盐胁迫下荒漠共生植物红砂与珍珠的根茎叶中离子吸收与分配特征

西北荒漠地区C3小灌木红砂(Reaumuria soongorica)和C4半灌木珍珠猪毛菜(Salsola passerina)在特定环境下混生在一起,分布面积广阔。以采自腾格里沙漠边缘荒漠地带的天然野生珍珠猪毛菜和红砂群落的幼苗为材料,经0、100、200、300、400mmol/L NaCl盐溶液共同胁迫10 d,检测它们的含水量、主要矿质离子在根茎叶的含量与分布,揭示二者耐盐的共生协同的离子平衡适应机制。试验结果发现,珍珠猪毛菜叶片具有"吸钾排钠的"的耐盐特征,红砂叶片具备"吸钠排钾"的特征,吸收利用无机矿质离子具备互补效应。二者耐盐Cl、Ca和Si离子吸收与累积能力存在很大差异:随着盐胁迫程度加剧,红砂的根茎叶中Cl离子含量持续增加,并且为珍珠猪毛菜的2—5倍;珍珠猪毛菜根中Ca离子含量为红砂的2—3倍,但含量变化不显著;红砂根中Si离子含量迅速降低后稳定,并且是珍珠猪毛菜根的3—5倍,其他器官变化差异较小。因此,红砂与珍珠猪毛菜的共培养盐胁迫下根中吸收的离子侧重不同,红砂以Na、Cl、Si为主,珍珠猪毛菜以K、Ca为主。随着盐胁迫的程度加强,离子选择吸收系数S k,Na的变化趋势降低,表明二者叶部对Na的选择性减小,K的选择性吸收积累增大,增强了它们的抗盐性,最终使叶片所受盐害减小。总之红砂与珍珠猪毛菜共生的耐盐离子稳态机制显著不同,离子吸收与分布具有互补互利的效应。

Ion absorption and distribution of symbiotic Reaumuria soongorica and Salsola passerina seedlings under NaCl stress

Wild C₃ plant Reaumuria soongorica and C₄ plant Salsola passerina coexist mutually in some desert habitats and form large-scale communities distributed in northwestern China. In this study we collected their seedlings from the edge of the Tengger desert. Their seedlings were subjected to salt stress together by soaked in 0, 100, 200, 300 to 400 mmol/L NaCl solutions for 10 d. We examined their water contents and main mineral ion contents changes in their roots, stems, and leaves during salt stress. The experiment results indicated that S. passerina absorbed K and inhibited Na in leaves to adapt to high salt stress as NaCl concentration increased. By on the contrary, R. soongorica absorbed Na and inhibited K. Cl in its roots continuously increased two to five times higher than that in S. passerina's roots. Ca content in S. passerina roots was two to three times higher than that in R. soongorica roots. Si content in R. soongorica roots was three to five times higher than that in S. passerina. Therefore, salt stress resistance in R. soongorica and S. passerina communities occurred via root absorption of different ions, and these ions were subsequently distributed to various organs. Based on salt ion selective absorption coefficient S_{Na(leaf/root)/K(leaf/root)} ratio value, the two plants foliar selectivity increased K absorption and decreased Na absorption, thereby reducing salt damage on the leaves. Thus, these plants mutually benefit from each other and cooperate to promote their resistance to salt stress.