Effects of salt and nitrogen on physiological indices and carbon isotope discrimination of wheat cultivars in the northeast of Iran

In order to study the effects of different levels of salt stress and nitrogen(N) on physiological mechanisms,carbon isotope discrimination(△~(13)C),and yield of two wheat cultivars(cv.),a two-year field experiment was carried out during 2013-2015.The treatments included three levels of salt stress(1.3,5.2,and 10.5 dS m~(-1)),three levels of N(50,100,and 150 kg N ha~(-1)),and two wheat cultivars,Bam and Toos.Under salt stress,N application(100 and 150 kg N ha~(-1)) produced a significant effect on both cultivars with respect to physiological traits,i.e.,net photosynthetic rate(P_n),stomatal conductance(g_s),chlorophyll index(Cl),Na~+/K~+ratio as well as the grain yield(GY).The salt-tolerant and-sensitive cultivars exhibited the maximum values of physio-biochemical and yield attributes at 100 and 150 kg N ha~(-1),respectively.The results of △~(13)C showed a significant difference(P0.001) between wheat cultivars under the control and salt stress.According to our result,salt-tolerant cultivar Bam seems to be more efficient in terms of higher GY,P_n,g_s,Cl,and lower Na~+/K~+ratio as well as higher △~(13)C as compared with salt-sensitive cultivar Toos,under salt stress.Therefore,a significant positive correlation that observed between △~(13)C and GY,indicated that △~(13)C may be an effective index for indirect selection of yield potential in wheat under irrigation regimes with saline water.     

Heat stability of winter wheat depends on cultivars,timing and protective methods

Heat stress negatively affects wheat production in many regions of the world. At present, sensitivity to heat stress remains one of the least understood aspects of wheat genetics and breeding, and measures for preventing heat stress are understudied. In this study, we used three cultivars of winter wheat(GY2018, SL02-1 and SY20) to evaluate the effect of heat stress at different days after anthesis(DAA) on yield and quality. Heat stability of the cultivars were analyzed and evaluated for the effects of two kinds of regulators on wheat under heat stress conditions. Heat treatment at 7 DAA led to the most substantial reduction in yield while GY2018 had the best heat stability with respect to yield, and demonstrated the most positive effects on several quality traits including protein content, sedimentation volume and glutenin and gliadin contents. Heat treatment at 14 DAA had the least reduction in yield, while SY20 had the best heat stability with respect to yield and heat treatment had minimal effects on quality. Heat treatment at 21 DAA had only a limited effect on yield, while SL02-1 had the best heat stability with respect to yield, but it showed the most negative effects on quality. Stable time at 14 DAA and protein content at 21 DAA can be used as indicators for detecting the stability of quality under heat stress. Among the three studied cultivars, SY20 was the most sensitive to heat stress with the stable time decreasing from 26.4 to 9.1 min, a higher sedimentation volume at 7 DAA, and a lower γ-gliadin content which increased 2.4-fold under high-temperature treatment. The addition of various regulators had different effects: potassium dihydrogen phosphate(KDP) was more protective of yield with heat stress at 7 DAA, while Duntianbao(DTB) had better effects on quality with heat stress at 21 DAA.     

小麦灌浆期耐热性QTL定位分析

【目的】以普通小麦加倍单倍体（DH）群体（旱选10号×鲁麦14）的150个株系为材料,鉴定其灌浆期耐热相关生理性状及千粒重耐热指数,并进行QTL定位,以期发掘具有显著效应以及不同环境中稳定表达的主效QTL,为改良小麦耐热性提供理论依据及分子标记。【方法】运用基于混合线性模型的复合区间作图法,以耐热指数为耐热性指标,对DH群体在田间雨养和灌溉2种土壤水分条件下的耐热性进行QTL定位。【结果】2种土壤水分条件下共检测到12个控制不同性状耐热指数的加性效应QTL,对表型变异的贡献率范围为2.64%—11.41%,其中,9个QTL与环境存在互作效应,对耐热指数表型变异的贡献率为1.41%—4.66%;检测到17对上位性效应QTL,对表型变异的贡献率为2.45%—8.84%,其中,仅4对与环境有互作效应,对表型变异的贡献率为0.62%—2.32%。控制耐热性的QTL来自双亲,DH群体中有耐热性超亲的株系存在。【结论】评价小麦灌浆期的耐热性,千粒重耐热指数是最直接的指标,生理性状指标为耐热性鉴定的间接辅助指标,其中,旱地条件下选用旗叶相对含水量耐热指数作为间接指标较好,而灌溉条件下选用气冠温差耐热指数较好。染色体1B、2D、5A、5B、6A、6B和7A对灌浆期耐热性贡献较大。千粒重耐热指数和旗叶叶绿素含量耐热指数的遗传以加性效应为主,叶绿素荧光参数耐热指数和气冠温差耐热指数的遗传以上位性效应为主,而叶片相对含水量耐热指数的遗传加性效应与上位性效应都重要。     

Effects of Powdery Mildew on 1000-Kernel Weight,Crude Protein Content and Yield of Winter Wheat in Three Consecutive Growing Seasons

In order to clarify the impact posed by wheat powdery mildew (Blumeria graminis f. sp. tritici) on the yield and yield components in different epidemic seasons, field trials were conducted in three growing seasons, 2009–2010, 2010–2011 and 2011–2012, in Langfang City, Hebei Province, China. The relationships between 1000-kernel weight, crude protein content of grain and yield and disease index (DI), as well as area under disease progress curve (AUDPC) were studied. The models of the percentage of loss of 1000-kernel weight, crude protein content and yield were constructed using DI at critical point (CP) of growth stages (GS) and AUDPC in the three growing seasons, respectively. The CPs for estimating 1000-kernel weight, crude protein content of grain and yield of wheat caused by powdery mildew were GS 11.1, GS 10.5.3 and GS 10.5.3, respectively. Models based on DI at CP to estimate the percentage of loss of 1000-kernel weight, crude protein content of grain and yield were better than models based on AUDPC. And models of the percentage of loss of 1000-kernel weight, crude protein content and yield for 2011–2012 season were significant different from these for 2009–2010 and 2010–2011 seasons. These results indicated that besides powdery mildew, weather conditions also had influence on 1000-kernel weight, crude protein content of grain and yield loss of wheat when powdery mildew occurred.     

Effects of short-term heat stress on PSII and subsequent recovery for senescent leaves of Vitis vinifera L. cv. Red Globe

Heat stress occurs frequently in energy-saving sunlight greenhouses(ESSG) at the late growth stage. Three-year delayed cultivation(DC) of the Red Globe cultivar of Vitis vinifera L. was used to clarify the physiological mechanisms of short-term heat stress on PSII and subsequent recovery from heat stress. By November, the photosynthetic function had declined and the fall in transpiration rate(E) with heating time increased the possibility of heat damage. In July, the most obvious increase was in the relative variable fluorescence at J point at 40°C, and in November it changed to K point. The 5 min of heat treatment resulted in a significant increase of the relative variable fluorescence at 0.3 ms(W_k), and after 10 min of heat treatment, the number of reactive centres per excited cross section(RC/CS_o), probability that a trapped exciton moves an electron into the electron transport chain beyond Q_A–(at t=0)(Ψ_o) and quantum yield of electron transport at t=0(φ_(Eo)) decreased significantly(P0.05), suggesting that the reaction centre, donor and acceptor side of photosystem II(PSII) were all significantly inhibited(P0.05) and that the thermal stability of the photosynthetic mechanism was reduced. The inhibition of energy fluxes for senescent leaves in November was earlier and more pronounced than that for healthy leaves, which did not recover from heat stress of more than 15 min after 2 h recovery at room temperature.     

Cultivar selection can increase yield potential and resource use efficiency of spring maize to adapt to climate change in Northeast China

Northeast China (NEC) is one of the major maize production areas in China.Agro-climatic resources have obviously changed,which will seriously affect crop growth and development in this region.It is important to investigate the contribution of climate change adaptation measures to the yield and resource use efficiency to improve our understanding of how we can effectively ensure high yield and high efficiency in the future.In this study,we divided the study area into five accumulated temperature zones (ATZs) based on growing degree days (GDD).Based on the meteorological data,maize data (from agrometeorological stations) and the validated APSIM-Maize Model,we first investigated the spatial distributions and temporal trends of maize potential yield of actual planted cultivars,and revealed the radiation use efficiency (RUE) and heat resource use efficiency (HUE) from 1981 to 2017.Then according to the potential growing seasons and actual growing seasons,we identified the utilization percentages of radiation (P_R) resource and heat resource (P_H) for each ATZ under potential production from 1981 to 2017.Finally,we quantified the contributions of cultivar changings to yield,P_R and P_H of maize.The results showed that during the past 37 years,the estimated mean potential yield of actual planted cultivars was 13 649 kg ha~(–1),ranged from 11 205 to 15 257 kg ha~(–1),and increased by 140 kg ha~(–1) per decade.For potential production,the mean values of RUE and HUE for the actual planted maize cultivars were 1.22 g MJ~(–1) and 8.58 kg (℃ d)~(–1) ha~(–1).RUE showed an increasing tendency,while HUE showed a decreasing tendency.The lengths of the potential growing season and actual growing season were 158 and 123 d,and increased by 2 and 1 d per decade.P_R and P_H under potential production were 82 and 86%,respectively and showed a decreasing tendency during the past 37 years.This indicates that actual planted cultivars failed to make full use of climate resources.However,results from the adaptation assessments indicate that,adoption of cultivars with growing season increased by 2–11 d among ATZs caused increase in yield,P_R and P_H of 0.6–1.7%,1.1–7.6% and 1.5–8.9%,respectively.Therefore,introduction of cultivars with longer growing season can effectively increase the radiation and heat utilization percentages and potential yield.     

高温胁迫下15 个茶花品种的耐热性

以茶花Camellia 3 个主要品种群的15 个品种为材料, 利用生理生化测定及SPSS 统计分析对其耐热性进行了研究。结果表明:持续7 d 36 ～ 38 ℃的高温胁迫能够有效区分不同茶花品种耐热性;生理生化测定结果的系统聚类与主成分分析能够对不同茶花品种的耐热性进行有效评价。云南山茶Camellia reticalata 及其杂种品种群耐热性较差, 茶梅C .sasanqua 耐热性较强, 而红山茶C .japonica 品种群耐热性变化范围较大。茶花品种耐热性与花型相关性不大。图1 表4 参15     

Canopy morphological changes and water use efficiency in winter wheat under different irrigation treatments

Water is a key limiting factor in agriculture. Water resource shortages have become a serious threat to global food security. The development of water-saving irrigation techniques based on crop requirements is an important strategy to resolve water scarcity in arid and semi-arid regions. In this study, field experiments with winter wheat were performed at Wuqiao Experiment Station, China Agricultural University in two growing seasons in 2013–2015 to help develop such techniques. Three irrigation treatments were tested: no-irrigation(i.e., no water applied after sowing), limited-irrigation(i.e., 60 mm of water applied at jointing), and sufficient-irrigation(i.e., a total of 180 mm of water applied with 60 mm at turning green, jointing and anthesis stages, respectively). Leaf area index(LAI), light transmittance(LT), leaf angle(LA), transpiration rate(Tr), specific leaf weight, water use efficiency(WUE), and grain yield of winter wheat were measured. The highest WUE of wheat in the irrigated treatments was found under limited-irrigation and grain yield was only reduced by a small amount in this treatment compared to the sufficient irrigation treatment. The LAI and LA of wheat plants was lower under limited irrigation than sufficient irrigation, but canopy LT was greater. Moreover, the specific leaf weight of winter wheat was significantly lower under sufficient than limited irrigation conditions, while the leaf Tr was significantly higher. Correlation analysis showed that the increased LAI was associated with an increase in the leaf Tr, but the specific leaf weight had the opposite relationship with transpiration. Optimum WUE occurred over a reasonable range in leaf Tr. In conclusion, reduced irrigation can optimize wheat canopies and regulate water consumption, with only small reductions in final yield, ultimately leading to higher wheat WUE and water saving in arid and semi-arid regions.     

关于小麦育种若干问题的探讨

回顾了近年来小麦育种工作的进展,并提出了今后小麦育种的目标和途径。小麦育种目标的制定应该包含4个方面:丰产性,稳产性,品质和生产成本。丰产性的实现要依赖生物学产量和经济系数的提高,可以通过繁茂性和粒叶比的选择来实现。目前我国品质改良的工作重点仍是提高面筋强度,应加强高分子量谷蛋白优质亚基和谷蛋白大聚体含量的选择,耐热性也是黄淮麦区品质改良的重要内容。稳产性的提高应增强品种的抗旱和耐热性能,水旱轮选是选育抗旱品种行之有效的方法,而细胞膜稳定性和气-冠温差在组织和群体水平上较好地反映了植物耐热性的差异,可用于耐热品种的选择。     

Relations Between Photosynthetic Parameters and Seed Yields of Adzuki Bean Cultivars (Vigna angularis

The study comparatively examined the leaf photosynthetic capacities of different adzuki bean cultivars, high-yield 2000-75 and Jihong 9218, and low-yield Hongbao 1 and Wanxuan 1 from flowering to ripening. It showed that after flowering, the leaves of the cultivars gradually aged, the leaf chlorophyll (Chl.), soluble protein (SP) contents, net photosynthetic rates (P_n), transpiration rates (T_r) and stomatal conductance (G_s) of the cultivars tended to decline, but the leaf intercellular CO₂ concentration (C_i) of the cultivars tended to rise. The leaf photosynthetic capacities of the cultivars decreased gradually from the lower to the upper nodes. The dry seed yields of the cultivars were positively correlated with their leaf Chl., SP, P_n, and T_r and G_s, and negatively associated with their leaf C_i. At the late growth stages, the high-yield cultivars maintained higher leaf Chl. contents, SP contents, P_n, T_r, and G_s than the low-yield cultivars, indicating that leaf photosynthetic capacity was one of important yield-affecting factors of adzuki bean. Therefore, it was important for a crop at the crucial stage of yield formation to maintain a high leaf chlorophyll content and a high leaf photosynthetic capacity and delay leaf aging.     

Reactive oxygen species are involved in cell death in wheat roots against powdery mildew

Inoculation of wheat(Triticum aestivum L.) leaves with wheat powdery mildew fungus(Blumeria graminis f. sp. tritici) induces the cell death in adventitious roots. Reactive oxygen species(ROS) play a key role in respond to biotic stress in plants. To study the involvement of ROS and the degree of cell death in the wheat roots following inoculation, ROS levels and microstructure of root cells were analyzed in two wheat cultivars that are susceptible(Huamai 8) and resistant(Shenmai 8) to powdery mildew fungus. At 18 d after powdery mildew fungus inoculation, only Huamai 8 displayed the leaf lesions, while root cell death occurred in both varieties. Huamai 8 had a high level of ROS accumulation, which is associated with increased root cell degradation, while in Shenmai 8, there was little ROS accumulation correlating with slight root cell degradation. The molecular study about the expression levels of ROS scavenging genes(MnSOD and CAT) in wheat roots showed that these genes expression decreased after the leaves of wheat was inoculated. The difference between Huamai 8 and Shenmai 8 on subcellular localization of H2 O2 and O2–· was corresponded with the different down-regulation of the genes encoding for superoxide dismutase and catalase in two wheat cultivars. These results suggested that ROS were involved in the process by which powdery mildew fungus induced cell death in wheat roots.     

Identifying the limiting factors driving the winter wheat yield gap on smallholder farms by agronomic diagnosis in North China Plain

North China Plain(NCP) is the primary winter wheat production region in China, characterized by smallholder farming systems. Whereas the winter wheat average yield of smallholder farmers is currently low, the yield potential and limiting factors driving the current yield gap remain unclear. Therefore, increasing the wheat yield in NCP is essential for the national food security. This study monitored wheat yield, management practices and soil nutrient data in 132 farmers' fields of Xushui County, Baoding City, Hebei Province during 2014–2016. These data were analyzed using variance and path analysis to determine the yield gap and the contribution of yield components(i.e., spikes per hectare, grain number per spike and 1 000-grain weight) to wheat yield. Then, the limiting factors of yield components and the optimizing strategies were identified by a boundary line approach. The results showed that the attainable potential yield for winter wheat was 10 514 kg ha~(–1). The yield gaps varied strongly between three yield groups(i.e., high, middle and low), which were divided by yield level and contained 44 farmers in each group, and amounted to 2 493, 1 636 and 814 kg ha~(–1), respectively. For the three yield components, only spikes per hectare was significantly different(P0.01) among the three yield groups. For all 132 farmers' fields, correlation between yield and spikes per hectare(r=0.51, P0.01), was significantly positive, while correlations with grain number per spike(r=–0.16) and 1 000-grain weight(r=–0.10) were not significant. The path analysis also showed that the spikes per hectare of winter wheat were the most important component to the wheat yield. Boundary line analysis showed that seeding date was the most limiting factor of spikes per hectare with the highest contribution rate(26.7%), followed by basal N input(22.1%) and seeding rate(14.5%), which indicated that management factors in the seeding step were the most important for affecting spikes per hectare. For desired spikes per hectare(6.598×10~6 ha~(–1)),the seeding rate should range from 210–300 kg ha~(–1), seeding date should range from 3th to 8th October, and basal N input should range from 90~(–1)80 kg ha~(–1). Compared to these reasonable ranges of management measures, most of the farmers' practices were not suitable, and both lower and higher levels of management existed. It is concluded that the strategies for optimizing yield components could be achieved by improving wheat seeding quality and optimizing farmers' nutrient management practices in the NCP.     

Evaluation of drought indices to identify tolerant genotypes in common bean bush(Phaseolus vulgaris L.)

Drought is one of the major abiotic stresses often causing negative impacts on bean crops in the Andean region in Colombia. An experiment under the greenhouse conditions was carried out to assess the effect of a prolonged drought period(15 days) at two different phenological stages(vegetative or reproductive) on grain yield and yield components of five bush bean cultivars(ICA-Cerinza, Bachue, NUA35, Bianca, and Bacatá). Nine tolerance indices including stress susceptibility index(SSI), tolerance(TOL), mean productivity(MP), geometric mean productivity(GMP), stress tolerance index(STI), yield stability index(YSI), yield index(YI), Harmonic mean(HM), and drought sensitivity index(DSI) were calculated based on grain yield under non-stressed(YP) and drought(YS) conditions. Based on the different drought indices, genotypes ICA-Cerinza and NUA35 had the best performance under drought conditions in both studied phases, which reflected in a reduction of grain yield ～≤40%. The biplot analysis also showed a clear superiority of these two genotypes at both phenological stages. Results also showed that SSI was more effective to identify genotypes less affected by drought. The above results allowed us to conclude that ICA-Cerinza and NUA35 may be considered for agricultural areas where long periods of water deficit are expected and can be used in breeding programs for drought tolerance.     

小麦耐热性的生理遗传研究进展

小麦是中国第二大口粮作物,其产量直接关系人民的生活水平,所以高产和稳产一直是中国小麦的首要育种目标。小麦起源于温带,属喜凉作物,生长季节内的高温对生长发育会产生不利影响,使其产量下降,品质变劣。由于耐热性是复杂的数量遗传性状,其机制的解析一直是生物学研究难点,也是研究热点。为了解析小麦耐热的生理遗传学及分子生物学基础,国内外研究人员通过正向遗传学方法,构建遗传分离群体,以冠层温度、灌浆持续时间、细胞膜稳定性和叶绿素含量等生理学参数,以及穗粒数和千粒重热感指数为指标,在小麦不同染色体上定位了多个耐热相关的QTL位点。同时利用反向遗传学方法,特别是通过转录组、蛋白组和表观遗传组等组学方法鉴定了大量的高温胁迫响应的基因、mi RNA及长片段非编码RNA,并通过转基因等手段证明了部分候选基因在小麦抵御高温胁迫中的重要作用。另外,虽然植物中高温受体至今尚未发现,但是钙离子信号通道以及ABA和SA等激素在高温信号传导中的作用也逐渐引起人们的关注。文中主要综述了现阶段高温对小麦产量品质及生理性状的影响、小麦耐热相关QTL的定位,以及小麦响应高温胁迫的转录组、蛋白组和表观遗传组的研究进展;提出应针对小麦种质资源进行系统的耐热性评价,筛选优异等位基因、解析其分子遗传机理,通过创新再利用,为选育适合中国气候条件的耐热小麦品种提供新材料,实现品种耐热性与丰产性的统一。     

Geographic variation in the yield formation of single-season high-yielding hybrid rice in southern China

Environmental conditions greatly affect the growth of rice. To investigate the geographic differences in yield formation of single-season high-yielding hybrid rice in southern China, experiments were conducted in 2017 and 2018 in the upper and middle–lower reaches of the Yangtze River with 10–30 main locally planted high-yielding hybrid cultivars used as materials. Compared with rice planted in the middle–lower reaches of the Yangtze River, rice planted in the upper reaches has a longer tillering duration, higher accumulated temperature(≥10℃) during tillering period, but lower accumulated temperature and solar radiation from initial booting to maturity. Yield traits comparison between the upper and the middle–lower reaches of Yangtze River showed that the former had 48.1% more panicles per unit area while the latter had 46.4% more grains per panicle; the rice yield in the former was positively correlated with the seed setting rate and the dry matter accumulation before heading, while the latter was positively correlated with grains per panicle and dry matter accumulation from booting to maturity. Comparison of the same variety Tianyouhuazhan planted in different regions showed there was a significant positive correlation between panicle number and the duration of and accumulated temperature during the tillering period(r=0.982~(**), r=0.993~(**), respectively), and between grains per panicle and accumulated solar radiation during booting period(r=0.952~*). In the upper reaches of the Yangtze River, more than 90% of cultivars with an yield of greater than 11 t ha~(–1) had an effective panicle number of 250–340 m~(–2), and there was a significant negative correlation between seed setting rate and grains per panicle; therefore, the high-yielding rice production in these regions with a long effective tillering period(40 d) should choose varieties with moderate grains per panicle, adopt crop managements such as good fertilizer and water measures during vegetative growth period to ensure a certain number of effective panicles, and to increase the dry matter accumulation before heading. While in regions with a short effective tillering period(20 d) but good sunshine conditions during the reproductive growth period, such as the middle–lower reaches of the Yangtze River, high-yielding rice production should choose cultivars with large panicles, adopt good water and fertilizer managements during the reproductive growth period to ensure the formation of large panicles and the increase of dry matter accumulation after heading.     

Relationships between temperature-light meteorological factors and seedcotton biomass per boll at different boll positions

Cotton growth and development are determined and influenced by cultivars,meteorological conditions,and management practices.The objective of this study was to quantify the optimum of temperature-light meteorological factors for seedcotton biomass per boll with respect to boll positions.Field experiments were conducted using two cultivars of Kemian 1 and Sumian 15 with three planting dates of 25 April(mean daily temperature(MDT)was 28.0 and 25.4°C in 2010 and 2011,respectively),25 May(MDT was 22.5 and 21.2°C in 2010 and 2011,respectively),and 10 Jun(MDT was 18.7 and 17.9°C in 2010 and 2011,respectively),and under three shading levels(crop relative light rates(CRLR)were 100,80,and 60%)during 2010 and 2011 cotton boll development period(from anthesis to boll open stages).The main meteorological factors(temperature and light)affected seedcotton biomass per boll differently among different boll positions and cultivars.Mean daily radiation(MDR)affected seedcotton biomass per boll at all boll positions,except fruiting branch 2(FB_2)fruting node1(FN_1).However,its influence was less than temperature factors,especially growing degree-days(GDD).Optimum mean daily maximum temperature(MDT_(max))for seedcotton biomass per boll at FB_(11)FN_3 was 29.9–32.4°C,and the optimum MDR at aforementioned position was 15.8–17.5 MJ m~(–2).Definitely,these results can contribute to future cultural practices such as rational cultivars choice and distribution,simplifying field managements and mechanization to acquire more efficient and economical cotton management.     

Effect of low-nitrogen stress on photosynthesis and chlorophyll fluorescence characteristics of maize cultivars with different low-nitrogen tolerances

Nitrogen(N) is a critical element for plant growth and productivity that influences photosynthesis and chlorophyll fluorescence. We investigated the effect of low-N stress on leaf photosynthesis and chlorophyll fluorescence characteristics of maize cultivars with difference in tolerance to low N levels. The low-N tolerant cultivar ZH311 and low-N sensitive cultivar XY508 were used as the test materials. A field experiment(with three N levels: N0, 0 kg ha–1; N1, 150 kg ha–1; N2, 300 kg ha–1) in Jiyanyang, Sichuan Province, China, and a hydroponic experiment(with two N levels: CK, 4 mmol L–1; LN, 0.04 mmol L–1) in Chengdu, Sichuan Province, China were conducted. Low-N stress significantly decreased chlorophyll content and rapid light response curves of the maximum fluorescence under light(Fm′), fluorescence instable state(Fs), non-photochemical quenching(qN), the maximum efficiency of PSII photochemistry under dark-adaption(Fv/Fm), potential activity of PSII(Fv/Fo), and actual photochemical efficiency of PSII(ΦPSII) of leaves. Further, it increased the chlorophyll(Chl) a/Chl b values and so on. The light compensation point of ZH311 decreased, while that of XY508 increased. The degree of variation of these indices in low-N tolerant cultivars was lower than that in low-N sensitive cultivars, especially at the seedling stage. Maize could increase Chl a/Chl b, apparent quantum yield and light saturation point to adapt to N stress. Compared to low-N sensitive cultivars, low-N tolerant cultivars maintained a higher net photosynthetic rate and electron transport rate to maintain stronger PSII activity, which further promoted the ability to harvest and transfer light. This might be a photosynthetic mechanism by which low-N tolerant cultivar adapt to low-N stress.     

Identification of yellow rust in wheat using in-situ spectral reflectance measurements and airborne hyperspectral imaging

The aim of this study was to evaluate the accuracy of the spectro-optical, photochemical reflectance index (PRI) for quantifying the disease index (DI) of yellow rust (Biotroph Puccinia striiformis) in wheat (Triticum aestivum L.), and its applicability in the detection of the disease using hyperspectral imagery. Over two successive seasons, canopy reflectance spectra and disease index (DI) were measured five times during the growth of wheat plants (3 varieties) infected with varying amounts of yellow rust. Airborne hyperspectral images of the field site were also acquired in the second season. The PRI exhibited a significant, negative, linear, relationship with DI in the first season (r ² = 0.91, n = 64), which was insensitive to both variety and stage of crop development from Zadoks stage 3–9. Application of the PRI regression equation to measured spectral data in the second season yielded a coefficient of determination of r ² = 0.97 (n = 80). Application of the same PRI regression equation to airborne hyperspectral imagery in the second season also yielded a coefficient of determination of DI of r ² = 0.91 (n = 120). The results show clearly the potential of PRI for quantifying yellow rust levels in winter wheat, and as the basis for developing a proximal, or airborne/spaceborne imaging sensor of yellow rust in fields of winter wheat.     

Wheat growth,photosynthesis and physiological characteristics under different soil Zn levels

In recent years,heavy metal hazards in the soil have seriously affected agricultural production.This study aims to examine the effects of different levels of heavy metal Zn on the growth,photosynthesis and physiological characteristics of wheat,and provide a theoretical basis for the diagnosis and control of heavy metal pollution in agricultural production.The field test method was used to explore the changes of wheat agronomic traits,photosynthetic capacity,chlorophyll fluorescence parameters,s...