Growth traits and nitrogen assimilation-associated physiological parameters of wheat(Triticum aestivum L.) under low and high N conditions

In this study, 14 wheat cultivars with contrasting yield and N use efficiency(NUE) were used to investigate the agronomic and NUE-related traits, and the N assimilation-associated enzyme activities under low and high N conditions. Under deficient-N, the cultivars with high N uptake efficiency(UpE) and high N utilization efficiency(UtE) exhibited higher plant biomass, yields, and N contents than those with medium and low NUEs. The high Up E cultivars accumulated more N than other NUE type cultivars. Under sufficient-N, the tested cultivars showed similar patterns in biomass, yield, and N content to those under deficient-N, but the varietal variations in above traits were smaller. In addition, the high Up E cultivars displayed much more of root biomass and larger of root length, surface area, and volume than other NUE type cultivars, indicating that the root morphological traits under N deprivation are closely associated with the plant biomass through its improvement of the N acquisition. The high Ut E cultivars showed higher activities of nitrate reductase(NR), nitrite reductase(NIR), and glutamine synthetase(GS) at stages of seediling, heading and filling than other NUE type cultivars under both low and high N conditions. Moreover, the high Up E and Ut E cultivars also displayed higher photosynthetic rate under deficient-N than the medium and low NUE cultivars. Together, our results indicated that the tested wheat cultivars possess dramatically genetic variations in biomass, yield, and NUE. The root morphological traits and the N assimilation enzymatic acitivities play critical roles in regulating N accumulation and internal N translocation under the N-starvation stress, respectively. They can be used as morphological and biochemical references for evaluation of Up E and Ut E in wheat.     

Tiller fertility is critical for improving grain yield,photosynthesis, and nitrogen efficiency in wheat

Genetic improvement has promoted wheat’s grain yield and nitrogen use efficiency (NUE) during the past decades. Therefore, the current wheat cultivars exhibit higher grain yield and NUE than previous cultivars in the Yangtze River Basin, China since the 2000s. However, the critical traits and mechanisms of the increased grain yield and NUE remain unknown. This study explores the mechanisms underlying these new cultivars’ increased grain yield and NUE by studying 21 local cultivars cultivated for three growing seasons from 2016 to 2019. Significantly positive correlations were observed between grain yield and NUE in the three years. The cultivars were grouped into high (HH), medium (MM), and low (LL) grain yield and NUE groups. The HH group exhibited significantly high grain yield and NUE. High grain yield was attributed to more effective ears by high tiller fertility and greater single-spike yield by increasing post-anthesis single-stem biomass. Compared to other groups, the HH group demonstrated a longer leaf stay-green ability and a greater flag leaf photosynthetic rate after anthesis. It also showed higher N accumulation at pre-anthesis, which contributed to increasing N accumulation per stem, including stem and leaf sheath, leaf blade, and unit leaf area at pre-anthesis, and promoting N uptake efficiency, the main contribution of high NUE. Moreover, tiller fertility was positively related to N accumulation per stem, N accumulation per unit leaf area, leaf stay-green ability, and flag leaf photosynthetic rate, which indicates that improving tiller fertility promoted N uptake, leaf N accumulation, and photosynthetic ability, thereby achieving synchronous improvements in grain yield and NUE. Therefore, tiller fertility is proposed as an important kernel indicator that can be used in the breeding and management of cultivars to improve agricultural efficiency and sustainability.     

秦冠、富士苹果杂交后代抗早期落叶病的遗传分析

采用秦冠、富士杂交F1代,对苹果早期落叶病的抗性遗传倾向进行研究。结果表明,杂交F1代斑点病的遗传倾向在不同年份表现一致,病情指数由小到大依次为秦冠×富士<富士×秦冠,而褐斑病的遗传倾向在不同组合不同年份表现不一致。秦冠、富士杂交F1代的斑点病病情指数均值略高于或低于亲中值,表明秦冠、富士杂交后代抗斑点病的遗传中加性效应较大,在后代中选择抗病单株潜力大。褐斑病病情指数均高于亲中值,表明褐斑病遗传中非加性效应占有较大比重。     

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.     

Precision phenotyping of contrasting potato(Solanum tuberosum L.) varieties in a novel aeroponics system for improving nitrogen use efficiency: In search of key traits and genes

With increasing population, degrading soil health, limited arable land area, and high cost of nitrogen(N) fertilizers, improving nitrogen use efficiency(NUE) of potato is an inevitable approach to save the environment and achieve sufficient tuber yields with less N fertilizer supply. Recently, we have developed an aeroponics system to study NUE in potato using genomics, physiology, and breeding approaches. This study aims on precision phenotyping of plants of two distinct potato varieties(Kufri Gaurav, N efficient; Kufri Jyoti, N inefficient) in the novel aeroponics system. Plants were grown in aeroponics under controlled conditions with low N(0.75 mmol L~(-1) NO_3~-) and high N(7.5 mmol L~(–1) NO_3~-) levels. Plant biomass, root traits, total chlorophyll content, and plant N were increased with increasing N supply, whereas higher NUE parameters namely NUE, agronomic NUE(Ag NUE), N uptake efficiency(NUp E), harvest index(HI), and N harvest index(NHI) were observed at low N. An NUE efficient cv. Kufri Gaurav showed higher tuber dry weight, fresh tuber yield, tuber number per plant, early start of tuber harvesting, root traits, stolon traits, NUE parameters, and higher amino acid(aspartic acid and asparagine) content at low N supply. Higher expression of nitrate reductase(NR), nitrite reductase(NIR), and asparagine synthetase(AS) genes was observed in the leaf tissues of Kufri Gaurav at high N. Thus, aeroponics-based precision phenotyping enables identification of NUE efficient genotypes based on key traits and genes involved in improving NUE in potato. Further, this study suggests that the potential of aeroponics can be utilized to investigate N biology in potato under different N regimes.     

谷子苗期氮高效品种筛选及相关特性分析

【目的】评价不同基因型谷子苗期氮素吸收利用差异性,筛选谷子氮高效利用基因型材料,为谷子氮高效利用品种选育和机理研究提供理论依据。【方法】采用沙培盆栽试验,以具有代表性生态类型的79个谷子品种为材料,分析其在低氮(0.2 mmol·L~(-1))和高氮(6 mmol·L~(-1))处理下茎叶干物重、含氮量、氮素吸收量、氮素吸收与利用效率的差异及相关性,并划分不同生态类型品种的氮效率类型。【结果】供试谷子品种在2个氮素水平条件下的茎叶干物重(CV_(N0.2) 35.39%和CV_(N6) 50.83%)、氮素含量(CV_(N0.2) 11.52%和CV_(N6) 11.22%)、氮素吸收量(CV_(N0.2) 32.82%和CV_(N6) 48.46%)、氮素吸收效率(CV_(N0.2) 32.82%和CV_(N6) 48.45%)、氮素利用效率(CV_(N0.2) 11.53%和CV_(N6) 11.27%)和氮效率(CV_(N0.2) 35.35%和CV_(N6) 50.61%)均存在较大差异。不同生态类型谷子品种的氮素吸收和利用效率差异显著,西北春谷类型氮素吸收效率的变化(CV_(N0.2) 39.99%和CV_(N6) 54.38%)显著高于华北夏谷类型(CV_(N0.2)29.31%和CV_(N6) 45.68%)和东北春谷类型(CV_(N0.2) 29.49%和CV_(N6) 40.30%),而氮素利用效率以华北夏谷类型品种间差异最大(CV_(N0.212.03%和CV_(N6) 12.70%)。茎叶干物重与氮素吸收和氮素利用效率呈极显著正相关(P0.01),相关系数分别为R~2_(N0.2)=0.1827**和R~2_(N6)=0.1027**及R~2_(N0.2)=0.8985**和R~2_(N6)=0.9442**;氮效率与氮素吸收量极显著正相关,与氮含量极显著负相关,相关系数分别为R~2_(N0.2)=0.8985**和R~2_(N6)=0.9442**及R~2_(N0.2)=0.1962**和R~2_(N6)=0.0998**;氮素利用效率与氮含量极显著负相关,相关系数分别为R~2_(N0.2)=0.9924**和R~2_(N6)=0.9910**。氮素吸收效率与氮素含量和氮素利用效率间无显著相关性。以两氮素水平条件下茎叶干物重和氮效率的平均值为标准,将3种生态类型的谷子品种划分为4种氮效率类型,双高效型、双低效型、高氮高效型和低氮高效型。其中,东北春谷双高效型和高氮高效型品种所占比重最高(P_(东北)52.9%P_(西北)36.0%P_(华北)29.7%和P_(东北)23.5%P_(华北)18.9%P_(西北)4.0%),双低效型比重最低(P_(东北)17.6%P_(华北)32.4%P_(西北)36.0%),而低氮高效型在西北春谷类型中所占比重最高(P_(西北)24.0%P_(华北)18.9%P_(东北)5.9%)。【结论】不同谷子品种苗期氮效率差异显著,且西北春谷类型品种间氮素吸收效率差异最大,华北夏谷类型品种间氮素利用效率差异最大;氮素吸收效率和利用效率之间无显著相关性,应作为2个独立的氮效率指标进行评价和改良。     

不同薏苡品种光合特性及其与氮素利用效率的关系

为明确薏苡品种的光合特性及与氮素利用效率间的关系。2015年早季和晚季,分别以从大田试验中筛选出来的氮素利用效率较高和较低品种各2个为材料进行盆栽试验,在分蘖期、抽穗期和成熟期测定功能叶片光合速率及叶绿素荧光参数,抽穗期测定顶部4片功能叶的光合速率,成熟期测定氮素积累量和氮素利用效率。结果表明,氮高效品种西林1号(XL)与黔饮1号(QL)早季和晚季成熟期单株氮素吸收量平均分别比氮低效品种隆林1号(LL)与品种10号(CU)高125.5%和96.0%,其氮素利用效率平均比品种LL与CU分别高出17.7%和18.0%,品种间差异显著。氮高效品种在分蘖期、抽穗期和成熟期功能叶片的光合速率和叶绿素含量均明显高于氮低效品种。同时,氮高效品种在分蘖期后的光合速率、叶绿素含量衰减速率比氮低效品种小。不同品种在分蘖期、抽穗期和成熟期功能叶片的叶绿素荧光参数及抽穗期顶部4片功能叶光合速率也存在一定的差异,但品种间的变化规律不明显。综上所述,氮高效薏苡品种各生育期功能叶片的光合速率和叶绿素含量较高,其中后期光合速率及叶绿素含量衰减较慢。薏苡品种氮素利用效率与功能叶片的叶绿素荧光参数及顶部4片功能叶光合速率的变化没有显著的相关关系。     

Improvement in winter wheat productivity through regulating PSⅡ photochemistry,photosynthesis and chlorophyll fluorescence under deficit irrigation conditions

Deficit irrigation is critical to global food production, particularly in arid and semi-arid regions with low precipitation. Given water shortage has threatened agricultural sustainability under the dry-land farming system in China, there is an urgent need to develop effective water-saving technologies. We carried out a field study under two cultivation techniques:(1) the ridge and furrow cultivation model(R); and(2) the conventional flat farming model(F), and three simulated precipitation level...     

Postponed and reduced basal nitrogen application improves nitrogen use efficiency and plant growth of winter wheat

Excessive nitrogen(N) fertilization with a high basal N ratio in wheat can result in lower N use efficiency(NUE) and has led to environmental problems in the Yangtze River Basin, China. However, wheat requires less N fertilizer at seedling growth stage, and its basal N fertilizer utilization efficiency is relatively low; therefore, reducing the N application rate at the seedling stage and postponing the N fertilization period may be effective for reducing N application and increasing wheat yield and NUE. A 4-year field experiment was conducted with two cultivars under four N rates(240 kg N ha–1(N240), 180 kg N ha–1(N180), 150 kg N ha–1(N150), and 0 kg N ha–1(N0)) and three basal N application stages(seeding(L0), fourleaf stage(L4), and six-leaf stage(L6)) to investigate the effects of reducing the basal N application rate and postponing the basal N fertilization period on grain yield, NUE, and N balance in a soil-wheat system. There was no significant difference in grain yield between the N180 L4 and N240 L0(control) treatments, and the maximum N recovery efficiency and N agronomy efficiency were observed in the N180 L4 treatment. Grain yield and NUE were the highest in the L4 treatment. The leaf area index, flag leaf photosynthesis rate, flag leaf nitrate reductase and glutamine synthase activities, dry matter accumulation, and N uptake post-jointing under N180 L4 did not differ significantly from those under N240 L0. Reduced N application decreased the inorganic N content in the 0–60-cm soil layer, and the inorganic N content of the L6 treatment was higher than those of the L0 and L4 treatments at the same N level. Surplus N was low under the reduced N rates and delayed basal N application treatments. Therefore, postponing and reducing basal N fertilization could maintain a high yield and improve NUE by improving the photosynthetic production capacity, promoting N uptake and assimilation, and reducing surplus N in soil-wheat systems.     

Screening of drought resistance indices and evaluation of drought resistance in cotton (Gossypium hirsutum L.)

Sixteen cotton cultivars widely planted in China were sowed under five different drought concentrations (0, 2.5, 5, 7.5, and 10%) using PEG₆₀₀₀ to screen the indices of drought resistance identification and explore the drought resistance of different cotton cultivars. Eighteen physiological indices including root, stem, and leaf water contents (RWC, SWC, and LWC), net photosynthetic rate (P_n), the maximum photochemical quantum yield (F_v/F_m), the actual photochemical quantum yield (ϕPSII), non-photochemical quenching coefficient (NPQ), leaf water potential (LWP), osmotic potential (ψs), leaf relative conductivity (REC), leaf proline content (Pro), leaf and root soluble protein contents (LSPC and RSPC), leaf and root malondialdehyde (MDA) contents (LMDA and RMDA), root superoxide dismutase, peroxidase, and catalase activities (RSOD, RPOD, and RCAT) were measured. Results indicated the 18 physiological indices can be converted into five or six independent comprehensive indices by principal component analysis, and nine typical indices (F_v/F_m, SWC, LWP, Pro, LMDA, RSPC, RMDA, RSOD, and RCAT) screened out by a stepwise regression method could be utilized to evaluate the drought resistance. Moreover, the 16 cotton cultivars were divided into four types: drought sensitive, drought weak sensitive, moderate drought resistant, and drought resistant types. The resistance ability of two selected cotton cultivars (drought resistant cultivar, Dexiamian 1; drought sensitive cultivar, Yuzaomian 9110) with contrasting drought sensitivities were further verified by pot experiment. Results showed that the responses of final cotton biomass, yield, and yield composition to drought were significantly different between the two cultivars. In conclusion, drought resistant cultivar Dexiamian 1 and drought sensitive cultivar Yuzaomian 9110 were screened through hydroponics experiment, which can be used as ideal experimental materials to study the mechanism of different cotton cultivars with contrasting drought sensitivities in response to drought stress.     

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.     

施肥水平对不同氮效率水稻氮素利用特征及产量的影响

【目的】研究不同施肥水平下不同氮效率杂交水稻产量差异与氮素吸收和利用的关系,以期为水稻品种改良和高产高效栽培技术提供依据。【方法】以氮高效品种(德香4103)和氮低效品种(宜香3724)为材料,通过设置低肥(75 kg N·hm~(-2),37.5 kg P_2O_5·hm~(-2),75 kg K_2O·hm~(-2),记为N_1P_1K_1)、中肥(150 kg N·hm~(-2),75 kg P_2O_5·hm~(-2),150 kg K_2O·hm~(-2),记为N_2P_2K_2)、高肥(225 kg N·hm~(-2),112.5 kg P_2O_5·hm~(-2),225 kg K_2O·hm~(-2),记为N_3P_3K_3)3种施肥水平,并在各施肥水平下均增设一不施氮处理,研究其对不同氮效率水稻产量和氮素利用效率的影响及其结实期氮素吸收、转运和分配特性。【结果】品种与施肥水平对杂交稻主要生育时期及各生育阶段氮素的累积、转运、分配,以及氮素利用特征和产量均存在显著影响;品种对氮肥回收利用率、千粒重,以及总颖花数的影响均不同程度的高于施肥水平的调控效应;施肥水平对主要生育时期及各生育阶段氮素的累积,结实期叶片和茎鞘氮的运转,以及产量调控作用显著。N_2P_2K_2相对于N_1P_1K_1处理能促进不同氮效率水稻主要生育时期及各生育阶段氮素的累积,提高氮收获指数,促进结实期叶片和茎鞘中氮素的运转,进而显著提高稻谷产量及氮肥利用效率,且N_2P_2K_2均显著高于同品种下其他的肥料施用处理,为本试验最佳的氮磷钾肥施用模式;N_3P_3K_3处理易造成结实期叶片及茎鞘中氮滞留量增加,氮转运贡献率显著降低,导致产量及氮肥利用效率显著降低。氮高效品种具有总颖花数、结实率高的特征,其主要生育时期氮素累积量,氮素干物质生产效率,氮素稻谷生产效率及氮素收获指数等均显著高于氮低效品种,但千粒重并不是氮高效品种所独有的特征;此外,氮高效品种结实期更有利于叶片与茎鞘氮素的运转及穗部氮素的累积,尤其氮高效品种具有较高的茎鞘氮素转运率,其与氮肥生理利用率、回收利用率及农艺利用率均存在显著正相关性(r=0.699*—0.743*),是导致不同氮效率品种氮肥利用效率、产量差异的重要因子,可作为氮效率及品种鉴选的评价指标,也可以以进一步提高抽穗至成熟期氮高效水稻品种茎鞘氮素运转率,作为实现水稻高产与氮高效利用协调统一的另一重要途径。【结论】本试验条件下,氮高效品种具备的结实期茎鞘高氮素转运、高总颖花数及结实率是优于氮低效品种而形成产量差异的主要因素,N_2P_2K2_为氮高效品种配套的最优氮磷钾肥施用模式。提高抽穗期至成熟期氮累积量,促进叶片与茎鞘氮运转量,尤其应提高茎鞘氮素运转率,可实现高产与氮高效利用的同步提高。     

Dynamic Changes in the Calcium Content of Several Apple Cultivars During the Growing Season

Dynamic changes in calcium content were investigated in eight apple cultivars. The results showed that the calcium concentration in leaves and shoots increased with fruit development. The cultivars displayed only a small difference in the calcium concentration during the early stage of development, the difference became very significant at the late stage of development, especially in shoots. In shoots, for example, calcium content was highest in Starkrimson （19 638.6 mg kg^-1） and lowest in Fuji （8 751.3 mg kg^-1）. Calcium concentration was highest in young fruits and was found to decrease with the growth of fruit, and was characterized by a dramatic drop at the rapid expansion stage. There was a significant difference among cultivars. Young Starkrimson fruits contained the highest calcium concentration of 506.52 mg kg^-1 among cultivars tested, followed by Pink Lady and Fuji. The calcium concentration in mature fruits from high to low is as follows： Starkrimson, Sansa, Pink Lady, Senshu, Gala, Fuji, Red General and New Century. In this study, it was found that eight cultivars continuously assimilated calcium during the whole growing season, especially at the young stage when fruit took up 35-46% of total calcium. The calcium content in fruitlets was low in all cultivars; in the expansion stage, there was rapid absorption of about 30% of total calcium, whereas in the ripening fruit, content of calcium was reduced. The calcium accumulation increased with fruit growth in stalk, similar to that in fruit.     

Characterization of low-N responses in maize(Zea mays L.) cultivars with contrasting nitrogen use efficiency in the North China Plain

Over-use of N fertilizer in crop production has resulted in a series of environmental problems in the North China Plain(NCP). Thus, improvement of nitrogen use efficiency(NUE) in summer maize has become an effective strategy for promoting sustainable agriculture in this region. Using twenty maize cultivars, plant dry matter production, N absorption and accumulation, yield formation, and NUE in summer maize were investigated under three N levels in two growing seasons. Based on their yield and yield components, these maize cultivars were categorized into four groups including efficient-efficient(EE) cultivars, high-nitrogen efficient(HNE) cultivars, low-nitrogen efficient(LNE) cultivars and nonefficient-nonefficient(NN) cultivars. In both two seasons, the EE cultivars improved grain yield together with increased plant biomass, and enhanced accumulative amounts as well as higher average grain yields than the other cultivar groups under deficient-N conditions. Significant correlations were observed between yield and kernel numbers(KN), dry matter(DM) amount and N accumulation at both post-silking and maturity stages. DM and N accumulation at late growth stage(i.e., from silking to maturity) contributed largely to the enhanced yield capacity and improved NUE under N-deficient conditions. Compared with the NN cultivars, the EE cultivars also showed increased N assimilation amount(NAA) and N remobilization content(NRC), and elevated N remobilization efficiency(NRE), NUE and nitrogen partial factor productivity(PFPN). Our investigation has revealed N-associated physiological processes and may provide guidance for cultivation and breeding of high yield and NUE summer maize under limited N conditions in the NCP.     

The mitigation effects of exogenous dopamine on low nitrogen stress in Malus hupehensis

Dopamine plays numerous physiological roles in plants. We explored its role in the regulation of growth, nutrient absorption, and response to nitrogen (N) deficiency in Malus hupehensis Rehd. Under low N condition, plant growth slowed, and the net photosynthetic rates, chlorophyll contents, and maximal quantum yield of PSII (F_v/F_m) decreased significantly. However, the application of 100 μmol L⁻¹ exogenous dopamine significantly reduced the inhibition of low N stress on plant growth. In addition to modifying root system architecture under low N supply, exogenous dopamine also changed the uptake, transport, and distribution of N, P, and K. Furthermore, exogenous dopamine enhances the tolerance to low nitrogen stress by increasing the activity of enzymes (nitrate reductase, nitrite reductase, glutamic acid synthase and glutamine synthetase) involved in N metabolism. We also found that exogenous dopamine promoted the expression of ethylene signaling genes (ERF1, ERF2, EIL1, ERS2, ETR1, and EIN4) under low N stress. Therefore, we hypothesized that ethylene might be involved in dopamine response to low N stress in M. hupehensis. Our results suggest that exogenous dopamine can mitigate low N stress by regulating the absorption of mineral nutrients, possibly through the regulation of the ethylene signaling pathway.     

覆草对苹果叶片显微结构及光系统功能的影响

【目的】探究渤海湾北部冷凉苹果产区,果园覆草管理措施对苹果叶片光合机构及生理功能的影响机制,为果园有机覆盖措施提供理论依据。【方法】以2年生‘寒富’苹果/GM256/山定子为试材,当地自然生长的马唐草(Digitaria sanguinalis(L.)Scop.)为覆盖材料,设覆草处理(1 kg草/盆,C1N0),施用氮肥处理(3.4g尿素/盆,C0N1),覆草+氮肥处理(1 kg草+3.4 g尿素/盆,C1N1)和对照(CK)4个处理,通过盆栽试验模拟果园覆草的土壤管理措施,研究覆盖草残体及配施氮肥各处理对苹果叶片的显微结构、光合色素含量、叶片气体交换参数及光合机构整体功能的影响。【结果】与对照相比,盆栽条件下覆草配施氮肥各处理对苹果叶片显微结构产生影响,其中单独覆草处理及施氮肥处理均可以增加栅栏组织的厚度和栅栏组织/海绵组织的比值,但两处理叶片的海绵组织厚度、叶片厚度与对照差异不显著;覆草+氮肥处理的苹果叶片栅栏组织厚度、海绵组织厚度和叶片厚度分别较对照增加8.45%、12.91%和19.34%,明显提高了叶片栅栏组织/海绵组织的比值。覆草处理可改变叶片的叶绿素含量、叶绿素组分比例和光合气体交换参数,其中叶绿素a含量、总叶绿素含量、叶绿素a/b和叶片净光合速率(Pn)分别提高22.67%、12.71%、23.42%和22.83%;施氮肥处理与覆草+氮肥处理的叶片光合色素含量和光合生理参数高于覆草处理及对照水平,后者的叶绿素a含量、叶绿素b含量和总叶绿素含量分别是对照的1.42、1.04和1.37倍,叶片的净光合速率(Pn)和水分利用效率(WUE)也分别较对照增加41.71%和21.99%。各处理叶片的叶绿素荧光诱导动力曲线和820 nm光吸收曲线出现较为明显变化,经JIP-test荧光数据分析表明,最大光化学效率(Fv/Fm)、捕获的激子将电子传递到电子传递链中QA下游其他电子受体的概率(ψo)和PSⅡ反应中心吸收的光能用于电子传递的量子产额(φEo)表现为C1N1C0N1C1N0CK,叶片光合性能指数(PIABS)、光系统Ⅰ(PSⅠ)最大氧化还原能力(ΔI/Io)也均高于对照水平。各处理均提高了苹果植株的生长发育水平,单独覆草处理的叶片长度与对照无显著差异,而施氮肥处理的叶片长度较对照增加10.63%,覆草处理及施氮肥处理均可明显增加叶片的宽度和叶片面积,苹果植株的干周也分别较对照增加8.82%和12.35%,覆草+氮肥处理的苹果植株叶片长度、叶片宽度、叶面积和干周则分别是对照的1.14、1.19、1.44和1.21倍。【结论】盆栽试验条件下,模拟果园覆草和施用氮肥复合处理可显著提高叶片光合效能,有效促进苹果树生长。     

Genome-wide identification and function analysis of the sucrose phosphate synthase MdSPS gene family in apple

Sucrose phosphate synthase(SPS) is a rate-limiting enzyme that works in conjunction with sucrose-6-phosphate phosphatase(SPP) for sucrose synthesis, and it plays an essential role in energy provisioning during growth and development in plants as well as improving fruit quality. However, studies on the systematic analysis and evolutionary pattern of the SPS gene family in apple are still lacking. In the present study, a total of seven MdSPS and four MdSPP genes were identified from the Malus dome...     

滴灌施肥水肥耦合对温室番茄产量、品质和水氮利用的影响

【目的】水肥是限制作物增产的两大因子,不合理的灌溉与施氮不仅难于增加产量,还会增加土壤剖面硝态氮累积、降低作物品质及水氮利用效率。针对西北半干旱地区温室蔬菜灌水和施肥存在的问题,通过滴灌施肥水肥耦合对温室番茄产量品质和水氮利用的影响,研究滴灌施肥条件下温室番茄高产优质高效的灌水施肥制度。【方法】通过温室番茄小区试验,设常规沟灌施肥（100%ET₀,N240-P₂O₅120-K₂O150 kg·hm^-2）以及3个滴灌水量（高水W₁：100%ET₀、中水W₂：75%ET₀、低水W₃：50%ET₀）和3个施肥水平（高肥F₁：N240-P₂O₅120-K₂O150 kg·hm^-2、中肥F₂：N180-P₂O₅90-K₂O112.5 kg·hm^-2、低肥F₃：N120-P₂O₅60-K₂O75 kg·hm^-2）,共10个处理,分析番茄生长产量、品质、土壤硝态氮分布以及水氮吸收利用对不同灌水量和施肥量的响应规律。【结果】与常规沟灌施肥相比,滴灌施肥增加番茄产量31.04 t·hm^-2、干物质量3 208 kg·hm^-2和总氮吸收量73.13 kg·hm^-2,增幅分别为46.9%、54.0%和82.4%,同时增加果实中维生素C（Vc）含量61.8%;降低土壤中硝态氮含量;水分利用效率（WUE）和氮肥利用率（NUE）分别增加46.4%和76.5%。滴灌施肥条件下,W₁F₂处理总干物质量最大（9 248 kg·hm^-2）,产量和植株氮素吸收量均与灌水量和施肥量正相关,增加施肥量带来的增产效应大于灌水,且W₁F₂处理产量和氮素吸收量增加幅度最大。增加灌水量,降低施肥量,WUE逐渐下降,NUE逐渐上升,W₃F₁处理WUE最大（47.7 kg·m^-3）,W₁F₃处理NUE最大（65.6%）,且W₃F₂处理的WUE和W₁F₂处理的NUE增加幅度明显大于其他处理。土壤中硝态氮含量受灌水、施肥以及水肥交互效应影响显著,随灌水量的增加呈先增大后降低的趋势,随施肥量的增加逐渐增大,在滴头正下方没有明显累积,在湿润土体的横向边缘产生累积,W₁F₂处理土壤中硝态氮含量较小,分布更均匀。增大灌水量显著降低番茄Vc、番茄红素和可溶性糖含量以及营养累积量;增大施肥量,品质含量以及营养累积量呈先增大后降低的趋势;W₃F₂处理获得最大的Vc和番茄红素含量及营养累积量,最大的可溶性糖含量及较大的营养累积量。【结论】温室番茄滴灌施肥技术能够达到高产优质和高效的目的,当追求产量和氮肥利用率时,高水中肥（W₁F₂：100%ET₀,N180-P₂O₅90-K₂O112.5 kg·hm^-2）处理能获得较高的产量和NUE以及较低的土壤硝态氮含量;当追求品质和水分利用效率时,低水中肥（W₃F₂：50%ET₀,N180-P₂O₅90-K₂O112.5 kg·hm^-2）处理获得最大的维生素C、可溶性糖和番茄红素含量以及较高的水分利用效率。     

甘蓝型油菜氮高效的生理与分子遗传基础研究进展

氮是植物生长发育所必需的大量营养元素。油菜对氮肥的需求量较大,氮肥利用率低。不同油菜品种的氮效率存在较大的基因型差异。与氮低效基因型油菜相比,氮高效基因型油菜在氮的吸收、转运、代谢、光合作用以及再利用等方面表现出显著的优势。同时,参与上述过程的基因包括硝酸根转运基因(NRT)、铵离子转运基因(AMT)、编码植物氮代谢相关酶类的基因以及其他基因等的表达水平也受到氮水平的显著影响,并在氮高、低效基因型间表现出显著的差异。本文主要从甘蓝型油菜氮效率的基因型差异、氮高效的生理与分子遗传基础等方面简要介绍了近年来关于甘蓝型油菜氮效率方面的研究进展。