Effects of Root-Zone Temperature on Growth,Chlorophyll Fluorescence Characteristics and Chlorophyll Content of Greenhouse Pepper Plants Grown under Cold Stress in Southern China

In Southern China, plants are usually exposed to cold stress during winter in an unheated greenhouse, but due to the high energy consumption and costs, most of the greenhouses remain unheated. In an attempt to find a simple and affordable solution to this problem, this study was undertaken. In this research, Capsicum frutescens L. plants were studied to investigate the effect of different root zone temperatures on its growth and chlorophyll fluorescence characteristics under cold stress. The plants were cultivated under cold stress conditions in a root zone temperature (RZT) control system where the roots were subjected to four different root-zone temperature treatments of 20°C-T20, 25°C-T25, 45°C-T45 and a control CK group. Growth characteristics studied included plant height, stem diameter, plant width, root length, biomass accumulation. Whilst fluorescence characteristics investigated were chlorophyll fluorescence ratio F_v/F_m, photochemical quenching (qL), efficiency of Photosystem II (Y[II]) and electron transport rate (ETR). Chlorophyll content in the leaves of the plants was also investigated. The findings demonstrated that plants in the CK group suffered a detrimental effect on the growth characteristics registering the lowest values in the measured variables. Conversely, the highest values were observed in T25 RZT treatment. In fluorescence characteristics, values of F_v/F_m were maintained at between 0.8 and 0.83 but also suffered a photo-inhibitory depression in CK and T45 RZT treatments to F_v/F_m values of <0.79. This depicted that root zone heating protected the PS II of these plants from photoinactivation induced by cold stress. Similar trends were seen in the qL, Y[II], ETR values with the T20 and T25 treatments registering the highest values. Chlorophyll content was significantly higher in the leaves of the plants in the T20 and T25 group. The lowest chlorophyll content was recorded in the CK group. Plants in all the treatments accumulated more biomass in the shoot than in the roots as depicted by a significantly lower shoot to root ratio values with the exception of those in the CK group. The findings of this study suggest that pepper plants can successfully be grown in an unheated greenhouse in the Yangtze River Delta area of Southern China during winter by heating the root zone of the plants to a RZT value of 25°C, thereby providing a simple, affordable and cost-effective technique.     

Evaluation of Chlorophyll Content and Fluorescence Parameters as Indicators of Drought Tolerance in Barley

Drought is a major abiotic stress that severely affects food production worldwide. Agronomic and physiological traits associated with drought tolerance are suitable indicators for selection of drought tolerance genotypes to reduce the impact of water deficit on crop yield in breeding program. The objective of this study was to identify indicators related to drought tolerance through analysis of photosynthetic traits in barley （Hordeum vulgare L.）. These traits included chlorophyll content, initial fluorescence （Fo）, maximum primary yield of photochemistry of photosystem Ⅱ （Fv /Fo） and maximum quantum yield of photosystem Ⅱ （Fv/Fm）. Four genotypes （Tadmor, Arta, Morocco9-75 and WI2291） variable in drought tolerance were used to investigate the correlation between these traits and drought tolerance. The results reflected that all of these traits were affected negatively in the four genotypes at different levels of post-anthesis drought stress, but the decrease in drought tolerant genotypes was much less than that of drought sensitive genotypes. The results further revealed that the components of the photosynthetic apparatus could be damaged significantly in drought sensitive genotypes, while drought tolerant genotypes were relatively less affected. On the other hand, the values of chlorophyll content, Fo, Fv/Fo and Fv/Fm in drought tolerance genotypes were significantly higher than those in drought sensitive genotypes under drought stress. It was concluded that chlorophyll content, Fo, Fv/Fo and Fv/Fm could be considered as reliable indicators in screening barley germplasm for drought tolerance.     

Beneficial effects of silicon on photosynthesis of tomato seedlings under water stress

Silicon can improve drought tolerance of plants,but the mechanism still remains unclear.Previous studies have mainly concentrated on silicon-accumulating plants,whereas less work has been conducted in silicon-excluding plants,such as tomato(Solanum lycopersicum L.).In this study,we investigated the effects of exogenous silicon(2.5 mmol L~(–1))on the chlorophyll fluorescence and expression of photosynthesis-related genes in tomato seedlings(Zhongza 9)under water stress induced by 10%(w/v)polyethylene glycol(PEG-6000).The results showed that under water stress,the growth of shoot and root was inhibited,and the chlorophyll and carotenoid concentrations were decreased,while silicon addition improved the plant growth and increased the concentrations of chlorophyll and carotenoid.Under water sterss,chlorophyll fluorescence parameters such as PSII maximum photochemical efficiency(F_v/F_m),effective quantum efficiency,actual photochemical quantum efficiency(Ф_(PSII)),photosynthetic electron transport rate(ETR),and photochemical quenching coefficient(q_P)were decreased;while these changes were reversed in the presence of added silicon.The expressions of some photosynthesis-related genes including PetE,PetF,PsbP,PsbQ,PsbW,and Psb28 were down-regulated under water stress,and exogenous Si could partially up-regulate their expressions.These results suggest that silicon plays a role in the alleviation of water stress by modulating some photosynthesis-related genes and regulating the photochemical process,and thus promoting photosynthesis.     

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.     

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.     

外源亚精胺对高温胁迫下生姜叶片内源激素及叶绿体超微结构的影响

【目的】生姜具喜温怕热的特性,生产中极易遭受高温伤害。本文旨在通过研究高温胁迫条件下外源亚精胺（Spd）与内源激素的关系,以及对叶绿体的保护作用,探讨外源Spd缓解生姜高温胁迫的生理机制。【方法】以砂培莱芜大姜为试材,置光周期12 h/12 h、昼夜温度28℃/18℃和38℃/28℃的光照培养箱内,分别采用0.5 mmol·L^-1Spd处理生姜根系,在处理后0、5、10、15和20 d时测定功能叶片的相对含水量、叶绿素含量、MDA含量、电解质渗透率、叶绿素荧光参数、活性氧（ROS）和内源激素代谢等相关指标,并于处理后第20 天观察叶绿体及类囊体超微结构。【结果】高温胁迫导致生姜叶片叶绿体和类囊体严重受损,叶绿素含量降低;随着高温胁迫时间的延长,叶片F_v/F_m、Ф_PSII、F_v′/F_m′、q_P和P持续降低,NPQ、β/α-1和D显著升高;主要表现为PSII反应中心的光化学活性降低,致使光能过剩,诱发 和H₂O₂大量积累,导致叶片MDA含量和电解质渗透率升高。高温胁迫下SOD活性、ABA含量和脯氨酸含量先升后降;APX活性、CTK含量和KT含量持续下降。外源添加Spd可恢复叶片相对含水量和叶绿素含量,降低MDA含量和电解质渗透率,维持叶绿体和类囊体结构的完整性,促使叶绿素荧光参数趋于正常水平,提高高温胁迫下抗氧化酶活性及内源激素水平,进而降低ROS水平,缓解高温对生姜幼苗产生的伤害。【结论】38℃/28℃的高温胁迫导致生姜叶片受损,叶绿体和PSII功能紊乱,活性氧和内源激素水平异常;外源添加0.5 mmol·L^-1Spd可降低高温胁迫下生姜叶片损伤程度,维护叶绿体的正常生理功能,维持内源激素的正常代谢,进而提高生姜植株的耐热性。     

油菜素内酯对阔世玛胁迫下谷子叶片光合荧光特性及糖代谢的影响

【目的】探明油菜素内酯(brassinolide,BR)对阔世玛胁迫下谷子叶片的光合荧光特性及糖代谢的影响,为谷子田磺酰脲类除草剂阔世玛的安全应用及利用植物生长调节剂油菜素内酯缓解除草剂药害提供理论基础和技术途径。【方法】采用完全随机设计,重复3次,以杂交高产谷张杂5号和普通优质谷晋谷21号为材料,进行盆栽试验,待幼苗长至3—5叶期时,喷施7.5 mg·L~(-1)阔世玛,药后1 d,分别叶面喷施清水(对照)、0.05、0.1、0.2和0.4 mg·L~(-1)的油菜素内酯,7 d后对所有处理的谷子幼苗株高、叶面积、鲜重等农艺性状、叶片光合色素含量、气体交换参数、叶绿素荧光参数、糖含量及蔗糖代谢关键酶活性进行测定与分析。【结果】在7.5 mg·L~(-1)阔世玛胁迫下,谷子的株高、叶面积、鲜重、叶绿素a、叶绿素b、类胡萝卜素、叶绿素(a+b)、净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、最大光化学产量(Fv/Fm)、表观光合电子传递速率(ETR)、非调节性能量耗散量子产量(Y(NO))、中性转化酶(NI)、蔗糖合成酶(SS)及蔗糖磷酸合成酶(SPS)活性显著降低;而胞间CO2浓度(Ci)、调节性能量耗散量子产量(Y(NPQ))、还原性糖、蔗糖和淀粉含量显著升高。药后1 d喷施适宜浓度的BR能部分缓解阔世玛对谷子的药害,显著提高谷子的株高、叶面积、鲜重、光合色素含量、Pn、Tr、Gs、Fv/Fm、ETR、Y(NO)、NI、SS及SPS活性,并显著降低Ci、Y(NPQ)、还原性糖、蔗糖和淀粉含量;其中,0.05—0.1 mg·L~(-1) BR对缓解张杂5号阔世玛药害的效果较好,0.1—0.2 mg·L~(-1) BR对缓解晋谷21号阔世玛药害的效果较好。≥0.4 mg·L~(-1) BR不能缓解阔世玛药害。【结论】7.5 mg·L~(-1)的阔世玛对谷子产生显著药害的原因之一是降低了其光合色素含量,抑制了PSⅡ光化学活性,影响了糖代谢的正常运转。0.1 mg·L~(-1)的油菜素内酯通过提高光合色素含量、增加气孔导度、提高PSⅡ光化学活性、促进碳水化合物的卸出、维持蔗糖代谢平衡等来缓解阔世玛对谷子光合作用的抑制。     

芦苇对阿特拉津胁迫的生理响应及其与耐受性的关系

为揭示阿特拉津胁迫下芦苇的生理响应规律及其与芦苇耐受性的关系,通过水培实验研究了阿特拉津对芦苇叶绿素含量、抗氧化酶(SOD和POD)活性和叶绿素荧光参数的影响,并以植物相对生长率为耐受性指标,利用逐步回归法分析了各生理指标与耐受性的关系。结果表明:≤8 mg·L~(-1)阿特拉津胁迫1周,芦苇虽可正常存活,但相对生长率受到显著抑制;胁迫2周时,生长停止;叶绿素a(Chla)和叶绿素b(Chlb)随处理浓度的增加而降低。POD活性胁迫1周时显著增强,胁迫2周时最低和最高浓度处理(0.5、8 mg·L~(-1))较1周时有所下降,与对照无显著差异;而SOD活性随处理浓度增加无显著变化。随处理浓度的增加,F_v/F_m和F_v/F_0显著降低,qN显著增加,而胁迫2周较1周时qN显著下降。研究表明,芦苇对阿特拉津比较敏感,但在短期内(1周)表现一定的耐受性,主要是通过增强非光化学淬灭能力来保护叶绿体,从而保持一定浓度的叶绿素来维持光合作用的物质基础,抵抗来自阿特拉津的胁迫。     

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.     

不同磷水平下雷竹幼苗叶绿素荧光特性

 为了解不同磷水平下雷竹Phyllostachys violascens幼苗叶片叶绿素荧光特性的变化,试验以无性繁殖的雷竹幼苗作为试验材料,采用砂培试验方法,研究了不同磷水平（0,0.5,5.0,50.0,500.0 mg·L^－1）对雷竹幼苗叶绿素荧光参数和光通量密度?鄄光合电子传递速率（P_AR-E_TR）响应曲线的影响。结果表明,随着磷质量浓度的升高,幼苗叶片潜在光化学活性（F_o /F_m）呈逐渐降低趋势,最大光化学效率（F_v /F_m）在0~50.0 mg·L^－1磷质量浓度范围内逐渐下降。磷质量浓度为5.0 mg·L^－1时,初始荧光（F_o）,最大荧光（F_m）,适时最小荧光（F_t）和可变荧光（F_v）均达到最大值,电子传递速率（E_TR）和光系统Ⅱ（PSⅡ）实际光化学效率（Y）较大,光化学猝灭系数（q_P）和非光化学猝灭系数（q_N和N_PQ）相对较低,说明在5.0 mg·L^-1磷质量浓度下,雷竹幼苗叶片的光合能力较强,接近适宜雷竹幼苗生长的磷质量浓度。磷质量浓度过高（50.0和500.0 mg·L^-1）均导致雷竹幼苗叶片E_TR下降,热耗散增加,光化学效率和光量子产额降低。图1表3参20     

Effects of sodium benzoate on growth and physiological characteristics of wheat seedlings under compound heavy metal stress

In this study, we investigated the effect of exogenous sodium benzoate on wheat seedlings(Yangmai 16) grown under heavy metal stress. The results showed that 2.4 mmol kg~(–1) of heavy metals significantly inhibited growth and delayed emergence of wheat seedlings. Under compound heavy metal stress, application of 2–4 g L~(–1) sodium benzoate significantly increased(P0.01) chlorophyll content and chlorophyll fluorescence parameters F_v/F_m and F_v/F_o of wheat, compared to the control(water treatment). Further analysis showed that application of 2–4 g L~(–1) sodium benzoate alleviated osmotic stress by promoting the accumulation of osmolytes such as soluble proteins and free proline, increased the activity of superoxide dismutase(SOD) and reduced malondialdehyde content(MDA). In contrast, higher concentrations of sodium benzoate solution(6 g L~(–1)) inhibited the growth of wheat seedlings and even caused damage to seedlings. Correlation analysis showed that when the sodium benzoate concentration was in the range of 1.97–3.12 g L~(–1)(2016) and 1.58–3.27 g L~(–1)(2017), values of chlorophyll and its components, root activity, SOD activity, soluble protein, and free proline content were the highest. When the sodium benzoate concentration was raised to 2.59 g L~(–1)(2016) or 3.02 g L~(–1)(2017), MDA content was the lowest. Ultimately, exogenous sodium benzoate(2–4 g L~(–1)) facilitates root development and improves the root activity of wheat seedlings grown under compound heavy metals stress, thereby effectively alleviating the damage of compound heavy metal stress in wheat seedlings.     

不同分子量的褐藻寡糖对黄瓜幼苗光合作用及生长的影响

应用不同分子量的褐藻寡糖(ADO)喷施在黄瓜幼苗叶片上,探索不同分子量的褐藻寡糖对黄瓜幼苗的生长情况以及生理特性的影响。结果表明:ADO促进黄瓜幼苗的生长,与对照相比,ADO处理过的幼苗株高、茎粗、株幅和鲜重均有显著增加,且ADO提高了黄瓜叶片中SOD和POD的活力,使得植物体内的氧自由基清除能力提升;ADO还提高叶片中的叶绿素的含量同时使得叶片中净光合速率(P_n)、气孔导度(G_s)、蒸腾速率(T_r)、胞间CO_2浓度(C_i)、叶绿素荧光参数F_v/F_m值均有显著提高。但是,不同分子量的ADO对黄瓜生长的促进效果存在差异,以分子量为8 000的褐藻寡糖处理的效果最好。     

Effects of aqueous leaf extracts of Populus tomentosa at different ages on the growth and photosynthetic characteristics of its own seedlings

Through the outdoor potted plant trials, the allelopathic potential of Populus tomentosa was tested against its species in the growth, chlorophyll content, and photosynthetic and chlorophyll fluorescence characteristics with aqueous extracts (0.01, 0.02, 0.05, and 0.1 g·mL⁻¹) obtained from leaves at different individual ages (1, 20, and 45 years old). The results showed that seedling height, basal diameter, fresh and dry weights, quantity of chlorophyll, the ratio of chlorophyll a/b, net photosynthetic rate (P _n ), stomatal conductance (G _s ), transpiration rate (T _r ), efficiency of primary conversion of light energy of PSII (F _v /F _m ), potential activity of PSII (F _v /F ₀), and photochemical quenching (q _P ) of the seedlings gradually decreased with the increase of extract concentration of all three ages when compared with the controls. The older the P. tomentosa used for extract preparation, the greater the percentage declined in the aforementioned parameters. Moreover, at the four concentrations used, there was a significant difference between treatments with the extracts from 1- and 45-year-old plants (except for q _P ), but occasionally, the effects were not obvious between the 1- and the 20-year-old plants, or the 20- and 45-year-old plants. The intercellular CO₂ concentration (C _i ) treated with the extracts from the 1-year-old decreased at the lowest concentration, whereas it increased at higher concentrations. The C _i treated with aqueous leaf extracts from the 20-year-old decreased at the lower concentrations and increased to similar levels to that of the control at the higher concentrations. C _i was always close to control levels in 45-year-old extract treatments. All the aqueous leaf extracts of P. tomentosa at all ages caused an increase of the initial fluorescence (F ₀ ). The older P. tomentosa used for the preparation of aqueous leaf extracts caused a greater percentage decline in F ₀ . The nonphotochemical quenching (q _N ) increased significantly at lower concentrations of all P. tomentosa extracts, whereas it decreased significantly at higher concentrations. It seemed that aqueous leaf extracts from P. tomentosa were harmful to the photosynthetic structure of its own seedlings, inhibited seedling growth, and led to an eventual decrease of biomass. Extracts from older P. tomentosa leaves had more negative effects on the seedling growth of poplar. The effects on photosynthesis are the more important mechanism of the allelopathy of poplar.     

干旱复水激发玉米叶片补偿效应的生理机制

采用盆栽控水试验,在旱后复水条件下,于苗期对2个不同抗旱性玉米品种叶片生理生化指标进行了测定,结果表明:干旱导致细胞膜结构破坏、叶绿素含量及光合作用下降,抗旱性强的品种变化较小;渗透调节物质和保护性酶活性增加,抗旱性强的品种升幅较大.复水后细胞膜结构迅速恢复,保护性酶活性和可溶性糖含量继续增加,叶绿素含量、光合速率、Fv/F0和Fv/Fm等光合作用参数出现超补偿现象.中度干旱10 d后复水激发了作物的生理补偿效应,主要生理机制是干旱复水后细胞膜结构迅速修复和叶绿素含量的超补偿增加,大大提高了光合作用的潜力和速率;前期干旱锻炼增强了玉米抗旱能力,抗旱品种表现出较高的超补偿效应,有利于适应干湿交替和低水多变的环境,实现节水高产.     

多噬伯克霍尔德氏菌WS-FJ9对杨树光合作用和生物量的影响

为研究Burkholderia multivorans WS-FJ9对杨树Populus的促生机制,采用LI-6400XT便携式光合仪对接菌后的杨树叶片的光合指标及荧光参数进行了测定,同时对杨树叶片的叶绿素质量分数及杨树的苗高、地径和生物量进行了测定。结果表明:在处理期内,接种WS-FJ9菌株处理的净光合速率(Pn),蒸腾速率(Tr)和气孔导度(Gs)均呈先上升后下降趋势,胞间二氧化碳摩尔分数(Ci)呈先下降后上升趋势,Pn和Tr在整个处理期均高于对照,Ci在整个处理期均低于对照,Gs在第30天时低于对照,其后均高于对照。荧光参数Fv/Fm和ΦPSⅡ值均高于对照;叶绿素总量及叶绿素a/b比值均高于对照;杨树实生苗接菌处理150 d后的苗高、地径和生物量均显著高于对照。研究结果从光合作用及生物量的角度阐明了WS-FJ9菌株对NL-895杨的促生机制,为生物菌肥的开发与利用提供了参考依据。     

壬基酚对四尾棚藻生长及群体形成的影响

选取水体中广泛存在的壬基酚为代表,研究其对四尾栅藻生理特性及群体形成的影响。实验设置6个暴露组(0.63、1.02、1.65、2.67、4.32和7.00 mg·L-1)和1个对照组(0 mg·L-1),测定了96 h内四尾栅藻细胞密度、叶绿素a含量、胞外多糖合成、最大光能转化效率(Fv/Fm)以及群体形态等变化。结果表明,四尾栅藻起始细胞密度6.64×105 cells·m L-1下,壬基酚对四尾栅藻细胞密度的EC50为2.05 mg·L-1;随着壬基酚质量浓度的提高,四尾栅藻的叶绿素a含量和Fv/Fm下降,四尾栅藻的生长受到抑制,但细胞胞外多糖含量增多,导致细胞间黏性增强,同时双细胞和多细胞(≥3个)群体占总细胞比例上升。     

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...     

Discrimination of corn,grasses and dicot weeds by their UV-induced fluorescence spectral signature

Real-time spot spraying of weed patches requires the development of sensors for the automatic detection of weeds within a crop. In this context, the potential of UV-induced fluorescence of green plants for corn-weed discrimination was evaluated. A total of 1 440 spectral signatures of fluorescence were recorded in a greenhouse from three plant groups (four corn hybrids, four dicotyledonous weed species and four monocotyledonous weed species) grown in a growth chamber. With multi-variate analysis, the full information contained in each spectrum was first reduced to the scores calculated from five principal components. Then, a linear discriminant analysis was applied on these scores to classify spectra on a species/hybrids basis and, subsequently, the resulting classes were aggregated according to the three plant groups. This two-step process minimized the error generated by heterogeneous groups such as dicotyledonous weeds. The output of this classification shows the significant potential of UV-induced fluorescence for plant group discrimination as the success rate reached 91.8%. No error was observed between corn and dicot weeds and most of the errors between corn and grasses came from confusion between the hybrid Pioneer 39Y85 and Setaria glauca L. (Beauv.). Analysis also determined that the position of the fluorescence sensor on the leaf and the plant age had negligible effects on the efficiency of fluorescence to discriminate plant groups. The factors to consider for transferring the results about UV-induced fluoro-sensing from laboratory to the field are discussed.     

甘蔗光合指标与抗旱性关系研究

 利用因子分析方法研究了甘蔗叶片净光合速率（P_n）、胞间CO₂浓度（C_i）、气孔导度（G_s）、蒸腾速率（T_r）、水分利用率（WUE）、PSⅡ原初光能转换效率（F_v/F_m）、PSⅡ潜在活性（F_v/F_o）等光合参数与抗旱性的关系。结果表明,通过因子分析将7个甘蔗光合性状指标用2个因子表示,累加方差贡献率达到87.6%。因子l主要是反映F_v/F_o,P_n,F_v/F_m,G_s,T_r对甘蔗品种抗旱性起支配作用;因子2中,C_i,WUE对甘蔗品种抗旱性起主导作用。甘蔗参试品种的因子分析结果与农艺性状基本一致,表明利用因子分析甘蔗光合性状指标是可行的。