Influence of phosphorus and endomycorrhiza (Glomus intraradices) on gas exchange and plant growth of chile ancho pepper (Capsicum annuum L. cv. San Luis)

Seedlings of chile ancho pepper were grown in pots containing a pasteurized mixture of sand and a low phosphorus (P) sandy loam soil, and either inoculated (VAM) or not inoculated (NVAM) with the endomycorrhizal fungus Glomus intraradices. Long Ashton nutrient solution (LANS) was modified to supply P to the seedlings at 0, 11, and 44 g(P) m(-3) (P-0, P-11, P-44, respectively). Low P depressed net photosynthetic rate (P-N), stomatal conductance (g(s)), phosphorus use efficiency (P-N/P), and internal CO2 concentration (C-i). The mycorrhiza alleviated low P effects by increasing P-N g(s), P-N/P, and decreasing C-i. At P-0, C-i of NVAM plants was equal to or higher than that of VAM plants, suggesting nonstomatal inhibition of photosynthesis. Gas exchange of VAM plants at P-0 was similar to that of NVAM plants at P-11. Endomycorrhiza increased leaf number, leaf area, shoot, root and fruit mass at P-0 and P-11 compared to NVAM plants. Reproductive growth was enhanced by 450% in mycorrhizal plants at P-44 Root colonization (arbuscules, vesicles, internal and extraradical hyphae development) was higher at lower P concentrations, while sporulation was unaffected. The enhanced growth and gas exchange of mycorrhizal plants was in part due to greater uptake of P and greater extraradical hyphae development.