干旱胁迫下AMF对云南蓝果树幼苗生长和光合特征的影响

采用盆栽试验与称重控水法,将土壤相对含水量分别控制在田间最大持水量的100%、91.68%、82.85%、60.00%、41.86%和21.28%,并在这6个不同的土壤相对含水量条件下,分别设添加苯菌灵(杀真菌剂)(低AMF)和不添加苯菌灵(高AMF)处理,研究干旱胁迫下AMF对极小种群野生植物云南蓝果树幼苗生长和光合特征的影响,揭示云南蓝果树濒危的微生物学机制,为云南蓝果树保护措施的制定与实施奠定基础。结果表明,添加苯菌灵处理显著降低了不同水分条件下的AMF侵染率,说明试验中AMF处理的实生苗在生长和光合特征上的差异是苯菌灵处理下侵染率下降导致的;随着干旱胁迫的加剧,云南蓝果树幼苗的根部AMF侵染率显著降低、叶面积等生长指标和净光合速率(Pn)等光合参数都发生显著变化;高AMF处理可以显著增加水分充足和轻度干旱胁迫条件下云南蓝果树幼苗的大部分生长指标和光合参数,而对重度胁迫下的云南蓝果树幼苗没有显著影响,说明重度干旱胁迫对其影响大于AMF的影响;另外,整合了可塑性指数分析和隶属函数分析两种方法对其抗旱性进行评价,云南蓝果树幼苗基本上无法通过调节形态和光合能力来适应水分环境的变化,但是高AMF处理可使云南蓝果树幼苗具有较强的可塑性和更强的抗旱性。实验结果为云南蓝果树的科学保育及种苗繁育提供了理论依据。

Effects of arbuscular mycorrhizal fungi on growth and photosynthetic characteristics of Nyssa yunnanensis seedlings under drought stress

Among various environmental stresses, drought stress has become a critical problem worldwide due to its dramatic effects on plant growth and physiology, and recently, this has attracted much attention. Arbuscular mycorrhizal fungi (AMF) have previously been reported to afford greater resistance to drought stress in some plant species. The aim of this study was to determine the impacts of AMF on growth and photosynthetic characteristics of Nyssa yunnanensis seedlings through addition (Low AMF) or non-addition (High AMF) of the fungicide benomyl at each water treatment. We further aimed to elucidate drought resistance and associated microbiological mechanisms of this endangered plant species, which would help to establish and implement protection measures. In this study, a pot experiment was conducted to control the soil water content, and 100, 91.68, 82.85, 60.00, 41.86, and 21.28% of field moisture capacity were set. The seedlings were subjected to different watering regimes and measurements were made at the end of the experiment to investigate the growth and photosynthetic characteristics of N. yunnanensis seedlings. Plasticity index analysis and principal component analysis of 18 indices of N. yunnanensis were integrated and analyzed using the membership function method to evaluate synthetic drought resistance. These variables provide a theoretical basis for a better understanding of the mechanism of AMF on the tolerance of N. yunnanensis seedlings to drought stress. The results showed that the AMF colonization rate of N. yunnanensis roots significantly decreased under "Low AMF" treatments, indicating that differences in the growth and photosynthetic characteristics of AMF-treated seedlings were caused by a reduction in the rate of AMF colonization in N. yunnanensis roots. With the intensification of drought stress, the AMF colonization rate of N. yunnanensis roots significantly decreased and changed both growth parameters, including leaf area, and photosynthetic characteristics, including net photosynthetic rate of N. yunnanensis seedlings. High AMF significantly enhanced N. yunnanensis tolerance to the imposed drought stress by improving both growth parameters and photosynthetic characteristics under conditions of adequate moisture and mild drought stress. Nevertheless, there were no significant differences between AMF treatments under severe drought stress, indicating that this had more significant effects on N. yunnanensis seedlings than did AMF. The results also demonstrated that the N. yunnanensis seedlings could not adapt to diverse water stress through plastic responses in morphology and photosynthesis, whereas high AMF treatments led to higher plastic differences in both growth parameters and photosynthetic characteristic. N. yunnanensis seedlings showed stronger drought resistance under high AMF conditions. The experimental results provide a theoretical basis for the scientific conservation and breeding of N. yunnanensis. In conclusion, N. yunnanensis seedlings did not show resistance to drought stress, but plants were dependent on mycorrhizae under water stress, which partially compensated its effects.