植物的成花生理ppt課件-在線瀏覽
2025-03-03 22:48本頁面
【正文】 日照植物相反，在中等日照條件下保持營養(yǎng)狀態(tài)，而在較長或較短日照下才能開花。 Representative shortday (a) and longday (b) plants, each grown under shortday (on left) and longday (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 24hour 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 photoperiod36 hours long herewith both long days and long nights. Under these conditions, shomday (longnight) plants bloom, but longday (shortnight) plants do not. 臨界日長和臨界暗期 ? 根據(jù)各種短日植物和長日植物的臨界日長具體的數(shù)值，現(xiàn)在已知道原來以 12h作為短日植物和長日植物的臨界日長的假定是不正確的。因此，如果將短日植物蒼耳和長日植物天仙子同樣放置在 14h日照長度下，這兩種植物將都可以開花。因此，判斷一種植物是長日植物或短日植物，不能以日照長短為準(zhǔn)，必須以臨界日長來判斷。對長日植物來說，日長大于臨界日長，即使是 24h日長都能開花；而對短日植物來說，日長必須小于臨界日長才能開花，然而日長太短也不能開花，可能因光照不足，植物幾乎成為黃化植物之故。 ? 在自然條件下，晝夜總是在 24h的周期內(nèi)交替出現(xiàn)的，因此，和臨界日長相對應(yīng)的就有臨界暗期(critical dark period)。植物開花究竟決定于日長還是夜長 ?例如短日植物開花是因日長縮短還是因暗期延長超過某一限度而引起的呢 ?有報(bào)道認(rèn)為，以短日植物大豆為試驗(yàn)材料，日長為 16h及 4h，暗期為 420h，結(jié)果表明，暗期在 10h以下無花芽分化，暗期長于 10h形成花芽，暗期 1314h花芽最多。由此可見，臨界暗期比臨界日長對開花更為重要。 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 redviolet bars). On the abscissa are 6 h intervals marked. (K. C. HAMNER, 1960) Shortday plants flower only when the photoperiod is less than some critical v
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