CALCIUM (Ca) 40.08 Atomic weight
Calcium is absorbed by plants as the calcium ion (Ca++). It is an essential part of cell wall structure and must be present for the formation of new cells. Calcium is non-mobile in plants. Young tissue is affected first under conditions of deficiency.
Calcium is the most abundant metallic element in the human body, and the fifth most abundant element in the earth’s crust. Calcium does not occur naturally in the free state, but its compounds make up 3.64% of the earth’s crust.
A deficient level of calcium in the soil impairs plant absorption and retention of other ions such as magnesium. The mechanism responsible for plant discrimination between K+ and Na+ depends on the presence of Ca+.+. A small amount of Calcium in a foliar solution increases the plants uptake of potassium by as much as 150% by changing cell membrane permeability. Maintenance of the plant tissue cell wall structure depends on calcium cross-linkages.
The brown discoloration that occurs in most Calcium deficient tissue could be the result of increased leakage of phenolic compounds into the cytoplasm. Oxidation of some of the enzymes would then occur.
There are basically four biological roles of Calcium in the growth and development of plants:
1) Calcium’s effect on plant membranes.
2) Its effect on cell wall structure
3) Its role in enzyme activities
4) Its interaction with phytohormones
MAGNESIUM (Mn) 24.30 Atomic Weight
Magnesium is the eighth most abundant element in the earth’s crust, comprising 2.5%. It comprises 0.13% of seawater. It is about one sixth as plentiful as Potassium in human body cells, where it serves as a catalyst for enzyme activities in carbohydrate metabolism It does not occur in nature un-combined.
Magnesium is an essential element in both plant and animal life, and is non toxic. Plant uptake is in the form of Magnesium ion (Mg++). The chlorophyll molecule contains magnesium, and it is therefore essential for photosynthesis. Magnesium serves as an activator for many plant enzymes required in growth processes. It is mobile in plants and can be readily translocated from older to younger tissue under conditions of deficiency.
SULFUR (S) 32.06 Atomic Weight
Sulfur (Sulphur) is estimated to be the ninth most abundant element in the universe. It constitutes .03% of the earth’s crust. After Oxygen and Silicon, it is the most abundant constituent of minerals. Sulfur is essential to all life as a component of fats, organic fluids, and bones. It is non-toxic in its elemental form as well as its sulfate compound.
Uptake of Sulfur in plants is in the form of sulfate ions (SO4---). Sulfur may also be absorbed from the air through the leaves in areas where the atmosphere has been enriched with Sulfur compounds from industrial or volcanic sources.
Sulfur is a constituent of two amino acids (methionine and cysteine) and is therefore essential for protein synthesis. It is also essential for nodule formation on legume roots, and is present in oil compounds responsible for plant odor. It helps in chlorophyll formation.