《植物的成花生理》PPT课件.ppt

Chapter nine floral physiology of plants,植物的成花生理,植物由营养生长转入生殖生长需要一些特殊的环境条件。无论一年生还是多年生植物，都必须达到生理成熟状态才能感受所要求的环境条件而开花。这种具有感受环境条件而诱导开花的生理状态称为花熟状态(ripeness to floral state)，是植物由营养生长转入生殖生长的标志。 植物开花的顺序：成花诱导(floral induction);成花启动(floral evocation)和花发育(floral development)。在自然状态下，温度和昼夜长度随季节有规律地变化，植物在长期的环境适应和系统进化过程中，形成了对温度和昼夜长度的感应，以顺利完成生活周期。,9.1春化作用(vernalization),9.1.1发现和概念：Cold may affect the flowering response. For example, if winter rye (Secale cereale) is planted in the autumn, it germinates during the winter and flowers the following summer, 7 weeks after growth resumes. If it is planted in the spring, it does not flower for 14 weeks. In 1915, the plant physiologist Gustav Gassner discovered that he could influence the flowering of winter rye and other cereal plants by controlling the temperature of the germinating seeds. He found that if the seeds of the winter strain are kept at near-freezing (1 ) temperatures during germination, the winter rye, even when planted in late spring, will flower the same summer it is planted. This procedure, which came to be known as vernalization (from the Latin vernus, meaning “spring“), is now a common practice in agriculture. 低温诱导促使植物开花的作用，称为春化作用。成花受低温影响的植物，主要是一些二年生植物(如芹菜、胡萝卜、萝卜、葱、蒜、白菜、荠莱、百合、鸢尾、甜菜和天仙子等)和一些冬性一年生植物(如冬小麦、冬黑麦等)。在自然条件下，冬小麦等是在头一年秋季萌发，以营养体过冬，第二年夏初开花和结实。对这类植物来说，秋末冬初的低温就成为花诱导所必需的条件。冬小麦经低温处理后，即使在春季播种也能在夏初抽穗开花。,9.1.2 植物对低温反应的类型,绝对型：二年生和多年生草本植物多属于这类。第一年秋季长成莲座型的营养体，必须经过冬季的低温才能在夏季抽薹开花。 相对型：如冬小麦，低温促进开花；未经过低温处理亦能开花，但营养生长期延长。根据原产地的不同，小麦可分为冬性、半冬性和春性类型。不同类型所要求的低温范围不同，低温时间(春化天数)也不同。一般说来，冬性愈强，要求的春化温度愈低，春化的天数也愈长。 较高温度 或短日处理可使春化作用减弱或消失，这种现象只在低温处理初期才有，称为去春化作用(devernalization)或解除春化。春化作用一旦完成，就非常稳定，高温处理就不起作用。,9.1.3春化的感受部位和传递,接受低温影响的部位是茎尖端的生长点。曾将芹菜种植在高温的温室中，由于得不到花分化所需要的低温，不能开花结实。但是，如果以橡皮管把芹菜茎的顶端缠绕起来，管内不断通过冰冷的水流，使茎的生长点获得低温，就能通过春化，可开花结实。反过来，如把芹菜放在冰冷的室内，而使茎生长点处于高温下，也不能开花结实。 在春化过程中形成一种刺激物质，称为春化素(vernalin)，这种物质还没有从植物体中分离出来，但嫁接试验证明春化素的存在。,经过低温处理开花结果,未经低温处理没有花果,9.1.4 作用机理和应用,9.1.4.1作用机理,9.1.5.2春化过程中的生理生化变化,呼吸速率增强； 核酸代谢加速，在春化过程中核酸（特别是RNA）含量增加，而且RNA性质有所变化； 蛋白质代谢，可溶性Pr及游离AA含量（Pro）增加。 GA含量增加：一些需春化的植物（如天仙子、白菜、胡萝卜等）未经低温处理，若施用GA也能开花。 GA以某种方式代替低温的作用。 9.1.5.3 应用：人工春化处理(如小麦闷种、加速育种进程)；引种调种；控制花期。,9.2光周期现象(photoperiodism),9.2.1发现和概念：The effect of day length on flowering was discovered some seventy years ago by two investigators from the U.S. Department of Agriculture, W.W. Garner and H.A. Allard, who found that neither the Maryland Mammoth variety of tobacco (Nicotiana tabacum) nor the Biloxi variety of soybean (Glycine max) would flower unless the day length was shorter than a critical number of hours. Garner and Allard called this phenomenon photoperiodism. Plants that flower only under certain day-length conditions are said to be photoperiodic. Photoperiodism is a biological response to a change in the proportions of light and dark in a 24 hour daily cycle. 在一天之中，白天和黑夜相对长度的交替变化，称为光周期(photoperiod)。光周期对花诱导有着极为显著的影响。植物对白天和黑夜的相对长度的反应，称为光周期现象(photoperiodism)。,The relative length of day and night determines when plants flower. The four curves depict the annual change of day length in four North American cities at four different latitudes. The horizontal colored lines indicate the effective photoperiod of three different short-day plants. The cocklebur(苍耳), for instance, requires 16 hours or less of light, in Miami, San Francisco, and Chicago, it can flower as soon as it matures, but in Winnipeg(温尼伯湖加拿大中南部), the buds do not appear until early August, so late that the frost will probably kill the plants before the seed is set.,9.2.2 光周期反应类型,长日植物(long-day plant,LDP)：在24h昼夜周期中，日照长度长于一定日数才能成花的植物。延长日照提早开花，延长黑夜推迟开花。如大麦、小麦、黑麦、油菜、菠萝、萝卜、白菜、甘蓝、芹菜、甜菜、胡萝卜、金光菊、山茶、杜鹃、桂花、天仙子等。 短日植物(short-day plant,SDP)：在24h昼夜周期中，日照长度短于一定日数才能成花的植物。延长黑夜或缩短光照提早开花，延长日照推迟开花。如水稻、玉米、大豆、高粱、苍耳、紫苏、大麻、草莓、烟草、菊花、秋海棠、腊梅、日本牵牛。 中日性植物(day-neutral plant)：在任何日照条件下都可以开花的植物。如黄瓜、月季、茄子、番茄、辣椒、菜豆、君子兰、向日葵、蒲公英等。,长短日植物(long-short day plant)：要求先长日后短日的双重日照条件，如芦荟、夜香树等 短长日植物(short-long day plant)：要求先短日后长日的双重日照条件，如风铃草、鸭茅、瓦松、白三叶草等。 中日照植物(intermediate-day plant )：只能在一定的日照长度下才开花，延长或缩短日照都抑制开花，如甘蔗只有在日长12.5 h下才开花。 两极光周期植物(amphophotoperiodism)：与中日照植物相反，在中等日照条件下保持营养状态，而在较长或较短日照下才能开花。如狗尾草。,Representative short-day (a) and long-day (b) plants, each grown under short-day (on left) and long-day (on right) conditions. (a) Chrysanthemum(菊花). (b) Spinach(菠菜) (Spinada oleracea). Note that the plants exposed to long days have longer stems than those exposed to short days, regardless of whether or not they flower.,(a) and (b) Natural 24-hour light/dark cycles must have short nights any time the days are long (summer) and long nights when days are short (winter), so plants could detect season by measuring either day or night. When photoperiodism was first discovered, it was assumed that day length wag important, so all our terminology was based on that.,(c) With electric lights, it is possible to create a long photoperiod-36 hours long here-with both long days and long nights. Under these conditions, shomday (long-night) plants bloom, but long-day (short-night) plants do not.,临界日长和临界暗期,根据各种短日植物和长日植物的临界日长具体的数值，现在已知道原来以12h作为短日植物和长日植物的临界日长的假定是不正确的。例如，美洲烟草和苍耳都是短日植物，但实际上，美洲烟草的临界日长是12h，而苍耳的临界日长则是15.5 h，长日植物如天仙子的临界日长是1l h。因此，如果将短日植物苍耳和长日植物天仙子同样放置在14h日照长度下，这两种植物将都可以开花。苍耳将因14h短于它的临界日照长度(15.5 h)而开花，天仙子也将因14 h长于它的临界日照长度(11 h)而开花。因此，判断一种植物是长日植物或短日植物，不能以日照长短为准，必须以临界日长来判断。临界日长的概念，严格地说，是指昼夜周期中诱导短日植物开花所必需的最长日照或诱导长日植物开花所必需的最短日照。对长日植物来说，日长大于临界日长，即使是24h日长都能开花；而对短日植物来说，日长必须小于临界日长才能开花，然而日长太短也不能开花，可能因光照不足，植物几乎成为黄化植物之故。因此可以说，长日植物是指在日照长度长于临界日长才能正常开花的植物；短日植物是指在日照长度短于临界日长才能正常开花的植物。,在自然条件下，昼夜总是在24h的周期内交替出现的，因此，和临界日长相对应的就有临界暗期(critical dark period)。临界暗期是指在昼夜周期中短日植物能够开花所必需的最短暗期长度，或长日植物能够开花所必需的最长暗期长度。植物开花究竟决定于日长还是夜长?例如短日植物开花是因日长缩短还是因暗期延长超过某一限度而引起的呢?有报道认为，以短日植物大豆为试验材料，日长为16h及4h，暗期为4-20h，结果表明，暗期在10h以下无花芽分化，暗期长于10h形成花芽，暗期13-14h花芽最多。又如长日植物天仙子，在12h日长和12h暗期环境下不开花，但以6h日长和6h暗期处理则开花。由此可见，临界暗期比临界日长对开花更为重要。短日植物实际是长夜植物(long night plant)，长日植物实际是短夜植物(short night plant)。,The soybean was cultivated under cycles of 10 h light and 8 - 62 h of darkness.,Ordinate: Number of Flowers. The maxima are at 10 h light and 14 h darkness and at 10 h light and 30 h darkness (Periods of light are symbolized by light blue, periods of darkness by red-violet bars). On the abscissa are 6 h intervals marked. (K. C. HAMNER, 1960),Short-day plants flower only when the photoperiod is less than some critical value. The common cocklebur (Xanthium strumafium), a short-day plant, requires less than 16 hours of light to flower. Long-day plants flower only when the photoperiod is longer than some critical value. The long-day plant henbane (Hyoscyamus niger) requires about 10 hours (depending on temperature) or more to flower. If the dark period is interrupted by a flash of light, Hyoscyamu will flower even when the daily light period is shorter than 10 hours. However, a pulse of light during the dark period has the opposite effect in a short-day plant-it prevents flowering. The bars at the top indicate the duration of light and dark periods in a 24-hour day.,9.2.3 光周期刺激的感受和传递,接受光周期的部位是叶,仅叶片照光开花,仅生长点照光不开花,仅茎照光不开花,If grafted together and given short days, both short-day plants and day-neutral plants flower. Apparently the floral stimulus that was induced le short-day plant has been transported to, is active in, the day-neutral plant,Under short days, short-day plants are induced to flower but day-neutral ones are not.,光周期传递,9.2.4光对暗期中断的响应,在自然条件下，光周期诱导所要求的光照强度是很微弱的，远远低于光合作用所需要的光照强度。在足以引起短日植物开花的暗期，在接近暗期中间的时候，被个足够强度的闪光所间断，短日植物就不能开花，但长日植物却开了花。短日植物菊花在秋季自然短日下开花，但在花开始诱导时，连续数周每天的午夜照光1 h，就延迟开花。,Cockleburs (adapted to the latitude of Michigan) will flower only if they have been kept in the dark for at least 8.5 hours the critical period. (A and B).,Interruption of red (660 nm) rays prevents flowering.,following by irradiation with far red (730 nm) light,An intense exposure to far red light at the start of the night reduces the dark requirement by 2 hours,Effect of Interference Light,用不同波长的光来间断暗期的试验表明：无论是抑制短日植物开花，还是诱导长日植物开花，都是红光最有效。如果在红光照过之后立即再照以远红光，就不能发生夜间断(night break) 的作用，也就是被远红光的作用所抵消。这个反应可以反复逆转多次，而开花与否决定于最后照射的是红光还是远红光。对短日植物说，红光使植株不开花，而远红光使植株开花；对长日植物说，红光使植株开花，远红光使植株不开花。从以上两个实验看出，在植物花诱导上，光敏