CONICET | Buscador de Institutos y Recursos Humanos

Soybean (Glycine max) is an economical important crop with a great expansion even to arid andsemiarid regions. This crop is often grown in soils with moderate to high arsenic concentrations and/orsoils irrigated with arsenic contaminated groundwater. Little is known about the changes on soybeangrowth and metabolism and under arsenate (AsV) or arsenite (AsIII) exposure. The first sensing events likeincrease in phosphatidic acid (PA), a key messenger in plants, would be in part responsible of triggeringtolerance response for adaptation and survival to arsenic stress such as rapid stomatal closure, rootstructural alterations and antioxidant enzymes induction. Despite tolerance response, arsenic treatedsoybean seeds and seedlings show deleterious effects on germination and growth such as root tip cell death,membrane lipoperoxidation and chlorophyll content reduction. Microscopic analysis of root cross-sectionsshowed reduction in the cortex area, broken cells and dark deposits in the vascular system. All these allchanges would contribute with metalloid phytoxicity reduction by reactive oxygen species (ROS)scavenging, water status preservation and prevention of arsenic translocation to the aboveground tissues.Moreover, obstruction of the vascular system could explain the low level of arsenic found in aerial partsand grains with a major accumulation in roots. Inoculation with Bradyrhizobium japonicum E109, which isthe N2 fixing bacterium most used as inoculant in Argentina, was not successful in attenuating arsenicdeleterious effects on soybean growth since bacterial survival, motility and symbiosis (number of effectivenodules) were negatively affected. Although soybean grain consumption would not be a health problembecause arsenic translocation to aerial parts is depreciable, the negative impact of this metalloid on soybeanproduction is considerable. Novel biotechnological strategies like inoculation with arsenic tolerant plantgrowth promoting bacteria (PGPB) and co-inoculation with B. japonicum must be developed to achievesustainable soybean production in arsenical soils.

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