Detection of Chlorophyll Breakdown Products in the Senescent Leaves of Higher Plants

The determination of intermediary breakdown products of chlorophyllsin senescent leaves of higher plants was performed by high-performanceliquid chromatographic technique that had been newly developedto separate and identify the oxidation products of chlorophylls,in particular monopyrrole derivatives [Suzuki et al. (1999)J. Chromatogr. A 839: 85]. In six plants tested, degradationproducts were detected only in the senescent leaves of plantsincluding barley (Hordeum vulgare), except for radish (Raphanussativus), in which they were found both in pre- and senescentcotyledons. In the senescent cotyledons of barley, three degradationproducts, hematinic acid, methyl ethyl maleimide, and the putativedegraded C-E-ring derivative, methyl vinyl maleimide dialdehyde,were detected. In addition to above three products, methyl vinylmaleimide was also found in both pre- and senescent cotyledonsof radish. These products decreased during senescence with anaccumulation of unknown compound(s), probably degraded monopyrrolederivatives. The degradation process and amounts of breakdownproducts of chlorophylls depend largely on plant species andvary with length of senescence. To conclude, it is likely thatchlorophylls are degraded into low-molecular-weight hydrolyticcompounds through monopyrroles. (Received March 10, 1999; Accepted June 11, 1999)     

Correlation between Chlorophyll and Chlorogenic Acid Content in Tobacco Leaves

Developmental stages of tobacco (Nicotiana tabacum L. cv. Burley 21) flower and capsule were correlated with tissue contents of polyphenols and activities of phenylalanine ammonialyase, polyphenoloxidase, and peroxidase. Chlorogenic acid, scopolin, and scopoletin were present in most tissues, whereas rutin and two dihydroxyphenolic glycosides concentrated primarily in the corolla and placenta, respectively. Ovules contained only chlorogenic acid. As development progressed, polyphenols accounted for nearly 15% of the dry weight in the green capsule of field-grown plants. Fertilization triggered a rapid increase of chlorogenic acid in the ovary. When l-phenylalanine-U-¹⁴C was fed to the detached green capsules and capsule parts, an incorporation of radioactivity into chlorogenic acid and dihydroxyphenolic glycosides occurred which suggested in situ synthesis of these compounds. This was subtantiated by a positive correlation between phenylalanine ammonia-lyase activity and polyphenol accumulation. High polyphenoloxidase activity was associated mainly with the ovary, whereas peroxidase activity was maximal during senescence of all tissues. Polyacrylamide gel slab electrophoresis revealed five cathodic bands and one diffuse zone with poly-phenoloxidase activity in flower extracts. Two anodic poly-phenoloxidase isozymes appeared only in the fertilized ovary. Among 17 peroxidase isozymes, six cathodic forms were present throughout floral development, and the anodic ones increased in number and activity at the later stages of capsule growth.     

Relation Between the Chlorophyll Content and Paleness of Gibberellic Acid-Treated Leaves

The rate of chlorophyll synthesis as a function of lime was examined in plants of Hordeum vitlgare L. cultivated in Knop solution containing 1 mg/1 GA₃. The action of concentration on the relations of chlorophyll components was investigated in GA₃ solutions of five different concentrations. The relations of total chlorophyll contents, including those of the a and b components, were determined from ethanol and aqueous acetone extract at various periods of treatment, at the same moment but with different concentrations of GA₃. A significant difference is noted between the chlorophyll contents of the GA₃ treated plants and those of the control. The chlorophyll contents of treated plants are decreasing. The difference increases with raising GA₃ concentration. The components were separated on thin layer with the partition method, and the spots were eluted. The density was measured with a spectrophotometer. Among the yellow components in the treated plants, the carotenes (α and β carotenes) increase as compared with the control plants. The total quantity of xanthophylls (lutein, zeaxanthine, lutein-5, 6-epoxide, violaxanthine and neoxanthine) almost equals the xanthophyll amount in the control plants; there is no significant difference. The paleness of leaves treated with GA₃ is provoked by the quantitative change of pigment components; the chlorophylls o and b decrease, the xanthophylls remain unchanged and the carotenes increase.     

Variation in Chlorophyll A Content and Stability in Wheat Flag Leaves

Chlorophyll a content in segments of flag leaves from 19 wheatvarieties excised at ear emergence was shown to vary by a factorof 2.3. Chlorophyll stability (expressed as the percentage ofchlorophyll remaining in the segments after 4 days senescencein moist boxes at 20 °C in the dark) varied by a factorof 8.5. Variation in these parameters between varieties appearedto be independent. Five of these varieties, representing the extremes, were furthertested at three nutrient levels, and under three light/temperatureregimes. Whilst lower leaf canopy senescence was greater atlow nutrient levels, flag leaf chlorophyll content actuallyincreased slightly, stability remaining fairly constant. Incontrast, as light intensity improved, chlorophyll content increasedmarkedly, with a consequent slight non-significant decreasein stability. Testing the F₁ progeny of a partial diallel involving four ofthe above varieties showed that the mean chlorophyll content,and stability, of the parents followed the same ranking as theprogeny to which they contributed. This suggests heritable controlof the parameters measured. Some implications of these resultsin breeding for resistance to senescence are discussed.     

Phytochrome Control of Chlorophyll Content in Mature Attached Leaves of Petunia axillaris

Petunia axillaris plants were grown under white light (photoperiod10 h). Pulses of end-of-day far-red light, but not red lightat the end of the day slowed down the accumulation of chlorophyllin expanding, greening leaves and reduced chlorophyll contentin mature leaves. The chlorophyll a / b ratio was unaffected.Low phytochrome photoequilibria reduced chlorophyll contentin mature leaves without affecting leaf area or d. wt. Thiseffect occurred even before senescence was triggered in thecontrol plants having high phytochrome photoequilibria     

An Algorithm for Estimating Chlorophyll Content in Leaves Using a Video Camera

Plant leaf colour is commonly used as an index for nutrientdiagnosis. We have developed a low-cost diagnostic method thatis easy to use to assess the nutrient status of plants, basedon the estimation of chlorophyll content of leaves using a portablecolour video camera and a personal computer. Relationships betweenchlorophyll content and various functions derived from red,green and blue wavelengths are examined. Although red-blue andgreen-blue wavelengths show the highest correlation with chlorophyllcontent under a limited range of meteorological conditions,the normalized difference (red-blue)/(red+blue) is the mostapplicable function which can use data collected under differentmeteorological conditions. The accuracy in estimating chlorophyllcontent from video images could be improved by correcting withsolar radiation data. It is shown that, for practical purposes,the chlorophyll content of leaves can be estimated with sufficientaccuracy using a portable video camera.Copyright 1998 Annalsof Botany Company Chlorophyll content; leaf colour; video camera; image processing; nutrient diagnosis.     

Pathways of Carbohydrate Catabolism in Senescent and Non-senescent Tobacco Leaves

The pathway (s) of glucose degradation in detached senescent and non-senescent tobacco leaves from plants approximately 100 days old were studied utilizing‘Relabeled carbohydrates. Comparable samples of each tissue were allowed to metabolize glucose-1- and glucose-6-¹⁴C and C₆/C₁ ratios were computed from the radioactivity of ¹⁴CO₂ collected. Two methods of calculation were compared. Hexose monophosphate pathway activity was also compared in both ages of tissue by measuring ¹⁴CO₂ respired from substrate ribose-1-, xylose-1- and gluconic acid-6-¹⁴C. The results indicate that the hexose monophosphate pathway accounts for approximately 25 percent of the respired CO₂ in both senescent and non-senescent tissues. Both types of tissue were equally efficient in degrading HMP shunt intermediates to CO₂.     

Physiological Properties of Abscission Accelerator from Senescent Leaves

A substance which is not abscisic acid accelerates leaf abscission by regulating ethylene production.     

The Effect of Diuron and 5-Aminolevulinic Acid on the Maintenance of Stable Chlorophyll Content in Greening Barley Leaves

Chlorophyll (Chl) accumulation and delayed luminescence of PSII were compared in greening barley leaves pretreated and untreated with diuron (DCMU) in the etiolated state, and reactions of two photosystems were studied in the plastids isolated from the pretreated and untreated leaves. The effect of treatment in light of post-etiolated leaves after 40-h illumination with 5-aminolevulinic acid (ALA), on the content of Chl and its precursor, protochlorophyllide (PChld) was also studied. The pretreatment of etiolated leaves with DCMU did not affect the rate of greening and the stable level of Chl content in barley. ALA, when introduced to leaves after the termination of Chl accumulation, increased PChld, but not Chl level. We suppose that the primary cause of greening cessation in etiolated leaves is the inhibition and cessation of the synthesis of apoproteins of pigment–protein complexes. The exhaustion of binding sites for newly synthesized Chl molecules leads to their retention in the so-called retroinhibitory pool of Chl, thus resulting in the inhibition of ALA synthesis by a negative feedback mechanism.     

Seasonal Dynamics of the Chlorophyll and Carotenoid Content in the Leaves of Steppe and Forest Plants on Species and Community Level

Russian Journal of Plant Physiology - The content of chlorophylls (Сhl) a and b and carotenoids (Сar) during the growing season was studied in the leaves of 31 species of steppe and...     

Changes in the Chlorophyll Content and Cytokinin Levels in the Top Three Leaves of New Plant Type Rice During Grain Filling

This paper reports the ways that the differences in leaf senescence are related to grain filling, grain yield, and the dynamics of cytokinins (CKs) in the top three leaves of four field-grown new plant type (NPT) rice, a tropical japonica developed at the International Rice Research Institute, Philippines, to increase the yield potential of rice. The chlorophyll content in leaves decreased from flowering to maturity in all the NPT lines, whereas the grain filling percentage was higher in the fast-senescing NPT line than in slow-senescing NPT line. Grain yield was positively correlated with senescence in the flag leaf. Rapid changes in the CK levels were recorded in the leaves of the fast-senescing line, whereas the CK levels were relatively stable in leaves of the slow-senescing line, suggesting that the dynamics of CKs in the fast-senescing line are vital for fast senescence. There were no significant changes in bioactive CKs, CK O-glucosides (storage CKs), and cis-zeatin derivatives in different leaves of the slow-senescing NPT line between 0 and 3 weeks after flowering, suggesting that the content of these CKs is relatively stable during grain filling. A progressive increase in levels of bioactive CKs was positively correlated with gradual accumulation of CK N-glucosides (inactive CKs) in the top three leaves of the slow-senescing NPT line, whereas the decrease of bioactive CKs in the flag leaf of the fast-senescing line was accompanied by accumulation of CK O-glucosides. These results suggest that there is a higher rate of biosynthesis and/or import of bioactive CKs as well as their turnover which may favor delay of leaf senescence in the slow-senescing NPT line.     

Effect of Gibberellic Acid on Growth, Gibberellin Content, and Chlorophyll Content of Leaves of Potato (Solanum tuberosum)

Spraying potato plants with a solution of gibberellic acid (GA)when the 15th leaf was emerging increased the area of this leafand its total gibberellin content, assayed by dwarf French beanleaf disks. GA, assayed by lettuce hypocotyls, was not detectedin leaves from untreated plants. The GA content of leaves fromGA-treated plants decreased after 2 weeks and none was detectableafter 5 weeks; apparently it was converted to another gibberellin,possibly the same as the natural gibberellin. GA increased chlorophyllcontent per leaf but increased leaf area more so that the chlorophyllper unit area decreased, and the leaves were paler than untreatedleaves.     

持续脱水下海藻叶绿素瞬变荧光模式的三阶段转换及临界水量的发现

在自然干燥条件下,跟踪研究了海洋红藻带形蜈蚣藻（Grateloupia turuturu Yamada),绿藻石莼（Ulva pertusa Kjellm)和褐藻海带（Laminaria japonica Aresch)的叶绿素荧光动力学曲线的变化,并用脉冲调制荧光仪分析了藻体脱水过程中的各个荧光参数。结果表明,在持续脱水过程中,3类海藻的荧光动力学曲线都显示出3个阶段的变化,即：1）在脱水开始时正常的峰形曲线;2）荧光上升至最高时持平、形成了高原型曲线;3）荧光跌落变成平台型曲线,发现荧光跌落前藻体的含水百分数是一个重要的生理指标,称为临界水量（CWC）。一旦藻体失水至低于此临界水量时,即便复水也不能使原来的峰形曲线得以恢复,说明脱水可能引起了叶绿体类囊体膜的不可逆损伤。临界水量可以用来衡量不同海藻的耐旱力,其数值高低随不同海藻而不同,并与其耐旱力成负相关。如在上述3大类海藻中,海带的CWC值最高（约90％）,但其耐旱性最差。此外,在红藻（只有红藻）经受干燥后作复水处理时,观察到有荧光急剧上升（爆发）的现象。对海膜脱水前后的几个荧光参数（F0、Fv、Fv/Fm)作了测定和比较,发现F0和Fv在脱水的第一阶段都上升,而v/Fm值维持基本不变。因此可以得出结论,活体叶绿素荧光对干旱的最初响应是立即增强,当继续失水时,F0保持上升而Fv却下降并越来越低,故此时总荧光的变化（包括荧光的跌落和爆发）主要是由F0的变化所引起的,因而进一步研究F0与脱水时类囊体膜状态变化的关系具有重要意义。     

衰老叶片和叶绿体中超氧阴离子和有机自由基浓度的变化

以电子自旋共振波谱技术,研究从水稻、玉米、花生和苋菜的成熟及衰老叶片分离的叶绿体中O_2~-的形成,以及干燥叶绿体和叶片粉末的有机自由基。经紫外光照射后老叶叶绿体的O_2~-浓度比成熟叶增大10～249％。冷冻干燥叶绿体及烘干叶片粉末在辐照前后皆有明显的单峰信号。辐照引发两种干样中形成更多的有机自由基。老叶制备的干样不论辐照或暗下都有较高水平的自由基。以上结果表明,叶片的衰老与自由基引起的损伤有关。     

Chlorophyll Formation in the Dark II. Chlorophyll in Wheat Leaves Transplanted to Pine Megagametophytes

Chlorophyll production in wheat (Triticum vulgare) leaves takes place in the dark when wheat embryos are transplanted to the megagametophytes of black pine (Pinus nigra). The chlorophyll content in the wheat leaves is about half that in black pine cotyledons of the same age.     

Substitution of Cytokinins and Chlorophyll Breakdown in Detached Wheat Leaves

Four derivatives of benzyladenine with alkyl-substitution atthe 9 position, (9-methyl, 9-methoxymethyl, 9-tetrahydro-2-pyranyland 9-cyclopentyl-N⁶ benzyladenine), can slow, depending uponthe substituent and concentration, the breakdown of chlorophyllin detached wheat leaves. (Received June 9, 1984; Accepted September 25, 1984)     

Chlorophyll Breakdown in Senescent Chloroplasts (Cleavage of Pheophorbide a in Two Enzymic Steps)

The cleavage of pheophorbide (Pheide) a into primary fluoescent chlorophyll (Chl) catabolites (pFCCs) in senescent chloroplasts was investigated. Chloroplast preparations isolated from senescent canola (Brassica napus) cotyledons exhibited light-dependent production of pFCC when assay mixtures were supplemented with ferredoxin (Fd). pFCC production in detergent-solubilized membranes was dependent on the presence of an Fd-reducing system. Pheide a cleavage required the action of two proteins, Pheide a oxygenase and a stroma protein. In the absence of stroma protein, Pheide a oxygenase converted Pheide a into a red Chl catabolite (RCC), the presumptive intermediary product of Pheide a cleavage. Incubation of the stroma protein (RCC reductase) together with chemically synthesized RCC resulted in the production of three different FCCs. Two of these catabolites were identical to the pFCCs from canola or barley (Hordeum vulgare) (pFCC-1) and sweet pepper (Capsicum annuum) (pFCC-2), respectively. Thus, the conversion of Pheide a to pFCC could be demonstrated to proceed in two consecutive steps, and both reactions depended on reduced Fd as the source of electrons. The function of Fd in Chl breakdown in vivo is corroborated by the marked retention of this protein until the late stages of senescence, as demonstrated by immunoblotting.