Effects of Heat Stress during Seed Filling Stage on Brassica napus Seed Oil Accumulation and Chlorophyll Fluorescence Characteristics

As global temperature rise,the threat of heat stress to rapeseed production is becoming more obvious.Exploring the response characteristics of two important biological pathways,oil accumulation and photosynthesis,to heat stress during B.napus seed filling is helpful in the genetic improvement of heat-tolerant rapeseed.The effects of heat stress on seed oil accumulation and chlorophyll fluorescence characteristics of 29 B.napus germplasms with different oil content and environmental sensitivity,including 6 rapeseed varieties which exhibited environmentsensitive/insensitive and with high,medium or low oil content,were tested by whole plant heat stress or the in vitro silique culture system.Both assay exhibited similar trend on oil content of the rapeseed germplasms.The heat effect on the chlorophyll fluorescence kinetic parameters F_(v)/F_(m),ETR and Y(Ⅱ)were also consistent.Heat stress significantly decreased oil content,although there was abundant genetic variation on heat tolerance among the genotypes.Correlation analysis showed that the decrease rate of F_(v)/F_(m) of silique heat-stressed B.napus developing seed was positive correlative to the decrease rate of mature seed oil content of the whole plant heat-stressed rapeseed(R=0.9214,P-value<0.01).Overall,the results indicated that heat stress inhibited oil accumulation and photosynthesis in B.napus developing seed.The decrease rate of chlorophyll fluorescence parameter F_(v)/F_(m) of heat-stressed developing seed could be used as the index of heat tolerant rapeseed identification.Further,two heat insensitive rapeseed varieties with high oil content were identified.

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.

Effects of NaCl and NaHCO3 Stress on Photosynthesis and Chlorophyll Fluorescence Characteristics of Hemerocallis fulva ‘Golden Doll’

With Hemerocallis fulva‘Golden Doll'as an experimental material,the effects of different concentrations of neutral salt( NaCl) and alkaline salt( NaHCO3) stresses on photosynthesis and chlorophyll fluorescence characteristics in H. fulva seedlings were studied. The results showed that salt stress treatment significantly reduced the photosynthetic capacity of H. fulva. Under the NaCl and NaHCO3 stresses,the photosynthetic characteristics and chlorophyll fluorescence parameters of H. fulva seedlings were basically the same,but the photosynthetic characteristics and chlorophyll fluorescence parameter values of H. fulva seedlings were significantly different under different salt types and salt concentrations. With the extension of days of salt stress and the increase of salt concentration,the initial fluorescence yield( Fo) and non-photochemical quenching coefficient( NPQ) increased;the maximum fluorescence yield( Fm),maximum photochemical efficiency( Fv/Fm),PSII actual photosynthetic quantum yield( Y) and apparent quantum efficiency( AQY) all showed a downward trend;and moreover,with the extension of days of salt stress and the increase of salt concentration,the net photosynthetic rate( Pn) decreased and the intercellular CO2 concentration( Ci) increased. It was speculated that under salt stress,the photosynthetic characteristics of H. fulva leaves were inhibited. On the one hand,the non-stomatal limiting factor,i. e.,the chlorophyll content decreased,which led to the inhibition of photosynthetic characteristics. On the other hand,the decrease in the photosynthetic performance of mesophyll cells led to a decrease in the net photosynthetic rate of H. fulva. The changes of photosynthetic characteristics and chlorophyll fluorescence parameters in H. fulva caused by salt stress were closely related to the types of salts and salt concentration. High salt stress significantly inhibited the photosynthetic capacity of H. fulva‘Golden Doll',and the effect of NaHCO3 on H. fulva seedlings was significantly greater than that of NaCl.

Effects of Water Stress on Leaf Water and Chlorophyll Fluorescence Parameters of Sugarcane Seedling

[Objective] The aim was to explore the effects of water stress on leaf water and chlorophyll fluorescence parameters of sugarcane seedling,as well as to provide basis for the study on sugarcane production and evaluation. [Method] Seven different sugarcane varieties were studied at the seedling stage under drought stress,and the changes of leaf water and chlorophyll fluorescence parameters under stress conditions were detected. [Result] leaf water potential,leaf relative water content and soil relative water content showed a certain amount of internal relationship,the sugarcane varieties that had more tolerant to drought had higher utilization rate of soil water; the correlation analysis and factor analysis suggested that the survival rate at seedling stage under drought stress,Fv/Fm,leaf water potential and relative water content could be used as drought resistance evaluation indicators. [Conclusion] As a relatively independent influencing factor,water potential had dominating effect on drought resistance,and the reliability of Fv/Fm as drought resistance evaluation indicator had been verified.

Negative Effects of Oxytetracycline on Wheat (Triticum aestivum L.) Growth, Root Activity, Photosynthesis, and Chlorophyll Contents

A solution culture experiment was performed to investigate the effects of oxytetracycline （OTC） on wheat （Triticum aestivum L.） growth, chlorophyll contents, and photosynthesis at five levels of 0, 10, 20, 40, and 80 mmol L-1 OTC. OTC is toxic to wheat. The wheat growth, especially wheat root was significantly decreased. Further OTC also significantly decreased root activity, chlorophyll contents, and photosynthetic parameters except for intercellular CO2 concentrations. The different responses of indicators such as root number, root activity and so on to OTC were also observed. The IC50 values for the tested indicators to OTC ranged from 7.1 to 113.4 mmol L-1 OTC. The order of indicator sensitivity to OTC was root number stomatal conductance chlorophyll a total chlorophyll photosynthetic rates total surface area transpiration rate chlorophyll b fresh weight of root dry weight of root total length dry weight of shoot = fresh weight of shoot total volume. The root number was more sensitive than other indicators with the IC50 value of 7.1 mmol L-1 OTC, and could be taken as the sensitive indicator to predict the hazards of OTC to wheat.

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 levels(1,275 mm;2,200 mm;3,125 mm) with two deficit irrigation levels(150 and 75 mm).We demonstrated that under the ridge furrow(R) model,rainfall harvesting planting under 150 mm deficit irrigation combined with 200 mm simulated precipitation can considerably increase net photosynthesis rate(P_(n)),quantum yield of PSII(ΦPSⅡ),electron transport rate(ETR),performance index of photosynthetic PSII(F_(v)/F_(m)′),and transformation energy potential of PSII(F_(v)/F_(o)).In addition,during the jointing,anthesis and grain-filling stages,the grain and biomass yield in the R model are 18.9 and 11.1% higher than those in the flat cultivation model,respectively,primarily due to improved soil water contents.The winter wheat fluorescence parameters were significantly positively associated with the photosynthesis,biomass and wheat production.The result suggests that the R cultivation model with irrigation of 150 mm and simulated precipitation of 200 mm is an effective planting method for enhancing P_(n),biomass,wheat production,and chlorophyll fluorescence parameters in dry-land farming areas.

Effect of Zn, Cd and Cr on growth, water status and chlorophyll content of barley plants (<i>H. vulgare L.</i>)

To evaluate the potential of barley for the phytoremediation of soils contaminated by metals, we conducted a growth chamber experiment with plants exposed to various concentrations of Zn, Cd and Cr. Growth parameters, chlorophyll content and chlorophyll fluorescence were measured at 15 and 29 days after treatment application, and the metal concentration in the aerial part of the plant, the root and the soil was also measured. In all cases, the amount of metal accumulated in the plant increased by increasing the concentration of the applied metal, and the roots accumulated more metal than did the aerial part of the plant. The amount of Cr found in the soil was significantly lower than that of Cd and Zn. The toxic effect of Zn and Cd on the plant was low, affecting growth only at the highest concentrations. For Zn and Cd at the concentrations used, the decrease in water content was 14% compared with the control and 26% for Cr. For plants treated with the highest metal concentrations, the most significant differences were found in chlorophyll content, which had the lowest values compared with the control (23% for Zn, and 42% for Cd and Cr), and in chlorophyll fluorescence (2% for Zn, 23% for Cd and 29% for Cr). These decreases occurred 29 days after applying the Zn and Cd treatments. In plants treated with Cr, the decrease occurred 15 days after treatment application. Under our experimental conditions, barley is more tolerant to Zn and Cd than to Cr.

Effects of Water Stress on Photosynthesis and Fluorescence Characteristics in Peony

[ Objective] Study on the photosynthesis and fluorescence characteristics in peony under water stress. [ Method ] The two peony varieties Huhong and Luoyanghong were treated by different water stress for determining the photosynthesis and fluorescence characteristics. [ Result ] With the aggravation of water stress, the net photosynthetic rate （Pn） and stomatal conductance （Gs） decreased, while the intercellular CO2 concentration （Ci） increased. Drought could decrease Pn, constrain gas exchange and change the daily photosynthesis. Fo of peony leaf increased and Fv/Fm decreased under water stress especially water logging, causing the inactivation of the PS II reaction center, and the chlorophyll fluorescence characters gradually recovered until afternoon. [ Conclusion] The 75% soil relative water content （SRWC） is the best condition for growth of peony. Compared with drought, water logging is more unfit for the growth of peony. For the two varieties, Huhong assumed more tolerance to drought, accordingly more adaptability.

Relationships between leaf color changes,pigment levels,enzyme activity,photosynthetic fluorescence characteristics and chloroplast ultrastructure of Liquidambar formosana Hance

Liquidambar formosana Hance is an attractive landscape tree species because its leaves gradually change from green to red,purple or orange in autumn.In this study,the red variety of L.formosana was used to establish a quantitative model of leaf color.Physiological changes in leaf color,pigment levels,enzyme activity,photosynthetic fluorescence characteristics and chloroplast ultrastructure were monitored.The relationship between leaf color and physiological structure indices was quantitatively analyzed to systematically explore the mechanisms behind leaf color.Our data showed that with a decrease in external temperatures,chloroplast numbers and sizes gradually decreased,thylakoid membranes became distorted,and chlorophyll synthesis was blocked and gradually decreased.As a result,chloroplast membranes could not be biosynthesized normally;net photosynthesis,maximum and actual photochemical efficiency,and rate of electron transfer decreased rapidly.Excess light energy caused leaf photoinhibition.With intensification of photoinhibition,leaves protected themselves using two mechanisms.In the first,anthocyanin synthesis was promoted by increasing chalcone isomerase and flavonoid glycosyltransferase activities and soluble sugar content so as to increase anthocyanin to filter light and eliminate reactive oxygen species to reduce photoinhibition.In the second,excessive light energy was consumed in the form of heat energy by increasing the non-photochemical quenching coefficient.These processes tuned the leaves red.

Characteristics of Photosynthetic Fluorescence of Dominant Submerged Plants in Nanjishan Wetland of Poyang Lake in Winter

Based on the investigation of the species and frequency of submerged plants in Nanjishan Wetland of Poyang Lake in the winter of 2013,chlorophyll contents and photosynthetic fluorescence characteristics of the dominant submerged plants were studied using chlorophyll fluorescence imaging method. The results indicate that the major submerged plants of Nanjishan Wetland in Poyang Lake in winter included Hydrilla verticillata,Vallisneria natans,Najas minor,Potamogeton pectinatus,Nymphoides peltatum,Myriophyllum verticillatum and so on,and the dominant species were mainly H. verticillata and V. natans in different submerged plant communities. The chlorophyll content of H. verticillata is higher than that of V.natans,and the photosynthesis intensity of H. verticillata is stronger than that of V. natans. The value of Ca / Cb of H. verticillata is not large,which shows that the light-harvesting capacity of H. verticillata＇s chlorophyll is considerable in different sampling sites. The highest value of QY-max of V.natans is up to 0. 732,while the lowest value is only 0. 465; the highest value of QY-max of H. verticillata is 0. 677,while the lowest value is 0. 556.All values of QY-max of the submerged plants were lower than 0. 8,which shows that the submerged plants in Nanjishan Wetland of Poyang Lake may be subjected to certain external stress,which indicates that the external stress might cause some damage for the PSII reaction centers.

Response of leaf photosynthetic characteristics of Syringa oblata and Syringa reticulata var.mandshurica to chilling stress

Syringa species not only have good ornamental properties but also play an important role in the landscaping and environmental purification of cities.To investigate the chilling stress resistance of Syringa oblata Lindl.and Syringa reticulata var.mandshurica and provide theoretical grounds for the practical cultivation of Syringa species,in vitro leaves were used to study photosynthetic gas exchange parameters and chlorophyll fluorescence parameters.After nine hours of chilling,decreasing rates of net photosynthesis,stomatal conductance,and transpiration in S.reticulata var.mandshurica leaves were significantly greater than that of the S.oblata,while intercellular CO2 concentrations in S.oblata leaves were higher than those in S.reticulata var.mandshurica.The quantum yield of PSII reaction center(APSII)declined in S.reticulata and light capture efficiency(Fv 0/Fm 0)was stable.However,reduction percentages of Fv 0/Fm 0,APSII,and Fv/Fm in S.oblata were significant higher than those of S.reticulata var.mandshurica.After nine hours of chilling,the relative variable fluorescence of VJ and VI of S.oblata increased and the increasing rate of VJ was greater than VI.In contrast,the change of VJ and VI in S.reticulata var.mandshurica leaves was relatively small.This suggests that chilling primarily damaged the electron transport process of QA to QB at the receptor site of the PSII reaction center.Photosynthetic capacity of S.oblata was more sensitive to chilling stress compared to S.reticulate var.mandshurica,which the limitations were mainly due to non-stomatal factors such as the decrease in electron transport efficiency,activity in the PSII reaction center,and the destruction of the photodamage defense system.

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,spectral characteristic curve,active oxygen metabolism system,cell ultrastructure,and yield,under different Zn levels(0,250,500,750,and 1000 mg kg^(-1)).The results show that,low-level Zn treatments can effectively promote the synthesis of wheat chlorophyll,improve photosynthetic capacity,and increase yield.The yield of ZnL1(250 mg kg^(-1))was the highest in the two-year test,which increased by 20.4%in 2018 and 13.9%in 2019 compared with CK(0 mg kg^(-1)).However,a high Zn level had a significant stress effect on the photosystem of wheat.PIabs(reaction center performance index)and Fv/Fm(maximum photochemical efficiency)were significantly reduced,the active oxygen metabolism system was damaged,and the photosynthetic capacity was reduced,which in turn led to reduced yield.Among them,the yield of ZnL4(1000 mg kg^(-1))was the lowest in the two-year test,which was 28.1 and 16.4%lower than CK in 2018 and 2019,respectively.The green peak position of ZnL3 and ZnL4 had"red shift"to the long wave direction,while the red valley position of ZnL4 had"blue shift"to the short wave direction.Under ZnL4,some wheat leaf organelles began to decompose,vacuoles increased,cytoplasm decreased,cell walls thickened,chloroplast basal lamellae were disordered,and mitochondrial membranes disintegrated.Stepwise regression and Path analysis showed that Pn(net photosynthetic rate)played a leading role in the formation of yield.Redundancy(RDA)analysis showed that the optimal Zn level for wheat growth was about 250 mg kg^(-1),and wheat would be stressed when the soil Zn level exceeded 500 mg kg^(-1) in the test condition of this study.Findings of this study provide a theoretical basis for the diagnosis and prevention of heavy metal(Zn)pollution in the soil.

不同品种山核桃幼苗叶片光合及叶绿素荧光特性的比较分析

为了给不同品种山核桃高效栽培提供科学依据,开展5个山核桃品种幼苗叶片光合及叶绿素荧光特性的比较分析来筛选高光效品种,以2年生山核桃为研究对象,采用光合测定仪(LI-6800)及叶绿素荧光仪(MINI-PAM-Ⅱ)测定5个品种山核桃的叶片光合及叶绿素荧光特性,进行相关性分析,并利用隶属函数法对光合能力进行综合评价。相关性分析结果显示:5个山核桃品种P_(n)、C_(i)、G_(s)、T_(r)、WUE等指标均达到极显著差异;净光合速率与G_(s)、T_(r)呈极显著正相关,C_(i)与G_(s)、Y_(II)呈显著性正相关,与qP呈显著性负相关。隶属函数分析表明,供试品种的光合能力依次为:宁国山核桃2号>宁国山核桃4号>宁国山核桃3号>宁国山核桃5号>宁国山核桃1号。可见5个山核桃品种光合特性存在差异。宁国山核桃2号和3号光合能力较强,蒸腾速率较高,水分利用率低,生产中宜选择水肥条件较好的造林地;宁国山核桃4号耗散过剩光能热量的能力最强,具有较高的光保护能力,其他山核桃品种幼林期建议间作高杆玉米等适度遮阴。

嫁接方法与套袋处理对山苍子生长、光合特性及叶绿素荧光特征的影响

【目的】比较嫁接方法和套袋处理对山苍子嫁接幼苗生长、光合特性和叶绿素荧光特征的影响,筛选出最适宜的山苍子嫁接方法。【方法】以1年生山苍子实生苗为砧木、3年生山苍子穗条为接穗,分别采用嵌芽接、劈接和切接3种方法嫁接,每种嫁接方法设置套袋和不套袋2个处理,测定不同组合处理嫁接苗的成活率、生长性状指标、叶片光合特性和叶绿素荧光参数,对各指标进行多重比较,并利用模糊隶属函数法对各组合处理的嫁接苗情况进行综合评价。【结果】3种嫁接方法中,不套袋嵌芽接的嫁接成活率最高(93.75%),劈接苗和切接苗经套袋处理的成活率分别较不套袋处理提高9.03%和26.01%;整体以套袋处理成活率稍高。不同山苍子嫁接苗新枝长、新枝基径和叶片数在嫁接后120~150 d达到峰值,其中新枝长以套袋切接苗最大,新枝基径以套袋嵌芽接苗最大,叶片数以不套袋切接苗最大,分别为26.06 cm,5.69 mm和35.55片。与不套袋处理相比,套袋处理嵌芽接和劈接苗叶片的净光合速率(Pn)、蒸腾速率(T_(r))和气孔导度(G_(s))均有所降低,切接苗叶片的P_(n)、T_(r)、G_(s)和水分利用率(WUE)均有所提高;叶片胞间CO_(2)浓度(Ci)以套袋劈接苗最高,为272.11μmol/mol。与不套袋处理相比,套袋处理嵌芽接苗叶片的实际光化学效率(YⅡ)和光化学荧光淬灭系数(qP)以及切接苗PSⅡ最大光合效率(F_(v)/F_(m))、YⅡ和非光化学荧光淬灭系数(NPQ)均有所提高,而嵌芽接苗和劈接苗叶片的F_(v)/F_(m)、NPQ以及切接苗叶片的qP均有所降低。不同组合处理山苍子嫁接苗综合评分从高到低依次为套袋嵌芽接苗>不套袋劈接苗>套袋切接苗>不套袋嵌芽接苗>不套袋切接苗>套袋劈接苗。【结论】山苍子不同组合处理中,以套袋嵌芽接苗和不套袋劈接苗各项指标的综合表现较优,其最适宜的嫁接方法为套袋嵌芽接,建议在江西地区推广应用。

葡萄叶绿素荧光参数测量方法的优化与日变化特征分析

【目的】确定葡萄叶绿素荧光参数测量最适的暗适应时间、测量光强度,分析葡萄叶绿素荧光参数日变化特征并确定最适测量时间,提出优化测量方法的建议,为进一步研究葡萄光合特性提供理论依据,以提高研究数据的准确性和可靠性。【方法】选择阳光玫瑰葡萄和巨峰葡萄叶龄为40~50 d的健康成熟叶片,利用JIP测定(JIP-test)和主成分分析(PCA)研究葡萄叶片在不同暗适应时间(5、10、15、20、25、30、35和40 min)、不同测量光强度[500、1000、1500、2000、2500、3000和3500μmol/(m^(2)·s)]和一天中不同时间点(8:00、10:00、12:00、14:00、16:00、18:00和20:00)的快速叶绿素荧光诱导动力学(OJIP)曲线特征,分析不同测量条件对葡萄叶片叶绿素荧光参数的影响。【结果】暗适应时间和测量光强度均明显影响葡萄叶片叶绿素荧光参数,较长的暗适应时间和较高的测量光强度能获得更稳定和可靠的测量结果。OJIP曲线特征显示,在较短的暗适应时间(5~15 min)内,各暗适应时间与暗适应5 min间的特征区间(OJ相、JI相和IP相)相对可变荧光差值(ΔWOJ、ΔWJI和ΔWIP)曲线变化幅度较大,初始荧光(F_(o))、最大荧光(F_(m))和最大光化学效率(F_(v)/F_(m))等参数波动较大,当暗适应时间达30 min以上时,各参数再无显著变化(P>0.05,下同),趋于稳定。随着测量光强度的增加,F_(m)、F_(v)/F_(m)、OJIP曲线的初始斜率(M_o)和单位面积反应中心数量(RC/CSm)等参数呈上升趋势,各测量光强度与500μmol/(m^(2)·s)测量光强度间的ΔWOJ、ΔWJI和ΔWIP曲线呈正K峰、负H峰和正G峰,当光强度达3000μmol/(m^(2)·s)以上时,各参数均无显著变化。葡萄叶片的多数叶绿素荧光参数随着一天中时间点的推移而变化,光系统II(PSII)光化学效率在12:00之前较高,14:00时光化学效率下降,16:00之后PSII逐渐恢复至最佳状态。【结论】针对葡萄叶片进行OJIP曲线测定时,暗适应时间应为30 min以上,最小测量光强度为3000μmol/(m^(2)·s),测量时间宜选择在12:00之前和16:00之后,以确保结果的准确性和可靠性。

南疆地区复种早熟粮饲兼用玉米叶绿素荧光特征分析

【目的】为明确南疆地区复种早熟粮饲兼用玉米品种最佳种植密度以及不同密度下叶绿素荧光特征参数变化规律及其与产量形成的关系,为南疆地区复播玉米种植技术的提升提供参考依据。【方法】以自育早熟粮饲兼用玉米杂交新品种XL1822和XL1903为材料,设置高、低两种密度(9.00×10^(4)和11.25×10^(4)株/hm^(2)),研究两个玉米品种高、低密度下叶片叶绿素荧光特征参数、主要农艺性状、干物质积累及产量结构等的差异。【结果】XL1822低密度处理在拔节期、大喇叭口期、吐丝期、灌浆期叶片实际光量子产量[Y(Ⅱ)]、光化学淬灭系数(qL)、PSⅡ反应中心活性较高;XL1903高密度处理在拔节期、大喇叭口期、吐丝期叶片Y(Ⅱ)、qL较高。XL1822低密度处理在吐丝期、灌浆期、成熟期叶片SPAD值略高于高密度。XL1903高密度处理全生育期叶片的SPAD值较高。XL1822低密度籽率产量为9250 kg/hm^(2)、干物质积累量为15590 kg/hm^(2),显著高于高密度处理。XL1903高密度籽率产量为9065 kg/hm^(2)、干物质积累量为19095 kg/hm^(2),显著高于低密度处理。【结论】较高的叶绿素荧光特征参数和SAPD值为玉米产量形成和干物质积累奠定基础。极早熟品种XL1822低密度处理、早熟玉米品种XL1903高密度处理在关键生育时期植株Y(Ⅱ)、qL、PSⅡ反应中心活性较高,因此XL1822种植密度为9×10^(4)株/hm^(2),XL1903种植密度为11.25×10^(4)株/hm^(2)时在南疆地区可获得较高产量。

辣椒叶片水分胁迫高光谱特性研究

为精准判别作物需水程度,以生长期辣椒为实验样本,对辣椒进行不同程度的水浸、干旱等水分胁迫处理,分析不同水分胁迫程度下辣椒叶片的高光谱响应特性。样本分为重度干旱、轻度干旱、轻度水浸、重度水浸等4个水分胁迫组和一个实验对照组,共5个数据组,每组20株辣椒,待各组叶片外观出现明显差异时,分别采集各组辣椒叶片的叶绿素荧光参数与高光谱数据。比较多元散射校正(MSC)、SG卷积平滑滤波和标准正态变换(SNV)3种不同的预处理方法对背景信息干扰的消除效果。采用SPA算法和CARS算法提取对水分胁迫敏感的特征波长。建立预测辣椒叶片不同水分胁迫程度的支持向量机(SVM)、BP神经网络、径向基函数(RBF)和随机森林(RF)模型。结果说明,SG-SPA-RFB为预测辣椒叶片水分胁迫程度的最优组合,其训练集准确率为99.02%,测试集准确率为94.00%。本研究为判断辣椒植株水分胁迫状态提供了一种便捷可靠的无损检测方法。

7个杨树品种苗期叶片解剖结构和叶绿素荧光特性研究

本研究旨在筛选具有高抗逆性和强适应性的杨树优良品种。通过系统研究7个杨树品种的苗期表观生长性状、叶片解剖结构和叶绿素荧光生理特征,并采用单因素方差分析方法比较各品种间指标的差异,同时运用主成分分析法对苗期的生态适应性进行综合评价。结果表明显示,(1)各杨树品种苗期生长表现、叶绿素含量和叶绿素荧光参数之间存在显著差异,叶片解剖结构中的下层栅栏厚度、上表皮厚度及上表皮相对厚度有显著差异。其中‘湘林75’和‘巨霸杨’叶绿素含量较高,Y(Ⅱ)、ETR、qP等叶绿素荧光参数也较高,光合能力较强;‘江淮1号杨’叶片较厚,下层栅栏组织发达,抗旱性较强。(2)叶片解剖结构与叶绿素荧光参数间存在相关关系,中脉厚度与ETR、Y(Ⅱ)均显著负相关,栅栏组织、CTR与Fv/Fm显著正相关。叶绿素含量与叶绿素荧光参数间存在相关关系,但未达显著水平。(3)7个杨树品种苗期生态适应性由强到弱为‘湘林75’>‘巨霸杨’>‘湘林90’>‘湘林80’>‘江淮1号杨’>‘2025杨’>‘皖林1号杨’(CK)。

干旱胁迫条件下朱槿叶绿素荧光特性

以朱槿为试验材料,研究了干旱胁迫及复水对朱槿叶片叶绿素荧光参数的影响。结果表明:朱槿在经受25 d自然干旱胁迫后,除Fv/Fm值显著降低外,Y(Ⅱ)、qP、NPQ、ETR等值均有所上升。复水1 d后,Fv/Fm值有止降回升的趋势,Y(Ⅱ)、qP、NPQ、ETR等参数则恢复到对照水平。利用直角双曲线修正模型拟合的快速光曲线结果表明,中度干旱胁迫提高了朱槿光化学反应的启动能力,在弱光条件下具有最高的光能利用效率。当光强超过190μmol/(m^(2)·s)时,CK和复水1 d的适应能力更强,具有最大适应光强变化的能力和光合活性。研究综合认为,朱槿在干旱胁迫下具有良好的自身调节能力,具有较强的光合系统损伤修复能力,表现出极强的抗干旱胁迫能力,可在较干旱地区栽培应用。

The characteristics of CO_2 assimilation of photosynthesis and chlorophyll fluorescence in transgenic PEPC rice

With PEPC, PPDK, NADP-ME and PEPC+ PPDK transgenic and untransformed rice (Orysa sativa L.), the activities of related C4 photosynthesis enzymes, the chlorophyll fluorescence parameters, CO2 exchange and other physiological indexes were compared, in which the physiological characteristics of PEPC transgenic rice were mainly studied. The results were as follows: (i) The activities of PEPC in PEPC transgenic rice were 20-fold higher than those in untransformed rice; the light-saturation photosynthetic rates and the carboxylation efficiency of PEPC transgenic rice were increased by 55% and 50% more than those of untransformed rice, respectively, while the CO2 compensation point decreased by 27%. (ii) The PS II photochemical efficiency (Fv/Fm) and photochemical quenching (qp) of transgenic PEPC rice decreased less in comparison with those of untransformed rice after the treatment with high light intensity (3 h) or methyl viologen (MV), a photooxidative reagent, which demonstrated that the tolerance of PEPC