高級植物生理學 課件 第七章 植物的生殖生理-文庫吧
2025-01-01 01:26 本頁面
【正文】 during a 24hour period 15 Varies according to the latitude and seasonal changes. Photoperiod 16 Critical daylength Critical Daylength (CD) Xanthium(蒼耳） : a short day plant, flowers when CD is LESS than 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 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. ? Longshortday: flowering requires certain number of short days are preceded by a certain number of long days. ? Shortlongday: flowering requires certain number of long days are preceded by a certain number of short days. ? Intermediatedaylength: 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 known as longday (LD) plants. Shortday (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 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 t
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