CaCl2和水杨酸对昼间亚高温胁迫下番茄叶片光合作用的影响

以"辽园多丽"番茄品种(Lycopersicon esculentum Mill.)为试材,在第1花序第1花开花当天进行昼间亚高温(35℃)胁迫处理,并喷施10 mmol/L CaCl2和0.2 mmol/L水杨酸(SA)水溶液.以25℃喷施清水为对照,研究叶片净光合速率,叶绿素荧光参数和保护酶活性(SOD和POD)的变化情况,探讨CaCI2和水杨酸对番茄耐哑高温特性的调控作用.结果表明,亚高温胁迫处理使叶片净光合速率下降,气孔导度和胞间CO2浓度略有升高,PSII最大光化学效率(Fv/Fm)和电子传递速率(ETR)降低,说明不是气孔因素导致光合速率的下降.而亚高温条件下喷施10 mmol/L的CaCI2和0.2 mrnol/L的SA可以显著提高净光合速率、保护酶活性和PSII最大光化学效率.在处理结束时,使这些指标达到或超过对照水平.CaCI2主要是通过提高气孔的开放程度和防止光合机构的破坏来提高光合速率的,而水杨酸主要是通过改善光合机构的性能提高光合速率的.     

超级杂交稻两优培九高产的光合特性及其生理基础

超级杂交稻两优培九(培矮64S/9311)是中国超级稻计划完成第一步目标的标志性品种,与其亲本籼稻9311和之前大面积种植的当家杂交籼稻汕优63相比,具有明显的产量超亲优势和竞争优势,近15年来累计种植面积遥居杂交稻首位。两优培九稻谷产量高的生物学基础是源于优良光合特性而获得较高的生物学产量,因此,研究其光合特性及其生理基础,有助于了解高产杂交稻生长优势的光合特征和利用探索性育种技术提高水稻光合性能,为杂交稻超高产育种和栽培提供理论基础和技术途径。多年较系统的研究发现,与9311和汕优63相比,两优培九在正常生长和衰老过程中,光能吸收、传递和转化效率及碳同化等方面均具有优势,Pn较高,光合性能优异。表现在对强光和弱光、UV-B辐射增强的适应性或耐受能力及抗衰老能力更强;具有多种抵御偏低或过高温度的策略,对不良温度的适应性或耐受能力更强;水分亏缺造成的伤害较轻;光合速率随施用氮肥量的增加而提高,低氮或高氮条件下,均具有光合能力的比较优势;光合作用对大气CO_2浓度升高、土壤pH、盐胁迫等环境条件的适应能力更强。两优培九优异的光合性能与其光合机构和酶学基础有关,表现为叶绿体类囊体膜基粒数多、片层高而长、垛叠密集;叶绿素含量高,出现衰老特征晚,生育后期叶绿体衰败、叶绿素分解速度较慢;具有更高的Rubisco初始羧化活性、总羧化活性和活化率;C4光合途径酶活性较高,在低光强下仍有较高的碳同化效率,CO_2补偿点和光呼吸活性均较低;叶片的SOD、POD等抗氧化酶含量和活性均高,内源O2.-、H_2O_2含量低,抗膜脂过氧化能力较强。笔者认为,高产杂交稻育种要做到"遗传上有性状杂种优势,形态上有优良光合株型,功能上有优异光合性能"的遗传、形态和功能"三优"相结合;探究两优培九C4特性与高光合性能的联系和研究新的更高产杂交稻的光合特性,有助于加深对高产杂交稻光合生长优势的理解和探索针对性技术促进C4光合功能等,从而进一步提高光合生产以至于稻谷产量。     

适宜氮水平下冬油菜苗期不同叶位叶片光合氮分配特征

【目的】探讨适宜氮水平下冬油菜苗期不同叶位叶片的光合速率及其内部光合氮素利用特征,并分析氮素营养影响光合氮利用效率的限制因子,为合理施用氮肥提供理论依据。【方法】采用田间试验,设置4个施氮水平(0、45、180和360 kg·hm~(-2),分别用N_0、N_(45)、N_(180)和N_(360)表示),测定苗期干物质积累及成熟期产量。选取N_0(对照)和N_(180)(适宜氮水平)处理,将植株绿叶从上而下平均分为上部、中部和下部,测定不同叶位叶片最大净光合速率(P_n max)、氮含量(N_A)、叶绿素含量(Cc)以及可溶性蛋白氮含量(N_S)等相关生理、光合参数,并计算叶片氮素在光合组织系统(羧化系统、生物力能学组分和捕光系统)的分配比例,分析叶片氮素利用特征。【结果】施氮对冬油菜增产效果显著,N_(45)、N_(180)和N_(360)较N_0处理增产幅度分别达170.0%、505.6%和604.1%,其中,N_(180)与N_(360)处理产量差异不显著;苗期干物质积累与产量表现一致。与N_0处理相比,N_(180)处理冬油菜不同叶位叶片N_A、Cc和P_n max均显著升高,上部和中部叶片光合氮利用效率(P_NUE)有所下降。光合组织系统氮分配结果表明,N_(180)处理上部、中部叶片,氮素在光合组织系统中羧化系统(P_C)、生物力能学组分(P_B)及捕光系统(P_L)的分配比例均低于N_0处理,但各组分氮含量较N_0处理平均增加幅度分别达到20.6%、11.8%和28.8%。施氮与否对相同叶位叶片可溶性蛋白氮(N_S)与非可溶性蛋白氮(N_(non-S))的比例影响不大,但显著影响光合组织系统在N_S和N_(non-S)中的分配,其中N_0处理各部叶片的羧化系统氮含量(NC)占N_S的比例平均为83.4%,N_(180)处理比例为60.3%。基于边界线分析法定量各光合组织系统分配对P_NUE的影响结果表明,P_C和P_B对P_NUE的影响大小分别为26.8%和42.6%,显著高于P_L的影响。氮素营养对P_NUE的影响以P_C和P_B限制为主,平均所占比例达77.8%。上部叶P_NUE主要受P_C限制,所占比例达83.3%;而下部叶片P_NUE主要受P_B和P_L限制。【结论】施氮对冬油菜增产效果显著,施氮量为180 kg·hm~(-2)时较为适宜。缺氮条件下,植株将有限的氮尽可能地向光合器官中分配,且下部叶片光合氮素较早发生降解,而适宜氮水平下能维持光合蛋白在各自蛋白类型内的分配比例。氮素营养限制光合氮素利用效率提高的主要因子是羧化系统和生物力能学组分氮分配;随着叶位的降低光合氮素利用效率的主要限制因子由羧化系统氮分配逐渐转变为捕光系统及生物力能学组分氮分配。     

Irrigation mitigates the heat impacts on photosynthesis during grain filling in maize

Elevating soil water content (SWC) through irrigation was one of the simple mitigation measures to improve crop resilience to heat stress. The response of leaf function, such as photosynthetic capacity based on chlorophyll fluorescence during the mitigation, has received limited attention, especially in field conditions. A two-year field experiment with three treatments (control treatment (CK), high-temperature treatment (H), and high-temperature together with elevating SWC treatment (HW)) was carried out during grain filling with two maize hybrids at a typical station in North China Plain. Averagely, the net photosynthetic rate (P_n) was improved by 20%, and the canopy temperature decreased by 1–3°C in HW compared with in H in both years. Furthermore, the higher SWC in HW significantly improved the actual photosynthetic rate (Phi2), linear electron flow (LEF), variable fluorescence (F_v), and the maximal potential quantum efficiency (F_v/F_m) for both hybrids. Meanwhile, different responses in chlorophyll fluorescence between hybrids were also observed. The higher SWC in HW significantly improved thylakoid proton conductivity (gH⁺) and the maximal fluorescence (F_m) for the hybrid ZD958. For the hybrid XY335, the proton conductivity of chloroplast ATP synthase (vH⁺) and the minimal fluorescence (F_o) was increased by the SWC. The structural equation model (SEM) further showed that SWC had significantly positive relationships with P_n, LEF, and F_v/F_m. The elevating SWC alleviated heat stress with the delayed leaf senescence to prolong the effective period of photosynthesis and enhanced leaf photosynthetic capacity by improving Phi2, LEF, F_v, and F_v/F_m. This research demonstrates that elevating SWC through enhancing leaf photosynthesis during grain filling would be an important mitigation strategy for adapting to the warming climate in maize production.     

Nitrogen Deficiency Limited the Improvement of Photosynthesis in Maize by Elevated CO2 Under Drought

Global environmental change affects plant physiological and ecosystem processes. The interaction of elevated CO₂, drought and nitrogen (N) deficiency result in complex responses of C₄ species photosynthetic process that challenge our current understanding. An experiment of maize (Zea mays L.) involving CO₂ concentrations (380 or 750 µmol mol⁻¹, climate chamber), osmotic stresses (10% PEG-6000, −0.32 MPa) and nitrogen constraints (N deficiency treated since the 144th drought hour) was carried out to investigate its photosynthesis capacity and leaf nitrogen use efficiency. Elevated CO₂ could alleviate drought-induced photosynthetic limitation through increasing capacity of PEPC carboxylation (V_pmax) and decreasing stomatal limitations (SL). The N deficiency exacerbated drought-induced photosynthesis limitations in ambient CO₂. Elevated CO₂ partially alleviated the limitation induced by drought and N deficiency through improving the capacity of Rubisco carboxylation (V_max) and decreasing SL. Plants with N deficiency transported more N to their leaves at elevated CO₂, leading to a high photosynthetic nitrogen-use efficiency but low whole-plant nitrogen-use efficiency. The stress mitigation by elevated CO₂ under N deficiency conditions was not enough to improving plant N use efficiency and biomass accumulation. The study demonstrated that elevated CO₂ could alleviate drought-induced photosynthesis limitation, but the alleviation varied with N supplies.     

Effects of potassium deficiency on photosynthesis,chloroplast ultrastructure,ROS, and antioxidant activities in maize (Zea mays L.)

Potassium(K)deficiency significantly decreases photosynthesis due to leaf chlorosis induced by accumulation of reactive oxygen species(ROS).But,the physiological mechanism for adjusting antioxidative defense system to protect leaf function in maize(Zea mays L.)is unknown.In the present study,four maize inbred lines(K-tolerant,90-21-3 and 099;K-sensitive,D937 and 835)were used to analyze leaf photosynthesis,anatomical structure,chloroplast ultrastructure,ROS,and antioxidant activities.The results showed that the chlorophyll content,net photosynthetic rate(P_n),stomatal conductance(G_s),photochemical quenching(q_P),and electron transport rate of PSII(ETR)in 90-21-3 and 099 were higher than those in D937 and 835 under K deficiency treatment.Parameters of leaf anatomical structure in D937 that were significantly changed under K deficiency treatment include smaller thickness of leaf,lower epidermis cells,and vascular bundle area,whereas the vascular bundle area,xylem vessel number,and area in 90-21-3 were significantly larger or higher.D937 also had seriously damaged chloroplasts and PSII reaction centers along with increased superoxide anion(O_2~-·)and hydrogen peroxide(H_2O_2).Activities of antioxidants,like superoxide dismutase(SOD),catalase(CAT),and ascorbate peroxidase(APX),were significantly stimulated in 90-21-3 resulting in lower levels of O_2~-·and H_2O_2.These results indicated that the K-tolerant maize promoted antioxidant enzyme activities to maintain ROS homeostasis and suffered less oxidative damage on the photosynthetic apparatus,thereby maintaining regular photosynthesis under K deficiency stress.     

夜间低温对白菜型冬油菜光合机构的影响

【目的】探讨夜间低温对白菜型冬油菜叶片光合机构的影响机理及品种间差异。【方法】采用人工气候室内模拟夜间低温对白菜型冬油菜幼苗叶片气孔形态、叶绿体超微结构、光合特性及产物分配与积累的影响。【结果】昼/夜温度为20℃/10℃时,与弱抗寒品种天油2号相比,超强抗寒品种陇油7号生长点较低,株型匍匐,叶色深,叶绿素含量、胞间CO₂ 浓度（C_i）、叶片净光合速率（P_n）处于同一显著水平。当夜间温度降至5℃处理7 d后,不同抗寒品种气孔导度（G_s）、C_i、P_n下降,叶绿素含量、根/冠升高,表明低夜温下不同品种均有更多光合产物被优先输送到根部;天油2号叶片叶缘、叶尖呈卷曲状或水渍斑状,表现明显冻害症状,陇油7号叶色加深,叶片平展,生长点下陷,未见冻害;夜温降低处理后白菜型冬油菜叶片叶绿素均升高,不同品种叶绿素升高幅度明显不同,天油2号比对照升高6.0%,陇油7号升高9.6%;此时,天油2号大部分气孔关闭或半关闭,其叶片胞间C_i高于陇油7号,G_S、P_n显著低于陇油7号,表明在夜间温度为5℃时,天油2号光合作用受到显著抑制,非气孔限制是引起其光合效率降低的主要原因;而陇油7号在5℃低夜温条件下,叶片气孔大部分仍保持开放,叶片P_n、C_i虽略有下降,但与对照（昼夜温度为20℃/10℃）处于同一显著水平,在5℃低夜温条件下仍保持较高的光合能力。昼/夜温度为20℃/10℃时,白菜型冬油菜叶绿体紧贴细胞内壁整齐排列,基粒片层垛堞整齐紧密,基质片层整齐有序,叶绿体外形呈梭状或单面凹透镜形,内含淀粉颗粒,陇油7号淀粉粒数量和直径均大于天油2号;当昼/夜温度降为20℃/-5℃时,天油2号下部叶片已全部干枯,持绿叶片叶出现水渍状冻害,陇油7号心叶深绿色,下部叶变黄,但叶片平展,叶面呈块状泛红;天油2号相邻叶绿体融合、叶绿体外膜破裂、释放出內溶物,基粒溶解、基质片层断裂,叶绿体膜有序结构完全损坏;陇油7号叶绿体外膜完整清晰,保持部分基粒结构,基质片层结构较完整,其内仍有少量淀粉粒存在;-5℃低夜温处理后冬油菜不同品种C_i升高,叶绿素含量、G_s、P_n下降;但不同品种叶绿素含量、气体交换参数等存在显著差异,天油2号叶绿素含量显著低于陇油7号,其P_n迅速降低到0.210 μmol CO₂·m^-2·s^-1,比对照下降256.2%,陇油7号P_n为0.434 μmolCO₂·m^-2·s^-1,是天油2号的2.06倍,在-5℃低夜温处理后陇油7号仍有较高的光合速率;陇油7号根/冠显著高于天油2号,表明陇油7号更多光合物质被优先输送到根部保存。【结论】低夜温造成白菜型冬油菜叶绿体光合膜结构损伤,引起叶片P_n降低,昼/夜温度为20℃/5℃时,P_n的下降主要与气孔限制相关,而昼/夜温度为20℃/-5℃时,P_n下降主要由非气孔限制引起。     

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.     

Evaluating the efficacy of an attenuated Streptococcus equi ssp. zooepidemicus vaccine produced by multi-gene deletion in pathogenicity island SeseCisland_4

Streptococcus equi ssp. zooepidemicus(SEZ) is a pathogen associated with a wild range of animal species. Frequent outbreaks have occurred in recent years in pigs, horses, goats and dogs which is liable to infect humans. There is a lack of efficient vaccines against this disease and the occurrence of antibiotic resistance may render drug therapies ineffective. In this study, gene deletion mutant(ΔSEZ) in pathogenicity islands SeseCisland_4 was constructed. The mutant ΔSEZ had a 52-fold decrease in 50% lethal dose(LD_(50)) and had less capacity to adhere epithelial cells. Importantly, immunization of mice with attenuated vaccine ΔSEZ at the dose of 10~2 colony-forming units(CFU) mL~(–1) elicited a significant humoral antibody response, with an antibody titer of 1:12 800. Therefore, 10~2 CFU mL~(–1) might be used as the appropriate immune dose for the attenuated vaccine ΔSEZ, which provided mice with efficient protection against virulent SEZ. In addition, the hyperimmune sera against 10~2 CFU m L–1 attenuated vaccine ΔSEZ could confer significant protection against virulent SEZ infection in the passive immunization experiment and exhibited efficient bactericidal activity in the whole blood assay. Meanwhile, no viable bacteria was detected in blood when mice were immunized with ΔSEZ at the dose of 10~2 CFU mL~(–1) via hypodermic injection. Thereafter, the mutant ΔSEZ at the dose of 10~2 CFU mL~(–1) could confer significant protection in mice and had less negative effects on host, which could be an effective attenuated vaccine candidate for the prevention of SEZ.     

低温胁迫时间对4种幼苗生理生化及光合特性的影响

以盐肤木(Rhus chinensis)、假连翘(Duranta repens)、老鸭嘴(Thunbergia erecta)和葛藤(Pueraria lobata)4种幼苗为试验材料,研究了人工模拟下的低温胁迫环境(6 ℃)对幼苗叶片生理生化及光合特性的影响。结果表明:(1) 随低温胁迫的延长,假连翘幼苗的叶绿素含量先升后降,其余3种幼苗持续下降,低温解除后均显著回升;4种幼苗的脯氨酸含量持续上升或波动;葛藤幼苗的可溶性蛋白质含量先升后降,其余幼苗显著上升, 且低温解除后有所增加;4种幼苗叶片可溶性糖含量以及丙二醛含量呈增加趋势,SOD活性持续上升或先升后降。低温解除后,盐肤木幼苗的SOD活性略有上升,其余幼苗显著下降。(2) 随低温胁迫的延长,4种幼苗的净光合速率(P_n)、气孔导度(G_s)、蒸腾速率(T_r)均持续下降,假连翘的胞间CO₂浓度(C_i)持续上升,其余幼苗先降后升。低温解除后4种幼苗叶片P_n、G_s、T_r均有不同程度的回升,C_i有不同程度的下降。低温胁迫和恢复48 h期间,4种幼苗的脯氨酸、可溶性糖、可溶性蛋白质含量的增加和SOD活性的稳定或增加,减轻了幼苗叶片细胞的膜脂过氧化程度, 维持了细胞膜的完整性,是幼苗对低温胁迫适应性反应的重要调节机制。恢复48 h时的P_n、G_s和Tr均有不同程度的回升,C_i有不同程度的下降,说明4种幼苗有一定的抗寒能力。(3)用主成分分析法分别对生理生化指标和光合生理指标进行分析,均得出4种幼苗的抗寒性顺序为葛藤>盐肤木>老鸭嘴>假连翘,这一结果可为采矿石废弃地生态恢复的植物筛选提供科学依据。     

4种金色叶树木对SO2胁迫的生理响应

近年来 SO₂污染比较严重,它对植物有着多方面的影响。因此,越来越多的学者开始关注这方面的问题。彩叶植物在丰富园林景观及降低环境污染方面占用重要的地位,它们也被认为是净化城市空气最有效的途径之一。 旨在阐明4种彩叶树种耐SO₂污染机制,对丰富植物耐SO₂研究的理论、科学评价植物抗SO₂污染能力以及指导园林绿化科学选择树种等具有重要理论和现实意义。研究采用人工模拟熏气的方法对金叶女贞、金叶莸、金叶风箱果和金叶红瑞木4种金色叶树种的2年生苗木进行不同浓度的 SO₂ 胁迫,研究了参试树种的外观受害症状及膜脂过氧化、渗透调节物质、保护酶活性等生理指标对 SO₂ 的反应,并采用模糊数学隶属函数法和灰色关联度法对其抗SO₂能力进行了综合评价。结果表明: 4种金色叶植物对 SO₂ 均具有一定的净化能力,表现为随着 SO₂ 浓度的增加膜透性增大,丙二醛、脯氨酸、可溶性糖和硫含量增加,超氧化物歧化酶、过氧化物酶以及过氧化氢酶活性上升,叶绿素含量先增后降,叶液 pH 值下降。但4种金色叶树木对 SO₂ 的净化能力有差别,其中金叶红瑞木的净化能力强最大,金叶女贞和金叶风箱果的净化能力为中等,而金叶莸的净化能力最差。这与其含硫量的顺序一致,却与其对SO₂的抗性大小即金叶女贞> 金叶莸> 金叶红瑞木>金叶风箱果完全不同,说明这四种植物对 SO₂ 的吸收能力与其对该气体的抗性不完全一致。但这不能表明抗性差的树种在兰州地区不能应用,因为,兰州市空气中的SO₂实际污染程度与研究所设置的最低浓度相比仍属安全浓度。在所选的10个指标中,丙二醛含量、细胞膜透性、超氧化物歧化酶活性、过氧化氢酶活性、脯氨酸、过氧化物酶活性、叶绿素和可溶性糖等指标均可作为金色叶植物对 SO₂ 抗性的重要鉴定指标,而S含量和叶液 pH 值在评价植物对SO₂抗性能力时并不具有重要性。4种植物的受害程度与其SO₂抗性相反,说明受害症状可以作为判断其对SO₂抗性大小依据。     

Physiological and Biochemical Changes of IrlVHA-c gene Transgenic Tobacco Seedlings and Self-crossed Progeny Under NaHCO3 Stress

In order to study the alkali resistivity of VHA-c in Iris lacteal. (IrlVHA-c), the transgenic tobacco seedlings harboring IrlVHA-c gene from Iris lactea (T0), the self-crossed progeny (T1), and the non-transgenic lines of tobacco seedlings were grown in Hoagland nutrient solutions supplemented with 0, 100, 200, 300, 400 mmol·L-1 NaHCO3 . The MDA content, CAT, POD and SOD activity, electrical conductivity, chlorophyll content, soluble sugar content, proline content and polyphenol oxidase activity of the seedlings were determined. The results showed that the transgenic lines of tobacco maintained a high activity up to 200 mmol·L-1 NaHCO3 , and activity was slightly lower at 300 mmol·L-1 NaHCO3 . When the concentration of NaHCO3 was as high as 400 mmol·L-1 the seedlings were badly hurt. In addition, the activity of T0 and T1 transgentic tobacoo was maintained more or less. While the non-transgenic lines of tobacco could maintain viably up to 100 mmol·L-1 NaHCO3 , and they could not survive at 400 mmol·L-1 NaHCO3 . The conclusion was drawn that the alkali resistance of the tobacoo transformed IrlVHA-c was noticeably improved.     

UV-A诱导大豆芽苗菜下胚轴中花青苷积累的分子机理

【目的】研究长波紫外光（UV-A）、白光（W）和蓝光（B）对大豆芽苗菜下胚轴中花青苷含量、花青苷合成相关酶活性、花青苷合成途径相关基因及光受体基因表达量的影响,以探明UV-A诱导大豆芽苗菜下胚轴中花青苷生物合成的分子机理,为光质调控技术应用于大豆芽苗菜工业化生产提供理论依据。【方法】以大豆‘东农690’为试材,以黑暗培养为对照,连续的UV-A、白光（W）和蓝光（B）光照培养作为试验处理,在处理0 h、12 h、24 h和36 h后各采样一次,分别测定花青苷含量,苯丙氨酸解氨酶（PAL）、查尔酮异构酶（CHI）以及类黄酮半乳糖苷转移酶（UFGT）活性,相关基因（PAL、CHS、CHI、DFR、ANS、UFGT、MYB75、CRY1、CRY2、UVR8）表达量。花青苷含量采用分光光度法测定,苯丙氨酸解氨酶（PAL）及查尔酮异构酶（CHI）活性采用分光光度法测定,类黄酮半乳糖苷转移酶（UFGT）活性采用超高效液相色谱法（UPLC）测定。材料总RNA采用Trizol试剂法提取,基因表达量采用qRT-PCR测定。【结果】黑暗培养下的大豆芽苗菜子叶为黄色,而白光（W）、蓝光（B）和UV-A培养下的大豆芽苗菜子叶为绿色。与黑暗培养及其他光质处理相比,UV-A显著提高大豆芽苗菜下胚轴中花青苷含量;随着处理时间的延长,花青苷积累逐渐增加。0 h处理下,大豆芽苗菜下胚轴中花青苷含量较低,约2 U·g^-1FW。经36 h的UV-A处理,大豆芽苗菜下胚轴中花青苷含量达到最大值（43 U·g^-1FW）,显著高于黑暗及其他光照处理。0 h处理下,PAL和CHI酶活性较高。与黑暗培养及其他光质处理相比,24 h及36 h UV-A处理显著提高了PAL酶活性;12 h及24 h UV-A处理显著提高了UFGT酶活性。0 h处理下,不同处理间的花青苷合成相关基因表达均无差异。与黑暗培养及其他光质处理相比, UV-A处理36 h显著上调了MYB75、CRY1、CRY2及UVR8的表达,分别上调约12倍、30倍、6倍和2倍;UV-A处理12 h显著上调了花青苷合成相关结构基因（PAL、CHS、CHI、DFR、ANS、UFGT）的表达,分别上调约5倍、58倍、10倍、6倍、44倍和47倍。【结论】UV-A通过提高PAL、UFGT酶活性及上调花青苷合成和光受体相关基因的表达,诱导了大豆芽苗菜下胚轴中花青苷的积累。     

The positive function of selenium supplementation on reducing nitrate accumulation in hydroponic lettuce (Lactuca sativa L.)

High nitrate(NO_3~- ) in vegetables, especially in leaf vegetables poses threaten to human health. Selenium(Se) is an important element for maintaining human health, and exogenous Se application during vegetable and crop production is an effective way to prevent Se deficiency in human bodies. Exogenous Se shows positive function on plant growth and nutrition uptake under abiotic and/or biotic stresses. However, the influence of exogenous Se on NO_3~- accumulation in hydroponic vegetables is still not clear. In the present study, hydroponic lettuce plants were subjected to six different concentrations(0, 0.1, 0.5, 5, 10 and 50 μmol L–1) of Se as Na2 Se O3. The effects of Se on NO_3~- content, plant growth, and photosynthetic capacity of lettuce(Lactuca sativa L.) were investigated. The results showed that exogenous Se positively decreased NO_3~- content and this effect was concentration-dependent. The lowest NO_3~- content was obtained under 0.5 μmol L–1 Se treatment. The application of Se enhanced photosynthetic capacity by increasing the photosynthesis rate(Pn), stomatal conductance(Cs) and the transpiration efficiency(Tr) of lettuce. The transportation and assimilation of NO_3~- and activities of nitrogen metabolism enzymes in lettuce were also analysed. The NO_3~- efflux in the lettuce roots was markedly increased, but the efflux of NO_3~- from the root to the shoot was decreased after treated with exogenous Se. Moreover, Se application stimulated NO_3~- assimilation by enhancing nitrate reductase(NR), nitrite reductase(Ni R), glutamine synthetase(GS) and glutamate synthase enzyme(GOGAT) activities. These results provide direct evidence that exogenous Se shows positive function on decreasing NO_3~- accumulation via regulating the transport and enhancing activities of nitrogen metabolism enzyme in lettuce. We suggested that 0.5 μmol L–1 Se can be used to reduce NO_3~- content and increase hydroponic lettuce yield.     

硼调控干旱胁迫下马铃薯生长发育及抗性的生理机制

为了探讨叶面喷施硼（Na₂B₄O₇·10H₂O溶液）对马铃薯植株在干旱胁迫下生长发育及抗性的影响及其生理机制,在甘肃省景泰县条山集团马铃薯种植基地,对中度干旱和轻度干旱处理的两垄地,每隔3 m进行一个硼浓度（Na₂B₄O₇·10H₂O）喷施处理,浓度依次为0、10、20、30、40、60 g·L^-1,每个浓度（3 m长）的喷施量为166.7 ml。结果表明：叶面喷施硼相对增加了干旱胁迫下马铃薯的块茎产量及生物量,使干旱胁迫下叶片含水量和色素含量下降幅度减小;叶面喷施硼还从整体上表现为抗氧化酶活性的提高,并抑制了超氧阴离子产生速率的增加。通过去花与不去花植株生长发育的比较,发现去花后马铃薯植株地上部分重和地下部分重均有所下降,但施硼相对提高了块茎产量及地下部分重。可见,叶面喷施硼能促进马铃薯植株在干旱胁迫下的生长发育,提高其抗旱性及块茎产量,且这种变化可能与其促进光合产物向地下部分输送密切相关。     

Enzymatic activity and chlorophyll fluorescence imaging of maize seedlings (Zea mays L.) after exposure to low doses of chlorsulfuron and cadmium

The aim of this research was to study the influence of chlorsulfuron residue and cadmium on the enzymatic activity and photosynthetic apparatus of maize(Zea mays L.) plants. Chlorsulfuron and cadmium at 0.001 and 5.0 mg kg–1, respectively, were mixed and applied to soil prior to planting. The levels of chlorsulfuron-and cadmium-induced stress to plants were estimated by growth, chlorophyll content, lipid peroxide content, enzyme activities, and major fluorescence parameters of chlorophyll(revealed by the fluorescence imaging system Fluor Cam). Chlorsulfuron negatively affected the chlorophyll content, photochemical efficiency of photosystem II in the dark-adapted state, the maximum efficiency of photosystem II, photochemical quenching coefficient, and steady-state fluorescence decline ratio in the leaves of maize seedlings. However, cadmium did not produce noticeable changes. Plants that were exposed to both chlorsulfuron and cadmium showed an obvious increase in the steady-state fluorescence decline ratio. These results implied that the seedlings possessed more resistance to cadmium than to chlorsulfuron and their resistance to chlorsulfuron toxicity was enhanced by the presence of cadmium. The results also suggested that chlorophyll fluorescence imaging reveals overall alterations within the leaves but may not reflect small-scale effects on tissues, as numeric values of specific parameters are averages of the data collected from the whole leaf.     

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.     

Increasing photosynthetic performance and post-silking N uptake by moderate decreasing leaf source of maize under high planting density

To date,little attention has been paid to the effects of leaf source reduction on photosynthetic matter production,root function and post-silking N uptake characteristics at different planting densities.In a 2-year field experiment,Xianyu 335,a widely released hybrid in China,was planted at 60 000 plants ha~(–1 )(conventional planting density,CD) and 90 000 plants ha~(–1) (high planting density,HD),respectively.Until all the filaments protruded from the ear,at which point the plants were subjected to the removal of 1/2 (T1),1/3 (T2) and 1/4 (T3) each leaf length per plant,no leaf removal served as the control(CK).We evaluated the leaf source reduction on canopy photosynthetic matter production and N accumulation of different planting densities.Under CD,decreasing leaf source markedly decreased photosynthetic rate (P_n),effective quantum yield of photosystem II (ΦPSII) and the maximal efficiency of photosystem II photochemistry (F_v/F_m) at grain filling stage,reduced post-silking dry matter accumulation,harvest index (HI),and the yield.Compared with the CK,the 2-year average yields of T1,T2 and T3 treatments decreased by 35.4,23.8 and 8.3%,respectively.Meanwhile,decreasing leaf source reduced the root bleeding sap intensity,the content of soluble sugar in the bleeding sap,post-silking N uptake,and N accumulation in grain.The grain N accumulation in T1,T2 and T3 decreased by 26.7,16.5 and 12.8% compared with CK,respectively.Under HD,compared to other treatments,excising T3 markedly improved the leaf P_n,ΦPSII and F_v/F_m at late-grain filling stage,increased the post-silking dry matter accumulation,HI and the grain yield.The yield of T3 was 9.2,35.7 and 20.1% higher than that of CK,T1 and T2 on average,respectively.The T3 treatment also increased the root bleeding sap intensity,the content of soluble sugar in the bleeding sap and post-silking N uptake and N accumulation in grain.Compared with CK,T1 and T2 treatments,the grain N accumulation in T3 increased by 13.1,40.9 and 25.2% on average,respectively.In addition,under the same source reduction treatment,the maize yield of HD was significantly higher than that of CD.Therefore,planting density should be increased in maize production for higher grain yield.Under HD,moderate decreasing leaf source improved photosynthetic performance and increased the post-silking dry matter accumulation and HI,and thus the grain yield.In addition,the improvement of photosynthetic performance improved the root function and promoted postsilking N uptake,which led to the increase of N accumulation in grain.