Plant Responses and Tolerance to High Temperature Stress: Role of Exogenous Phytoprotectants

SUMMARYHigh temperature stress at flowering can adversely affect rice yield, largely due to failure of fertilization. Oxidative damage can be a major reason inducing spikelet sterility in rice. In the present study, the effect of high temperatures on antioxidant metabolism in rice spikelets was characterised using nine different genotypes. Exposure to different temperatures at flowering stage revealed significant differences among various antioxidant enzymes in spikelets, both quantitatively and qualitatively. Spikelets of susceptible genotypes withstood temperature stress of up to 35 °C, those of moderately tolerant between 35 °C and 38 °C and those of tolerant genotypes up to 40 °C. Presence or absence, and changes in the isozyme intensities were consistent with alterations in their activities. Superoxide dismutase (SOD) isozymes II and III were present after exposure at 30 °C and 35 °C, while SOD I appeared above 40°C. Intensities of catalase isozymes I and III and the only isozyme of ascorbate peroxidase altered, while the only isozyme of guaical peroxidase and two (III and IV) of the four isozymes of catechol peroxidase disappeared after high temperature exposure of 45 °C. Thus, this work provides an evidence of the role of antioxidant metabolism in spikelets under high temperature stress conditions. Hence, changes in antioxidant isozymes in rice spikelets can be used as a biomarker for characterizing high temperature stress tolerance in rice spikelets.

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Physiological and Transcriptomic Analyses Reveal Exogenous Trehalose Is Involved in the Responses of Wheat Roots to High Temperature Stress

Plants ◽

10.3390/plants10122644 ◽

2021 ◽

Vol 10 (12) ◽

pp. 2644

Author(s):

Yin Luo ◽

Yanyang Xie ◽

Weiqiang Li ◽

Maohuan Wei ◽

Tian Dai ◽

...

Keyword(s):

Gene Expression ◽

High Temperature ◽

Temperature Stress ◽

Gene Expression Regulation ◽

High Temperature Stress ◽

Physiological Data ◽

Glutathione Metabolism ◽

Plant Responses ◽

Wheat Roots ◽

Wheat Varieties

High temperature stress seriously limits the yield and quality of wheat. Trehalose, a non-reducing disaccharide, has been shown involved in regulating plant responses to a variety of environmental stresses. This study aimed to explore the molecular regulatory network of exogenous trehalose to improve wheat heat tolerance through RNA-sequencing technology and physiological determination. The physiological data and RNA-seq showed that trehalose reduced malondialdehyde content and relative conductivity in wheat roots, and affecting the phenylpropane biosynthesis, starch and sucrose metabolism, glutathione metabolism, and other pathways. Our results showed that exogenous trehalose alleviates the oxidative damage caused by high temperature, coordinating the effect of wheat on heat stress by re-encoding the overall gene expression, but two wheat varieties showed different responses to high temperature stress after trehalose pretreatment. This study preliminarily revealed the effect of trehalose on gene expression regulation of wheat roots under high temperature stress, which provided a reference for the study of trehalose.

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Effect of High-Temperature Stress on Plant Physiological Traits and Mycorrhizal Symbiosis in Maize Plants

Journal of Fungi ◽

10.3390/jof7100867 ◽

2021 ◽

Vol 7 (10) ◽

pp. 867

Author(s):

Sonal Mathur ◽

Richa Agnihotri ◽

Mahaveer P. Sharma ◽

Vangimalla R. Reddy ◽

Anjana Jajoo

Keyword(s):

High Temperature ◽

Temperature Stress ◽

Soil Microbial Communities ◽

High Temperature Stress ◽

Protective Role ◽

Physiological Parameters ◽

Ps Ii ◽

Below Ground ◽

Maize Plants

Increasing high temperature (HT) has a deleterious effect on plant growth. Earlier works reported the protective role of arbuscular mycorrhizal fungi (AMF) under stress conditions, particularly influencing the physiological parameters. However, the protective role of AMF under high-temperature stress examining physiological parameters with characteristic phospholipid fatty acids (PLFA) of soil microbial communities including AMF has not been studied. This work aims to study how high-temperature stress affects photosynthetic and below-ground traits in maize plants with and without AMF. Photosynthetic parameters like quantum yield of photosystem (PS) II, PSI, electron transport, and fractions of open reaction centers decreased in HT exposed plants, but recovered in AMF + HT plants. AMF + HT plants had significantly higher AM-signature 16:1ω5cis neutral lipid fatty acid (NLFA), spore density in soil, and root colonization with lower lipid peroxidation than non-mycorrhizal HT plants. As a result, enriched plants had more active living biomass, which improved photosynthetic efficiency when exposed to heat. This study provides an understanding of how AM-mediated plants can tolerate high temperatures while maintaining the stability of their photosynthetic apparatus. This is the first study to combine above- and below-ground traits, which could lead to a new understanding of plant and rhizosphere stress.

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Regulation of Osmotic Balance and Increased Antioxidant Activities under Heat Stress in Abelmoschus esculentus L. Triggered by Exogenous Proline Application

Agronomy ◽

10.3390/agronomy11040685 ◽

2021 ◽

Vol 11 (4) ◽

pp. 685

Author(s):

Rashid Hussain ◽

Choudhary Muhammad Ayyub ◽

Muhammad Rashid Shaheen ◽

Sahar Rashid ◽

Muhammad Nafees ◽

...

Keyword(s):

Heat Stress ◽

High Temperature ◽

Water Use Efficiency ◽

Temperature Stress ◽

Water Use ◽

Antioxidant Activities ◽

High Temperature Stress ◽

Plant Responses ◽

Randomized Design ◽

Use Efficiency

Keeping in view the yield losses instigated by heat stress in several crops, we carried out an experiment to explore the curative effect of exogenous applications of proline on the morpho-physiological, biochemical, and water-related attributes of okra genotypes under high-temperature stress (controlled conditions). Four contrasting genotypes C1, C2, C3, and C4 heat tolerant and heat sensitive genotypes were selected from a diverse panel of okra genotypes (n = 100) to examine plant responses to high-temperature stress and exogenous application of proline. Four-week-old seedlings were subjected to heat stress by gradually increasing the temperature of a growth chamber from 28/22 °C to 45/35 °C (day/night) and sprayed with an optimized proline concentration 2.5 mM. The experiment consisted of a factorial arrangement of treatments in a completely randomized design. The results showed that there were maximum increases in shoot length (32.7%), root length (58.9%), and shoot fresh (85.7%). The quantities of leaves per plant were increased by 52.9%, 123.6%, 82.5%, and 62.2% in C1, C2, C3, and C4 after proline application. On the other hand, only root fresh weight decreased in all genotypes after proline application by 23.1%, 20%, 266.7%, and 280.8% (C1, C2, C3, C4). A lower leaf temperature of 27.72 °C, minimum transpiration of 3.29 mmol m−2 s−1, maximum photosynthesis of 3.91 μmol m−2 s−1, and a maximum water use efficiency of 1.20 μmol CO2 mmol H2O were recorded in the genotypes C2, C1, C3, and C4, respectively. The highest enzymatic activity of superoxide dismutase, peroxidase and catalase were 14.88, 0.31, and 0.15 U mg-protein in C2, C1, and C3, respectively. Maximum leaf proline, glycinebetaine, total free amino acids, and chlorophyll content 3.46 mg g−1, 4.02 mg g−1, 3.46 mg g−1, and 46.89 (in C2), respectively, due to foliar applications of proline. Another important finding was that heat tolerance in okra was highly linked highly linked to genotypes’ genetic potential, having more water use efficiency, enzymatic activities, and physio-biochemical attributes under the foliar applications of proline.

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WRKY Transcription Factor Response to High-Temperature Stress

Plants ◽

10.3390/plants10102211 ◽

2021 ◽

Vol 10 (10) ◽

pp. 2211

Author(s):

Zhuoya Cheng ◽

Yuting Luan ◽

Jiasong Meng ◽

Jing Sun ◽

Jun Tao ◽

...

Keyword(s):

High Temperature ◽

Plant Growth ◽

Signaling Pathways ◽

Temperature Stress ◽

Molecular Mechanisms ◽

Target Genes ◽

High Temperature Stress ◽

Research Progress ◽

Plant Responses ◽

Gene Promoters

Plant growth and development are closely related to the environment, and high-temperature stress is an important environmental factor that affects these processes. WRKY transcription factors (TFs) play important roles in plant responses to high-temperature stress. WRKY TFs can bind to the W-box cis-acting elements of target gene promoters, thereby regulating the expression of multiple types of target genes and participating in multiple signaling pathways in plants. A number of studies have shown the important biological functions and working mechanisms of WRKY TFs in plant responses to high temperature. However, there are few reviews that summarize the research progress on this topic. To fully understand the role of WRKY TFs in the response to high temperature, this paper reviews the structure and regulatory mechanism of WRKY TFs, as well as the related signaling pathways that regulate plant growth under high-temperature stress, which have been described in recent years, and this paper provides references for the further exploration of the molecular mechanisms underlying plant tolerance to high temperature.

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