Effects on Membranes


Historical Information
  Determination of Essentiality
Functions in Plants
  Effects on Membranes
  Role in Cell Walls
  Effects on Enzymes
  Interactions with Phytohormones
  Other Effects
Diagnosis of Calcium Status in Plants
  Symptoms of Deficiency and Excess
  Concentrations of Calcium in Plants
    - Forms of Calcium Compounds
    - Distribution of Calcium in Plants
    - Calcicole and Calcifuge Species
    - Critical Concentrations of Calcium
    - Tabulated Data of Concentrations by Crops
Assessment of Calcium Status in Soils
  Forms of Calcium in Soil
  Soil Tests
  Tabulated Data on Calcium Contents in Soils
Fertilizers for Calcium
  Kinds of Fertilizer
  Application of Calcium Fertilizers

Epstein established that membranes become leaky when plants are grown in the absence of calcium (5) and that ion selectivity is lost. Calcium ions (Ca2+) bridge phosphate and carboxylate groups of phospholipids and proteins at membrane surfaces (6), helping to maintain membrane structure. Also, some effect occurs in the middle of the membrane, possibly through interaction of the calcium and proteins that are an integral part of membranes (6,7). Possibly, calcium may link adjacent phosphatidyl-serine head groups, binding the phospholipids together in certain areas that are then more rigid than the surrounding areas (8).