Newingham Beth A, Callaway Ragan M, Bassirirad Hormoz
Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA.
Oecologia. 2007 Oct;153(4):913-20. doi: 10.1007/s00442-007-0791-2. Epub 2007 Jul 7.
Centaurea maculosa, an invasive North American plant species, shows a high degree of tolerance to the root-boring biocontrol herbivore, Agapeta zoegana. For example, infested individuals of C. maculosa often exhibit more rigorous growth and reproduction compared with their non-infested counterparts. Compensatory responses to aboveground herbivores often involve increases in leaf area and/or photosynthetic capacity, but considerably less is known about root system compensatory responses to belowground herbivory. We used a (15)N labeling approach to evaluate whether compensatory adjustments in N acquisition via changes in root morphology and/or physiological uptake capacity could explain the ability of C. maculosa to tolerate root herbivory. Root herbivory reduced whole plant N uptake by more than 30% and root uptake capacity by about 50%. Despite a marked reduction in N procurement, herbivory did not affect total biomass or shoot N status. Infested plants maintained shoot N status by shifting more of the acquired N from the root to the shoot. To our knowledge, shifting N allocation away from a root herbivore has not been reported and provides a plausible mechanism for the host plant to overcome an otherwise devastating effect of a root herbivore-induced N deficit.
斑点矢车菊是一种入侵性的北美植物物种，对根部钻蛀性生物防治食草动物Agapeta zoegana具有高度耐受性。例如，受侵染的斑点矢车菊个体与未受侵染的个体相比，往往表现出更旺盛的生长和繁殖能力。对地上食草动物的补偿反应通常涉及叶面积和/或光合能力的增加，但对于根系对地下食草作用的补偿反应了解得要少得多。我们采用¹⁵N标记方法来评估通过根系形态变化和/或生理吸收能力的改变而在氮素获取方面的补偿性调整是否能够解释斑点矢车菊耐受根部食草作用的能力。根部食草作用使整株植物的氮素吸收减少了30%以上，根系吸收能力降低了约50%。尽管氮素获取显著减少，但食草作用并未影响总生物量或地上部分的氮素状况。受侵染的植株通过将更多获取的氮从根部转移到地上部分来维持地上部分的氮素状况。据我们所知，将氮分配从根部食草动物那里转移开的情况尚未见报道，这为寄主植物克服根部食草动物诱导的氮素缺乏所带来的潜在毁灭性影响提供了一种合理的机制。
