High-temperature stress suppresses allene oxide cyclase 2 and causes male sterility in cotton by disrupting jasmonic acid signaling

Cotton(Gossypium spp.) yield is reduced by stress. In this study, high temperature(HT) suppressed the expression of the jasmonic acid(JA) biosynthesis gene allene oxide cyclase 2(GhAOC2), reducing JA content and causing male sterility in the cotton HT-sensitive line H05. Anther sterility was reversed by exogenous application of methyl jasmonate(MeJA) to early buds. To elucidate the role of GhAOC2 in JA biosynthesis and identify its putative contribution to the anther response to HT, we created gene knockout cotton plants using the CRISPR/Cas9 system. Ghaoc2 mutant lines showed male-sterile flowers with reduced JA content in the anthers at the tetrad stage(TS), tapetum degradation stage(TDS), and anther dehiscence stage(ADS). Exogenous application of MeJA to early mutant buds(containing TS or TDS anthers) rescued the sterile pollen and indehiscent anther phenotypes, while ROS signals were reduced in ADS anthers. We propose that HT downregulates the expression of GhAOC2 in anthers, reducing JA biosynthesis and causing excessive ROS accumulation in anthers, leading to male sterility. These findings suggest exogenous JA application as a strategy for increasing male fertility in cotton under HT.

Osmotic Regulation,Antioxidant Enzyme Activities and Photosynthetic Characteristics of Tree Peony(Paeonia suffruticosa Andr.)in Response to High-Temperature Stress

Tree peony(Paeonia suffruticosa Andr.)is a traditional Chinese flower,which prefers cool weather.However,high temperature in summer in the middle and lower reaches of the Yangtze River restricts its growth and development.In this study,osmotic regulation,antioxidant enzyme activities,and photosynthetic characteristics of tree peony in response to high-temperature stress were investigated.The results showed that high-temperature stress had destroyed the cell membrane,manifested as the increased relative electrical conductivity and malondialdehyde content.Moreover,high-temperature stress led to excessive accumulation of reactive oxygen species,thereby,activating antioxidant enzyme activities.Also,photosynthetic parameters and chlorophyll fluorescence parameters directly reflected the damage to the photosystem II reflection center under high-temperature stress.In addition,high-temperature stress led to stomatal closure and chloroplast damage.This study revealed the physiological responses of tree peony to high-temperature stress,laying a foundation for the promotion of tree peony in high-temperature areas and the improvement of high-temperature resistance.

Analysis on high-temperature oxidation and growth stress of iron-based alloy using phase field method

High-temperature oxidation is an important property to evaluate thermal protection materials. However, since oxidation is a complex process involving microstructure evolution, its quantitative analysis has always been a challenge. In this work, a phase field method （PFM） based on the thermodynamics theory is developed to simulate the oxidation behavior and oxidation induced growth stress. It involves microstructure evolution and solves the problem of quantitatively computational analysis for the oxidation behavior and growth stress. Employing this method, the diffusion process, oxidation performance, and stress evolution axe predicted for Fe-Cr-A1-Y alloys. The numerical results agree well with the experimental data. The linear relationship between the maximum growth stress and the environment oxygen concentration is found. PFM provides a powerful tool to investigate high-temperature oxidation in complex environments.

A thermal stress loading technique for large-sized hot dry rock mechanical tests

Testing of large-sized specimens is becoming increasingly important in deep underground rock mechanics and engineering.In traditional mechanical loading,stresses on large-sized specimens are achieved by large host frames and hydraulic pumps,which could lead to great investment.Low-cost testing machines clearly always have great appeal.In this study,a new approach is proposed using thermal expansion stress to load rock specimens,which may be particularly suitable for tests of deep hot dry rock with high temperatures.This is a different technical route from traditional mechanical loading through hydraulic pressure.For the rock mechanics test system of hot dry rock that already has an investment in heating systems,this technology may reduce the cost of the loading subsystem by fully utilizing the temperature changes.This paper presents the basic principle and a typical design of this technical solution.Preliminary feasibility analysis is then conducted based on numerical simulations.Although some technical details still need to be resolved,the feasibility of this loading approach has been preliminarily confirmed.

Daytime Heat Stress, Thermal Pattern, Hyperthermia and Body Caloric Overload in Tropical Acclimatized Holstein and Jersey Heifers

The influence of daytime tropical heat stress in the summer was studied in Holstein and Jersey heifers already acclimatized to tropical environments to determine their physiological response based on body thermal patterns and respiratory alterations according to psychrometric caloric indicators. Daytime psychrometric elements showed a tropical caloric potential for developing moderate to severe heat stress in dairy cattle. Body temperature and respiratory rate increased in both breeds open and pregnant (P < 0.01). Thermal body overload and respiratory works increased from 09 am to 12 md (P < 0.001);reaching and sustaining hyperthermia under the highest caloric pressure from 12 md to 03 pm. Rectal temperature increased +1.5˚C in open Holstein (OH), +1.3˚C in pregnant Holstein (PH), +0.8˚C in open jersey (OJ) and +0.8˚C in pregnant Jersey (PJ). The lowest heat stress index (HSI) was at 06 am, where OH and PH showed a HIS +2.25 and +2.30 and OJ and PJ +2.34 and +2.38. Maximum heat stress occurred at 12 md where OH averaged +3.28 and Pregnant Holsteins showed +3.85 at 03 pm. Open Jersey (OJ) showed a maximum HSI at 12 md (3.54) and PJ resulted in +3.89 at 03 pm. Open and pregnant Jersey heifers were more tolerant to heat stress based on lower body mass, insulation, feed consumption and greater relation between body surface and metabolic body size for thermolysis. Acclimatization between five and twenty-five months under tropical heat stress allowed Holstein and Jersey heifers to develop thermal tolerance. Middle thermal acclimatization lowered thermal sensitivity, hyperthermia and hyperpnea in Holstein and Jersey heifers in the morning;however, pregnant heifers in both breeds showed higher thermal alteration in the afternoon. Tropical acclimatization at low altitudes could be integrated with environmental improvements and nutritional and health management to reduce influences of severe heat stress and improve physiological comfort and welfare in Holstein and Jersey heifers in the summer. Those combined strategies will reduce daytime thermal and respiratory responses and allow growth, pregnancy and health with lower body heat overload and less hyperthermia.

Physiological Response of Spring Soybean Seedlings Under High-temperature Stress

To understand the response characteristics of soybean seedling resistance systems to high-temperature stress,the spring soybean varieties HN44 and HN65 were selected in this study as the experimental materials,as they had substantial differences in stress resistance.Soybean physiological status was studied under high-temperature stress.Sand culture was used in the experiment,and soybeans at the seedling stage were treated with high-temperature stress.The results showed that the activity of antioxidases and osmotic regulatory substance contents in soybean increased under high-temperature treatment for a certain period of time,the activity of antioxidases and osmotic regulatory substance contents decreased after continuous treatment,and high temperatures continuously increased malondialdehyde contents in the two varieties.At high temperatures,the antioxidant activity and osmotic regulator contents of HN44 were higher than those of HN65,and the malondialdehyde contents of HN44 were higher than those of HN65.The above results showed that HN44 soybeans exhibited significantly higher resistance to high-temperature stress than HN65 variety.

Effects of Application of Nitrogen, Potassium and Glycinebetaine on Alleviation of Water Stress to Summer Maize

A pot experiment was conducted under water deficit and adequate water-supplied conditions with two maize genetypic varieties （Shaandan 9 and Shaandan 911） to study the effects of nitrogen, potassium and glycinebetaine （GlyBet） on the dry matter and grain yields as well as water use efficiency （WUE）. Determinations were made at different stages of the two varieties for revealing the function of these factors in increasing plant resistance to drought. Results showed that under a water-stressed condition, dry matter and grain yield were significantly reduced. However, the response of the two varieties to water stress was different： Shaandan 9 was significantly higher in dry matter and grain yields, and therefore could be regarded as a drought-resistant variety compared to Shaandan 911.Application of nitrogen, potassium and glycinebetaine raised dry matter and grain yield to different levels, and thereby alleviated the water stress and increased water use efficiency. These effects were higher for Shaandan 911 than for Shaandan 9. Under water-stressed conditions application of N fertilizer, either at low rate or at high rate, significantly increased dry matter, grain yield and water use efficiency. A significant different effect was found for Shaandan 911 between N rates, but not so for Shaandan 9. However, with supplemental water supply, effects of N fertilization were obviously decreased, showing that in addition to supplying nutrient, N fertilizer has a function in increasing drought-resistance of the crop. Potassium and glycinebetaine exhibited a remarkable function in increasing dry matter and grain yields as well as water use efficiency under water stress while such effects were obviously declined, even vanished, with supplemental water supply, indicating the important contribution of these factors in rise of drought-resistance ability of a crop.

Graphene/carbon structured catalyst layer to enhance the performance and durability of the high-temperature proton exchange membrane fuel cells

In this study,nitrogen doped electrochemically exfoliated reduced graphene oxide and carbon black supported platinum(Pt/Nr EGO_(2)-CB_(3))has been prepared to enhance the performance and durability of hightemperature PEMFCs with lower Pt loading.On the one hand,Pt/Nr EGO_(2)-CB_(3)with the strong interaction between the Pt and nitrogen(N)prevent agglomeration of Pt particles and Pt particles is 5.46±1.46 nm,which is smaller than that of 6.78±1.34 nm in Pt/C.Meanwhile,ECSA of Pt/Nr EGO_(2)-CB_(3)decrease 13.65%after AST,which is much lower than that of 97.99%in Pt/C.On the other hand,the Nr EGO flakes in MEAac act as a barrier to mitigate phosphoric acid redistribution,which improves the formation of triple-phase boundaries(TPBs)and gives stable operation of the MEAacwith a lower decay rate of 0.02 mV h^(-1)within100 h.After steady-state operation,the maximum power density of Pt/Nr EGO_(2)-CB_(3)(0.411 W cm^(-2))is three times higher than that of conventional Pt/C(0.134 W cm^(-2))in high-temperature PEMFCs.After AST,the mass transfer resistance of Pt/Nr EGO_(2)-CB_(3)electrode(0.560Ωcm^(2))is lower than that in Pt/C(0.728Ωcm^(2)).

授粉期高温胁迫对夏玉米植株形态、叶片光合及产量的影响

针对黄淮海地区花期高温影响夏玉米安全生产的问题,本研究以热敏感型品种‘先玉335’为试验材料,以大田常温为对照(CK),设置授粉期高温处理(HT),研究授粉期高温胁迫对夏玉米植株形态、叶片光合特性、干物质积累与分配及产量形成的影响。结果表明:2021年和2022年,HT处理的冠层最高温度超过40℃的天数分别为7 d和8 d,高温处理期间冠层最高温度分别较CK高1.7~6.8℃和1.5~4.6℃。HT处理显著提高了夏玉米株高和穗位高,对茎粗和叶面积无显著影响,但延缓了生育后期叶片衰老,2021年和2022年成熟期的叶面积较CK分别显著提高34.69%和163.72%。高温处理期间,HT处理的玉米叶片气孔导度、蒸腾速率和胞间CO_(2)浓度显著升高(P<0.05,P<0.01),叶片羧化效率、气孔限制值和水分利用效率显著降低(P<0.05,P<0.01);叶片净光合速率随处理温度而变化,处理温度过高(一般>40℃时)则显著降低(P<0.05),反之则显著升高(P<0.05)或无显著变化,叶片整体光合性能下降。高温胁迫解除后,HT处理的叶片光合性能相关参数逐渐与CK趋于一致。经授粉期高温胁迫处理后,玉米茎秆、叶片、苞叶、穗轴和单株干重降低,其中穗轴干重降幅最大,而雄穗和花丝干重增加,使得干物质向茎秆、叶片、雄穗、花丝等部位的分配比例增加,而向穗轴的分配比例显著减少(P<0.05)。至成熟期,HT处理造成玉米籽粒和单株干重显著减少48.32%和16.71%(P<0.05),而玉米茎秆和叶片干重显著增加35.01%和9.48%(P<0.05)。HT处理的结实率和穗粒数分别显著下降54.43%和53.19%(P<0.05),百粒重显著提高10.13%(P<0.05),但籽粒产量显著降低46.82%(P<0.05)。综上,授粉期高温胁迫增强了玉米叶片气孔蒸腾,增加了胞间CO_(2)浓度,降低了叶片羧化效率和水分利用效率,导致植株整体光合性能下降,制约了光合同化物积累及向穗部的转移分配,导致结实率显著下降,穗粒数显著减少,制约了花后光合同化物从“源”(茎秆和叶片)向“库”(籽粒)的转运,最终导致籽粒产量大幅下降。

Rice Heat Tolerance Breeding: A Comprehensive Review and Forward Gaze

The yield potential of rice is seriously affected by heat stress due to climate change. Since rice is a staple food globally, it is imperative to develop heat-resistant rice varieties. Thus, a thorough understanding of the complex molecular mechanisms underlying heat tolerance and the impact of high temperatures on various critical stages of the crop is needed. Adoption of both conventional and innovative breeding strategies offers a long-term advantage over other methods, such as agronomic practices, to counter heat stress. In this review, we summarize the effects of heat stress, regulatory pathways for heat tolerance, phenotyping strategies, and various breeding methods available for developing heat-tolerant rice. We offer perspectives and knowledge to guide future research endeavors aimed at enhancing the ability of rice to withstand heat stress and ultimately benefit humanity.

不同生育期涝渍胁迫对夏玉米产量影响的试验研究

为探明夏玉米在不同生育期对不同形式和历时涝渍胁迫的响应规律,在夏玉米拔节期、抽雄期和灌浆期分别设置1、3、5 d单涝,3、5、7 d单渍和先涝后渍组合胁迫试验,分析各涝渍胁迫对夏玉米产量及其构成、果穗性状、干物质损失和分配的影响。研究结果表明:①拔节期涝渍胁迫使夏玉米减产最多,灌浆期次之,抽雄期最少。3种涝渍胁迫中先涝后渍胁迫减产幅度最大。各生育期夏玉米受同种涝渍胁迫后的减产幅度随胁迫时长的增加而增大。拔节期涝水时长超过3 d都可能使玉米绝收;抽雄期和灌浆期减产最多的均为先涝5 d后渍5 d胁迫,产量显著下降49.1%和82.4%。②百粒重和穗粒数共同影响夏玉米产量,不同生育期涝渍胁迫对两者影响幅度不同。拔节期单涝、先涝后渍胁迫主要减少百粒重;拔节期、灌浆期单渍胁迫和抽雄期、灌浆期先涝后渍胁迫主要减少穗粒数;抽雄期单渍胁迫一并影响穗粒数和百粒重;抽雄期、灌浆期单涝1 d、3 d主要影响百粒重,5 d主要影响穗粒数。③涝渍胁迫使夏玉米果穗性状指标受到影响。涝渍胁迫发生在拔节期使穗长和穗粗变短,抽雄期主要影响穗长,灌浆期主要影响穗粗。涝渍胁迫使夏玉米秃尖长度和秃尖比增加,进而导致产量损失。灌浆期涝渍胁迫对秃尖长度和秃尖比影响最明显。④涝渍胁迫导致夏玉米干物质损失和分配比例变化。拔节期涝水时长超过3 d使籽粒占比归零,穗轴占比降低。抽雄期涝渍胁迫主要影响干物质在茎叶和籽粒间的分配,穗轴占比无明显变化。灌浆期涝渍胁迫使干物质在茎叶、籽粒和穗轴间的分配均受到影响。

淮北平原干旱胁迫对夏大豆土壤耗水量及产量的影响

为探究不同干旱水平在各生育期对夏大豆在砂姜黑土与黄潮土中的影响及差异,基于2022年五道沟实验站桶栽受旱试验,在夏大豆分枝期、花荚期、鼓粒成熟期通过水分控制,设置轻旱、中旱、重旱3个干旱水平与全生育期无旱对照(CK),分析各生育期不同干旱水平胁迫对夏大豆在两种土壤中耗水量、产量、水分利用效率(WUE)的影响及差异。结果表明:(1)两种土壤中夏大豆各生育阶段随干旱加重耗水量呈减小趋势,重旱减小最显著;砂姜黑土中耗水量各受旱组小于对照组,黄潮土除分枝期轻旱外耗水量均低于对照组,且耗水量减少水平除鼓粒成熟期轻旱均小于砂姜黑土。(2)两种土壤重旱对产量影响最强烈,鼓粒成熟期重旱减产最严重;黄潮土花荚期不同受旱水平减产率均低于砂姜黑土,分枝期各受旱组砂姜黑土减产率低于黄潮土。(3)两种土壤花荚期、鼓粒成熟期WUE随干旱程度加剧呈明显递减趋势,重旱影响下WUE减小明显,鼓粒成熟期重旱对WUE影响最严重;受旱减产水平在不同生育阶段存在差异,使得花荚期黄潮土各处理组WUE均高于砂姜黑土,分枝期黄潮土WUE均低于砂姜黑土。

干旱条件下淮北平原夏玉米根系水分来源研究

为探究干旱胁迫条件下淮北平原夏玉米生长期水分利用特征,分析农田降水-土壤水-作物水之间的转化规律。通过野外实验和室内分析,测定分析不同生长期内降水、土壤水、植物水、地下水的稳定氢氧同位素值。采用稳定氢氧同位素技术分析了各水体的同位素分布特征,利用直接对比法和多元线性混合模型法分析夏玉米对土壤水分的主要吸水深度及贡献率,进而研究其水分来源。结果表明,五道沟实验站夏季大气降水线方程为δD=7.26×δ^(18)O+3.11(R^(2)=0.98),其斜率和截距均小于全球大气降水线方程,表明降水在降落过程存在蒸发富集过程。土壤水氢氧同位素在垂直方向剖面呈现明显的梯度分布。干旱胁迫条件下,夏玉米拔节-抽雄期主要吸收0~20、20~40、40~60 cm处的土壤水,贡献率分别为21.8±13.6%、25.5±20%和25.1±18.2%;抽雄-灌浆期主要吸收0~20 cm处的土壤水,贡献率为68.6±3.6%;灌浆-成熟期主要吸收0~20 cm处的土壤水,贡献率为72.0±0.9%。夏玉米根系优先利用浅层土壤水,土壤水主要来自大气降水。地下水埋深较浅地区,干旱条件下夏玉米在整个生长期内根系吸水深度较浅,由此考虑生长期改变灌溉方式来提高灌溉水利用率。

高温越夏日本大葱种质表型性状差异及亲缘关系研究

为了鉴定、筛选出越夏高产大葱种质并用于耐高温品种改良和选育,以42份日本大葱种质为试材,采用形态鉴定方法,在塑料大棚环境下研究了经高温越夏后种质的表型性状差异和亲缘关系远近,并用隶属函数法对初筛种质进行综合评价。结果表明:42份种质单株质量、株高、假茎质量、假茎长、假茎直径、叶长、叶扁宽、宿存叶片数、假茎指数和叶形指数10个数量性状的变异范围为10.50%~38.60%,平均值为19.62%。其中,假茎质量和单株质量变异系数较高,分别为38.60%和37.23%。经聚类分析将42份种质聚为1个高细类型、1个矮细类型、2个矮粗类型亚组共计4个组群,组群间性状差异显著。采用隶属函数法对高细类型、矮粗类型第1亚组14份种质进行种质综合评价,排名为喜太郎晚抽、玖源晚抽、什全一本、夏力源、成田一本、智荣、玖美、咏秀、荣辉、金春一本、卡曼、盛源泰32号、川田一本和揽胜。该研究从形态学角度解析了越夏日本大葱种质遗传差异,明确了不同资源亲缘关系远近,为越夏大葱种质筛选和优势杂交育种亲本选择提供了依据。

涝渍胁迫条件下水分生产函数研究

为预估涝渍综合胁迫对农业生产的影响,以皖北平原典型作物夏大豆和典型涝渍胁迫过程先涝后渍为研究对象,依据2021年6-10月在五道沟水文水资源实验站作物与水关系试验场开展的夏大豆涝渍胁迫试验,建立了涝渍胁迫程度与作物产量间的关系。通过设置不同的涝渍胁迫形式及程度的试验,分析单涝、单渍的理论减产作用,对涝渍综合胁迫过程中的涝害指标SFW和渍害指标SEW_(30)进行统一,对多个水分生产函数进行改进,并对函数参数进行率定、验证及评价。结果表明:在涝渍胁迫敏感因子识别方面,由改进的Blank模型、Singh模型和Hiler模型得到的作物对涝渍胁迫敏感程度更为可靠。在涝渍胁迫条件下的产量预测方面,以Blank模型对大豆不同生育期受涝渍综合胁迫时产量预测精度最高,综合绝对平均误差(MAE)为0.116,并且纳什系数(NSE)最接近1,模型质量最好,其次为Jensen模型、Hiler模型和Singh模型;Stewart模型质量最差,对涝渍胁迫下大豆产量预测MAE达到0.294,RMSE达到0.323,不适合作为涝渍胁迫下水分生产模型使用。研究内容为扩展涝渍胁迫条件下作物水分生产函数计算方法提供了参考,为涝渍综合胁迫下作物相对产量预测提供了理论依据。

Calculation of circulation in the South China Sea during summer of 2000 by the modified inverse method

On the basis of hydrographic data obtained in August 2000 cruise, the circulation in the South China Sea (SCS) is computed by the modified inverse method in combination with SSH data from TOPEX/ERS-2 analysis. For study of the dynamical mechanism, which causes the pattern of summer circulation in the SCS, the diagnostic model (Yuan et al. 1982. Acta Oceanologica Sinica,4(1):1-11; Yuan and Su. 1992. Numerical Computation of Physical Oceanography.474-542) is used to simulate numerically the summer circulation in the SCS. The following results have been obtained. (1) The central and southwestern SCSs are dominated mainly by anticy-clonic circulation systems. They are mainly as follows. 1) There is strong anticyclonic eddy southeast of Vietnam (W1). Its horizontal scale is about 300 km, and it extends vertically from the surface to the about 1 000 m level. 2) There are a warm eddy W2 southeast of Zhongsha Islands and the anticyclonic circulation system W3 west off the Luzon Island. 3) There is a stronger cyclonic eddy C1 between the anticyclonic eddies W1 and W2.4) A strong northward coastal jet is present near the coast of Vietnam, and separates from the coast of Vietnam at about 12° N to the northeast.(2)The northern SCS is dominated mainly by a cyclonic circulation system. There is a cyclonic circulation system near and north of Section N2. (3) The southeastern SCS is dominated mainly by the cyclonic circulation system. (4) Comparing the results of circulation in the SCS during the summer of 2000 with those during the summer of 1998, it is found that they agree qualitatively, but there is the some difference between them in quantity.This shows that the circulation in the SCS has obviously seasonal feature. (5) The dynamical mechanism which products the basic pattern of summer circulation is because the following two reasons: 1) the joint effect of the baroclinity and relief (JEBAR) is essential dynamical cause; and 2) it is next important dynamical cause that the interaction between the wind stress and bottom topography under the southerly monsoon. (6) Comparing the hydrographic structure and distribution of stream functions with the SSH data from TOPEX/ERS-2 analysis in the SCS during August of 2000, they agree qualitatively.

The effects of sulfide stress cracking on the mechanical properties and intergranular cracking of P110 casing steel in sour environments

Variation and degradation of P-110 casing steel mechanical properties, due to sulfide stress cracking （SSC） in sour environments, was investigated using tensile and impact tests. These tests were carried out on specimens, which were pretreated under the following conditions for 168 hours： temperature, 60 ℃; pressure, 10 MPa; H2S partial pressure, 1 MPa and CO2 partial pressure, 1 MPa; preload stress, 80% of the yield strength （os）; medium, simulated formation water. The reduction in tensile and impact strengths for P-110 casing specimens in corrosive environments were 28% and 54%, respectively. The surface morphology analysis indicated that surface damage and uniform plastic deformation occurred as a result of strain aging. Impact toughness of the casing decreased significantly and intergranular cracking occurred when specimens were maintained at a high stress level of 85% %.

Towards a more flexible representation of water stress effects in the nonlinear Jarvis model

To better interpret summer maize stomatal conductance （gs） variation under conditions of changing water status at different growth stages, three water stress indicators, soil water content （SWC）, leaf-air temperature difference （AT） and leaf level water stress index （CWSIL） were employed in Jarvis model, which were Js, JT and Jc models respectively. Measurements of gs were conducted in a summer maize field experiment during the year 2012-2013. In the insufficient irrigation exper- iment, three levels of irrigation amount were applied at four different growth stages of summer maize. We constructed three scenarios to evaluate the performance of the three water stress indicators for estimating maize gs in a modified Jarvis model. Results showed that JT and Jc models had better simulation accuracy than the Js model, especially at the late growth stage （Scenario 1） or considering the plant recovery compensation effects （Scenario 2）. Scenario 3 indicated that the more environmental factors were adopted, the better prediction performance would be for Js model. While for JT model, two environmental factors （photosynthesis active radiation （PAR）, and vapor pressure deficit （VPD）） seemed good enough to obtain a reliable simulation. When there were insufficient environmental data, CWSI, would be the best option. This study can be useful to understand the response of plant stomatal to changing water conditions and will further facilitate the application of the Jarvis model in various environments.

增施氮肥对夏玉米花后高温胁迫下籽粒碳氮代谢的影响

花后高温是影响黄淮海夏玉米籽粒灌浆及产量形成的主要逆境胁迫之一。目前关于增施氮肥缓解灌浆期高温胁迫对小麦、玉米和水稻等作物产量形成的抑制作用已得到证实,但相关调控途径及其生理机制尚不明确。本研究选用郑单958(Zhengdan 958,ZD958)和先玉335(Xianyu 335,XY335)2个玉米品种为试验材料开展盆栽试验,设置2个温度处理,分别为自然环境温度(ambient temperature,CK)和温室增温处理(heat stress,HS);3个施氮水平,分别为低施氮量(low nitrogen application rate,LN):120 kg hm–2,中施氮量(middle nitrogen application rate,MN):240 kg hm–2和高施氮量(high nitrogen application rate,HN):360 kg hm–2,研究增施氮肥对花后初期高温胁迫下玉米碳氮代谢的影响。结果表明,与自然温度比,花后增温(35℃)处理20 d导致ZD958和XY335两个品种的成熟期粒重降低10.6%~19.3%,但粒重降幅随着施氮量增加而下降,中施氮量(MN)和高施氮量(HN)下粒重降幅(10.6%~11.2%)小于低施氮量(LN)下粒重降幅(16.2%~19.3%),说明增施氮肥可以显著提高花后高温胁迫下的玉米粒重。这主要是因为增施氮肥有效缓解了花后初期高温胁迫对玉米籽粒氮代谢的抑制作用,显著提高了谷氨酰胺合成酶(GS)和谷氨酸合成酶(GOGAT)等氮代谢关键酶活性,同时维持了碳代谢关键酶蔗糖磷酸合成酶(SPS)和蔗糖合成酶(SS)活性,促进了籽粒可溶性糖合成增加,从而保证了较高的籽粒灌浆物质基础。综上所述,增施氮肥可以缓解玉米花后初期高温胁迫对籽粒碳、氮代谢的抑制,促进籽粒中同化物积累而增加粒重,为黄淮海区夏玉米抗逆稳产栽培提供了思路。

华北平原40年夏玉米作物系数变化及影响因素

作物系数(作物实际蒸散量与参考作物蒸散量之比,Kc)作为农田需耗水确定的关键参数,对农业精准灌溉和节水具有重要的参考价值。研究作物系数如何受生产条件和气象条件变化的影响,可为准确确定作物系数提供依据。本研究基于中国科学院栾城农业生态系统试验站1980—2018年充分灌溉条件下夏玉米作物系数变化规律及影响因素,利用2019—2021年夏玉米不同灌水处理下的试验数据,确定不同供水条件下夏玉米作物系数的计算方法。结果表明,1980—2018年参考作物蒸散量(ETo)基本保持稳定,但存在年际波动。充分供水条件下夏玉米实际蒸散量(ETc)在2005年之前保持年际间稳定,近年来年际间波动幅度较大。作物实际蒸散量与参考作物蒸散量之比的作物系数多年平均值为0.91,年际变异系数为12.36%。作物系数受作物产量和大气条件影响,产量的增加伴随着夏玉米实际蒸散量的增加,参考作物蒸散量主要受平均风速和日照时数的影响。分析表明作物系数由参考作物蒸散量和实际蒸散量共同决定,且受夏玉米实际蒸散量的影响较大。灌水量的差异是造成相同年份不同处理间差异的主要因素。利用缺水处理下土壤水分状况和不同土层相对根长密度计算土壤水分胁迫系数,结果表明使用缺水灌溉处理的土壤有效水分含量对夏玉米作物系数进行校正,所得值与实际值最为接近,可根据计划控制的土壤水分状况调整作物系数,确定不同控水条件下的农田实际耗水量。