高級(jí)植物生理學(xué)課件第七章植物的生殖生理-展示頁(yè)
2025-01-25 01:26本頁(yè)面
【正文】 length of the daylength? 20 ? Xanthium flowers when the dark period exceeds hours. Hamner and Bonner (1938): Xanthium strumarium(蒼耳） , a SD plant with CD = 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 flowering. Light break induces flowering. 22 What tissues/ans perceive photoperiod? 23 Exp. 1: The leaf or apex of Perilla（ 紫蘇 ） (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 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 aponent of the floral stimulus, is the floral integrator 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 ? FTlike genes ( FD, FVE, FCA, FY, and FPA) are ubiquitous in plants and have been found to regulate flowering in a variety of species including wheat and poplar The role of phytochrome in deetiolation response Phytochrome: a molecular switching mechanism The effect of light on the biological clock ?Phytoperiodism and control of flowering ?Shortday plant: required a light period shorter than a critical length to flower ?longday plant: required a light period longer than a critical length to flower ?Dayneutral 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, 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 Temperature Biological 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 nyctinastic 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 M
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