Gas exchange is related to the hormone balance in mycorrhizal or nitrogen-fixing alfalfa subjected to drought
Gas exchange is related to the hormone balance in mycorrhizal or nitrogen-fixing alfalfa subjected to drought
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DOI：
10.1111/j.1399-3054.1997.tb00027.x
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发表时间：
1997-08-01
影响因子：
6.4
通讯作者：
SanchezDiaz, M
中科院分区：
文献类型：
--
作者：
Goicoechea, N;Antolin, MC;SanchezDiaz, M
菌核化对干旱条件下寄主植物光合作用气体交换的有利影响可能与磷营养和水分吸收的变化以外的因素有关。本研究旨在研究干旱对紫花苜蓿植物激素和气体交换参数的影响。与丛枝菌根(AM)真菌和/或固氮菌有关或不与之相关的细菌。试验分四个处理：(1)接种红豆杉(Taxter Sensu Gerd.)(2)只接种根瘤菌(R)的植株；(3)只接种菌根(M)的植株；(4)未接种的植株(N)。当内生菌完全形成时，处理在营养液中接受不同水平的磷和氮，以获得大小相似的植株。种植60天后，植株经历了干旱和恢复两个周期。第二次干旱后，测定了叶片水势(Psi)、CO2交换速率(CER)、叶片电导(g(W))和蒸腾作用(T)，以及叶片和根脱落酸(ABA)和细胞分裂素浓度。通过红外气体分析确定了气体交换参数。用ELISA法和HPLC法分别检测组织中细胞分裂素和脱落酸的含量。在水分充足的条件下，节根R和MR植株的ABA含量最低。水分胁迫增加了N、R和MR植株叶片中的ABA含量，而M植株的ABA含量没有变化。水分亏缺条件下ABA产量最高的是非菌根植物的根部。干旱胁迫下，非菌根植物叶片和根中ABA/细胞分裂素浓度的比值显著增加。相比之下，M植株的根中这一比例降低，而MR植株的叶和根在胁迫时保持不变。在水分充足的条件下，叶片电导率和蒸腾通量最高的是固氮R和MR植株，但这些结果并没有随着CO2交换速率的增加而受到影响。胁迫时，所有处理的光合作用、叶片电导率和蒸腾速率均下降，其中非菌根植物的下降幅度最大。这些气体交换参数与胁迫下紫花苜蓿组织中激素浓度之间的关系表明，微生物通过根中激素的产生和叶中ABA/细胞分裂素的平衡，在控制寄主植物的气体交换中起着重要作用。在干旱条件下，菌根真菌的相关性最强。
The beneficial effect of mycorrhization on photosynthetic gas exchange of host plants under drought conditions could be related to factors other than changes in phosphorus nutrition and water uptake. Our objective was to study the influence of drought on phytohormones and gas exchange parameters in Medicago saliva L. cv. Aragon associated with or in the absence of arbuscular mycorrhizal (AM) fungi and/or nitrogen-fixing bacteria. Four treatments were used: (1) plants inoculated with Glomus fasciculatum (Taxter sensu Gerd.) Gerdemann and Trappe and Rhizobium meliloti 102 F51 strain (MR); (2) plants inoculated with only Rhizobium (R); (3) plants inoculated with only mycorrhizae (M); and (4) non-inoculated plants (N). When endophytes were well established, treatments received different levels of phosphorus and nitrogen in the nutrient solution in order to obtain plants similar in size. Sixty days after planting, plants were subjected to two cycles of drought and recovery. Midday leaf water potential (Psi), CO2 exchange rate (CER), leaf conductance (g(w)) and transpiration (T), as well as leaf and root abscisic acid (ABA) and cytokinin concentrations were measured after the second drought period. Gas exchange parameters were determined by infrared gas analysis. Cytokinins and ABA levels in tissues were analysed by ELISA and HPLC, respectively. Nodulated R and MR plants had the lowest ABA concentrations in roots under well-watered conditions. Water stress increased ABA concentrations in leaves of N, R and MR plants, while ABA concentration in M plants did not change. The highest production of ABA under water deficit was in the roots of non-mycorrhizal plants. The ratio of ABA to cytokinin concentration strongly increased in leaves and roots of non-mycorrhizal plants under drought. By contrast, this ratio was lowered in roots of M plants and remained unchanged in leaves and roots of MR plants when stress was imposed. The highest leaf conductances and transpirational fluxes under well-watered conditions were those of nitrogen-fixing R and MR plants, but these results were not impaired with increased CO2 exchange rates. Photosynthesis, leaf conductance and transpiration rates decreased in all treatments when stress was imposed, with the strongest decrease occurring in non-mycorrhizal plants. The relationships found between these gas exchange parameters and the hormone concentrations in stressed alfalfa tissues suggest that microsymbionts have an important role in the control of gas exchange of the host plant through hormone production in roots and the ABA/cytokinin balance in leaves. The most relevant effect of mycorrhizal fungi was observed under drought conditions.