epigenetic modification. This hypothesis was first generated from the studies on Arabidopsis. The key epigenetic changes accompanying vernalization in this species is the trimethylation of lysine 27 (K27me3) in histone H3 that repress FLC. The H3K27me3 modification is responsible for the epigenetic downregulation of FLC. The absence of the repressor protein FLC following vernalization then activates the expression of two other genes, FLOWERING LOCUS T (FT) and SUPPRESSOR OF OVER EXPRESSION OF CONSTANS (SOC1), and the activity of their gene products triggers the genes that control flower development. It has also been proposed that vernalization responses, in Arabidopsis and other plants, is mediated by changes in DNA methyltion. The cold treatment results in demethyltion of the promoter regions and subsequent actiation of a gene or genes critical for initiating reproductive development. 近期的研究通过表观遗传修饰的方法揭示了开花阻抑蛋白 FLOWERING LOCUS C (FLC)的下调 机理，该理论是在对拟南芥的研究中首次被发现的。研究表明，伴随着拟南芥的春化而产生的关键性 遗传改变是 H3 上 K27 的三甲基化，这导致了 FLC 被抑制，即 H3K27me3 与 FCL 的下调直接相关。 春化时阻抑蛋白 FCL 的减少激活了另外两个基因 FLOWERING LOCUS T (FT) 和 SUPPRESSOR OF OVER EXPRESSION OF CONSTANS (SOC1)的表达，其基因产物进而触发了开花控制基因的活化。 另外，拟南芥及其他植物的春化反应也受 DNA 甲基化/去甲基化的调节。由低温处理而导致的基因增 强子区的去甲基化以及随后引发的一系列其他基因的活化对植物生殖生长的启动十分重要。 11.3 Photoperiodism 光周期现象 11.3.1 Definition of photoperiodism（光周期现象的概念） Photoperiod is the duration of daily period of light and dark. In most latitudes there are seasonal changes in the length of the photoperiod, photoperiodism is the developmental responses of plants to the relative lengths of the light and dark periods, Plant responses controlled by photoperiodism are numerous, including the initiation of flowering, asexual reproduction, the formation of storage organs, and the onset of dormancy. Photoperiodism is primarily associated with longer-lived species that survive for at least a single growing season. Development of such species can often depend on photoperiod to synchronize flowering to ensure that flowering occurs at a specific time of year in order to allow successful seed set and maturation along with cross-pollination. 光周期是指一昼夜的光暗交替。地球上大多数纬度地区存在昼夜长短的季节性变化，光周期现象
即为植物对白天和黑夜的相对长度的反应。植物的很多生理活动都受光周期的调控,如开花的诱导 无性生殖,贮藏器官的形成,休眠的开始等。光周期现象主要表现在寿命较长的植物种类上,该植物 至少能存活一个生长季节。这类植物依靠光周期使开花发生在特定的时期,从而确保伴随着异花授粉 的实现,植物可以顺利地结实与成熟。 113.2 Three types of Photoperiodic Responses(三种光周期反应类型 Plants are classified into three categories: short-day(long-night), long-day(short-night), or day-neutral depending on their response to the day length for flowering: 1. Short-day plants (SDPs)require shorter than a certain number of hours of light to induce flowering. In general, short-day plants flower as days grow shorter, which is during summer or fall in the northern hemisphere. 2. Long-day plants(LDPs)require longer than a certain number of hours of light in each 24-hour period to induce flowering. These plants typically flower in the northern hemisphere during late spring or early summer as days are getting longer 3. Day-neutral plants(DNPs)such as cucumbers, roses and tomatoes, do not initiate flowering based on photoperiodism at all; they flower regardless of the day length. They may initiate flowering after attaining a certain overall developmental stage or age, or in response to alternative environmental stimuli, for example, many desert annuals, such as Castilleja chromos(desert paintbrush), evolved to germinate, grow, and flower quickly whenever sufficient water is available. Further, some species exhibit a dual requirement for successful flowering, i. e. they may require a prescribed sequence of inductive conditions such as SD-LD (short day-long day)or LD-SD 根据植物在日照长短变化时的开花反应可将其分为三个类型:短日(长夜)植物,长日(短夜) 植物及日中性植物。短日植物在光照时间短于一定时数时才能成花。一般而言,北半球的夏末和秋季 白天逐渐变短,短日植物可在这段时间开花。长日植物在每一个24h昼夜周期中光照时间长于一定时 数时才能成花。因此,这些植物往往在北半球的春末夏初白天变长时开花。日中性植物如黄瓜、玫瑰 番茄等,成花不受光周期现象的影响,在任何长度的日照下均可进行。这类植物通常在发育到一定的 生长阶段或者接受一定的环境刺激后即可开花。例如沙漠画笔等许多沙漠一年生植物,无论何时, 要有足够的水分便可发芽生长,然后迅速开花。 另外,还有一些植物对成花有着双重需求,它们可能需要短日-长日或者长日-短日的双重诱导。 113.3 Critical day length(临界日长) Ithough plants are grouped as short day or long day plants, the distinction between Sd plant and LD plant is not based on the absolute length of day. Whether a plant is classified as a Sd plant or LD plant depends on its behavior relative to a certain duration, called the critical day length. Critical day length can be defined as the maximum day length a short-day plant, and the minimum day length a long-day plant, require to initiate flowering. Thus flowering in LDPs is promoted only when the day length exceeds the critical day length, whereas promotion of flowering in SDPs requires a day length that is less than the critical day length. The absolute value of the critical day length varies widely among species 植物被分为短日或长日植物的依据并非绝对日长,而是临界日长,它们对一定时间的日照会产生 不同的反应。临界日长指的是诱导短日植物开花的最长日照或者诱导长日植物开花的最短日照。对于 长日植物而言,只有当日长大于临界日长时才能开花:而对于短日植物而言,只有当日长小于临界日 长时才能开花。临界日长的具体数值存在种间差异。 1l34 Important role of the night length(夜长在光周期现象中的重要性) Under natural conditions, day and night lengths configure a 24-hour cycle of light and darkness. The term photoperiodism implies that plants measure the relative lengths of day and night, which is misleading In fact, a plant measures neither the relative length of day and night nor the duration of daylight, it measures the length of dark period. This was elegantly demonstrated by the experiments of Hamner and Bonner(1938) and Hamner(1940)where flowering of cocklebur, a short day plant, occurred only when night length exceed
即为植物对白天和黑夜的相对长度的反应。植物的很多生理活动都受光周期的调控，如开花的诱导， 无性生殖，贮藏器官的形成，休眠的开始等。光周期现象主要表现在寿命较长的植物种类上，该植物 至少能存活一个生长季节。这类植物依靠光周期使开花发生在特定的时期，从而确保伴随着异花授粉 的实现，植物可以顺利地结实与成熟。 11.3.2 Three types of Photoperiodic Responses（三种光周期反应类型） Plants are classified into three categories: short-day (long-night), long-day (short-night), or day-neutral, depending on their response to the day length for flowering: 1. Short-day plants (SDPs) require shorter than a certain number of hours of light to induce flowering. In general, short-day plants flower as days grow shorter, which is during summer or fall in the northern hemisphere. 2. Long-day plants (LDPs) require longer than a certain number of hours of light in each 24-hour period to induce flowering. These plants typically flower in the northern hemisphere during late spring or early summer as days are getting longer. 3. Day-neutral plants (DNPs) such as cucumbers, roses and tomatoes, do not initiate flowering based on photoperiodism at all; they flower regardless of the day length. They may initiate flowering after attaining a certain overall developmental stage or age, or in response to alternative environmental stimuli, for example, many desert annuals, such as Castilleja chromosa (desert paintbrush), evolved to germinate, grow, and flower quickly whenever sufficient water is available. Further, some species exhibit a dual requirement for successful flowering, i. e. they may require a prescribed sequence of inductive conditions such as SD-LD (short day-long day) or LD-SD. 根据植物在日照长短变化时的开花反应可将其分为三个类型：短日（长夜）植物，长日（短夜） 植物及日中性植物。短日植物在光照时间短于一定时数时才能成花。一般而言，北半球的夏末和秋季 白天逐渐变短，短日植物可在这段时间开花。长日植物在每一个24h昼夜周期中光照时间长于一定时 数时才能成花。因此，这些植物往往在北半球的春末夏初白天变长时开花。日中性植物如黄瓜、玫瑰、 番茄等，成花不受光周期现象的影响，在任何长度的日照下均可进行。这类植物通常在发育到一定的 生长阶段或者接受一定的环境刺激后即可开花。例如沙漠画笔等许多沙漠一年生植物，无论何时，只 要有足够的水分便可发芽生长，然后迅速开花。 另外，还有一些植物对成花有着双重需求，它们可能需要短日-长日或者长日-短日的双重诱导。 11.3.3 Critical day length（临界日长） Although plants are grouped as short day or long day plants, the distinction between SD plant and LD plant is not based on the absolute length of day. Whether a plant is classified as a SD plant or LD plant depends on its behavior relative to a certain duration, called the critical day length. Critical day length can be defined as the maximum day length a short-day plant, and the minimum day length a long-day plant, require to initiate flowering. Thus flowering in LDPs is promoted only when the day length exceeds the critical day length, whereas promotion of flowering in SDPs requires a day length that is less than the critical day length. The absolute value of the critical day length varies widely among species. 植物被分为短日或长日植物的依据并非绝对日长，而是临界日长，它们对一定时间的日照会产生 不同的反应。临界日长指的是诱导短日植物开花的最长日照或者诱导长日植物开花的最短日照。对于 长日植物而言，只有当日长大于临界日长时才能开花；而对于短日植物而言，只有当日长小于临界日 长时才能开花。临界日长的具体数值存在种间差异。 11.3.4 Important role of the night length （夜长在光周期现象中的重要性） Under natural conditions, day and night lengths configure a 24-hour cycle of light and darkness. The term photoperiodism implies that plants measure the relative lengths of day and night，which is misleading. In fact, a plant measures neither the relative length of day and night nor the duration of daylight, it measures the length of dark period. This was elegantly demonstrated by the experiments of Hamner and Bonner (1938) and Hamner (1940) where flowering of cocklebur, a short day plant, occurred only when night length exceed
8.5 h, but remained vegetative on a schedule of 16 h light and 8 h darkness. On schedule of 4 h light-8 h darkness, plants remained vegetative even though the 4 h day length is much shorter than the 15.5 h critical day length. On the other hand, schedule of 16 h light-32 h darkness induced rapid flowering even thoug the day length exceeded the critical day length. Night break lighting of cocklebur of as little as a few minutes prevented flowering even when the total night length was sufficient to promote flowering. Similarly, night break lighting can result in stimulation of flowering in LDP. But much longer lengths of time of a night break are often required to promote flowering in LDPs. So a SDP could actually be a LNP(long night plant) and a LDP could really be a SNP(short night plant 在自然条件下,昼夜总是在24h的周期内交替出现。依据“光周期现象”的定义可知,植物可以 估量白天与黑夜的相对长度,这其实是不准确的。事实上,植物既不能估量白天与黑夜的相对长度 也不能估量白天的绝对长度,它只能估量夜晚的长度。这一理论可以完美地解释 Hamner and Bonner (1938)与 Hamner(1940)利用苍耳所做的成花诱导实验。苍耳是短日植物,只有在夜长超过8h时才可 开花,当日长为l6h且夜长为$h时,其进行营养性生长,不开花:当日长为4h且夜长为8h时,其仍为 营养性生长,此时4h已远远短于临界日长155h。但另一方面,当日长为16h且夜长为32h时,其很快 便开花了,即使此时16h已超过临界日长。在足够引起苍耳开花的暗期内,即使一个短至几分钟的夜 间断也能阻断其开花。与此类似,夜间断也可以影响长日植物的成花诱导,但较长时间的夜间断通常 可以促进其开花。因此,短日植物实际是长夜植物,长日植物实际是短夜植物 113.5 Perception of the photoperiodic signal(光周期信号的感知) The photoperiodic stimulus in both LDPs and SDPs is perceived not by the stem apex, where the actual change from vegetative to reproductive growth occur, but by the leaves. This has been demonstrated experimentally. For example, SDP cocklebur stripped of all but one leaf could be induced to flower if the remaining leaf were provided the appropriate photoperiod, even when the rest of the plant is exposed to long days. Photoperiodic induction can take place in a leaf that has been separated from the plant. For example, in the SDP Perilla crispa, an excised leaf exposed to short days can cause flowering when subsequently grafted to a noninduced plant maintained in long days(Zeevaart and Boyer 1987). This result indicates that photoperiodic induction depends on events that take place exclusively in the leaf. 实验证明,长日植物与短日植物感受光周期刺激的部位不是茎尖端生长点(从营养生长转变为生 殖生长的发生部位),而是叶片。例如,将短日植物苍耳的叶片去除到只剩一片叶子,将这片叶子用 合适的光诱导周期处理,即使该植物的其他部位处于长日照下,植物仍能开花。光周期诱导还可发生 在离体的叶片上。例如,将一片离体的紫苏(短日植物)叶片用短日照处理后嫁接于一株未诱导的长 日照植物上,可引起后者开花。这个现象表明光周期诱导仅与叶片上发生的反应有关。 113.6 Photoperiodic induction(光周期诱导) The photoperiod-regulated processes that occur in the leaves resulting in the transmission of a floral tumulus to the shoot apex are referred to collectively as photoperiodic induction. The appropriate photoperiod is referred to as an inductive treatment. The number of inductive treatments required to induce flowering varies with species. Some plants, such as cocklebur, will proceed to flower even if the plant is returned to unfavorable photoperiods after a single inductive treatment, many other plants require more or less continuous inductive treatments to induce flowering Induction is not an all-or-none process, but can be achieved in degrees. For example, the flowering of cocklebur can be induced by a single inductive treatment but the flower initiation can be more rapid and prolific if more inductive treatments are given 发生在叶片上的反应产生成花物质并传导到茎尖端,这一受光周期调控的过程统称为光周期诱 导。适宜的光周期便是一次诱导处理。开花所需的诱导次数因植物种类而异。有些植物(如苍耳)在 次诱导处理后,即使被置于不适宜的光周期下也仍能开花,另外一些植物或多或少需要连续几次的 诱导处理才能开花。诱导处理并非一个“全或无”的过程,可以表现为梯度式。如苍耳可以在接受
8.5 h, but remained vegetative on a schedule of 16 h light and 8 h darkness. On schedule of 4 h light-8 h darkness, plants remained vegetative even though the 4 h day length is much shorter than the 15.5 h critical day length. On the other hand, schedule of 16 h light-32 h darkness induced rapid flowering even thoug the day length exceeded the critical day length. Night break lighting of cocklebur of as little as a few minutes prevented flowering even when the total night length was sufficient to promote flowering. Similarly, night break lighting can result in stimulation of flowering in LDP. But much longer lengths of time of a night break are often required to promote flowering in LDPs. So a SDP could actually be a LNP (long night plant), and a LDP could really be a SNP (short night plant). 在自然条件下，昼夜总是在24h的周期内交替出现。依据“光周期现象”的定义可知，植物可以 估量白天与黑夜的相对长度，这其实是不准确的。事实上，植物既不能估量白天与黑夜的相对长度， 也不能估量白天的绝对长度，它只能估量夜晚的长度。这一理论可以完美地解释Hamner and Bonner (1938) 与Hamner (1940)利用苍耳所做的成花诱导实验。苍耳是短日植物，只有在夜长超过8.5h时才可 开花，当日长为16h且夜长为8h时，其进行营养性生长，不开花；当日长为4h且夜长为8h时，其仍为 营养性生长，此时4h已远远短于临界日长15.5h。但另一方面，当日长为16h且夜长为32h时，其很快 便开花了，即使此时16h已超过临界日长。在足够引起苍耳开花的暗期内，即使一个短至几分钟的夜 间断也能阻断其开花。与此类似，夜间断也可以影响长日植物的成花诱导，但较长时间的夜间断通常 可以促进其开花。因此，短日植物实际是长夜植物，长日植物实际是短夜植物。 11.3.5 Perception of the photoperiodic signal（光周期信号的感知） The photoperiodic stimulus in both LDPs and SDPs is perceived not by the stem apex, where the actual change from vegetative to reproductive growth occur, but by the leaves. This has been demonstrated experimentally. For example, SDP cocklebur stripped of all but one leaf could be induced to flower if the remaining leaf were provided the appropriate photoperiod, even when the rest of the plant is exposed to long days. Photoperiodic induction can take place in a leaf that has been separated from the plant. For example, in the SDP Perilla crispa, an excised leaf exposed to short days can cause flowering when subsequently grafted to a noninduced plant maintained in long days (Zeevaart and Boyer 1987). This result indicates that photoperiodic induction depends on events that take place exclusively in the leaf. 实验证明，长日植物与短日植物感受光周期刺激的部位不是茎尖端生长点（从营养生长转变为生 殖生长的发生部位），而是叶片。例如，将短日植物苍耳的叶片去除到只剩一片叶子，将这片叶子用 合适的光诱导周期处理，即使该植物的其他部位处于长日照下，植物仍能开花。光周期诱导还可发生 在离体的叶片上。例如，将一片离体的紫苏（短日植物）叶片用短日照处理后嫁接于一株未诱导的长 日照植物上，可引起后者开花。这个现象表明光周期诱导仅与叶片上发生的反应有关。 11.3.6 Photoperiodic induction（光周期诱导） The photoperiod-regulated processes that occur in the leaves resulting in the transmission of a floral stimulus to the shoot apex are referred to collectively as photoperiodic induction. The appropriate photoperiod is referred to as an inductive treatment. The number of inductive treatments required to induce flowering varies with species. Some plants, such as cocklebur, will proceed to flower even if the plant is returned to unfavorable photoperiods after a single inductive treatment, many other plants require more or less continuous inductive treatments to induce flowering. Induction is not an all-or-none process, but can be achieved in degrees. For example, the flowering of cocklebur can be induced by a single inductive treatment, but the flower initiation can be more rapid and prolific if more inductive treatments are given. 发生在叶片上的反应产生成花物质并传导到茎尖端，这一受光周期调控的过程统称为光周期诱 导。适宜的光周期便是一次诱导处理。开花所需的诱导次数因植物种类而异。有些植物（如苍耳）在 一次诱导处理后，即使被置于不适宜的光周期下也仍能开花，另外一些植物或多或少需要连续几次的 诱导处理才能开花。诱导处理并非一个“全或无”的过程，可以表现为梯度式。如苍耳可以在接受一