45 research outputs found
Mitochondrial bioenergetics is affected by the herbicide paraquat
AbstractThe potential toxicity of the herbicide paraquat (1,1-dimethyl-4,4′-bipyridylium dichloride) was tested in bioenergetic functions of isolated rat liver mitochondria. Paraquat increases the rate of State 4 respiration, doubling at 10 mM, indicating uncoupling effects. Additionally, State 3 respiration is depressed by about 15%, at 10 mM paraquat, whereas uncoupled respiration in the presence of CCCP is depressed by about 30%. Furthermore, paraquat partially inhibits the ATPase activity through a direct effect on this enzyme complex. However, at high concentrations (5–10 mM), the ATPase activity is stimulated, probably as consequence of the described uncoupling effect. Depression of respiratory activity is mediated through partial inhibitions of mitochondrial complexes III and IV. Paraquat depresses Δψ as a function of herbicide concentration. In addition, the depolarization induced by ADP is decreased and repolarization is biphasic suggesting a double effect. Repolarization resumes at a level consistently higher than the initial level before ADP addition, for paraquat concentrations up to 10 mM. This particular effect is clear at 1 mM paraquat and tends to fade out with increasing concentrations of the herbicide
Changes in carbon stocks in Eucalyptus globulus Labill. plantations induced by different water and nutrient availability
Changes in the carbon stocks under different soil water and nutrient conditions were studied in Eucalyptus globulus Labill.
stands in a field experiment, at O ´ bidos (central Portugal). The treatments were irrigation plus a complete fertiliser solution to
simulate ‘near optimal’ nutrition (IF), irrigation only (I), and fertilisers added to rain-fed plots (F). The control (C) received
neither water nor fertilisers (except a small amount at planting). The production of biomass (aboveground), the litterfall and the
soil chemical composition were evaluated regularly during the experiment. Root biomass was estimated at the end of the
experiment. Carbon in biomass, litterfall and soil, increased significantly when water and/or nutrients were supplied, in
comparison to the control. The amount of carbon accumulated in the system, 6 years after planting, was 8.22, 10.22, 11.23 and
13.76 kg C m 2 in the control, F, I and IF treatments, respectively. The increase of carbon in the system during the same period
was 5.86, 7.86, 8.87 and 11.40 kg C m 2 in the control, F, I and IF treatments, respectively. This rise in carbon resulted from the
accumulation of long-lived woody biomass, which represented between 77.7 (in IF) and 82.9% (in the control) of the total rise in
carbon. Although water was the main limiting factor for biomass accumulation, the allocation of carbon to the soil was mainly
related to nutrient supply, irrespective of water availability. The amount of carbon stored belowground, i.e. soil and forest floor,
plus stumps and roots, reached 4.2, 4.7, 4.8 and 6.3 kg C m 2 in the control, F, I and IF treatments, respectively. The increase in
C in the mineral soil regarding the initial state was, in the same order as above, 0.21, 0.75, 0.58 and 1.21 kg C m 2. These values
were 3.6, 9.6, 6.6 and 10.6% of the C accumulated in the whole system, during the experimental period
Studies on the association of the Quercus suber decline disease with Phytophthora cinnamomi in Portugal
En Portugal, la enfermedad de la “seca” se ha
descrito en los Quercus de hoja perenne (Quercus
suber L. and Q.ilex subsp. rotundifolia Lam.) desde
el final del siglo XIX. La mortalidad de estas
especies afecta, particularmente las regiones centrales
y meridionales del país, siendo uno de los problemas
forestales más graves. Phytophthora cinnamomi
Rands es el principal patógeno responsable de la
mortalidad de alcornoques y encinas en Portugal. Se
han desarrollado varios estudios teniendo como
objetivo una mejor comprensión del efecto de la
acción de P. cinnamomi en el decaimiento de los
Quercus.
El actual trabajo describe resultados preliminares
de algunos de estos estudios.___________________________________In Portugal, the decline disease has been described
in evergreen oaks (Quercus suber L. and Q.ilex
subsp. rotundifolia Lam.) since the end of the 19th
century. The mortality of these species affects,
particularly the central and southern regions of the
country, being one of the most severe forest
problems. Phytophthora cinnamomi Rands is the
main pathogen responsible for the cork and holm
oak mortality in Portugal. Several studies have
been developed aiming at a better understanding of
the effect of the P. cinnamomi action on the cork
oak trees decline.
The present work describes preliminary results of
some of these studies
A moenda da azeitona e as características físico-químicas dos azeites virgens
Comunicação apresentada no III Simpósio Nacional de Olivicultura que decorreu em Castelo Branco na Escola Superior Agrária do Instituto Politécnico de Castelo Branco, de 29 a 31 de Outubro de 2003.No presente trabalho estudou-se a influência do tipo de moenda da azeitona nas
características do azeite virgem, comparando os azeites obtidos extraídos por moinho de
pedras e por moinho metálico de martelos (com grelhas 5 e 7 mm de diâmetro). A
azeitona foi processada numa linha Rapanelli . A qualidade dos azeites foi avaliada por
determinação de: acidez, índice de peróxido, absorvâncias no UV, composição em
ácidos gordos, estabilidade oxidativa, K225, pigmentos clorofilinos, cor (L*a*b*) e
polifenóis totais. Em geral, a moenda não influencia os parâmetros de qualidade dos
azeites, dependendo mais das cultivares constituintes dos lotes. Os resultados mostram
que quando se utilizam moinhos de martelos se obtêm azeites virgens com um teor
superior de pigmentos clorofilinos
Influence of soil and organic residue management on biomass and biodiversity of understory vegetation in a Eucalyptus globulus Labill. plantation
The objective of this study was to assess the effect of different options of soil preparation and management of harvesting debris on
biodiversity and biomass of understory vegetation in plantations of Eucalyptus globulus of Central Portugal. The experiment
consisted of six treatments in a replanted area and four treatments in a coppice area with five replicates, following a randomised
block design. Surveys of vegetation were performed for 6 years. The proportion of soil cover by plant specieswas estimated and the
Shannon–Wiener diversity and equitability indexes determined for each treatment and year. After the 2nd year, the understory
vegetation was randomly sampled for above-ground biomass determination.Within the planted area, the removal of slash without
soil preparation induced the highest number of species during the experimental period. A similar trend was observed in the coppice
area, but less regularly. Significant differences in the proportion of soil cover only occurred within the planted area in the first year,
when slash removal without soil preparation induced the highest understory cover. Species diversity was not clearly affected by
treatments: significant differences only occurred occasionally and were apparently related to differences in the number of species.
Therefore, differences in the equitability index between treatments never were significant. Removal of slash without soil
disturbance and broadcast of slash over the soil usually shared the highest biodiversity. Differences between treatments in the
amount of understory biomass were never statistically significant during the experimental period. Tendency for a negative influence
of soil mobilisation on the amount of understory biomass was observed within the planted area, as well as a similar effect of the
treatments consisting of broadcast of slash over the soil surface in the coppice area. In parallel to tree development and canopy
closure biomass of that vegetation along the study period was reduced, especially in the planted area
Effects of harrowing and fertilisation on understory vegetation and timber production of Eucalyptus globulus Labill. plantation in central Portugal
Harrowing and fertilisation are common practices at middle rotation in Eucalyptus globulus Labill. plantations in Central Portugal. In order to
clarify the effects of such practices on understory vegetation and timber production, a field trial was installed in a 5-year-old first rotation
eucalyptus plantation, in a region with mixed oceanic and Mediterranean climatic influences. Four treatments that involved harrowing (H),
fertilisation (F), harrowing and fertilisation (HF), and control (C) were tested in the study. The treatments were replicated four times and arranged
in a simple completely randomised design. Vegetation surveys were performed by the quadrat method in the 3 years following treatments and by
the line interception method in the 7th and 8th years. Samples of understory biomass were collected, oven dried and weighed. In treatments with
harrowing, the understory vegetation consistently had lower number of species, less plant cover, species diversity, and biomass than the other
treatments. The mean total number of species only once reached 10 in H or HF plots, and was always greater than 12 in C and F plots in the first 3
years, but decreased in the 7th and 8th years. In the first 3 years, the understory biomass averaged 30–60 g m 2 in the F and C plots, and never
exceeded 13 g m 2 in treatments with harrowing, which corresponded with the proportion of soil coverage by understory vegetation (4–12% in H
and HF, and 38–62% in F and C plots). In the 7th and 8th years, differences in the understory biomass were less important, but the control plots
consistently had the largest understory biomass. The influence of treatments in timber production was not statistically significant at the end of
rotation
Species richness and biomass of understory vegetation in a Eucalyptus globulus Labill. coppice as affected by slash management
The aim of this study was to assess the effect of
different slash management practices on understory
biodiversity and biomass in Eucalyptus globulus coppices
in Central Portugal. The experiment consisted of four
treatments: (a) removal of slash (R), (b) broadcast over
the soil (S), (c) as in S but concentrating woody residues
between tree rows (W) and (d) incorporation of slash
into soil by harrowing (I). Understory vegetation was
surveyed during 1–6, 9, and 10 years, the proportion of
soil cover by plant species estimated, and diversity and
equitability indexes determined. Above ground understory
biomass was sampled in years 2–6, 9, and 10. The
highest number of species in most years occurred in plots
where slash was removed. Differences between treatments
in the proportion of plant soil cover were never
significant, whereas differences in diversity index were
only occasionally significant and apparently related to
the number of species. Thus, differences in the equitability
index were not significant. Understory biomass did
not decrease during the rotation period, and was usually
highest in R and I, and lowest in S, but not significantly
different. At the end of the rotation period, understory
biodiversity indices and biomass were apparently independent
of slash treatment