Plants defend themselves against herbivore attack by constitutively producing toxic secondary metabolites, as well as by inducing them in response to herbivore feeding. Induction of secondary metabolites can cross plant tissue boundaries, such as from root to shoot. However, whether the potential for plants to systemically induce secondary metabolites from roots to shoots shows genetic variability, and thus, potentially, is under selection conferring fitness benefits to the plants is an open question. To address this question, we induced 26 maternal plant families of the wild species Cardamine hirsuta belowground (BG) using the wound-mimicking phytohormone jasmonic acid (JA). We measured resistance against a generalist (Spodoptera littoralis) and a specialist (Pieris brassicae) herbivore species, as well as the production of glucosinolates (GSLs) in plants. We showed that BG induction increased AG resistance against the generalist but not against the specialist, and found substantial plant family-level variation for resistance and GSL induction. We further found that the systemic induction of several GSLs tempered the negative effects of herbivory on total seed set production. Using a widespread natural system, we thus confirm that BG to AG induction has a strong genetic component, and can be under positive selection by increasing plant fitness. We suggest that natural variation in systemic induction is in part dictated by allocation trade-offs between constitutive and inducible GSL production, as well as natural variation in AG and BG herbivore attack in nature.

中文翻译：

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草甘膦从地下到地面的全身诱导变化在草食动物攻击下介导植物适应性后果。

植物通过组成性地产生有毒的次生代谢产物以及通过响应草食动物的摄食诱导它们来防御草食动物的攻击。次级代谢产物的诱导可以跨越植物组织的边界，例如从根到芽。然而，植物从根到芽系统性地诱导次生代谢产物的潜力是否显示出遗传变异性，因此是否有可能在选择中赋予植物适宜性的益处是一个悬而未决的问题。为了解决这个问题，我们使用模仿伤口的植物激素茉莉酸（JA）诱导了26种野生物种Cardamine hirsuta地下（BG）的母本植物。我们测量了对通才（Spodoptera littoralis）和专科医生（菜青虫（Pieris brasicae）草食动物种类，以及植物中芥子油苷（GSLs）的产生。我们发现BG诱导增加了AG对通用植物的抗性，但对专家没有抵抗力，并且发现了植物家族水平的抗性和GSL诱导变异。我们进一步发现，几种GSL的系统诱导减轻了草食对种子总产量的负面影响。因此，使用广泛的自然系统，我们确认BG到AG的诱导具有很强的遗传成分，可以通过增加植物适应性来进行正选择。我们认为，系统诱导的自然变异部分取决于组成型和诱导型GSL产生之间的分配权衡，以及AG和BG草食动物攻击的自然变异。