Chen Yayuan, Puentes Adriana, Björkman Christer, Brosset Agnès, Bylund Helena
Department of Ecology, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden.
Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio, Finland.
Front Plant Sci. 2021 Jul 20;12:695867. doi: 10.3389/fpls.2021.695867. eCollection 2021.
Exogenous application of the plant hormone methyl jasmonate (MeJA) can trigger induced plant defenses against herbivores, and has been shown to provide protection against insect herbivory in conifer seedlings. Other methods, such as mechanical damage to seedlings, can also induce plant defenses, yet few have been compared to MeJA and most studies lack subsequent herbivory feeding tests. We conducted two lab experiments to: (1) compare the efficacy of MeJA to mechanical damage treatments that could also induce seedling resistance, (2) examine if subsequent insect damage differs depending on the time since induction treatments occurred, and (3) assess if these induction methods affect plant growth. We compared Scots pine () seedlings sprayed with MeJA (10 or 15 mM) to seedlings subjected to four different mechanical bark damage treatments (two different bark wound sizes, needle-piercing damage, root damage) and previous pine weevil () damage as a reference treatment. The seedlings were exposed to pine weevils 12 or 32 days after treatments (early and late exposure, hereafter), and resistance was measured as the amount of damage received by plants. At early exposure, seedlings treated with needle-piercing damage received significantly more subsequent pine weevil feeding damage than those treated with MeJA. Seedlings treated with MeJA and needle-piercing damage received 84% less and 250% more pine weevil feeding, respectively, relative to control seedlings. The other treatments did not differ statistically from control or MeJA in terms of subsequent pine weevil damage. For the late exposure group, plants in all induction treatments tended to receive less pine weevil feeding (yet this was not statistically significant) compared to control seedlings. On the other hand, MeJA significantly slowed down seedling growth relative to control and all other induction treatments. Overall, the mechanical damage treatments appeared to have no or variable effects on seedling resistance. One of the treatments, needle-piercing damage, actually increased pine weevil feeding at early exposure. These results therefore suggest that mechanical damage shows little potential as a plant protection measure to reduce feeding by a bark-chewing insect.
外源施用植物激素茉莉酸甲酯（MeJA）可引发植物对食草动物的诱导防御，并且已证明其能为针叶树幼苗抵御昆虫取食提供保护。其他方法，如对幼苗进行机械损伤，也可诱导植物防御，但很少有方法与MeJA进行比较，且大多数研究缺乏后续的食草动物取食试验。我们进行了两项实验室实验，目的是：（1）比较MeJA与同样能诱导幼苗抗性的机械损伤处理的效果；（2）研究后续昆虫损伤是否因诱导处理后经过的时间不同而有所差异；（3）评估这些诱导方法是否影响植物生长。我们将喷施MeJA（10或15 mM）的苏格兰松（）幼苗与接受四种不同机械树皮损伤处理（两种不同的树皮伤口大小、针刺损伤、根部损伤）的幼苗以及先前遭受松象鼻虫（）损伤的幼苗作为对照处理进行比较。处理后12天或32天（分别为早期暴露和晚期暴露）将幼苗暴露于松象鼻虫，以植物所受损伤量来衡量抗性。在早期暴露时，经针刺损伤处理的幼苗比经MeJA处理的幼苗遭受的后续松象鼻虫取食损伤显著更多。相对于对照幼苗，经MeJA和针刺损伤处理的幼苗分别遭受的松象鼻虫取食量减少了84%和增加了250%。就后续松象鼻虫损伤而言，其他处理与对照或MeJA在统计学上无差异。对于晚期暴露组，与对照幼苗相比，所有诱导处理的植株遭受的松象鼻虫取食量往往较少（但这在统计学上不显著）。另一方面，相对于对照和所有其他诱导处理，MeJA显著减缓了幼苗生长。总体而言，机械损伤处理对幼苗抗性似乎没有影响或影响不一。其中一种处理，即针刺损伤，实际上在早期暴露时增加了松象鼻虫的取食量。因此，这些结果表明，作为一种减少树皮咀嚼昆虫取食的植物保护措施，机械损伤几乎没有潜力。
