高级植物生理学课件第七章植物的生殖生理.ppt
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1、1,Plant Reproduction,Zichao Mao,2,Life cycle of plant,3,4,Transition to reproduction,Vegetative phase,Reproductive phase,?,Inflorescence,Flower,5,Production of flowers involves two transitions in Arabidopsis,SC: stem cell P: organ primordia Se: sepal,Convert SAM (Shoot Apical Meristem) to infloresce
2、nce meristem (infinite, making lateral organs) 2. Convert inflorescence meristem to floral meristem (terminal, flowers),6,Factors regulating the transitions,Vegetative meristem,Inflorescence meristem,Floral meristem,Genes (flowering-time genes and floral identity genes) Light (photoperiod) The biolo
3、gical clock Temperature Hormones,7,affecting the transition of vegetative growth to reproductive growth,WT,emf2,Flowering-time genes,emf1,embryonic flower,8,affecting formation of inflorescence and floral meristems,Floral identity genes,Inflorescence (from Inflorescence meristem),Flower (from Floral
4、 meristem),9,terminal flower 1 (tfl1): Convert the inflorescence meristem to the flower meristem.,leafy (lfy): produce more inflorescences, delayed flowering,Mutations in floral identity genes,tfl1,FUNCTION Controls inflorescence meristem identity and is required for maintenance of a indeterminate i
5、nflorescence. Prevents the expression of APETALA1 and LEAFY. Also plays a role in the regulation of the time of flowering in the long-day flowering pathway. May form complexes with phosphorylated ligands by interfering with kinases and their effectors Expressed below the apical dome of inflorescence
6、 and coflorescence meristems, and in inflorescence stem. Weakly expressed in vegetative phase from day 2 or day 3. Increased expression after commitment to flowering from day 7 on.,LEAFY;,LFY, FUNCTIONS IN: chromatin DNA binding, transcription factor activity, sequence-specific DNA binding; INVOLVED
7、 IN: flower development, maintenance of inflorescence meristem identity, response to gibberellin stimulus, gibberellic acid mediated signaling; LOCATED IN: nucleus; EXPRESSED IN: shoot apex, leaf whorl, embryo, flower, seed; EXPRESSED DURING: 7 growth stages;,12,Factors regulating the transition to
8、reproduction,Vegetative meristem,Inflorescence meristem,Floral meristem,EMF,TF1,LFY,13,Garner and Allard (1920s),The discovery of photoperiodism,Soybeans (Glycine max) planted over a three-month period all flowered about the same time,14,Many more experiments were followed: Eliminate a variety of en
9、vironmental conditions: Nutrition, temperature, and light intensity Relative length of day and night decides the flowering time,Photoperiodism: ability of an organism to measure the proportion of daylight during a 24-hour period,15,Varies according to the latitude and seasonal changes.,Photoperiod,1
10、6,Critical daylength,Critical Daylength (CD),Xanthium(苍耳): a short day plant, flowers when CD is LESS than 15.5 hours. Hyoscyamus(茛菪 ): a long day plant, flowers when CD is MORE than 11 hours.,17,Plants are induced to flower by different photoperiods,short day (SD) : plants are stimulated to flower
11、when the length of day falls below a threshold long day (LD): plants are stimulated to flower when the length of day exceeds a threshold Day neutral (DN): plants flower indifference to the changes of day length. Long-short-day: flowering requires certain number of short days are preceded by a certai
12、n number of long days. Short-long-day: flowering requires certain number of long days are preceded by a certain number of short days. Intermediate-daylength: not flowering if the daylength is too short or too long.,Plants that respond to lengthening days and flower in the spring or early summer are
13、known as long-day (LD) plants. Short-day (SD) plants flower in the late summer or autumn in response to shortening days and lengthening nights,19,Do plants really measure the length of the daylength?,20,Xanthium flowers when the dark period exceeds 8.5 hours.,Hamner and Bonner (1938): Xanthium strum
14、arium(苍耳), a SD plant with CD = 15.5 hours,Short interruption of dark period, even by a pulse of light as short as 1 minute delays flowering. The relative length of dark is not the determining factor.,21,Similar results were obtained with other SD plants.,For LD plants A longer dark period inhibits
15、flowering. Light break induces flowering.,22,What tissues/organs perceive photoperiod?,23,Exp. 1: The leaf or apex of Perilla(紫苏 ) (a short day plant) was exposed to different daylength.,24,Exp. 2: Grafting experiment with Perilla,25,the flowering signal is generated in the leaf the signal goes one
16、way: from the leaf to the apex Grafting transmittable,The flowering signal: florigen,?,vegetative or reproductive growth?,SAM,Florigen,Florigen,Florigen,Recent studies in Arabidopsis and rice have made a strong case that florigen, or at least acomponent of the floral stimulus, is the floral integrat
17、or FT. The FT gene is expressed in leaves, and the protein travels to the meristem where it interacts with another integrator, FD, to initiate the floral transition FT-like genes ( FD, FVE, FCA, FY, and FPA) are ubiquitous in plants and have been found to regulate flowering in a variety of species i
18、ncluding wheat and poplar,The role of phytochrome in de-etiolation response,Phytochrome: a molecular switching mechanism,The effect of light on the biological clock,Phytoperiodism and control of flowering Short-day plant: required a light period shorter than a critical length to flower long-day plan
19、t: required a light period longer than a critical length to flower Day-neutral plant: unaffected by photoperiod and flower when reaching a certain stage of maturity Vernalization: use of pretreatment with cold to induce flowering,32,The Arabidopsis biological clock,The central oscillator: CCA1, LHY,
20、 and TOC1 (these are transcription factors) and other proteins,33,Present in plants, animals, fungi, and some photosynthetic bacteria An internal time measuring system (“clock”) that runs on its own with a periodicity of nearly 24 hours. It can be “reset” by external signals.,The biological clock,Bi
21、ological clocks and circadian rhythms,36,The Arabidopsis biological clock,CCA1 and LHY are expressed during the day and together repress expression of TOC1 during the day,TOC1 is expressed at night and is required for activation of CCA1 and LHY1, beginning just before morning,37,Lack of the nyctinas
22、tic movement: diurnal rise and fall of leaves Altered flowering time in some mutants cca1: early flowering lhy: early flowering toc1: early flowering Some other clock mutants can be late flowering,Mutations in the clock genes,38,Temperature: Vernalization,Vernalization: low temperature treatment can
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