The increased prevalence of high temperatures (HTs) around the world is a major global concern, as they dramatically affect agronomic productivity. Upon HT exposure, plants sense the temperature change and initiate cellular and metabolic responses that enable them to adapt to their new environmental conditions. Decoding the mechanisms by which plants cope with HT will facilitate the development of molecular markers to enable the production of plants with improved thermotolerance. In recent decades, genetic, physiological, molecular, and biochemical studies have revealed a number of vital cellular components and processes involved in thermoresponsive growth and the acquisition of thermotolerance in plants. This review summarizes the major mechanisms involved in plant HT responses, with a special focus on recent discoveries related to plant thermosensing, heat stress signaling, and HT-regulated gene expression networks that promote plant adaptation to elevated environmental temperatures.

以20个黄淮海区域主栽夏玉米品种为试验材料，采用大田试验，研究花期高温胁迫对不同夏玉米品种产量和品质的影响，并对夏玉米品种的耐热性进行评价,为黄淮海区域耐热夏玉米品种的推广应用提供理论依据。结果表明，高温胁迫可降低夏玉米品种百粒质量、穗行数和穗粒数，进而降低产量，其中，郑单958、隆平206、登海605、伟科702、郑单1002、郑单309、京科968、中科玉505的产量耐热系数较高，而浚单29、先玉335、蠡玉16、农华101、迪卡517、联创808、郑单343等品种的产量耐热系数较低。与对照（常温处理）相比，高温处理夏玉米品种总蛋白质含量平均增加4.27%，清蛋白、球蛋白、醇溶蛋白含量分别增加13.33%、10.53%、12.12%；总淀粉含量下降2.11%，其中支链淀粉含量下降了3.02%。其中，高温处理伟科702、郑单1002、郑单309、先玉335的总蛋白质含量较对照增加较多，分别增加了23.06%、19.77%、18.67%、18.58%，而浚单29、农大372、裕丰303较对照降低较多，分别降低了9.68%、10.25%、11.36%；秋乐218、新单68、中科玉505、裕丰303的总淀粉含量较对照降低较多，分别降低了5.60%、6.47%、5.13%、5.49%，而浚单29、伟科702、郑单1002分别较对照降低了0.28%、0.03%、0.34%。利用产量耐热系数进行聚类分析，将20个品种分为3类：耐热型、中间型和热敏感型，耐热型包括农大372、登海605、郑单1002、郑单309、京科968、中科玉505，中间型包括郑单958、隆平206、宇玉30、伟科702、新单68，热敏感型包括浚单29、先玉335、蠡玉16、联创808、农华101、迪卡517、秋乐218、裕丰303、郑单343。高温处理下，热敏感型品种的籽粒总蛋白质含量最高，但较对照变化幅度最小；不同类型品种淀粉含量相近，但以热敏感型品种较对照的变化幅度最大。

【目的】利用热感指数作为耐热性鉴定指标,分别对冬、春小麦种质资源进行高通量耐热性鉴定,筛选耐热种质资源,为小麦耐热性育种提供材料基础。【方法】冬小麦材料采用延期播种、春小麦材料种植在温度有显著差异的地理环境下,人为致使小麦灌浆期遭遇高温胁迫。根据不同环境处理的千粒重值计算冬、春小麦各个材料的热感指数。依据热感指数,对来自中国不同小麦生态区和国外不同地区和组织的1 325份小麦种质资源,包括688份冬小麦和637份春小麦,分别进行耐热性评价。热感指数小于0.5为极耐热材料、大于等于0.5小于1为中等耐热材料、大于等于1小于1.5为中等热敏感材料、大于等于1.5为极敏感材料。【结果】冬小麦和春小麦热胁迫处理组灌浆期平均最高温度分别高于对照组1.91℃和7.09℃,且热胁迫处理组千粒重与对照组相比均有显著降低。根据热感指数分级评价结果,极耐热冬、春小麦材料31和48份,占供试材料的4.51%和7.54%;极敏感冬、春小麦材料19和58份,占供试材料的2.76%和9.11%;其余大多数材料为中间类型（中等耐热材料和中等热敏感材料）。从中国小麦生态区域的地理分布来看,来自南部麦区（西南冬麦区、青藏春冬麦区、长江中下游冬麦区）的冬小麦材料耐热性整体高于来自北部麦区（北部冬麦区、黄淮冬麦区）的冬小麦材料。对于春小麦,来自新疆春冬麦区的材料耐热性最强,平均热感指数为0.70,且其中88.00%的材料属于耐热材料（极耐热材料或中等耐热材料）;此外,来自国际干旱地区农业研究中心的春小麦平均热感指数为0.88,也表现出较强的耐热性。来自CIMMYT的人工合成六倍体材料耐热性最弱,平均HSI为1.18,其中69.58%的材料为热敏感材料（中等热敏感材料和极敏感材料）。【结论】采用延期播种或在高温的地理环境下种植能使小麦在灌浆期遭遇高温胁迫。以千粒重热感指数作为评价指标,对1 325份小麦种质资源进行高通量耐热性鉴定,综合考虑正常条件下的产量潜力和高温条件下的耐热性,筛选出优异耐热资源103份,可用于相应生态区小麦的耐热性遗传改良。

本研究首次以盐生草（Halogeton glomeratus）为材料，模拟盐胁迫（100 mmol·L^-1 NaCl）环境，探讨不同浓度重金属Cu²⁺，Zn²⁺，Ni²⁺，Cd²⁺，Pb²⁺处理对其萌发特性的影响。结果表明：随处理浓度的升高，发芽率和发芽势均表现为先升高后下降趋势，表明低浓度重金属离子可促进植物的萌发，幼苗鲜重、干重、株高均呈现逐渐下降趋势。测定离子含量得出，Cd²⁺和Pb²⁺离子含量随着胁迫加重呈先升高后下降的趋势，Cu²⁺，Zn²⁺和Ni²⁺离子含量逐渐增加。测定根系活力发现，Cu²⁺，Zn²⁺根系活力随浓度的升高呈先上升后下降趋势，Ni²⁺，Cd²⁺，Pb²⁺根系活力逐渐降低。综合聚类及主成分分析得出：盐生草耐Cu²⁺，Zn²⁺，Ni²⁺，Cd²⁺，Pb²⁺的临界浓度分别为：1.00 mmol·L^-1，10.00 mmol·L^-1，0.30 mmol·L^-1，0.20 mmol·L^-1和0.50 mmol·L^-1，在胁迫浓度达临界值时贡献率最大的指标分别为：萌发指标、干重、发芽势、干重和发芽势。

Leaf extracts of both Nicotiana tabacum and Nicotiana sylvestris contain multiple forms of catalase (H(2)O(2):H(2)O(2) oxidoreductase, EC 1.11.1.6) which are separable at different pH values by chromatofocusing columns. Marked changes in distribution of these catalases occur during seedling development and leaf maturation. The form of catalase eluting first (peak 1) was predominant during early seedling growth and present at all stages of development. Two more acidic forms (peaks 2 and 3) appeared later and comprised 29% of the total activity by 11 days postgermination. Mature leaves of N. tabacum contained peak 1 catalase, but peaks 2 and 3 represented 62% of the total activity. No interconversion of peaks 1, 2, and 3 was detected. The three forms of catalase differed in thermal stability with peak 1 > peak 2 >> peak 3. For N. sylvestris, t((1/2)) at 55 degrees C was 31.5 and 3.0 min for peaks 1 and 3, respectively, and for N. tabacum, t((1/2)) was 41.5 and 3.2 min, respectively. All forms of catalase in tobacco show peroxidatic (measured as ethanol to acetaldehyde conversion) as well as catalatic activities. However, for both Nicotiana species the ratio peroxidatic/catalatic activity is at least 30-fold higher in peak 3 than in peaks 1 and 2. Chromatofocusing of extracts from spinach leaves separated at least four peaks of catalase activity, one of which had a 10-fold higher ratio of peroxidatic/catalatic activity than the others. Short-term growth (5 days) of tobacco seedlings under atmospheric conditions suppressing photorespiration (1% CO(2)/21% O(2)) reduced total catalase activity and caused a decline in peak 1 catalase and a substantial increase in the activity of peaks 2 and 3 relative to air-grown seedlings at the same stage.

Crop plants require an optimum range of temperature for normal growth and development however high temperature can adversely affect the plants, induce oxidative stress and disintegrate biomolecules especially DNA and proteins. In wheat, high temperature stress (35-40 °C) during ripening stage hampers the yield tremendously. In this study, we assessed high temperature (HT) induced oxidative stress, subsequent DNA damage and role of priming in stress tolerance by analyzing DNA repair enzyme Triticum aestivum AP endonuclease (TaApe1L). Sixteen days old seedlings of wheat varieties PBW 550 and PBW 343 were primed with mild drought and exposed to HT (38 °C) for 2, 4, and 6 h. Hydrogen peroxide (HO) was used as oxidative stress marker and quantified on regular time intervals. DNA damage was analyzed by DNA laddering and TaApe1L gene expression was analyzed using RT PCR and western blotting. Phylogenetic analysis of Ape1 revealed presence of some key amino acids that are evolutionary conserved. A significant increase in HO content was observed after 6 h of exposure especially in PBW 343. Similarly, the DNA damage was also increased with HT exposure especially in PBW 343. The TaApe1L mRNA expression increased after priming in both the varieties after 4 h. But APE1 protein expression was higher in PBW 343, which can be correlated with DNA damage and repair. Lastly, it can be concluded that there is varietal difference in the HT sensitivity but 6 h exposure was detrimental to both the varieties. Also, drought priming improved HT tolerance by over expressing APE1.Copyright © 2020 Elsevier Masson SAS. All rights reserved.

High temperature (HT) stress is a major environmental stress that limits plant growth, metabolism, and productivity worldwide. Plant growth and development involve numerous biochemical reactions that are sensitive to temperature. Plant responses to HT vary with the degree and duration of HT and the plant type. HT is now a major concern for crop production and approaches for sustaining high yields of crop plants under HT stress are important agricultural goals. Plants possess a number of adaptive, avoidance, or acclimation mechanisms to cope with HT situations. In addition, major tolerance mechanisms that employ ion transporters, proteins, osmoprotectants, antioxidants, and other factors involved in signaling cascades and transcriptional control are activated to offset stress-induced biochemical and physiological alterations. Plant survival under HT stress depends on the ability to perceive the HT stimulus, generate and transmit the signal, and initiate appropriate physiological and biochemical changes. HT-induced gene expression and metabolite synthesis also substantially improve tolerance. The physiological and biochemical responses to heat stress are active research areas, and the molecular approaches are being adopted for developing HT tolerance in plants. This article reviews the recent findings on responses, adaptation, and tolerance to HT at the cellular, organellar, and whole plant levels and describes various approaches being taken to enhance thermotolerance in plants.

The astonishing increase in temperature presents an alarming threat to crop production worldwide. As evident by huge yield decline in various crops, the escalating drastic impacts of heat stress (HS) are putting global food production as well as nutritional security at high risk. HS is a major abiotic stress that influences plant morphology, physiology, reproduction, and productivity worldwide. The physiological and molecular responses to HS are dynamic research areas, and molecular techniques are being adopted for producing heat tolerant crop plants. In this article, we reviewed recent findings, impacts, adoption, and tolerance at the cellular, organellar, and whole plant level and reported several approaches that are used to improve HS tolerance in crop plants. Omics approaches unravel various mechanisms underlying thermotolerance, which is imperative to understand the processes of molecular responses toward HS. Our review about physiological and molecular mechanisms may enlighten ways to develop thermo-tolerant cultivars and to produce crop plants that are agriculturally important in adverse climatic conditions.

Polycyclic aromatic compounds (PACs) are known due to their mutagenic activity. Among them, 2-nitrobenzanthrone (2-NBA) and 3-nitrobenzanthrone (3-NBA) are considered as two of the most potent mutagens found in atmospheric particles. In the present study 2-NBA, 3-NBA and selected PAHs and Nitro-PAHs were determined in fine particle samples (PM 2.5) collected in a bus station and an outdoor site. The fuel used by buses was a diesel-biodiesel (96:4) blend and light-duty vehicles run with any ethanol-to-gasoline proportion. The concentrations of 2-NBA and 3-NBA were, on average, under 14.8 µg g−1 and 4.39 µg g−1, respectively. In order to access the main sources and formation routes of these compounds, we performed ternary correlations and multivariate statistical analyses. The main sources for the studied compounds in the bus station were diesel/biodiesel exhaust followed by floor resuspension. In the coastal site, vehicular emission, photochemical formation and wood combustion were the main sources for 2-NBA and 3-NBA as well as the other PACs. Incremental lifetime cancer risk (ILCR) were calculated for both places, which presented low values, showing low cancer risk incidence although the ILCR values for the bus station were around 2.5 times higher than the ILCR from the coastal site.

为鉴定不同菜心品种的耐热性,以热害指数为评价指标对19份材料进行耐热性评价,并在此基础上研究了酶促抗氧化系统对人工模拟高温胁迫及恢复的响应。结果表明:通过热害指数分析,筛选出耐热品种5个、中等耐热品种11个、不耐热品种3个。对耐热品种CX10、中等耐热品种CX17和不耐热品种CX13进行人工模拟高温处理发现,37 ℃高温胁迫时菜心叶片的电导率、MDA含量显著升高,SOD、POD和CAT的活性,以及Mn-SOD、POD和CAT基因表达量显著增加。从增加幅度来看,耐热材料中的电导率、MDA含量增幅明显低于不耐热材料,SOD、POD和CAT的活性,以及Mn-SOD、POD和CAT基因表达量则以耐热材料中增幅最大。在胁迫恢复3 d时,与胁迫时相比,所有指标均呈下降趋势,但仍高于对照。以上结果说明,高温胁迫影响了菜心酶促抗氧化系统的正常代谢,即使高温解除后也不能恢复至正常状态,但耐热材料可通过调节自身的酶促系统减轻胁迫带来的伤害。

【目的】分析不同基因型小麦的耐热性,筛选耐热鉴定指标,建立可靠的耐热评价模型,为耐热小麦品种的选育提供理论支撑。【方法】以黄淮海麦区大面积推广的20个小麦品种为试验材料,采用田间试验,设置高温（花后第14—20天,连续7 d高温处理）和自然条件2种处理,在灌浆后期测定小麦穗部冠层温度、旗叶叶绿素相对含量（SPAD）、丙二醛（MDA）含量以及超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活性;收获晾干后测定单穗粒重、千粒重和产量。根据高温处理和自然条件生长下各项指标的耐热系数,采用主成分分析、隶属函数法、聚类分析和逐步回归分析方法对小麦耐热性进行综合评价。【结果】高温处理下各性状变异幅度为-14.89%—15.09%。通过对9个性状指标的相关分析,发现各指标之间存在显著或极显著相关性。通过主成分分析将9个单项指标转换为3个相互独立的综合指标,其贡献率分别为55.970%、15.530%和12.171%,代表了全部数据83.670%的信息量。利用隶属函数法计算综合耐热评价值（D）,并对其进行聚类分析,按照耐热性强弱将20个小麦品种划分为3类,第一类耐热型8个品种;第二类中等耐热型7个品种;第三类高温敏感型5个品种。通过逐步回归方程建立了小麦耐热性的评价数学模型：D=-4.801+0.834X₄+2.913X₇+0.303X₆+2.937X₈- 1.409X₁-0.524X₃+0.876X₉（R²=0.986）,利用建立的最优回归方程预测供试材料的耐热性,预测值（VP）与D值基本一致,表明SOD活性（X₄）、单穗粒重（X₇）、CAT活性（X₆）、千粒重（X₈）、冠层温度（X₁）、MDA含量（X₃）和产量（X₉）这7个指标可用于小麦耐热性品种的鉴定。【结论】采用多元统计分析方法对小麦耐热性评价是可行的;20个小麦品种被分为3类（耐热型、中等耐热型和高温敏感型）;高温处理下,SOD活性、单穗粒重、CAT活性、千粒重、冠层温度、MDA含量和产量可以作为小麦耐热性的鉴定指标。