192 research outputs found
Changes in oxalate composition and other nutritive traits in root tubers and shoots of sweet potato (Ipomoea batatasL. [Lam.]) under water stress
BACKGROUND: The presence of insoluble calcium oxalate druse crystals (CaOx) in sweet potato (Ipomoea batatas) can negatively
affect its nutritional quality. Photosynthesis, starch, and protein composition are linked with oxalate synthesis and tuber quality
under water scarcity. Our main objective was the oxalate quantitation of sweet potato tubers and shoots and also to assess
how drought changes their nutritional value. Eight sweet potato accessions from Madeira, the Canaries and Guinea-Bissau were
analyzed for their response to drought stress. Tubers and shoots were analyzed for total (T-Ox), soluble (S-Ox) and insoluble
(CaOx) oxalates, protein, chlorophyll content index (CCI), soluble starch, starch swelling power, and starch solubility in water.
RESULTS: The S-Ox and CaOx content was higher in shoots. Six accessions were above maximum CaOx levels for raw consumption. Accessions with more favorable responses to drought had decreased CaOx with S-Ox increase content for osmoregulation.
They also presented slightly decreased CCI and protein contents. These accessions also had an increased shoot starch content,
for further tuber storage starch hydrolysis, and maintained the quality and functional properties of the tuber starch grain. Those
with a less favorable response to drought had a higher T-Ox and CaOx content in both organs, hindering water absorption. They
also had decreased protein and CCI, with a slight increase in tuber starch hydrolysis.
CONCLUSION: Oxalate content was significantly related to carbohydrate metabolism, CCI, and protein synthesis. This study
significantly contributed to the screening of the sweet potato stress response to drought, to adapt this crop to climatic change
through breeding programs.info:eu-repo/semantics/publishedVersio
Stable isotope natural abundances (δ13C and δ15N) and carbon-water relations as drought stress mechanism response of taro (Colocasia esculenta L. Schott)
Taro (Colocasia esculenta L. Schott) is an important staple food crop in tropical and developing countries, having high water requirements. The purpose of this study was to evaluate the feasibility of using carbon and nitrogen isotopic composition (δ13C and δ15N) as a physiological indicator of taro response to drought, and elucidation of the relationship between the water use efficiency (WUE) under drought conditions and carbon isotope discrimination (Δ13C). As an alternative to WUE determination, obtained by measuring plant growth and water loss during an entire vegetative cycle, we have used Δ13C to determine the tolerance of C3 taro plants to drought. Seven taro accessions from Madeira, Canary Islands and the Secretariat of the Pacific Community (Fiji) collections were grown under greenhouse conditions and subjected to different watering regimes during a one-year cycle. Total plant biomass (TPB), WUE and δ15N were determined at the whole-plant level (WP). Corms and shoots were evaluated separately for nitrogen content (N), δ13C, Δ13C and δ15N. WUE showed positive correlation with TPB (r = 0.4) and negative with Δ13C (r = -0.3); Corm δ15N showed positive correlations with WP δ15N (r = 0.6) and corm N (r = 0.3). Accordingly, the taro plants with enhanced WUE exhibited low Δ13C and δ15N values as a physiological response to drought stress. The approach used in the present study has developed new tools that could be used in further research on taro response to environmental stresses.This work was supported by the Programa Operacional da Região
Autónoma da Madeira – PO Madeira 14–20 [grant number M1420-01-
0145-FEDER-000011, CASBio] and the Agência Regional para o
Desenvolvimento da Investigação Tecnologia e Inovação – ARDITI [grant
number M1420-09-5369-FSE-000001].info:eu-repo/semantics/publishedVersio
Morphological evaluation of common bean diversity on the Island of Madeira
The variability of fifty populations of
common bean (Phaseolus vulgaris L.), representing a
wide range of ecological conditions on the Island of
Madeira, was evaluated based on morphological and
reproductive traits. Individual data of 58 traits related
to earliness, plant and tassel structure and the shape of
the ear and grain were analysed using multivariate
analysis. The populations belonging to two major
common varieties were clustered into fifteen groups by
their degree of dissimilarity, based on discriminant
analysis. The dissimilarity of these groups was con-
firmed by one way ANOVA. The racial rank of these
groups was proposed and a brief description of the
common bean landraces was presented. This work
represents the first morphological characterization and
analysis of diversity of bean germplasm from the
Archipelago of Madeira, where the traditional agricultural
practices are still keeping this Portuguese region
free from improved bean varieties. The description of
the Madeiran bean landraces allows the preservation of the existing bean biodiversity and could be used for
their registration as conservation landraces, or for
conservation and breeding purposes worldwide.The European Union has sponsored this
work through the INTERREG IIIB programme, through the project Germobanco Agrı´cola da Macarone´sia, 05/MAC/4.1/
C15. The Authors are grateful to the Madeiran farmers who
assisted with collection of bean samples.info:eu-repo/semantics/publishedVersio
Integrated approach of hydrogeomorphology and GIS mapping to the evaluation of ground water resources: an example from the hydromineral system of Caldas da Cavaca, NW Portugal.
Understanding the role of geomorphology is essential to accurately assess hydrogeological systems and groundwater resources. Hard-rock watersheds provide a source of valuable water resources. They commonly exhibit complex geological bedrock and morphological features as well as distinctive gradients in rainfall and temperature. A comprehensive evaluation and integrated gro undwater resources study has been carried out for Caldas da Cavaca hydromineral system in NW Portugal, using hydrogeomorphology and GIS mapping techniques. Thematic maps were prepared from satellite imagery, topographical and geological mapping and other hydrogeological field data. These maps were converted to GIS format a nd then integrated using GIS software with the purpose of elaborating a hydrogeomorphological map intended to delineate the infiltration potential areas for the study region. Finally, this study highlights the importance of hydrogeomorphological cartography and groundwater GIS mapping as useful tools to support hydrogeological surveys, as well as for decision-making in the scope of management plans respecting to land and water resources and groundwater sustainability
Evidences of organic acids exudation in aluminium stress responses of two Madeiran wheat (Triticum aestivum L.) landraces
Two wheat (Triticum aestivum L.)
Madeiran landraces were subjected to 100 μM and
200 μM of aluminium (Al) in hydroponic culture,
assessing the organic acid exudation role in plant’s
responses to this metal. Samples of initial landrace
populations (F0), F3 and haplodiploid lines (DH) were
evaluated using standard tests: eriochrome cyanine R
staining, root elongation and callose accumulation in
roots. Root exudates were obtained to determine if
the accumulation of malic and citric acids in hydroponic medium was a response to Al exposure.
Additionally, the presence of ALMT1 gene was
determined using five microsatellite markers. Standard tests confirmed that ISOP 76 was Al tolerant and
ISOP 239, Al susceptible. ISOP 76, in the presence of
100 μM Al, exuded substantially more malic acid
(12.87 to 43.33 mg/L), than ISOP 239 (3.65 to
7.72 mg/L). The levels of both organic acid exudation
were substantially lower in ISOP 239 than in the
ISOP 76. In the presence of 200 μM Al, ISOP 76 F0
shows a higher root elongation ratio (better tolerates
Al), but the DH line was the one that exuded higher
content of malic acid. Different gene alleles and
promoters were detected in both landraces. Molecular
differences could explain the observed dissimilarity
in organic acid exudation response to Al stress.The authors are grateful to the Madeiran
farmers providing samples of wheat landraces, and to all staff
of CGR ISOPlexis Gene bank and of the Department of
Biological Sciences of Alberta University for support and
access to laboratory facilities. This work got the funding
support from the programs INTERREG III-B, contract
05/MAC/4.1/C15 and Madeira PO 14-20, contract CASBio,
refª. M1420-01-0145-FEDER-000011.info:eu-repo/semantics/publishedVersio
Flavonoids in phylloclades discriminate endemic Semele androgyna chemotypes from Madeira
Thirty-five randomly-collected Semele androgyna Kunth
samples were screened by RP-HPLC for their phenolic
composition. Fraction analysis allowed the detection of
17 different compounds. According to their retention
times and UV spectra obtained by diode array analysis,
these phenolics represent three classes: phenolic
acids, flavones and flavonols. Co-chromatography with
specific standards enabled identification of quercetin,
rutin and quercitrin in Semele tissues for the first time.
Polymorphism based on phenolic composition was
evaluated using multivariate analysis and showed four
distinct S. androgyna clusters. This polymorphism was
not associated with morphological diversity or different
in ambient light intensities. Biochemical differentiation
is thus present in this species. The application of
multivariate analysis techniques to RP-HPLC data has
allowed the classification of samples into two groups,
previously proposed on the basis of morphological and
cytotaxonomical information. Therefore, the use of
phenolics as chemotaxonomic markers in Semele is
highly recommended because of its diagnostic value,
even at a subspecies level. Discriminant canonical
analysis and Mahalanobis distances confirmed these
clusters as recognisable chemosystematic units.
However, these units do not support the separation of S.
pterygophora.The Portuguese Foundation for Science and
Technology (FCT) funded this work through the Centre of Macaronesian
Studies (CEM). The authors are grateful to the Madeiran Centre of
Science and Technology (CITMA), the Berardo Foundation and
European Social Funding for financial assistance given during execution
of this work. The assistance rendered by Mr Rogério Correia during field
collection is gratefully acknowledged.info:eu-repo/semantics/publishedVersio
Screening for Drought Tolerance in Thirty Three Taro Cultivars
Taro [Colocasia esculenta (L.) Schott] is a root crop which is an important staple food in many regions of the world, producing 10.5 million tonnes on 1.4 million hectares a year. The crop is cultivated in wet (rain fed) or irrigated conditions, requiring on average 2,500 mm water per year, and in many countries it is cultivated in flooded plots. It is estimated that taro production could decrease by 40% as a result of the increase in drought and other severe events. In this work, thirty three accessions, including local cultivars, selected and hybrid lines were submitted to long duration drought stress and screened for tolerance. Twelve physiological, morphological and agronomic traits were measured at harvest, and subject to multivariate analysis. Stress indices, Water Use Efficiency and Factorial Analysis were useful for discriminating accessions regarding drought tolerance and yield stability, and drought tolerant and susceptible cultivars were identified. Our results confirm that different taro cultivars have different drought avoidance and tolerance strategies to cope with water scarcity. Better yield performers minimised biomass and canopy loss, while tolerance was observed in cultivars that presented low potential yield, but efficiently transferred resources to enhance corm formation. Among the 33 accessions, two local cultivars showed high yield stability and could be considered as suitable parents for breeding programs, while two others are well adapted to drought, but with overall low yield potential
Dynamic Critical Behavior of an Extended Reptation Dynamics for Self-Avoiding Walks
We consider lattice self-avoiding walks and discuss the dynamic critical
behavior of two dynamics that use local and bilocal moves and generalize the
usual reptation dynamics. We determine the integrated and exponential
autocorrelation times for several observables, perform a dynamic finite-size
scaling study of the autocorrelation functions, and compute the associated
dynamic critical exponents . For the variables that describe the size of the
walks, in the absence of interactions we find in two dimensions
and in three dimensions. At the -point in two dimensions
we have .Comment: laTeX2e, 32 pages, 11 eps figure
Delay times and reflection in chaotic cavities with absorption
Absorption yields an additional exponential decay in open quantum systems
which can be described by shifting the (scattering) energy E along the
imaginary axis, E+i\hbar/2\tau_{a}. Using the random matrix approach, we
calculate analytically the distribution of proper delay times (eigenvalues of
the time-delay matrix) in chaotic systems with broken time-reversal symmetry
that is valid for an arbitrary number of generally nonequivalent channels and
an arbitrary absorption rate 1/\tau_{a}. The relation between the average delay
time and the ``norm-leakage'' decay function is found. Fluctuations above the
average at large values of delay times are strongly suppressed by absorption.
The relation of the time-delay matrix to the reflection matrix S^{\dagger}S is
established at arbitrary absorption that gives us the distribution of
reflection eigenvalues. The particular case of single-channel scattering is
explicitly considered in detail.Comment: 5 pages, 3 figures; final version to appear in PRE (relation to
reflection extended, new material with Fig.3 added, experiment
cond-mat/0305090 discussed
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