植物生長(zhǎng)物質(zhì)

1、Plant hormones are organic substances that play a major role in regulating growth. Some hormones are produced in one tissue and transported to another tissues, where they produce special physiological responses; others a

2、ct with the same tissues where they are produced. Hormones are active in very small quantity.The word hormone comes from the Greek horman, meaning “to set in motion”. It is now clear, however, that some hormones have in

3、hibitory influences.,7.1生長(zhǎng)素類(auxins),7.1.1發(fā)現(xiàn)和種類7.1.1.1The Darwin Experiments(1880)：?jiǎn)畏较蚬庹?，胚芽鞘向光彎曲；如果切去胚芽鞘的尖端或在尖端套以錫箔小帽，即使是單側(cè)光照也不會(huì)使胚芽鞘向光彎曲。,The Darwins' experiment. (a) Seedlings normally bend toward the light. (b) Wh

4、en the tip of a seedling was covered by a lightproof collar, this bending did not occur, this bending did occur when the tip of a seedling was covered with a transparent collar.) (c) When a lightproof collar was placed b

5、elow the tip, the characteristic lightsponse took place. From these experiments, the Darwins concluded that, in response to light, an "influence" that causes bending is transmitted from the tip of the seedling

6、to the area below the tip where bending normally occurs.,7.1.1.2 Boysen-Jensen's Experiments(1913),背光面插 入云母片,向光面插 入云母片,7.1.1.3 Went experiments(Avena test，燕麥試驗(yàn)法,1926),Went實(shí)驗(yàn)的原始照片(Courtesy of Dr. Kenne

7、th V. Thimann),Auxin的發(fā)現(xiàn)和定名,Bioassay(生物測(cè)定法)：the use of living tissue to determine the amount of a substance. The Avena test soon revealed that substances with auxin activity occur widely in nature. One of the most potent

8、 was first isolated from human urine. It was indole-3-acetic acid (IAA) and turned out to be the auxin actually used by plants.,吲哚乙酸，IAA),具有生長(zhǎng)素活性的生長(zhǎng)物質(zhì),7.1.2生長(zhǎng)素的分布和運(yùn)輸,7.1.2.1分布：生長(zhǎng)素在高等植物中分布很廣，根、莖、葉、花、果實(shí)、種子及胚芽鞘中都有。它的含量甚微，1g

9、鮮重植物材料一般含10～100ng生長(zhǎng)素。生長(zhǎng)素大多集中在生長(zhǎng)旺盛的部分(如胚芽鞘、芽和根尖端的分生組織、形成層、受精后的子房、幼嫩種子等)，而在趨向衰老的組織和器官中則甚少。7.1.2.2化學(xué)狀態(tài)：易于從各種溶劑中提取的生長(zhǎng)素稱為自由生長(zhǎng)素(free auxin)；通過酶解、水解或自溶作用從束縛物釋放出來的那部分生長(zhǎng)素，稱為束縛生長(zhǎng)素(bound auxin）。自由生長(zhǎng)素具有活性，而束縛生長(zhǎng)素則沒有活性。,7.1.2.3 運(yùn)輸,極性

10、運(yùn)輸(polar transport)：生長(zhǎng)素只能從植物體的形態(tài)學(xué)上端向下端運(yùn)輸，而不能向相反方向運(yùn)輸。但是，成熟葉片合成IAA可能通過韌皮部運(yùn)輸。,Characteristics of polar auxin transport in stems, here represented by a segmentof hypocotyl from a seedling. (a) Auxin applied to the apical en

11、d of the hypocotylis transported to the agar block at the basal end of the segment; (b)If the segment is inverted, transport does not take place; (c) transport can take place against a concentration gradient along the s

12、egment.,,Apical end (A),Basal end (B),A,B,B,A,A,B,Agar donor block containing auxin,Donor block,Donor block,Donor block,Receiver block,Receiver block,Receiver block,hypocotyl,,Polar auxin transport,7.1.3生長(zhǎng)素的生物合成和降解,7.1.3

13、.1生長(zhǎng)素的生物合成生長(zhǎng)素在植物體中的合成部位主要是葉原基、嫩葉和發(fā)育中的種子。成熟葉片和根尖也產(chǎn)生生長(zhǎng)素，但數(shù)量很微。生長(zhǎng)素生物合成的前體主要是色氨酸（tryptophan）。色氨酸轉(zhuǎn)變?yōu)樯L(zhǎng)素時(shí)，其側(cè)鏈要經(jīng)過轉(zhuǎn)氨作用、脫羧作用和兩個(gè)氧化步驟。生物合成有4條:吲哚丙酮酸途徑(indole pyruvate pathway); 色胺途徑;3-吲哚乙醇途徑(indole ethanol pathway);吲哚乙腈途徑 7.1.3.

14、2生長(zhǎng)素的降解:酶促降解和光氧化。酶促降解:生長(zhǎng)素的酶促降解可分為脫羧降解(decarboxylated degradation)和不脫羧降解(nondecarboxylated degradation);脫羧降解,IAA氧化酶 光氧化: 體外的吲哚乙酸在核黃素催化下，可被光氧化，產(chǎn)物是吲哚醛(indole aldehyde)和亞甲基羥吲哚。,7.1.4生長(zhǎng)素的生理效應(yīng),7.1.4.1促進(jìn)生長(zhǎng)雙重作用：較低濃度促進(jìn)生長(zhǎng)，較高濃度抑

15、制生長(zhǎng)。不同器官對(duì)生長(zhǎng)素的敏感性不同：根最敏感，依次為芽和莖。對(duì)離體器官的效果高于整體器官。,,,,抑制生長(zhǎng)的IAA數(shù)值,,,,7.1.4.2促進(jìn)不定根的形成,The stalk of the African violet leaf on the left was placed in a solution containing the synthetic auxin naphthalene acetic acid (NAA) for

16、 10 days before the picture was taken. The stalk of the leaf on the right was placed in pure water. Note the growth of adventitious roots on the stalk of the hormone-treated leaf.,Adventitious root,No adventitious root,7

17、.1.4.3對(duì)養(yǎng)分的調(diào)運(yùn)作用,,,,,,,,,,7.1.4.4其它作用,促進(jìn)雌花增加，單性結(jié)實(shí)，子房壁生長(zhǎng)，細(xì)胞分裂，維管束分化，光合產(chǎn)物分配，葉片擴(kuò)大，莖伸長(zhǎng)，偏上性生長(zhǎng)，乙烯產(chǎn)生，葉片脫落，形成層活性，傷口愈合，不定根形成，種子發(fā)芽，側(cè)根形成，根瘤形成，種子和果實(shí)生長(zhǎng)，座果，頂端優(yōu)勢(shì)。抑制花朵脫落；側(cè)枝生長(zhǎng)，塊根形成，葉片衰老。,7.1.5 作用機(jī)理：細(xì)胞壁酸生長(zhǎng)學(xué)說(acid growth hypothesis)和基因調(diào)節(jié)學(xué)說

18、(Auxin regulatory hypothesis),,細(xì)胞壁酸化的過程,,基因調(diào)節(jié)過程,,Ca 2+或IP3等信號(hào),Cells in the subapical region have auxin receptors. If the apex is growing and producing auxin, IAA is present to bind to the receptors (a). After stimulation

19、 by auxin binding, the plasma membrane pumps protons from the cytoplasm into the wall (b), weakening it and allowing turgor pressure to stretch it. (c) Cell elongation stops once the maximum cell size is reached, and add

20、ing more auxin does not cause any more elongation; perhaps the receptors have been removed from the membrane.,IAA引起細(xì)胞壁酸化,Hormone response pathways. Hormones act by binding to proteins called receptors.The hormone signals

21、 are often amplified and passed down biochemical pathways by intermediary compounds called second messengers. Many responses to plant hormones are mediated through changes in gene expression within the nucleus. Specific

22、genes are switched on or off as a result of hormone action. Hormones ultimately affect cell growth by causing changes in the architecture and chemical properties of the cell wall.,7.2赤霉素類(gibberellins,GAs),7.2.1發(fā)現(xiàn)和種類：192

23、6年日本人黑澤英一(Kurosawa L) 從水稻惡苗病(foolish seeding disease)研究中發(fā)現(xiàn)的?；紣好绮〉牡局臧l(fā)生徒長(zhǎng)，是由赤霉菌分泌出來的物質(zhì)引起的。赤霉素的名稱由此而來。1938年日本人數(shù)田貞次郎(Yabuta)和住木(Sumiki)等從水稻赤霉菌中分離出赤霉素A和B兩種結(jié)晶，但這項(xiàng)研究在第二次世界大戰(zhàn)爆發(fā)后即被迫停頓。后經(jīng)過英美科學(xué)家研究獲得赤霉素化學(xué)結(jié)構(gòu)?，F(xiàn)已發(fā)現(xiàn)126種。,7.2.2赤霉素的分布和運(yùn)輸,

24、赤霉素廣泛分布于被子植物、裸子植物；蕨類植物、褐藻、綠藻、真菌和細(xì)菌中。赤霉素和生長(zhǎng)素一樣，較多存在于植株生長(zhǎng)旺盛的部分，如莖端、嫩葉、根尖和果實(shí)種子。高等植物的赤霉素含量一般是1-1000ng/g鮮重，果實(shí)和種子(尤其是未成熟種子)的赤霉素含量比營(yíng)養(yǎng)器官的多兩個(gè)數(shù)量級(jí)。每個(gè)器官或組織都含有2種以上的赤霉素，而且赤霉素的種類、數(shù)量和狀態(tài)(自由態(tài)或結(jié)合態(tài))都因植物發(fā)育時(shí)期而異。赤霉素在植物體內(nèi)的運(yùn)輸沒有極性。根尖合成的赤霉素沿導(dǎo)管向上

25、運(yùn)輸，而嫩葉產(chǎn)生的赤霉素則沿篩管向下運(yùn)輸。,7.2.3 生物合成,赤霉素在高等植物中生物合成的位置至少有3處：發(fā)育著的果實(shí)(或種子)，伸長(zhǎng)著的莖端和根部。赤霉素在細(xì)胞中的合成部位是微粒體、內(nèi)質(zhì)網(wǎng)和細(xì)胞質(zhì)可溶性部分等處。合成前體：甲瓦龍酸(甲羥戊酸) 。,7.2.4赤霉素的生理效應(yīng),7.2.4.1促進(jìn)莖的伸長(zhǎng)生長(zhǎng)：主要是促進(jìn)整株和節(jié)間的伸長(zhǎng)，并且沒有閾值。,Figure note：The plant on the right was

26、treated with gibberellin; the one on the left served as a control. The plants are Contender beans, a dwarf cultivar of the common bean(Phaseolus vulgaris).,,(a) Many biennial plants grow as a rosette in their first year,

27、 then elongate rapidly (bolt) in their second year, producing a tall shoot that bears numerous flowers. The bolting is controlled by gibberellic acid; if it is absent, the plants remain short . (b) In crop plants, havin

28、g tall stalks often makes harvesting difficult, and it is a waste of energy in fields where there is no competition for light. Plant breeders often artificially select mutant plants that are dwarfed or short. Many of the

29、se dwarf forms either lack the particular gibberellin needed lot stem elongation or are unresponsive to it, perhaps because they lack the proper receptors.,矮玉米,矮玉米＋GA,常規(guī)玉米,常規(guī)玉米+GA,,,,,7.2.4.2誘導(dǎo)開花：代替低溫促進(jìn)開花,Bolting in cabb

30、age (Brassica oleracea var. capitata) occurring naturally (left) and induced by gibberellin treatment (right). The plant on the right was treated once a week for eight weeks.,抽薹開花,,,7.2.4.3 打破休眠,可促進(jìn)馬鈴薯提前發(fā)芽，主要是GA誘導(dǎo)淀粉酶的活性。

31、,GA誘導(dǎo)淀粉酶的產(chǎn)生，促進(jìn)種子萌發(fā),7.2.4.4促進(jìn)果實(shí)發(fā)育,In the United States, large amounts of gibberellic acid are applied annually to the Thompson Seedless grapes, a cultivar of Vitis vinifera. Treatment causes larger fruit and much looser c

32、lusters.,1.單性結(jié)實(shí),2.養(yǎng)分調(diào)運(yùn),3.促進(jìn)坐果,GA3 treatment,control,7.2.5GA的作用機(jī)理,protein,tryptophan,Auxin,Oxidative products,GA,,蛋白酶,IAA氧化酶,,,,,,,7.3 Cytokinins(細(xì)胞分裂素),7.3.1發(fā)現(xiàn)和種類：1948～55年F.Skoog和崔澂等培養(yǎng)煙草髓部組織時(shí)，偶然向培養(yǎng)基中加入放置很久的鯡魚精子DNA，髓部細(xì)胞分裂

33、就加快；如加入新鮮的DNA，則完全無效。從DNA降解物中分離出6-呋喃氨基嘌吟(6-furfuryl amino purine)，它能促進(jìn)細(xì)胞分裂，被命名為激動(dòng)素(kinetin，KT)。,天然細(xì)胞分裂素可分為兩類：游離態(tài)和結(jié)合態(tài)。游離的細(xì)胞分裂素。前者共20多種，包括玉米素(zeatin，Z)、玉米素核苷(zeatin riboside，[9R]Z)、二氫玉米素(dihydrozeatin，[diH]Z）、異戊烯基腺苷(isopent

34、enyl adenosine，[9R]iP)。后者包括異戊烯基腺苷、玉米素核苷、甲硫基異戊烯基腺苷、甲硫基玉米素核苷，常與RNA結(jié)合。,7.3.2分布和運(yùn)輸,高等植物的細(xì)胞分裂素主要存在于進(jìn)行細(xì)胞分裂的部位，如莖尖、根尖、未成熟的種子、萌發(fā)的種子和生長(zhǎng)著的果實(shí)等。 細(xì)胞分裂素在植物體內(nèi)的運(yùn)輸，主要是從根部合成處通過木質(zhì)部運(yùn)到地上部，少數(shù)在葉片合成的細(xì)胞分裂素也可能從韌皮部運(yùn)走。,7.3.3生物合成,細(xì)胞分裂素生物合成是在細(xì)胞的微粒體中

35、進(jìn)行的。 細(xì)胞分裂素的生物合成有兩條途徑：由tRNA水解產(chǎn)生和從頭合成。第一條途徑是次要的，第二條途徑是主要的。高等植物的細(xì)胞分裂素是從頭直接合成的。細(xì)胞分裂素的前體是甲瓦龍酸。,7.3.4生理效應(yīng),7.3.4.1促進(jìn)細(xì)胞分裂：主要促進(jìn)細(xì)胞質(zhì)分裂，IAA促進(jìn)細(xì)胞核的分裂，GA主要是縮短了細(xì)胞周期中的G1和S期。,7.3.4.2促進(jìn)芽的分化(CTK/IAA比值),7.3.4.3促進(jìn)側(cè)芽發(fā)育,(a) Many cacti show al

36、most 10096 apical dominance; as long as the apex is undamaged, all axillary buds (spine clusters) remain dormant. Here, one bud has become active but is now producing enough auxin to keep its own buds dormant and suppres

37、s nearby buds on the parent stem. (b) The concentration of auxin is greatest at the shoot apex and less at lower levels; at sites where it drops below the threshold level, it can no longer suppress axillaly buds, and one

38、 or several become active. Other factors must be involved, because it is not always thelowest bud that becomes active first, even though it should be the first to encounter sufficiently low auxin concentrations.,消除頂端優(yōu)勢(shì),A

39、pical dominance in Nicotiana.,Lateral bud break in similar plant after top as removed.,,,7.3.4.4延緩葉片衰老,延緩葉綠素和蛋白質(zhì)的降解速率，穩(wěn)定多核糖體，抑制DNA酶、RNA酶和蛋白酶的活性，保持膜的完整性。,保綠,保綠,衰老發(fā)黃,衰老發(fā)黃,,,,,,7.4乙烯(ethylene),7.4.1發(fā)現(xiàn)和結(jié)構(gòu)：Ethylene was known

40、to have effects on plants long before the discovery of auxin. The “botanical” history of ethylene, a simple hydrocarbon, goes back to the 1800s, when city streets were lighted with lamps that burned illuminating gas. In

41、Germany, illuminating gas leaking from gas mains was founded to cause defoliation of shade trees along the streets. In 1901,Dimitry Neljubov, a plant physiologist of Russia, demonstrated that ethylene was the active comp

42、onent of illuminating gas. He noticed that exposure of pea seedlings to illuminating gas caused stems to grow in a horizontal direction.H2C=CH2,7.4.2分布和運(yùn)輸,高等植物各器官都能產(chǎn)生乙烯，但不同組織、器官和發(fā)育時(shí)期，乙烯的釋放量是不同的。例如，成熟組織釋放乙烯較少，一般為0.01～10n

43、l/g鮮重·h-1，分生組織、種子萌發(fā)、花剛凋謝和果實(shí)成熟時(shí)產(chǎn)生乙烯最多，某些真菌（青霉菌、鐮刀菌、酵母菌、毛霉)和細(xì)菌(大腸桿菌)也產(chǎn)生較多的乙烯。,7.4.3乙烯的生物合成,S-腺苷蛋氨酸 (S-adenosylmethionine,SAM),L-蛋氨酸(L-methionine),1-氨基環(huán)丙烷-1-羧酸(1-aminocyclopropane-1-carboxylic acid,ACC,簡(jiǎn)稱丙二酰基),乙烯(ethyl

44、ene),,,,,,,,7.4.4乙烯的生理效應(yīng),7.4.4.1改變生長(zhǎng)習(xí)性：三重反應(yīng)(triple response)，即抑制伸長(zhǎng)生長(zhǎng)(矮化)，促進(jìn)橫向生長(zhǎng)(加粗)，地上部失去負(fù)向重力性生長(zhǎng)（偏上生長(zhǎng)，器官的上部生長(zhǎng)速度快于下部)。,Ethylene treatment of seedlings promotes hook closure and stem thickening rather than elongation. Thes

45、e etiolated pea seedlings were treated with 0, 0.1 and 1 ppm ethylene (left to right),豌豆的偏上生長(zhǎng),黃瓜偏上生長(zhǎng)使黃瓜攀緣而上。,,,ETH和GA對(duì)生長(zhǎng)作用的比較,側(cè)向擴(kuò)展,,縱向擴(kuò)展,,7.4.4.2促進(jìn)成熟,驟變型果實(shí)（香蕉、番茄、蘋果等)在呼吸驟變前用乙烯處理，可以催熟果實(shí)。非驟變型果實(shí)(柑橘、橙等)亦有同樣效果。乙烯促進(jìn)果實(shí)成熟的原因可能是：

46、增強(qiáng)質(zhì)膜的透性，加速呼吸，引起果肉有機(jī)物的強(qiáng)烈轉(zhuǎn)化。,7.5脫落酸(abscisic acid，ABA),7.5.1發(fā)現(xiàn)、種類和化學(xué)結(jié)構(gòu)：是指能引起芽休眠、葉子脫落和抑制生長(zhǎng)等生理作用的一類激素。1964年,Frederic T. Addicott等從將要脫落的末成熟的棉桃中，提取出—種促進(jìn)棉桃脫落的激素，命名為脫落素(abscisin)。另外，英國(guó)Paul F. Wareing等(1963)從槭樹脫落的葉子中提取出一種促進(jìn)芽休眠的

47、激素，命名為休眠素(domin)。后來證明，脫落素和休眠素是同一物質(zhì)。1967年在第六屆國(guó)際生長(zhǎng)物質(zhì)會(huì)議上統(tǒng)一稱之為脫落酸（abscisic acid，ABA)。,7.5.2 ABA生物合成,高等植物的ABA生物合成是通過胡蘿卜素途徑(又稱C40途徑)，即由甲瓦龍酸經(jīng)胡蘿卜素進(jìn)一步轉(zhuǎn)變而成的。,甲瓦龍酸,異戊烯基焦磷酸,赤霉素,細(xì)胞分裂素,胡蘿卜素,脫落酸,,,,,,,,7.5.3 ABA的生理效應(yīng),7.5.3.1促進(jìn)脫落：(a) A

48、healthy leaf produces and transports enough auxin to suppress activity in the abscission zone (b) A damaged leaf produces less auxin, insufficient to prevent abscission (c) Autumn stimuli may cause the production of ethy

49、lene, which then suppresses auxin synthesis and transport. An alternative hypothesis postulates that autumn conditions directly suppress auxin production and ethylene is not necessary.,7.5.3.2 促進(jìn)氣孔關(guān)閉,ABA會(huì)增加胞質(zhì)Ca2+濃度和胞質(zhì)溶膠P

50、H，一方面抑制保衛(wèi)細(xì)胞質(zhì)膜上的內(nèi)向K+通道蛋白活性，抑制外向K+通道蛋白活性，保衛(wèi)細(xì)胞內(nèi)K+濃度減少；與此同時(shí)，ABA活化外向Cl-通道蛋白，Cl-外流，保衛(wèi)細(xì)胞時(shí)Cl-濃度減少，保衛(wèi)細(xì)胞膨壓就下降，氣孔關(guān)閉。,7.5.3.3 促進(jìn)休眠,脫落酸能促進(jìn)多種多年生木本植物和種子休眠。將脫落酸施用到紅醋栗或其他木本植物生長(zhǎng)旺盛的小枝上，會(huì)產(chǎn)生類似休眠的一般征狀，如節(jié)間縮短，營(yíng)養(yǎng)葉變小，頂端分生組織的有絲分裂減少，形成了休眠芽，并造成下面某些葉