Blueing of sepal colour of Hydrangea macrophylla

Blue and red sepals of Hydrangea macrophylla were quantitatively analyzed for aluminium, anthocyanin (delphinidin 3-glucoside) and copigments (caffeoyl- and p-coumaroylquinic acids). All the blue sepals examined contained both Al and copigments (especially 3-caffeoylquinic acid) in considerable amounts. In in vitro experiments using 3- and 5-caffeoylquinic acids, Al and delphinidin 3-glucoside, it was shown that 3-caffeoylquinic acid and Al formed a blue complex with the anthocyanin. Absorption spectra of the blue complex were practically identical with those of the blue solutions obtained from blue hydrangea sepals by extraction with 4 M NACl. In contrast, 5-caffeoylquinic acid (chlorogenic acid) which was also present in hydrangea sepals gave only a red-purple colour with Al and the anthocyanin. Neither 3-caffeoylquinic acid nor Al independently produced blue colour when mixed with the anthocyanin in the mole ratios of 1–30, this being the range that the compounds were found in blue sepals. These results suggest that blue colour of hydrangea sepals is due mainly to the blue complex of delphinidin 3-glucoside-aluminium-3-caffeoylquinic acid. The role of aluminium may be to stabilize an interaction between the quinic ester and the anthocyanin.     

Eudesmanolides and costic acid derivatives from Flourensia macrophylla

The aerial parts of Flourensia macrophylla afforded, in addition to compounds similar to those from other Flourensia species, four new eudesman     

Light absorption patterns of intact Rosa flowers in relation to the flower colour

Absorption curves of fresh, intact petals from 18 rose cultivars and 2 species were measured and compared with visual evaluations of their colours and there was a reasonable correlation. The in vivo maxima of anthocyanin absorption were in the range of 520–560 nm. Five patterns of absorption spectrum in the visible region were recognized: (a) maximum range ca. 520–535 rim (red roses); (b) as (a) but low absorbance (pink roses); (c) absorption pattern varying with age of flowers; (d) absorption at long wavelengths in blue roses due to co-pigmentation of cyanin, flavonols; (e) absorption of carotenoids and anthocyanins together in yellow, orange or orange red flowers.     

Malonic acid: The acyl moiety of the Mimulus luteus anthocyanin

Malonic acid has been identified as the acylating agent of the anthocyanin produced by the Mimulus luteus complex.     

Investigation of the in vivo organization of anthocyanins using resonance raman microspectrometry

Resonance Raman (RR) microspectrometry constitutes a new means for studying the organization of anthocyanins in living tissues. RR spectra of the pigments present in a single cell have been recorded from the skins of the mature berries of the ‘Pinot noir’ grape, as well as the petals of the common mallow. Comparison of these spectra with those obtained from model solutions of anthocyanins permits us to conclude that in the ‘Pinot noir’ berries, malvidin 3-glucoside is the main pigment. Furthermore, inside the skin it is essentially in the quinonoidal base form, whereas in the outer face of the skin it is mainly in the flavylium form. In the upper epidermis of petals of the common mallow, only malvidin 3,5-diglucoside could be detected, entirely in the cationic flavylium form. Since self-association or co-pigmentation processes do not seem to contribute much to the RR spectra, we conclude that they perturb the electronic excited state of the monomeric anthocyanin chromophores much more than they modify the corresponding electronic ground state. In the case of the skins of the mature berries of the ‘Pinot noir’ grape, dark grains, which we believe to be anthocyanoplasts, have been observed. In vivo RR spectra of the dark grains have been recorded.     

Anthocyanins in Salix species: A new anthocyanin in salix purpurea bark

Cyanidin 3-glucoside and delphinidin 3-glucoside (minor component) occurred in the bark of Salix purpurea (29 cultivars examined), S. fragilis (3 cvs), S. americana (4 cvs), S. rubra (1 cv.), S. incana (1 cv.), S. aegyptica (1 cv.) and S. alba (3 cvs) and several hybrids. A previously unrecorded anthocyanin was also present in appreciable amounts in the bark of eleven S. purpurea cultivars, notably those with small leaves. In other large-leaved cultivars of S. purpurea (18) it occurred only in traces or was not detected with certainty. A trace was found in one purpurea hybrid, but it was not detected in four others. Small amounts of the new anthocyanin were also found in S. incana (1 cv.), S. fragilis cv. Basfordiana, S. americana cv. Cordata and one hybrid, but were absent from other cultivars of S. fragilis (2) and S. americana (2), and also from S. alba (3), S. aegyptica (1), S. daphnoides (1), S. rubra (1), S. triandra (1), S. viminalis (1) and three hybrids. The new anthocyanin is unique in containing fructose as well as glucose and is based upon a previously undescribed anthocyanidin, possibly dimeric in nature, which is provisionally named purpurinidin.     

Greenish blue flower colour of Strongylodon macrobotrys

The flower colour of Strongyledon macrobotrys is luminous blue green and attracts bats for pollination. The chemical basis for development of the flower colour was investigated. The flower contained an anthocyanin (malvin) and a flavone (saponarin), approximately 1:9 (malvin: saponarin) in molar ratio. The pH of the pigmented epidermal cell sap of the jade vine petal was exceptionally high, 7.90, while the pH value of the colourless inner tissue was 5.60. Copigmentation test using the mixtures of malvin and saponarin (1:9 M ratio) at various pH values revealed that the characteristic blue green colour of the jade vine is developed by copigmentation of malvin with saponarin in slightly alkaline cell sap, pH 7.9. In the copigmentation in slightly alkaline condition, saponarin shows a strong yellow colour, which gives a greenish tone to the flower colour.     

Origin of the exceptional colour stability of the Zebrina anthocyanin

The exceptional colour stability near neutrality of the Zebrina anthocyanin is related both to a high value of the acidity constant and to the total absence of formation of the colourless pseudobase and chalcone. The aromatic residues of the acylated groups (caffeic and ferulic) probably interact with the positively charged pyrylium nucleus. This intramolecular effect prevents further addition of nucleophiles to the pyrylium ring; in particular, addition of water is largely disfavoured compared to ordinary anthocyanins.     

Lunularic acid and related compounds in liverworts,algae and Hydrangea

Lunularic acid and lunularin were detected in 76 species of hepatics, but not in any of the Anthrocerotales or Algae examined. Lunularic acid, lunularin, 3,4′-dihydroxystilbene and a glycoside of lunularic acid were also identified in extracts of Hydrangea macrophylla roots, together with hydrangenol, hydrangeic acid and their glucosides.     

Differences in the incorporation pattern of labelled cinnamic acid and l-phenylalanine into the anthocyanins of Petunia hybrida

The incorporation of phenylalanine-[¹⁴C] into anthocyanins of petals of Petunia hybrida is greater than that of cinnamic acid-[¹⁴C]. Moreover, there is a preferential incorporation of phenylalanine-[¹⁴C] into delphinidin 3-monoglucoside, as compared with the incorporation into cyanidin and peonidin 3-monoglucosides.     

The triterpenoid acids of Schinus molle

From the acidic fraction of the oleoresin obtained from the berries of Schinus molle was isolated isomasticadienonic, isomasticadienonalic, masticadienonic and 3-epi-isomasticadienolic acids. In addition the new 3-epi-isomasticadienolalic acid was isolated. Both isomasticadienonalic and 3-epi-isomasticadienolalic acids had an aldehydic group attached to C-20. The absolute configuration of this centre was established. The PMR study of the isolated compounds, of their reduction products and O-acetyl derivatives is reported.     

De novo synthesis and hormonal regulation of a dipeptidase in Cucurbita maxima

The following evidence was obtained for the de novo synthesis of dipeptidase in squash (Cucurbita maxima Duch. var. Hubbard) cotyledons during germination: (i) the amount of [¹⁴C]leucine incorporated into the dipeptidase was greater than that found in other proteins; (ii) the enzyme coincided with a peak of radioactivity in DEAE column chromatography; and (iii) the specific radioactivity of the enzyme increased with purification. There was also a positive correlation between the rate of [¹⁴C]leucine incorporation into dipeptidase and the rate of dipeptidase development. Four plant growth regulators, gibberellic acid (GA) benzyladenine (BA), indol-3-acetic acid (IAA), and abscisic acid (ABA) were examined for their effect on the development of dipeptidase activity at 5 × 10^?6 and 5 × 10^?5 M. None of these regulators affected the activity of the isolated dipeptidase per se. In intact see ds, BA and IAA inhibited the development of dipeptidase activity at the higher concentration, ABA reduced the activity at both concentrations; however, GA enhanced its development at the higher concentration. In distal-half cotyledons, BA and GA stimulated enzyme development but they showed no synergistic effect. IAA suppressed the development of enzyme activity at the higher concentration and ABA inhibited development at both levels.     

In vitro auxin production by Balansia epichloë

Balansia epichloë, a systemic plant pathogen isolated from Sporobolus poiretii, was shown to produce the plant growth regulators 3-indole acetic acid, 3-indole ethanol, 3-indole acetamide and methyl-3-indole carboxylate when grown on a medium containing tryptophan. When grown on a tryptophan deficient medium 3-substituted indole derivatives were not detected. However, extracts of the medium in lower doses increased and in higher doses inhibited the growth of wheat coleoptiles.     

Biosynthesis of ticloidine in Physalis peruviana

The aerial parts and roots of Physalis peruviana (Cape Gooseberry) have been shown to contain tigloidine (3β-tigloyloxytropane) and 3α-tigloyloxytropane. The tiglic acid moiety of these alkaloids is derived from l-iSoleucine.     

Membrane permeability changes: A component of phytochrome-mediated anthocyanin synthesis in Sinapis alba

Dark synthesis of anthocyanin in Sinapis alba seedlings is greatly promoted by short treatments with n-propanol. The effect of n-propanol treatment is reversed by subsequent far-red light pulses. Photoreversibility kinetics suggest that n-propanol and red light act in the same way. However, phytochrome measurements and other control experiments suggest that n-propanol treatment does not lead to significant Pfr production, nor does it increase the effectiveness of any ‘dark’ Pfr present in the seedlings. The findings are difficult to explain in terms of Pfr as the sole effector of this phytochrome-mediated response.     

Genetic control of chalcone synthase activity in flowers of Antirrhinum majus

Chalcone synthase activity was demonstrated in flower extracts of defined genotypes of Antirrhinum majus. Independent of the genetic state of the g     

Biosynthesis of (2E,4E,6E)-5-acetoxymethyltetradeca-2,4,6-trienoic acid in Eremophila oppositifolia

Evidence is presented indicating that the triple conjugated branched chain fatty acid from Eremophila oppositifolia R.Br. arises by the acetate-malonate pathway with the side chain carbon atom originating from the S-methyl group of methionine.     

Structural colour and iridescence in plants: the poorly studied relations of pigment colour

Background

Colour is a consequence of the optical properties of an object and the visual system of the animal perceiving it. Colour is produced through chemical and structural means, but structural colour has been relatively poorly studied in plants.

Scope

This Botanical Briefing describes the mechanisms by which structures can produce colour. In plants, as in animals, the most common mechanisms are multilayers and diffraction gratings. The functions of structural colour are then discussed. In animals, these colours act primarily as signals between members of the same species, although they can also play roles in camouflaging animals from their predators. In plants, multilayers are found predominantly in shade-plant leaves, suggesting a role either in photoprotection or in optimizing capture of photosynthetically active light. Diffraction gratings may be a surprisingly common feature of petals, and recent work has shown that they can be used by bees as cues to identify rewarding flowers.

Conclusions

Structural colour may be surprisingly frequent in the plant kingdom, playing important roles alongside pigment colour. Much remains to be discovered about its distribution, development and function.     

Analysis of 3-indole carboxylic acid in Pinus sylvestris needles

3-Indole carboxylic acid (ICA) has been characterized as an endogenous constituent of Pinus sylvestris needles. Quantitative estimates of 3-indole acetic acid (IAA) and ICA, corrected for both sample losses and the conversion of IAA to ICA occurring during purification, indicate that Pinus needles contain 24.5 ± 6.5 ng IAA/g and 2.3 ± 0.4 ng ICA/g.