不久前,美国弗吉尼亚大学及其他一些单位的研究人员通过一系列的观察和研究证明,轻旱有助于植物抵御害虫的侵袭。他们观察到蚕豆叶甲的幼虫进食时,总是挑选富含水分的植物叶片,而对在较干旱环境下生长的植物叶片则不喜欢吃。当没有选择余地而不得不进食含水分较少的叶片时,蚕豆叶甲的幼虫生长缓慢,而且其成虫也较弱小。这表明不仅因为叶片含水量低而更加坚韧,难于啃食,而且在较干旱环境下生长的植物所产生的化学防御物质也在起作用。为了证实这一观点,研究人员先将在较干旱环境中生长的植物浇透水,使其 Not long ago, researchers at the University of Virginia and several other institutes in the United States demonstrated through a series of observations and studies that drought alleviation helps plants to withstand pests. They observed that when the larvae of Vicia faba were fed, they always picked leaves of plants that were rich in water, but did not like to eat leaves of plants that grew in arid environments. When there is no choice but to eat leaves with less water, Larvae larvae grow slowly and their adults are also weaker. This shows that chemical defenses produced by plants grown in drier environments are also working, not only because of the low moisture content of the leaves, but also because they are tough to eat. To confirm this view, researchers drenched plants grown in arid environments to water