Physiological and photosynthetic responses of melon (Cucumis melo L.) seedlings to three Glomus species under water deficit

Melon (Cucumis melo L.)—an important horticultural crop that is often cultivated in simply equipped solar greenhouses in northwestern regions of China—usually suffers under poor water management. Arbuscular mycorrhizal (AM) symbiosis can play a major role in enhancing drought tolerance. Plant growth, physiological, and photosynthetic responses of melon plants inoculated with three Glomus species under two water conditions were investigated. Results show that inoculation with Glomus improves the physiological and photosynthetic parameters of inoculated seedlings compared with non-AM seedlings. Regardless of water conditions, plant height, root length, biomass production, antioxidant enzyme activity, soluble sugar content, net photosynthetic rate, and photosynthetic water use efficiency were elevated in AM seedlings compared to non-AM seedlings. Each Glomus species manifests unique effects under the two watering conditions. We posit that AM symbiosis can protect melon plants against water deficiencies by improving their antioxidant activity, bi-directional transport of carbohydrates, and photosynthetic capacity. In addition, regardless of water conditions, the most efficient fungus for melon (Cucumis melo L.) was Glomus mosseae.