Emission mechanism of floral scent in Petunia axillaris

The mechanism of floral scent emission was studied in Petunia axillaris, a plant with a diurnal rhythm of scent output. The emission rate of each volatile compound oscillated in synchrony with its endogenous concentration, so that the intensity of the floral scent appeared to be determined by the endogenous concentrations. The composition of major volatiles in the flower tissue and the flower headspace showed characteristic differences. A negative correlation was found between the boiling points of the volatile compounds and the ratio of their emitted and endogenous concentrations, indicating that the composition of the floral scent depends directly on the endogenous composition of the volatile compounds. We conclude that in P. axillaris, the physiological regulation of floral scent emission operates not in the vaporization process but in the control of the endogenous concentrations of volatiles through biosynthesis and metabolic conversion.     

Phytochrome Control of Chlorophyll and Carotenoid Accumulation in Sorghum bicolor

Etiolated Sorghum bicolor seedlings manifested a significantmorphological response to short term irradiations by red andfar-red light and to a continuous far-red light. Accumulationof chlorophylls in white light and carotenoids in darkness isunder red/far-red reversible control as well as along with theeffectiveness of ‘High Irradiance Reaction’. Phytochromeis also found to eliminate the lag phase during the accumulationof chlorophylls and carotenoids in white light. (Received March 11, 1981; Accepted May 2, 1981)     

Chlorophyll Content and the Pattern of Yellowing in Senescent Leaves

In senescent leaves of four species, leaf chlorophyll contentwas approximately linearly related to the estimated area ofyellow tissue, but the species differed in the amount of chlorophylllost before yellowing became apparent. Cotoneaster and Vicia leaves and Sinapis cotyledons, which produceddistinct yellowing patterns lost about 40 per cent, whereasSolanumleaves, which yellowed more uniformly lost over 60 percent of the chlorophyll before yellowing was visible. It issuggested that the leaf-cell population of Solanum may senescerather more synchronously than the other species, and that chlorophyllloss before yellowing may be a useful index of synchrony ofsenescence in leaves.     

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.     

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.     

Effects of Benzyladenine on Chlorophyll, DNA, RNA and Protein Content of Attached Young Bean (Phaseolus vulgaris L.) Leaves

N⁶-Benzyladenine (BA) was applied to intact bean (Phaseolusvulgaris L.) primary leaves at 2 and 6 days after imbibition,when they were in the cell division and post-cell division stages,respectively. BA treatment at day 2 temporarily inhibited an increase in chlorophyllcontent in the following day, but stimulated it in later days.No such inhibition by BA was observed for changes with timein DNA, RNA, and protein content and f. wt. On the other hand,BA treatment at day 6 enhanced RNA and protein content, withoutsignificant influence on DNA and chlorophyll content and f.wt. The mode of cytokinin action on greening in leaves during cell-divisiongrowth seems to be different from that in etiolated cotyledons. Phaseolus vulgaris L., bean, greening, benzyladenine, DNA, RNA, protein     

Phytochrome Control of Cell Wall-bound Hydroxyproline Content in Etiolated Pea Epicotyls

The red light inhibition of growth of the intact pea (Pisum sativum L. cv. Alaska) third internode was correlated with an increase in the content of cell wall-bound hydroxyproline. These changes were detected 3 hours after irradiation, and possibly at 1 hour. Far red light reversed the effects of red light. The iron chelator α,α′-dipyridyl reversed the red light effects on both growth and hydroxyproline content. Using segments incubated in vitro, no phytochrome-mediated change in hydroxyproline content could be observed, perhaps because of an overwhelming wounding response. If plants were irradiated in situ and grown for 8 hours before excision and incubation of segments, some enhancement of hydroxylation by red light was detectable both colorimetrically and radioisotopically. The red light inhibition of segment growth was reversed by α,α′-dipyridyl. These results are examined in reference to the role of extensin in normal and induced growth cessation.     

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.     

Evaluation of a SPAD-502 Plus Chlorophyll Meter to Estimate Chlorophyll Content in Leaves with Interveinal Chlorosis

Russian Journal of Plant Physiology - The portable chlorophyll (Chl) meter SPAD-502 Plus (Konica Minolta Optics, Japan) is one of the most commonly used diagnostic tools for rapid and...     

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.     

Phytochrome effects on leaf growth and chlorophyll content in Petunia axilaris

Abstract Changes in the phytochrome status at the end of the daily photosynthetic period result in several plant responses. To understand the causal relations among these responses it is useful to investigate species or experimental conditions where the most common correlations among responses are broken. A step in this direction is presented here with Petunia axilaris, where FR-treated plants showed low chlorophyll content and erect leaves, but- contrary to other species-higher leaf area and plant dry weight. Differences in area expansion were related to the late phase of leaf growth and were due, at least in part, to larger cells in FR-treated plants. Effects on length/width ratio, specific leaf area, net assimilation rate, shoot/root ratio and leaf number were small or non-existent. It is suggested that the lower chlorophyll content in FR-treated plants was not a consequence of scarcity of assimilates.     

Inter-organ Control of Chlorophyll Synthesis in Primary Leaves of Dark-grown Phaseolus aureus

The changing roles of the cotyledons and hypocotyl in the development of dark-grown Phaseolus aureus seedlings are described. The effect of the cotyledons on total chlorophyll synthesis declined with age, but on a chlorophyll per gram fresh weight basis this was less pronounced. In five-day-old plants the hypocotyl was more effective than the cotyledons in increasing the chlorophyll level, and together their effect was less than additive. The promoting factors in the cotyledons were at a saturating level at this stage. The relationship between the effects of the two organs is discussed with particular reference to the components which they supply to the leaves.     

Continuous Turnover of Carotenes and Chlorophyll a in Mature Leaves of Arabidopsis Revealed by 14CO2 Pulse-Chase Labeling

Carotenoid turnover was investigated in mature leaves of Arabidopsis (Arabidopsis thaliana) by ¹⁴CO₂ pulse-chase labeling under control-light (CL; 130 μmol photons m⁻² s⁻¹) and high-light (HL; 1,000 μmol photons m⁻² s⁻¹) conditions. Following a 30-min ¹⁴CO₂ administration, photosynthetically fixed ¹⁴C was quickly incorporated in β-carotene (β-C) and chlorophyll a (Chl a) in all samples during a chase of up to 10 h. In contrast, ¹⁴C was not detected in Chl b and xanthophylls, even when steady-state amounts of the xanthophyll-cycle pigments and lutein increased markedly, presumably by de novo synthesis, in CL-grown plants under HL. Different light conditions during the chase did not affect the ¹⁴C fractions incorporated in β-C and Chl a, whereas long-term HL acclimation significantly enhanced ¹⁴C labeling of Chl a but not β-C. Consequently, the maximal ¹⁴C signal ratio between β-C and Chl a was much lower in HL-grown plants (1:10) than in CL-grown plants (1:4). In lut5 mutants, containing α-carotene (α-C) together with reduced amounts of β-C, remarkably high ¹⁴C labeling was found for α-C while the labeling efficiency of Chl a was similar to that of wild-type plants. The maximum ¹⁴C ratios between carotenes and Chl a were 1:2 for α-C:Chl a and 1:5 for β-C:Chl a in CL-grown lut5 plants, suggesting high turnover of α-C. The data demonstrate continuous synthesis and degradation of carotenes and Chl a in photosynthesizing leaves and indicate distinct acclimatory responses of their turnover to changing irradiance. In addition, the results are discussed in the context of photosystem II repair cycle and D1 protein turnover.Carotenoids are classified as accessory pigments in photosynthesis because they augment light harvesting in the blue spectral region by transferring the absorbed light energy to chlorophyll (Chl). However, the universal occurrence of carotenoids in photosynthetic cells, from bacteria to higher plants, indicates their essential roles, rather than mere accessory roles, in photosynthesis. Under excess light, carotenoids provide protection against photooxidative damage by facilitating dissipation of excitation energy from singlet- or triplet-state Chl and scavenging highly reactive singlet oxygen, which is generated through interaction between triplet excited Chl and oxygen (Demmig-Adams, 1990; Müller et al., 2001). These photoprotective functions make carotenoids indispensable for oxygenic photosynthesis, as demonstrated by lethal effects of inhibitors of carotenoid biosynthesis in plants (Bramley, 1993). Regulation of light harvesting and photoprotection by carotenoids requires their close proximity as well as the proper orientation to Chl molecules in pigment-protein complexes of PSI and PSII. Furthermore, a small fraction of non-protein-bound carotenoids serves as antioxidants in the lipid phase of photosynthetic membranes (Havaux and Niyogi, 1999; Havaux et al., 2004) and influences the structure and fluidity of the lipid bilayer (Gruszecki and Strzałka, 2005). Despite these and other lines of defense, the PSII reaction center polypeptide D1, and to a lesser extent also D2, undergo frequent photooxidative damage and repair in the light (Melis, 1999; Baena-González and Aro, 2002). When the repair process cannot keep up with the rate of photodamage, the overall quantum yield of PSII declines.Carotenoids are derived from isoprenoid precursors in plastids (for reviews on carotenoid biosynthesis in plants, see Lichtenthaler, 1999; Hirschberg, 2001; DellaPenna and Pogson, 2006; Giuliano et al., 2008; Tanaka et al., 2008; Cazzonelli and Pogson, 2010). Following the formation of linear C₄₀ lycopene, the pathway splits into two branches of major cyclic carotenoids: the β,β-branch gives rise to β-carotene (β-C) having two β-rings, whereas the β,ϵ-branch leads to formation of α-carotene (α-C) having one β-ring and one ϵ-ring. Hydroxylation of β-C and α-C produces the xanthophylls zeaxanthin (Z) and lutein (L), respectively. In the β,β-branch, epoxidation of the β-rings of Z results in successive synthesis of antheraxanthin (A) and violaxanthin (V); subsequently, V can be converted to neoxanthin (N), the last carotenoid product of the β,β-branch. Except for some species (García-Plazaola et al., 2007), L does not undergo β-ring epoxidation and the β,ϵ-branch thus stops with L, the most abundant carotenoid in leaves.Each of these carotenoids occupies specific binding sites in the photosynthetic apparatus to fulfill distinct roles. In both PSI and PSII, carotenes (α-C and β-C) are generally bound in core complexes, which also harbor Chl a molecules, while the majority of xanthophylls (L, Z, A, V, and N) are bound in light-harvesting antenna complexes together with Chl a and Chl b molecules (Bassi et al., 1993; Lee and Thornber, 1995). Accumulation of β-C in core complexes is a common feature of diverse photosynthetic organisms, whereas the occurrence of α-C in addition to β-C is restricted to certain taxa. For higher plants, α-C has been found in leaves of some, but not all, shade-tolerant species (Thayer and Björkman, 1990; Demmig-Adams and Adams, 1992; Demmig-Adams, 1998; Matsubara et al., 2009). Based on this photoacclimatory behavior, it has been proposed that α-C may function as a light-harvesting pigment while β-C may contribute to photoprotection (Krause et al., 2001), presumably by scavenging singlet oxygen and mediating a cyclic electron transfer around PSII (Tracewell et al., 2001; Telfer, 2005).Pronounced light-dependent changes are also observed for xanthophyll composition in light-harvesting antenna complexes. In a short term (minutes to hours), operation of the xanthophyll cycle, involving Z, A, and V, modulates levels of Z in a light-dependent manner. It is widely accepted that Z is able to enhance the dissipation of excess light energy from singlet excited Chl while V is not (Demmig-Adams, 1990; Müller et al., 2001). Long-term acclimation (days) to strong irradiance typically results in an increased pool size of the xanthophyll-cycle pigments (V + A + Z) and downsizing of PSII antenna, as indicated by a greater Chl a-to-Chl b ratio (Demmig-Adams and Adams, 1992; Demmig-Adams, 1998; Matsubara et al., 2009). Based on the observed changes in steady-state amounts of xanthophylls and carotenes following irradiance shifts, alterations in the balance between biosynthesis and degradation, or turnover, have been implicated as a mechanism for long-term adjustment of carotenoid levels in leaves (Förster et al., 2009). However, just how much biosynthesis and degradation of different carotenoids occurs in photosynthesizing green leaves is an open question to date.In order to gain insight into carotenoid turnover of mature leaves, we conducted ¹⁴CO₂ pulse-chase labeling experiments with Arabidopsis (Arabidopsis thaliana) plants. Carotenoid turnover has been studied in algae in the past by applying [¹⁴C]bicarbonate (Blass et al., 1959; Grumbach et al., 1978); for example, no more than 1% to 2% of the photosynthetically incorporated ¹⁴C was allocated to the lipophilic fraction containing Chl and carotenoid in Chlorella pyrenoidosa after a 2-h pulse application (Grumbach et al., 1978). Even lower labeling efficiency is expected for photosynthetic pigments in nongrowing green leaves, in which pigment turnover takes place almost exclusively as part of the maintenance and acclimation of photosynthetic membranes. To overcome this intrinsic but anticipated difficulty, a ¹⁴CO₂ application setup was established for efficient and reproducible ¹⁴CO₂ incorporation in detached leaves of Arabidopsis during a short (30-min) pulse period. Moreover, a method of pigment separation was developed for ¹⁴C detection in concentrated leaf pigment extracts using a radio-HPLC system. Because carotenoid composition exhibits marked sun-shade responses in leaves (Demmig-Adams and Adams, 1992; Demmig-Adams, 1998; Matsubara et al., 2009), ¹⁴CO₂ labeling patterns were studied in three different sets of Arabidopsis plants: (1) plants grown under 130 μmol photons m⁻² s⁻¹ (control light [CL]) and exposed to CL during a chase period of up to 10 h (CL plants); (2) plants acclimated to 1,000 μmol photons m⁻² s⁻¹ (high light [HL]) for 2 weeks and exposed to HL during the chase period (HL plants); and (3) plants grown under CL but exposed to HL during the chase period (CL→HL plants). These treatments simulated short-term (CL→HL) and long-term (CL or HL) responses to irradiance. Finally, as ¹⁴C was found to be rapidly incorporated in β-C and Chl a molecules in leaves of wild-type plants, in which β-C represents the only carotene species, ¹⁴C labeling experiments were also conducted with leaves of lut5 mutants containing both α-C and β-C (Fiore et al., 2006; Kim and DellaPenna, 2006) to compare turnover of the two carotenes.     

Floral scent diversity is differently expressed in emitted and endogenous components in Petunia axillaris lines

BACKGROUND AND AIMS: Among the subspecies of Petunia axillaris are various lines emitting sensorially different scents. Analysis of variations in floral scent among genetically close individuals is a powerful approach to understanding the mechanisms for generating scent diversity. METHODS: Emitted and endogenous components were analysed independently to gain information about evaporation and endogenous production in 13 wild lines of P. axillaris. A dynamic headspace method was used to collect emitted components. Endogenous components were extracted with solvent. Both of these sample types were subjected to quantitative and qualitative analysis by gas chromatography (GC)-flame ionization detector (FID) and GC-mass spectrometry (MS). KEY RESULTS AND CONCLUSIONS: Whereas the profiles of emitted compounds showed qualitative homogeneity, being mainly composed of methyl benzoate with quantitative variation, the profiles of endogenous compounds showed both qualitative and quantitative variation. A negative correlation was found between the evaporation ratio and boiling point of each compound examined. Lower boiling point compounds were strongly represented in the emitted component, resulting in the reduction of qualitative variation in floral scent. In conclusion, floral scent diversity results from variation in both the endogenous production and the evaporation rate of the individual volatile compounds.     

Distribution of self-compatible and self-incompatible populations of Petunia axillaris (Solanaceae) outside Uruguay

Petunia axillaris occurs in temperate South America and consists of three allopatric subspecies: axillaris, parodii, and subandina. Previous studies have revealed that subsp. axillaris is self-incompatible (SI), subsp. parodii is self-compatible (SC) in Uruguay, and subsp. subandina is SC in Argentina. The SI/SC status over the entire distribution range is not completely understood, however. The objective of this study was to examine the overall SI/SC status of the respective subspecies in comparison with floral morphology. The results confirmed that subsp. parodii and subsp. subandina were SC throughout the distribution range, and that subsp. axillaris was also SC in Brazil and in most of the Argentinean territory. The SI P. axillaris occurs in the natural population only between 34 and 36°S, along the eastern shore of South America. The Brazilian and Uruguayan subsp. axillaris differed in SI/SC status and floral morphology. We discuss the cause of this difference.     

Phytochrome Control of Longitudinal Growth and Phytochrome Synthesis in Maize Seedlings

The active, far-red light absorbing, form of phytochrome was found to inhibit growth and phytochrome levels in the mesocotyl and coleoptile of 4- to 5.5-day-old seedlings of Zea mays L. Short, low-irradiance red or far-red light treatments were used to produce different proportions of active phytochrome at the end of highdirradiance white-light periods, which left different levels of total phytochrome in the plants. After light treatments which left relatively high levels of spectrophotometrically assayable phytochrome in the seedlings, apparent phytochrome synthesis in the subsequent dark period was low regardless of the proportions of each form of the pigment present at the beginning of the dark period. In light treatments producing relatively low levels of assayable phytochrome, levels of apparent phytochrome synthesis in both red and far-red treatments and differences between apparent synthesis in red and far-red treatments were maximal. No simple correlation was found between growth and apparent phytochrome synthesis. However, growth and total phytochrome levels were positively correlated in both organs. Using a subtractive method of correlation, in which only phytochrome effects were plotted, strong linear relationships between phytochrome levels or longitudinal growth and P_fr levels were found in those light treatments leaving greater than 8% of dark control levels of phytochrome in the tissues. Using this technique non-linear, inverse relationships between P_fr and apparent phytochrome synthesis was found, indicating that modes of phytochrome control over phytochrome synthesis and growth differ. Our results are consistent with the view that in vivo assays of “bulk’ phytochrome reflect levels and states of the physiologically active phytochrome fraction under our experimental conditions in maize.