Hunter Mark D, Schultz Jack C
Department of Entomology, Pennsylvania State University, 16802, University Park, PA, USA.
Oecologia. 1993 May;94(2):195-203. doi: 10.1007/BF00341317.
Although wound-induced responses in plants are widespread, neither the ecological nor the evolutionary significance of phytochemical induction is clear. Several studies have shown, for example, that induced responses can act against both plant pathogens and herbivores simultaneously. We present the first evidence that phytochemical induction can inhibit a pathogen of the herbivore responsible for the defoliation. In 1990, we generated leaf damage by enclosing gypsy moth larvae on branches of red oak trees. We then inoculated a second cohort of larvae with a nuclear polyhedrosis virus (LdNPV) on foliage from the damaged branches. Larvae were less susceptible to virus consumed on foliage from branches with increasing levels of defoliation, and with higher concentrations of gallotannin. Defoliation itself was not related to any of our chemistry measures. Field sampling supported the results of our experiments: death from virus among feral larvae collected from unmanipulated trees was also negatively correlated with defoliation. In 1991, defoliation and gallotannin were again found to inhibit the virus. In addition, gallotannin concentrations were found to be positively correlated with defoliation the previous year. Compared with previous results that demonstrated a delecterious effect of induction on gypsy moth pupal weight and fecundity, the inhibition of the virus should confer an advantage to the gypsy moth. Since leaf damage levels increase as gypsy moth density increases, and since leaf damage inhibits the gypsy moth virus, there is the potential for positive feedback in the system. If phytochemical induction in red oak can inhibit an animal pathogen such as LdNPV, it suggests to us that induction in red oak is a generalized response to tissue damage rather than an adaptive defense against herbivores.
虽然植物中伤口诱导的反应很普遍，但植物化学诱导的生态意义和进化意义都不清楚。例如，几项研究表明，诱导反应可以同时对抗植物病原体和食草动物。我们提供了首个证据，证明植物化学诱导可以抑制造成落叶的食草动物的一种病原体。1990年，我们通过将舞毒蛾幼虫封闭在红橡树的树枝上来造成叶片损伤。然后，我们在来自受损树枝的叶子上用核型多角体病毒（LdNPV）接种了第二批幼虫。随着落叶程度的增加以及没食子单宁浓度的升高，幼虫对取自树枝上叶子的病毒的易感性降低。落叶本身与我们的任何化学测量指标均无关联。野外采样支持了我们的实验结果：从未经处理的树上采集的野生幼虫中，因病毒导致的死亡也与落叶呈负相关。1991年，再次发现落叶和没食子单宁可抑制该病毒。此外，还发现没食子单宁浓度与前一年的落叶呈正相关。与之前证明诱导对舞毒蛾蛹重和繁殖力有有害影响的结果相比，病毒受到抑制应该会给舞毒蛾带来优势。由于随着舞毒蛾密度的增加叶片损伤水平会升高，并且由于叶片损伤会抑制舞毒蛾病毒，因此该系统中存在正反馈的可能性。如果红橡树中的植物化学诱导能够抑制诸如LdNPV这样的动物病原体，那么这向我们表明，红橡树中的诱导是对组织损伤的一种普遍反应，而不是针对食草动物的适应性防御。
