Relationship between chlorophyll meter readings and nitrogen in poinsettia leaves

Chlorophyll meters are used for non-destructive estimation of leaf nitrogen (N). The objective of this study was to evaluate the readings with several chlorophyll meters (SPAD-502, atLEAF, and CCM-300), different sampling sites on leaves, number of leaves used for sampling, and different types of leaf N sampling on estimation of N in leaves of potted poinsettia (Euphorbia pulcherrima) “Prestige Red.” Results showed that all meters gave readings that were correlated for N determination and also were correlated with each other. SPAD and atLEAF showed interaction between different N treatments and different sampling sites on the leaves, while CCM readings were affected by different sampling sites on the leaf. atLEAF readings showed interaction between number of leaves sampled and different N treatments. Thus, during sensor-based leaf N estimation, sampling site on leaf, number of leaves sampled, and stage of plant development should be considered to minimize error.     

Changes in nitrogen concentrations of corn leaves near silking time

Abstract

Precision in tissue testing to characterize the nitrogen (N) status of corn (Zea mays L.) is more important than ever before because of current concerns about the effects of N fertilizers on environmental quality. This study was conducted to assess the importance of errors associated with differences in physiological age of plants when plots receiving various rates of N fertilizer are sampled at a single time during the period of silk emergence. Ear leaf samples were collected at four times between early and late silking from five experiments at different locations in Iowa during 1987. Nitrogen deficiencies delayed silking by less than 2 days. After adjustments for delays in the onset of silking, the rates of silk emergence were similar for all N rates. Rapid rates of silk emergence indicated that it is practically impossible to sample leaves at a specific silking percentage such as 50 or 75%. Leaf N concentrations were not significantly influenced by time of sampling during the period of silk emergence. However, variability in N concentrations during the sampling period indicated that the practice of sampling leaves from all plots within a site at one time is more appropriate than the practice of sampling plots at the same percentage silking.     

玉米生理年龄的差异对N缺乏诊断的影响

Many studies have shown that chlorophyll meter readings （CMRs） can be used to diagnose deficiencies of nitrogen （N） during the growth of corn （Zea mays L.） in small-plot trials, but there is need to address additional problems encountered when diagnoses are made in fields of the size managed in production agriculture. A noteworthy difference between smallplot trials and production agriculture is the extent to which the effects of N are confounded with the effects of other factors such as tillage, landscape, soil organic matter and moisture content. We illustrate how some of these factors can cause differences in the physiological age of plants and introduce errors in the diagnoses of N deficiencies. We suggest methods （measuring the height to the youngest leaf collar and assigning leaf numbers by using the first leaf with pubescence and the ear leaf as references to identify growth stages） for minimizing these errors. The simplified method of growth stage identification can be used to select appropriate plants and leaves for making diagnoses in fields and to distinguish the effects of N from the effects of other factors that influence plant growth.     

Within plot variability in available soil mineral nitrogen in relation to leaf greenness and yield

Abstract

Available soil mineral nitrogen (N) varies both temporally and spatially. These variations affect field‐scale N‐use efficiency. A field study was conducted for three years to investigate spatial variability in available soil mineral N within uniform research plots in relation to leaf greenness or chlorophyll content (plant N sufficiency) and yield. Variations within the plot in available soil mineral N sampled at the 6‐ligule stage was related to N fertility: the higher the fertilizer N levels, the higher the variability. The standard deviation for the 200 kg N ha^‐1 treatment was up to five times higher than the unfertilized control treatment. The nitrate (NO₃)‐N accounted for 70 to 80% of soil mineral N in fertilized plots compared to 50 to 60% in unfertilized control plots. The variability in grain yield of individual maize (Zea mays L.) plants within a plot was inversely related to soil N fertility: the higher the fertilizer N levels, the lower the yield variability (at 100 or 200 kg N ha^‐1, yield ranged from 97 to 148 g plant¹, or 10% CV within ayear compared to ranges from 0 to 82, or 50% CV in the same year at 0 kg N ha^‐1). On an individual plant basis, chlorophyll content from the 6‐ligule stage through the growing season generally showed much smaller CV's, but had a similar trend to variations in yield. Leaf greenness from 6‐ligule stage to silking was significantly correlated with harvest yield (r>0.60, P<0.01), and both also correlated with available soil mineral N, though to a lesser degree (r>0.36). The number of fully expanded leaves prior to silking differentiated N treatments better than did single leaf chlorophyll measurements with higher yields associated with more rapid vegetative development. Our data suggest that multiple core samples are required to estimate available soil mineral N, particularly in fertilized plots that have greater spatial variability. Variability of plant‐based measures, such as chlorophyll content, could be used as an indicator of relative plant N sufficiency at early growth stages as spatial variability declined with higher soil N fertility.     

Relationship between spectroradiometric and chlorophyll measurements in green beans

Abstract

Individual linear relationships were established between total chlorophyll and SPAD readings, while a unique linear relationship was determined between chlorophyll a and SPAD readings for three green bean cultivars (Phaseolus vulgaris L.). Greening of young expanding leaves at the top of the canopy of all cultivars was associated with low transmittance and reflectance in the PAR region. However, transmittance and reflectance responses of young leaves were different between cultivars. Leaf senescence was associated with an increase in transmittance in the PAR region, but no changes were obtained in the Near‐InfraRed region (NIR). Top young leaves and middle canopy fully expanded leaves of the three green bean cultivars presented a similar transmittance in the Visible and NIR regions. Although the correlations between reflectance and SPAD values of young expanding leaves and that for the inverse‐log reflectance were relatively weaker than that obtained for transmittance either for the same leaf age or different leaf ages, the results suggest that the SPAD meter may be used to provide a rapid estimate of leaf transmittance and reflectance in the field.     

Use of a hand‐held chlorophyll meter in winter wheat: Evaluation of different measuring positions on the leaves

A portable chlorophyll meter (Minolta SPAD‐502) was used to assess the nitrogen status of winter wheat (Triticum aestivum L.) in two fertilizer trials at Apelsvoll Research Centre, located in south‐east Norway. The midpoint of the last fully developed leaf was found to be the best position on the winter wheat plant on which to take chlorophyll meter readings. This conclusion was reached after examination of the relationships between soil‐plant analyses development (SPAD) readings taken at different positions on the plant and leaf nitrogen concentration, grain yield and grain protein content. Emphasis was also laid on finding a measuring position that was convenient from a practical point of view. The relationships between chlorophyll meter readings and the parameters investigated were better at Zadoks growth stage (GS) 49 than earlier in the season at GS 31.     

Ozone effects on dry matter partitioning and chlorophyll fluorescence during plant development of wheat

In closed-chamber fumigation experiments dry matter partitioning and chlorophyll fluorescence of wheat were studied, analysing the effects of ozone during different stages of plant development. Ozone causes enhanced leaf senescence, leading to a loss of green leaf area and, consequently to a decreased supply of assimilates, affecting (in increasing order of severeness) stem, ear and grain productivity because of reduced storage pools for translocation. Leaves of plants before shooting stage were most sensitive but the lack of green leaf area after ear emergence had the most pronounced effects on grain yield.Measurements of photochemical capacity showed that evidence for negative ozone effects could be found in changes of chlorophyll fluorescence parameters in leaf sections not yet showing visible ozone injury. Negative effects on photosynthesis were more distinct with increasing accumulated ozone dose, with increasing age of leaf tissue and with increasing ozone sensitivity of the cultivar. The changes in chlorophyll fluorescence are most likely to be explained by a decreased pool size of plastoquinones caused by ozone.     

Assessing Variations in SPAD‐502 Chlorophyll Meter Measurements and Their Relationships with Nutrient Content of Trembling Aspen Foliage

Abstract

The relative chlorophyll content in leaves estimated by the SPAD‐502 chlorophyll meter can be an efficient way to evaluate plant nitrogen (N) status in many crops and some tree species. In this study, the SPAD meter was used to look for relationships between relative leaf chlorophyll content and leaf nutrient concentration in trembling aspen. The variations in leaf chlorophyll measurements were also evaluated by using three sampling times and three measurement techniques. Hypothetical experimental designs were created to achieve better design efficiency. The best representation of overall leaf chlorophyll was found when six SPAD readings were taken at different locations on each leaf. There was a positive correlation between overall leaf N and estimated chlorophyll content, especially in the top part of the trees. Overall, this study suggested that the SPAD meter can give an estimation of trembling aspen nutritional status, especially if the differential partitioning of N within trees is considered.     

Determination of cotton nitrogen status with a handheld chlorophyll meter

The ability of a hand‐held chlorophyll meter (SPAD‐502 Chlorophyll Meter³, Minolta Camera Co., Ltd., Japan) to determine the N status of cotton (Gossypium hirsutum L.) was studied at field sites in Alabama and Missouri. Meter readings on the uppermost fully‐expanded leaf were compared to leaf‐blade N and petiole NO₃‐N at first square, first bloom and midbloom as to their seed cotton yield predictive capability. Nitrogen was applied at rates of 0, 45, 90, 135, 180 and 225 kg ha^‐1 to establish a range of cotton chlorophyll levels, tissue N concentrations, and seed cotton yields. A typical curvilinear cotton yield response to N fertilizer was observed in Alabama experiments.

Because of adverse weather conditions, cotton yield in Missouri experiments did not respond to N. Chlorophyll meter readings were significantly correlated to leaf‐blade N concentration at all three stages of growth for all experiments. In Alabama, chlorophyll meter readings compared favorably to leaf‐blade N and petiole NO₃‐N with respect to their seed cotton yield predictive capability at all three stages of growth. It appears that hand‐held chlorophyll meters would be as reliable as leaf‐blade N and petiole NO₃‐N for predicting supplemental N fertilization requirements of cotton. However, more research will be required prior to use of chlorophyll meter readings for routine cotton‐N recommendation purposes.     

Effect of p-chlorophenyl dimethyl urea on the degradation of chlorophyll in detached rice leaf in the light

It was observed previously that, when a fully developed leaf of the rice plant (Oryza sativa) was detached and kept in the light, more rapid loss of chlorophyll took place than in the dark during their incubation. Since this had been considered to be associated with photosynthesis, the effects of CMU (p-chlorophenyl dimethyl urea) and other compounds on the degradation of chlorophyll were studied. CMU had a significant effect in retarding the degradation of chlorophyll in the light irrespective of the presence of sucrose, whereas monoiodo acetic acid was far less effective. The degradation of chlorophyll was greatly promoted, especially in the light, when a detached leaf was kept in oxygen gas, but was delayed in nitrogen gas.

Electron microscopic observation showed that grana fret-work system and chlorophyll membrane were maintained in a healthy condition for the first few days during treatment with CMU. But they were completely degraded without CMU, and the disorganization of chloroplasts was accompanied by a rapid degradation of chlorophyll. It was assumed that oxygen evolved in photosynthetic reaction causes light-induced degradation of chlorophyll, and CMU represses degradation by inhibiting oxygen evolution in the light reaction of photosynthesis. A suggestion was made as to the scheme of light-induced degradation of chlorophyll relative to photosynthetic reaction and the mode of action of CMU.     

The influence of nitrogen nutrition on plant response to greenbug infestation 1

The influence of nitrogen nutrition and greenbug (Schizaphis graminum Rondani) infestation on growth, chlorophyll content, soluble amino acids, and soluble protein of barley plants (Hordeum vulgare L.) was studied in growth chamber experiments. Plants were grown for 21 days using complete or minus nitrogen nutrient solution. First leaves were then fitted with cages containing eight apterous adult greenbugs. After 7 days, the greenbugs were removed and the plants harvested. The plants given complete nutrient solution grew more rapidly than those given minus nitrogen. Plants grown with minus nitrogen had fewer greenbugs per plant but had much higher numbers of greenbugs per square centimeter of total plant leaf area than plants given complete nutrient solution. All leaves of infested plants grown with minus nitrogen had decreased dry weight, decreased chlorophyll, and increased soluble amino acids when compared with minus nitrogen uninfested plants. Infestation of first leaves of plants grown on complete nutrient solution increased soluble amino acids in all leaves. However, there was little change in the dry weight or chlorophyll level in leaves other than the first leaf. It is concluded that adequate nitrogen nutrition produces plants that can better withstand localized greenbug feeding damage than plants deficient in nitrogen.     

Multilayer Perceptron Neural Network Approach to Estimate Chlorophyll Concentration Index of Lettuce (Lactuca sativa L.)

Nitrogen is an essential nutrient for greenhouse-grown lettuce (Lactuca sativa L.); however, excessive nutrient availability causes disease and detrimental effects on the leaf and root development. In this study, nitrogen content of the lettuce leaves was estimated by determining the chlorophyll concentrations of the leaves using image processing technique. The Hoagland solution was used as a fertilizer in five different doses (control, quarter of the solution, half of the solution, standard solution, and two times more of the solution). Multilayer perceptron neural network (MLPNN) model was developed based on the red, green, and blue components of the color image captured to estimate chlorophyll content and chlorophyll concentration index (SPAD values). According to the obtained results, the MLPNN model was capable of estimating the lettuce leaf chlorophyll content with a reasonable accuracy. The coefficient of determination was 0.98, and mean square error was 0.006 in validation process.     

一个新的水稻白化转绿突变体G_9的特性研究

利用60Coγ射线离体诱变籼稻光温敏核不育系广占63S,获得一个新的白化转绿突变体G9。该突变体从出苗到4叶1心期,叶色表现出明显的白化现象,从第4新生叶开始,新老叶片开始转为正常绿色,到6叶1心时秧苗完全转绿;在2叶期,其叶片叶绿素含量极少,随着叶色转绿,叶绿素含量开始显著增加,4叶期约为亲本的1/4,而至6叶期,突变体和亲本的总叶绿素含量无显著差异。遗传分析表明,该突变体的叶色白化转绿变异受一对隐性核基因控制。用144个SSR标记分析了突变体和亲本的SSR组型,未发现两者之间存在差异,说明该突变体确系诱发突变而来,两者存在很好的近等基因特性。对G9/AM6的F4代的农艺性状进行比较,发现突变基因对幼苗总根数、白根数、最长根长度和苗期株高均有显著影响;对植株分蘖能力、成熟期株高、单穗实粒数、结实率、千粒重、单株产量均有显著影响,而对有效穗数无明显影响。     

Comparison of Various Analysis Methods for Determination of Iron Chlorosis in Apple Trees

Abstract

The objective of this study was to compare iron (Fe) concentrations (mg kg^?1) of the leaves measured by different methods and to determine the most suitable method to be used in evaluation of iron chlorosis in apple trees. For this purpose, green and chlorotic leaves were collected from 76 apple orchards in 1998 and 1999. Iron concentrations (mg kg^?1) of dried leaf samples were measured with 4 different methods, 1 N HCl (Method 1), 0.1 N HCl (Method 2), 0.005 M DTPA (Method 3), and 1.5% o-phenanthroline (Method 4). Total Fe concentrations (mg kg^?1) of dried leaf samples were also analyzed. Total chlorophyll and peroxidase enzyme activity in fresh leaf samples were measured. The total chlorophyll, peroxidase enzyme activity, Fe concentrations (mg kg^?1) determined by Method 1, Method 3, Method 4, and total Fe concentrations (mg kg^?1) of green leaves were higher than those of chlorotic leaves. On the other hand, no significant difference was found between Fe concentrations (mg kg^?1) of green and chlorotic leaves, measured with Method 2. Significant relationship observed amongst chlorophyll concentrations, peroxidase enzyme activity, and Fe concentrations (mg kg^?1) of samples suggests that 1 N HCl method was the most suitable method amongst the methods used in this study for apple trees.     

施氮量对穗期高温胁迫下玉米叶片光合生理及产量的影响

【目的】探究不同施氮量对玉米穗期高温胁迫下光合生理及产量的影响,为合理施氮实现玉米抗逆稳产提供理论依据。【方法】2020—2021年开展人工模拟高温田间试验。以耐热型品种郑单958 (Zhengdan 958)和热敏感型品种先玉335 (Xianyu 335)为材料;设置3个施氮量,分别为低氮(N 90 kg/hm2,N90)、中氮(N180 kg/hm2,N180)和高氮(N 270 kg/hm2,N270)。在玉米第11片叶展开期至抽雄期进行高温处理(HT),分别持续12天(2020年)和9天(2021年),以田间自然生长的植株为对照(CK),处理期间高温和对照的日最高温度均值分别为41.9℃、35.9℃(2020年)和40.8℃、37.7℃(2021年),昼夜温差均值分别为19.3℃、13.0℃(2020年)和18.1℃、14.8℃(2021年),调查两个品种穗位叶的光合色素含量、光合参数、叶绿素荧光参数、光合酶活性、籽粒产量及产量构成因素,分析温度、品种和施氮量三者之间的互作效应。【结果】1)高温胁迫提高了两个玉米品种穗位叶的磷酸烯醇式丙酮酸羧化酶(PEPCase)和核酮糖-1...     

施氮对半湿润农田夏玉米冠层氮素及叶绿素相对值(SPAD值)垂直分布的影响

以半湿润地区土垫旱耕人为土为供试土壤,采用田问试验,研究了不同施氮水平下夏玉米(Zea maysL.)拔节期、灌浆期和成熟期3个生育期冠层叶片氮素、叶绿素相对值(SPAt)值)的垂直分布规律及其差异;同时对各层叶片含氮量、SPAR值与施氮量进行相关分析.结果表明,在各生育期不同叶层叶片含氮量按上、中、下层顺序呈明显递减规律,从全生育期不同施氮处理看,上层比中层增加6.64%,中层比下层增加5.18%.随施氮量增加,中上层叶片含氮量差异增大,中下层叶片含氮量差异减小.冠层内叶片SPAD值垂直分布规律与叶片含氮量分布规律相类似.相关分析表明,全生育期各层叶片SPAD值与叶片含氮量呈极显著线性正相关关系(R=0.503**).进一步分析发现,各层叶片SPAD值,叶片含氮量与施氮量的相关性以上层叶关系最为密切,揭示了夏玉米氮素营养诊断的较好叶片是上层叶位.     

有机肥和化肥对烟叶气体交换、叶绿素荧光特性及叶绿体超微结构的影响

【目的】本文以烤烟K326为材料,探讨了在不同叶龄时期有机肥与化肥在烟叶气体交换参数、叶绿素荧光特性、叶绿素含量及叶绿体超微结构等方面的差异,以期从光能利用(宏观)及叶绿体超微结构(微观)方面,揭示两种肥料配比对烟叶光合作用的影响机制,同时为探索烟叶高产优质栽培模式提供理论依据。【方法】以蛭石为栽培基质进行盆栽试验。设施用烤烟专用有机肥(N∶P2O5∶K2O为9∶9∶10,有机质≥70%,中、微量元素≥12%)和施用普通尿素两个处理。烟草为工厂化无毒育秧苗,叶龄(叶龄从叶片长约2 cm时算起)15天、30天、45天、60天和75天取样或测定自上而下第6~8片叶。用Li-6400(美国)便携式光合仪测定烟叶的净光合速率,蒸腾作用与气孔导度。使用M系列调制叶绿素荧光成像系统Maxi-Imaging-PAM(德国)测定叶绿素荧光参数。用C-7000透射电子显微镜观测叶绿体超微结构并拍照,用软件Auto CAD 2004计算淀粉颗粒在叶绿体中所占的相对面积比Ra,叶绿体基粒片层的统计方法据Goodenough等改进的Teichler-Zallen法。【结果】有机肥对烟叶叶绿素含量及光合速率的影响显著,在叶龄60天时,其叶绿素含量比普通化肥高136.1%;在叶龄75天时,其烟叶净光合速率、气孔导度及蒸腾速率分别比普通化肥处理高135.3%、84.5%和51.3%,叶绿素荧光参数Y[Ⅱ]和q L分别比普通化肥处理高22.2%和39.5%,Fv/Fm在叶龄60天时比普通化肥处理高18.7%,而NPQ值在叶龄45天时普通化肥比有机肥处理高23.3%。叶绿体内孕育的淀粉粒随叶龄的增加而逐渐膨大,期间伴随着淀粉粒在叶绿体中所占的面积比例(Ra值)越来越大,两处理Ra值差异明显,尤其是在叶龄45天时,化肥栽培下的烟叶Ra值比有机肥栽培高31.8%。有机肥处理的叶绿体呈梭形,长宽比大,而普通化肥种植的叶绿体形态近圆形,长宽比小。【结论】施用有机肥可显著提高烟叶叶绿素含量及光合速率,且随叶龄的增加,有机肥的作用效果日趋明显。叶绿素荧光参数的差异表明,增施生物有机肥可延缓烟株衰老、提高烟叶光能利用效率。两种施肥方式下,淀粉颗粒Ra值的差异不能说明施用化肥可提高烟叶合成淀粉的能力。与普通化肥处理下的烟叶相比,有机肥可显著提高叶绿体基粒垛叠数大于10的片层占基粒垛叠片层总数的百分比。     

氮素对玉米灌浆期叶片光合性能的影响

以玉米自交系齐319(Q319)为材料,采用单株盆栽种植方式,借助叶绿素荧光快速诱导动力学曲线和820 nm光吸收曲线,研究了氮素对玉米灌浆期叶片光合性能的影响。2年研究结果表明,在本试验条件下,氮素对Q319灌浆期叶片叶绿素含量无明显提高作用,但其净光合速率(Pn)和单株干物质积累量、子粒产量显著增加。JIP-test分析表明,氮素显著提高了叶片光系统Ⅱ(PSⅡ)反应中心电子供体侧和受体侧性能;显著提高了Q319 PSⅡ反应中心电子受体侧之后的电子传递链性能,增强了电子由PSⅡ向PSⅠ的分配,从而显著地提高了PSⅡ与PSⅠ之间的协调性。可以认为,施氮后灌浆期叶片叶绿素含量的变化不是Pn提高的主要原因,而两个光系统性能的改善及二者间协调性的提高增强了光合电子传递链的性能是灌浆期Pn升高与成熟期产量增加的主要原因。     

Development of Critical Values for the Leaf Color Chart,SPAD and Fieldscout CM 1000 for Fixed Time Adjustable Nitrogen Management in Aromatic Hybrid Rice (Oryza sativa L.)

The nitrogen (N) requirement of hybrid rice is generally greater than in conventional rice varieties. Recommendations for N monitoring at regular intervals of 7–10 days through leaf greenness are available, but farmers are accustomed to apply fertilizer N at selected growth stages only. An inexpensive leaf color chart (LCC) and nondestructive chlorophyll meters were evaluated for site-specific N management strategy in world’s first aromatic rice hybrid PRH-10 at the Indian Agricultural Research Institute, New Delhi. Two field experiments were conducted on PRH-10 with four levels of N (0, 70, 140, and 210 kg ha^?1) during June–October of 2010 and 2011 to determine the LCC, soil–plant analysis development (SPAD), and Fieldscout CM 1000 (CM 1000) values for achieving economic optimum grain yield at three critical growth stages (tillering, panicle initiation, and flowering). Quadratic regression between N levels and grain yield were used to determine economic optimum grain yield (6427 kg ha^?1 in 2010 and 6399 kg ha^?1 in 2011) corresponding to optimum economical dose of 151 kg N ha^?1 (2010) and 144 kg N ha^?1 (2011). Nitrogen concentration in fully expanded youngest leaf correlated significantly (P < 0.01) and positively with LCC score, SPAD value, CM 1000 value, and total chlorophyll concentration at tillering, panicle initiation, and flowering for both years. The critical LCC score, SPAD, CM 1000 values, chlorophyll concentration, and leaf N concentration obtained were at tillering 4.4, 42.3, 285, and 2.16 mg g^?1 fresh weight and 3.29%; at panicle initiation 4.4, 43.0, 276, and 2.16 mg g^?1 fresh weight and 3.02%; and at flowering 4.5, 41.7, 270, and 2.05 mg g^?1 fresh weight and 2.83%, respectively. Corrective N application should be done when observed leaf N indicator values at a particular growth stage reach or go below the critical values.