Do plants need calcium supplements? Calcium deficiency makes plants "difficult to survive" and "unpalatable"

Tuchong Creative

What's your first reaction when it comes to calcium? Maybe it's bone health or calcium supplementation. Indeed, calcium is essential for healthy growth and development. But you may not think that calcium is also essential for the normal growth of plants. Why is watermelon sweeter in dry weather? Why does the Albizia Julibrissin close its leaves before a rainstorm? Why does the night-blooming cereus bloom only when night falls? All of these are related to calcium.

Today, let’s talk about calcium and plants.

Our human body can sense changes in the external environment, all of which depends on receptors inside and outside the body, including taste receptors on the tongue, temperature receptors and pressure receptors on the skin. When these receptors are triggered by external signals, they convert the signals into electrical signals and transmit them to the brain through nerve cells, which then responds accordingly.

Plants actually have similar mechanisms in response to environmental changes.

Many previous studies have found that when plants are under adverse conditions, the calcium ion concentration in their cells changes dramatically and rapidly, and this change is indeed related to the plant's ability to resist stress.

As early as 2009, Polish scientist Dorota Konopka-Postupolska conducted an experiment to study the role of membrane-bound proteins that control the entry of calcium ions into cells. After culturing Arabidopsis under short-light conditions for 4 weeks, the Arabidopsis delayed flowering, maintained vegetative growth, and then was subjected to drought treatment.

At the beginning of the experiment, the soil of these Arabidopsis thaliana plants gradually became dry until they were completely dehydrated. The results showed that the annexin-deficient mutant (Atann1) showed wilting symptoms on the 5th day after drought treatment, while the wild type and annexin-overexpressing strains remained green and plump, indicating that annexin may play a role under drought stress conditions.

In other words, plants can indeed sense adverse external conditions and convert this signal into changes in calcium ion concentration. Calcium ions transmit information to corresponding proteins. So which receptors convert external signals into calcium signals inside cells?

In the latest research, scientists from Hunan Agricultural University found that when the water content increases, the plant's hypoosmotic receptors OSCA2.1 and OSCA2.2 will quickly sense the abundant water in the outside world, enhance the calcium signal in the cytoplasm, and thus respond with defense.

In fact, the osmotic receptor OSCA gene family is very old. They first appeared in protists. These genes play a role in maintaining the shape and pressure of protists. After plants came onto land, they faced a more complex water environment. The water content in the soil was sometimes high and sometimes low, and there were occasional changes in water accumulation due to heavy rains and floods. This forced terrestrial plants to develop coping strategies. The expansion and evolution of the plant OSCA gene family played an important role in plants' response to water changes.

The question is, although plants also have sensitive receptors, how do they transmit the detected environmental information to the corresponding cells? After all, there are no specialized nerve cells in the plant body to transmit information. At this time, calcium ions play an important role.

In plant cells, the flow rate of calcium ions is much faster than we thought, reaching 400 microns per second, which sounds slow, but the cells in plant roots are usually only tens of microns, which means that within 1 second, the information has been transmitted to the inside of the root system.

So how do calcium ions get plant cells moving and prepare all cells to cope with extreme environments? This is about a special protein - calmodulin. In cells, each production line has a specific key to start, and calmodulin is a special key that can change its shape as the calcium ion concentration changes, thereby starting different cell production lines. It is no exaggeration to say that calmodulin is like a master key, and it is also smart.

It is worth noting that calcium ions in cells come and go quickly. This is because high concentrations of calcium ions will greatly interfere with the normal functioning of cells. Therefore, within a few seconds, the calcium ion concentration in the cells will return to normal. But at this time, the plants have already prepared for drought, working overtime to produce sugars and amino acids to ensure that they will not be dehydrated due to the drought environment.

Whether a fruit is sweet or not is actually related to calcium. This is something no one would have thought of.

This article is a work supported by the Science Popularization China Creation Cultivation Program. Author: Shi Jun

Reviewer: Gu Lei, Associate Professor, School of Life Sciences, Capital Normal University

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.