英国科学家日前发现，一些植物之所以在秋天变红，很可能是为了躲避害虫侵害。
伦敦帝国学院托马斯·多雷博士和吉姆·哈迪教授在实验中用了70种不同颜色对比秋天在植物上产卵的蚜虫更偏爱其中哪一类颜色。结果发现，蚜虫对红色系的叶子最不感兴趣，而黄色叶子对蚜虫的吸引力则大得多。
多雷分析说，植物叶片变红是因为花青素的作用，而变黄是叶绿素分解、叶黄素和胡萝卜素颜色显现造成的。并不是所有植物叶子都在秋天变红，这是因为“如果（这个品种）被昆虫袭击的可能性较大，可能造成的损失大于在秋天制造花青素的代价，植物会选择变红。而如果感染虫害的可能性较低，植物就会保持黄色”。
多雷说，昆虫的眼睛并不能分辨红色，但实验结果证明红色对于蚜虫确实具有防御功效，这让他感到“非常困惑”。
这项研究成果发表在最新一期英国《皇家学会学报B》（Proceedings of the Royal Society B）上。（生物谷Bioon.com）
生物谷推荐原始出处：
Proceedings of the Royal Society B，DOI：10.1098/rspb.2008.0858，Thomas F. D?ring，Jim Hardie
Autumn leaves seen through herbivore eyes
Thomas F. D?ring1, 2, Marco Archetti3, Jim Hardie1
1Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, UK
2 School of Biological and Chemical Sciences, Queen Mary, University London, London E1 4NS, UK
3Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
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.
