Science

Abiotic and Biotic Plant Stress

Have you ever thought what causes a plant to get stressed? The answer to this question is the same with plants, just as the source of stress in humans is the living organisms that can cause disease or damage in humans. In this article, what is the stress seen in plants and what are the reasons, there is information about them.

What is Stress in Plants?

Plants are exposed to a wide range of environmental stresses that reduce and limit the productivity of agricultural products. There are two types of environmental stresses in plants that can be categorized as abiotic stress and biotic stress. Abiotic stress causes loss of large crop plants worldwide and includes radiation, salinity, flood, drought, extreme temperature, heavy metals etc. On the other hand, attacks of various pathogens such as fungi, bacteria, oomycetes, nematodes and herbivores are included in biotic stresses. Since plants are silent in nature, there is no choice to escape these environmental clues. Plants have developed various mechanisms to overcome these biotic and abiotic stress threats. They perceive the external stress environment, are stimulated, and then produce appropriate cellular responses. They do this by stimuli transmitted to the transcriptional machine taken from the sensors located in the cell surface or cytoplasm and placed in the nucleus with the help of various signal transmission paths. This leads to transcriptional changes that make the plant tolerant to stress. Signaling pathways act as a link bond and play an important role between sensing the stress environment and producing an appropriate biochemical and physiological response.

Causes of Stress

Water Stress

Water stress is one of the most important abiotic stresses that affect plants. A plant needs a certain amount of water for optimal survival; too much water (flood pressure) can cause plant cells to swell and burst; Drought stress (too little water) can cause the plant to dry out, which is called drying. Both conditions can be deadly for the plant.

Temperature Stress

Temperature stresses can wreak havoc on a plant. Like any living organism, a plant has an optimal temperature range where it grows and performs best. If the temperature is too cold for the plant, it can cause cold stress, also called cooling stress. Extreme cold stress forms can cause freezing stress. Cold temperatures can affect the intake and rate of water and nutrients, causing cell dryness and hunger. Under extremely cold conditions, cell fluids may freeze, causing plant death.

Hot weather can also negatively affect crops. Intense heat can cause plant cell proteins, a process called denaturation, to break down. Cell walls and membranes can also melt at extremely high temperatures, and the permeability of the membranes is affected.

Other Abiotic Stress

Other abiotic stresses are less pronounced, but can be equally fatal. Eventually, most abiotic stress affects plant cells in the same way as water stress and temperature stress. Wind stress can either directly damage the plant or affect wind sweating through the wind leaf stoma and cause drying. Burning plants by direct fires will cause cell structure to break down by melting or denaturation.

In agricultural systems, the addition of agricultural chemicals such as fertilizer and pesticides may cause abiotic stress to the plant. The plant is affected by nutritional imbalance or toxicity. A high amount of salt taken by a plant can cause cell drying, as high levels of salt outside the plant cell will cause water to escape from a cell called osmosis. Plant intake of heavy metals can occur when grown in soils fertilized with improperly combined sewage sludge. High heavy metal content in plants can lead to complications with basic physiological and biochemical activities such as photosynthesis.

Biotic Stress

Biotic stresses damage plants through living organisms, including bacteria, fungi, weeds, and insects. Viruses cause biotic stress on plants, although they are not considered living organisms. Fungi cause more disease in plants than other biotic stress factors. Why plant disease of over 8,000 fungal species is known. On the other hand, according to the Ohio State University Extension publication, only about 14 bacterial species cause economically important diseases in plants. Many plants do not have pathogenic viruses, but according to published estimates, they are as serious as fungi worldwide, almost as serious as causing product damage Microorganisms can cause plant fading, leaf spots, root rot or seed damage. Insects can cause serious physical damage to plants, including leaves, stems, bark and flowers. Insects can also act as a vector of viruses and bacteria from infected plants to healthy plants.

Polyamine: Plant Response to Stress

Plants that are immobile in nature have to experience constant fluctuations in the environment with appropriate physiological, developmental and biochemical changes. More than 50% reduction in crop plants is caused by worldwide abiotic stresses, which is the main cause of product loss. To counteract stress, plants are equipped with a large set of defense mechanisms. Among the different compatible soluble classes, polyamines are one of the most effective against extreme environmental stress. Polyamines are low molecular weight aliphatic nitrogen compounds positively charged at physiological pH. Research on plant polyamines at the molecular level has led to the isolation of a number of genes encoding polyamine biosynthetic enzymes from various plant species. In recent years, molecular and genomic studies with mutants and transgenic plants with or without enzyme activity in the biosynthesis of polyamines have contributed to a better understanding of the biological functions of polyamines in plants.

Polyamine and Plant Response to Biotic Stress

It is known that polyamine metabolism begins to deteriorate in plant cells that respond to insight changes in plants that interact with fungal, viral pathogens and mycorrhiza. It is difficult to identify the contribution of the accumulation of polyamine in infected organs, as it is present in both plants and pathogenic fungi. With the specific inhibition of polyamine biosynthesis, the probability of control of fungal plant diseases is the most exciting and most effective for achieving development.

The world temperature is expected to rise by 3-5 ° C in the next 50–100 years. Flood and drought changes are always taken into account, as there is a continuous increase in temperature and irregular precipitation. Anthropogenic activities, such as excess fertilizers, improper irrigation and the use of metal resources, can lead to a great deal of salt stress. Under these conditions, plants will likely encounter both biotic and abiotic stresses more often. It is the task of plant growers to develop stress-resistant varieties to ensure food safety and safety for farmers. Molecular studies will be conducted at the genetic level to develop mechanisms in plants to protect them from different stress conditions.

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