Carbon-isotope discrimination, water use efficiency, net photosynthesis and transpiration in mycorrhizal kinnow (Citrus nobilis x C. deliciosa) plants

摘要

In a field experiment, three-year-old Kinnow trees budded on Jatti Katti (Citrus jambhiri) rootstock were inoculated with three different arbuscular mycorrhizal fungus (AMF), Glomus manihotis (T₁), Glomus mosseae (T₂) and Gigaspora gigantea (T₃) separately or in combination (T₄). Plants were grown under an ordinary field management program with a non-limiting supply of water and fertilized with only farm yard manure. Mycorrhizal infection increased transpiration rate by 46% with T₁ followed by T₄, T₃ and T₂ (30, 11 and 3%, respectively) over non-mycorrhizal plants. Photosynthetic rate under saturated light condition increased 44% with T₄ followed by T₃ and T₁ (13 and 10%, respectively). Photosynthetic water use efficiency enhanced slightly as determined on the single leaf level ( micro mol CO₂/mol H₂O) or by carbon isotope discrimination ( Delta 13C). These data were also used to analyze correlation between Delta and water use efficiency (WUE) and some other plant attributes. A strong positive correlation between Delta and WUE (r=0.622**) and between Delta and transpiration rate (r=0.697**) was observed. WUE showed higher dependence on photosynthesis (r=0.578*) rather than transpiration rate (r=0.209).