Khodayari Samira, Abedini Fatemeh, Renault David
Department of Plant Protection, Faculty of Agriculture, University of Maragheh, P.O. Box 55181-83111, Maragheh, Iran.
Department of Horticultural Sciences, Faculty of Agriculture, University of Maragheh, P.O. Box 55181-83111, Maragheh, Iran.
Exp Appl Acarol. 2018 May;75(1):41-53. doi: 10.1007/s10493-018-0246-y. Epub 2018 Mar 29.
The plant stress hypothesis posits that a herbivore's reproductive success increases when it feeds on stressed plants, while the plant vigor hypothesis predicts that a herbivore preferentially feeds on more vigorous plants. We examined these opposing hypotheses by growing spider mites (Tetranychus urticae) on the leaves of stressed and healthy (vigorous) cucumber plants. Host plants were grown under controlled conditions at low, moderate, and high concentrations of NaCl (to induce salinity stress), at low, moderate, and high fertilizer concentrations (to support growth), and without these additions (control). The effects of these treatments were evaluated by measuring fresh and dry plant biomass, carotenoid and chlorophyll content, antioxidant enzyme activity, and concentrations of PO, K, and Na in plant tissues. The addition of low concentrations of fertilizer increased dry mass, protein, and carotenoid content relative to controls, suggesting a beneficial effect on plants. The highest NaCl treatment (2560 mg L) resulted in increased Na and protein content relative to control plants, as well as reduced PO, K, and chlorophyll levels and reduced catalase and ascorbate peroxidase enzyme activity levels. Analysis of life table data of T. urticae mites raised on leaves from the aforementioned plant groups showed the intrinsic rate of increase (r) for mites was 0.167 day in control specimens, 0.125 day for mites reared on plants treated with a moderate concentration of fertilizer (10 mL L), and was highest (0.241 day) on plants grown under moderate salinity conditions (1920 mg L NaCl). Reproductive success of T. urticae did not differ on plants watered with a moderate concentration of NaCl or a high concentration of fertilizer. The moderately-stressed plants formed a favorable environment for the development and reproduction of spider mites, supporting the plant stress hypothesis.
植物胁迫假说认为，当食草动物取食受胁迫的植物时，其繁殖成功率会增加，而植物活力假说则预测，食草动物会优先取食更具活力的植物。我们通过在受胁迫和健康（有活力）的黄瓜植株叶片上饲养叶螨（二斑叶螨）来检验这些相互对立的假说。寄主植物在受控条件下生长，设置低、中、高浓度的氯化钠（以诱导盐胁迫）、低、中、高肥料浓度（以促进生长）以及不添加这些物质的对照组。通过测量植物的鲜重和干重、类胡萝卜素和叶绿素含量、抗氧化酶活性以及植物组织中磷、钾和钠的浓度来评估这些处理的效果。与对照组相比，添加低浓度肥料增加了干重、蛋白质和类胡萝卜素含量，表明对植物有有益影响。最高氯化钠处理浓度（2560毫克/升）导致相对于对照植株，钠和蛋白质含量增加，同时磷、钾和叶绿素水平降低，过氧化氢酶和抗坏血酸过氧化物酶活性水平降低。对在上述植物组叶片上饲养的二斑叶螨的生命表数据进行分析表明，对照组叶螨的内禀增长率（r）为0.167/天，在中等浓度肥料（10毫升/升）处理的植株上饲养的叶螨为0.125/天，而在中等盐度条件（1920毫克/升氯化钠）下生长的植株上饲养的叶螨内禀增长率最高（0.241/天）。在中等浓度氯化钠或高浓度肥料浇灌的植株上，二斑叶螨的繁殖成功率没有差异。中等胁迫的植株为叶螨的发育和繁殖形成了有利环境，支持了植物胁迫假说。
