Introduction:
Like any other living thing, plants are vulnerable to stress. Any internal or external factors that interfere with the natural growth and development of plants and also lowers its productivity and efficiency is referred to as plant stress. In order to overcome these unconditional situations, plants have evolved a variety of stress-response mechanisms such as changes in gene expression, the synthesis of stress proteins, and the formation of metabolites and ions. Therefore, this ability of a plant to endure and thrive in difficult environmental conditions is referred to as stress tolerance. Plants have evolved a variety of methods to deal with stress and preserve growth and productivity.
Types of Stress in plant:
Plants can experience a variety of stresses in their environment that can affect their growth, development, and productivity. Here are some common types of stress that plants may encounter:
Abiotic stress: This type of stress is caused by non-living factors in the environment, such as drought, salinity, extreme temperatures (hot or cold), high light intensity, heavy metals, and air pollution.
Biotic stress: This type of stress is caused by living organisms, such as insects, pathogens (bacteria, viruses, fungi), and herbivores. Biotic stress can also be caused by competition with other plants for resources.
Fig: Different types of Stress in plants
Nutritional stress: This type of stress is caused by a lack of essential nutrients, such as nitrogen, phosphorus, and potassium, in the soil or growing medium.
Chemical stress: This type of stress is caused by exposure to toxic chemicals, such as pesticides, herbicides, and pollutants.
Physical stress: This type of stress is caused by physical damage to the plant, such as mechanical injury, wind, and flooding.
Water Stress: This type of stress occurs when plants do not receive enough water, or when they receive too much water. Water stress can affect plant growth and development, and can lead to dehydration, wilting, and even death.
Metabolism under stress in plant:
Drought, heat, cold, salt, nutrient inadequacy, disease and pest exposure are all sources of stress for plants. Plants activate several metabolic and physiological processes in response to stress in order to adapt to the new conditions.
An increase in the production of stress-related hormones such as abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA) is one of the key metabolic changes that occur during plant stress. These hormones cause a variety of reactions, including stomatal closure, changes in gene expression, and the activation of defensive mechanisms.
Plants adjust their primary metabolism when they are under stress, producing more reactive oxygen species (ROS) and accumulating sugars and other solutes that are compatible with ROS, such as proline. By protecting cellular structures and preserving cellular balance, these substances enable plants in responding with stress.
Under stress, plants can also adjust their secondary metabolism. Plants under drought stress, for instance, may produce more flavonoids, which are known to have anti-inflammatory and antioxidant properties.
Overall, stress-induced metabolic alterations in plants are crucial for their survival and ability to adapt to their environment. In order to improve plant resistance to stress and maximize agricultural production and quality in the context of climate change and other environmental problems, researchers can benefit from better understanding of these processes.
Role of ion and metabolic accumulation in plant during stress:
Plant responses to stress are significantly influenced by the accumulation of ions and metabolic. Ions like potassium, calcium, and sodium aid in cellular homeostasis and osmotic balance, while metabolites like proline, sugars, and organic acids serve as osmoprotectants and antioxidants like ascorbate and glutathione aid in scavenging reactive oxygen species during stress. These ions, metabolites, and antioxidants all play important roles in how plants adapt to and respond to stress.
| Soluble sugars (e.g. sucrose, glucose, fructose) | Polyamines, such as spermidine and spermine, are positively charged molecules that accumulate in plants under stress. They have been shown to have a variety of protective functions, such as stabilizing cellular membranes, protecting against oxidative stress, and regulating gene expression. |
| Phytohormones | Can regulate gene expression and signaling pathways involved in stress responses; examples include abscisic acid (ABA), salicylic acid (SA), and jasmonic acid (JA) |
| Polyamines (e.g. spermidine, spermine) | Stabilizes cellular membranes, protects against oxidative stress, and regulates gene expression. |
| Potassium (K+) | Maintains turgor pressure and regulates stomatal function. |
| Sodium (Na+) | Toxic to plants in excess, but can be accumulated in small amounts to help maintain osmotic balance under salt stress. |
| Calcium (Ca2+) | Regulates ion transport, activates enzymes involved in stress signaling, and regulates gene expression. |
| Mg2+ | Can help activate enzymes involved in photosynthesis and energy metabolism, which can be disrupted by stress. |
Heat shock protein (HSP):
Heat shock proteins (HSPs) are proteins produced when cells are unexpectedly exposed to temperatures higher than their typical growth temperature. HSP synthesis is a ubiquitous phenomenon that has been observed in all plant and animal species studied, including humans. Prokaryotic cells, such as bacteria and archaea, also produce HSPs. HSPs are commonly referred to as “stress proteins” because they can be induced by oxidants, toxins, heavy metals, free radicals, viruses, and other stressors such as amino acid analogues, inflammatory cytokines, oxidative stress, or ischemia.
Heat shock proteins (HSPs) are an important component of plant stress response, especially in response to high temperature stress. Plants have a complex network of HSPs that are created in response to heat stress, allowing them to function effectively in hot environments.
HSPs play a role in a range of cellular functions in plants, including protein folding and transport, protein complex building and disassembly, and stress-induced damage prevention. HSP synthesis is controlled by a number of signaling pathways and transcription factors that are activated in response to stress.
HSPs operate as molecular chaperones under heat stress circumstances, assisting other proteins in folding correctly and preventing them from aggregating or denaturing. They also aid in the degradation of misfolded or damaged proteins, which can accumulate in stressed cells and cause cellular malfunction. By performing these functions, HSPs can protect plants from heat stress-induced damage and maintain cellular homeostasis.
Types of HSPs:
Heat shock proteins (HSPs) are a group of proteins that are produced in response to stress, including heat stress. They are classified into different types based on their molecular weight and cellular functions:
HSP100: These are the largest HSPs and are involved in protein disaggregation and degradation.
HSP90: These HSPs are involved in the folding and stabilization of proteins and play important roles in signal transduction pathways.
HSP70: These HSPs are involved in protein folding, transport, and degradation. They bind to partially folded proteins and prevent their aggregation.
HSP60: These HSPs are involved in the folding of newly synthesized proteins and in the refolding of denatured proteins.
Small HSPs: These are the smallest HSPs and are involved in the protection of cells from stress-induced damage.
References:
- Ul Haq S, Khan A, Ali M, Khattak AM, Gai WX, Zhang HX, Wei AM, Gong ZH. Heat Shock Proteins: Dynamic Biomolecules to Counter Plant Biotic and Abiotic Stresses. Int J Mol Sci. 2019 Oct 25;20(21):5321.
- Zhu, C., Ding, Y. and Liu, H., 2011. MiR398 and plant stress responses. Physiologia plantarum, 143(1), pp.1-9.
- Salam U, Ullah S, Tang ZH, Elateeq AA, Khan Y, Khan J, Khan A, Ali S. Plant Metabolomics: An Overview of the Role of Primary and Secondary Metabolites against Different Environmental Stress Factors. Life (Basel). 2023 Mar 6;13(3):706.
- Pagare, S., Bhatia, M., Tripathi, N., Pagare, S. and Bansal, Y.K., 2015. Secondary metabolites of plants and their role: Overview. Current Trends in Biotechnology and Pharmacy, 9(3), pp.293-304.