Arabinogalactan protein content in both root extracellular trap and root exudates varies in three Sahelian woody plant species that are differentially tolerant to drought. At the root tip, mature root cap cells, mainly border cells (BCs)/border-like cells (BLCs) and their associated mucilage, form a web-like structure known as the “Root Extracellular Trap” (RET). Although the RET along with the entire suite of root exudates are known to influence rhizosphere function, their features in woody species is poorly documented. Here, RET and root exudates were analyzed from three Sahelian woody species with contrasted sensitivity to drought stress (Balanites aegyptiaca, Acacia raddiana and Tamarindus indica) and that have been selected for reforestation along the African Great Green Wall in northern Senegal. Optical and transmission electron microscopy show that Balanites aegyptiaca, the most drought-tolerant species, produces only BC, whereas Acacia raddiana and Tamarindus indica release both BCs and BLCs. Biochemical analyses reveal that RET and root exudates of Balanites aegyptiaca and Acacia raddiana contain significantly more abundant arabinogalactan proteins (AGPs) compared to Tamarindus indica, the most drought-sensitive species. Root exudates of the three woody species also differentially impact the plant soil beneficial bacteria Azospirillum brasilense growth. These results highlight the importance of root secretions for woody species survival under dry conditions.

中文翻译：

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三种萨赫勒木本植物根系细胞外诱捕器和分泌物的体外表征

根细胞外陷阱和根分泌物中的阿拉伯半乳聚糖蛋白含量在三种对干旱有不同耐受性的萨赫勒木本植物中有所不同。在根尖，成熟的根帽细胞，主要是边缘细胞（BCs）/边缘样细胞（BLCs）及其相关的粘液，形成称为“根细胞外陷阱”（RET）的网状结构。尽管已知 RET 以及整套根系分泌物会影响根际功能，但它们在木本物种中的特征却鲜有记载。在这里，对三种对干旱胁迫具有不同敏感性的萨赫勒木本植物（Balanites aegyptiaca、Acacia raddiana 和 Tamarindus indica）进行了 RET 和根系分泌物分析，这些植物已被选为塞内加尔北部非洲绿色长城沿线的重新造林。光学和透射电子显微镜显示，最耐旱的埃及龟头龟仅产生 BC，而 Acacia raddiana 和罗望子则释放 BC 和 BLC。生化分析表明，与对干旱最敏感的物种罗望子相比，埃及龟头龟和金合欢的 RET 和根分泌物含有显着更多的阿拉伯半乳聚糖蛋白 (AGP)。三种木本植物的根系分泌物也对植物土壤有益细菌 Azospirillum brasilense 的生长产生不同的影响。这些结果突出了根分泌物对干燥条件下木本物种生存的重要性。生化分析表明，与对干旱最敏感的物种罗望子相比，埃及龟头龟和金合欢的 RET 和根分泌物含有显着更多的阿拉伯半乳聚糖蛋白 (AGP)。三种木本植物的根系分泌物也对植物土壤有益细菌 Azospirillum brasilense 的生长产生不同的影响。这些结果突出了根分泌物对干燥条件下木本物种生存的重要性。生化分析表明，与对干旱最敏感的物种罗望子相比，埃及龟头龟和金合欢的 RET 和根分泌物含有显着更多的阿拉伯半乳聚糖蛋白 (AGP)。三种木本植物的根系分泌物也对植物土壤有益细菌 Azospirillum brasilense 的生长产生不同的影响。这些结果突出了根分泌物对干燥条件下木本物种生存的重要性。