Leonor Alegre

University of Barcelona | UB · Department of Chemical Engineering

Vitamin E, a potent antioxidant either present in the form of tocopherols and/or tocotrienols depending on the plant species, tissue and developmental stage, plays a major role in protecting lipids from oxidation in seeds. Unlike tocopherols, which have a more universal distribution, the occurrence of tocotrienols is limited primarily to monocot se...

Background: Population structure and dynamics in natural ecosystems can be affected by seed viability and dormancy. However, how the endogenous contents of phytohormones and vitamin E in seeds relative to the environment affect viability and dormancy is not yet fully understood. Aims: We studied seed viability and germination capacity in two popul...

Chamaerops humilis (L.), the only dwarf palm native of continental Europe that is found in the Iberian Peninsula, accumulates tocotrienols rather than tocopherols in quiescent seeds, as it occurs in other monocots. To unravel the protective role of either tocopherols or tocotrienols against lipid peroxidation during seed germination; seed viability...

Main conclusion The interaction between enzymatic and non-enzymatic antioxidants, endogenous levels of ABA and ABA-GE, the rapid recuperation of photosynthetic proteins under re-watering as well the high level of antioxidant proteins in previously drought-stressed plants under re-watering conditions, will contribute to drought resistance in plants...

Using Arabidopsis plants Col-0 and vtc2 transformed with a redox sensitive green fluorescent protein, (c-roGFP) and (m-roGFP), we investigated the effects of a progressive water stress and re-watering on the redox status of the cytosol and the mitochondria. Our results establish that water stress affects redox status differently in these two compar...

Plants possess a battery of structural, physiological, biochemical, and molecular mechanisms to withstand drought periods. During drought, stomatal limitation of photosynthesis, overreduction of the photosynthetic electron transport chain, enhanced photorespiration, and many other processes may result on enhanced formation of reactive oxygen specie...

The interplay between jasmonic acid (JA) and abscisic acid (ABA) in plant responses to water stress and in water-stress-enhanced oxidative stress was investigated in Arabidopsis thaliana plants subjected to water stress by water deprivation. For this purpose a drought assay was conducted using Arabidopsis mutants impaired in ABA (aba2), JA (aos), a...

Physiological studies on aging in perennials are mainly focused either on the primary metabolism or the hormonal regulation of the process. However, to our knowledge, the involvement of the secondary metabolism in this process has not yet been explored. Cistus clusii, a Mediterranean sclerophyllous evergreen bush, shows considerable amounts of flav...

Here we examined the contribution of methyl jasmonate (MeJA) to the acclimation of a Mediterranean shrub, Cistus albidus L., to water stress under natural climatic conditions. For this purpose, changes in MeJA, hydrogen peroxide (H2O2), ascorbate (AA) and the maximum efficiency of PSII photochemistry (Fv/Fm ratio) and lipid peroxidation were monito...

Referee: Dr. Kozi Asada, Department of Biotechnology, Faculty of Engineering, Fukuyama University, Gakuencho 1, Fukuyama 729-0292, Japan Tocopherols and tocotrienols, which differ only in the degree of saturation of their hydrophobic prenyl side chains, are lipid-soluble molecules that have a number of functions in plants. Synthesized from homogent...

Abiotic stresses, such as drought, can increase the production of reactive oxygen species (ROS) in plants. An increase in ROS levels can provoke a partial or severe oxidation of cellular components inducing redox status changes, so continuous control of ROS and therefore of their metabolism is decisive under stress conditions. The present work focu...

Flavonoids are a large family of plant secondary metabolites, principally recognized for their health-promoting properties in human diets. Most flavonoids outperform well-known antioxidants, such as ascorbate (vitamin C) and alpha-tocopherol (vitamin E), in in vitro antioxidant assays because of their strong capacity to donate electrons or hydrogen...

BACKGROUND: Carnosic acid and carnosol, the two major phenolic diterpenes present in rosemary and sage extracts, have received attention in food science and biomedicine because of their potent antioxidant properties. In plants, these compounds have been identified as being present in some species of the family Lamiaceae, but there is still little i...

This study evaluated the possible role of hydrogen peroxide (H2O2) in the acclimation of a Mediterranean shrub, Cistus albidus L., to summer drought growing under Mediterranean field conditions. For this purpose, changes in H2O2 concentrations and localization throughout a year were analysed. H2O2 changes in response to environmental conditions in...

Most studies on the function of tocopherols in plants have focused on their photo-protective and antioxidant properties, and it has been recently suggested, though not yet demonstrated, that they may also play a role in cellular signaling. By using vte1 mutants of Arabidopsis thaliana, with an insertion in the promoter region of the gene encoding t...

(-)-Epicatechin (EC) and (-)-epigallocatechin gallate (EGCG), two major tea flavan-3-ols, have received attention in food science and biomedicine because of their potent antioxidant properties. In plants, flavan-3-ols serve as proanthocyanidin (PA) building blocks, and although both monomeric flavan-3-ols and PAs show antioxidant activity in vitro,...

Photosynthesis operates in a constantly shifting balance between efficient capture of solar energy and its rapid dissipation when captured in excess. In an attempt to better understand the role of alpha-tocopherol in plant photoprotection, we examined the changes in alpha-tocopherol quinone (alpha-TQ), in parallel with those of other low-molecular-...

Abscisic acid (ABA) accumulation has been analyzed in irrigated and water-stressed wild-type and the vtc-1 mutant of Arabidopsis thaliana, which shows an ascorbate deficiency in leaves of approximately 60%. The amounts of ABA increased progressively up to 2.3-fold in water-stressed wild-type plants, whereas levels were kept at low levels in the irr...

Mediterranean plants have evolved a complex antioxidant defense system to cope with summer drought. Flavonoids, and particularly flavanols and flavonols, are potent in vitro antioxidants, but their in vivo significance within the complex network of antioxidant defenses remains unclear, especially in plant responses to stress. To gain insight into t...

Leaf senescence is a highly regulated physiological process that leads to leaf death and is, as such, the last developmental stage of the leaf. Plant aging and environmental stresses may induce the process of senescence. Here we will focus on the role of leaf senescence in field-grown plants as a response to adverse climatic conditions and, more sp...

To assess antioxidative protection by carnosic acid (CA) in combination with that of other low-molecular weight (M(r)) antioxidants (alpha-tocopherol [alpha-T] and ascorbate [Asc]) in chloroplasts, we measured endogenous concentrations of these antioxidants, their redox states, and other indicators of oxidative stress in chloroplasts of three Labia...

Mechanisms of drought stress resistance were studied in Cistus clusii Dunal and Cistus albidus L., two native Mediterranean shrubs that can withstand severe summer drought. While water deficit, solar radiation and temperature increased from winter to summer in the field, C. clusii and C. albidus reduced leaf area, increased root mass per leaf area,...

The effects of low ascorbic acid (Asc) on lipophilic antioxidant defences and lipid peroxidation in chloroplasts were evaluated in the vtc-1 mutant of Arabidopsis thaliana, which had an Asc deficiency in chloroplasts of ca. 60%. Although low Asc did not cause oxidative stress in optimal growth conditions, it increased malondialdehyde levels in chlo...

Summary • The effects are reported here of inoculation with the soil-borne pathogen Fusarium oxysporum f. sp. lycopersici race 1 (FOL-1) on the photosynthetic capacity of tomato plants (Lycopersicon esculentum cv. Roma). • Plants were grown in cork compost with a pathogen concentration of c. 1 × 105 cfu ml−1, or without the fungus, for 31 d in cont...

The endogenous concentrations of ACC and ABA were measured, at predawn and at maximum solar radiation, during a summer drought, and recovery after autumn rainfalls, in rosemary (Rosmarinus officinalis L.), a drought-tolerant species, growing under Mediterranean field conditions. During the summer, plants were subjected to both water deficit and hig...

Aging has received considerable attention in biomedicine, but little is known about the regulatory mechanisms responsible for the aging not associated with senescence in plants. This study provides new insights into the relationship between oxidative stress and plant aging, and points out chloroplasts as one of the target organelles of age-associat...

The effects of summer drought, dew deposition on leaves and autumn rainfall on plant water relations and diurnal variations of photosynthesis were measured in two evergreen shrubs, rosemary (Rosmarinus officinalis) and lavender (Lavandula stoechas), grown in Mediterranean field conditions. Withholding water for 40 d caused a similar decrease in pre...

In the Mediterranean, annual mean precipitation has continuously decreased over the last three years (by ca 36% in Barcelona), and the decrease has been dramatic during the summer (by ca 78 and 64% during July and August, respectively). The impact of increased drought on the photosynthetic capacity of Mediterranean vegetation is currently unknown....

The relationship between drought, oxidative stress and leaf senescence was evaluated in field-grown sage (Salvia officinalis L.), a drought-susceptible species that shows symptoms of senescence when exposed to stress. Despite the photoprotection conferred by the xanthophyll cycle, drought-stressed senescing leaves showed enhanced lipid peroxidation...

Previous studies have shown that diterpene carnosic acid plays a role as an antioxidant in rosemary, a drought-tolerant species. However, this mechanism has not been tested so far in other species. The endogenous levels of diterpene carnosic acid and α-tocopherol, which are lipophilic antioxidants found in chloroplasts, were measured in a drought-r...

α-Tocopherol (vitamin E) is a lipophilic antioxidant, which protects chloroplasts from oxidative damage. Diurnal variations in α-tocopherol, chlorophylls and carbon dioxide assimilation rates were measured during two consecutive summers to evaluate the photosynthetic response to drought and the protective role of α-tocopherol in 2- and 3-year-old l...

The potent antioxidant properties of rosemary (Rosmarinus officinalis) extracts have been attributed to its major diterpene, carnosic acid. Carnosic acid has received considerable attention in food science and biomedicine, but little is known about its function in the plant in vivo. We recently found that highly oxidized diterpenes increase in rose...

Effects of drought on water relations, whole-shoot gas-exchange characteristics, and pigment and zeatin concentrations were investigated in the Mediterranean shrubs rosemary (Rosmarinus officinalis L.) and lavender (Lavandula stoechas L.). Two-year-old, greenhouse-grown plants were placed in a whole-shoot gas-exchange measurement system and subject...

Two-year-old rosemary (Rosmarinus officinalis L.) plants were subjected to severe stress by exposure to prolonged drought during a Mediterranean summer. Severely stressed plants recovered completely after the autumn rainfalls although the relative water content remained below 35% for 3 months and the chlorophyll content of leaves was reduced by up...

Diurnal variations in pigment composition, α-tocopherol and photosynthesis were measured during the summer drought and recovery after autumn rainfalls in Melissa officinalis L. grown under Mediterranean climate. Summer drought caused a drastic decrease in relative water content and water potential of leaves to ca 35% and −3 MPa respectively, indica...

 The formation of phenolic diterpenes in the leaves of rosemary plants grown under Mediterranean climate was investigated. Low precipitation coincided with high solar radiation during the summer, resulting in water and light stress of the plants. The highest concentrations of the major diterpenes carnosic acid and carnosol were found during the win...

The water relations, the photosynthetic capacity and the pigment content of leaves, i.e. chlorophylls, carotenes and xanthophylls, were analysed during the summer drought and recovery after autumn rainfalls in lavender (Lavandula stoechas L.) plants grown in Mediterranean field conditions. Summer drought caused photoinhibition of photosynthesis and...

Abietane diterpenes were measured in field-grown rosemary (Rosmarinus officinalis L.) plants throughout the year. Carnosic acid and carnosol, which were present in high amounts (5 and 1 mg/gDW respectively) in rosemary leaves, decreased by ca. 50% during the Mediterranean summer in response to low precipitation, high radiation and high temperature....

Diurnal variations in pigment composition, alpha-tocopherol and photosynthesis were measured during the summer drought and recovery after autumn rainfalls in Melissa officinalis L. grown under Mediterranean climate. Summer drought caused a drastic decrease in relative water content and water potential of leaves to ca 35% and -3 MPa respectively, in...

The lipid-soluble antioxidants alpha-tocopherol and carnosic acid were studied in field-grown rosemary (Rosmarinus officinalis L.) plants subjected to drought. During summer in the Mediterranean region, the predawn water potential decreased to -3 MPa and the relative water content to 42%, which caused a depletion of the maximum diurnal CO(2) assimi...

Summer diurnal variations of photosynthesis and α-tocopherol content were measured in relation to natural drought in field-grown rosemary (Rosmarinus officinalis L.) and lemon balm (Melissa officinalis L.) plants. During the summer relative water contents (RWC) of ca. 40% in Rosmarinus officinalis and ca. 30% in Melissa officinalis were attained, i...

The effect of drought and simulated daily dew on the water relations and photosynthetic capacity of lemon balm plants (Melissa officinalis L.) grown in Mediterranean field conditions was evaluated. Drought stress during the summer caused a large decrease in xilematic water potential (Ψw) and relative water content of leaves (RWC), and values around...

The relationship between the bulk abscisic acid (ABA) content, ABA compartmental redistribution, and chloroplast ultrastructural changes was studied in leaves of lavender (Lavandula stoechas L.) plants subjected to water stress. ABA was uniformly distributed in the cytosol, nucleus, chloroplasts, and cell walls of mesophyll cells in well-watered pl...

The effect of water deficit on gas exchange in Mediterranean vegetation has been widely reviewed by a number of authors (1,2). Drought affects not only the rate of gas exchange, but also results in diurnal changes in activity (3,4).

Seasonal changes in leaf anatomy and ultrastructure were studied in a sward of Cynodon dactylon (L.) Pers. grown under Mediterranean field conditions and under water stress. Relative water content (RWC), leaf water potential (ψ), and specific leaf weight were determined. Anatomical measurements included leaf thickness and number and area of bundle...

The effect of water stress on plant water status and net photosynthetic gas exchange (PN) in six barley genotypes (Hordeum vulgare L.) differing in productivity and drought tolerance was studied in a controlled growth chamber. Osmotic adjustment (OA), PN, stomatal conductance (gs), and the ratio intercellular/ambient. CO2 concentration (Ci/Ca) were...

Water stress induced an increase in endogenous concentrations of ABA in Lavandula stoechas L. plants to 13100 pmol ABA g–1 FW, which may contribute to the maintenance of water relations between the second and the third day of water stress treatment. After the third day, a sharp decrease in ABA levels was observed to 2630 pmol ABA g–1 FW, together w...

Fuzzy-logic-based expert systems assist Brazilian engineers with the drilling, pumping, and processing of offshore oil, cutting costs without compromising safety. The authors discuss these applications of fuzzy logic control

Seasonal changes in water relations, production and mineral composition were studied in a sward ofCynodon dactylon (L). Pers. subjected to water deficits during a dry summer, and at recovery in autumn. The experiment was carried out under Mediterranean field conditions. Water deficits during summer reduced total dry matter production by 60%, but in...

A monoclonal antibody was used to localize abscisic acid in Lavandula stoechas L. plants treated with 1 M abscisic acid. ABA localization was performed using EDC as the only fixative, which preserves antigenicity and improves the specificity of monoclonal antibodies. A relationship was observed between the effect of abscisic acid on chloroplast ult...

The retention of aerosols by canopies of holm oak trees in a typical Mediterranean forest is studied. Firstly, dry deposition is measured both under and outside the canopy during several months. No clear differences are observed either in the amount or in the chemical composition of the particles collected under and outside the canopy. Secondly, th...

Ultrastructural alterations in epidermal and mesophyll cells as well as variations in bulk leaf endogenous ABA and IAA concentrations were studied in PEG-treated plants of Fatsia japonica Decne & Plank. Under stress induced by PEG vesicles containing fibrous material and electron-dense bodies associated with plasma membranes were observed. Cytochem...

Ultrastructural alterations in mesophyll cells as well as variations in bulk leaf endogenous ABA and IAA concentrations were studied in water-stressed field-grown plants of Fatsia japonica. Under water deficit cellular membranes were modified and an increase in vesicles was observed. The main damage to the chloroplasts included thylakoid swelling a...

The effect of drought on the photosynthetic functioning of twenty genotypes of barley (Hordeum vulgare L.) was examined using a modulated fluorescence technique coupled to measurements of simple fluorescence, net photosynthesis and leaf water potential. While any of these parameters can be used to score genotypes with extreme responses to water str...

Plant-water relationships, leaf morphology and concentrations of pigments, proline, solu- ble sugars, anthocyans and nutrients of after wildfire resprout leaves of Arbutus unedo L. were com- pared with those of same age sprout leaves in unbumed plants. In spring samples, several significant differences appear: after-fire resprouts showed some juven...

Diurnal variations in endogenous IAA levels inFatsia japonica leaves, maintaining constant other external factors such as temperature and relative humidity, were studied. Plants were cultivated in a growth chamber (20 °C, 75 % RH, 16 h photoperiod, 400 µmol m-2 s-1 PAR). IAA analyses were carried out by analytical IP-HPLC with on-line spectrofluori...

Comparisons of leaf structure and gas exchange characteristics have been made between flag leaves of four old genotypes of cultivated tetraploid wheats and three current varieties of hexaploid Triticum aestivum grown under Mediterranean climate conditions. For some genotypes the effect of varying the sowing date was investigated. In the hexaploid w...

Leaf structure, photosynthetic characteristics and related physiological parameters have been studied in three ornamental shade species: Fatsia japonica, Cissus rhombifolia (relatively light-tolerant plants), and Philodendron scandens (obligate shade plant). Species were grown in a shadehouse. Maximum photosynthetic photon flux density was 470 μmol...

Net photosynthesis rate (Pn), stomatal conductance to CO2 and residual conductance to CO2 were measured in the last six leaves (the sixth or flag leaf and the preceding five leaves) of Triticum aestivum L. cv. Kolibri plants grown in Mediterranean conditions. Recently fully expanded leaves of well-watered plants were always used. Measurements were...

Formation of phenolic diterpenes in Salvia officinalis L. plants In the recent years interest has increased in phenolic diterpenes from sage and rosemary. The high antioxidative activity of diterpenes is caused by the scavenging of reactive oxygen species. In this study the formation of phenolic diterpenes in leaves of sage plants under drought str...