MYCORRHIZA AND REPEATED DROUGHT EXPOSURE AFFECT DROUGHT RESISTANCE AND EXTRARADICAL HYPHAE DEVELOPMENT OF PEPPER PLANTS INDEPENDENT OF PLANT SIZE AND NUTRIENT CONTENT

Pepper (Capsicum annuum L.) plants with and without VA-mycorrhiza (formed by the fungus Glomus deserticola Trappe, Bloss & Menge), VAM, and NVAM, respectively, were drought acclimated (DA) by four drought cycles or kept well watered (NDA). All plants were then subjected to an additional drought cycle. Similar shoot mass and leaf area were achieved in all treatments by giving more P fertilizer to NVAM than VAM plants. With few exceptions, leaf nutrient concentrations of 12 elements, including P, were either equal or higher in NVAM than VAM plants. During peak drought stress, plants with the combination of VAM-DA treatments had the greatest drought resistance, as indicated by the highest leaf water potential, turgor, relative water content and frequency of non-wilted plants. Some drought resistance, as indicated by intermediate frequency of wilting, occurred when VAM or DA were applied singly. Nutrition and plant size were not associated with this drought resistance. Extraradical hyphae development and soil aggregation of VAM plants were enhanced by drought acclimation, suggesting that these hyphae improved drought resistance by facilitating soil water uptake.