Adaptation of Plants to Adverse Chemical Soil Conditions

Publisher Summary This chapter focuses on the various constraints faced by plants in adverse soil conditions such as acidity, poor aeration, alkalinity, and salinity. The low-external input high-efficiency involving adapted genotypes that efficiently uses the nutrients from soil reserves and fertilizer can lead to yields that are only 10–20% below the maximum. Two components that contribute to overall nutrient efficiency include uptake efficiency, which is the amount of nutrient absorbed, and utilization efficiency, which characterizes the efficiency with which the absorbed nutrients are utilized to produce yield. Both of them primarily depend on the nutrient supply by the soil and fertilizers. The main constraints to plant growth in flooded or submerged soils are the low oxygen availability, Fe and Mn toxicity and toxic metabolites of anaerobic decomposition. Adaptation to flooded soils includes aerenchyma formation to transport oxygen to the roots, efficient generation and use of energy and carbohydrate conservation. Plant growth in alkaline or calcareous soils is inhibited by low availability of Fe, Zn, Mn and B and tolerance to such soils is achieved by mobilization of Fe and Zn via exudation of chelating compounds such as organic acid anions in Strategy I plants and phytosiderophores in Strategy II plants. The main constraints to plant growth in saline soils are low osmotic potential and ion toxicity (Na, Cl, sulphate) as well as ion imbalances (low K/Na ratio). The salt tolerance mechanisms can be divided into salt exclusion (reduced uptake, increased efflux) and salt inclusion (compartmentation into the vacuole, release of salts via salt glands, and salt-tolerant enzymes).