What is the plant response to heat stress?
High temperature is a major abiotic stress that limits the growth and production of plants. Therefore, the plant response to heat stress (HS) has been a focus of research. However, the plant response to HS involves complex physiological traits and molecular or gene networks that are not fully understood.
How do plants cope with adverse temperature conditions?
The elucidation of mechanisms by which temperature stress causes disorders is important to reveal responses by which plants cope with adverse temperature conditions. However, plants respond to temperature stress by regulating membrane lipid composition, stress-related transcription factors, metabolite synthesis and detoxification pathways.
How to develop plant tolerance to temperature stress?
The management of plant nutrients is very helpful to develop plant tolerance to temperature stress. Better plant nutrition can effectively alleviate the adverse effects of temperature stress by numerous mechanisms. Application of nutrients such as N, Ca, Mg, B, K, and Se reduced the ROS by enhancing the antioxidant system.
How does temperature affect plant growth?
The effect of temperature on plants vary widely, and is influenced by factors such as exposure to sunlight, moisture drainage, elevation, difference between day and night temperatures, and proximity to surrounding rock structure (thermal heat mass). Does Temperature Affect Seed Growth?
What does temperature stress mean?
Temperature stress, either fever or hypothermia, is associated with nitrogen loss, increased adrenal activity, and increased protein turnover. These stresses cause a decrease in total serum protein and albumin, but they often cause an increase in α2-globulin associated with the acute phase response.
How do plants cope with temperature stress?
Plants respond to heat stress by activating heat shock factors and also other molecular players. In particular, hormones as chemical messengers are involved. Among the hormones that plants produce are the brassinosteroids, which primarily regulate their growth and developments.
What is heat stress in biology?
Heat stress is often defined as the rise in temperature beyond a threshold level for a period of time sufficient to cause irreversible damage to plant growth and development. In general, a transient elevation in temperature, usually 10–15 °C above ambient, is considered heat shock or heat stress.
What is plant stress definition?
Any unfavorable condition or substance that affects or blocks a plant's metabolism, growth, or development is regarded as stress. Vegetation stress can be induced by various natural and anthropogenic stress factors.
What is low temperature stress in plants?
Generally, plants encounter two forms of low-temperature stress i.e., chilling and freezing. For plants, chilling temperatures are low but positive temperatures (0–15 °C) that could vary with the plant's tolerance level and variety.
What happens to plants at high temperature?
If extreme heat continues for weeks at a time, plants can actually die from a depletion of their food reserves. Finally, high temperatures may simply cause severe water loss (desiccation) when transpiration (the process by which leaves release water vapor to the atmosphere) exceeds moisture absorption by the roots.
What factors affect temperature stresses?
Factors that contribute to heat stress are high air temperatures, radiant heat sources, high humidity, direct physical contact with hot objects, and strenuous physical activities.
What temperature can cause heat stress?
Heatstroke is a condition caused by your body overheating, usually as a result of prolonged exposure to or physical exertion in high temperatures. This most serious form of heat injury, heatstroke, can occur if your body temperature rises to 104 F (40 C) or higher. The condition is most common in the summer months.
Why do plants have high heat stress?
Studies have shown that high temperatures can increase the plant's rate of reproductive development, which shortens the time for photosynthesis to contribute to fruit or seed production. Heat stress problems also make the plant more susceptible to pests and other environmental problems.
What are types of plant stress?
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].
What is plant stress and types of stress?
That environment can host two stressors: physical and chemical stress. Physical Plant Stress: The stress imposed by the physical environment. Such as drought (water stress), flood (waterlogging), salinity (toxicity), temperatures, winds, and soil compaction.
What types of stress are there?
Stress factors broadly fall into four types or categories: physical stress, psychological stress, psychosocial stress, and psychospiritual stress.
How do plants adapt to temperature?
Background: Plants adapt to seasonal and yearly fluctuations in ambient temperature by altering multiple aspects of their development, such as growth and the time to initiate flowering. These modifications in plant development depending on temperature are known as thermal developmental plasticity.
How do plants survive heat damage?
Leaf rolling and cupping Corn and tomatoes are among many plants that commonly roll their leaves or cup in response to heat. Leaf surface area is minimized, and stomata (microscopic openings in leaves, like pores, that allow movement of moisture and gasses) close. Together, these reduce moisture loss in the plant.
How long does it take plants to recover from heat stress?
You can cut back the plant to remove the damaged parts and fertilize. Even if you prune it back hard, it should grow back better than ever and bloom in about 6 weeks or so.
How do you keep plants alive in extreme heat?
Summer Plant Care: 8 Tips to Survive a Heat WavePromote high humidity. ... Water well, and water deeply. ... Shade sensitive plants from too much sun. ... Keep it cool. ... Don't fertilize during a heat wave. ... Don't re-pot during a heat wave. ... Wait to prune. ... Learn to recognize stress.
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Abstract
Temperature stress in plants is classified into three types depending on the stressor, which may be high, chilling or freezing temperature. Temperature-stressed plants show low germination rates, growth retardation, reduced photosynthesis, and often die.
Key Concepts
Plants cope with adverse temperature stress by altering molecular mechanisms involving proteins, antioxidants, metabolites, regulatory factors, other protectants and membrane lipids.
Other versions of this article
Please review our Terms and Conditions of Use and check box below to share full-text version of article.
Abstract
Temperature stress in plants is classified into three types depending on the stressor, which may be high, chilling or freezing temperature. Temperature-stressed plants show low germination rates, growth retardation, reduced photosynthesis, and often die.
Key Concepts
Plants cope with adverse temperature stress by altering molecular mechanisms involving proteins, antioxidants, metabolites, regulatory factors, other protectants and membrane lipids.
What are the three classes of HSFs?
Plant HSFs are divided into three conserved evolutionary classes (A, B, and C) according to the structural features of their oligomerization domains. Class A HSFs are essential for transcriptional activation. However, Class B and C HSFs have no activator function because they lack the appropriate motif comprising acidic amino acid residues [22]. Among class A HSFs, HSFA1 is the master transcriptional activator, triggering the immediate expression of other HS-responsive transcription factors (TFs) [20], including DEHYDRATION-RESPONSIVE ELEMENT BINDING PROTEIN 2A (DREB2A), HSFA2, HSFA7, HSFBs, and MULTIPROTEIN-BRIDGING FACTOR 1C (MBF1C) (Figure 2). HSFA1 transactivation activity is induced by interaction with HEAT SHOCK PROTEIN 70 (HSP70) and HSP90 under HS [23]. Interestingly, both HSFA1a and HSFA1b are important for the initial phase of HS-responsive gene expression [24]. HSFA2, as a heat-inducible transactivator, prolongs acquired thermotolerance by maintaining the expression of HSPgenes in Arabidopsis[25]. HSFA3 is regulated by DREB2A and DREB2C, playing a role in thermotolerance [20,26]. DREB2A, a key transcription factor, directly regulates HSFA3 transcription via a coactivator complex of NUCLEAR FACTOR Y, SUBUNIT A2 (NF-YA2), NF-YB3, and DNA POLYMERASE II SUBUNIT B3-1 (DPB3-1)/NF-YC10 under HS (Figure 2). In addition, HSFA4a and HSFA8 act as sensors of the ROS produced as secondary stress responses during the HS response in Arabidopsis[27].
What is the role of HSPs in plants?
The HSFsrapidly induce the expression of HSPs, and both HSFsand HSPsplay central roles in the plant HS response and induction of thermotolerance [20,21]. However, overexpression of a single HSFor HSPgene has little impact on thermotolerance, suggesting that HSFsand HSPsact synergistically to confer HS resistance.
What transcription factors are involved in plant thermotolerance?
The bZIP transcription factors and the unfolded protein response (UPR) play important roles in plant thermotolerance. bZIP28 and bZIP60, which localize to the endoplasmic reticulum (ER) membrane, are transferred to the nucleus, where they activate the expression of stress-responsive genes [42]. Under HS, the ER membrane-localized RNA splicing factor IRE1 (INOSITOL-REQUIRING ENZYME 1) splices the mRNA of bZIP60, causing synthesis of a spliced bZIP60 (sbZIP60), which translocates into the nucleus [28]. The ER-localized chaperone BiP (BINDING PROTEIN) binds to bZIP28 and inhibits its activation under non-stress conditions. The coordination of bZIP28 and HSFA2 is involved in regulation of the HS response in Arabidopsis. bZIP28-deficient plants showed enhanced activation of cytosolic APX-, MBF1c-, HSP-dependent pathways, and had elevated HSFA2 transcript levels, suggesting these pathways compensate for the deficiency in bZIP28 during HS [43]. The activation of bZIP17 is controlled by HS in a manner similar to the regulatory mechanism that controls the UPR. In lily (Lilium longiflorum), promotion of thermotolerance by LlHSFAs involves regulation of bZip factors (AtbZIP11, AtbZIP44) [44]. In addition, the response pathway of bZIPs is activated during prolonged warming [19].
How do plants acquire thermotolerance?
Notably, a minimal yet significant level of acquired thermotolerance can be attained in plants by induction of the expression of a small number of genes regulated by other transcription factors such as WRKY, bZIP, and MYB. WRKYs participate in developmental and physiological processes, as well as in stress responses. Under HS, WRKY18, WRKY25, WRKY26, WRKY33, WRKY39, WRKY40, WRKY46, and WRKY68 coordinately induce plant thermotolerance by positively regulating HSP-related signaling pathways (e.g., HSFs, HSPs, and MBF1c) [39,40]. In addition, OsWRKY11 in rice plays a role in the HS response and tolerance. Overexpression of OsWRKY11 under the control of the HSP101 promoter led to enhanced heat tolerance [41].
What are the effects of HS on plants?
Plants exposed to HS show accumulation of ROS—singlet oxygen (1O2), superoxide radical (O2−), hydrogen peroxide (H2O2), and hydroxyl radical (OH−)—generating oxidative stress [14]. The ROS are generated mainly in PSI and PSII. In PSII, excess energy generates the triplet state of chlorophylls, which pass excitation energy to O2, producing singlet oxygen. Over-reduction of PSI leads to generation of the superoxide anion, promoting H2O2production [8]. ROS (e.g., O2−, H2O2) induce oxidative stress by altering membrane properties, degrading proteins, and inactivating enzymes, thus reducing plant cell viability [15]. Heat stress induces lipid peroxidation due to free radical damage of the cell membrane [6]. Under HS, the content of malondialdehyde (MAD; an indicator of lipid peroxidation) is significantly increased in many plants such as sorghum [16]. ROS can also trigger programmed cell death under HS. On the other hand, plants have developed mechanisms to detoxify ROS and enhance heat tolerance. Plants increase their thermotolerance by recruiting the antioxidant enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR), and peroxidase (POX) [17].
What are the physiological consequences of plant exposure to HS?
Membrane dysfunction is the main physiological consequence of plant exposure to HS. Under extreme HS, the increased kinetic energy and movement of biomolecules across membranes loosens chemical bonds, leading to disintegration of membrane lipids and increasing membrane fluidity [12]. HS increases cellular membrane permeability and the loss of cellular electrolytes, consequently inhibiting cellular function and decreasing thermotolerance [5]. In addition, the reactive oxygen species (ROS) accumulation caused by HS leads to membrane damage, decreasing thermotolerance [13]. In short, membrane thermostability plays an important role in conferring tolerance to HS in plants.
How does epigenetic memory affect plants?
Epigenetic memory improves plant adaptation to various stress environments [61,91,92]. Histone modification and HSFA2 are important for HS memory in A. thaliana. The level of H3K4 methylation (H3K4me2/3), which is associated with transcriptional memory, was higher for at least 2 days after a priming heat shock [93]. Accumulation of H3K4 methylation is important for HSRexpression and transcriptional HS memory, and this modification depends on HSFA2 (Figure 4). HSFA2 and H3K27me3 demethylase RELATIVE OF EARLY FLOWERING 6 (REF6) display a positive feedback loop to transmit long-term epigenetic memory in A. thaliana(Figure 4) [94]. In wheat, the level of lysine-specific histone demethylase 1 (LSD1) was upregulated in the progeny of heat-primed plants compared to that of non-heat primed plants, implicating histone modification in the induction of transgenerational thermo-tolerance by heat priming. HS-induced transgenerational epigenetic memory or phenotypic changes can be maintained for at least three generations [95,96]. In addition, the ONSEN retrotransposon, as mentioned above, is transcriptionally activated in plants exposed to HS. Interestingly, ONSEN transposition occurs more frequently in the progeny of RdDM mutants subjected to HS (Figure 4), indicating that RdDM-mediated epigenetic modification prevents transgenerational propagation of retrotransposons in plants [55,97].
What is the effect of heat stress on plants?
Heat stress leads to excessive production of ethylene (ET), which promotes male sterility in plants, and also constrains the important enzymes that are involved in starch metabolism, further which deteriorates the grain filling pattern of plants limiting the rate of grain filling and ultimately produces sterile grain.
What enzymes are affected by high temperature?
High-temperature stress moderates the activity of various enzymes, such as sucrose phosphate synthase, adenosine di-phosphate (ADP)-glucose pyrophosphorylase, and invertase, which ultimately inhibits the synthesis of starch and sucrose ( Djanaguiraman et al., 2009 ).
What is the disease of Phaseolus vulgaris?
Phaseolus vulgaris. Green bean. Damages at early stages of development and reduced growth rate and reduction in yield. But in chilling stress, plants show symptom such as desiccation of foliage, necrosis, spot on leaves, fruits, and at extreme condition death of a part of plant.
What is temperature hassle?
Temperature hassle is generally demarcated as the intensification in the temperature beyond a verge level, which causes irrevocable damages to plant growth and development . Elevated temperature usually above 30°C considered being heat stress; it is a complicated function encompassing the duration of exposure, intensity, and frequency of rise in temperature ( Fig. 2.1 ).
How does temperature affect plants?
Plants in their life cycle face adverse environmental factors, including biotic and abiotic. Among these, temperature stress (low and high) is an important factor that directly or indirectly influences the growth and development of plants. Temperature stress affects the plant at different levels, such as at morphological, biochemical, and molecular, and degree of toxicity is different in plants facing low and high temperature. High temperature enhances the denaturation of enzymes and proteins and also denatures the DNA structure at molecular level and loss of membrane integrity. On the other hand, low temperature particularly affects the reproductive fitness of plants, ovule abortion, and reduced fruit set. Due to these adverse impacts, it is necessary to increase the protective mechanism against temperature stress. Plants develop several strategies at morphological, biochemical, and molecular levels to cope up with temperature stress. At morphological level, avoidance and tolerance mechanism is adopted. ROS generation is a common phenomenon by temperatures stress. To mitigate ROS-induced damage, every plant having an array of antioxidant machinery includes enzymatic (SOD, POD, CAT, and GST) antioxidants. Besides, HSP is common protein that is involved in heat stress tolerance, including HSP 60 and 90. The management of plant nutrients is very helpful to develop plant tolerance to temperature stress. Better plant nutrition can effectively alleviate the adverse effects of temperature stress by numerous mechanisms. Application of nutrients such as N, Ca, Mg, B, K, and Se reduced the ROS by enhancing the antioxidant system. Nutrient management significantly enhances the crop productivity for the betterment of human welfare.
What are the environmental factors that affect plants?
First one is biotic factors that include pathogen and herbivore attacks, and second is abiotic factors that include drought, heat, cold, nutrient deficiency, and heavy-metal accumulation in the soil. Among these, salt, drought, and temperature affect the geographical distribution of plant species and disrupt the plant metabolism ( Bolton, 2009 ). As a consequence, they limit the quality and quantity of food production in agriculture, reducing the food supply for growing population ( Fedoroff et al., 2010 ), and to overcome these adverse effects tolerance mechanism in plants have been well studied ( Abuqamar et al., 2009, Mengiste et al., 2003, Suzuki et al., 2005 ). In general, various environmental factors (biotic and abiotic) induce the plant resistance by activation of stress tolerance genes. The average temperature was found to be increased by 0.2°C/year and it has to be increased by 1.8°C–4°C at the end of year 2100, hence temperature is pondered to be one of the utmost detrimental stress ( Hasanuzzaman et al., 2013 ). Climate change due to temperature is a global concern that has altered the physiological and biochemical activities of plant, thereby reducing the productivity of crops ( Hasanuzzaman et al., 2012, Hasanuzzaman et al., 2013 ). Increased temperature continuously caused heat stress in plants, which depends upon the quality, intensity, and duration of light. Generation of reactive oxygen species (ROS) is a common phenomenon exhibited by all environmental factors (biotic and abiotic), including heat stress that damaged the macromolecules, such as DNA, proteins, and lipids ( Singh et al., 2016 ), and plants are under oxidative stress. Furthermore, heat stress also altered the expression of genes that participate in the formation of responsible for the production of osmoprotectants, detoxifying enzymes, transporters, and regulatory proteins ( Semenov, 2009, Krasensky and Jonak, 2012 ). On contrary to this, heat stress inhibits the protein folding, affects the membrane (lipid bilayer) fluidity and cytoskeleton arrangement, and also affects the vegetative and reproductive tissue ( Ruelland et al., 2009, Zinn et al., 2010 ). Rise in temperature up to a certain limit is beneficial for plant, which regulates the circadian rhythms in plants, regulates plant movements (opening/closing of corolla) ( Van Doorn and Van Meeteren, 2003, Thines and Harmon, 2010 ), and also affects the geographical distribution of plants in nature. Plants susceptibility toward pathogen was also enhanced by high temperature. Infection capacity of tobacco mosaic and tomato-spotted wilt viruses was found to be increased when ambient temperature increased and cause viral diseases in tobacco ( Nicotiana tabacum) and pepper ( Capsicum annuum ), respectively ( Király et al., 2008, Moury et al., 1998 ). In wheat genotypes, its sensitivity toward Cochliobolus sativus (caused spot blotch) was increased associated with increase in nighttime temperature ( Sharma et al., 2007 ).
How do plants tolerate temperature stress?
Plants tolerate temperature stress by modulating genes and also regulate the gene expression involve in activation HSPs ( Vinocur and Altman, 2005 ). Majority of stress tolerance proteins are soluble in water and among them, HSPs are exclusively concerned in heat-stress response.
What transcriptional factors regulate flavonol biosynthesis?
Transcriptional factors MYB11, MYB12, and MYB111 control flavonol biosynthesis via activating upstream EBGs. 57 Consequently, MYB 75, MYB 90, MYB 113, and MYB 114 regulate the anthocyanin biosynthesis genes ( DFR and LDOX ), categorized under late biosynthetic genes (LBGs) ( Fig. 13.4 ). 58 These MYB transcriptional factors that regulate the biosynthesis of flavonols, and subsequently anthocyanins, are in turn controlled by redox potential. 12 Redox control is crucial in the regulation of MYB proteins as any abnormalities can influence the DNA binding property of these transcription factors. Several lines of evidence showed that MYB proteins participate in the cross-talk between different signaling pathways under stress conditions for imparting cross-tolerance. Recently, evidence showed that overexpressing an R2R3-MYB gene, regulating anthocyanin biosynthesis, leads to enhanced cross-tolerance against chilling and oxidative stress. 59 Moreover, AtMYB15 is also reported to be involved in cold stress tolerance. 60 The phytohormone ABA is a positive indicator of drought stress, and several MYB, such as AtMYB60 and AtMYB96, in A. thaliana link with ABA signaling cascade for regulating stomatal movement, and thus contribute to drought tolerance 61 and disease resistance. 62 A study of R2R3 TF in oilseed crop, canola, reveals that a member of MYB TF family, BnaMYB78, which mediates cell necrosis, modulates the expression of ROS dependent defense-related genes such as HIN1, RbohB, and GST. 63
Why do plants accumulate proline?
In plants, proline accumulation has been reported to occur due to salt, drought, high temperature, low temperature, heavy metal, pathogen infection, anaerobiosis, nutrient deficiency, atmospheric pollution, and UV irradiation ( Hare and Cress, 1997; Siripornadulsil et al., 2002 ). The level of proline accumulation in plants varies from species to species and can be 100 times greater than in a control situation. Osmotic stress, which includes treatments lowering the osmotic potential component of the water potential, are by far the most studied because they represent a major concern in agriculture. Proline accumulation is believed to play adaptive roles in plant stress tolerance. Proline has been proposed to act as a compatible osmolyte and to be a method for storing carbon and nitrogen ( Hare and Cress, 1997 ). Salinity and drought are known to induce oxidative stress. In vitro studies showed that proline can be a ROSs scavenger ( Smirnoff and Cumbes, 1989 ). Proline has also been proposed to function as a molecular chaperone stabilizing the structure of proteins, and proline accumulation can provide a way to buffer cytosolic pH and balance the cell redox status. Finally, proline accumulation may be part of the stress signal influencing adaptive responses ( Maggio et al., 2002 ). Proline accumulation during osmotic stress is mainly due to increased synthesis and reduced degradation. Although proline transport certainly plays an important role in proline distribution, its role during stress has been poorly studied ( Rentsch et al., 1996 ).
How do plants maintain metabolic activities?
Under drought stress, plants maintain metabolic activities through drought avoidance or dehydration tolerance mechanisms. Drought avoidance is a physiological process in which plant cells maintain high water potential and increase WUE. This can be done using various processes such as reducing transpiration, extracting more water from the roots, increasing root growth, and limiting vegetative growth ( Kooyers, 2015 ). Dehydration tolerance is a mechanism of maintaining high tolerance to desiccation by OA and cell membrane stability (CMS). CMS is the ability of cell membrane to restrict water stress damage and to regain integrity and membrane bound actions promptly upon rehydration. It can be measured by checking electrolyte leakage from a segment of leaf ( Bajji et al., 2002 ).
What happens to plants during drought?
During drought stress, plants fail to keep the balance of ROS in their cells and fulfill the antioxidant requirement in plant cells ( Hossain et al., 2012 ). This leads to extreme damages of proteins, lipids, and nucleic acid molecules present in plant cells ( Rinalducci et al., 2008 ). To counter this stress, plants have very well-developed defense system that involves both enzymatic and nonenzymatic mechanisms ( Hossain et al., 2010 ). The cellular system aids these mechanisms by sending different stress signals to cell organelles ( Desikan et al., 2001 ). As the stress signals reach cell surfaces, they produce their response at the outer surface first and then activate the responsive mechanism inside of plants ( Huang et al., 2012 ). Actually the presence of ROS is the stress signal that activates plant cell–defensive mechanism is the primary stress response of plants ( Agrawal et al., 2011 ). Moreover, proteins receptors are also present in the cell membrane, which immediately respond to stress signals ( Komatsu et al., 2007 ).
How do plants respond to temperature?
Under temperature stress, plants evolve two types of responses, one is long-term response that falls under (evolutionary, phonological, and morphological adaptations) and the other is short-term (avoidance or acclimation) response. Plants exhibited several physiological changes including alteration in leaf orientation, change in composition of membrane lipids, or increase the transpirational cooling. Leaves of plants are very labile to temperature, and under stress condition, leaves closed the stomata, increased the stomatal, trichomatous densities, and in vascular bundle, xylem vessels become larger to avoid heat stress ( Srivastava et al., 2012 ). Plants under extreme high-temperature environment avoid excess temperature by reducing the absorption of solar radiation by the presence of thick cuticle having small hairs (tomentose) and waxy covering. Leaf orientation also changed under changing temperature of environment as leaf blades turn away from light and change their orientation by rolling in such a way that they seem to be parallel with falling sun rays ( Hasanuzzaman et al., 2013 ). In general, temperature tolerant species having small-sized leaves than temperature sensitive species and avoid heat stress. The increasing rate of transpiration is also a strategy of plants to maintain basal temperature, and it protects leaves from heat stress and temperature that is around 6°C lower than outside temperature ( Fitter and Hay, 2002 ). Plant life cycle also modified in response to temperature as leaf abscission, dessert annuals and increasing the heat resistant buds, and completes their reproductive phase in cooler months to avoid heat stress ( Fitter and Hay, 2002 ). Sarieva et al. (2010) studied that under heat stress condition, wheat leaves show a significant increase in water metabolism. Although all plants in their early life cycle are sensitive to temperature, resistance toward high temperature develops in summer environment and the highest level of tolerance during winter dormancy. To avoid damage due to temperature stress, proper sowing methods play very important role, such as choice of sowing date, cultivars, and irrigation methods. Further, lettuce plant seeds when grown in summer show improper germination and shows proper germination by sowing the lettuce seed into dry beds during the day and then sprinkle irrigating the beds during the late afternoon. To avoid improper germinations, seeds of different plants are kept in osmotic solution to provide constant temperature for several days. Furthermore, tolerance strategy was also an adaptive response against temperature stress, which includes production of osmoprotectants, late embryogenesis abundant proteins, increase in ion transporters, and involvement of antioxidant defense system ( Rodríguez et al., 2005; Wang et al., 2004 ). In response to the applied stress types, different plant parts show variation in developmental complexity ( Queitsch et al., 2000 ). Changes in membrane fluidity under temperature stress reestablish homeostasis and to protect and repair damaged proteins and membranes ( Vinocur and Altman, 2005) ( Fig. 2.2 ).
Why do plants need high energy levels?
Findings of different authors suggest that plants need high-energy levels to fuel defense mechanisms of plants under Cd stress.
How does stress affect plants?
83 They have been recognized as important adaptation strategies and as a mechanistic basis for stress memory, enabling plants to respond faster and more efficiently to recurring stress or even to prepare their offspring for potential future climate changes. 84 In recent years, scientists have developed approaches and tools for estimating and quantifying epigenetic variations with respect to their impacts on plant responses to environmental stresses. 85 DNA methylation and alterations in chromatin dynamics can be induced by drought or temperature treatments and these changes at the level of drought-inducible genes are associated with altered expression of transcriptional responses. 86 Trimethylation of histone H3 at the position of lysine 4 (H3K4me3) is a prominent histone mark known to be connected with promoters and early-transcribed regions of active genes, and functions in promoting gene transcription. 87 Changes in H3K4me3 in response to preexposure to drought have been reported for delaying dehydrin-induced gene expression. 88 Furthermore, some epigenetic processes are controlled by fluxes of certain hormones, such as ABA, which are in turn influenced by drought and heat stress, resulting in plant adaptation. 89,90 However, no research has been conducted regarding epigenetic changes related to drought priming-enhanced heat tolerance, in efforts to decipher how epigenetic machinery responds to environmental stresses so that epigenetic modifications may be used in breeding new crop cultivars that are more resilient to a future changing climate. 85
