基于MODIS-NDVI遥感数据以及地表气象数据,计算了2001-2013年华北地区的修正Palmer干旱指数（Palmer Drought Severity Index,PDSI）和植被覆盖度,总结出植被覆盖度以及PDSI的年际变化规律,从华北地区生态分区的角度分析了二者的相关关系。结果表明：① 华北平原的植被覆盖度呈南高北低、中部高四周低的分布特点,最低为内蒙古高原草原生态区的0.61,最高为淮阳丘陵地区的0.84;② 2001-2013年,华北平原整体植被覆盖度主要呈上升趋势,其中华北的北部、西部、南部山区及丘陵地带植被覆盖度主要呈上升趋势,而华北平原农业区以及京津唐城郊地带植被覆盖度呈下降趋势;③ 华北地区的东北部有变潮湿的趋势,南部则有变干旱的趋势,其他地区干旱条件变化不明显;④ 华北地区植被覆盖度与气候干旱程度的平均相关系数为0.20,73.37%的地区相关系数为正,正相关关系最为明显的地区为华北地区的西北部,而北京、天津、以及河北省与河南省一级、二级城市的城郊地区相关系数多为负值。⑤ 在华北大部分地区,夏季和秋季的气候干旱条件对植被覆盖度的影响最为明显。

Based on previous studies, the climate drought index can be used to assess the evolution trend of ecological environment under various arid climatic conditions. It is necessary for us to further explore the relationship between vegetation coverage (index) and climate drought conditions. Therefore, in this study, based on MODIS-NDVI products and meteorological observation data, the Palmer Drought Severity Index (PDSI) and vegetation coverage in North China were first calculated. Then the interannual variation of PDSI and vegetation coverage over 2001-2013 was analyzed by using a Theil-Sen slope estimator. Finally in an ecoregion perspective the correlation between them was discussed. The experimental results demonstrated that PDSI index and vegetation coverage value varied over different ecoregions. During the period 2001-2013, vegetation coverage increased in southern and northern mountains in North China, while it showed a decreasing trend in Beijing-Tianjin-Tangshan City Circle area and suburban agricultural zone. During the 13 years, the climate of the northeastern part of North China became more humid, while in the southern part of North China, it tended to be dry. According to the correlation analysis results, 73.37% of North China had a positive correlation between the vegetation coverage and climate drought index. A negative correlation was observed mainly in urban and periurban areas of Beijing, Tianjin, Hebei Province and Henan Province. In most parts of North China, drought conditions in summer and autumn had more influence on vegetation coverage.

[目的]明确新疆南部极端干旱区滴灌小麦目前灌量是否合理及灌水量阈值.通过分析新疆南部极端干旱区滴灌小麦在水分利用方面的现状,为进一步解析滴灌冬小麦产量提升及节水灌溉的关键要素和限制因子提供研究基础.[方法]设计四种减量灌溉模式(总灌量分别为3 376、3 000、2 625和2 250 m3/hm2).以常规灌量为对照(总灌量为3 750 m3/hm2).监测冬小麦产量及水分利用效率.[结果]D4处理(灌量2250 m3/hm2)到D3处理(灌量2 625 m3/hm2)产量逐步增加,D3处理产量最高为9 450.kg/hm2,随灌溉量的增加,产量逐步降低.[结论]D4(灌溉量2 250 m3/hm2)到D2处理(灌溉量3 000 m3/hm2)水分利用效率逐步增加,而后波动性下降.说明灌溉量超出其阈值,水分利用效率随灌溉量的增加反而减少.

探究大气CO₂浓度倍增条件下冬小麦气体交换参数对高温干旱及复水过程的生理响应机制, 有助于提高生态过程模型的模拟精度, 更加准确地预测全球气候变化对农田生态系统初级生产力及其生态服务功能的影响。利用4个可精准控制CO₂浓度和温度的大型人工气候室, 研究了CO₂浓度倍增条件下高温干旱及复水过程对冬小麦气孔特征和气体交换参数的影响。结果表明, CO₂浓度倍增(E)导致冬小麦远轴面气孔密度增加、气孔宽度减小、气孔空间分布规则程度降低, 但提高叶片的净光合速率(P_n)、气孔导度(G_s)、蒸腾速率(T_r)和水分利用效率(WUE)。高温干旱(HD)使叶片气孔长度、密度、周长和面积减小, 导致叶片气体交换参数均显著下降。然而, 高CO₂浓度及高温干旱(EHD)导致气体交换参数下降幅度相对较小, 表明高CO₂浓度对高温干旱具有一定的缓解作用。此外, 干旱复水后, 不同处理条件下冬小麦叶片气体交换参数均有所升高, 但高温干旱下叶片的气体交换参数仍未能恢复到对照水平, 暗示光合器官可能在高温干旱时遭到损伤和破坏。

Understanding the responsible mechanisms of crops to combined environmental stresses such as elevated CO2 concentration, climate warming, and drought is critical to improve the accuracy of ecological process models, and thus accurately predict the impacts of global climate change on the Net Primary Production (NPP) and ecosystem service function of farmlands. Four environmental growth chambers accurately controlling CO2 concentration and temperature were employed to investigate the combined effects of high temperature and drought stresses on the stomatal traits and leaf gas exchange during re-watering under doubling CO2 concentration. We found that elevated CO2 concentration (E) increased the stomatal density, decreased the stomatal width and made the spatial distribution pattern of stomata irregular on the abaxial leaf surface, while enhanced the net photosynthetic rates (Pn), stomatal conductance (Gs), transpiration rates (Tr), and water use efficiency (WUE). The stomatal length, width, perimeter and area were substantially decreased under the combined high temperature and drought stress (HD), resulting in dramatic decline of leaf gas exchange parameters. Doubling CO2 concentration made the leaf gas exchange parameters enhanced under the HD treatment, suggesting that elevated CO2 concentration can compensate the negative impacts of heat and drought on the physiological processes of winter wheat. Additionally, the leaf gas exchange of winter wheat subjected to the high temperature and drought stresses was enhanced after re-watering, but these parameters were still lower than those of Control, suggesting that the photosynthetic apparatus may be damaged by the combined high temperature and drought stresses.

【目的】研究两个枣品种在高温环境下光合特性及相关生理指标的差异。【方法】以10 a生骏枣和伏脆蜜为对象,在吐鲁番田间自然高温条件下,测定光合日变化参数,采集相同部位叶片,测定丙二醛(MDA)、渗透调节物质。【结果】伏脆蜜的净光合速率(P_n)为单峰型;骏枣则呈双峰型,且在12:00有明显的光合午休现象。两品种蒸腾速率(T_r)均呈双峰型,但伏脆蜜的蒸腾速率(T_r)变化更剧烈,在14:00有明显的谷值。两品种的丙二醛(MDA)、脯氨酸(Pro)和可溶性蛋白(SP)含量变化趋势基本一致,其中骏枣的MDA和Pro明显高于伏脆蜜,且MDA含量骏枣较伏脆蜜提前4 h达到最大值。【结论】高温环境下,伏脆蜜无光合午休现象,叶片的净光合速率(P_n)和蒸腾速率(T_r)较骏枣高;骏枣叶片MDA和Pro含量明显高于伏脆蜜,其叶片细胞膜受损比伏脆蜜重。光合特性和生理指标两方面均证明伏脆蜜细胞膜稳定性较强,耐高温能力优于骏枣。

【Objective】 To study the differences of photosynthesis and physiological responses to heat stress between two jujube cultivars in the areas of atypical warmth.【Method】The photosynthetic diurnal changes of 10-year-old Fucuimi and Junzao were determined under natural high-temperature conditions in the field of Turpan. Meanwhile, the leaves at the corresponding time were collected to determine the contents of malondialdehyde (MDA), osmoregulation substances in the laboratory. 【Result】The results showed that diurnal variation of net photosynthetic rate(<i>P_n</i>) of Fucuimi was single-peak curve, while that of Junzao was a typical bimodal curve with noon break at 12 o&apos;clock. The Transpiration rate (<i>T_r</i>) of the two cultivars showed a bimodal curve, but Fucuimi changed more drastically, with obvious troughs at 14 o&apos;clock. The trends of MDA, proline (Pro), and soluble protein (SP) content in the two varieties were the same. The MDA and Pro of Junzao were significantly higher than that of Fucuimi. The content of MDA in Junzao reached the maximum value 4 hours earlier than Fucuimi.【Conclusion】In the high temperature areas, Fucuimi didn&apos;t have a noon break in photosynthetic, and it&apos;s <i>P_n</i> and <i>T_r</i> of the leaves were higher than those of Junzao. The contents of MDA and Pro in the leaves of Junzao were significantly higher than those of Fucuimi. Both photosynthetic characteristics and physiological indexes proved that the cell membrane stability of Fucuimi was stronger than that of Junzao. Fucuimi was more resistant to high temperatures than Junzao.

目的 针对不断增高的大气二氧化碳(CO₂)浓度和温度,研究这两个重要环境因子及其互作对大田生长水稻叶片叶绿素含量和SPAD值的动态影响。方法 利用农田T-FACE(Temperature-Free Air CO₂ Enrichment)系统,以高产优质粳稻武运粳23为供试材料,设置两个CO₂浓度(环境CO₂浓度和高CO₂浓度)和两个温度处理(环境温度和高温),测定自然生长环境下水稻不同生育期叶片的叶绿素含量及SPAD值。结果 550 &#x000b5;mol/molCO₂浓度使水稻移栽后41、77、94 d叶绿素a,b和a+b含量均增加(最大增幅为6.4%),但移栽110、119 d后均减少(最大降幅为5.4%)。由于叶绿素b含量对CO₂较叶绿素a含量更敏感,故高CO₂浓度使移栽后41、77和94 d叶绿素a/b值均下降,降幅分别为4.7%、2.3%和0.9%,但移栽110和119 d后分别增加1.9%和5.3%;以上对CO₂的响应多达显著水平。对叶片SPAD值而言,高CO₂浓度对水稻生长前、中期的影响较小,但移栽110和119 d后分别下降3.5%(P=0.1)和19.1%(P&#x0003C;0.01)。大田生长期增温1℃,各期叶绿素a、b以及a+b含量多呈增加趋势,叶绿素a/b值表现相反,但总体上变幅小于CO₂效应;高温对水稻前、中期叶片SPAD的影响较小,但移栽110和119 d后SPAD值平均下降7.1%和14.8%,均达极显著水平。CO₂与温度处理对上述测定参数多无显著互作效应,但CO₂浓度、温度处理与生育期之间多存在明显的互作效应。结论 大气CO₂浓度增高有利于水稻生长前中期叶片叶绿素的形成,但生长后期叶绿素含量和SPAD值均明显下降且伴随叶绿素a/b值的显著升高,这种早衰现象在不同生长温度下趋势一致。

【Objcetive】In view of the potential impacts of increasing atmospheric carbon dioxide (CO2) concentration and air temperature, the dynamic effects of these two important environmental factors and their interaction on leaf chlorophyll contents and SPAD values of rice in field were studied.【Method】 By using T-FACE(Temperature-Free Air CO2 Enrichment) facility, a high yield and excellent-quality japonica rice (Oryza sativa L.) Wuyunjing 23 was grown at two levels of CO2 (ambient and elevated CO2 concentration) and two temperature regimes (ambient and elevated temperature) in a field experiment. We measured leaf chlorophyll contents and SPAD values during the whole growth period of rice plants.【Result】Elevated CO2 concentration increased chlorophyll a, b, a+b contents of rice on 41, 77 and 94 days after transplanting (DAT), with the maximum increase of 6.4%. On the contrary, they were decreased by elevated CO2 concentration on 110 and 119 DAT, with the maximum decrease of 5.4%. Due to the greater responses of chlorophyll b to CO2 concentration than that of chlorophyll a, elevated CO2 concentration decreased chlorophyll a/b ratio on 41, 77 and 94 DAT by 4.7%, 2.3% and 0.9%, but increased it on 110 and 119 DAT by 1.9% and 5.3%, respectively. No obvious effect of elevated CO2 concentration on leaf SPAD values was detected in the early and middle growth stages. But elevated CO2 concentration decreased leaf SPAD values by 3.5% (P=0.1) and 19.1% (P<0.01) on 110 and 119 DAT. 1℃increase in temperature on average had positive effects on chlorophyll a, b, a+b contents in each growth stage of rice, but negative effects were found on chlorophyll a/b ratio. In general, the magnitudes of variation induced by temperature were less than those by elevated CO2 concentration. No obvious effect of temperature elevation on leaf SPAD values was detected in the early and middle growth stages. But temperature elevation deceased leaf SPAD values by 7.1% (P<0.01) and 14.8% (P<0.01) on 110 and 119 DAT, respectively. No CO2-temperature interaction was detected for most of measured parameters, but significant CO2- or temperature-growth stage interactions were found.【Conclusion】The results indicated that elevated CO2 concentration favored the leaf chlorophyll formation of rice in the early and middle growth stages. But in the late growth stage, leaf chlorophyll contents and SPAD value declined, meanwhile chlorophyll a/b ration increased significantly. Such phenomenon of quick-leaf-senescence induced by elevated CO2 concentration was identical under the two temperature regimes.

[目的]通过对11个新疆主要优良杏品种的叶绿素荧光参数及其日变化的观测,旨在了解其荧光特性和对塔里木盆地高光热环境的适应差异,以期为优良杏品种在环塔里木盆地的推广应用提供参考.[方法]采用调制式OS-30P荧光仪测定了供试品种的初始荧光(Fo)、最大荧光(Fm)、PSII最大光能转化效率(Fv/Fm)和PSII最大光能转化潜力(Fv/Fo)4个叶绿素荧光参数随太阳总辐射、空气温度和空气相对湿度变化的日变化以及不同作用光强下从初始荧光上升到最大荧光一半所需时间(T 1/2)的变化特征.[结果]11个测试杏品种的叶绿素荧光参数Fv/Fm和Fv/Fo品种间差异不显著(P>0.05),巴都玉吕克、大果胡安娜、阿克西米西全天具有相对较高的Fv/Fm 和Fv/Fo,粗黑叶杏、木牙格的Fv/Fm 和Fv/Fo日均值相对较低;Fo、Fm的品种间差异达到了极显著水平(P<0.01);在时间序列上Fv/Fm、Fv/Fo、Fo和Fm均表现为差异极显著(P<0.01);粗黑叶杏、木牙格的叶绿素荧光参数T1/2下午相比上午明显下降.[结论]测试品种耐光抑制能力的强弱为:巴都玉吕克、大果胡安娜、阿克西米西耐光抑制能力最强,雀斑杏、索格佳娜丽、库买提、细黑叶杏、黑叶杏、佳娜丽其次,粗黑叶杏、木牙格耐光抑制能力最弱.

【目的】 研究南疆滴灌冬小麦氮素吸收和利用特征,为揭示滴灌冬小麦氮素高效利用机制打下基础。【方法】 以新冬22号为材料,开展水氮裂区设计试验,滴施纯氮为主区,设N₁(138 kg/hm²)、N₂(207 kg/hm²)、N₃(276 kg/hm²)和N₀(对照,不施氮肥)4个水平;滴水量为副区,在统一冬灌900 m³/hm²的基础上,起身期以后设W₁(1 800 m³/hm²)、W₂(3 150 m³/hm²)、W₃(4 500 m³/hm²)3个滴灌水平,共12个处理。【结果】 (1)适当增加水氮供应量有利于提高冬小麦植株氮素积累量,其中N₃W₂、N₃W₃、N₂W₂和N₂W₃处理的积累量显著高于其他处理。(2)开花前是氮素积累量的主要时期,其平均积累量占总积累量的78.28%,拔节-扬花期是氮素吸收速率高峰期,并以N₃W₂、N₂W₃和N₂W₂处理最高,分别达6.38、5.81和5.01 kg/(hm²·d)。(3)各器官氮素转运量及对籽粒氮素积累的贡献率大小为叶片>茎鞘>颖壳+穗轴;N₃W₂和N₂W₃处理的营养器官氮素转移量显著高于其他处理,达158.34和147.49 kg/hm²;N₃W₂、N₂W₂和N₂W₃处理的籽粒蛋白质含量及蛋白质产量显著高于其他处理,分别达15.73%、15.41%和14.18%及1 475.94、1 256.97和1 217.78 kg/hm²。(4)滴灌冬小麦的产量构成及水、氮利用效率具有显著的水氮耦合效应,N₃W₂、N₂W₃和N₂W₂处理的产量较高,其氮肥农学利用率、氮肥利用效率及灌溉水利用效率也最大。【结论】 207~276 kg/hm²的施氮量和3 150~4 500 m³/hm²的春季滴水量是该地区较合适的水氮供应范围,当施氮量为275.08 kg/hm²和滴水量为4 457.89 m³/hm²包括冬灌900 m³/hm²时,产量可达最大为8 558.73 kg/hm²。

<strong>【Objective】 </strong> To clarify the mechanism of efficient use of nitrogen, the characteristics of N absorption and utilization of winter wheat in drip irrigation in southern Xinjiang were studied.<strong>【Method】</strong> Xindong 22 was used as testing material, and split plot design was used where the main zone was fertigation treatments including N₀(0 kg/hm²), N₁(138 kg/hm²), N₂(207 kg/hm²) and N₃(276 kg/hm²); deputy district was drip irrigating treatments including W1(1,800 m³/hm²),W2(3,150 m³/hm²) and W3(4,500 m³/hm²) in spring based on the unified winter irrigation of 900 m³/hm².<strong>【Result】</strong> (1) Proper increase of water and nitrogen supply was beneficial to increase nitrogen accumulation in winter wheat, and nitrogen accumulation of N₃W₂, N₃W₃, N₂W₂ and N₂W₃ was significantly higher than that of other treatments. (2) The main period of nitrogen accumulation was before anthesis with 78.28% of the total accumulation. The jointing-flowering stage was the peak of nitrogen uptake rate, and with N₃W₂, N₂W₃ and N₂W₂ treatments reaching the highest of 6.38 kg/(hm²·d), 5.81 kg/(hm²·d) and 5.01 kg/(hm²·d), respectively.(3) The amount of nitrogen translocation in each organ and its contribution rate to nitrogen accumulation of grain were leaf >stem + sheath > spike axis + glume. Nitrogen translocation amount in vegetative organs of N₃W₂ and N₂W₃ was significantly higher than that by other treatments, reaching 158.34 kg/hm² and 147.49 kg/hm², the grain protein content and protein yield of N₃W₂, N₂W₂ and N₂W₃ were significantly higher than those by other treatments, reaching 15.73%, 15.41% and 14.18%,1,475.94 kg/hm², 1,256.97 kg/hm² and 1,217.78 kg/hm², respectively.(4) The yield components and water and nitrogen use efficiency of winter wheat under drip irrigation have significant coupling effects of water and nitrogen, the yields of N₃W₂, N₂W₃ and N₂W₂ were higher, and their agronomic efficiency of nitrogen fertilizer, nitrogen use efficiency and irrigation water use efficiency were also the largest.<strong>【Conclusion】</strong> 207-276 kg/hm² nitrogen rate and 3,150-4,500 m³/hm² spring drip amount were the suitable supply range in this region. When the nitrogen amount was 275.08 kg/hm², the drip irrigation was 4,457.89 m³/hm² (including winter irrigation of 900 m³/hm²), the yield could reach the maximum of 8,558.73 kg/hm².

Water availability for plant growth is becoming increasingly limited, whereas rising atmospheric carbon dioxide concentration may have interactive effects with drought stress. The objectives of this study were to determine whether elevated CO2 would mitigate drought-induced water deficit and photosynthesis inhibition and enhance recovery from drought damages on rewatering and to determine whether the mitigating effects during drought stress and the recovery in photosynthesis during rewatering by elevated CO2 were the result of the regulation of stomatal movement or carboxylation activities in tall fescue (Festuca arundinacea Schreb. cv. Rembrandt). Plants were grown in controlled-environment chambers with ambient CO2 concentration (400 μmol·mol−1) or elevated CO2 concentration (800 μmol·mol−1) and maintained well watered (control) or subjected to drought stress and subsequently rewatered. Elevated CO2 reduced stomatal conductance (gS) and transpiration rate of leaves during both drought stress and rewatering. Osmotic adjustment and soluble sugar content were enhanced by elevated CO2. Elevated CO2 enhanced net photosynthetic rate with lower gS but higher Rubisco and Rubisco activase activities during both drought and rewatering. The results demonstrated that elevated CO2 could improve leaf hydration status and photosynthesis during both drought stress and rewatering, and the recovery in photosynthesis from drought damages on rewatering was mainly the result of the elimination of metabolic limitation from drought damages associated with carboxylation enzyme activities.

Analysis of survival is commonly used as a means of comparing the performance of plant lines under drought. However, the assessment of plant water status during such studies typically involves detachment to estimate water shock, imprecise methods of estimation or invasive measurements such as osmotic adjustment that influence or annul further evaluation of a specimen's response to drought.

为研究依据不同土层的土壤质量含水量进行测墒补灌对小麦(Triticum aestivum)拔节期与开花期旗叶荧光特性和水分利用效率的影响, 2011&ndash;2012和2012&ndash;2013年度两个小麦生长季, 设置0&ndash;20 (D1)、0&ndash;40 (D2)、0&ndash;60 (D3)和0&ndash;140 cm (D4) 4个土层进行处理, 测定土壤质量含水量, 以各土层平均土壤相对含水量在拔节期为65%和在开花期为70%为目标相对含水量进行补灌, 全生育期不灌溉为对照(D0)。结果表明: (1) D2处理拔节至开花期40&ndash;100 cm土层和开花至成熟期40&ndash;140 cm土层的土壤贮水消耗量高于其他处理, 开花至成熟期是小麦贮水消耗的最大时期。(2)开花后旗叶水分利用效率、PSII潜在活性(F_v/F_o)、PSII电子传输活性(F_m/F_o)、相对电子传递速率(ETR)和光化学猝灭系数(q_P) D2处理最高, D3次之, D0最低。(3)两个小麦生长季, 各处理的籽粒产量为D2 > D3 > D1 > D4 > D0, D2的水分利用效率分别为20.19 kg&middot;hm^&ndash;2&middot;mm^&ndash;1和21.92 kg&middot;hm^&ndash;2&middot;mm^&ndash;1, 高于D0、D3和D4处理, 与D1处理间无显著差异。综合分析, 小麦拔节期和开花期依据0&ndash;40 cm土层的土壤质量含水量进行测墒补灌可兼顾高产和高水分利用效率。

<p><em>Aims</em> Our objective was to determine the effects of supplemental irrigation by measuring the moisture content at jointing and anthesis on fluorescence characteristics and water use efficiency in flag leaves of wheat (<em>Triticum aestivum</em>).</br><em>Methods</em> Four irrigation treatments were imposed, i.e. the average relative soil water content in the soil layer of 0&ndash;20 cm (D1), 0&ndash;40 cm (D2), 0&ndash;60 cm (D3), and 0&ndash;40 cm (D4) were raised to 65% (at jointing) and 70% (at anthesis), respectively, by supplemental irrigation, with zero-irrigation as a control treatment (D0) in 2011&ndash;2012 and 2012&ndash;2013.</br><em>Important findings</em> The soil water consumption in the D2 treatment was significantly higher than in other treatments in the 40&ndash;100 cm soil layer from jointing to anthesis and in the 40&ndash;140 cm soil layer from anthesis to maturity; the latter stage showed the highest soil water consumption during wheat growing. The flag leaves of wheat plants in the D2 treatment showed the highest water use efficiency, potential photosynthesis activity of PSII (<em>F</em>_v/<em>F</em>_o), electronic transpiration activity of PSII (<em>F</em>_m/<em>F</em>_o), relative electron transport rate (<em>ETR</em>) and photochemistry quenching index (<em>q</em>_P) after anthesis, followed by the D3 treatment, with those in the D0 treatment having the lowest values. In both growing seasons, the grain yield was ranked in the order of D2 > D3 > D1 > D4 > D0 among the treatments; water use efficiency (<em>WUE</em>) in the D2 treatment was 20.19 kg&middot;hm^&ndash;2&middot;mm^&ndash;1 and 21.92 kg&middot;hm^&ndash;2&middot;mm^&ndash;1, respectively, higher than in the D0, D3, and D4 treatments. No significant difference was observed in any of the variables between the D1 and D2 treatments. Hence, the D2 treatment, with application of irrigation based on the soil moisture measurement in the 0&ndash;40 cm soil layer at jointing and anthesis, is the most optimal treatment for achieving high grain yield and high <em>WUE</em>.</p>

为了探寻快速高效筛选冬小麦抗旱品种的方法，给冬小麦抗旱品种筛选提供参考依据，以烟农999、泰麦1918、济麦22号、济麦23号、泰山27和师栾02-1 6个冬小麦品种为供试材料，设置正常水分处理（土壤相对含水量75%）、轻微干旱处理（土壤相对含水量55%）和中度干旱处理（土壤相对含水量40%），研究了苗期叶绿素荧光参数、生物量、根冠比、SPAD、超氧化物歧化酶（SOD）活性和丙二醛（MDA）含量及其之间相关关系。结果表明：与其他冬小麦品种相比，干旱胁迫下，泰麦1918的抗旱系数（DTC）最大，根冠比降低程度最小，SPAD值、光系统Ⅱ最大光合效率（Fv/Fm）、光系统Ⅱ实际光合效率（φPSⅡ）和相对电子传递速率（ETR）的降低程度最小，SOD活性的降低程度最小，非光化学淬灭（NPQ）升高程度最大，丙二醛含量升高程度最小。6个供试冬小麦品种的抗旱性强弱依次为泰麦1918 > 烟农999 > 济麦22号 > 济麦23号 > 泰山27 > 师栾02-1。通过相关性分析发现，叶绿素荧光参数与抗旱系数、SOD活性以及MDA含量的相关性均达到极显著水平。综上，供试材料中泰麦1918的抗旱性最强，叶绿素荧光参数可作为在苗期筛选冬小麦抗旱性品种的重要依据。

[目的]针对土壤高湿和干旱影响夏玉米籽粒灌浆并对其造成减产的灾害问题,为了揭示其致灾的生理机制,[方法]2016年在夏玉米生长季通过人工控制土壤水分,设计了土壤高湿、干旱和对照3种处理,在玉米灌浆期测定叶片的光合特性日变化、光饱和点和光补偿点、夜间叶片暗呼吸等。[结果]结果表明：对照玉米叶片的净光合速率日变化曲线呈双峰型,即“M”型,而高湿处理被弱化为单峰型,干旱处理全天持续走低。气孔导度(Gs)和蒸腾速率(Tr)的日变化规律一致,呈显著正相关；胞间CO2浓度(Ci)和水分利用效率(WUE)的日变化曲线呈反向变化,呈显著负相关。高湿处理的叶片暗呼吸比对照提高0.5800-0.7767μmolCO2m-2.s-1,干旱处理比对照降低0.1767-0.4933μmolCO2m-2.s-1,可能因为土壤高湿情况下,玉米叶片等绿色器官呼吸作用强导致果穗籽粒养分积累少进而造成减产；分析光饱和点和光补偿点发现,高湿处理光合作用有效利用光强的区间拉大,干旱胁迫下,光合作用有效利用光强的区间缩小,这可能是玉米灌浆期干旱造成减产的主要生理原因。

Aiming at the effects of high humidity and drought on grain filling and yield reduction of summer maize, and revealing its physiological mechanism to disaster, the authors designed 3 treatments of high humidity, drought and control of soil in the summer maize growing season by artificially controlling soil moisture in 2016, and measured the diurnal variation of photosynthetic characteristics, light saturation point, light compensation point and dark respiration of leaves at night at the grain filling stage. The results showed that: the diurnal variation curve of the net photosynthetic rate of maize leaves was bimodal, that was“M”, while that of the high humidity treatment was weakened into a single-peak pattern, and that of the drought treatment continued to decline throughout the day; the diurnal variation law of stomatal conductance (Gs) and transpiration rate (Tr) was consistent and they had a significant positive correlation; while that of intercellular CO2 concentration (Ci) and water use efficiency (WUE) showed a negative correlation; the dark respiration under the high humidity treatment increased by 0.5800-0.7767 μmol CO2/(m2 &middot;s) compared with that of the control, while that of the drought treatment reduced by 0.1767-0.4933 μmol CO2/(m2&middot;s) compared with that of the control, the reason for this situation might be that the high humidity condition led to the intensified respiration process of maize leaves and other green organs, which resulted in the decrease of nutrient accumulation in grains and ergo the drop of yield; according to the analysis of light saturation points and light compensation points, the interval of photosynthesis effectively using light under high humidity treatment expanded, while under drought stress, that value went down, which might be the main physiological reason for the reduction of maize yield resulting from drought at the grain filling stage.

<p><em>Aims</em> Our objective was to determine the effects of irrigation schedule on grain yield, water use efficiency (<em>WUE</em>), and accumulation and distribution of dry matter in winter wheat (<em>Triticum aestivum</em>) &lsquo;Lingkang-2&rsquo; in the arid Hexi corridor of Northwest China.<br><em>Methods</em> Based on pre-winter irrigation quota of 180 mm, we set up five irrigation treatments, i.e., irrigation quota of 165 mm at the jointing stage (W1), irrigation quota of 120 mm at the jointing stage and 105 mm at the heading stage (W2), irrigation quota of 105 mm at the jointing, heading and grain filling stages, respectively (W3), irrigation quota of 75 mm at the jointing, heading and grain filling stages, respectively (W4), and irrigation quota of 105 mm at the jointing stage, 75 mm at the heading stage, and 45 mm at the grain filling stage (W5).<br><em>Important findings</em> Available soil water content (<em>AWC</em>) in the 0&ndash;150 cm layer across different irrigation treatments changed with wheat growth stages. The grain yield in both W3 and W4 treatments was obviously improved by higher leaf area index (<em>LAI</em>) and dry matter accumulation. Higher <em>AWC</em> was found in the W3 and W4 treatments, but there was no significant difference in the grain yield between the two treatments. Nevertheless, the highest water use efficiency (<em>WUE</em>) in the W4 treatment was associated with its higher value of growth index than those in the W1, W2 and W5 treatments. In contrast, <em>LAI</em> in the W1, W2 and W5 treatments quickly decreased after anthesis, corresponding to lower dry matter accumulation, shorter grain filling duration and fewer numbers of spike and lower 1000-grain weight. We also observed that drought stress after anthesis promoted dry matter translocation from vegetative organs to grains, with a complementary effect on grain yield occurring as drought stress increased. In the grain filling stage, drought stress stimulated average filling rate, but shortened the duration&nbsp;of grain filling. The duration of grain filling, effective period of grain filling, the value of increases in grain weight during effective period of grain filling, and the timing of the maximum filling rate were positively correlated with 1000-grain weight and grain yield of winter wheat (<em>p</em> < 0.05). In consideration of all results, winter wheat should be irrigated at 75 mm at the jointing, heading and filling stages to achieve reasonable water use efficiency and grain yield. Our findings may help with the decision makers by providing hydrological and ecological evidence in development of sustainable agriculture in arid regions.</p>

Techniques based on the use of double ridges and furrows mulched with plastic film is very effective for improving water use efficiency and maize (Zea mays L.) yields in semiarid areas. Little is known, however, about the impact of removing the plastic film mulch during the reproductive stage (RS), i.e., during the July to September rainy season. We therefore performed a field experiment to investigate the effects of removing the film mulch during the RS. Two treatments were evaluated: (i) plastic film mulch in place during all growing stages (FM), and (ii) plastic film removed at the silking stage (RM). Relative to the FM treatment, the RM treatment decreased the cumulative soil temperature by 33°C in 2010 and 45°C in 2011 during the RS, thereby delaying leaf senescence and increasing the rate of photosynthesis. Grain growth measurements showed that the RM treatment extended the grain filling period by 3 to 4 d, resulting in greater ear biomass production, kernel numbers, and kernel volume. The greater grain production under the RM treatment was attributed to increases in source capacity or sink strength. Overall, the grain yields achieved under the RM treatment were greater than those for the FM treatment by 0.9 Mg ha−1 in 2010 and 1.3 Mg ha−1 in 2011, with concomitant increases in biomass production and harvest index. It may therefore be desirable to replace conventional film mulching with the RM treatment in regions with semiarid monsoon climates that have sufficient rainfall during the RS of maize growth to permit good yields.