Table_1_Selenium enhances chilling stress tolerance in coffee species by modulating nutrient, carbohydrates, and amino acids content.xlsx

The effects of selenium (Se) on plant metabolism have been reported in several studies triggering plant tolerance to abiotic stresses, yet, the effects of Se on coffee plants under chilling stress are unclear. This study aimed to evaluate the effects of foliar Se application on coffee seedlings submitted to chilling stress and subsequent plant recovery. Two Coffea species, Coffea arabica cv. Arara, and Coffea canephora clone 31, were submitted to foliar application of sodium selenate solution (0.4 mg plant–1) or a control foliar solution, then on day 2 plants were submitted to low temperature (10°C day/4°C night) for 2 days. After that, the temperature was restored to optimal (25°C day/20°C night) for 2 days. Leaf samples were collected three times (before, during, and after the chilling stress) to perform analyses. After the chilling stress, visual leaf injury was observed in both species; however, the damage was twofold higher in C. canephora. The lower effect of cold on C. arabica was correlated to the increase in ascorbate peroxidase and higher content of starch, sucrose, and total soluble sugars compared with C. canephora, as well as a reduction in reducing sugars and proline content during the stress and rewarming. Se increased the nitrogen and sulfur content before stress but reduced their content during low temperature. The reduced content of nitrogen and sulfur during stress indicates that they were remobilized to stem and roots. Se supply reduced the damage in C. canephora leaves by 24% compared with the control. However, there was no evidence of the Se effects on antioxidant enzymatic pathways or ROS activity during stress as previously reported in the literature. Se increased the content of catalase during the rewarming. Se foliar supply also increased starch, amino acids, and proline, which may have reduced symptom expression in C. canephora in response to low temperature. In conclusion, Se foliar application can be used as a strategy to improve coffee tolerance under low-temperature changing nutrient remobilization, carbohydrate metabolism, and catalase activity in response to rewarming stress, but C. arabica and C. canephora respond differently to chilling stress and Se supply.

已有多项研究报道了硒（Selenium, Se）对植物代谢的影响，其可增强植物对非生物胁迫（abiotic stresses）的耐受性，但目前关于硒对低温胁迫（chilling stress）下咖啡植株的作用尚不明确。本研究旨在评估叶面施硒（foliar Se application）对遭受低温胁迫及后续恢复过程的咖啡幼苗的影响。本研究选取两个咖啡品种，即阿拉比卡咖啡（Coffea arabica）品种‘阿拉拉（Arara）’以及罗布斯塔咖啡（Coffea canephora）无性系31，分别叶面喷施硒酸钠溶液（sodium selenate solution，0.4 mg·plant⁻¹）或对照叶面溶液（control foliar solution）。试验第2天时，将植株置于低温环境（昼温10℃/夜温4℃）下处理2天，随后恢复至适宜温度（昼温25℃/夜温20℃）继续培养2天。分别在低温胁迫前、胁迫中及胁迫后三个时间点采集叶片样本以开展相关分析。低温胁迫结束后，两个咖啡品种均出现可见的叶片损伤，但罗布斯塔咖啡的损伤程度是阿拉比卡咖啡的两倍。阿拉比卡咖啡受低温影响较轻，这与其抗坏血酸过氧化物酶（ascorbate peroxidase）活性升高、淀粉、蔗糖及总可溶性糖含量高于罗布斯塔咖啡相关；同时在胁迫及复温阶段，其还原糖与脯氨酸含量均有所降低。叶面施硒可在胁迫前提升植株氮、硫含量，但在低温胁迫期间降低二者含量。胁迫期氮、硫含量下降表明其被重新转运至茎秆与根系。与对照组相比，施硒可使罗布斯塔咖啡的叶片损伤程度降低24%。但与此前文献报道不同，本研究未发现硒对胁迫期间的抗氧化酶通路或活性氧（Reactive Oxygen Species, ROS）活性产生影响。不过在复温阶段，施硒可提升过氧化氢酶（catalase）活性。此外，叶面施硒还可提升淀粉、氨基酸及脯氨酸含量，这可能降低了罗布斯塔咖啡在低温胁迫下的症状表现。综上，叶面施硒可通过调控养分转运、碳水化合物代谢及复温胁迫（rewarming stress）阶段的过氧化氢酶活性，作为提升咖啡低温耐受性的可行策略，但阿拉比卡咖啡与罗布斯塔咖啡对低温胁迫及施硒的响应存在显著差异。