Data from: Experimental evaluation of the robustness of the growth-stress tolerance trade-off within the perennial grass Dactylis glomerata

1. A core tenet of functional ecology is that the vast phenotypic diversity observed in the plant kingdom could be partly generated by a trade- off between the ability of plants to grow quickly and acquire resources in rich environments vs. the ability to conserve resources and avoid mortality under stress. However, experimental demonstrations remain scarce and potentially blurred by phylogenetic constraints in cross-species analyses. Here we experimentally decoupled growth potential and stress survival by applying an off-season stress on contrasting populations of the perennial grass Dactylis glomerata exhibiting a range of seasonal dormancy. 2. Seventeen populations of D. glomerata, originating from a latitudinal gradient from Norway to Morocco, were subjected to three types of dehydration stress: winter frost in Norway, summer drought, and early spring (off-season) drought stress in the south of France. Growth rate, and two leaf traits (leaf width and leaf dry matter content) suspected to be involved in the adaptation to dehydration stress, were monitored under optimal conditions. We quantified plant dehydration survival as the amount of plant recovery after a severe stress. 3. Nordic populations were found to be winter dormant. Winter and summer dormant populations better survived frost and summer drought, respectively. However, no trade-off between growth potential and dehydration survival was detected in non-dormant plants in early spring when dehydration occurred unseasonably for all populations. Furthermore, Mediterranean populations better survived an early spring drought. 4. Our results highlight the importance of assessing plant growth potential as a response to seasonal environmental cues. They suggest that growth potential and stress survival trade-off when plants exhibit seasonal dormancy but can be functionally independent at other seasons. Consequently, the growth-stress survival relationship could be better described as a dynamic linkage rather than a constant and general trade-off. Moreover, leaf trait values, such as thinner and more lignified leaves reflecting drought adaptation, may have contributed to the improved drought-stress survival without resulting in a cost to growth. 5. Further exploration of the growth-stress survival relationship should permit deciphering the suite of plant traits and trait covariations involved in plants’ responses to increasing stress.1. 功能生态学（functional ecology）的核心原则之一认为，植物界中广泛观测到的表型多样性（phenotypic diversity），部分可由两类能力间的权衡（trade-off）所产生：一类是植物在资源丰富的环境中快速生长并获取资源的能力，另一类是在胁迫环境下保存资源、规避死亡的能力。然而，跨物种分析中的系统发育约束（phylogenetic constraints）往往会模糊相关实验证据，且此类实验论证迄今仍较为匮乏。本研究通过对表现出不同季节休眠特性的多年生草本植物鸡脚草（Dactylis glomerata）的不同种群施加非季节胁迫，在实验层面实现了生长潜力与胁迫存活能力的解耦。 2. 本研究选取了17个鸡脚草种群，其采样点沿挪威至摩洛哥的纬度梯度分布，分别接受三种脱水胁迫处理：挪威冬季霜冻、夏季干旱，以及法国南部的早春（非季节）干旱胁迫。在最优生长条件下，研究人员监测了植株的生长速率，以及两项疑似参与脱水胁迫适应的叶片性状：叶宽与叶片干物质含量（leaf dry matter content）。本研究以重度胁迫后植株的恢复程度，作为植株脱水胁迫存活能力的量化指标。 3. 研究发现，北欧种群具有冬季休眠特性；冬季休眠与夏季休眠种群分别更耐受霜冻与夏季干旱。然而，在早春这一所有种群均不处于休眠期的非季节脱水胁迫处理中，未检测到生长潜力与脱水存活能力间存在权衡关系。此外，地中海地区的种群对早春干旱的耐受能力更强。 4. 本研究结果凸显了将植物生长潜力作为季节性环境响应指标进行评估的重要性。结果表明，当植物表现出季节休眠时，生长潜力与胁迫存活能力间存在权衡，但在其他季节二者则可能在功能上相互独立。因此，生长-胁迫存活的关系更适合被描述为一种动态关联，而非普适性的恒定权衡。此外，反映干旱适应特性的叶片性状（如更薄且木质化程度更高的叶片），或许有助于提升植株的干旱胁迫耐受能力，且不会对植株生长造成代价。 5. 未来对生长-胁迫存活关系的进一步探索，将有助于解析植物应对不断增强的胁迫时所涉及的一系列性状及其性状协同变异机制。