Stock W D, Le Roux D, Van der Heyden F
Department of Botany, University of Cape Town, Private Bag, 7700, Rondebosch, South Africa.
Oecologia. 1993 Dec;96(4):562-568. doi: 10.1007/BF00320514.
Allocation of carbon to chemical defences has often been suggested to be a direct response to browsing or grazing by herbivores. This study quantitatively compares total polyphenol and tannin production in response to simulated browsing of three karoo shrubs in order to test this induced defence hypothesis. The three species studied responded to browsing either by rapid regrowth or by increasing polyphenol production in the remaining tissues. The patterns did not follow any phylogenetic relationships but were weakly associated with the palatability of each species. The highly palatable deciduous species Osteospermum sinuatum, which is capable of rapid regrowth, showed no or very low levels of constitutive and browsing-induced total polyphenols, condensed tannins and protein-precipitating tannins. The evergreen sclerophyllous species Pteronia pallens showed a limited regrowth capacity and had intermediate levels of polyphenols, while the evergreen succulent species Ruschia spinosa showed almost no regrowth over the study period. R. spinosa contained the highest constitutive and browsing-induced levels of polyphenols, condensed tannins and protein-precipitating tannins. In two of the species more than one anti-herbivore defence feature co-occur. P. pallens foliage contains both hepatotoxins and polyphenols while R. spinosa has both structural (spines) and chemical defences. Responses of karoo shrubs to simulated browsing are interpreted as the result of passive alterations in plant chemistry rather than as an active defence response to herbivores.
碳分配到化学防御中，通常被认为是对食草动物啃食或放牧的直接反应。本研究定量比较了三种卡鲁灌木在模拟啃食情况下总多酚和单宁的产量，以检验这种诱导防御假说。所研究的三个物种对啃食的反应，要么是快速再生，要么是在剩余组织中增加多酚产量。这些模式并不遵循任何系统发育关系，而是与每个物种的适口性有微弱关联。适口性很高的落叶物种紫苑，能够快速再生，其组成型和啃食诱导型的总多酚、缩合单宁和蛋白质沉淀单宁含量均无或极低。常绿硬叶物种白翼菊的再生能力有限，多酚含量中等，而常绿肉质物种多刺露子花在研究期间几乎没有再生。多刺露子花的组成型和啃食诱导型多酚、缩合单宁和蛋白质沉淀单宁含量最高。在其中两个物种中，不止一种抗食草动物防御特征同时出现。白翼菊的叶子既含有肝毒素又有多酚，而多刺露子花既有结构防御（刺）又有化学防御。卡鲁灌木对模拟啃食的反应被解释为植物化学的被动改变，而不是对食草动物的主动防御反应。
