Abstract
Catalpa bungei C.A.Mey. is a common ornamental timber species. Its survival and growth are greatly affected by water scarcity in arid and semi-arid areas of Northwest China. Evidence suggests arbuscular mycorrhizal fungus (AMF) may improve plant drought resistance. However, there is limited information on the systematic effects of AMF on drought resistance in C. bungei seedlings. Here, a pot experiment was used to explore the effects of inoculation with the AMF Rhizophagus intraradices on the growth and physiological performance of C. bungei under different water treatment conditions. Three water levels and two mycorrhizal inoculation treatments were used with factorial design. The results showed that drought stress noticeably affected the growth and physiological performance of C. bungei seedlings. However, inoculation with R. intraradices significantly ameliorated the growth, and alleviated the effects of drought stress. The growth parameters of AMF-inoculated seedlings significantly increased regardless of water status. AMF changed the biomass allocation in seedlings by reducing the root mass ratio (RMR) and root/shoot ratio. AMF-inoculated seedlings displayed higher gas exchange parameters, photosynthetic pigment concentrations, specific leaf area (SLA), but lower specific leaf weight (SLW), regardless of water status. AMF alleviated drought-induced oxidative stress by attenuating the excess generation of reactive oxygen species (ROS), especially H2O2 and O2−, in leaves. Inoculation with AMF under drought stress also dramatically augmented indole-3-acetic acid (IAA) and gibberellins (GA3) levels and the IAA/abscisic acid (ABA) and GA3/ABA ratios, but reduced ABA and zeatin (ZT) levels in leaves. AMF symbiosis improved root morphology and promoted the absorption of nitrogen (N) and phosphorus (P) in seedlings. We conclude that inoculation with R. intraradices is potentially useful for afforestation and cultivation of C. bungei in Northwest China. Furthermore, AMF improved soil structure by increasing the glomalin-related soil protein (GRSP) contents and the proportion of macro-aggregates (0.25–0.5 mm) in the rhizosphere soil.
Highlights
Drought is one of the most important factors affecting plant growth in terrestrial ecosystems [1].Climate change increases the odds of severe drought conditions around the world [2,3]
No arbuscular mycorrhizal fungus (AMF) colonization was found in the roots of non-inoculated C. bungei seedlings (Figure 2A), whereas clear colonization by R. intraradices was observed in the mycorrhizal inoculated seedlings
There was no significant difference in the EE-glomalin-related soil protein (GRSP) and total glomalin-related soil protein (T-GRSP) contents among the three water treatments, Forestsaddition, 2020, 11, 1117 under drought stress, the ZT/abscisic acid (ABA) and GA3/ABA ratios were significantly higher in the15 of 29 leaves of non-mycorrhizal treated seedlings than under WW conditions. These results showed that drought stress could stimulate the accumulation of hormones to a certain extent, could change their regardless of the inoculation status (p > 0.5), which indicated that water stress had little effect on proportion, and had an overall greater impact on these growth regulators in the leaves of the GRSP
Summary
Drought is one of the most important factors affecting plant growth in terrestrial ecosystems [1].Climate change increases the odds of severe drought conditions around the world [2,3]. Drought is one of the most important factors affecting plant growth in terrestrial ecosystems [1]. Drought stress can change plant water status, and has obvious effects on seed germination, plant morphological structure, biomass distribution, soil nutrient availability, photosynthesis, and metabolism, thereby seriously restricting the normal growth, development, survival, and productivity of plants [3,4,5,6]. Plants adapt to drought by making morphological and physiological adjustments through the synergistic. Attempts to enhance plant drought resistance are being made to improve forestry and agricultural productivity and reduce water consumption. One of the strategies used to enhance plant drought resistance is inoculation with AMF [2,7,8]
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