Olson D M, Davis R F, Wäckers F L, Rains G C, Potter T
Crop Protection and Management Research Unit, USDA-ARS, Tifton, GA 31793, USA.
J Chem Ecol. 2008 Oct;34(10):1341-8. doi: 10.1007/s10886-008-9532-1. Epub 2008 Aug 16.
Most studies on plant-herbivore interactions focus on either root or shoot herbivory in isolation, but above- and belowground herbivores may interact on a shared host plant. Cotton (Gossypium spp.) produces gossypol and a variety of other gossypol-like terpenoids that exhibit toxicity to a wide range of herbivores and pathogens. Cotton plants also can emit herbivore-induced volatile compounds at the site of damage and systemically on all tissues above the site of damage. As these volatile compounds attract natural enemy species of the herbivore, they are thought to represent an indirect plant defense. Our study quantified gossypol and gossypol-like compounds in cotton plants with foliage feeding (Heliocoverpa zea), root feeding (Meloidogyne incognita), or their combination. Cotton plants with these treatments were studied also with respect to induced local and systemic volatile production and the attraction of the parasitic wasp Microplitis croceipes to those plants. We also evaluated whether foliage or root feeding affected foliar nitrogen levels in cotton. After 48 hr of leaf feeding and 5 wk of root feeding, local and systemic induction of volatiles (known to attract parasitoids such as M. croceipes) occurred with herbivore damage to leaves, and it increased in levels when root herbivory was added. Nevertheless, M. croceipes were equally attracted to plants with both leaf and root damage and leaf damage only. In contrast to previous studies in cotton, production of gossypol and gossypol-like compounds was not induced in leaf and root tissue following foliage or root herbivory, or their combination. We conclude that root feeding by M. incognita has little influence on direct and indirect defenses of Gossypium hirsutum against insect herbivory.
大多数关于植物与食草动物相互作用的研究要么单独关注根部食草作用，要么单独关注地上部食草作用，但地上部和地下部的食草动物可能会在同一寄主植物上相互作用。棉花（棉属物种）会产生棉酚和多种其他类似棉酚的萜类化合物，这些化合物对多种食草动物和病原体具有毒性。棉花植株在受损部位以及受损部位上方的所有组织中都会系统性地释放由食草动物诱导产生的挥发性化合物。由于这些挥发性化合物会吸引食草动物的天敌物种，因此它们被认为是一种间接的植物防御机制。我们的研究对遭受叶片取食（棉铃虫）、根部取食（南方根结线虫）或二者组合处理的棉花植株中的棉酚和类似棉酚的化合物进行了定量分析。还研究了经过这些处理的棉花植株在诱导产生局部和系统性挥发性物质方面的情况，以及寄生蜂微红绒茧蜂对这些植株的吸引力。我们还评估了叶片或根部取食是否会影响棉花叶片中的氮含量。在叶片取食48小时和根部取食5周后，食草动物对叶片造成损害会诱导产生局部和系统性的挥发性物质（已知这些挥发性物质会吸引诸如微红绒茧蜂之类的寄生蜂），并且当添加根部食草作用时，其水平会升高。然而，微红绒茧蜂对同时遭受叶片和根部损害的植株以及仅遭受叶片损害的植株的吸引力是相同的。与之前对棉花的研究不同，在叶片或根部遭受食草作用或二者组合处理后，叶片和根部组织中并未诱导产生棉酚和类似棉酚的化合物。我们得出结论，南方根结线虫的根部取食对陆地棉针对昆虫食草作用的直接和间接防御影响很小。
