The responses of plants to recurrent stress may differ from their responses to a single stress event. In this study, we investigated whether clonal plants can remember past environments. Parental ramets of Glechoma longituba (Nakai) Kuprian were exposed to UV-B stress treatments either once or repeatedly (20 and 40 repetitions). Differences in DNA methylation levels and growth parameters among parents, offspring ramets and genets were analysed. Our results showed that UV-B stress reduced the DNA methylation level of parental ramets, and the reduction was enhanced by increasing the number of UV-B treatments. The epigenetic variation exhibited by recurrently stressed parents was maintained for a long time, but that of singly stressed parents was only short-term. Moreover, clonal plants responded to different UV-B stress treatments with different growth strategies. The one-time stress was a eustress that increased genet biomass by increasing offspring leaf allocation and defensive allocation in comparison to the older offspring. In contrast, recurring stress was a distress that reduced genet biomass, increased the biomass of storage stolons, and allocated more defensive substances to the younger ramets. This study demonstrated that the growth of offspring and genets was clearly affected by parental experience, and parental epigenetic memory and the transgenerational effect may play important roles in this effect.

植物对反复胁迫的响应可能不同于它们对单个胁迫事件的响应。在这项研究中，我们调查了克隆植物是否可以记住过去的环境。长寿树的父母分株（Nakai）Kuprian一次或多次（重复20和40次）接受UV-B压力治疗。分析了父母，后代分株和种系之间DNA甲基化水平和生长参数的差异。我们的结果表明，UV-B胁迫降低了亲本分株的DNA甲基化水平，并且通过增加UV-B的处理数量而增加了这种降低。反复承受压力的父母表现出的表观遗传变异可以维持很长时间，而单一承受压力的父母只是短期的。此外，克隆植物对不同的UV-B胁迫处理具有不同的生长策略。一次性压力是一种eustress，与较年长的后代相比，通过增加后代叶片分配和防御性分配来增加种质生物量。相比之下，反复出现的压力是一种麻烦，它减少了种系生物量，增加了贮藏茎的生物量，并为年轻的分株分配了更多的防御性物质。这项研究表明，后代和种系的生长明显受父母的经验影响，父母的表观遗传记忆和转基因效应可能在该效应中起重要作用。