Pigment Production by Cultured Florets of Chrysanthemum morifolium

Individual florets (4–5 mm long) of a purple cultivar(Fandango) of the horticultural chrysanthemum (Chrysanthemummorifolium Ramat) were taken from flower buds just prior toopening and cultured in a sterile liquid medium (containinginorganic salts and sucrose) at 15 °C under a 12-h day.For the first 14 days increase in wet weight was exponential.Anthocyanin appeared on the third day and was then synthesizedrapidly. Chlorophyll and carotenoid were present initially:carotenoid levels rose quickly while chlorophyll remained almostconstant. Highest pigment content and most growth were foundwhen the florets were grown on 3 per cent sucrose. However,the highest anthocyanin concentration was found with 4 per centsucrose, the highest carotenoid concentration with 0.6 per centsucrose. No anthocyanin was produced when the florets were grownat 6 or 30 °C; maximum yield was at 15 °C. Most carotenoidwas formed at 30 °C and most chlorophyll was found at 20–5°C. All florets from 1 to 7 mm long could be cultured. Theseresults are discussed in relation to flower colour and pigmentformation in vivo.     

Supercooling Ability, Water Content and Hardiness of Rhododendron Flower Buds during Cold Acclimation and Deacclimation

The relationship between supercooling ability and water contentand killing temperature of flower buds during cold acclimationand deacclimation were studied using R. kiusianum and R. x akebono.The occurrence of multiple floret exotherms and their shiftto a narrow range at lower subzero temperatures, as well asthe marked decrease of florets water content, were observedas the symptoms of cold acclimation occuring in flower budsfrom fall to winter, and vice versa in spring buds during deacclimation.In R. kiusianum, the fully acclimated period was from Novemberto March and two months longer than that of R. x akebono. Thesupercooling ability of the former was about –25°Cand about –20°C in the latter. Although the watermigration within bud tissues during the freezing process wasdetermined in the acclimated and deacclimated buds for R. xakebono, no significant water changes could be observed, evenin the acclimated buds. Thus, it is conceivable that deep supercoolingin florets may result not necessarily from water migration fromflorets and bud axes to scales in response to freezing, butfrom low water content in situ of cold-acclimated or artificiallydehydrated flower buds. (Received July 29, 1981; Accepted October 12, 1981)     

Cold Hardiness and Acclimation Intensity in Flower Buds for Fall Bloom and Spring Bloom Clones in Rhododendron kiusianum, a Dwarf Evergreen Azalea

The relationship between the degree of cold hardiness (supercoolingability of florets) and the acclimation intensity in flowerbuds was investigated in the fall bloom and the spring bloom(typical) clones of Rhododendron kiusianum, a hardy dwarf evergreenazalea. Supercooling ability or exotherm temperature distribution(ETD) in florets was determined by differential thermal analysis(DTA) and the intensity of bud acclimation or the rate of deacclimationwas judged by the changes in ETD profiles resulting from thedehardening temperature treatment. Although the two clone typesshowed no significant differences in ETDs and water contentsin florets, they differed in their rates of bud deacclimation.The flower buds of fall bloom clones generally tend to deacclimatemore quickly than the spring bloom ones throughout the seasons.It is concluded that the degree of cold hardiness in flowerbuds of R. kiusianum does not differ between the fall bloomand spring bloom clones but the intensity of bud acclimationdoes; acclimation intensity is higher in the spring bloom clonesand the rate of deacclimation is greater in the fall bloom ones. (Received October 14, 1985; Accepted February 5, 1986)     

不同花色菊花品种花色素结构基因的表达特性

对红色、黄色、粉紫色和白色菊花品种不同开放度的花序舌状花中CHS、CHI、DFR、F3H、F3′H和3GT基因的表达量进行了相对定量分析。结果表显示:6个基因的表达因不同花色、不同发育阶段而异。‘钟山红鹰’(红色)中各基因的表达量均较高,且均在Ⅱ(松蕾期)或Ⅲ(半开期)期达到峰值,其中DFR、3GT基因的表达量远高于其他花色品种。‘金陵娇黄’(黄色)中CHS、CHI基因表达量较高,且Ⅰ(紧蕾期)、Ⅱ期表达量高于Ⅲ、Ⅳ(盛开期)期;3GT、DFR基因表达量分别高或低于‘金陵笑靥’(粉紫色)品种中相应基因的表达量,但均比红色品种低;F3H在4个品种中表达量最低,F3′H表达量接近或略低于红色或粉紫色品种,且各阶段表达水平较稳定。‘金陵笑靥’中DFR表达量仅次于‘钟山红鹰’,3GT和CHS表达量低于红色与黄色品种。‘钟山雪桂’(白色)中各基因仅有微量表达,除F3H外各基因的表达量明显低于其他花色品种。研究表明,花色素结构基因DFR、3GT是菊花花色素合成的关键基因,DFR很可能是限速关键基因,一定表达水平的CHS、CHI也是菊花花色素合成所必须的,F3H基因与花色素合成不存在直接相关。     

Changes of Anatomical Features, Photosynthesis and Ribulose Bisphosphate Carboxylase-Oxygenase Content of Mango Leaves

Changes in anatomical and physiological features, includingchanges in amount per unit area of anthocyanin and chlorophyll,in leaves of seedling mango (Mangifera indica L. cv. Irwin)trees were determined to understand what controls the rate ofphotosynthesis (Pn) at various stages of development. The youngleaves of seedling trees contained high concentrations of anthocyanin.During enlargement of leaves, the disappearance of anthocyaninand the accumulation of chlorophyll occurred concomitantly;the anthocyanin content began to decrease markedly once theleaf area had reached a maximum. During the early period ofleaf development, the thickness of mesophyll tissue decreasedtemporarily, but when the length of the leaf reached half thatof a mature leaf, the mesophyll began to thicken again. Smallstarch grains appeared in the chloroplasts of the young leavesand chloroplast nucleoids (ct-nuclei) were distributed throughoutthe chloroplasts. When leaves matured, ct-nuclei were displacedto the periphery of chloroplasts because of the accumulationof large starch grains. Compared with young leaves, green andmature leaves contained greater concentrations of ribulose bisphosphatecarboxylase-oxygenase (RuBisCO) protein. The results of immunocytochemicalexamination of RuBisCO under the light microscope reflectedthe results of electrophoresis measurements of RuBisCO. Pn waslow during the chocolate-coloured stage of early leaf development.In green and mature leaves Pn was higher; the average Pn was7·6 mg CO₂ dm^-2 h^-1 under light at intensities above500 µmol m^-2 s^-1.Copyright 1995, 1999 Academic Press Mangifera indica L., mango leaf, chloroplast nucleoids, chloroplast ultrastructure, starch accumulation, anthocyanin, chlorophyll, DAPI staining, SDS-PAGE, immunocytochemical technique     

Spectral reflectance indices and pigment functions during leaf ontogenesis in six subtropical landscape plants

Pigment combinations are regulated during leaf ontogenesis. To better understand pigment function, alterations in chlorophyll, carotenoid and anthocyanin concentrations were investigated during different leaf development stages in six subtropical landscape plants, namely Ixora chinensis Lam, Camellia japonica Linn, Eugenia oleina Wight, Mangifera indica L., Osmanthus fragrans Lowr and Saraca dives Pierre. High concentrations of anthocyanin were associated with reduced chlorophyll in juvenile leaves. As leaves developed, the photosynthetic pigments (chlorophyll and carotenoid) of all six species increased while anthocyanin concentration declined. Chlorophyll fluorescence imaging of Φ_PSII (effective quantum yield of PSII) and of NPQ (non-photochemical fluorescence quenching) and determination of electron transport rate-rapid light curve (RLC) showed that maximum ETR (leaf electron transport rate), Φ_PSII and the saturation point in RLC increased during leaf development but declined as they aged. Juvenile leaves displayed higher values of NPQ and Car/Chl ratios than leaves at other developmental stages. Leaf reflectance spectra (400–800 nm) were measured to provide an in vivo non-destructive assessment of pigments in leaves during ontogenesis. Four reflectance indices, related to pigment characters, were compared with data obtained quantitatively from biochemical analysis. The results showed that the ARI (anthocyanin reflectance index) was linearly correlated to anthocyanin concentration in juvenile leaves, while a positive correlation of Chl NDI (chlorophyll normalized difference vegetation index) to chlorophyll a concentration was species dependent. Photosynthetic reflectance index was not closely related to Car/Chl ratio, while a structural-independent pigment index was not greatly altered by leaf development or species. Accordingly, it is suggested that the high concentration of anthocyanin, higher NPQ and Car/Chl ratio in juvenile leaves are important functional responses to cope with high radiation when the photosynthetic apparatus is not fully developed. Another two leaf reflectance indices, ARI and Chl NDI, are valuable for in vivo pigment evaluation during leaf development.     

Photosynthesis, Dark Respiration and Bud Sugar Concentrations in Pepper Cultivars Differing in Susceptibility to Stress-induced Bud Abscission

Pepper (Capsicum annuum L.) cultivars differ in susceptibilityto stress-induced abscission. Previous research indicates thatthe stress susceptible cultivar 'Shamrock' undergoes a largerreduction in net assimilation rate (NAR) under low light stress,and partitions less dry matter (DM) to reproductive structuresand more to leaves than the more tolerant cultivar 'Ace'. Todetermine if photosynthetic rates under low light stress couldexplain NAR differences, photosynthesis was measured on 'Ace'and 'Shamrock'. Assimilate partitioning was compared throughmeasurement of leaf and bud respiration rates and analysis ofbud sugar concentrations. Photosynthetic rates per unit leafarea of leaves fully exposed to incident light revealed no cultivardifferences under low light conditions. Bud respiration ratesfell to a lower level in 'Shamrock' than 'Ace' in low light-stressedplants, while expanded leaves respired at higher rates in 'Shamrock'than 'Ace' under both full and low light. Bud sugar concentrationswere significantly lower in 'Shamrock' than 'Ace' after 3 dof low light stress. Susceptibility to low light stress-inducedabscission in 'Shamrock' appears to be associated with reducedassimilate partitioning to flower buds, which may be relatedto high assimilate consumption in maintenance of expanded leaves.Copyright1994, 1999 Academic Press Pepper (Capsicum annuum L.), abscission, low light stress, photosynthesis, respiration, sugars, assimilate partitioning, cultivar     

Freezing Avoidance Mechanisms by Supercooling in Some Rhododendron flower Buds with Reference to Water Relations

Excised florets of some hardy Rhododendron species did not toleratefreezing at –5°C when ice-inoculated due to intracellularfreezing. Florets in intact December buds, however, could besupercooled to about –30°C. When flower buds of R.japonicum were slowly cooled with daily decrements of 5°Cto temperatures ranging from 0 to –20°C, the exothermtemperatures of the florets drastically decreased. This wasaccompanied by a decrease in water content of florets and peduncleand an increase in that of scales. The water in florets andthe peduncle is thought to migrate to scales and other tissuesduring the early stages of freezing; the dehydrated floret hasa lower freezing point which enhances its supercooling abilityand the dehydrated peduncle helps to maintain the supercooledstate of the florets. This hypothesis would explain the dependenceon the cooling rate of supercooling in Rhododendron flower buds.Water migration within flower buds was observed in other hardyRhododendron species with some variation in ice formation siteand the quantity of migrated water. The exotherm temperatureof excised florets was inversely proportional to their watercontent. Dehydration of flower buds by wind at 0°C alsoenhanced their supercooling ability. Mechanisms of freezingavoidance by supercooling in Rhododendron flower buds and therelationship of supercooling to freezing tolerance are discussed. ¹ Contribution No. 2254 from the Institute of Low TemperatureScience ² This is a revised form of the master's thesis of the seniorauthor (M.I.) which is cited in the present and previous papers(Sakai 1979a, b, etc.). (Received August 11, 1980; Accepted June 1, 1981)     

枫香秋季变色期叶色变化及其生理基础

为探究秋季枫叶呈色的关键生理因素,该文以转色期叶色为绿色、黄色和红色的枫香单株为试材,研究了L^*、a^*、b^*值变化与叶片色素、可溶性糖及可溶性蛋白质含量变化的相关性。结果表明:(1)在变色期,3种色彩枫香叶片叶绿素a、叶绿素b、总叶绿素和类胡萝卜素均大量降解,花色素苷不同程度积累。(2)绿色叶单株叶绿素和类胡萝卜素始终保持较高含量,花色素苷含量上升4.2倍,叶片内色素含量比值始终保持稳定; 黄色叶单株叶绿素和类胡萝卜素含量最低,花色素苷含量上升4.4倍,b^*值与叶绿素含量极显著负相关,与类胡萝卜素含量显著负相关,与花色素苷/类胡萝卜素含量比值极显著正相关; 红色叶单株叶绿素和类胡萝卜素含量略高于黄色叶单株,花色素苷含量上升27.2倍,a^*值与叶绿素含量、类胡萝卜素含量极显著负相关,与花色素苷含量显著正相关,与色素含量比值无显著相关性。(3)红色叶单株具有较高的可溶性糖含量和可溶性蛋白质含量。因此,在枫香叶片变色期,保持较高的叶绿素和类胡萝卜素含量,维持色素含量比值稳定使叶片呈现绿色; 叶绿素和类胡萝卜素的大量降解,以及花色素苷/类胡萝卜素含量比值的升高使叶片呈现黄色; 叶绿素的降解和花色素苷的大量合成使叶片呈现红色。     

Temporal and spatial regulation of anthocyanin biosynthesis provide diverse flower colour intensities and patterning in <Emphasis Type="Italic">Cymbidium</Emphasis> orchid

Main conclusion

This study confirmed pigment profiles in different colour groups, isolated key anthocyanin biosynthetic genes and established a basis to examine the regulation of colour patterning in flowers of Cymbidium orchid. Cymbidium orchid (Cymbidium hybrida) has a range of flower colours, often classified into four colour groups; pink, white, yellow and green. In this study, the biochemical and molecular basis for the different colour types was investigated, and genes involved in flavonoid/anthocyanin synthesis were identified and characterised. Pigment analysis across selected cultivars confirmed cyanidin 3-O-rutinoside and peonidin 3-O-rutinoside as the major anthocyanins detected; the flavonols quercetin and kaempferol rutinoside and robinoside were also present in petal tissue. β-carotene was the major carotenoid in the yellow cultivars, whilst pheophytins were the major chlorophyll pigments in the green cultivars. Anthocyanin pigments were important across all eight cultivars because anthocyanin accumulated in the flower labellum, even if not in the other petals/sepals. Genes encoding the flavonoid biosynthetic pathway enzymes chalcone synthase, flavonol synthase, flavonoid 3′ hydroxylase (F3′H), dihydroflavonol 4-reductase (DFR) and anthocyanidin synthase (ANS) were isolated from petal tissue of a Cymbidium cultivar. Expression of these flavonoid genes was monitored across flower bud development in each cultivar, confirming that DFR and ANS were only expressed in tissues where anthocyanin accumulated. Phylogenetic analysis suggested a cytochrome P450 sequence as that of the Cymbidium F3′H, consistent with the accumulation of di-hydroxylated anthocyanins and flavonols in flower tissue. A separate polyketide synthase, identified as a bibenzyl synthase, was isolated from petal tissue but was not associated with pigment accumulation. Our analyses show the diversity in flower colour of Cymbidium orchid derives not from different individual pigments but from subtle variations in concentration and pattern of pigment accumulation.

     

Genetic variation in the reduction of attractive floral traits of an annual tarweed in response to drought and apical damage

Aims Foliar herbivory and water stress may affect floral traits attractive to pollinators. Plant genotypes may differ in their responses to the interplay between these factors, and evolution of phenotypic plasticity could be expected, particularly in heterogeneous environments. We aimed at evaluating the effects of simulated herbivory and experimental drought on floral traits attractive to pollinators in genetic families of the annual tarweed Madia sativa, which inhabits heterogeneous environments in terms of water availability, herbivore abundance and pollinator abundance.Methods In a greenhouse experiment with 15 inbred lines from a M. sativa population located in central Chile (Mediterranean-type climate), we measured the effects of apical bud damage and reduced water availability on: number of ray florets per flower head, length of ray florets, flower head diameter, number of open flower heads per plant, flowering plant height and flowering time.Important findings Apical damage and water shortage reduced phenotypic expression of floral traits attractive to pollinators via additive and non-additive effects. Plants in low water showed decreased height and had fewer and shorter ray florets, and fewer and smaller flower heads. Damaged plants showed delayed flowering, were less tall, and showed shorter ray florets and smaller flower heads. The number of ray florets was reduced by damage only in the low water treatment. Plant height, flowering time and number of flower heads showed among-family variation. These traits also showed genetic variation for plasticity to water availability. Ray floret length, flower head size and time to flowering showed genetic variation for plastic responses to apical damage. Plasticity in flowering time may allow M. sativa to adjust to the increased aridity foreseen for its habitat. Because genetic variation for plastic responses was detected, conditions are given for evolutionary responses to selective forces acting on plastic traits. We suggest that the evolution of adaptive floral plasticity in M. sativa in this ecological scenario (heterogeneous environments) would result from selective forces that include not only pollinators but also resource availability and herbivore damage.     

The Rest Period of Rhododendron Flower Buds: II. STUDIES ON THE REST PERIOD IN TISSUE 3IN SITU

Shortly after the onset of rest in Rhododendron flower buds,the buds were transferred to a tissue-culture medium. The resultsreported here show that the rest period in culture was identicalto the rest period of buds in situ. In both environments theduration of rest and the frequnency distribution of elongationof the buds were the same. Histograms of bud development againsttime were bimodal, with about 20 per cent of the buds elongatingduring the second peak. In culture, the rest period was notaffected by changes in pH, temperature, or the addition of nutrientsalts. The results further show that the duration of the rest periodof each bud was independent of the time of the onset of rest.Buds that were supplied with either indol-3yl-acetic acid orgibberellic acid in culture or in situ remained in rest. Onlya low temperature treatment had a rest-breaking influence.     

Comparative Photosynthesis in Developing Leaves of Brachystegia spiciformis Benth

Photosynthesis and dark respiration were studied during andafter the spring flush in Brachystegia spiciformis Benth. Variousparameters were examined including anthocyanin and chlorophyllcontent, Hill reaction activity, and gas exchange. Total chlorophyllcontent steadily increased reaching a constant value in fullyexpanded (25-d-old) leaves, whereas anthocyanin concentrationincreased as the chlorophylls but rapidly declined after 23d. Hill reaction measurements confirmed that leaf material fromevery stage of the flush (bud burst to mature leaves) was photosyntheticallyfunctional. The activity was low in flushing leaves with highanthocyanin content and then dramatically increased as leafanthocyanin content declined. Oxygen exchange measurements showedflushing leaves to have lower photosynthetic rates but higherrespiratory activity than mature leaves (60% and 120%, respectively).Gas exchange and in vitro electron transport were also generallycorrelated; Hill reaction activity was 128% of gas exchangein mature leaves and 92% in flushing leaves. It is concludedthat although photosynthetic rates are lower and respirationrates are higher in flushing leaves than in mature, fully expandedleaves, flushing leaves are fully photosynthetically competentand apparently require no net input of carbon for growth anddevelopment. Key words: Brachystegia, Hill reaction, photosynthesis, Zimbabwe     

Development and Control of the Number of Flowers per Node in Pisum sativum L.

Non-dormant flower initials are laid down in the axils of successiveleaf initials as they are formed by the apical meristem of Pisumsativum L. In cultivars with a maximum capability of two flowersper raceme, the undeveloped flower meristem divides into twoportions. One forms the first flower and the other either developsinto a small protrusion on one side of the first flower or becomesthe second flower, depending on the prevailing environment.Flower development in conditions favouring single-flowered racemeswas advanced by one plastochron. Variation in the number offlowers per raceme occurs between cultivars and between environments.The number of double flowers formed was favoured by higher lightintensity (120 Js^–1 m^–2) and carbon dioxide concentration(330 µ11^–) and lower temperature (15°C). Incultivars producing more than two flowers per raceme, lowerlight intensity (60 Js^–1 m^–2) plus higher temperature(20°C) increased the mean number of flowers per raceme.Soluble sugar levels in all varieties were higher (36.05 mgeq glucose g^–1 fresh weight) in the low temperature/highlight environment than the high temperature/low light environment(14.80 mg eq glucose g^–1 fresh weight). The flowering potential and stability of 13 cultivars have beenassessed in controlled environment and in sowing date trialsin the field. A stable variety, which consistently producedtwo flowers per raceme, was identified in controlled environmentand its stability was maintained in field trials. A linear regressionof stability of flower number in the field on stability in controlledenvironment accounted for 89.6 per cent of the variance (P<5per cent), but the flowering potential in a sowing date experimentwas not related to temperature or radiation intensity.     

Invertase Activity, Soluble Carbohydrates and Inflorescence Development in the Tomato (Lycopersicon esculentum Mill.)

The concentration of reducing sugars in the developing firstinflorescence of the tomato (Lycopersicon esculentum Mill.)increased steadily between the macroscopic appearance of theflower buds and the initial stages of fruit expansion. Overthis period sucrose concentrations remained relatively constant.The rise in reducing sugar concentration was accompanied byan increase in the activity of an acid invertase. In individualflower buds invertase activity rose to a maximum shortly beforeanthesis and declined sharply as the anthers dehisced. Increased planting densities and removal of source leaves reducedthe rate of dry matter accumulation by the first inflorescenceand increased the incidence of flower bud abortion. These changeswere correlated with reductions in reducing sugar concentrations,in reducing sugar/sucrose ratios and in acid invertase levels.Removal of young leaves at the shoot apex significantly increasedthe relative growth rate of the inflorescence and led to a substantialincrease in its invertase content. These treatments had relativelylittle effect on sucrose concentration in the inflorescence. The data are consistent with the operation of an invertase-mediatedunloading mechanism for transported sucrose at sinks in theflower buds. It is suggested that the retarded development ofthe first inflorescence and the high incidence of flower budabortion observed under conditions of reduced photoassimilateavailability are causally related to the decline in invertaseproduction in the flower buds. Possible mechanisms for the regulationof invertase synthesis in the flowers are discussed. Lycopersicon esculentum Mill, tomato, inflorescence development, invertase, sink activity     

The Occurrence of Rhodoxanthin in Red-leaved Seedlings of Agathis australis Salisb.

A red carotenoid pigment was isolated by paper chromatographyfrom extracts of leaves of red pigmented Agathis australis seedlings.The position and shape of the absorption spectra of this pigmentin three solvents was identical with those for rhodoxanthinisolated from the arils of Taxus baccata fruit. The behaviourof the red pigment on partitioning between petroleum ether and90 per cent, methanol, its position on sucrose, celite, andmagnesium oxide columns and its solubility in various solventswas consistent with this conclusion. The red leaf pigment andrhodoxanthin could not be separated when co-chromatographedin two solvent systems. The concentration of this pigment inred seedlings was c. 25 times greater than that in green seedlingswhile the chlorophyll content in the former was half that ofthe latter. The implications of these findings are discussed.     

The Rate of Photosynthesis in Isolated Chloroplasts

Chloroplasts were isolated using aqueous and nonaqueous procedures.Aqueous chloroplasts lost approximately 50 per cent, of theirsoluble proteins during isolation. Nonaqueous chloroplasts retainedall their soluble enzymes, but lost their ability to performthe light reactions of photosynthesis. It was possible to reconstitutea chloroplast system of higher activity by adding soluble enzymesfrom nonaqueous chloroplasts to protein-deficient aqueous chloroplasts.The properties of the reconstituted chloroplast system wereas follows: 1. The CO₂ fixation rate of the reconstituted chloroplast system( 4 µM./. chlorophyll/hr.) was 3–4 times that ofthe aqueous chloroplasts ( I µM./. chlorophyll/hr.). Thefixation of aqueous chloroplasts isapparently limited in partby lack of soluble enzymes. 2. During light-fixation, the reconstituted chloroplast systemaccumulated PGA. This indicates that the reduction of PGA totriosephosphate is a rate-limiting step in this system. 3. It was possible to increase the CO₂ fixation to 12 µM.CO₂/mg. chlorophyll/ hr. by addition of ATP and TPNH to thesystem, but the reduction of PGA was still rate-limiting. 4. Further increase in the fixation rate was obtained by concentratingthe reaction mixture. Part of the striking differences of theCO₂-fixing capabilities of chloroplasts in vivo and in vitrois caused by dilution effects. Extrapolation of the dilutioneffect to the protein concentration which exists in chloroplastsyields a CO₂ fixation rate of approximately 30 µM./mg.chlorophyll/hr. 5. Inhibitors which are located in vivo outside the chloroplastsaffect the CO₂ fixation in vitro. 6. Under consideration of the examined factors which influencethe CO₂ fixation of isolated chloroplasts, it is possible toraise the fixation from approximately 1 per cent, to at least15 per cent, of the fixation in vivo.