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starseacow專家顧問 (職業(yè)作家)
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[交流]
葉子為什么會(huì)在脅迫或衰老情況下失綠變黃 已有8人參與
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與蟲友交流一個(gè)問題:葉子為什么會(huì)在脅迫或衰老情況下失綠變黃 眾所周知,在這一過程中,葉綠素降解,而一些其他色素(如葉黃素,花青素之類)還存在,因此葉片呈現(xiàn)黃色或紅色。那么,這一過程中究竟發(fā)生了什么?為什么植物進(jìn)化出這樣一種生理反應(yīng)?這種生理反應(yīng)對(duì)植物有什么意義? 希望做相關(guān)研究或感興趣的蟲友能夠談?wù)勀愕目捶? |

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專家經(jīng)驗(yàn): +426 |
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拋磚引玉,提供一篇有趣的論文: 一些植物之所以在秋天變紅,很可能是為了躲避害蟲侵害 Autumn leaves seen through herbivore eyes Thomas F Döring, Marco Archetti and Jim Hardie Proc. R. Soc. B 2009 276, 121-127 Why leaves of some trees turn red in autumn has puzzled biologists for decades, as just before leaf fall the pigments causing red coloration are newly synthesized. One idea to explain this apparently untimely investment is that red colour signals the tree’s quality to herbivorous insects, particularly aphids. However, it is unclear whether red leaves are indeed less attractive to aphids than green leaves. Because aphids lack a red photoreceptor, it was conjectured that red leaves could even be indiscernable from green ones for these insects. Here we show, however, that the colour of autumnal tree leaves that appear red to humans are on average much less attractive to aphids than green leaves, whereas yellow leaves are much more attractive. We conclude that, while active avoidance of red leaves by aphids is unlikely, red coloration in autumn could still be a signal of the tree’s quality, or alternatively serve to mask the over-attractive yellow that is unveiled when the green chlorophyll is recovered from senescing leaves. Our study shows that in sensory ecology, receiver physiology alone is not sufficient to reveal the whole picture. Instead, the combined analysis of behaviour and a large set of natural stimuli unexpectedly shows that animals lacking a red photoreceptor may be able to differentiate between red and green leaves. |

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如果是植物主動(dòng)調(diào)節(jié),能否認(rèn)為是為了降低蒸騰作用的水分散失?干旱脅迫葉片變黃,呼吸作用、光合作用都降低,水分缺失葉片表面氣孔關(guān)閉,有些會(huì)永久性損傷,自由基活性氧等在葉片內(nèi)失去平衡,葉片組織有序死亡,體現(xiàn)為葉片凋零 轉(zhuǎn)帖: 花卉出現(xiàn)黃葉,視其發(fā)生特點(diǎn),有以下幾種情況: 一是水黃。因澆水過勤引起,其特點(diǎn)是老葉無明顯變化、幼葉變黃;此應(yīng)立即控水; 二是旱黃。因缺水、干旱引起,其特點(diǎn)是自下而上老葉先黃,若缺水時(shí)間稍長,則會(huì)全株黃葉,甚至死亡,應(yīng)及時(shí)澆水; 三是肥黃。因施肥過勤或濃度過高引起;特點(diǎn)是幼葉肥厚,有光澤,且凹凸不平;應(yīng)控肥、中耕、澆水; 四是餓黃。因肥料不足、施肥濃度偏低,且施肥間隔時(shí)間過長而引起;其特點(diǎn)為幼葉、嫩莖處先黃,如見此現(xiàn)象后不及時(shí)施肥,也會(huì)造成全株黃葉甚至死亡;對(duì)缺肥的花卉,切忌一次大量施用濃肥,以免造成燒根; 五是缺鐵性黃葉。溫室中木本花卉等,由于土壤肥力條件變化大,常會(huì)出現(xiàn)黃葉現(xiàn)象,特點(diǎn)是幼葉明顯,老葉較輕,葉肉黃色,葉脈綠色,并形成典型網(wǎng)絡(luò);可施用硫酸亞鐵水溶液來解決,其方法為:餅肥7份,硫酸亞鐵5份,水200份配成倍液澆之。 |

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