Barton Kasey E
Department of Botany, University of Hawai'i at Mānoa, Honolulu, HI 96822, USA
Ann Bot. 2016 May;117(6):1053-62. doi: 10.1093/aob/mcw021. Epub 2016 Apr 6.
Seedling herbivory is an important factor underlying plant community diversity and structure. While considerable research has characterized seedling defence in terms of resistance, very little is known about seedling tolerance of herbivory. Moreover, few studies have attempted to identify mechanisms of tolerance across a range of plant species.
Seedling tolerance of simulated herbivory was tested in a diverse pool of ten Hawaiian plant species, including several lobeliad species (family Campanulaceae), a grass, a herb and common woody trees and shrubs. Tolerance was measured as the relative survival and growth of damaged plants receiving 50 % defoliation with simultaneous jasmonic acid application compared with undamaged control plants, assessed 1·5 and 5 weeks after damage. Putative mechanisms of tolerance were measured, including photosynthetic parameters, light use efficiency, and biomass allocation reflecting growth priorities, and analysed using species-level regression analyses on tolerance indices.
No species fully tolerated 50 % defoliation at either harvest date, and simulated herbivory significantly reduced shoot as well as root biomass. Lobeliad species had particularly low tolerance. Species varied considerably in size, biomass allocation parameters and their constitutive (pre-damage) and induced (post-damage) photosynthetic parameters. However, only constitutive levels of non-photochemical quenching were significantly related to tolerance, indicating that species with more efficient light use (and less heat dissipation) are better at tolerating damage than species with high levels of heat dissipation.
Native Hawaiian plants expressed low tolerance to a conservative level of simulated herbivory. Root growth decreased in response to damage, but this was not associated with greater tolerance, suggesting this response may be due to allocation constraints following defoliation and not due to adaptive plasticity. Conservation of native island plants threatened by invasive herbivores should prioritize protection for seedlings for improved regeneration and the persistence of native plants in disturbed habitats.
幼苗食草作用是影响植物群落多样性和结构的重要因素。尽管已有大量研究从抗性角度描述了幼苗防御机制，但对于幼苗对食草作用的耐受性却知之甚少。此外，很少有研究尝试确定一系列植物物种的耐受机制。
在10种夏威夷植物的不同样本中测试了模拟食草作用下的幼苗耐受性，其中包括几种半边莲属植物（桔梗科）、一种草、一种草本植物以及常见的木本乔木和灌木。耐受性通过受损植株与未受损对照植株相比的相对存活率和生长情况来衡量，受损植株进行50%去叶处理并同时施加茉莉酸，在损伤后1.5周和5周进行评估。测定了可能的耐受机制，包括光合参数、光利用效率以及反映生长优先级的生物量分配，并使用物种水平的耐受性指数回归分析进行分析。
在两个收获日期，没有物种能完全耐受50%的去叶处理，模拟食草作用显著降低了地上部和根部生物量。半边莲属植物的耐受性尤其低。不同物种在大小、生物量分配参数以及它们的组成性（损伤前）和诱导性（损伤后）光合参数方面差异很大。然而，只有组成性的非光化学猝灭水平与耐受性显著相关，这表明光利用效率更高（且热耗散更少）的物种比热耗散水平高的物种更能耐受损伤。
夏威夷本土植物对保守水平的模拟食草作用表现出较低的耐受性。根系生长因损伤而下降，但这与更高的耐受性无关，这表明这种反应可能是由于去叶后的分配限制，而不是由于适应性可塑性。对于受到入侵食草动物威胁的本土岛屿植物的保护，应优先保护幼苗，以促进其更好地再生以及在受干扰栖息地中本土植物的存续。
