The Role of Calcium in Plant Growth

Calcium is an essential nutrient for plants and has extremely important physiological functions. Although the calcium content in the soil can generally meet the needs of plants, due to the large-scale and long-term application of chemical fertilizers and unbalanced fertilization, calcium deficiency in plants occurs frequently, causing great economic losses to agricultural production.

As early as the 19th century, calcium was listed as an essential nutrient for plants and was called the "four elements of fertilizer" together with nitrogen, phosphorus and potassium. Calcium is known as the "general regulator of plant cell metabolism". Its importance is mainly reflected in the fact that calcium can bind to calmodulin as an intracellular messenger to regulate many physiological metabolic processes in plants. Especially under environmental stress, calcium and calmodulin participate in the perception, transmission, response and expression of stress signals, and improve the stress resistance of plants.

The role of calcium

1. Calcium is an important component of the cell wall

Most of the calcium in plants is a pectin structural component of the cell wall. It forms pectin calcium with pectin acid and is fixed between two adjacent cell walls, that is, in the middle gelatin layer, to maintain the structure and function of the cell wall. When calcium is deficient, the adhesion between calcium and pectin in the middle gelatin layer is affected, and plant tissues are vulnerable to pathogens. Therefore, calcium can enhance the disease resistance of plants, making crops resistant to storage, transportation and rot.

2. Calcium can stabilize cell membranes

Calcium acts as a link between phosphate and protein carboxyl groups in cell membranes. It is reported that calcium can increase the activity of superoxide dismutase and reduce the content of membrane lipid malondialdehyde, thereby protecting the integrity of cell membrane structure.

3. Calcium acts as a second messenger

Calcium can bind to calmodulin (CaM) in plant cells to regulate enzyme activity, acting as a second messenger for hormone and environmental signal transduction. It is currently believed that cell division and differentiation, cytoskeleton and cell movement, photosynthesis, germination of spores, seeds and pollen, response to hormones, nuclear enzyme system and gene expression are all closely related to CaM.

4. Calcium has a physiological regulatory effect

Calcium can neutralize organic acids generated by plant metabolism, form insoluble organic calcium such as calcium oxalate, calcium citrate, and calcium malate, regulate pH, and stabilize the intracellular environment. Calcium ions can reduce the dispersion of protoplasmic colloids, regulate the colloidal state of protoplasm, and make the cell water filling, viscosity, elasticity, and permeability suitable for crop growth.

5. Calcium and plant cold resistance

Low temperature stress causes a large number of free radicals to be produced in plants, causing damage to the membrane system and causing low temperature damage. Under low temperature stress, calcium can slow down the reduction rate of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in plants. These three enzymes are important protective enzymes in plants, play an important role in removing free radicals, and are closely related to the stress resistance of plants. Therefore, calcium can effectively improve the cold resistance of plants.

6. Calcium and plant drought resistance

Calcium can regulate the activity of certain enzymes, transmit and induce the expression of drought signals, and improve the water retention capacity of plants.

7. Calcium and plant salt tolerance

Calcium can regulate the ion balance in plant cells and reduce the absorption of sodium ions. Recent studies have shown that calcium can promote the selective absorption, transportation and distribution of ions.

For melon and fruit vegetables and fruit trees, calcium is a nutrient element that is easy to lack and difficult to supplement.

What should we pay attention to when applying calcium fertilizer?

1. Choose appropriate calcium fertilizer and use reasonable application methods

The traditional calcium fertilizers applied to the soil mainly include lime, calcium nitrate, calcium chloride, calcium carbonate, superphosphate and calcium magnesium phosphate fertilizer. Calcium fertilizers with high solubility such as calcium nitrate and calcium chloride can be dissolved and sprayed, or watered immediately after applying calcium fertilizer to the soil to dissolve, so as to improve fertilizer utilization. Superphosphate should be applied after composting with organic fertilizer. Calcium chloride is easy to cause soil salinization and is rarely used in production. Large-scale application of lime is easy to cause soil pH to rise, affecting the soil microbial environment.

At present, liquid calcium fertilizer is recommended for facility vegetables and fruit trees. Liquid calcium fertilizers mostly use chelating agents to increase the stability of calcium, such as amino acid calcium, humic acid calcium and sugar alcohol chelated calcium. Currently, the most advanced and efficient technology is sugar alcohol chelation. This type of sugar alcohol chelated calcium can not only improve the absorption rate of calcium, but also absorb it through the leaves and fruit surfaces, and can be used after bagging.

2. Pay attention to supplementing boron at the same time when supplementing calcium

In order to increase the application effect of liquid calcium fertilizer, elements such as boron and zinc are added to liquid calcium fertilizer. Boron fertilizer plays a key role in the growth and development period of fruits. It can promote flower bud differentiation and increase fruit setting rate and fruiting rate. Boron has a more significant effect, which is its strong transportation capacity. Boron can make carbohydrates in plants work, which is equivalent to the commander-in-chief. It quickly delivers the elements and nutrients needed by various organs, which is conducive to leaf absorption, so that crops can grow normally.

3. Functional fertilizers can be used appropriately

When applying calcium fertilizers, functional fertilizers can be used in combination to promote root growth, improve the ability of crops to absorb nutrients, and improve crop resistance.