基于2DFT的植物叶片萎蔫程度与微环境因素相关性研究

在基于激光斜射测距原理的3D扫描装置实时获取的植株3D图像中,提取二维傅里叶(2DFT)谱中直流分量作为萎蔫指数来定量研究植物的萎蔫程度,采用西葫芦、葫芦、南瓜及秋葵4种植物的嫩叶期体态变化检验了二维傅里叶萎蔫指数与萎蔫程度的相关性,结果表明:二维傅里叶谱的直流分量(萎蔫指数)与萎蔫程度具有较好的相关性,R2达到0.82以上。在此基础上,运用SPSS软件建立了二维傅里叶谱叶片萎蔫指数与环境饱和水气压差及光合有效辐射系数的多元线性回归统计模型,可作为亏水胁迫程度的定量化指标。     

基于3-D数据的叶片萎蔫形态辨识方法

以西葫芦为试验对象,采用非接触式激光扫描获取植物叶片3-D形态信息,运用微分几何算法、二维傅里叶谱分析法、垂直投影叶面积法以及标准差法定义了4种植物萎蔫指数(TB_3D、RLWI-2DFT、RTPLA和RSD)用来定量刻画植物萎蔫状态。试验结果表明萎蔫指数能够很好地定量刻画植物萎蔫形态。其中TB_3D与太阳全辐射量、大气温度线性相关,决定系数取值范围分别为[0.710,0.721]和[0.513,0.589]。TB_3D与茎秆直径线性相关,决定系数为0.845。最后通过比较4种萎蔫指数刻画萎蔫状态的相关性,两两间决定系数大于0.736,结果表明4种指数的萎蔫表征效果基本一致。     

基于“双毯法”的植物叶态萎蔫辨识研究

为实现植物生命需水状况的无损检测,通过定量辨识植物叶态萎蔫特征反映植物亏水胁迫状况,基于分形理论"双毯法"定义了萎蔫指数LDBM,利用基于激光三角原理的三维激光扫描仪获取植物叶片表型点云数据,以西葫芦、秋葵、葫芦、南瓜4种植物为研究对象,结合饱和水汽压差与光合有效辐射2种微环境参数,进行了植物叶态萎蔫定量辨识研究。试验分析了4种植物萎蔫指数LDBM的日变化曲线,证明LDBM用于表征叶态萎蔫状况是合理和可行的;分析了萎蔫指数LDBM与微环境参数的相关性,4种植物LDBM与饱和水汽压差相关系数均大于0.81,与光合有效辐射相关系数均大于0.71,与2种参数都有很强的正相关性;并且与基于离散时域傅里叶变换定义的萎蔫指数L2DFT进行了对比,LDBM与L2DFT呈负相关性,4种植物的相关系数均大于0.82,表明LDBM能够准确地定量表征叶态萎蔫。     

基于TOF摄像机的植物叶态萎蔫辨识研究

为定量辨识植物叶态的萎蔫程度,定义了基于离散时域傅里叶变换的萎蔫指数,搭建了一套植物叶态采集系统,以黄瓜和绿皮西葫芦幼苗为试验样品,采用植株根部快速失水与汲水的方法,控制植株叶片处于不同程度的萎蔫状况,使用TOF摄像机获取叶态3D图像信息,对图像进行去噪、阈值分割、点积运算等处理,得到目标叶片的三维点云数据,运用离散时域傅里叶变换计算其萎蔫指数。通过对黄瓜单片叶和绿皮西葫芦多片叶在植物失水、叶片萎蔫阶段和植物吸水、叶片恢复阶段的萎蔫指数定量对比分析,以及对叶片萎蔫指数在整个植物水分胁迫过程的单因素方差分析,显著性分别为0.890 4、0.292 2、0.903 6,均大于0.05,验证了基于TOF摄像机的叶态萎蔫定量辨识方法的可行性与准确性。     

基于3-D图像的植物亏水胁迫萎蔫体态辨识方法

萎蔫现象是植物亏水胁迫环境下表现出的一种生命特征。为了定量辨识植株的萎蔫体态,在应用激光扫描装置快速获取植株3-D图像基础上,定义了4种萎蔫指数,即叶面卷曲统计指数、叶片形心的高斯曲率、基于形心切平面的叶尖投影以及叶片边缘投影求和平均。实验方法将叶片萎蔫程度分为5个等级水平(LS1~LS5),通过逐一检验每种定义的萎蔫指数是否具有单调性得出可应用性结论。实验结果表明距离投影算法满足萎蔫指数的单调要求,尤其是叶片边缘投影求和平均萎蔫指数具有更好的鲁棒性。     

植物叶片萎蔫过程的物理表示方法

为定量化描述植物叶片萎蔫的动态过程,提出一种基于物理模型的描述方法。首先基于植物叶片的三维模型构造体素结构用以抽象植物的细胞结构,在此基础上利用质点弹簧模型表示细胞之间的受力关系,然后根据欧拉-拉格朗日方程描述细胞的运动过程,最后采用隐式纽马克积分法对方程求解进而得到细胞的三维位置变化。以萎蔫状态下叶尖在几何空间的变化轨迹作为参考属性进行数据验证,模拟的叶尖运动方向与实测值相差19°,实测的叶尖三维空间位置与模拟结果的距离差值在0.68 cm至3.0 cm之间,数据表明所提算法得到的叶尖变化轨迹与真实叶尖变化轨迹接近;其次,从视觉角度评价,也可逼真地模拟萎蔫状态下叶片三维形态的变化过程。     

喀斯特地区黄壤土壤水库蓄存能力及分形估算

以重庆市黔江区喀斯特地区3种典型黄壤为研究对象,分析了其土壤水库蓄存能力,通过构建2种土壤粒径分形模型对3种土壤的土壤水库蓄存能力做了推导预测。结果表明,喀斯特地区黄壤土壤水库蓄存能力受到土壤密度、有机质、土壤颗粒和土层厚度的共同作用;以土粒粒径与颗粒数量关系求得的土壤分形维数(D1),以及以土粒粒径与颗粒质量关系求得的土壤分形维数(D2),可以用来推求喀斯特地区黄壤的田间持水率和萎蔫系数;利用土壤粒径分布进行的土壤水库蓄存能力预测,萎蔫系数的预测情况较田间持水率较差,这也造成了无效水库容与有效水库容预测精度比贮水库容和通透库容的预测低。     

日光温室黄瓜叶片形态和叶水势之间的关系

针对温室中黄瓜叶片在受到水分胁迫时会发生萎蔫的现象,希望利用计算机视觉技术提取黄瓜叶片形态变化这种叶片萎蔫时最直接的表象,并通过形态指标来量化这些形态特征.同时,结合当时叶片的水势状态,通过相关性分析,分析黄瓜叶片形态指数和叶片水势之间的相互关系.实验选用8组形态指标和叶片水势进行分析,结果表明:叶片延展率AR与叶片有相同截面惯性矩的椭圆形的延长率E、离心率Ec与叶片水势数据之间的相关性最好.     

基于三维光谱指数的土壤含水率反演研究

为研究三维光谱指数预测土壤含水率的效果,以期能为精准农业地表土壤含水率的快速精确测定提供参考.以浙江永康地区采集的不同含水率土壤样本为研究对象,利用ASD FieldSpec 3光谱仪在室内对土样进行光谱反射率测量,并基于原始光谱反射率(R)及其对应的一阶微分光谱(FD)、二阶微分光谱(SD)进行一维二维及三维光谱指数的提取.再通过偏最小二乘回归模型(PLSR)对不同光谱指数建模,并对比分析不同模型的反演精度.结果表明:三维光谱指数相比于一维二维光谱指数对土壤含水率更加敏感;基于三维光谱指数(TBI2)偏最小二乘回归模型具有最佳的预测效果,其Rv2=0.92,RPD可达3.32;对于土壤含水率反演而言,三维指数(R-TBI1)相比于其他的光谱指数更具重要性,其变量投影重要性(VIP)达1.04.该研究表明利用三维光谱指数建模为高光谱遥感对表层土壤含水率的快速有效监测提供了一条新途径.     

土壤重金属胁迫对经济树种的光合响应特征研究

为揭示土壤重金属胁迫对经济树种的光合响应特征及其相关性,选取北京市常见经济树种(核桃树(Juglansregia L.)、桃树(Amygdaluspersica L.)和李树(Prunussalicina Lindl.))作为研究对象,研究了不同土壤重金属(Cr、As、Cu、Pb)含量下的叶绿素相对含量及相关性,分析了3种经济树种对4种常见重金属元素胁迫的抗性机制。结果表明:在不同重金属含量的土壤环境中,由于重金属胁迫的复合影响,植物的叶绿素相对含量存在较显著的差异,说明土壤重金属对植物生长存在明显影响。单因子指数法和内梅罗综合评价法的计算结果表明,试验果园土壤重金属As、Cr元素综合污染等级分别为轻度污染等级和警戒线等级,而Cu、Pb元素处于安全等级。总体来看,单因子污染指数与内梅罗综合污染指数由大到小均为As、Cr、Cu、Pb。3种经济树种的叶绿素相对含量由大到小依次为李树(25.9±6.5)、桃树(24.3±7.1)、核桃树(18.55±4.8)。叶绿素相对含量与4种土壤重金属含量存在显著的负相关关系,这说明重金属胁迫抑制了植物光合作用的途径,从而降低了其光合能力,随着胁迫强度的增大,对叶绿素相对含量的抑制作用越强。3种经济树种中,核桃树对土壤重金属胁迫的抗性较强,李树次之,桃树较差。     

沙棘“生态经济育种”研究Ⅳ——干旱对沙棘杂种源库关系的生理学调节

在鄂尔多斯半干旱地区,杂交沙棘高产株的优势,表现在表型指标:新梢数、果枝数、百叶重、单叶面积、总叶面积、果实数、百果重和果产量都明显高于中、低产株。生理指标:果实脱落率最低、果/叶比系数最小、净光合效率和日进程都最高、水分利用效率也高。高产株杂种优势的实质,是能自我调节、合理分配源(叶)与库(果)间物质流和能量流的结果,显示了高产株杂种在重组基因优势上能较好的适应恶劣的生态条件。     

Plant water parameters and the remote sensing <Emphasis Type="Italic">R</Emphasis><Subscript>1300</Subscript>/<Emphasis Type="Italic">R</Emphasis><Subscript>1450</Subscript> leaf water index: controlled condition dynamics during the development of water deficit stress

Plants with different abilities for osmotic adjustment (cowpea, bean, and sugarbeet) were subjected to gradually decreasing soil water content. During the development of water deficit stress, various plant water parameters were measured to characterize their relationship to the near infrared R ₁₃₀₀/R ₁₄₅₀ leaf water index, which is based on the measurement of light reflected from leaves. In all three species, leaf water thickness (LWT), leaf cell relative water content (RWC), and overall leaf thickness remained relatively constant under moderate water deficit stress. However, at the point when plants could no longer cope with the increasing level of water deficit stress, LWT, RWC, and leaf thickness were found to decrease substantially, signaling the onset of leaf dehydration. The R ₁₃₀₀/R ₁₄₅₀ leaf water index followed the RWC very closely in cowpea and bean leaves, and with some time lag in sugarbeet leaves. The R ₁₃₀₀/R ₁₄₅₀ index may therefore be used as a feedback-signal in precision irrigation control, signaling effectively the physiological response of plants when water deficit stress becomes detrimental. RWC and the R ₁₃₀₀/R ₁₄₅₀ index were linearly correlated in cowpea and bean leaves, but not in sugarbeet leaves.     

北京市园林主要灌木单株耗水量比较研究

采用盆栽法分别对6种北京城市常用园林灌木单株的耗水规律进行研究,并对苗木在不同灌溉量处理下的耗水特性及生长表现进行研究与评价。研究结果表明:在相同自然环境条件下,6种灌木的耗水特性划分为三类:高耗水型、低耗水型、中间型。大叶黄杨(Euonymus japonicus)为高耗水型灌木,金银木(Lonicera maackii)、红瑞木(Swida alba)为低耗水型灌木,小叶黄杨(Buxus microphylla)、冬青卫矛(Euonymus kiautschovicus)、棣堂(Kerria ja-ponica)等3种灌木为耗水量适中的灌木类型;不同灌溉处理对6种灌木植物蒸腾耗水量具有显著的影响(P<0.001),随着水分胁迫的加强,6种灌木的蒸腾耗水量表现出依次减少的趋势;选取植物光合速率与单片叶面积作为衡量植物水分匮缺的两项重要指标,其中植物光合速率与灌溉量成线性相关,灌溉量越高植物光合速率越大;不同灌溉处理下的植株基本表现为灌溉量越多,植株外形越好,其中叶面积与灌溉水平之间表现明显的相关性,是体现植株水分匮缺的一个很好的指标。     

清、污水灌溉对夏玉米生长影响的田间试验研究

污水灌溉对作物生长和土壤环境的影响倍受研究人员的关注。通过在北京东郊所进行的清、污水灌溉田间试验 ,着重探讨了污灌条件下 ,不同灌水水平和施肥量对夏玉米生长和产量的影响。结果表明 ,与清水灌溉相比 ,污水灌溉 :1对夏玉米的生长发育具有一定的抑制作用 ;2对夏玉米的产量和干物质量的影响要大于对株高和叶面积指数的影响 ;3无肥处理比施肥处理的产量要高 5 .2 %。     

麦后移栽棉生育及生理特性对水分亏缺的响应

在防雨棚测坑试验条件下,研究了不同生育阶段水分亏缺对麦后移栽棉生长发育及生理特性的影响。结果表明,蕾期水分亏缺抑制了植株的正常生长发育,棉花株高、茎粗和叶面积指数等生长发育指标均随水分亏缺程度的增大而减小,而花铃期水分亏缺对其影响较小;在植株快速生长阶段,蕾铃数和叶面积指数呈现良好的对数正相关关系,决定系数达到0.90以上;不论蕾期还是花铃期,与对照处理相比,水分亏缺均显著提高了叶片可溶性糖和丙二醛(MDA)的质量分数,且随水分亏缺程度的增大而增大,进而限制了蕾铃的正常生长发育,复水后可溶性糖与MDA均降低至与对照无明显差异的程度。     

Irrigation restriction effects on water use efficiency and osmotic adjustment in Aloe Vera plants (Aloe barbadensis Miller)

Aloe barbadensis Miller, known as Aloe Vera, requires limited irrigation depending on the capacity of the soil to retain humidity, since it is a CAM species and thus naturally adapted to conditions of dryness and high temperatures. Therefore, we postulated that plants of Aloe Vera plants under conditions of water deficit should improve their water use efficiency (WUE) by performing osmotic adjustment (OA) with a temporal correlation between WUE and OA. The objective of the investigation was to determine the effect of water restriction on the WUE and OA of A. barbadensis under different water treatments. 18-month old Aloe Vera plants were cultivated in pots with a soil substrate that was a mixture of equal parts of sand and organic matter with 18% of FC and 9% of permanent wilting point. To determine the effects of the soil humidity on plant WUE and OA, four treatments were arranged in a complete random design with four repetitions; these were 100%, 75%, 50% and 25% of FC, which correspond to an evatranspiration of 11.4, 9.6, 4.0 and 1.7 L per plant, respectively. The water treatments were maintained by frequent irrigation. The following variables were determined: dry matter, leaf water potential, relative water content (RWC), amount of gel produced, sap flow, proline content, soluble and total sugars and oligo and polyfructans. Aloe Vera increased WUE with increasing water deficit; the sap flow rate decreased with water restrictions, and the plants performed osmotic adjustment by increasing the synthesis of proline, soluble and total sugars as well as the amounts of oligo and polyfructans, mainly polymers of β-(2 → 6) kestotriose, changing from the inulin type to the neofructan type. The plants most and less irrigated (100% and 25% of FC) were the groups with lowest WUE. The plants irrigated with 75% of FC presented the best WUE in terms of dry mass and amount of gel produced by a litre of supplied water.     

结合图像的叶绿素荧光动力学植物水分胁迫探测方法

为了准确、直观探测植物水分胁迫及生长状态信息,融合了叶绿素荧光动力学参数及荧光图像对不同干旱胁迫条件下的植物进行了实验观测。以460 nm蓝色LED作为激发光源,EMCCD加装690 nm带通滤光片进行荧光图像采集,对4种不同采样周期下的各1 000幅图像求每幅图的像素平均值,按时间序列绘制荧光强度,可得到信息更全面的叶绿素荧光动力学曲线,并计算得出各个动力学参数。同时,对不同时间产生的荧光图像进行降噪、乘除等运算,并用伪彩色显示,可直观分析各类因素导致的荧光分布不均匀性。对易失水叶片和非易失水叶片分别进行快速水分胁迫和缓慢水分胁迫实验,结果表明,荧光比Rfd及动力学曲线上次峰值出现的时间随着胁迫的加剧均发生相应变化,且与叶片含水率之间具有较高的拟合决定系数。因此,将叶绿素荧光动力学特征和图像信息相结合,可提高植物干旱胁迫早期预测的准确度和直观性,为现场连续无损地监测植物生长状态、各类胁迫信息、病虫害检测等提供了一种快速的遥测手段。     

Chloride accumulation and partitioning in Barley as affected by differential root and foliar salt absorption under saline sprinkler irrigation

Barley is a crop that has been classified as tolerant to soil salinity, but under sprinkler irrigation with saline water it can readily absorb salts through its leaves and develop injury. Experiments using a triple-line-source sprinkler system were conducted on barley between 1989 and 1991 to determine: (1) the specific effects of foliage wetting on the mass of different shoot components; (2) the relative contribution of root and foliar absorption processes to foliar Cl accumulation; and (3) the extent by which these processes affect Cl partitioning in the shoot at the end of the season. Some plants were covered with plastic during the irrigation process to prevent foliar wetting while others remained uncovered. Salinity affected the partitioning of dry matter in the shoots regardless of whether plants were covered during the irrigation process. The organs associated with reproduction, e.g., heads and peduncles, comprised a larger fraction of the total shoot biomass under high salinity than under low salinity, indicating that plants under salinity stress were able to redistribute their dry matter to favor reproductive growth. The Cl concentration of the young leaves sampled from uncovered plants was linearly related (i.e., r ²>0.71) to the Cl concentration of the irrigation water. Equivalent leaves from covered plants also contained a substantial amount of Cl but concentrations were weakly correlated (i.e., r ²<-0.41) with the concentration of Cl in the irrigation water. At low salinity, there were no differences in leaf Cl concentrations between covered and uncovered treatments. In young leaves, differences between these treatments progressively increased with increasing salinity, indicating that the relative contribution of Cl in the leaf from foliar absorbed salts increased with increasing Cl in the irrigation water. Only in the youngest leaves sampled at the end of the season from plants grown at high salinity was the Cl concentration in uncovered plants (foliar plus root-absorbed Cl) found to be more than twice that in covered plants (only root-absorbed Cl) indicating that most of the Cl in young leaves originated from foliar absorption. In addition, only in the youngest leaves (e.g., flag leaves) was the slope of the relationship between leaf-Cl concentration and Cl concentration of the sprinkling water of uncovered plants more than twice that of covered plants, also indicating that foliar-Cl absorption was more substantial than root-Cl absorption. At high salinity, the difference in leaf Cl concentration between covered and uncovered plants was maximum in the youngest leaf (flag leaf), but differences became progressively smaller with increasing leaf age until ultimately concentrations of chloride in leaves older than the flag leaf-2 were highest in covered plants. In older tissue, it was difficult to distinguish which process, foliar or root absorption, was most responsible for leaf-Cl accumulation. These processes may not be entirely independent of one another and much of the Cl in the oldest leaves of uncovered plants could have been derived from foliar sources during the first month of sprinkling, reaching maximal levels, and thereby restricting root-absorbed Cl. Furthermore, since these leaves at the end of the season are more injured and drier than those from covered plants, late-season sprinkler irrigations may have been responsible for leaching some of the Cl out of these necrotic leaves.     

A reexamination of the crop water stress index

Summary Hand-held infrared radiometers, developed during the past decade, have extended the measurement of plant canopy temperatures from individual leaves to entire plant canopies. Canopy temperatures are determined by the water status of the plants and by ambient meteorological conditions. The crop water stress index (CWSI) combines these factors and yields a measure of plant water stress. Two forms of the index have been proposed, an empirical approach as reported by Idso et al. (1981), and a theoretical approach reported by Jackson et al. (1981). Because it is simple and requires only three variables to be measured, the empirical approach has received much attention in the literature. It has, however received some criticism concerning its inability to account for temperature changes due to radiation and windspeed. The theoretical method is more complicated in that it requires these two additional variables to be measured, and the evaluation of an aerodynamic resistance, but it will account for differences in radiation and windspeed. This report reexamines the theoretical approach and proposes a method for estimating an aerodynamic resistance applicable to a plant canopy. A brief history of plant temperature measurements is given and the theoretical basis for the CWSI reviewed.