Abstract
Research Highlights: Drought stress significantly decreased the performance of seedlings in the nursery. Seedlings inoculated with Claroideoglomus etunicatum is recommended to produce superior planting stock of mahogany seedlings with better drought resistance in the nursery. Background and Objectives: With numerous intense droughts across tropical regions due to climate change, it is crucial to understand effects of drought stress on tree seedlings to improve crop management practices and avoid failures on large scale planting. Swietenia macrophylla, a commercial timber species in India, is poorly studied in relation to its management including physiological responses to various environmental stresses. Arbuscular mycorrhizal fungi (AMF) is known to improve performance of tree seedlings under drought conditions and produce quality planting stock in nursery. This study aims to understand the responses of mahogany seedlings under different levels of drought stress when inoculated with three types of AMF, namely Funneliformis mosseae, Claroideoglomus etunicatum, and Rhizophagus intraradices. Materials and Methods: The experiment is conducted in pot culture using a factorial completely randomized design. Different irrigation regimes were applied at 100, 80, 60, and 40 percentage of weekly cumulative evapotranspiration. The seedlings were tested for biometric, physiological, and mycorrhizal parameters periodically. Results: Physiological attributes such as rate of photosynthesis, stomatal conductance, transpiration rate, chlorophyll content, and water potential were found to be higher in the daily irrigated (control) seedlings. Performance of the seedlings were poorest in the least irrigated treatment. It was apparent that inoculated seedlings performed better than the non-inoculated ones. Conclusions: Among the three different AMF species used, C. etunicatum was found to be the most beneficial and suitable for the young mahogany seedlings. These seedlings also recorded higher root colonization percentage and total spore count in the rhizosphere soils. Seedlings inoculated with C. etunicatum showed positive influence on rate of photosynthesis, stomatal conductance, transpiration rate, chlorophyll content, relative growth rate (RGR) and water potential of seedlings.
Highlights
Changing environmental conditions induced by climate change create abiotic stress in tree seedlings which has detrimental effect on its growth and productivity
The seedlings treated with R. intraradices (1.44 μ mol CO2 m−2 s−1 ) and C. etunicatum (1.29 μ mol CO2 m−2 s−1 ) showed higher rate of photosynthesis compared to non-inoculated seedlings
The results shows that arbuscular mycorrhizal fungi (AMF) inoculated seedlings were less stressed than non-inoculated ones which could be related to a combination of increased water uptake by mycorrhizal roots, high soil-to-plant hydraulic conductance and improved stomatal conductance in response to high water potential [30,42,46]
Summary
Changing environmental conditions induced by climate change create abiotic stress in tree seedlings which has detrimental effect on its growth and productivity. Tree seedlings in their first year of planting lack extensive and deep root systems. This root system is not adequate to access the receding soil water levels created by drought conditions [4]. Silvicultural, and management strategies could be employed for improving the adaptive capacity of these seedlings to drought stress [5]. One such strategy that could increase the rate of seedling survival would be planting nursery grown seedlings inoculated with suitable arbuscular mycorrhizal fungi (AMF) [6]. There is considerable evidences to suggest that AMF symbiosis can enhance the tolerance of associated host plants to water deficit [8]
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