Effect of Aluminum Ions on the Bluing of Petal Color in Cut Chinese Bellflower, Platycodon grandiflorum

Petal color of Chinese bellflower, Platycodon grandiflorum A.DC,changed from blueviolet to blue in a short period after cutflowers were placed in a solution containing AI ions. The absorptionmaximum of Al-treated fresh petals shifted to longer wavelength(bathochromic shift) and increased in intensity. These phenomenawere also observed upon addition of Al ions to anthocyanin solution.The addition of EDTA to the anthocyanin solution treated withAl ions decreased the bluing effect due to Al addition. Thus, the flower color change of cut Chinese bellflowers byAl uptake seems to be due to the chelation of anthocyanin withAl ions. (Received December 2, 1982; Accepted March 31, 1983)     

Effects of Tissue-type and Development on Dark Respiration in Two Herbaceous Perennials

Perennial plants go through a number of developmental stagesduring the growing season. Changes in metabolism during thesephases have been documented in laboratory-grown plants but neverin native plants growing in natural habitats. The purpose ofthis study was to describe the seasonal pattern of dark respirationin the above-ground tissues of two herbaceous perennials, Bistortabistortoides(Pursh) Small and Campanula rotundifolia L., growingin the Rocky Mountains (USA). The effect of biomass accumulationon respiration rate and differences in respiration rate amongtissues were measured. Respiration rate differed significantlyamong the above-ground tissues. Reproductive structures hadthe highest respiration rates, followed by leaves, then stems.Respiration rate decreased by 10–90% over the growingseason in these tissues but was generally not correlated witha decrease in biomass accumulation. The seasonal pattern ofrespiration rate varied significantly among tissues. Total tissuerespiratory flux was calculated at 15 °C for each tissue.In both species, total above-ground respiratory flux was eitherrelatively constant during the growing season with a markeddecrease at seed dispersal or a maximum rate was reached atmid-season. In B. bistortoides, leaves had the highest totalrespiratory fluxes, and the respiratory fluxes of the stem andreproductive structures were similar to one another. In C. rotundifolia,leaf and stem respiratory fluxes were similar, while the respiratoryflux of the reproductive structures was considerably lower thanthat of leaves and stems. This study emphasizes the importanceof developmental processes and tissue-type on respiration rateand highlights the importance of including all plant tissuesin predictive models of plant carbon balance.Copyright 2001Annals of Botany Company Respiration, development, growth, maintenance, tissue, Bistorta bistortoides, Campanula rotundifolia, harebell     

Temperature Effects on Cytokinin Accumulation and Kernel Mass in a Dwarf Wheat

The objectives of this study were: (1) to quantify post-anthesiskernel cytokinin levels in ‘Tibet Dwarf’, a dwarfwheat (Triticum aestivumL.) that accumulates elevated quantitiesof leaf cytokinins; and (2) to measure the effects of temperatureon kernel cytokinin accumulation and mature kernel mass in thiswheat. Post-anthesis kernel cytokinin accumulation was measuredin control plants maintained at 25/12 °C (day/night) andtreated plants which received a 7 d exposure to 35/25 °Cbeginning at anthesis and grown to maturity at 25/15 °C.Zeatin (Z), dihydrozeatin (diHZ) and their respective ribosideswere the predominant cytokinins detected in control and treatedplants. Minimal quantities of isopentenyl adenine-type cytokininswere detected. Kernel cytokinin content peaked within 3 d afteranthesis in both groups and returned to baseline levels within1–2 d. Relative to controls, exposure to high temperaturereduced kernel cytokinin content approx. 80% within 1 d afteranthesis. Because kernel cytokinin in control Tibet Dwarf plantsexceeded that previously measured in other varieties by over100-fold, the reduced content of treated plants still exceededthat of untreated plants of other varieties. The increased cytokinincontent did not enhance thermotolerance. The temperature treatmentreduced mature kernel weights approx. 27%, similar to reductionsmeasured in other wheat varieties.Copyright 1999 Annals of BotanyCompany Triticum aestivum, endosperm development, heat stress, kernel mass, cytokinins.     

The stabilizing effect of the acyl group on the co-pigmentation of acylated anthocyanins with C-glucosylflavones

The stability of the complex formed between acylated anthocyanins and flavocommelin was compared with that between unacylated anthocyanins and the flavone. At low anthocyanin concentrations (5 × 10^?4 M), the complex involving acylated anthocyanins was much stabler than that involving ordinary anthocyanins. This extra stability is due to the acyl moiety in the acylated anthocyanins. The co-pigmentation constant (Kc) is defined as the affinity between an anthocyanin and its co-pigment.     

Temporal and Spatial Heterogeneity in the Accumulation of Anthocyanins in Cell Cultures of Catharanthus roseus (L.) G.Don.

The accumulation of anthocyanins, a group of pigmented secondarymetabolites, in cell cultures of the Madagascar periwinkle Catharanthusroseus has been investigated. In these cultures it was foundthat anthocyanin accumulation was restricted to the post-divisionphase of the culture growth cycle, during which the culturesbecame deep purple in colour. As a result of anthocyanin visibilityit has been possible to ascertain that accumulation of thesemetabolites occurred in only a small proportion of the cellpopulation. Approximately 10% of cells regularly accumulateddetectable levels. Considerable variation within this ‘productive’population was observed and using a standard integrating microdensitometerit has been possible to quantify directly this heterogeneityand compare it with data obtained from whole plants. Analysishas revealed that the variation in both intracellular anthocyanincontent and concentration in cell cultures was much greaterthan that observed within tissues of mature plants. Significantdifferences in mean values were however found between the wholeplant tissues. The relevance of this temporal and spatial heterogeneityobserved in vitro to our understanding of the control of secondarymetabolite accumulation and to the potential use of tissue culturesystems as a means to produce these compounds is discussed. Key words: Heterogeneity, anthocyanins, cell culture     

Anthocyanins and anthocyanidins in the flowers of Aconitum (Ranunculaceae)

The presence of anthocyanidins and anthocyanins were analyzed in flowers of 30 taxa of Aconitum. Delphinidin was detected as a major anthocyanidin from the hydrolysate of 29 taxa with violet and violet-blue flowers. Pelargonidin was identified as a major anthocyanidin in one taxon with white flowers (partially pale reddish purple; White group N155C by R.H.S. Colour Chart). This is the first reported detection of pelargonidin as a major anthocyanidin from Aconitum flowers. Pelargonidin was also found in ten taxa as a minor anthocyanidin, whereas cyanidin was detected from the flowers of all 30 taxa as a minor anthocyanidin.Two anthocyanins polyacylated by p-hydroxybenzoic acids, violdelphin and monodeacylcampanin were identified from 29 taxa with violet and violet-blue flowers as major anthocyanins. This is the first reported isolation of monodeacylcampanin from Aconitum flowers. The structures of these two anthocyanins were elucidated on the basis of Nuclear Magnetic Resonance (NMR) and Mass Spectrometry (MS).     

Heterologous Expression of Two Gentian Cytochrome P450 Genes can Modulate the Intensity of Flower Pigmentation in Transgenic Tobacco Plants

Two different heterologous expression systems, microsomal fractions of Saccharomyces cerevisiae and transgenic tobacco plants, were used to investigate the enzymatic activities of flavonoid 3′-hydroxylase (GtF3′H) and flavone synthase II (GtFSII) homologues isolated from gentian petals. Recombinant GtF3′H expressed in yeast showed hydroxylation activities in the 3′ position with several flavonoid substrates, while recombinant GtFSII was able to produce flavone from flavanone. GtF3′ H-expressing transgenic tobacco plants showed a slight increase in anthocyanin content and flower color intensity, and conversion of the flavonol quercetin from kaempferol. On the other hand, GtFSII-expressing plants showed a remarkable reduction in anthocyanin content and flower color intensity, and additional accumulation of flavone, especially luteolin derivatives. We demonstrated that two cytochrome P450s from gentian petals have F3′H and FSII enzymatic activities both in vitro and in vivo, and might therefore be useful in modification of flower color using genetic engineering.     

Black flower coloration in wild Lisianthius nigrescens: its chemistry and ecological consequences

The major pigments responsible for the flower color within the black flowered Gentianaceae, Lisianthius nigrescens, were characterized by HPLC and chemical analyses HPLC analysis showed one major and one minor anthocyanin and 3 major and 3 minor flavone glycosides. The anthocyanins [delphinidin-3-O-rhamnol(1-6)galactoside and its 5-O-glucoside] comprised an extraordinary 24% of the dry weight of wild collected L. nigrescens corallas, and were accompanied in a 1:1 ratio by a range of apigenin and luteolin 8-C-glucosides and their 7-O-methyl ethers. The high levels of anthocyanins and flavones (and their co-pigmentation) is thought to account for the almost complete absorption of both UV and visible wavebands observed by reflectance photography.     

Dwarfism Caused by Floral-Bud Removal in Petunia and its Reversal by Gibberellin

The effect of floral-bud removal at different stages of developmenton the plant height and on the total number of buds of Petuniawas studied. Continuous removal of all the floral buds 2 d beforeanthesis caused a marked decrease in plant height and also increasedthe total number of floral buds formed thereafter. At otherstages of floral bud development, bud removal had a lesser effecton both phenomena. Moreover, the plants did not respond to budremoval at anthesis. GA₃ at 25 ppm applied to plants from which the buds had beenremoved, promoted stem elongation. The most pronounced effectwas on plants from which the buds were removed 2 d before anthesis,but it had no effect on plants from which the buds were removedat anthesis stage. The possible involvement of endogenous growth hormones in theresponse of Petunia plants to floral-bud removal and to applicationof GA₃ is discussed. Bud removal, bud number, dwarfness, GA₃, Petunia, plant height     

The identification of flavonoids and the expression of genes of anthocyanin biosynthesis in the chrysanthemum flowers

In order to provide additional information on the coloration of chrysanthemum flowers, the flavonoid composition and the expression of six structural genes involved in anthocyanin pathway in the ray florets of a pink flowering (cv. H5) and two white flowering (cvs. Keikai and Jinba) Chrysanthemum grandiflorum cultivars were examined. HPLCDAD/ESI-MSⁿ analysis showed that cyanidin 3-O-(6″-O-malonylglucoside) and cyanidin 3-O-(3″,6″-O-dimalonylglucoside) were the two major flavonoids presented in H5, while white flowering cultivars contained flavones instead of anthocyanins. Nine flavone derivatives were detected in the three cultivars, the amount of each flavone varied upon cultivars, and seven of these were identified as luteolin 7-O-arabinosylglucuronide, apigenin 7-O-glucoside, luteolin 7-O-malonylglucoside, apigenin 7-O-malonylglucoside, chrysoeriol 7-O-malonylglucoside, acacetin 7-O-rutinoside and acacetin 7-O-malonylglucoside. The two white flowering cultivars showed similar total flavonoid content, which was about two fold higher than that in H5. A high expression of the genes encoding dihydroflavonol 4-reductase and 3-O-glucosyltransferase was detected only in H5 but not in Keikai or Jinba. Chalcone synthase, chalcone isomerase, flavanone 3-hydroxylase, and flavonoid 3′-hydroxylase were expressed in all flowers, suggesting that the lack of anthocyanin in white flowering cultivars cannot be due to any blockage of their expression.     

Anthocyanins facilitate tungsten accumulation in Brassica

Accumulation of molybdenum in Brassica was recently found to be correlated with anthocyanin content, involving the formation of a blue complex. Here the role of anthocyanins in tungsten sequestration was investigated using three species of Brassica : B. rapa (cv. Fast plants), B. juncea (Indian mustard) and B. oleracea (red cabbage). Seedlings of B. rapa and B. juncea turned blue when supplied with colourless tungstate. The blue compound co-localized with anthocyanins in the peripheral cell layers, and the degree of blueness was correlated with anthocyanin content. The direct involvement of anthocyanins in the blue coloration was evident when purified anthocyanins showed a colour change from pink to blue in vitro upon addition of tungstate, over a wide pH range. Anthocyanin production was upregulated 3-fold by W in B. juncea , possibly reflecting a function for anthocyanins in W tolerance or sequestration. The presence of anthocyanins facilitated W accumulation in B. rapa : anthocyanin-containing seedlings accumulated 3-fold more W than an anthocyaninless mutant. There was no correlation between anthocyanin content and W tolerance under these conditions. The nature of the interaction between anthocyanins and tungstate was investigated. X-ray absorption spectroscopy showed no change in the local chemical environment of W upon uptake of tungstate by the plant; HPLC analysis of purified anthocyanin with or without tungstate showed no peak shift after metal treatment.     

Ultrastructure and Function of Floral Nectaries of Chamelaucium uncinatum (Myrtaceae)

Nectar is secreted for up to 11d after anthesis inChamelauciumuncinatum . The volume and sucrose concentration secreted variesbetween flowers, plants and days. The period of nectar secretioncoincides with the period of pollen presentation and stigmaticreceptivity suggesting nectar is part of an efficient reproductivestrategy inC. uncinatum . The nectary ofC. uncinatum consistsof the entire upper surface of the ovary and hypanthium. Theepidermis of the nectary is covered by a thickened cuticle whichis only broken at the sites of the numerous modified stomatawhich are scattered across its surface. It is suggested thatnectar is secreted onto the surface of the ovary via these modifiedstomata. The presence of extensive and well developed endoplasmicreticulum, mitochondria and Golgi bodies in the nectar secretingcells indicates that a granulocrine mechanism of secretion isoccurring inC. uncinatum . Chamelaucium uncinatum ; Geraldton Waxflower; floral nectaries; nectar production; modified stomata     

The Role of Phytochrome in Anthocyanin Synthesis in Seedlings of Vigna radiata (L.) Wilczek

Previously, it has been demonstrated that the red light-inducedanthocyanin accumulation in mung bean seedlings is mediatedby phytochrome [Dumortier and Vendrig Z. Pflanzenphysiol. 87:313 (1978)]. In this paper the importance of phytochrome forthe accumulation of anthocyanins in seedlings of mung beanswas studied in non-irradiated seedlings and in seedlings irradiatedwith 5 min R. A short FR-irradiation given early after sowing reduced theamount of anthocyanins which were normally found in non-irradiatedseedlings. This indicates that P_FR may be important for at leastpart of the anthocyanin synthesis in the dark. As for the redlight-mediated anthocyanin accumulation, irradiation appearedto be most effective when given to seedlings at the age of 36–48hr. Although the seedlings were sensitive to red light irradiationbefore that time, they were not able to synthesize anthocyaninsuntil they had reached the age of 36 hr. Complete escape ofred/far-red reversibility occurred only when far-red was given12 hr after red, although partial escape could be observed witha shorter time-interval. Furthermore, the time-course of anthocyaninaccumulation after a two-fold R-irradiation was compared withthe effect of a single R-exposure. From the results could beconcluded that the pattern of anthocyanin accumulation is dependenton the time during which P_FR is present in the seedlings. Theseexperiments also indicate that P_FR not only plays a role inthe synthesis of anthocyanins but probably also in their degradation. The results of our study show that phytochrome is importantfor anthocyanin accumulation in non-irradiated mung bean seedlingsas well as in R-irradiated, and that it probably is also involvedin the degradation of the pigment. (Received January 18, 1982; Accepted April 30, 1982)     

Flower colour and cytochromes P450

Cytochromes P450 play important roles in biosynthesis of flavonoids and their coloured class of compounds, anthocyanins, both of which are major floral pigments. The number of hydroxyl groups on the B-ring of anthocyanidins (the chromophores and precursors of anthocyanins) impact the anthocyanin colour, the more the bluer. The hydroxylation pattern is determined by two cytochromes P450, flavonoid 3′-hydroxylase (F3′H) and flavonoid 3′,5′-hydroxylase (F3′5′H) and thus they play a crucial role in the determination of flower colour. F3′H and F3′5′H mostly belong to CYP75B and CYP75A, respectively, except for the F3′5′Hs in Compositae that were derived from gene duplication of CYP75B and neofunctionalization. Roses and carnations lack blue/violet flower colours owing to the deficiency of F3′5′H and therefore lack the B-ring-trihydroxylated anthocyanins based upon delphinidin. Successful redirection of the anthocyanin biosynthesis pathway to delphinidin was achieved by expressing F3′5′H coding regions resulting in carnations and roses with novel blue hues that have been commercialized. Suppression of F3′5′H and F3′H in delphinidin-producing plants reduced the number of hydroxyl groups on the anthocyanidin B-ring resulting in the production of monohydroxylated anthocyanins based on pelargonidin with a shift in flower colour to orange/red. Pelargonidin biosynthesis is enhanced by additional expression of a dihydroflavonol 4-reductase that can use the monohydroxylated dihydrokaempferol (the pelargonidin precursor). Flavone synthase II (FNSII)-catalysing flavone biosynthesis from flavanones is also a P450 (CYP93B) and contributes to flower colour, because flavones act as co-pigments to anthocyanins and can cause blueing and darkening of colour. However, transgenic plants expression of a FNSII gene yielded paler flowers owing to a reduction of anthocyanins because flavanones are precursors of anthocyanins and flavones.     

Freezing injury to ovules, pollen and seeds in winter rape

Winter rapeseed (Brassica napus, cv. Samouraï) flowersearly in spring and, under field conditions, short freezingperiods can occur. Unacclimatized plants were freeze-stressed(–3°C for 4 h) at different developmental stages ofbuds, open flowers and seeds. The dissection of pistils from stressed plants showed that freezingresults in shrivelled ovules. We assessed freezing injury onthe basis of per cent of shrivelled ovules: ovule sensitivitybegins early (8 d before anthesis) but increases up to anthesis.Crosspollination of stressed pistils with non-stressed pollenshowed that recording of freeze-injured ovules is a good methodfor early estimation of the effect of stress on seed yields. On the other hand, stress does not reduce the viability of pollen,except when it was applied at the binucleate pollen stage. Useof frozen pollen x nonstressed pistils has little effect onseed yields. Freeze injury on seeds was assessed by seed filling:seeds are very susceptible just after fertilization until 20d after fertilization (DAF). Freezing seems to inhibit seedfilling. A germination test of stressed seeds during their developmentindicated that embryo viability is not affected if the stressoccurs after 35 DAF. As the embryos develop, resistance to stressincreases. Key words: Brassica napus, rapeseed, freeze injury, pollen and ovule, seed filling     

Changes in Nuclear DNA Content of Endosperm Cells During Grain Development in Rice (Oryza sativa)

Morphological, cytological and quantitative DNA changes associatedwith endosperm development in rice caryopsis were investigated.Following a brief free-nuclear phase, the endosperm became cellularby the 4th d after anthesis. While the mean length and breadthof grain attained maximum values at about 10, d after anthesis,f. wt of the whole grain, and of the endosperm separately, continuedto increase until about 16 d after anthesis. Cell divisionsin the endosperm continued until 10 d and following stabilizationof the cell number, the nuclei attained irregular shapes. Thesize of the nuclei and nuclei and the amount of nuclear DNAvaried considerably during endosperm development. The endospermnuclei did not retain the expected 3C–6C DNA level afterthe first few rounds of division and nuclei having more than30C DNA were frequent 8 d past anthesis. The highest C valuerecorded was 74C in a 16-d-old endosperm cell. Oryza sativa, rice, caryopsis, endosperm, cell number, nuclear area, nuclear DNA content, endoreduplication     

Environmental Influences on Panicle Differentiation and Spikelet Number of Pennisetum americanum

Pearl millet (Pennisetum americanum (L.) Leeke) has a juvenilephase after which the time to panicle initiation is reducedby short daylengths. To understand more fully the mechanismunderlying temperature ? daylength interactions on panicle initiationand differentiation, plants were grown (a) at a range of constanttemperatures under a short daylength from sowing until afterpanicle differentiation and (b) at one temperature until 20d after emergence and then at a range of temperatures duringa 10 d exposure to short daylength. Temperature prior to panicle initiation determined the numberof leaves initiated on the main stem and the size of the apicaldome at the start of panicle initiation. The number of leaves,in turn, influenced the duration of the phase from panicle initiationto anthesis: this phase required a constant thermal time whenexpressed as day degrees per leaf. At anthesis, panicle lengthwas positively correlated with the number of leaves on the mainstem (and temperature) prior to panicle initiation. Changingthe temperature only during exposure to inductive daylengthsaffected the rate of growth of the apical dome so that panicledifferentiation began within 10 d at high temperature (30?C)whereas differentiation did not commence in 10 dat 21?C. Paniclesdeveloped normally if differentiation had commenced under inductivedaylengths whereas panicles were abnormal when plants were returnedto long daylengths after panicle initiation but before visibledifferentiation. Relative extension rates of the panicle during differentiationwere correlated positively with temperature. The results areconsistent with the hypothesis that panicle initiation dependson the apex attaining a critical size and that temperature,by determining the number of leaves initiated on the main stem,affects the size of the apical dome and thus the onset of panicleinitiation, the duration of paniclc differentiation and thenumber of spikelets differentiated. Key words: Pennisetum americanum, panicle differentiation, spikelet number     

Development in wheat as affected by timing and length of exposure to long photoperiod

Seeds of a spring wheat (Triticum aestivum L. cv. ‘Condor’)were vernalized and then grown at 19C in two naturally–litenvironments, one with a moderate (12 h) and the other withlong (18 h) photoperiod. Treatments consisted of transfers ofplants from the moderate to the long photoperiod chamber ondifferent occasions, or for periods of different durations.The main objectives were to determine whether wheat developmentresponds to current and previous photoperiodic environmentsand whether there is a juvenile phase when the plants are insensitiveto photoperiod. Plants under constant 18 h photoperiod had fewerleaves which appeared faster than those under constant 12 hphotoperiod (i.e. phyllochron was increased from 4.4 to 5.1d leaf^–1). Plants transferred from 12 h to 18 h photoperiodat terminal spikelet appearance (TSA) reached anthesis 4 d earlierthan plants retained at 12 h, while plants under continuouslong photoperiod (18 h) completed this phase most rapidly. Thus,there was some evidence for a historic effect of photoperiodon development. Exposure to long photoperiod during the first 5 d after plantemergence accelerated the rate of development towards anthesis,suggesting that there was no juvenile period of photoperiodicinsensitivity. There were, however, changes during ontogenyin the degree of sensitivity to long photoperiod, increasingfrom seedling emergence to a maximum c. 15 d later, and thendecreasing again. Although all treatments were imposed beforeTSA, the response was not limited to the pre-TSA phase, suggestingthat well before the terminal spikelet appeared, the plant wasalready committed to the initiation of this spikelet. Spikeletnumber decreased with delayed transfer to long photoperiod witha minimum for plants transferred to long days from 16-20 d afterseedling emergence. Additionally, there was a trend for an increasein the rate of leaf appearance (decrease in phyllochron) whenthe plants were exposed to long days between 10 and 35 d afterseedling emergence. Although the differences were small, whenconsidered in conjunction with the effects on final leaf numberthey become important in explaining differences in time to anthesis. Key words: Development, flowering, leaf number, photoperiod, phyllochron, Triticum aestivum