Role Of Calcium in Plants

ROLE OF CALCIUM IN PLANT CULTURE AND SOIL

Role of Calcium in Plant Culture Along with Magnesium and Sulfur, Calcium is one of the three secondary nutrients. Like primary nutrients (nitrogen, phosphorus and potassium), those elements are essential for healthy plant growth. However, they are needed in lesser amounts. Function of Calcium: Calcium, in the form of calcium pectate, is responsible for holding together the cell walls of plants. When calcium is deficient, new tissue such as root tips, young leaves, and shoot tips often exhibit distorted growth from improper cell wall formation. Calcium is also used in activating certain enzymes and to send signals that coordinate certain cellular activities. Calcium Deficiency: Calcium is not mobile within the plant. So the plant relies on the process of transpiration in which the plant roots take up the soil solution (which contains the needed calcium), transports it to new growth where the calcium is used and the excess water vapor escapes out through holes in the leaves called stomata. Anything that slows transpiration, such as high humidity or cold temperatures, can induce calcium deficiency even if the calcium levels are normal in the growing medium. Parts of the plant that transpire little water, i.e. young leaves and fruit, will display calcium deficiencies first. Blossom end rot of tomatoes is a classic case of calcium deficiency. Calcium deficiency can arise if levels in the fertilizer solution are less than 40-60 ppm and/or potassium, magnesium, or sodium levels are too high. Calcium deficiency causing leaf edge necrosis in Poinsettia, bract edge burn, blossom end rot of tomatoes.

Calcium Toxicity: Calcium toxicity rarely occurs. High levels of calcium can compete with magnesium and potassium uptake, causing their deficiencies. Calcium Source-Fertilizer: Not all fertilizers contain calcium, such as those with a significant percentage of phosphorus, so it is important to read the label. Some fertilizers list the percentage of calcium and magnesium in the fertilizer analysis, i.e. 15-7-14-3Ca-1Mg. Those that are identified as a “Cal-Mag” such as 15-5-15, 17-5-17, etc., will contain calcium. If you are not certain that a fertilizer contains calcium, check the percentage list of ingredients in the fertilizer. Note: Most calcium-containing fertilizers are formulated with calcium nitrate. Keep in mind that calcium nitrate is potentially basic, meaning it will cause the pH of the growing medium to rise unless acid is injected or potentially acidic fertilizers are used in rotation. Calcium Source-Water: All water sources supply some calcium. As a general rule, water coming from deep wells or most noncoastal regions of North America has sufficient calcium for normal crop growth, while water from a shallow well, coastal region, rain, lake, river or pond generally has insufficient calcium levels. Regardless, it is best to have your water tested to verify if your water is supplying sufficient calcium. If the calcium level in your water is 40-60 ppm or more, then there is little need to use a fertilizer that provides calcium. MOBILITY AND UPTAKE OF CALCIUM BY PLANTS Calcium uptake by the plant is passive and does not require energy input. Calcium mobility in the plant takes places mainly in the xylem, together with water. Therefore calcium uptake is directly related to the plant transpiration rate. Conditions of high humidity, cold and a low transpiration rates may result in calcium deficiency. Salinity buildup might also cause calcium deficiency because it decreases the water uptake by the plant. Since calcium mobility in plants is limited, calcium deficiency will appear in younger leaves (die back or burns) and in fruits (blossom end rot, bitter pit), because they have a very low transpiration rate. Therefore, it is necessary to have a constant supply of calcium for continued growth.

Calcium is an essential plant nutrient. It has many roles: Participates in metabolic processes of other nutrients uptake. Promotes proper plant cell elongation. Strengthen cell wall structure - calcium is an essential part of plant cell wall. It forms calcium pectate compounds which give stability to cell walls and bind cells together. Participates in enzymatic and hormonal processes. Helps in protecting the plant against heat stress - calcium improves stomata function and participates in induction of heat shock proteins. Helps in protecting the plant against diseases - numerous fungi and bacteria secret enzymes which impair plant cell wall. Stronger Cell walls, induced by calcium, can avoid the invasion. Affects fruit quality. Has a role in the regulation of the stomata. FACTORS AFFECTING THE AVAILABILITY OF CALCIUM TO PLANTS Calcium forms insoluble compounds with other elements in soil, such as phosphorous. Calcium that is in the form of an insoluble compound is not available to plants. Since calcium is a positively charged ion, it is adsorbed in the soil to the surface of clay and organic particles which are negatively charged. Positively charged ions adsorbed to soil particles are termed "exchangeable ions" because they can be exchanged by other ions present in the soil solution. Soil analysis determines the level of exchangeable calcium ions, and not the total calcium in soil, because the exchangeable calcium is the form which is available to the plant. Several factors in the soil analysis can help in assessing the availability of calcium to plants: Soil pH - usually soils with a higher pH level contain more available calcium. CEC - this is a soil characteristic that describes the total amount of positively charged exchangeable ions that the soil can hold. A higher CEC indicates a higher capacity of the soil to adsorb and hold calcium, and therefore higher calcium availability. Presence of competing ions - calcium competes with other positively charged ions, such as sodium (Na+), potassium (K+), and magnesium (Mg+2). Applying too much of these positively charged ions might decrease calcium uptake by plants. Sodium ions can replace the adsorbed calcium, damage soil structure and decreases calcium availability.

OTHER REACTIONS OF CALCIUM IN SOIL Calcium-phosphorous precipitation - when free calcium accumulates in the soil solution (e.g. when soil pH is high), calcium tend to form insoluble compounds with phosphorous. Consequently, phosphorous availability is also significantly decreased. Calcium stabilizes soil structure - the calcium that is adsorbed to soil particles helps in stabilizing the soil structure. Adsorbed sodium might cause the soil to crack when dry and swell up when wet. Calcium replaces the adsorbed sodium and prevents damages to soil structure. SOURCES OF CALCIUM FOR PLANTS The most common calcium sources are calcium nitrate, calcium chloride, lime, gypsum, calcium chelates and some organic sources. ✿My Planting Hobby❁