Institute of Rice Industry Technology Research, Key Laboratory of Functional Agriculture of Guizhou Provincial Department of Education, Key Laboratory of Molecular Breeding for Grain and Oil Crops in Guizhou Province, College of Agricultural Sciences, Guizhou University, Guiyang, Guizhou, 550025, China.
Key Laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), Guizhou University, Guiyang, Guizhou, 550025, China.
BMC Plant Biol. 2024 Sep 30;24(1):903. doi: 10.1186/s12870-024-05615-2.
During the cold season, low temperature (LT) and high relative humidity (HRH) are significant environmental factors in greenhouses and plastic tunnels, often hindering plant growth and development. The chlorophyll (Chl) biosynthesis inhibitory mechanisms under LT and HRH stress are still widely unclear. To understand how cucumbers seedlings respond to LT and HRH stress, we investigated the impact of these stressors on Chl biosynthesis.
Our results revealed that individual LT, HRH and combined LT + HRH stress conditions affected chlorophyll a, b, total chlorophyll and carotenoid content, reducing the levels of these pigments. The levels of Chlorophyll precursors were also markedly reduced under LT and HRH stresses, with the greatest reduction observed in cucumber seedlings exposed to LT + HRH conditions (9/5℃, 95%HRH). The activities of glutamate-1-semialdehyde transaminase (GSA-AT), ALA dehydratase (ALAD), Mg-chelatase, and protochlorophyllide oxidoreductase (POR) were increased under individual LT, HRH, conditions but decreased by combination of LT + HRH stress condition. In addition, Chl biosynthesis related genes (except PBG) were upregulated by the HRH stress but were significantly downregulated under the LT + HRH stress condition in cucumber seedlings. Furthermore, the content of phenols, flavonoids and phenolic acids (cinnamic acid and caffeic acid) were significantly surged under LT + HRH treatment over the control. Histochemical observation showed higher O and HO content in cucumber leaves during the LT and HRH stress.
The results indicate that LT + HRH stress significantly impairs chlorophyll biosynthesis in cucumber seedlings by drastically reducing pigment accumulation, altering enzyme activity and gene expression. Additionally, LT + HRH stress induces oxidative damage, which further exacerbates the decline in chlorophyll content and affects overall cucumber metabolism.
在寒冷季节，低温（LT）和高相对湿度（HRH）是温室和塑料大棚中的重要环境因素，常阻碍植物的生长和发育。低温和高湿胁迫下叶绿素（Chl）生物合成抑制的机制仍不清楚。为了了解黄瓜幼苗对低温和高湿胁迫的响应，我们研究了这些胁迫因素对 Chl 生物合成的影响。
我们的结果表明，单独的 LT、HRH 和组合的 LT+HRH 胁迫条件影响叶绿素 a、b、总叶绿素和类胡萝卜素的含量，降低这些色素的水平。低温和高湿胁迫下叶绿素前体的水平也明显降低，在 LT+HRH 条件下（9/5℃，95%HRH）黄瓜幼苗的降幅最大。谷氨酸-1-半醛转氨酶（GSA-AT）、ALA 脱水酶（ALAD）、Mg-螯合酶和原叶绿素氧化还原酶（POR）的活性在单独的 LT、HRH 条件下增加，但在 LT+HRH 胁迫条件下降低。此外，Chl 生物合成相关基因（除 PBG 外）受 HRH 胁迫上调，但在 LT+HRH 胁迫条件下，黄瓜幼苗中显著下调。此外，LT+HRH 处理下的酚类、类黄酮和酚酸（肉桂酸和咖啡酸）的含量明显高于对照。组织化学观察表明，在 LT 和 HRH 胁迫下，黄瓜叶片中的 O 和 HO 含量较高。
结果表明，LT+HRH 胁迫通过显著降低色素积累、改变酶活性和基因表达，严重损害黄瓜幼苗的叶绿素生物合成。此外，LT+HRH 胁迫诱导氧化损伤，进一步加剧叶绿素含量下降，影响黄瓜整体代谢。
