Mycorrhizal Inoculation and High Arsenic Concentrations in the Soil Increase the Survival of Soybean Plants Subjected to Strong Water Stress

Soybean (Glycine max L.) cropping is increasing in marginal environments, including water-limited lands, some of which are loaded with arsenic (As). Plants inoculated with mycorrhiza increased their tolerance to water stress. We studied the effect of a sudden and severe water stress on soybean inoculated with the mycorrhizal fungus Glomus intraradices in soils with increasing concentrations of As. Soybean plants were grown in greenhouse with adequate water supply for 60 days. Irrigation was stopped completely and soil abruptly reached the permanent wilting point. Most inoculated plants survived under such limiting water stress, but noninoculated plants were clearly affected. Arsenic showed a negative effect on plant growth but improved plant survival under this severe water stress. It seems that the negative effects of As on plant water equilibrium explain why plants affected by As survived extreme water stress events.