Data from: Continuous high and low temperature induced a decrease of photosynthetic activity and changes in the diurnal fluctuations of organic acids in Opuntia streptacantha

Opuntia plants grow naturally in areas where temperatures are extreme and highly variable in the day during the entire year. These plants survive through different adaptations to respond to adverse environmental conditions. Despite this capability, it is unknown how CAM photosynthetic activity and growth in Opuntia plantlets is affected by constant heat or cold. Therefore, the main objective of this research was to evaluate the short-term effect of high (40°C) and low (4°C) continuous temperatures on the photosynthetic efficiency, the organic acid content (malic acid) and the relative growth rate (RGR) in seven-month-old Opuntia streptacantha plantlets during 5, 10, and 15 days. Chlorophyll fluorescence analysis allowed us to determine that high temperatures negatively impact the photosynthetic efficiency of O. streptacantha plantlets, which exhibited the lowest values of maximum quantum efficiency of the photosystem II (Fv/Fm = 52%, Fv/F0 = 85%), operational quantum yield of PS (ΦPSII = 65%) and relative electron transport rate (rETR = 65%), as well as highest values of basal fluorescence (F0 = 226%) during 15 days of treatment. Similarly, low temperatures decreased Fv/Fm (16%), Fv/F0 (50%), ΦPSII and rETR (16%). High temperatures also decreased nocturnal acidification in approximately 34–50%, whereas low temperatures increased it by 30–36%. Additionally, both continuous temperatures affected drastically diurnal consumption of malic acid, which was related to a significant RGR inhibition, where the specific photosynthetic structure area component was the most affected. Our results allowed determining that, despite the high tolerance to extreme temperatures described for Opuntia plants, young individuals of O. streptacantha suffered photosynthetic impairment that led to the inhibition of their growth. Thus, the main findings reported in this study can help to predict the potential impact of climatic change on the establishment and survival of succulent species of arid and semiarid regions of Mexico.

仙人掌属（Opuntia）植物自然分布于全年昼夜温度极端且波动剧烈的生境中，可通过多种适应性策略抵御逆境环境胁迫。尽管具备此种耐受能力，但目前学界尚未明确恒定高温或低温会如何影响仙人掌属幼苗的景天酸代谢（CAM）光合活性与生长状态。为此，本研究的核心目标为：评估持续高温（40℃）与低温（4℃）分别处理5、10、15天后，对7月龄胭脂仙人掌（Opuntia streptacantha）幼苗的光合效率、有机酸（苹果酸，malic acid）含量及相对生长速率（RGR）的短期影响。通过叶绿素荧光分析（Chlorophyll fluorescence analysis）可知，持续高温会对胭脂仙人掌幼苗的光合效率产生负面影响：在处理15天时，其光系统II（photosystem II, PSII）的最大量子效率（Fv/Fm = 52%、Fv/F0 = 85%）、PSII有效量子产额（ΦPSII = 65%）及相对电子传递速率（rETR = 65%）均降至最低水平，而基础荧光值（F0 = 226%）则达到峰值。与之类似，低温处理会使Fv/Fm下降16%、Fv/F0下降50%，ΦPSII与rETR下降16%。高温还会使夜间酸化程度降低约34%~50%，而低温则使其提升30%~36%。此外，两种恒定温度均会显著干扰苹果酸的日间消耗过程，这与相对生长速率受到显著抑制密切相关，其中特定光合结构的面积组分受影响最为显著。本研究结果证实：尽管此前研究已证实仙人掌属植物对极端温度具备较高耐受性，但胭脂仙人掌幼株仍会出现光合损伤，进而导致生长受抑。综上，本研究的核心发现可用于预测气候变化对墨西哥干旱与半干旱地区肉质植物种群建立与存活的潜在影响。