what is abiotic stress in plants

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What causes stress in plants?

Plant Stresses: Abiotic and Biotic Stresses Water Stress. One of the most important abiotic stresses affecting plants is water stress. A plant requires a certain... Temperature Stress. Temperature stresses can also wreak havoc on a plant. As with any living organism, a plant has an... Other Abiotic ...

How do abiotic stress affect plant nutrient dificiency?

Abiotic stresses and soil nutrient limitations are major environmental conditions that reduce plant growth, productivity and quality. Plants have evolved mechanisms to perceive these environmental challenges, transmit the stress signals within cells as well as between cells and tissues, and make appropriate adjustments in their growth and development in order to survive and reproduce.

Do positive interactions increase with abiotic stress?

The “stress gradient hypothesis” (SGH hereafter; Bertness and Callaway, 1994) states that positive interactions should be “particularly common” or increase in “frequency” under stressful conditions. The SGH predicts that the relative importance of facilitation and competition will vary inversely across gradients of abiotic stress, with facilitation being dominant under stressful conditions.

What are 5 examples of abiotic factors?

What are 5 abiotic factors in the savanna? Solar energy from the sun. Light from the sun. Climate and temperature. Wind, rain, and other weather. Fires. Oxygen and other gasses in the atmosphere. Soil and everything in it. Pollution.

What is mean by abiotic stress in plants?

Abiotic stresses, such as low or high temperature, deficient or excessive water, high salinity, heavy metals, and ultraviolet radiation, are hostile to plant growth and development, leading to great crop yield penalty worldwide.

What is biotic and abiotic stress in plants?

Abiotic stress includes temperature, ultraviolet radiation, salinity, floods, drought, heavy metals, etc., which results in the loss of important crop plants globally, while biotic stress refers to damage caused by insects, herbivores, nematodes, fungi, bacteria, or weeds.

How do plants respond to abiotic stress?

As sessile organisms, plants must cope with abiotic stress such as soil salinity, drought, and extreme temperatures. Core stress signaling pathways involve protein kinases related to the yeast SNF1 and mammalian AMPK, suggesting that stress signaling in plants evolved from energy sensing.

How abiotic stress conditions affects plant roots?

Low soil temperature results in reduced tissue nutrient concentrations and as such decreases root growth Lahti et al. [114]. Lateral root formation is inhibited by low temperature. Root growth and temperature generally increase together up to a point.

What is plant biological stress?

Biotic stress is an adverse condition in which plant cannot sustain its normal growth due to the interaction with deleterious microorganisms (fungi, bacteria, viruses, viroids, phytoplasma, and nematodes).

What is the example of biotic stresses?

Biotic stress includes various plant pathogens such as bacteria, fungi, viruses, nematodes, insects, and others. Pathogen infection frequently results in changes in plant physiology, the loss of biomass, early flowering, the decreased seed set, the accumulation of protective metabolites, and many other changes.

What are abiotic stresses causing disease in plants give 10 examples?

Unfavorable soil properties, fertility imbalances, moisture extremes, temperature extremes, chemical toxicity, physical injuries, and other problems are examples of abiotic disorders that can reduce plant health and even kill plants.

What are the 5 abiotic factors?

The most important abiotic factors include water, sunlight, oxygen, soil and temperature. Water (H2O) is a very important abiotic factor – it is often said that “water is life.” All living organisms need water.

How can you prevent plant stresses?

5 Ways Your Plants Can Avoid Stress1) Eat Healthy.2) Create a Stress-Free Environment.3) Take Advantage of New Strategies in Stress Prevention.4) Get to the Root of the Issue.5) Get Professional Advice and Regular Checkups.

How do plants treat abiotic disease?

How to Treat Abiotic DisordersTesting soil and fertilizing accordingly.Collecting and testing samples to identify and treat pests or diseases.Aerating compacted soil with an air tool to “fluff” it without damaging roots.Pruning to help a tree recover from damage caused by storms, road salt, or extreme temperatures.

What is root system in plants?

The root system is the descending (growing downwards) portion of the plant axis. When a seed germinates, radicle is the first organ to come out of it. It elongates to form primary or the tap root. It gives off lateral branches (secondary and tertiary roots) and thus forms the root system.

What are fibrous roots?

Thin, branched roots that arise from the base of the stem are known as fibrous roots. Grasses and monocotyledons are characterised by the presence of fibrous roots. The roots are moderately branched, but once a tree fully matures it gives a mat-like appearance.

What is shoot system in plants?

Shoot system is an aerial and erect part of plant body which grows upwards. It is usually above the soil and develops from plumule of the embryo. It consists of stem, branches, leaves, flowers, fruits and seeds.

What is abiotic stress PDF?

Abiotic stress in the other hand appears due to the adverse effects of non-living environmental factors i.e. water, temperature, light, metal, mineral nutrients etc. on plants which are often sporadic and are highly localized.

What is an abiotic pressure?

Abiotic pressure is created by non-living factors within the organism's environment, such as light, wind, and soil. All of these factors interact with the organism to provide opposition to its continued survival.

Is soil biotic or abiotic?

Soil is composed of both biotic—living and once-living things, like plants and insects—and abiotic materials—nonliving factors, like minerals, water, and air. Soil contains air, water, and minerals as well as plant and animal matter, both living and dead.

What is meant by biotic and abiotic?

Biotic and abiotic factors are what make up ecosystems. Biotic factors are living things within an ecosystem; such as plants, animals, and bacteria, while abiotic are non-living components; such as water, soil and atmosphere.

How do biotic and abiotic factors affect crop production?

Biotic factors like insects, rodents, pests, and many more spread the disease and reduce crop production. Abiotic factors like humidity, temperature, moisture, wind, rain, flood, and many more destroy the crop raised.

What are the 5 abiotic factors?

The most important abiotic factors include water, sunlight, oxygen, soil and temperature. Water (H2O) is a very important abiotic factor – it is often said that “water is life.” All living organisms need water.

Is soil biotic or abiotic?

Soil is composed of both biotic—living and once-living things, like plants and insects—and abiotic materials—nonliving factors, like minerals, water, and air. Soil contains air, water, and minerals as well as plant and animal matter, both living and dead.

What is abiotic stress?

Abiotic stress is defined as the negative impact of non-living factors on living organisms in a specific environment. The stresses include drought, salinity, low or high temperatures, and other environmental extremes. Abiotic stresses, especially hypersalinity and drought, are the primary causes of crop loss worldwide.

How does abiotic stress affect plant survival?

Abiotic stress negatively influences plant survival and plant productivity. Usually, multiple genes are responsible for controlling stress resistance response; hence it limits the breeding applications to improve crops with abiotic stress tolerance. Multiple genes associated with salinity, cold, drought, and heat stress adaptation have been identified through physiological studies as well as molecular mechanisms (Bressan et al., 2009 ).

How does abiotic stress affect the cell?

During abiotic stress the biosynthesis and accumulation of different molecules thought to have protective functions in the cells is induced . These molecules are thought to mediate their protective function by their interaction with, or stabilizing of, different cellular components such as membrane elements or proteins/enzymes whose structure or function are sensitive and can be damaged as a result of the low temperature. For some of these protective molecules the biosynthetic pathways were described and genes encoding specific key enzymes in the pathways were identified and subjected to molecular manipulations to modulate biosynthesis (Bhatnagar-Mathur et al., 2008 ). In cases where these protective molecules contribute to plant chilling tolerance, key biosynthetic or regulatory genes could serve as potential targets for biotechnological manipulations for improving cold tolerance for fresh produce during postharvest storage.

What causes crop loss?

Abiotic stress, particularly soil salinity, drought, and extreme temperature, is a leading cause of crop loss. As water resources decline and desertification intensifies in response to climate change, such losses are likely to worsen.

What are the environmental conditions that affect crop productivity?

Abiotic stress such as, drought, high soil salinity, heat, cold, oxidative stress and heavy metal toxicity is the common adverse environmental conditions that affect and limit crop productivity worldwide. Use of microbes may be a promising alternative strategy to overcome the limitations to crop production brought by abiotic stress ...

Why are microbes important for plant health?

Use of microbes may be a promising alternative strategy to overcome the limitations to crop production brought by abiotic stress and for better plant health and protection because they are environmental friendly, cost-effective and can also provide protection against biotic stresses.

How does osmotic effect affect plant growth?

Osmotic effect influences the plant growth due to the ion imbalance. Ionic imbalance can be reduced by making a way out of ions through vacuoles using different promoters. Overexpression of vacuolar Na + /H + antiporter ( NHX1) and the H + translocating pyrophosphatase ( AVP1) genes have been reported to increase Na + into the vacuole, and thus enhancing both accumulation and tolerance to Na + ( Gaxiola et al., 2001; Pasapula et al., 2011 ). Further, plants produce or accumulate many organic compounds such as amino acid (proline), quaternary, amines (glycine betaine and polyamines), normal sugars (fructose and sucrose), complex sugars (trehalose and fructans), and organic acids (oxalate and malate) to protect cellular proteins under stress conditions ( Valliyodan and Nguyen, 2006 ). These osmoprotectants defend plant cells under osmotic as well as other stress conditions without affecting the biochemistry of the cellular environment. The transgenic tomato overexpressing yeast trehalose-6-phosphate synthase genes showed tolerance to salinity, drought, and oxidative stresses ( Cortina and Culiáñez-Macià, 2005 ). In cold stress, C-repeat binding factor (CBF), a transcription factor, has been reported to be a modulator of genes which impart freezing tolerance by accumulating cryoprotective molecules such as proline, raffinose, and sucrose ( Kaplan et al., 2004; Thomashow, 2010; Zhao et al., 2016 ). Mzid et al. (2018) reported that overexpression of grape gene (VvWRKY2) in tobacco enhanced plant tolerance to salt as well as osmotic stresses. The accumulation of osmolytes also provides support to maintain the osmotic level in plant cells. Hence, enhancing the expression of known antiporters, osmoprotectants and cryo protectants genes and transcription factors through CRISPR/Cas9 mediated knock-in approach can ensure the development of plants having high tolerance under different stress conditions.

What is abiotic stress?

Stress on organisms caused by nonliving factors. Abiotic stress is the negative impact of non-living factors on the living organisms in a specific environment. The non-living variable must influence the environment beyond its normal range of variation to adversely affect the population performance or individual physiology ...

Why is abiotic stress important for organisms?

Lastly, abiotic stress has enabled species to grow, develop, and evolve, furthering natural selection as it picks out the weakest of a group of organisms.

What are the most common abiotic stress factors?

The most basic stressors include: High winds. Extreme temperatures.

What is the most harmful factor in crop production?

Abiotic stress is the most harmful factor concerning the growth and productivity of crops worldwide. Research has also shown that abiotic stressors are at their most harmful when they occur together, in combinations of abiotic stress factors.

How is biodiversity determined?

Biodiversity is determined by many things, and one of them is abiotic stress. If an environment is highly stressful, biodiversity tends to be low. If abiotic stress does not have a strong presence in an area, the biodiversity will be much higher.

How does abiotic stress affect ecosystems?

The higher the latitude of the area affected , the greater the impact of abiotic stress will be on that area . So, a taiga or boreal forest is at the mercy of whatever abiotic stress factors may come along, while tropical zones are much less susceptible to such stressors.

How does drought affect plants?

Drought stress defined as naturally occurring water deficit is one of the main causes of crop losses within the agricultural world. This is due to water's necessity in so many fundamental processes in plant growth. It has become especially important in recent years to find a way to combat drought stress. A decrease in precipitation and subsequent increase in drought are extremely likely in the future due to an increase in global warming. Plants have come up with many mechanisms and adaptations to try and deal with drought stress. One of the leading ways that plants combat drought stress is by closing their stomata. A key hormone regulating stomatal opening and closing is abscisic acid (ABA). Synthesis of ABA causes the ABA to bind to receptors. This binding then affects the opening of ion channels thereby decreasing turgor pressure in the stomata and causing them to close. Recent studies, by Gonzalez-Villagra, et al., showed how ABA levels increased in drought-stressed plants (2018). They showed that when plants were placed in a stressful situation they produced more ABA to try and conserve any water they had in their leaves. Another extremely important factor in dealing with drought stress and regulating the uptake and export of water is aquaporins (AQPs). AQPs are integral membrane proteins that make up channels. These channels' main job is the transport of water and other necessary solutes. AQPs are both transcriptionally and post transcriptionally regulated by many different factors such as ABA, GA3, pH and Ca2+ and the specific levels of AQPs in certain parts of the plant, such as roots or leaves, helps to draw as much water into the plant as possible. By understanding both the mechanism of AQPs and the hormone ABA, scientists will be better able to produce drought resistant plants in the future.

What are the abiotic stresses that affect plants?

Plants cannot move, so they must endure abiotic stresses such as drought, salinity and extreme temperatures. These stressors greatly limit the distribution of plants, alter their growth and development, and reduce crop productivity. Recent progress in our understanding of the molecular mechanisms underlying the responses of plants to abiotic stresses emphasizes their multilevel nature; multiple processes are involved, including sensing, signalling, transcription, transcript processing, translation and post-translational protein modifications. This improved knowledge can be used to boost crop productivity and agricultural sustainability through genetic, chemical and microbial approaches.

What are the factors that regulate abiotic stress?

Numerous genetic, biochemical and molecular studies have identified many of the factors that regulate abiotic stress responses, and it is now clear that abiotic stress elicits multilevel responses, involving stress sensing, signal transduction, transcription, transcript processing, translation and post-translational protein modifications (Fig. 1 ). These responses can be initiated in various cellular structures and compartments, including the cell wall, plasma membrane, cytoplasm, nucleus, chloroplasts, mitochondria, endoplasmic reticulum and peroxisomes (reviewed in ref. 3) (Fig. 1 ). Furthermore, whereas some responses are common to multiple stressors (such as detoxification of over-accumulated reactive oxygen species (ROS)), others are stress-specific (such as ionic stress responses specifically induced by high salinity 3 ).

What is the role of protein phosphorylation in plant responses to abiotic stress?

Protein phosphorylation is a common and critical event in signal transduction during plant responses to various abiotic stress conditions (Figs 2, 3 ). As shown in A. thaliana and conserved in crops such as rice and maize, members of the type 2C protein phosphatase (PP2C) family and the SnRK2 protein kinase subfamily are central players in multiple stress signalling pathways. They regulate various downstream proteins, including transcription factors, the plasma membrane anion channel SLAC1 that controls stomatal closure and the plasma membrane NADPH oxidase RbohF that generates extracellular hydrogen peroxide (H 2 O 2) 39, 40, 41, 42, 43, 44, 45 (Fig. 2 ). SnRK2s are activated by the phytohormone ABA, which is a key mediator of stomatal closure and other plant responses to salt, drought and several other hyperosmotic stress-inducing conditions. ABA binds to its receptor proteins (the PYR/PYL/RCAR family of small soluble proteins), allowing the receptors to physically interact with and inhibit the activity of clade A PP2Cs such as ABI1 and ABI2 (refs 46, 47 ). As a result, several SnRK2s are released from their association with and inhibition by the PP2Cs (ref. 48 ). However, not all SnRK2s are reliant on ABA for activation. For example, SnRK2.6/OST1 is activated independently of ABA in response to cold stress 49, and ABA-independent activation of SnRK2s by some B2/B3/B4 clades of Raf-like kinases (RAFs) in the MAP kinase kinase kinase (MAP3K) family occurs in response to osmotic stress 50, 51, 52, 53, 54; the RAF-activated SnRK2s can then phosphorylate other SnRK2s that are released from PP2Cs by PYL–ABA but not yet activated to amplify the osmotic stress and ABA responses 55. Although the SnRK3 family has been shown to function downstream of Ca 2+ signalling (as discussed above), it is unclear if and how SnRK2s are connected to Ca 2+ signalling.

How do environmental stressors affect plant cells?

Environmental stressors can directly cause physical or chemical changes to biomolecules in the plant cell, which trigger a cellular stress response . It is difficult to demonstrate that a biomolecule directly senses stress, so most putative stress sensors have been identified using indirect approaches. For example, disrupting the function of sensors is expected to affect the levels of second messengers such as Ca 2+, ROS, nitric oxide and phospholipids, and genetic screens have been designed to identify mutations that cause such phenotypes. In particular, the intracellular concentration of free Ca 2+ rapidly displays stimulus-specific patterns in response to external stressors, which has enabled sensing of osmolarity, salt and temperature stress to be studied in genetic screens of transgenic plants expressing aequorin-based Ca 2+ indicators.

How do plants respond to environmental stress?

To withstand environmental stresses, plants have evolved interconnected regulatory pathways that enable them to respond and adapt to their environments in a timely manner. Abiotic stress conditions affect many aspects of plant physiology and cause widespread changes in cellular processes. Some of the changes are non-adaptive responses that simply reflect damage inflicted by a stressor, such as the detrimental changes in membrane fluidity and protein structure caused by heat or cold stress, and the disruptions in enzyme kinetics and molecular interactions caused by toxic ions. However, many of the changes are adaptive responses that lead to increased stress resistance and are therefore potential targets for crop improvement. Processes involved in the adaptive response include the repair of stress-induced damage, the rebalancing of cellular homeostasis and the adjustment of growth to levels suitable for the particular stress condition 2, 3.

Why do plants lose their flavour when stored in cold?

For instance, tomato ( Solanum lycopersicum) fruits lose flavour during cold storage because cold treatment represses the transcription of the DNA demethylase gene DML2; the resulting increase in DNA methylation levels at the promoters of genes responsible for the biosynthesis of flavour volatiles leads to silencing of their expression 149 (Fig. 5b ).

How can genetics help crops?

Genetic, biochemical and molecular studies in model plants as well as crops have improve d our understanding of abiotic stress responses at multiple molecular levels. Key regulators at any of these levels are potential targets for manipulation to protect crops from stresses. Improving crop productivity under stress conditions requires cross-disciplinary approaches that integrate genetic methods such as CRISPR–Cas-based gene editing, treatments with chemicals such as the ABA receptor agonist AMF4 (which has long-lasting effects in promoting stomatal closure and inducing the expression of drought-responsive genes 191) and inoculation with beneficial microbes.

What are the abiotic stresses that plants must cope with?

As sessile organisms, plants must cope with abiotic stress such as soil salinity, drought, and extreme temperatures. Core stress signaling pathways involve protein kinases related to the yeast SNF1 and mammalian AMPK, suggesting that stress signaling in plants evolved from energy sensing. Stress signaling regulates proteins critical for ion and water transport and for metabolic and gene-expression reprogramming to bring about ionic and water homeostasis and cellular stability under stress conditions. Understanding stress signaling and responses will increase our ability to improve stress resistance in crops to achieve agricultural sustainability and food security for a growing world population.

How does cold stress affect plant metabolism?

The effect on plant metabolism arises from both direct inhibition of metabolic enzymes by cold temperatures and reprogramming of gene expression (Chinnusamy et al., 2007). In temperate plants, an exposure to low, nonfreezing temperatures enhances the tolerance to subsequent freezing temperatures, a process known as cold acclimation. Cold stress rapidly induces the expression of many transcription factors, including the AP2-domain proteins CBFs, which then activate the expression of numerous downstream cold responsive (COR) genes (Chinnusamy et al., 2007). The CBFgenes are controlled by upstream transcription factors, including the bHLH transcription factor ICE1. ICE1 is subjected to sumoylation, and polyubiquitylation and subsequent proteasomal degradation, mediated by the SUMO E3 ligase SIZ1 and ubiquitin E3 ligase HOS1, respectively (Chinnusamy et al., 2007). Cold stress induction of the CBFand CORgenes is gated by the circadian clock, whose activity is modulated by diurnal oscillation of the plastid retrograde signal tetrapyrroles (Norén et al., 2016).

How does salinity affect agriculture?

Soil salinity affects a substantial percentage of cultivated land and is a significant factor limiting agricultural productivity worldwide. High salt levels cause ion toxicity (mainly Na+), hyperosmotic stress, and secondary stresses such as oxidative damage (Zhu, 2002). It is not known how Na+is sensed in any cellular system. In the yeast S. cerevisiae, the calcineurin pathway plays a major role in Na+stress signaling and tolerance (Thewes, 2014). Na+stress-triggered cytosolic calcium binds to the EF-hand calcium-binding proteins calmodulin and the B subunit of calcineurin (CnB). Ca2+-CnB and Ca2+-calmodulin activate the phosphatase catalytic subunit of calcineurin, CnA. The activated phosphatase dephosphorylates the zinc finger transcription factor CRZ1, which then moves to the nucleus to activate the expression of ENA1and other target genes. ENA1encodes a Na+-ATPase that pumps the toxic Na+out of the cell, thus restoring ion homeostasis. Plant genomes do not encode any calcineurin proteins, even though the name calcineurin B-like (CBL) has been widely used to refer to a family of plant EF-hand calcium-binding proteins (Yu et al., 2014). Plants instead use a calcium-dependent protein kinase pathway known as the Salt-Overly-Sensitive (SOS) pathway for salt stress signaling and Na+tolerance (Zhu, 2002) (Figure 2). In this pathway, the EF-hand calcium-binding protein SOS3 senses the cytosolic calcium signal elicited by salt stress. SOS3 interacts with and activates SOS2, a serine/threonine protein kinase. SOS3 is preferentially expressed in the root, and an SOS3 paralog, SCaBP8/CBL10 mainly expressed in the shoot, performs an equivalent role as SOS3 (Quan et al., 2007). The activated SOS2 phosphorylates and activates SOS1, a Na+/H+antiporter at the plasma membrane (Zhu, 2002).

What causes plastid metabolites to increase?

High light and other stresses can also cause increases in the level of the plastid metabolite methylerythritol cyclodiphosphate (MEcPP), a precursor of isoprenoids. MEcPP functions as a retrograde signal to activate the expression of stress-responsive nuclear genes that encode plastid proteins (Xiao et al., 2012). Another plastid metabolite important for stress responses is the phosphonucleotide 3'-phosphoadenosine 5'-phosphate (PAP). PAP levels increase following drought and high light stress (Estavillo et al., 2011). SAL1/FRY1 is a bifunctional phosphatase that can dephosphorylate both inositol phosphates and PAP (to AMP), and its dysfunction causes PAP accumulation. PAP inhibits 5’ to 3’ exoribonucleases, contributing to the enhanced expression of a subset of drought- and high light-responsive genes and to altered drought resistance (Estavillo et al., 2011). In addition to PAP and MEcPP, other chloroplast metabolites, such as the tetrapyrroles (Norén et al., 2016) and oxidative breakdown products of β-carotene (Ramel et al., 2012), have been proposed as retrograde signals. How stress modulates the levels of MEcPP, PAP, tetrapyrroles, and other retrograde signaling metabolites is not well understood.

What is ER stress?

Both biotic and abiotic stress can cause protein misfolding or the accumulation of unfolded proteins, which is sensed as ER stress by specific sensor proteins in the ER membran e. This sensing leads to the expression of genes encoding chaperones and other proteins important for enhancing protein folding capacity, ER-associated degradation (ERAD), or protein translation suppression to reduce the amount of synthesized proteins loaded to ER via the PKR-like ER eIF2a kinase (Walter and Ron, 2011). These changes help restore ER homeostasis, i.e., the equilibrium between protein-folding demands and folding capacity, and are known as the unfolded protein response (UPR), a conserved stress response in eukaryotes (Walter and Ron, 2011). Two main types of sensors of ER stress have been identified in plants: ER membrane-associated transcription factors and an RNA splicing factor (Liu and Howell, 2016) (Figure 1B). The basic leucine zipper bZIP28 may sense heat and other ER stress agents through its interaction with the chaperone protein BIP (binding immunoglobulin protein) in the ER. Unfolded or misfolded proteins accumulate under stress, and these proteins can interact with BIP, which releases bZIP28 for transport to the Golgi, where it is cleaved. Its cytosolic portion then relocates to the nucleus to activate the expression of stress-response genes to restore ER homeostasis. bZIP28 may also sense other changes that promote its release from BIP, including alterations in energy charge levels and redox status or interactions between BIP and the DNAJ domain-containing protein chaperone (Liu and Howell, 2016). bZIP17 can be activated by salt stress in a similar manner. In addition, several ER- or plasma membrane-associated NAC transcription factors can be activated by ER stress and contribute to UPR (Liu and Howell, 2016). The second type of ER stress sensor in plants is IRE1, a splicing factor conserved from yeast to metazoans. Presumably, plant IRE1 proteins bind to unfolded proteins and sense ER stress in a manner similar to their yeast homolog. Activated IRE1 in Arabidopsis recognizes and splices bZIP60 mRNA and perhaps other target mRNAs. The splicing of bZIP60 mRNA by IRE1 results in a bZIP60 variant that can enter the nucleus to activate UPR genes (Liu and Howell, 2016).

Where does stress signaling occur?

Stress sensing is often compared to ligand perception, so it is frequently thought to occur on the cell surface or at the cell membrane. Then, the signal would be relayed to various subcellular locations such as the nucleus. Theoretically, physical stress signals, particularly temperature signals, may be sensed anywhere in the cell, as long as the stress signal causes a change in the status of the cellular component (protein, DNA, RNA, carbohydrate, or lipid) or compartment (e.g., metabolic reaction in a compartment), and as long as that change then affects other cellular components or activities. Stress-induced changes in protein folding in the ER are now widely recognized as an important cellular response to stress conditions, referred to as ER stress. Similarly, there is stress associated with other organelles such as the chloroplast, mitochondrion, peroxisome, nucleus, and cell wall, and the stress-generated signals from all organelles are integrated to regulate stress responsive gene expression and other cellular activities to restore cellular homeostasis (Figure 1A).

What is the sensor for hyperosmotic stress?

A putative sensor for hyperosmotic stress is the Arabidopsis OSCA1 (reduced hyperosmolality-induced calcium increase 1) (Yuan et al., 2014). Osmotic stress agents, high salt, cold, and heat as well as oxidative stress, heavy metals, and ABA, can cause increases in the cytosolic free calcium concentration in plants, which can be detected by researchers using genetically encoded aequorin or other calcium reporters. Arabidopsis osca1loss-of-function mutants display a reduced calcium spike compared to wild-type plants when treated with osmotic stress agents such as sorbitol and mannitol (Yuan et al., 2014). OSCA1encodes a plasma membrane protein that forms hyperosmolality-gated calcium-permeable channels. Because these mutant plants do not display any drought or salt stress phenotypes, the physiological significance of OSCA1 under the stress conditions is unclear. We do not know how OSCA1 senses osmotic stress, which is expected to reduce turgor and thus may affect membrane stretching and membrane–cell wall interactions. A number of mechano-sensitive channels are known in non-plant systems, including TRP, MscS-like, Piezo, DEG/ENaC, and K2P (Arnadottir and Chalfie, 2010; Hedrich, 2012). Animal TRP channels are well-known calcium channels that can sense changes in the membrane caused by fluctuations in temperature or osmotic pressure (Arnadottir and Chalfie, 2010). Plants lack TRP and DEG/ENaC genes but contain a family of MscS-like proteins and one Piezo homolog (Hedrich, 2012). One of the MscS-like proteins in Arabidopsis, MSL8, is required for pollen to survive hypo-osmotic shock during hydration, suggesting MSL8 as a sensor of hypo-osmotic stress-induced membrane tension (Hamilton et al., 2015). Plants also have a large family of cyclic nucleotide-gated channels (CNGCs) as well as a family of glutamate receptor-like (GLR) channels that are potentially very important in generating cytosolic Ca2+signals under stress (Swarbreck et al., 2013).

What are the abiotic stresses that plants must cope with?

As sessile organisms, plants must cope with abiotic stress such as soil salinity, drought, and extreme temperatures. Core stress-signaling pathways involve protein kinases related to the yeast SNF1 and mammalian AMPK, suggesting that stress signaling in plants evolved from energy sensing.

What is stress signaling?

Stress signaling regulates proteins critical for ion and water transport and for metabolic and gene-expression reprogramming to bring about ionic and water homeostasis and cellular stability under stress conditions.

What are the biotic and abiotic stresses on plants?

The resistant genes against these biotic stresses present in plant genome are encoded in hundreds. The biotic stress is totally different from abiotic stress, which is imposed on plants by non-living factors such as salinity, sunlight , temperature, cold, floods and drought having negative impact on crop plants.

What are the abiotic stresses that affect plant productivity?

These abiotic stresses are interconnected with each other and may occur in form of osmotic stress, malfunction of ion distribution and plant cell homeostasis.

What are the two main categories of stress in plants?

Plant stress can be divided into two primary categories namely abiotic stress and biotic stress .

What are the effects of stress on plants?

Stress in plants refers to external conditions that adversely affect growth, development or productivity of plants [ 1 ]. Stresses trigger a wide range of plant responses like altered gene expression, cellular metabolism, changes in growth rates, crop yields, etc. A plant stress usually reflects some sudden changes in environmental condition. However in stress tolerant plant species, exposure to a particular stress leads to acclimation to that specific stress in a time time-dependent manner [ 1 ]. Plant stress can be divided into two primary categories namely abiotic stress and biotic stress. Abiotic stress imposed on plants by environment may be either physical or chemical, while as biotic stress exposed to the crop plants is a biological unit like diseases, insects, etc. [ 1 ]. Some stresses to the plants injured them as such that plants exhibit several metabolic dysfunctions [ 1 ]. The plants can be recovered from injuries if the stress is mild or of short term as the effect is temporary while as severe stresses leads to death of crop plants by preventing flowering, seed formation and induce senescence [ 1 ]. Such plants will be considered to be stress susceptible. However several plants like desert plants (Ephemerals) can escape the stress altogether [ 2 ].

How does biotic stress affect plants?

Biotic stress in plants is caused by living organisms, specially viruses, bacteria, fungi, nematodes, insects, arachnids and weeds. The agents causing biotic stress directly deprive their host of its nutrients can lead to death of plants. Biotic stress can become major because of pre- and postharvest losses. Despite lacking the adaptive immune system plants can counteract biotic stresses by evolving themselves to certain sophisticated strategies. The defense mechanisms which act against these stresses are controlled genetically by plant’s genetic code stored in them. The resistant genes against these biotic stresses present in plant genome are encoded in hundreds. The biotic stress is totally different from abiotic stress, which is imposed on plants by non-living factors such as salinity, sunlight, temperature, cold, floods and drought having negative impact on crop plants. It is the climate in which the crop lives that decides what type of biotic stress may be imposed on crop plants and also the ability of the crop species to resist that particular type of stress. Many biotic stresses affect photosynthesis, as chewing insects reduce leaf area and virus infections reduce the rate of photosynthesis per leaf area.

What are the environmental stresses that affect plants?

Plants are subjected to a wide range of environmental stresses which reduces and limits the productivity of agricultural crops. Two types of environmental stresses are encountered to plants which can be categorized as (1) Abiotic stress and (2) Biotic stress. The abiotic stress causes the loss of major crop plants worldwide and includes radiation, salinity, floods, drought, extremes in temperature, heavy metals, etc. On the other hand, attacks by various pathogens such as fungi, bacteria, oomycetes, nematodes and herbivores are included in biotic stresses. As plants are sessile in nature, they have no choice to escape from these environmental cues. Plants have developed various mechanisms in order to overcome these threats of biotic and abiotic stresses. They sense the external stress environment, get stimulated and then generate appropriate cellular responses. They do this by stimuli received from the sensors located on the cell surface or cytoplasm and transferred to the transcriptional machinery situated in the nucleus, with the help of various signal transduction pathways. This leads to differential transcriptional changes making the plant tolerant against the stress. The signaling pathways act as a connecting link and play an important role between sensing the stress environment and generating an appropriate biochemical and physiological response.

Why are plants immobile?

Plants being immobile in nature have to go through continuous fluctuations in the environment with appropriate physiological, developmental and biochemical changes [ 4 ]. More than 50% reduction in crop plants occur due to abiotic stresses worldwide which is the main cause of crop loss [ 5 ]. To counteract the stresses, plants are equipped with a large set of defense mechanisms [ 6 ]. Among the different classes of compatible solutes, polyamines stand as one of the most effective against extreme environmental stress. Polyamines are low molecular weight aliphatic nitrogen compounds positively charged at physiological pH [ 7 ]. Investigations into plant polyamines at a molecular level have led to isolation of a number of genes encoding polyamine biosynthetic enzymes from a variety of plant species [ 8 ]. In recent years, molecular and genomic studies with mutants and transgenic plants having no or altered activity of enzymes involved in the biosynthesis of polyamines have contributed to a better understanding of biological functions of polyamines in plants.

Overview

In plants

Examples

Effects

In animals

In endangered species

See also