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PubMed1978

Responses of succulents to plant water stress.

Experiments were performed to test the hypothesis that succulents "shift" their method of photosynthetic metabolism in response to environmental change. Our data showed that there were at least three different responses of succulents to plant water status. When plant water status of Portulacaria afra (L.) Jacq. was lowered either by withholding water or by irrigating with 2% NaCl, a change from C(3)-photosynthesis to Crassulacean acid metabolism (CAM) occurred. Fluctuation of titratable acidity and nocturnal CO(2) uptake was induced in the stressed plants. Stressed Peperomia obtusifolia A. Dietr. plants showed a change from C(3)-photosynthesis to internal cycling of CO(2). Acid fluctuation commenced in response to stress but exogenous CO(2) uptake did not occur. Zygocactus truncatus Haworth plants showed a pattern of acid fluctuation and nocturnal CO(2) uptake typical of CAM even when well irrigated. The cacti converted from CAM to an internal CO(2) cycle similar to Peperomia when plants were water-stressed. Reverse phase gas exchange in succulents results in low water loss to carbon gain. Water is conserved and low levels of metabolic activity are maintained during drought periods by complete stomatal closure and continual fluctuation of organic acids.

Journal Article↗
PubMed2006

Ethnomedicines used in Trinidad and Tobago for urinary problems and diabetes mellitus.

BACKGROUND: This paper is based on ethnobotanical interviews conducted from 1996-2000 in Trinidad and Tobago with thirty male and female respondents. METHODS: A non-experimental validation was conducted on the plants used for urinary problems and diabetes mellitus: This is a preliminary step to establish that the plants used are safe or effective, to help direct clinical trials, and to inform Caribbean physicians of the plants' known properties to avoid counter-prescribing. RESULTS: The following plants are used to treat diabetes: Antigonon leptopus, Bidens alba, Bidens pilosa, Bixa orellana, Bontia daphnoides, Carica papaya, Catharanthus roseus, Cocos nucifera, Gomphrena globosa, Laportea aestuans, Momordica charantia, Morus alba, Phyllanthus urinaria and Spiranthes acaulis. Apium graviolens is used as a heart tonic and for low blood pressure. Bixa orellana, Bontia daphnoides, Cuscuta americana and Gomphrena globosa are used for jaundice. The following plants are used for hypertension: Aloe vera, Annona muricata, Artocarpus altilis, Bixa orellana, Bidens alba, Bidens pilosa, Bonta daphnoides, Carica papaya, Cecropia peltata, Citrus paradisi, Cola nitida, Crescentia cujete, Gomphrena globosa, Hibiscus sabdariffa, Kalanchoe pinnata, Morus alba, Nopalea cochinellifera, Ocimum campechianum, Passiflora quadrangularis, Persea americana and Tamarindus indicus. The plants used for kidney problems are Theobroma cacao, Chamaesyce hirta, Flemingia strobilifera, Peperomia rotundifolia, Petiveria alliacea, Nopalea cochinellifera, Apium graveolens, Cynodon dactylon, Eleusine indica, Gomphrena globosa, Pityrogramma calomelanos and Vetiveria zizanioides. Plants are also used for gall stones and for cooling. CONCLUSION: Chamaesyce hirta, Cissus verticillata, Kalanchoe pinnata, Peperomia spp., Portulaca oleraceae, Scoparia dulcis, and Zea mays have sufficient evidence to support their traditional use for urinary problems, "cooling" and high cholesterol. Eggplant extract as a hypocholesterolemic agent has some support but needs more study. The plants used for hypertension, jaundice and diabetes that may be safe and justify more formal evaluation are Annona squamosa, Aloe vera, Apium graveolens, Bidens alba, Carica papaya, Catharanthus roseus, Cecropia peltata, Citrus paradisi, Hibsicus sabdariffa, Momordica charantia, Morus alba, Persea americana, Phyllanthus urinaria, Tamarindus indicus and Tournefortia hirsutissima. Several of the plants are used for more than one condition and further trials should take this into account.

Diabetes Mellitus↗
PubMed2003

Epiphytic and terrestrial mycorrhizas in a lower montane Costa Rican cloud forest.

The epiphyte community is the most diverse plant community in neotropical cloud forests and its collective biomass can exceed that of the terrestrial shrubs and herbs. However, little is known about the role of mycorrhizas in this community. We assessed the mycorrhizal status of epiphytic (Araceae, Clusiaceae, Ericaceae, and Piperaceae) and terrestrial (Clusiaceae, Ericaceae) plants in a lower montane cloud forest in Costa Rica. Arbuscular mycorrhizas were observed in taxa from Araceae and Clusiaceae; ericoid mycorrhizas were observed in ericaceous plants. This is the first report of intracellular hyphal coils characteristic of ericoid mycorrhizas in roots of Cavendishia melastomoides, Disterigma humboldtii, and Gaultheria erecta. Ericaceous roots were also covered by an intermittent hyphal mantle that penetrated between epidermal cells. Mantles, observed uniquely on ericaceous roots, were more abundant on terrestrial than on epiphytic roots. Mantle abundance was negatively correlated with gravimetric soil water content for epiphytic samples. Dark septate endophytic (DSE) fungi colonized roots of all four families. For the common epiphyte D. humboldtii, DSE structures were most abundant on samples collected from exposed microsites in the canopy. The presence of mycorrhizas in all epiphytes except Peperomia sp. suggests that inoculum levels and environmental conditions in the canopy of tropical cloud forests are generally conducive to the formation of mycorrhizas. These may impact nutrient and water dynamics in arboreal ecosystems.

Araceae↗
PubMed1976

Photoinduction kinetics of electrical potential in a single chloroplast as studied with micro-electrode technique.

1. Using single chloroplasts of Peperomia metallica the kinetics of light-induced potential changes were studied. Three kinetic components (the initial fast rise, the decay in the light and the decay in the dark) were found to be characterized by time constants 4, 220 and 60 ms, respectively at light intensity 5000 1x and temperature 18 degrees C. After flash excitation the potential kept on rising for about 10 ms. Cooling of the medium down to 5 degrees C had no effect on the duration of potential rise after the flash. 2. Variations in the medium temperature in the range 2-23 degrees C had little effect on photoresponse magnitude but resulted in significant acceleration of decay in the light. 3. Addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (5-)0(-6) M) resulted in suppression of the magnitude of the photoresponse but was not accompanied by any change in the rate of initial rise of potential. 3-(3,4-Dichlorophenyl)-1,1-dimethylurea-inhibited photoresponse could be restored and even enhanced by subsequent addition of N-methylphenazonium methosulfate (10(-4) M). N-Methylphenazonium methosulfate essentially influenced the time course and light-intensity curves of photoresponse. 4. The chloroplast photoresponses were of different time-courses when elicited by red (640 nm) or far red (712 nm) light. This fact as well as an enhancement effect of combined illumination by two intermittent light beams indicate on the interaction of two photosynthetic pigment systems when the photoelectric response was formed. 5. An imposed electrical field resulted in stimulation or suppression of chloroplast photoresponse depending on the polarity of the field. No indications for the existance of "reversal potential" for photoelectric response were obtained. 6. A kinetic scheme of photoresponse formation is proposed, which includes two sequential photochemical reactions of photosynthesis.

Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone↗
PubMed1976

The effect of cations and membrane permeability modifying agents on the dark kinetics of the photoelectric response in isolated chloroplasts.

The kinetics of the photoelectric response induced by saturating light pulses were studied in isolated chloroplasts of Peperomia metallica as a function of K+- and Mg2+-concentrations in the medium in the absence and presence of ionophores for K+ and divalent cations. The dark decay of the potential generated in the light is found to be accelerated upon an increase in K+- or Mg2+-concentrations in the presence of valinomycin and A23187. An acceleration of the decay phase in the flash-induced response is also observed immediately after preillumination of the chloroplast. It is concluded that the dark kinetics of the potential decay after short and long light exposures are controlled by two different processes with rate constants of about 20 and 0.2s-1, respectively.

Calcimycin↗
PubMed2000

A three-state model for energy trapping and chlorophyll fluorescence in photosystem II incorporating radical pair recombination.

The multiphasic fluorescence induction kinetics upon a high intensity light pulse have been measured and analyzed at a time resolution of 10 micros in intact leaves of Peperomia metallica and Chenopodium album and in chloroplasts isolated from the latter. Current theories and models on the relation between chlorophyll fluorescence yield and primary photochemistry in photosystem II (PSII) are inadequate to describe changes in the initial phase of fluorescence induction and in the dark fluorescence level F(0) caused by pre-energization of the system with single turnover excitation(s). A novel model is presented, which gives a quantitative relation between the efficiencies of primary photochemistry, energy trapping, and radical pair recombination in PSII. The model takes into account that at least two turnovers are required for stationary closure of a reaction center. An open reaction center is transferred with high efficiency into its semiclosed (-open) state. This state is characterized by Q(A) and P680 in the fully reduced state and a lifetime equal to the inverse of the rate constant of Q(A)(-) oxidation (approx. 250 micros). The fluorescence yield of the system with 100% of the centers in the semiclosed state is 50% of the maximal yield with all centers in the closed state at fluorescence level F(m). A situation with approximately 100% of the centers in the semiclosed state is reached after a single turnover excitation in the presence of 3-(3',4'-dichlorophenyl)-1,1-dimethylurea (DCMU). The lifetime of this state under these conditions is approximately 10 s. Closure of a semiclosed (-open) center occurs with low efficiency in a second turnover. The low(er) efficiency is caused by the rate of P(+) reduction by the secondary donor Y(Z) being competitive with the rate of radical pair recombination in second and following turnovers. The single-turnover-induced alterations in the initial kinetics of the fluorescence concomitantly with a 15-25% increase in F(o) can be simulated with the present so called three-state model of energy trapping. The experimental data suggest evidence for an electrostatic effect of local charges in the vicinity of the reaction center affecting the rate of radical pair recombination in the reaction center.

Chenopodiaceae↗
PubMed2001

Essential oil analysis of 10 Piperaceae species from the Brazilian Atlantic forest.

The volatile composition of ten Piperaceae species, comprising three genera (Ottonia, Piper and Peperomia) has been studied. The species were collected in a typical fragment of the Brazilian Atlantic forest, constantly being damaged by human action. The essential oils were obtained by hydrodistillation in a modified Clevenger-type apparatus and their analyses were performed by GC and GC/MS. Identification of the substances was made by comparison of mass spectra and retention indices with literature records. A great number of non-oxygenated monoterpenes and sesquiterpenes were identified. Most of these sesquiterpenes are derived from E,E-farnesyl-PP, suggesting a preference of these species to synthesize metabolites from this pathway. Arylpropanoids, although being common compounds produced by Piperaceae species, were not found in these oils.

Brazil↗
PubMed2001

Modulation of photosystem II chlorophyll fluorescence by electrogenic events generated by photosystem I.

In an attempt to uncover electric field interactions between PS I and PS II during their functioning, fluorescence induction curves were measured on hydroxylamine-treated thylakoids of Chenopodium album under conditions ensuring low and high levels of photogenerated membrane potentials. In parallel experiments with Peperomia metallica chloroplasts, the photocurrents were measured with patch-clamp electrodes and served as indicator of electrogenic activity of thylakoid membranes in continuous light. Inhibition of linear electron flow at PS II donor side by hydroxylamine (0.1 mM) eliminated a slow rise of chlorophyll fluorescence to a peak level and suppressed photoelectrogenesis. Activation of PS I-dependent electron transport using cofactors of either cyclic (phenazine methosulfate) or noncyclic electron transport (reduced TMPD or DCPIP in combination with methyl viologen) restored photoelectrogenesis in hydroxylamine-treated chloroplasts and led to reappearance of slow components in the fluorescence induction curve. Exposure of thylakoids to valinomycin reduced the peak fluorescence in the presence of KCl but not in the absence of KCl. Combined application of valinomycin and nigericin in the presence of KCl exerted stronger suppression of fluorescence than valinomycin alone but was ineffective in the absence of KCl. In samples treated with hydroxylamine and PS I cofactors (DCPIP/ascorbate and methyl viologen), preillumination with a single-turnover flash or a multiturnover pulse shifted the induction curves of both membrane potential and chlorophyll fluorescence to shorter times, which confirms the supposed influence of PS I-generated electrical field on PS II fluorescence. A model is presented that describes modulating effect of the membrane potential on chlorophyll fluorescence and roughly simulates the fluorescence induction curves measured at low and high membrane potentials.

Chenopodium album↗
PubMed1998

Explosive invasion of plant mitochondria by a group I intron.

Group I introns are mobile, self-splicing genetic elements found principally in organellar genomes and nuclear rRNA genes. The only group I intron known from mitochondrial genomes of vascular plants is located in the cox1 gene of Peperomia, where it is thought to have been recently acquired by lateral transfer from a fungal donor. Southern-blot surveys of 335 diverse genera of land plants now show that this intron is in fact widespread among angiosperm cox1 genes, but with an exceptionally patchy phylogenetic distribution. Four lines of evidence-the intron's highly disjunct distribution, many incongruencies between intron and organismal phylogenies, and two sources of evidence from exonic coconversion tracts-lead us to conclude that the 48 angiosperm genera found to contain this cox1 intron acquired it by 32 separate horizontal transfer events. Extrapolating to the over 13,500 genera of angiosperms, we estimate that this intron has invaded cox1 genes by cross-species horizontal transfer over 1,000 times during angiosperm evolution. This massive wave of lateral transfers is of entirely recent occurrence, perhaps triggered by some key shift in the intron's invasiveness within angiosperms.

Base Sequence↗
PubMed1970

Transient heat and mass transfer from a leaf undergoing stomatal closure in a low pressure environment.

Stomatal control of water loss was studied in a low pressure environment by using detached leaves of Crassula argentea Thunb., Peperomia obtusifolia (L.) A. Dietr., and Setcreasea pallida Rose cv. ;Purple Heart.' The transient behavior of temperature and rate of mass loss were determined. A model based on free molecule gas flow was developed and used to predict mass loss to within the same order of magnitude of experimentally obtained results. By utilizing this model, the transient behavior of stomatal aperture was determined. The "nonphysiological" experimental conditions do not inhibit the closing process; therefore, this new experimental technique is a valid method of studying stomatal closure.

Journal Article↗
PubMed2007

Comparison of plants used for skin and stomach problems in Trinidad and Tobago with Asian ethnomedicine.

This paper provides a preliminary evaluation of fifty-eight ethnomedicinal plants used in Trinidad and Tobago for skin problems, stomach problems, pain and internal parasites for safety and possible efficacy. Thirty respondents, ten of whom were male were interviewed from September 1996 to September 2000 on medicinal plant use for health problems. The respondents were obtained by snowball sampling, and were found in thirteen different sites, 12 in Trinidad and one in Tobago. The uses are compared to those current in Asia. Bambusa vulgaris, Bidens alba, Jatropha curcas, Neurolaena lobata, Peperomia rotundifolia and Phyllanthus urinaria are possibly efficacious for stomach problems, pain and internal parasites. Further scientific study of these plants is warranted.

Anthropology, Cultural↗
PubMed1977

Comparison of vegetative anatomy of Piperales. II. Leaf.

Many characters of leaf (hair, hypodermal cells, palisade layers, intercellular space, distinction between spongy and palisade parenchyma, "palisade ratio", distribution of collenchyma and sclerenchyma, presence or absence of starch grains, calcium oxalate crystals, number, shape and arrangement of bundles of petiole) are useful distinguishing characters. Reduction of palisade layers seems to be the trend of evolution in Piper and Peperomia.

Plants↗
PubMed1981

[Light-induced generation of membrane potential in intact chloroplasts suspended in H2O or D2O media].

The membrane potential changes induced by short flashes and continuous light were investigated in isolated chloroplasts of Peperomia metallica suspended in H2O- or D2O media. The potential generated in H2O-suspended chloroplasts by a single turnover flash is approximately two times lower than the maximal level of potential induced by continuous light. The photoelectric response of D2O-suspended chloroplasts differs from that of H2O-suspended chloroplasts by an increased amplitude and a prolonged phase of the potential rise. Te dark decay of the potential proceeds 2-3 times slower in the D2O-suspended chloroplasts as compared to the H2O-suspended chloroplasts. The magnitude of the flash-induced potential is somewhat lower for the chloroplasts in D2O than for the chloroplasts in the H2O medium. The results obtained suggest that the substitution of H2O for D2O results in a decrease of the ionic conductance and an increase of stability of thylakoid membranes. It was shown that the rise of electrical potential under continuous illumination proceeds in two stages. The difference kinetics of membrane potential changes are observed under conditions of separate activity of two systems of photosynthesis.

Chloroplasts↗