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A Calatayud

Publications and source records attributed to A Calatayud.

8 recordsLinked to original sources
PubMed2006

Spatial-temporal variations in rose leaves under water stress conditions studied by chlorophyll fluorescence imaging.

Spatial-temporal changes were examined by imaging chlorophyll (Chl) a fluorescence in four leaf areas, two central and two external of rose plants (Rosa x hybrida) cv. Grand Gala for 9 days, under progressive water stress. New fluorescence parameters based on the lake model have recently been used to determine Q(A) redox state and excitation energy fluxes in order to gain a better understanding of the mechanisms that occur under drought stress. Chlorophyll fluorescence images showed a spatial variation in the leaves. The lower values for F(o), F(M), phi(2), q(P) and q(L) were found in the internal leaf area while higher values of non-photochemical quenching calculated from Stern-Volmer quenching (NPQ) and phi(NPQ). phi(Po) were more homogeneous throughout leaf. Temporal changes were also observed during the experiment, a 10% decrease in relative water content (RWC) (between day 1 and 2), led to a decrease in photochemical quenching and an increase in non-photochemical processes. Chlorophyll fluorescence parameters were more or less constant till day 8. At the end of the experiment (day 9), energy dissipation by downregulation, electron transport and Q(A) redox state, decreased and phi(NO) increased to compensate the change. Chlorophyll fluorescence parameters based on the lake model q(L), phi(NPQ) and phi(NO) have been found more appropriate for estimating the fraction of open centres, the quantum yield of regulated energy dissipation in photosystem II (PSII) and the quantum yield of non-regulated energy dissipation in PSII, respectively. The F(s)/F(o) ratio is strongly correlated with NPQ and phi(NPQ) up to a RWC of 20%. This coincides with a greater decrease in photochemical quenching and non-photochemical quenching and an increase in phi(NO).

Chlorophyll↗
PubMed2001

Chlorophyll a fluorescence, antioxidant enzymes and lipid peroxidation in tomato in response to ozone and benomyl.

Ozone is a widely distributed phytotoxic air pollutant and is known to reduce the yield of several important agricultural crops in Spain. However, benomyl has been found to lessen the adverse impact of ozone on plants. We studied the effects of ozone and benomyl on chlorophyll a fluorescence, antioxidant enzymes, and lipid peroxidation in tomato (Lycopersicon esculentum Mill. cv. Tiny Tim) grown in open-top chambers in the field. Our results indicate that benomyl prevented the peroxidation of membrane lipids and increased protection of PSII from ozone. There was also a significant reduction in the activity of the antioxidant enzyme superoxide dismutase in ozone-exposed plants that had not been treated with benomyl. Comparing plants treated with benomyl to untreated plants we found that, on exposure to ozone, a greater fraction of light absorption energy was cycled through the photosynthetic system in benomyl-treated plants, as shown by the higher PSII-mediated electron flow and the higher fraction of open PSII reaction centers. The values analyzed in the fluorescence parameters and lipid peroxidation were similar for plants without benomyl grown in a charcoal-filtered environment and benomyl-treated plants exposed to ozone.

Air Pollutants↗
PubMed2000

Cancer mortality and exposure to chemical carcinogens in the work place: an ecological study in the Valencian Community, Spain (1981-1995).

To evaluate the geographical distribution of the mortality from malignant tumours in relationship with exposure to chemical carcinogens in the work place, and to asses the possible association between these questions and the percentage of population employed in certain high-risk sectors, an ecological study in the Valencian Community (VC), Spain was carried out. Age-adjusted mortality rates for the total number of malignant tumours, lung, bladder, lymphomas and leukaemia during the periods 1981-1985 and 1991-1995 were calculated for the 34 geographical areas. The percentage of population in each area working in sectors in which they may be exposed to chemical carcinogens was obtained. The relationship between mortality on-the-job exposure was studied using linear regression methods. Large differences in cancer mortality were seen. In men, the geographical pattern was very stable and reveals a significant association with the distribution of certain high-risk jobs. Statistically significant positive correlations (p < 0.001) were found between cancer mortality and the percentage of the population working in metal, wood and furniture sectors. In contrast, a negative and statistically significant (p < 0.001) correlation was observed between cancer mortality and the percentage of the population working in agriculture. In conclusion, although the variability in cancer mortality in men was significantly associated with some occupational sectors in the VC, caution is needed when drawing conclusions about causation from ecological studies.

Agriculture↗
PubMed1998

Determination of L-ascorbic acid and total ascorbic acid in vascular and nonvascular plants by capillary zone electrophoresis.

A capillary zone electrophoresis (CZE) procedure for the determination of l-ascorbic acid (AA) and total ascorbic acid (TAA, as the sum of AA and dehydroascorbic acid) in vascular plants, lichens, bryophytes, and liverworts is described. The samples were frozen in liquid nitrogen and extracted with 2% metaphosphoric acid. To determine AA, an aliquot was directly injected in a fused-silica capillary. The determination of TAA was performed upon its reduction with dl-homocysteine at pH 7. The background electrolyte contained 60 mM sodium chloride, 60 mM sodium dihydrogen phosphate, 1 x 10(-4)% hexadimetrine bromide, and NaOH up to pH 7. The procedure was rapid and highly reproducible; the limit of detection was 0.2 microg ml-1, which corresponded to 0.4 mg/100 g of sample. The method was validated by comparison with an enzymatic assay. While the enzymatic assay failed to quantify AA in some plants owing to strong background UV absorption, CZE was successful in all the extracts assayed.

Ascorbic Acid↗
PubMed1997

Massive arterial bleeding from a single rectal vessel.

We report a case of massive rectal haemorrhage arising from a single ectatic arterial vessel above the haemorrhoidal cushion in normal rectal mucosa. Use of an anal retractor enable identification of the bleeding vessel and avoided a major laparatomy.

Aged↗
PubMed1991

1-Naphthyl Acetate-Dependent Medium Acidification by Zea mays L. Coleoptile Segments.

Zea mays L. cv INRA 5a coleoptile segments ecidify the incubation medium on the addition of 1-naphthyl acetate (1-NA). The buffering capacity of the bathing solution increases during 1-NA stimulated medium acidification. The solution bathing the 1-NA treated coleoptile segment was analyzed by high performance liquid chromatography. A considerable amount of acetic acid was detected in the bathing solution used to measure 1-NA-dependent medium acidification. For the first time, the data demonstrate directly the release of acetic acid from 1-NA. The extent of medium acidification was proportional to 1-NA concentration. Simultaneous measurement of medium acidification and acetate content upon addition of 1-NA showed that both processes were temporally correlated. The stoichiometry of proton equivalents to acetate ion was 0.966. Addition of 50 micromolar N,N'-dicyclohexylcarbodiimide had little effect on 1-NA-dependent medium acidification. The results indicate that 1-NA is hydrolyzed in the extracellular space of coleoptile cells.

Journal Article↗