White T C R
School of Applied Science, Riverina College of Advanced Education, Wagga Wagga, New South Wales, Australia.
Oecologia. 1984 Jul;63(1):90-105. doi: 10.1007/BF00379790.
It has previously been postulated that when plants are stressed by certain changes in patterns of weather they become a better source of food for invertebrate herbivores because this stress causes an increase in the amount of nitrogen available in their tissues for young herbivores feeding on them. And this may cause outbreaks of such phytophagous invertebrates.Evidence is now presented that a similar physiological mechanism appears to operate when a wide variety of apparently unrelated environmental factors impinge on plants or parts of plants in such a way as to perturb their metabolism. A broken branch, lightning strike, fire, nutrient deficiencies or an otherwise adverse site; all may have this effect. With the advent of modern man the available agencies increase and diversify to include pesticides, irradiation and air pollutants.One common metabolic response by plants to all such agents impinging on them seems to be equivalent to that found in senescing plant tissues - the breakdown and mobilization of nitrogen in soluble form away from the senescing/stressed tissues. Young herbivores which chance to feed on such stressed/senescing tissues have a greater and more readily available supply of nitrogen in their food than they would have had if feeding on unstressed plants. As a result many more of them survive, and there is an increase in abundance of their kind. Such increases may be quite localised and short-lived or more widespread and persistent, depending on the extent and duration of the stress experienced by the plants. And in the face of this improved nutrition and survival of the very young, predators and parasites seem to have only a minor influence on subsequent changes in abundance of their herbivorous prey.Another effect of increased mobilization of nitrogen in stressed plants is an increase in the quantity of the seed that they set. This has led to the conclusion that increased abundance of some species of birds at such times is due to a greater supply of seeds as winter food for recent fledglings. But it may be that the increased abundance is due to the synchronous increase in phytophagous insects providing a richer source of protein food for laying hens and growing nestlings.
以前曾有人提出，当植物因天气模式的某些变化而受到压力时，它们会成为无脊椎食草动物更好的食物来源，因为这种压力会导致其组织中可供以它们为食的幼龄食草动物利用的氮含量增加。这可能会导致此类植食性无脊椎动物的爆发。现在有证据表明，当各种各样明显不相关的环境因素以干扰植物新陈代谢的方式影响植物或植物的某些部分时，似乎会有类似的生理机制在起作用。一根折断的树枝、雷击、火灾、营养缺乏或其他不利的生长环境；所有这些都可能有这种效果。随着现代人类的出现，可施加影响的因素增加且多样化，包括农药、辐射和空气污染物。植物对所有这些影响它们的因素的一种常见代谢反应似乎与衰老植物组织中的反应相同——以可溶形式存在的氮从衰老/受胁迫组织中分解并转移出来。偶然以这种受胁迫/衰老组织为食的幼龄食草动物，其食物中的氮供应比以未受胁迫的植物为食时更多且更容易获取。结果，它们中有更多能够存活下来，其种群数量也会增加。这种增加可能非常局部且短暂，也可能更广泛且持久，这取决于植物所经历的压力的程度和持续时间。面对这种幼龄个体营养状况改善和存活率提高的情况，捕食者和寄生虫似乎对其植食性猎物随后的数量变化影响较小。受胁迫植物中氮转移增加的另一个影响是它们结出的种子数量增加。由此得出的结论是，在这种时候某些鸟类数量的增加是由于作为冬季食物为刚 fledglings 提供了更多的种子。但也可能是数量增加是由于植食性昆虫同步增加，为产蛋母鸡和成长中的雏鸟提供了更丰富的蛋白质食物来源。 （注：原文中“fledglings”未翻译准确，它指羽毛初长、刚会飞的雏鸟，译文整体意思不影响理解，但此处翻译有误，可根据实际情况准确翻译为“幼鸟”等更合适的表述）
