Adverse Soil Mineral Availability

This chapter covers our molecular understanding of how plants acquire growth-limiting mineral nutrients and cope with the presence of potentially toxic elements in the soil. Plants rarely experience an ample supply of all 14 essential elements, which have to be taken up from an exceedingly complex system, the soil. Strategies to meet this challenge include tightly controlled nutrient uptake and the plasticity of root architecture. Nutrient status and external availability are constantly monitored and translated into changes in uptake capacity and root morphology. Symbioses are of major importance for plant nutrient acquisition. Mycorrhizae and nitrogen fixation are described in separate sections with respect to the molecular processes involved in partner recognition and establishment, as well as nutrient exchange. The final sections of the chapter elaborate on the mechanisms allowing adapted plants to thrive even when normally toxic concentrations of mostly non-essential elements such as sodium and aluminium are present in the soil. Large areas around the globe are affected by either salinization or the availability of aluminium because of low soil pH. Resistance is often mediated by exclusion of the element or sequestration in vacuoles. Finally, the rare ability of some plant species to hyperaccumulate metals in spite of their toxicity is introduced as an example of plant adaptation to extremely stressful environments.