Physiological Effects of Hydrogen, Aluminum, and Manganese Toxicities in Acid Soil

Abstract

Soil acidity is a major growth-limiting factor for plants in many parts of the world. Soils are acid because their parent materials were acid and initially low in the basic cations or because these elements have been removed from the soil profile by normal rainfall leaching or the harvesting of crops. The direct effects of the hydrogen ion on plant growth are difficult to determine in acid soils, because at soil pH levels where it is considered harmful, aluminum, manganese, and other mineral elements may also be soluble in toxic concentrations, and the availabilities of essential elements, particularly calcium, magnesium, phosphorus, and molybdenum, may be suboptimal. Stress-tolerant and stress-sensitive genotypes are also valuable indicators of present and potential problems of mineral stress in soils, particularly when used in conjunction with conventional soil testing procedures. Vose emphasized the potential value of plant mutants in studying physiological processes.