Short communication. Do anthocyanins play a role in UV protection of the red juvenile leaves of Syzygium?

The biological function of juvenile leaves pigmented with anthocyanin is poorly understood. The role anthocyanins play in UV protection was assessed in juvenile leaves of two Syzygium species (S. luehmannii and S. wilsonii) which contain high anthocyanin concentrations. HPLC was used to separate UV-absorbing anthocyanins from other soluble UV-absorbing phenolic compounds. The isolated anthocyanins (predominantly malvidin-3,5-diglucoside) contributed little to the total absorbance of UV-A and UV-8 radiation. This was because the non-acylated anthocyanins only effectively absorbed shortwave UV-B radiation and the strong absorbance by other compounds. These results suggest that the UV protection hypothesis is not valid for anthocyanins in juvenile Syzygium leaves.     

Are green islands red herrings? Significance of green islands in plant interactions with pathogens and pests

The term green island was first used to describe an area of living, green tissue surrounding a site of infection by an obligately biotrophic fungal pathogen, differentiated from neighbouring yellowing, senescent tissue. However, it has now been used to describe symptoms formed in response to necrotrophic fungal pathogens, virus infection and infestation by certain insects. In leaves infected by obligate biotrophs such as rust and powdery mildew pathogens, green islands are areas where senescence is retarded, photosynthetic activity is maintained and polyamines accumulate. We propose such areas, in which both host and pathogen cells are alive, be termed green bionissia. By contrast, we propose that green areas associated with leaf damage caused by toxins produced by necrotrophic fungal pathogens be termed green necronissia. A range of biotrophic/hemibiotrophic fungi and leaf-mining insects produce cytokinins and it has been suggested that this cytokinin secretion may be responsible for the green island formation. Indeed, localised cytokinin accumulation may be a common mechanism responsible for green island formation in interactions of plants with biotrophic fungi, viruses and insects. Models have been developed to study if green island formation is pathogen-mediated or host-mediated. They suggest that green bionissia on leaves infected by biotrophic fungal pathogens represent zones of host tissue, altered physiologically to allow the pathogen maximum access to nutrients early in the interaction, thus supporting early sporulation and increasing pathogen fitness. They lead to the suggestion that green islands are 'red herrings', representing no more than the consequence of the infection process and discrete changes in leaf senescence.     

H2O2 intensifies CN−-induced apoptosis in pea leaves

H2O2 intensifies CN(-)-induced apoptosis in stoma guard cells and to lesser degree in basic epidermal cells in peels of the lower epidermis isolated from pea leaves. The maximum effect of H2O2 on guard cells was observed at 10(-4) M. By switching on non-cyclic electron transfer in chloroplasts menadione and methyl viologen intensified H2O2 generation in the light, but prevented the CN--induced apoptosis in guard cells. The light stimulation of CN- effect on guard cell apoptosis cannot be caused by disturbance of the ribulose-1,5-bisphosphate carboxylase function and associated OH* generation in chloroplasts with participation of free transition metals in the Fenton or Haber-Weiss type reactions as well as with participation of the FeS clusters of the electron acceptor side of Photosystem I. Menadione and methyl viologen did not suppress the CN(-)-induced apoptosis in epidermal cells that, unlike guard cells, contain mitochondria only, but not chloroplasts. Quinacrine and diphenylene iodonium, inhibitors of NAD(P)H oxidase of cell plasma membrane, had no effect on the respiration and photosynthetic O2 evolution by leaf slices, but prevented the CN(-)-induced guard cell death. The data suggest that NAD(P)H oxidase of guard cell plasma membrane is a source of reactive oxygen species (ROS) needed for execution of CN(-)-induced programmed cell death. Chloroplasts and mitochondria were inefficient as ROS sources in the programmed death of guard cells. When ROS generation is insufficient, exogenous H2O2 exhibits a stimulating effect on programmed cell death. H2O2 decreased the inhibitory effects of DCMU and DNP-INT on the CN(-)-induced apoptosis of guard cells. Quinacrine, DCMU, and DNP-INT had no effect on CN(-)-induced death of epidermal cells.     

Do cytochromes function as oxygen sensors in the regulation of nitrate reductase biosynthesis?

The observation that oxygen represses nitrate reductase biosynthesis in a hemA mutant grown aerobically with or without delta-aminolevulinic acid indicates that cytochromes are not responsible for nitrate reductase repression in aerobically grown cells.     

Quantitative Imaging of Microtubule Alteration as an Early Marker of?Axonal Degeneration after Ischemia in Neurons

Neuronal death can be preceded by progressive dysfunction of axons. Several pathological conditions such as ischemia can disrupt the neuronal cytoskeleton. Microtubules are basic structural components of the neuronal cytoskeleton that regulate axonal transport and neuronal function. Up-to-date, high-resolution observation of microtubules in living neuronal cells is usually accomplished using fluorescent-based microscopy techniques. However, this needs exogenous fluorescence markers to produce the required contrast. This is an invasive procedure that may interfere with the microtubule dynamics. In this work, we show, for the first time to our knowledge, that by using the endogenous (label-free) contrast provided by second harmonic generation (SHG) microscopy, it is possible to identify early molecular changes occurring in the microtubules of living neurons under ischemic conditions. This is done by measuring the intensity modulation of the SHG signal as a function of the angular rotation of the incident linearly polarized excitation light (technique referred to as PSHG). Our experiments were performed in microtubules from healthy control cultured cortical neurons and were compared to those upon application of several periods of oxygen and glucose deprivation (up to 120 min) causing ischemia. After 120-min oxygen and glucose deprivation, a change in the SHG response to the polarization was measured. Then, by using a three-dimensional PSHG biophysical model, we correlated this finding with the structural changes occurring in the microtubules under oxygen and glucose deprivation. To our knowledge, this is the first study performed in living neuronal cells that is based on direct imaging of axons and that provides the means of identifying the early symptoms of ischemia. Live observation of this process might bring new insights into understanding the dynamics and the mechanisms underlying neuronal degeneration or mechanisms of protection or regeneration.     

Cadmium-induced early changes in O2 •−, H2O2 and antioxidative enzymes in soybean (Glycine max L.) leaves

Cadmium-induced initial changes in the production of reactive oxygen species (ROS) and antioxidant mechanism were investigated in soybean (Glycine max L. cv. Don Mario 4800 RR) leaves. Whole plants (WP) and plants without roots (PWR) were exposed to 0.0, 10.0 and 40.0 μM Cd for 0, 4, 6 and 24 h. Compared to PWR, a higher level of endogenous Cd in WP was associated with a lower oxidative stress measured in terms of lipid peroxidation. Furthermore, O₂ ^•− content decreased in the leaves of Cd-treated WP, whereas it increased in those of Cd-treated PWR. Although O₂ ^•− accumulation in PWR was associated with a decrease in superoxide dismutase (SOD) activity, O₂ ^•− diminution in WP leaves was not related to any increase in SOD activity. H₂O₂ content increased in the leaves of both Cd-treated WP and PWR, and it was concomitant with a corresponding decline in catalase (CAT) and ascorbate peroxidase (APX) activities. When diphenyl iodonium (DPI), an inhibitor of NADPH oxidase, was added, H₂O₂ content remained unchanged in Cd-treated WP, suggesting that NADPH oxidase does not participate in the early hours of Cd toxicity. Taken together, our results showed that early ROS evolution and oxidative damage were different in WP and PWR. This suggests that the response in soybean leaves during the early hours of Cd toxicity is probably modulated by the root.     

Weak coherent radiation of OH and ortho- H2O space masers as a carrier in biocommunication: the ortho/para-conversion of H2O spin isomers?

A conception of biocommunication based on the principle of radiophysics stating that the carrier modulation takes place at the resonance frequency in the transmission-receiver system has been substantiated and proved. The coherent radiation of space OH-masers (1.6-1.7 GHz) and ortho-H2O-maser (22.3 GHz) is proposed as a source of the carrier frequency. The narrow lines of rotational transition of H2O and OH molecules in liquid water were proposed to be considered as an analog of selective resonances of transmitter and receiver in radiocommunication. The possibility of the ortho-para conversion of H2O spin isomers, induced by weak electromagnetic fields, is discussed.     

Synthesis and evaluation of novel N–H and N-substituted indole-2- and 3-carboxamide derivatives as antioxidants agents

We have previously reported on the synthesis of novel indole derivatives where some compounds showed significant antioxidant activity. Here, we report the synthesis of novel N–H and N-substituted indole-2- and 3-carboxamide derivatives and investigated their antioxidant role in order to identify structural characteristics responsible for activity. Although all compounds showed a strong inhibitory (95–100%) effect on superoxide anion (SOD) only compounds 4, 5 and 6 showed simliar potency for the inhibition of lipid peroxidation (81–94%) which revealed that compounds 4, 5 and 6 possessed highly potent antioxidant properties. Substitution in the 1-position of the indole ring caused the significant differences between the activity results regarding lipid peroxidation inhibition.     

Do the Copper Complexes of Histamine,Histidine and of Two H2-Antagonists React with O−2?

The effects of cimetidine, ranitidine, histamine and histidine. as well as of their copper complexes, have been examined in an enzymic and chemical O^?₂ generated systems. Copper complexes like CuZnSOD inhibited both the reduction of cytochrome c and NBT²⁺ in xanthine-xanthine oxidase systems, but their inhibitory action was due to a certain extent to the copper-induced inhibition of xanthine oxidase. EDTA abolished the inhibitory effect of all copper complexes studied. Luminol chemiluminescence in NADH,-PMS system was inhibited by CuZnSOD while it was enhanced by copper complexes. The copper-accelerating effect gradually increased up to about I μM Cu and decreased, reaching the control values up to 10 μM Cu. In the presence of low copper concentrations chemiluminescence was inhibited by CuZnSOD only, while in the presence of high copper concentrations it was inhibited by catalase and mannitol. but not by CuZnSOD. The ligands however, have been ineffective in the two O^?_2; generated systems.     

Do spin traps also act as classical chain-breaking antioxidants? A quantitative kinetic study of phenyl tert-butylnitrone (PBN) in solution and in liposomes

Free radical spin traps such as phenyl tert-butylnitrone (PBN) are often reported to provide protection of the central nervous system of animal models against free radical damage, and the effects are attributed to its "antioxidant activity." The effects of PBN and p-CH(3)O-PBN were compared with known antioxidants, alpha-tocopherol and 2,2,5,7,8-pentamethyl-6-hydroxychroman (PMHC), in quantitative kinetic studies of lipid peroxidation thermally initiated under controlled conditions. Results obtained on the spin traps in organic solvents and in dilinoleoyl phosphatidylcholine (DLPC) bilayers indicated that the spin traps do not act as peroxyl radical trapping antioxidants but rather act only as moderate "retarders" of oxygen uptake at relatively high concentration. At low oxygen partial pressures, e.g., 14 torr, which better reflect oxygen partial pressures in biological systems, PBN provides a more significant reduction in oxygen uptake (up to 50%) by DLPC bilayers but still did not act as a typical antioxidant. However, at low partial pressures, PBN does act cooperatively with PMHC. It is suggested that its role in biological fluids and tissues may be to extend the suppressed oxidation by natural antioxidants expected to be present. The combination of antioxidant/spin trap, alpha-(3, 5-di-tert-butyl-4-hydroxyphenyl)-N-tert-butylnitrone did not exhibit any enhanced antioxidant efficiency compared with the related hindered phenol, 2,6-di-tert-butyl-4-methoxyphenol.     

Population dynamics and resource use of red deer after release from harvesting in New?Zealand

Despite periods of extensive government-funded control, fluctuating commercial exploitation and ongoing recreational hunting, little is known about how red deer (Cervus elaphus scoticus L?nnberg) in New?Zealand respond to the cessation of harvesting in terms of population growth rate and resource use. We describe the population dynamics and resource use of red deer in a montane catchment over 5?years (1962?67) following cessation of intensive government-funded control in 1961. Locations and sex?age classes of deer were observed monthly along a fixed route in the Harper-Avoca catchment, inland Canterbury. A total of 2036 red deer groups were observed. The number of groups observed annually increased during the study but no trends in median (2 or 3) or modal (1 or 2) group sizes were found. Population growth rates (r) of deer were extraordinarily high in the first two years (e.g. 2.33 ? 0.22 for adult females and 1.61 ? 0.23 for adult males), but decreased in subsequent years and were not biologically possible without substantial immigration and/or changes in detectability of deer. Sexual segregation and selection of vegetation types (alpine grassland, montane grassland, and forest) and 10 topographic landforms showed stronger intra-annual than inter-annual patterns. Segregation was greatest in spring and summer, least in the rut, and variable in winter. In all seasons, sexual segregation was greatest at 25- and 50-ha scales, moderate at 100-ha, and absent at the 500- and 1000-ha scales. Selection of vegetation types also varied seasonally, with deer of both sexes preferring montane grasslands in spring and summer and alpine grasslands in the rut. Backslopes were preferred landforms in spring and summer, spurs during spring and the rut, and hollows during the rut. Our results highlight the need to consider spatial scale, immigration, and detectability in the design of red deer culling and harvesting programmes. Studies of home-range size and use, migration patterns, dispersal rates and distances are required to better understand the impacts of red deer on New?Zealand ecosystems and the effects of management on red deer populations.     

Do the higher oxidation states of the photosynthetic O2-evolving system contain bound H2O?

A modified mass spectrometer was used to determine whether the higher oxidation states of the photosynthetic O2-evolving system contain substrate water that is not freely exchangeable with the external medium. Our data indicated that the higher oxidation states contain no appreciable bound, non-exchangeable H2O. This suggests that H2O oxidation takes place via a rapid, concerted, all-or-none mechanism rather than by a mechanism involving stable, partially oxidized, H2O-derived intermediates. These findings set definite constraints on possible mechanisms of O2 evolution.     

The rate of nitrite reduction in leaves as indicated by O₂ and CO₂ exchange during photosynthesis

Light response (at 300 ppm CO(2) and 10-50 ppm O(2) in N(2)) and CO(2) response curves [at absorbed photon fluence rate (PAD) of 550 μmol m(-2) s(-1)] of O(2) evolution and CO(2) uptake were measured in tobacco (Nicotiana tabacum L.) leaves grown on either NO(3)(-) or NH(4)(+) as N source and in potato (Solanum tuberosum L.), sorghum (Sorghum bicolor L. Moench), and amaranth (Amaranthus cruentus L.) leaves grown on NH(4)NO(3). Photosynthetic O(2) evolution in excess of CO(2) uptake was measured with a stabilized zirconia O(2) electrode and an infrared CO(2) analyser, respectively, and the difference assumed to represent the rate of electron flow to acceptors alternative to CO(2), mainly NO(2)(-), SO(4)(2-), and oxaloacetate. In NO(3)(-)-grown tobacco, as well as in sorghum, amaranth, and young potato, the photosynthetic O(2)-CO(2) flux difference rapidly increased to about 1 μmol m(-2) s(-1) at very low PADs and the process was saturated at 50 μmol quanta m(-2) s(-1). At higher PADs the O(2)-CO(2) flux difference continued to increase proportionally with the photosynthetic rate to a maximum of about 2 μmol m(-2) s(-1). In NH(4)(+)-grown tobacco, as well as in potato during tuber filling, the low-PAD component of surplus O(2) evolution was virtually absent. The low-PAD phase was ascribed to photoreduction of NO(2)(-) which successfully competes with CO(2) reduction and saturates at a rate of about 1 μmol O(2) m(-2) s(-1) (9% of the maximum O(2) evolution rate). The high-PAD component of about 1 μmol O(2) m(-2) s(-1), superimposed on NO(2)(-) reduction, may represent oxaloacetate reduction. The roles of NO(2)(-), oxaloacetate, and O(2) reduction in the regulation of ATP/NADPH balance are discussed.     

Do cytokinins function as two‐way signals between plants and animals?

Cytokinins are plant hormones that have, among many other functions, senescence‐modulatory effects in plant tissue. This is evident not only from biochemical data, but is vividly illustrated in the “green island” phenotype in plant leaves caused by cytokinins released for example by leaf mining insects or microbial pathogens. It is beyond doubt that, in addition to their roles in plants, cytokinins also provoke physiological and developmental effects in animals. It is hypothesized that the recently much discussed modification of plant metabolism by insects and associated microbes via cytokinin signals has a counterpart in direct cytokinin signalling that interferes with the animals’ hormonal systems and impacts their population dynamics.     

Carnosine,homocarnosine and anserine: could they act as antioxidants in vivo?

Carnosine, homocarnosine and anserine have been proposed to act as antioxidants in vivo. Our studies show that all three compounds are good scavengers of the hydroxyl radical (.OH) but that none of them can react with superoxide radical, hydrogen peroxide or hypochlorous acid at biologically significant rates. None of them can bind iron ions in ways that interfere with 'site-specific' iron-dependent radical damage to the sugar deoxyribose, nor can they restrict the availability of Cu2+ to phenanthroline. Homocarnosine has no effect on iron ion-dependent lipid peroxidation; carnosine and anserine have weak inhibitory effects when used at high concentrations in some (but not all) assay systems. However, the ability of these compounds to interfere with a commonly used version of the thiobarbituric acid (TBA) test may have led to an overestimate of their ability to inhibit lipid peroxidation in some previous studies. By contrast, histidine stimulated iron ion-dependent lipid peroxidation. It is concluded that, because of the high concentrations present in vivo, carnosine and anserine could conceivably act as physiological antioxidants by scavenging .OH, but that they do not have a broad spectrum of antioxidant activity, and their ability to inhibit lipid peroxidation is not well established. It may be that they have a function other than antioxidant protection (e.g. buffering), but that they are safer to accumulate than histidine, which has a marked pro-oxidant action upon iron ion-dependent lipid peroxidation. The inability of homocarnosine to react with HOCl, interfere with the TBA test or affect lipid peroxidation systems in the same way as carnosine is surprising in view of the apparent structural similarity between these two molecules.     

Do myc,fos and E1A function as protein phosphatase inhibitors?

The oncogenic proteins myc, fos and E1A bear striking resemblance to protein phosphatase inhibitors 1 and 2. Both sets of proteins possess several regions rich in proline (P), glutamic acid (E), serine (S) and threonine (T). In addition to PEST sequences four of the five proteins contain clusters of arginine-arginine pairs. On the basis of these similarities, I suggest that myc, fos and E1A are protein phosphatase inhibitors.     

Do fish communities function as biotic vectors of organic matter between salt marshes and marine coastal waters?

The contribution of fish communities to organic matter (OM) fluxes, especially between salt marshes and adjacent marine coastal waters are reviewed. For this a data set from the bay of Mont Saint-Michel and literature is examined and discussed. In a range of macro-tidal coasts of Europe, salt marshes are only flooded at spring tides for a short time. Many animals, including fish, then invade the salt marshes through tidal creeks. They forage there for up to a few hours and swim back to sea at ebb. Meanwhile, organic matter is exported as gut content. In the 4000 ha of salt marshes of the bay of Mont Saint-Michel mullets were responsible for the export of about 8 kg of dry weight OM ha^–1 in 1996 and of roughly 12 kg in 1997. Although spatio-temporally variable, the fish communities appear to play a more or less significant role, as biotic vectors in the nutrient fluxes between salt marshes and coastal waters.     

Demographic consequences of chromatic leaf defence in tropical tree communities: do red young leaves increase growth and survival?

Background

Many tropical forest tree species delay greening their leaves until full expansion. This strategy is thought to provide newly flushing leaves with protection against damage by herbivores by keeping young leaves devoid of nutritive value. Because young leaves suffer the greatest predation from invertebrate herbivores, delayed greening could prevent costly tissue loss. Many species that delay greening also produce anthocyanin pigments in their new leaves, giving them a reddish tint. These anthocyanins may be fungicidal, protect leaves against UV damage or make leaves cryptic to herbivores blind to the red part of the spectrum.

Methods

A comprehensive survey was undertaken of seedlings, saplings and mature trees in two diverse tropical forests: a rain forest in western Amazonia (Yasuní National Park, Ecuador) and a deciduous forest in Central America (Barro Colorado Island, Panamá). A test was made of whether individuals and species with delayed greening or red-coloured young leaves showed lower mortality or higher relative growth rates than species that did not.

Key results

At both Yasuní and Barro Colorado Island, species with delayed greening or red young leaves comprised significant proportions of the seedling and tree communities. At both sites, significantly lower mortality was found in seedlings and trees with delayed greening and red-coloured young leaves. While there was little effect of leaf colour on the production of new leaves of seedlings, diameter relative growth rates of small trees were lower in species with delayed greening and red-coloured young leaves than in species with regular green leaves, and this effect remained when the trade-off between mortality and growth was accounted for.

Conclusions

Herbivores exert strong selection pressure on seedlings for the expression of defence traits. A delayed greening or red-coloured young leaf strategy in seedlings appears to be associated with higher survival for a given growth rate, and may thus influence the species composition of later life stages.     

Polyphenol gene expression and changes in anthocyanins and polyphenols in the skin of ‘Braeburn’ apples after the autumn application of prohexadione-calcium

Prohexadione-calcium (Pro-Ca) transient inhibits 2-Oxoglutarate-dependent dioxygenases and causes significant changes in the flavonoid spectrum of apple. In the present study the influence of two autumn preharvest applications of Pro-Ca on the polyphenol metabolism in apple peel during the advanced maturation was investigated. Pro-Ca was sprayed in two doses, approximately five and 3 weeks before the technological maturity. Changes in the concentrations of hydroxycinnamic acids, dihydrochalcones, flavonols, flavanols and anthocyanins as well as their related gene expression and enzyme activities in the apple peel were monitored six times during the advanced maturation until the technological maturity of the fruits. To evaluate its influence on red coloration differences in the chromatic values a*, h° and L* between the treated and untreated apples were monitored. The parameters showed a temporary effect of Pro-Ca on the intensity of red coloration, which was not detected anymore at the technological maturity of apples. The application of Pro-Ca decreased the flavanone 3-hydroxylase activity and slightly inhibited activities of all the enzymes analyzed. Concomitantly, the concentrations of anthocyanins in the peel of the treated apples decreased, whereas the concentrations of hydroxycinnamic acids, dihydrochalcones and flavan 3-ols increased. Flavonol concentrations, however, remained unchanged. The expression of ANS, ANR, FGT and MYB10 was downregulated after the Pro-Ca treatment. The results indicate that the autumn application of Pro-Ca modulates the biosynthetic pathway resulting in distinct changes in the flavonoid composition in the apple peel of ‘Braeburn’ apples. However, the changes are temporary and are generally suspended during apple storage.