Rapid determination of leaf water content for monitoring waterlogging in winter wheat based on hyperspectral parameters

Waterlogging is becoming an obvious constraint on food production due to the frequent occurrence of extremely high-level rainfall events.Leaf water content(LWC)is an important waterlogging indicator,and hyperspectral remote sensing provides a non-destructive,real-time and reliable method to determine LWC.Thus,based on a pot experiment,winter wheat was subjected to different gradients of waterlogging stress at the jointing stage.Leaf hyperspectral data and LWC were collected every 7 days after waterlogging treatment until the winter wheat was mature.Combined with methods such as vegetation index construction,correlation analysis,regression analysis,BP neural network(BPNN),etc.,we found that the effect of waterlogging stress on LWC had the characteristics of hysteresis and all waterlogging stress led to the decrease of LWC.LWC decreased faster under severe stress than under slight stress,but the effect of long-term slight stress was greater than that of short-term severe stress.The sensitive spectral bands of LWC were located in the visible(VIS,400–780 nm)and short-wave infrared(SWIR,1400–2500 nm)regions.The BPNN Model with the original spectrum at 648 nm,the first derivative spectrum at 500 nm,the red edge position(λr),the new vegetation index RVI(437,466),NDVI(437,466)and NDVI´(747,1956)as independent variables was the best model for inverting the LWC of waterlogging in winter wheat(modeling set:R^(2)=0.889,RMSE=0.138;validation set:R^(2)=0.891,RMSE=0.518).These results have important theoretical significance and practical application value for the precise control of waterlogging stress.

Review of theoretical methods and research aspects for detecting leaf water content using terahertz spectroscopy and imaging

The water content in vegetative leaves is an important indicator to plant science.It reveals the physiological status of plants and provides valuable information in irrigation management.Terahertz(THz)as a state-of-the-art technology shows great potential in measuring and monitoring the water status in plant leaves.This paper reviewed the theoretical models for calculating water content in the plant leaves,the methods for eliminating the scattering loss caused by the surface roughness of leaf,the applications of THz spectroscopy and THz imaging for monitoring leaf water content and describing leaf water distribution.The survey of the researches presents the considerable advantages of this emerging and promising THz technology in agriculture.

Estimating leaf water content at the leaf scale in soybean inoculated with arbuscular mycorrhizal fungi from in situ spectral measurements

Leaf water content(LWC)of crops is a suitable parameter for evaluation of plant water status and arbuscular mycorrhizal effect on the host plant under drought stress.Remote sensing technology provides an effective avenue to estimate LWC in crops.However,few LWC retrieval models have been developed specifically for the arbuscular mycorrhizal inoculated crops.In this study,soybean with inoculation and non-inoculation treatments were planted under the severe drought,moderate drought and normal irrigation levels.The LWC changes under different treatments at the 30 th,45 th and 64 th day after the inoculation were investigated,and the spectral response characteristics of inoculated and non-inoculated soybean leaves under the three drought stresses were analyzed.Five types of spectral variables/indices including:raw spectral reflectance(R),continuum-removed spectral reflectance(R C),difference vegetation index(DVI),normalized difference vegetation index(NDVI)and ratio vegetation index(RVI)were applied to determine the best estimator of LWC.The results indicate that LWC decreased as the aggravating of drought stress levels.However,LWC in inoculated leaves was higher than that in the counterparts under the same drought stress level,and the values of raw reflectance measured at inoculated leaves were lower than the non-inoculated leaves,especially around 1900 nm and 1410 nm.These water spectral features were more evident in the corresponding continuum-removed spectral reflectance.The newly proposed DVI C(2280,1900)index,derived from the continuum-removed spectral reflectance at 2280 nm and the raw spectral reflectance at 1900 nm in DVI type of index,was the most robust for soybean LWC assessment,with R 2 value of 0.72(p<0.01)and root mean square error(RMSE)and mean absolute error(MAE)of 2.12%and 1.75%,respectively.This study provides a means to monitor the mycorrhizal effect on drought-induced crops indirectly and non-destructively.

Leaf Water Status and Its Relationship with Reproductive Responses of Common Bean (<i>Phaseolus vulgaris</i>L.) Genotypes under Water Stress

Two tolerant (BB24 and BB43) and two susceptible (BARI busbean-2 and BB04) genotypes of common bean (Phaseolus vulgaris L.) were evaluated for their water status and its relationship with reproductive responses under continuous water stress (50% field capacity) and control (80% field capacity) conditions in a net house covered with polyethylene sheet at the Bangabandhu Sheikh Mujibur Rahman Agricultural University, Bangladesh. Under water stress condition, the susceptible genotype namely BB04 exhibited more negative leaf water potential (LWP) which was followed by that of BARI bushbean-2 in all the time of the day except at noon. The tolerant genotype namely BB24 exhibited less negative LWP at noon. The tolerant genotypes maintained higher relative water content (WRC) than the susceptible ones from dawn to dusk. The relationship between RWC and LWP was examined separately for four genotypes under water stress condition. The genotype BB24 showed a smaller decrease in RWC with more negative LWP than BB04. Water stress reduced pod setting ratio. The relationship between the leaf water status and reproductive responses showed that the genotype with a little reduction in mid-day drop of RWC or with high mid-day RWC displayed a high pod setting ratio.

基于无人机多光谱影像的矮林芳樟叶片含水率与叶水势反演

叶片含水率和叶水势反映植物组织中水分的状态,是衡量植物水分供应和水分利用效率的重要指标。为探究基于不同高度下无人机多光谱影像反演叶片含水率和叶水势模型的差异,本研究在3个飞行高度处理F30、F60、F100(30、60、100 m)下采集多光谱影像数据,通过使用6种光谱反射率+经验植被指数的组合与地面实测数据进行相关性分析,获得不同飞行高度下的光谱反射率+经验植被指数组合与叶片含水率和叶水势的反演模型及其决定系数,以决定系数为依据分别构建支持向量机(SVM)、随机森林(RF)和径向基神经网络(RBFNN)模型,分析不同飞行高度无人机多光谱影像反演芳樟叶片含水率和叶水势的精度。结果发现:3个飞行高度下,基于RF模型的反演精度均高于SVM模型和RBFNN模型。F30处理对叶片含水率与叶水势反演效果均优于F60和F100处理。F30处理对叶片含水率反演的敏感光谱反射率+植被指数组合为红光波段反射率(R)、红边1波段反射率(RE1)、红边2波段反射率(RE2)、近红外波段反射率(NIR)、增强型植被指数(EVI)、土壤调节植被指数(SAVI)。RF模型训练集的R2、RMSE、MRE分别为0.845、0.548%、0.712%;测试集的R2、RMSE、MRE分别为0.832、0.683%、0.897%。对叶水势反演的敏感光谱反射率+植被指数组合为R、RE2、NIR、EVI、SAVI、花青素反射指数(ARI)。RF模型训练集的R2、RMSE、MRE分别为0.814、0.073 MPa、3.550%;测试集的R2、RMSE、MRE分别为0.806、0.095 MPa、4.250%。研究结果表明飞行高度30 m与RF方法分别为反演叶片含水率和叶水势的最优光谱获取高度与最优模型构建方法。本研究可为基于无人机平台的矮林芳樟水分监测提供技术支持,并可为筛选无人机多光谱波段与经验植被指数、实现植物长势参数快速估测提供应用参考。

亚热带树种在未成林造林地的凋落物量和周转与叶片性状的关系

【目的】测定亚热带树种的叶片功能性状、凋落叶质量、凋落物量和周转期,揭示叶片性状对凋落物量和周转的影响,为杉木采伐后如何选择造林树种以改善土壤肥力提供科学依据。【方法】选取在二代杉木林采伐迹地营造的17种亚热带树种,测定其在3年生未成林造林地的凋落物量和周转期,同时测定各树种的叶片功能性状(比叶面积、干物质含量、氮含量等)和凋落叶质量(碳氮比、单宁含量、可溶性糖含量等),建立叶片性状与凋落物量和周转期的回归关系。【结果】17种树种中,米老排凋落物量最高(6.67 t·hm^(-2)a^(-1)),杉木凋落物量最低(0 t·hm^(-2)a^(-1));江南桤木凋落叶周转期最短(0.09年);深山含笑凋落叶周转期最长(1.09年)。凋落物量随比叶面积增加而增加,随叶氮含量增加而降低;凋落叶周转期随凋落叶碳氮比和单宁含量增加而增加,随凋落叶最大持水率增加而降低。【结论】在亚热带未成林造林地中,凋落物量受比叶面积和叶氮含量的影响,凋落叶周转期受凋落叶碳氮比、单宁含量和最大持水率的影响;杉木在未成林造林地阶段的凋落物归还量极少。经营亚热带人工林时,要考虑种植比叶面积和凋落叶最大持水能力较高、凋落叶单宁含量和碳氮比较低的树种,以提高林地凋落物归还量和周转速率,改善退化人工林的土壤肥力。

基于机器学习的油菜叶片水分含量高光谱估测

含水率是影响光合作用的重要因素之一,为了构建效果更好、更具普适性的油菜叶片含水量(leaf water content,LWC)定量监测模型,以蕾薹期、初花期油菜叶片为研究对象,采用自然风干法去除叶片水分,同步采集叶片质量和光谱信息。为了降低干扰以及消除噪声,采用标准正态变量变换、Savitzky-Golay卷积平滑算法(SG平滑)、多元散射校正、一阶求导和二阶求导5种方法对光谱数据进行预处理,并结合偏最小二乘法(partial least squares,PLS)分析选取最优预处理方法;采用连续投影算法(successive projections algorithm,SPA)筛选预处理后的光谱特征变量,获得对水分含量变化敏感的特征波长;利用支持向量机(support vector regression,SVR)和BP神经网络(back-propagation neural network,BPNN)方法,以特征波长建立的光谱指数为自变量建立油菜叶片水分含量估算模型。结果表明:采用多元散射校正预处理综合表现最好,2个生育期预测集相关系数均达到0.71以上;通过SPA法选择特征变量,分别筛选出特征波长,其中蕾薹期6个,初花期7个;在蕾薹期和初花期叶片水分含量预测模型中,基于SVR模型和BPNN模型建立的模型预测集决定系数(R^(2))均在0.800以上,均能实现油菜叶片水分含量的精准监测,其中SVR模型预测效果优于BPNN模型,R^(2)分别为0.857和0.827,RMSE分别为1.791和1.521。因此,利用油菜叶片高光谱建模反演油菜叶片含水率能准确监测油菜叶片含水率,可为精准农业水分管理提供理论参考。

18种城市园林树种光合耐脱水能力及抗旱性综合评价

随着未来全球气候变化导致的温度上升和蒸气压亏缺增加,筛选耐旱性强的城市园林树种对城市绿化具有十分重要的意义。本研究比较18种城市园林树种的叶光合耐脱水能力(脱水曲线上PSⅡ潜在量子效率开始下降时对应的相对含水量,RWC crit)的差异及与叶形态(叶面积、比叶质量、叶干物质含量、叶厚度和叶密度)、解剖结构(气孔密度、气孔长、气孔指数及上表皮、下表皮、栅栏组织、海绵组织、维管束鞘厚度及占横截面面积的比例)的关系和18种园林树种的抗旱能力。结果表明,18种树种的RWC crit在30.2%~58.0%,平均值为44.7%,18种树种的光合耐脱水能力RWC crit与叶面积呈显著正相关,与叶横截面下表皮面积所占比例呈显著负相关,18种园林树种的RWC crit与其综合抗旱能力变化趋势一致。研究结果表明,RWC crit可以作为耐旱性指标预测园林树种的耐旱性,对未来城市耐旱树种筛选和合理经营有一定价值。

北京山区黄栌叶片水分和光能利用效率季节变化及影响因子

未来气候变化将影响光合环境资源供给,尤其是水分和光能。为深入了解植物对气候变化的适应性,使用LI-6800便携式光合仪,于2021年5-10月份(完全展叶期)测定了北京山区广布灌木黄栌(Cotinus coggygria)叶片的光响应曲线,分析其水分利用效率(WUE=最大净光合速率[P_(nmax)]/气孔导度[g_(s)])和光能利用效率(LUE)的季节变化特征及影响因子。结果显示:黄栌叶片WUE在5-6月份呈下降趋势,7-10月份比较稳定;LUE在5-7月份呈上升趋势,8-10月份比较稳定。WUE和LUE的生长季平均值分别为98.25μmol/mol和0.06 mol/mol,变异系数分别为22%和17%,两者呈负相关(R^(2)=0.86;P<0.01)。环境因子中,WUE和LUE主要受土壤含水量(SWC)影响,WUE随SWC增加呈线性降低趋势,而LUE随SWC增加呈线性增加趋势。SWC每增加0.1 m^(3)/m^(3),P_(nmax)和g_(s)分别线性增加4.23μmol m^(-2)s^(-1)和0.07 mol m^(-2)s^(-1),即g_(s)对SWC变化的敏感性比P_(nmax)高。光合有效辐射(PAR)对WUE和LUE的影响不显著。生物因子中,比叶面积(SLA)是影响WUE和LUE的主要因子,WUE随SLA上升而上升,LUE随SLA上升而下降。叶氮含量(LNC)与WUE和LUE均不显著相关。SWC和SLA双因子线性回归模型均可以较好模拟WUE和LUE的季节变化,解释度分别为91%和71%,且其中SWC的标准回归系数较大,说明SWC是影响WUE和LUE变异的主导因子。结果表明SWC是限制黄栌叶片WUE和LUE的主要环境因子,SLA是调控WUE和LUE的关键生物因子,其中SWC起主要调控作用。研究结果利于深入了解北京山区灌木生态功能对未来气候变化的响应。

干旱胁迫和复水对掌叶木幼苗叶片结构和水分状况的影响

为给喀斯特地区石漠化治理和掌叶木(Handeliodendron bodinieri)的人工繁育提供科学依据,以1年生掌叶木幼苗为试材,通过自然干旱试验,测定干旱胁迫和复水条件下叶片的水分参数,观察解剖结构变化,探究干旱胁迫和复水对掌叶木幼苗叶片解剖结构和水分含量的影响。结果表明,干旱胁迫第0~15天,含水量、相对含水量和水分饱和亏缺均变化较小;干旱胁迫第18天,含水量和相对含水量均降低,水分饱和亏缺增加。干旱胁迫第12天,自由水含量最高,束缚水含量最低;干旱胁迫第18天,束缚水含量最高,自由水含量最低。干旱胁迫第0~18天,上表皮和海绵组织厚度均呈下降趋势,栅海比和组织结构紧密度均呈上升趋势;气孔宽度和气孔面积均呈下降趋势,气孔长度变化不显著,气孔密度呈先升后降的趋势。复水后,含水量、自由水和束缚水含量均快速恢复,气孔宽度、气孔长度、气孔密度和气孔面积均增加,组织结构紧密度降低,组织结构疏松度增加,说明幼苗具有较强的耐旱能力和复水后恢复能力。

基于神经网络的烟叶复烤回潮过程预测控制模型构建

针对烟叶复烤回潮过程系统复杂、参数耦合干扰、时间滞后等问题,以两段式烟叶复烤回潮工艺为研究对象,依据生产中工艺参数实时数据,构建了基于支持向量机(SVM)神经网络的烟叶复烤回潮过程预测控制模型。该模型通过训练学习,可以准确描述出口含水率与其他工艺参数之间的内在关系,有效预测二次润叶出口含水率,最大绝对误差不超过0.45%,为烟叶复烤回潮工艺提供了可行的预测控制方案,有利于出口含水率的有效调控,对烟丝生产加工具有重要的指导意义。

Effect of Kaolin Film Particle Applications (Surround WP^®) and Water Deficit on Physiological Characteristics in Rose Cut Plants (<i>Rose spp</i>L.)

The effect of foliar applications of a kaolin clay particle film (Surround WP) on leaf temperature (Tlf), chlorophyll fluorescence (Fv/Fm), shoot length, production and water relations in well-irrigated and water-stressed rose cut plants (Rose spp) were studied during ten weeks. Plants were sprayed twice at first and fifth week after the experiment started with aqueous suspensions of Kaolin (Surround) at a dose of 5% (w/v). The interaction between Kaolin applications and water status did not showed significances. Water stress decreased the stomatal conductance (gs), leaf water content (LWC), shoot length and the number of marketable floral stems. Kaolin sprays did not affect on SPAD readings, chlorophyll fluorescence, gs, LWC and shoot length. Kaolin reduced leaf temperature by 2.5°C approximately at midday compared to plants non-sprayed with kaolin. These results show that kaolin foliar applications could be considered an useful tool at early growth stage in improving rose plant acclimation to high temperatures levels under greenhouse conditions in tropical regions.

Growth and Physiological Performance of Aerobic and Lowland Rice as Affected by Water Stress at Selected Growth Stages

Aerobic rice technology is still new in Malaysia, and information regarding MARDI Aerob 1(MA1), the first local aerobic rice variety, is still lacking. Therefore, comparative studies were carried out to determine the physiological performance of aerobic rice variety MA1 and lowland rice variety MR253 under water stress given at the panicle initiation, flowering and ripening stages. This experiment was arranged in a randomized complete block design. Stomatal conductance(g_s), chlorophyll a fluorescence(F_v/F_m), leaf relative water content(leaf RWC), and soil moisture content(SMC) as well as yield component parameters such as panicle number, grain yield and 100-grain weight were measured. Results revealed that gs and leaf RWC for both varieties decreased with depletion of SMC. The correlation study between the physiological parameters and SMC indicated that F_v/F_m was not affected by water stress, regardless of varieties. The yield components(panicle number, grain yield and 100-grain weight) for both varieties greatly decreased when water stress was imposed at the panicle initiation stage. This study showed that the panicle initiation period was the most sensitive stage to water stress that contributed to a substantial reduction in yield for both varieties. Under the aerobic condition(control), MR253 produced higher panicle number, 100-grain weight and yield than MA1. Although MR253 is bred for lowland, it is well adapted to aerobic condition.

Responses in gas exchange and water status between drought-tolerant and-susceptible soybean genotypes with ABA application

The purpose of this study was to investigate the physiological responses of drought-tolerant and drought-susceptible soybean genotypes to exogenous abscisic acid(ABA) application during progressive soil drying at seedling stages. Five-day old soybean seedlings were transplanted into PVC tubes filled with soil mixture. Seedlings were watered daily with similar water volumes until second trifoliate leaves emerged, and thereafter soil drying with or without exogenous ABA application was imposed. Half of the seedlings of each genotype were left for regular watering as control plants. Soil water status declined significantly over seven days of withholding water supply for both genotypes. Leaf expansion rate, stomatal conductance(g_s), leaf water potential(ψ_w), and relative water content of leaves(%RWC) declined significantly under soil drying as well as soil drying with ABA application, compared to their values for well-watered soybean genotypes. However, a drought-tolerant genotype(C12) responded more rapidly than a drought-susceptible genotype(C08) after imposition of soil drying and soil drying with exogenous ABA. In addition, application of exogenous ABA to water-restricted soybeans resulted in higher %RWC and ψwin the drought-tolerant than in the drought-susceptible genotype. Compared to the drought-susceptible genotype, the drought-tolerant genotype was more responsive to exogenous ABA application, resulting in a higher root-to-shoot ratio.

3个紫薇品种形态和生理特性对干旱胁迫的响应

【目的】探明干旱胁迫对紫薇品种形态特征和生理特性的影响,为鉴选耐旱紫薇品种提供参考依据。【方法】以睡美人、莎拉的最爱、纳齐兹3个紫薇典型品种为材料,采用持续干旱和梯度干旱(盆苗浇水量100%;浇水量75%,轻度干旱;浇水量50%,中度干旱;浇水量25%,重度干旱;浇水量0%,极度干旱)胁迫法进行处理,通过测定植株形态、盆苗日失水量、叶片含水量、复水成活率和叶绿素荧光等指标变化,对3个紫薇品种的耐旱性开展综合分析。【结果】持续干旱试验中,紫薇植株形态评分依次为睡美人>莎拉的最爱>纳齐兹;平均盆苗日失水量/水盘日蒸发量比值依次为睡美人<莎拉的最爱<纳齐兹;睡美人、莎拉的最爱复水成活率均为80%,纳齐兹为60%。梯度干旱试验中,紫薇品种植株形态得分、叶片含水量、最大荧光(F_(m))、最大光化学效率(F_(v)/F_(m))均随干旱程度的加深而降低,初始荧光(F_(0))则随之增大,各指标变化幅度3个紫薇品种间表现为睡美人<莎拉的最爱<纳齐兹;睡美人盆苗浇水量0%处理、莎拉的最爱盆苗浇水量0%和25%处理、纳齐兹盆苗浇水量25%和50%处理下快速叶绿素荧光诱导曲线(OJIP曲线)在300μs出现显著峰值(K-band),说明干旱造成PSII供体侧的放氧复合体(OEC)受损。使用隶属函数法对3个紫薇品种的复水成活率、盆苗日失水量/水盘日蒸发量、植株形态、叶片含水量、PSⅡ初始荧光、PSⅡ最大荧光、PSⅡ最大光化学效率7个测量指标进行综合评价,分值依次为睡美人(0.934)>莎拉的最爱(0.366)>纳齐兹(0.116)。【结论】3个紫薇品种的耐旱能力依次为睡美人>莎拉的最爱>纳齐兹。睡美人、莎拉的最爱适合在节水园林中应用。

便携式玉米叶片含水率无损检测仪的设计与试验

【目的】设计一款便携式玉米叶片含水率检测仪,以实现植物叶片含水率的无损和快速现场检测。【方法】基于玉米叶片中的水分在波长980和1050 nm附近有吸收峰的现象,以峰值波长为980和1050 nm的发光二极管为便携式玉米叶片含水率检测仪的光源。分别以STC12C5A60S2单片机、数字光电传感器TSL2561和有机发光二极管为检测仪的控制器、检测器和显示器,采用C51语言编写检测仪的软件。以‘咸科858’和‘咸科602’两个玉米品种的叶片为对象,分析玉米叶片湿基含水率与波长980和1050 nm处吸光度值的关系,建立预测玉米叶片含水率的模型,将模型导入检测仪并对其性能进行测试。【结果】玉米叶片吸光度随含水率的增大而减小,可用二元一次关系式拟合叶片含水率与吸光度的关系,其相关系数为0.84。同国标规定的干燥法相比,该便携式检测仪对玉米叶片含水率的绝对测量误差为-6.3%~6.0%,平均误差为-0.1%,输出含水率的变异系数平均值为2.03%,每个样品的检测时间约为2 s。【结论】所设计的便携式玉米叶片含水率检测仪操作简单,结果可靠,可为其他植物叶片含水率的无损快速检测提供参考。

基于无人机多光谱影像的棉花SPAD值及叶片含水量估测

利用多光谱快速准确获取棉花花铃期旱胁迫性状对棉花后期产量和纤维品质具有重要帮助。为实现棉花关键抗旱指标的快速检测,该研究以253份棉花品种为材料,设置干旱胁迫和正常灌溉2个处理,在花铃期通过大疆精灵4多光谱无人机获得图像,分析花铃期干旱胁迫和正常处理棉花的光谱反射率,结合地面调查叶绿素相对值(S_(PAD))和叶片含水量(L_(WC))数据,结合神经网络算法中的径向基函数进行模型的预测。结果显示:棉花干旱胁迫前后除红光反射值略上升,其余4个光谱均小于正常处理;通过径向基函数模型估测S_(PAD)和L_(WC)的最佳估测模型都为二次函数,决定系数R^(2)分别为0.8488和0.9366,均方根误差R_(MSE)分别为2.005和0.930,相对误差R_(E)分别为0.004和0.011;将2个模型应用于试验区影像,对S_(PAD)及L_(WC)预测值进行聚类分析,根据S_(PAD)聚类结果,试验棉花旱情等级划分为特旱、重旱、中旱、轻旱、无旱5类,根据LWC聚类结果,试验棉花旱情等级划分为特旱、重旱、中旱、干旱、轻旱、无旱6类。以上模型及分类效果良好且符合棉花干旱胁迫的特点,研究结果可为快速评价棉花抗旱性、挖掘棉花抗旱基因提供技术支持。

基于叶片反射光谱和叶绿素荧光估测水稻叶片含水量

水稻冠层叶片含水量(leaf water content,LWC)快速无损监测对指导稻田精准灌溉和提高水稻水分利用效率具有重要意义。试验设置3个不同水分处理(传统淹灌、轻度干湿交替-15 kPa、重度干湿交替-30 kPa),于水分敏感期(抽穗灌浆期)动态监测顶1叶(L_(1))、顶2叶(L_(2))和顶3叶(L_(3))的光谱数据和叶绿素荧光参数,通过全光谱波段筛选出水分敏感波段,建立新型植被指数,结合叶绿素荧光参数,以期建立基于叶位组合的水稻冠层LWC精准监测模型。结果表明:水稻叶片水分敏感波段在近红外波段(1000~1400 nm),所构建新型植被指数NDSII_((1114,1387))较传统植被指数能更好地监测LWC;通过筛选与LWC有高相关性的荧光参数,基于实际光量子产量Y(Ⅱ)和植被指数NDSII_((1114,1387))的耦合监测模型较单一植被指数NDSII_((1114,1387))模型精度提高71.807%~83.976%。与单叶相比,L_(2)和L_(3)叶位组合的Y(Ⅱ)和植被指数NDSII_((1114,1387))耦合模型对水稻冠层LWC监测精度相较L_(2)、L_(3)分别显著(P<0.05)提高11.641%和23.029%。由此表明,基于叶位组合的叶片反射光谱与叶绿素荧光耦合可有效监测水稻冠层LWC,为光学仪器监测水稻LWC提供理论基础,并对未来利用反射光谱与荧光参数进行作物光合作用研究提供理论支持。

香花油茶不同无性系叶表型性状及叶绿素含量的差异

【目的】为香花油茶良种选育和生态经济型品种筛选提供参考。【方法】以生长良好的30个香花油茶无性系叶为材料,使用叶面积仪和Dualex植物多酚-叶绿素仪对叶表型性状和叶绿素含量进行测定。【结果】叶水分含量特征:叶含水量为52.07%~62.44%,含水量高于55%的无性系占比70%以上。叶表型性状:15号无性系的叶长最大,29号无性系的叶宽、叶面积、叶周长、形状系数均最小;各无性系叶表型性状的变异系数为9.18%~23.07%,叶周长的变异系数最小(为9.18%),叶面积的变异系数最大(为23.07%);叶宽、叶面积与其他叶表型性状间均存在极显著相关性;在主成分分析中,前2个主成分的累计贡献率达到92.708%,说明这2个主成分概括了6个性状的主要信息。其中,叶面积的特征向量值最大,其次是叶宽,叶面积和叶宽是区分香花油茶无性系最主要的叶性状。经聚类分析,香花油茶各无性系可被划分为3个类群。叶绿素含量:香花油茶不同无性系间叶绿素含量存在变异,变异系数为8.48%;25号无性系叶基、叶中的叶绿素含量与其他无性系有显著差异,叶尖叶绿素含量除与18号无性系无显著差异外,与其他无性系均有显著差异。【结论】香花油茶叶表型性状的遗传差异较大;叶中的叶绿素含量与叶总体的叶绿素含量的相关性最高,即叶中部可作为测定叶片叶绿素含量的最佳部位。