Data from: Multiple simultaneous treatments change plant response from adaptive parental effects to within-generation plasticity, in Arabidopsis thaliana

In general, studies on plant phenotypic plasticity concentrate on plant responses to different levels of a single environmental factor. Under natural conditions, however, multiple environmental factors often vary simultaneously. I studied the consequences for lifetime fitness caused by single treatments or treatment combinations by investigating patterns of phenotypic plasticity within and between generations. The parental plants (3 genotypes of the annual plant Arabidopsis thaliana) received zero, one or two stress treatments at an early life-stage. The treatments included wounding, shading, chilling, and their pairwise combinations. In the second generation, offspring of treated plants received either the parental or no treatment. Offspring of non-treated plants were reared under all treatment conditions. Plants responded strongly to the treatments, especially through delayed reproduction, which positively affected lifetime fitness. Notably, treatment combinations triggered stronger plastic responses on average. Because the delay in reproduction was offset by a delay in senescence, the treatments resulted in a fitness gain instead of a loss. However, under adverse environmental conditions, this delay represents a potential fitness cost, especially when the time for reproduction is limited. The treatments wounding and shading triggered parental effects that increased fitness only in plants that themselves received the treatment. Untreated offspring of wounded or shaded parents performed like control plants. Also, these parental effects were not accompanied by potential fitness costs, such as delayed reproduction. Chilling triggered genotype-specific parental effects that increased or reduced fitness. Of the treatment combinations only wounding and shading resulted in genotype-specific parental effects that increased or reduced fitness independently of offspring treatment. These results suggest that the response of annual plants to treatment combinations triggers predominantly within-generation plastic responses that include potential fitness costs, which cannot be inferred from studies that manipulate environmental factors individually. Therefore, single treatment studies likely underestimate the costs of plasticity in natural environments.总体而言，现有关于植物表型可塑性（phenotypic plasticity）的研究多聚焦于植物对单一环境因子不同水平的响应。然而在自然环境中，多种环境因子往往同时发生变化。本研究通过探究代内与代间的表型可塑性模式，分析了单一胁迫处理或处理组合对植物终生适合度（lifetime fitness）的影响。本研究以一年生植物拟南芥（Arabidopsis thaliana）的3个基因型为实验材料，在其早期生长阶段施加0种、1种或2种胁迫处理，处理方式包括机械损伤、遮阴、低温胁迫及其两两组合。在第二代实验中，经处理的亲本植株的后代要么接受与亲本一致的胁迫处理，要么不施加任何处理；而未接受处理的亲本植株的后代，则在全部处理条件下进行培育。植株对胁迫处理表现出强烈响应，尤以生殖延迟最为显著，该响应对终生适合度产生了正向影响。值得注意的是，处理组合平均而言能触发更强的可塑性响应。由于生殖延迟被衰老延迟所抵消，胁迫处理最终带来了适合度增益而非损失。不过在不利环境条件下，这种延迟可能构成潜在的适合度成本，尤其是当生殖周期有限时。机械损伤与遮阴处理引发的亲本效应（parental effects）仅在自身接受该处理的植株中提升了适合度。经机械损伤或遮阴处理的亲本所产生的未处理后代，其生长表现与对照植株无异，此外，这类亲本效应未伴随潜在的适合度成本，例如生殖延迟。低温胁迫则触发了基因型特异性的亲本效应，可提升或降低植株的适合度。在所有处理组合中，仅机械损伤与遮阴的组合产生了基因型特异性的亲本效应，其对适合度的影响不受后代自身处理条件的调控。上述结果表明，一年生植物对胁迫处理组合的响应主要触发代内可塑性响应，且该响应包含潜在的适合度成本——这一点无法通过单一操纵环境因子的研究推断得出。因此，单一处理研究很可能低估了自然环境中表型可塑性的成本。