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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.
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