Department of Zoology, Arizona State University, 85287-1501, Tempe, Arizona.
J Chem Ecol. 1992 Jun;18(6):915-25. doi: 10.1007/BF00988332.
Perennial plants are thought to respond to partial or complete defoliation by producing new foliage that is less susceptible to herbivores because of induction of allelochemicals. Here, I tested this hypothesis by manually removing primary foliage from branches ofQuercus emoryi (Fagaceae) at two different times in the season and monitoring changes in protein and tannin levels and the amount of herbivory relative to control branches. New, secondary leaves had 2.5 × greater hydrolyzable tannin content than mature foliage of control branches. Condensed tannins, which constitute a relatively low fraction of leaf mass, were lower, while protein content was temporarily greater, in new secondary leaves relative to mature leaves. Despite large increases in hydrolyzable tannins, herbivory levels were greater on refoliated branches than on control branches. New foliage is susceptible to herbivory regardless of when it is produced in the season, possibly because lower toughness and higher water content override any induced or developmentally related changes in allelochemistry. My results do not support the hypothesis that postherbivore changes in phytochemistry protect perennial plants from future herbivory, at least within a growing season.
多年生植物被认为会通过产生新的叶子来应对部分或完全的去叶，因为这些叶子会诱导化感物质，从而减少对食草动物的敏感性。在这里，我通过在季节的两个不同时间手动从Quercus emoryi（壳斗科）的树枝上除去初级叶子，并监测相对于对照树枝的蛋白质和单宁水平以及草食性变化，来测试这个假设。新的次生叶子的可水解单宁含量比对照树枝的成熟叶子高 2.5 倍。构成叶片质量相对较低部分的缩合单宁含量较低，而新次生叶子的蛋白质含量暂时高于成熟叶子。尽管可水解单宁含量大幅增加，但重新长出叶子的树枝上的草食性水平高于对照树枝。新叶子无论在季节的何时产生都容易受到草食性的影响，这可能是因为较低的韧性和较高的含水量超过了任何诱导或发育相关的化感变化。我的结果不支持这样的假设，即在草食动物之后植物化学物质的变化可以保护多年生植物免受未来的草食性侵害，至少在一个生长季节内是这样。
