Do Mycorrhizae Influence the Drought Tolerance of Citrus?

The benefits of vesicular-arbuscular mycorrhizal (VAM) fungi for increasing drought tolerance have been demonstrated under nutrient-limiting conditions, particularly in low phosphorus (P) soils. Horticultural plants grown in soilless media, under greenhouse fertilizer regimes, are usually non-mycorrhizal, but have optimum P and the desired size and nutritional characteristics available when transplanted. Since plant nutrition can influence responses to environmental stress, potential benefits of VAM fungi for reducing transplant stress, such as drought, should be evaluated where growth and nutrition of mycorrhizal and non-mycorrhizal plants are similar at time of outplanting. In this way, nutritional and any unique non-nutritional effects of mycorrhizae on stress tolerance of plants can be identified. Non-nutritional effects of VAM fungi on drought tolerance of woody horticultural plants have not yet been clearly demonstrated.