Henrique Pessoa dos Santos

Mobilisation of storage cell wall polysaccharides in seeds.

Plants store carbohydrate polymers in a number of forms. Starch is the principal form, followed by fructans and cell wall storage polysaccharides (CWSP). The latter are present mainly in seeds and consist of magnifications of one of the polysaccharides present in one of the cell wall matrices. CWSPs are classified as mannans, xyloglucans and galactans, the first being subdivided into pure mannans, galactomannans and glucomannans. The present review updates the principal discoveries concerning occurrence, structure, metabolism and eco-physiological significance of the seed storage cell wall polysaccharides with emphasis on their importance for plant metabolism and adaptation to their respective environments during evolution. The properties of CWSPs as storage polysaccharides are compared with starch and fructans and the current knowledge on the catabolism (including control) of mannan/galactomannan, xyloglucan, and galactan is reviewed. On the basis of these data, the idea that the CWSPs are multifunctional molecules is proposed and this feature is used as evidence for the hypothesis that, during evolution, the CWSPs were involved in cycles of transference of functions which led them to become storage polysaccharides, yet preserving some of their previous primary cell wall functions.

Alterações micrometeorológicas em vinhedos pelo uso de coberturas de plástico

The objective of this work was to evaluate the effects of plastic covering on the microclimate of vineyards (Vitis vinifera L., cultivar Moscato Giallo), in Serra Gaucha region in Rio Grande do Sul State, Brazil. The experiment was performed in Flores da Cunha, RS, during the 2005/2006 growing season. It comprised uncovered and covered rows of vines, using a 160 µm thick plastic film. Photossinthetically active radiation (PAR), air temperature and humidity, and wind velocity were monitored: over the plastic covering; between the film and the canopy; over the uncovered canopy; and close to grapes of both treatments. Reference evapotranspiration was estimated for both treatments. From the incoming PAR, 67.5% reached the covered canopy, 16% reached the covered grapes, and 36% reached the uncovered grapes. The plastic covering increased by 3.4oC the maximum air temperatures close to plants. Diurnal air relative humidity was reduced, while water vapor pressure and vapor pressure deficit were increased because of the plastic covering, which also reduced in 88% the wind velocity in comparison to open air. The reference evapotranspiration on the covered canopy was 35% lower than in open air. Although increasing diurnal air temperatures, the plastic covering may reduce the evaporative demand on vineyards, by reducing the incoming solar radiation and the wind velocity.

The Control of Storage Xyloglucan Mobilization in Cotyledons of Hymenaea courbaril

Hymenaea courbaril is a leguminous tree species from the neotropical rain forests. Its cotyledons are largely enriched with a storage cell wall polysaccharide (xyloglucan). Studies of cell wall storage polymers have been focused mostly on the mechanisms of their disassembly, whereas the control of their mobilization and the relationship between their metabolism and seedling development is not well understood. Here, we show that xyloglucan mobilization is strictly controlled by the development of first leaves of the seedling, with the start of its degradation occurring after the beginning of eophyll (first leaves) expansion. During the period of storage mobilization, an increase in the levels of xyloglucan hydrolases, starch, and free sugars were observed in the cotyledons. Xyloglucan mobilization was inhibited by shoot excision, darkness, and by treatment with the auxin-transport inhibitor N-1-naphthylphthalamic acid. Analyses of endogenous indole-3-acetic acid in the cotyledons revealed that its increase in concentration is followed by the rise in xyloglucan hydrolase activities, indicating that auxin is directly related to xyloglucan mobilization. Cotyledons detached during xyloglucan mobilization and treated with 2,4-dichlorophenoxyacetic acid showed a similar mobilization rate as in attached cotyledons. This hormonal control is probably essential for the ecophysiological performance of this species in their natural environment since it is the main factor responsible for promoting synchronism between shoot growth and reserve degradation. This is likely to increase the efficiency of carbon reserves utilization by the growing seedling in the understorey light conditions of the rain forest.

Transcription profiling of the chilling requirement for bud break in apples: a putative role for FLC-like genes

Apple production depends on the fulfilment of a chilling requirement for bud dormancy release. Insufficient winter chilling results in irregular and suboptimal bud break in the spring, with negative impacts on apple yield. Trees from apple cultivars with contrasting chilling requirements for bud break were used to investigate the expression of the entire set of apple genes in response to chilling accumulation in the field and controlled conditions. Total RNA was analysed on the AryANE v.1.0 oligonucleotide microarray chip representing 57,000 apple genes. The data were tested for functional enrichment, and differential expression was confirmed by real-time PCR. The largest number of differentially expressed genes was found in samples treated with cold temperatures. Cold exposure mostly repressed expression of transcripts related to photosynthesis, and long-term cold exposure repressed flavonoid biosynthesis genes. Among the differentially expressed selected candidates, we identified genes whose annotations were related to the circadian clock, hormonal signalling, regulation of growth, and flower development. Two genes, annotated as FLOWERING LOCUS C-like and MADS AFFECTING FLOWERING, showed strong differential expression in several comparisons. One of these two genes was upregulated in most comparisons involving dormancy release, and this genes chromosomal position co-localized with the confidence interval of a major quantitative trait locus for the timing of bud break. These results indicate that photosynthesis and auxin transport are major regulatory nodes of apple dormancy and unveil strong candidates for the control of bud dormancy.

Microclima de vinhedos sob cultivo protegido

Microclimate alterations promoted by plastic covering over vineyards interfere in the plant physiology and fungal diseases incidence on grapevines. The aim of this research was to evaluate the influence of the plastic covering on the microclimate of vineyards, in particular on the quality of the incoming solar radiation. The experiment was carried out in 2005/06 and 2006/07 seasons in Flores da Cunha-RS, in a vineyard of Moscato Giallo cultivar shaped in Y, with impermeable plastic (160μm) over 12 rows of 35m length and five rows without covering (control). In both treatments the air temperature and humidity, incoming photosynthetically radiation and wind speed were measured at the level of the canopy and clusters. Continuing measurements were taken through sensors and automatic acquisition systems (datalogger). Influences of the covering on quality of the incoming solar radiation, from 300 to 750nm, were evaluated through a spectroradiometer. The impermeable plastic covering above the plant rows increased the air temperature and decreased the photosynthetically radiation and wind speed. The covering interfered on the quality of the incoming solar radiation, by reducing mainly the irradiance in the ultraviolet band and reducing also the ratio between the irradiance in the red and far-red bands.

MATURAÇÃO DE UVAS MOSCATO GIALLO SOB CULTIVO PROTEGIDO 1

Plastic overhead cover (POC) is a recent viticulture practice in grapevine cultivation that maybe could changes the plant microclimate and the ripening profi le. The purpose of this work was to evaluate the POC infl uence on ripening evolution of grapes Moscato Giallo. The experiment was carried out in 2005/06 and 2006/07 seasons, in a vineyard covered with an impermeable plastic cloth (2.65 m x 160 m), being left fi ve rows without covering (control). Berries were collected (three replicates of 100 units for treatment) weekly in each area (POC and control). These berries were evaluated regarding to weight, diameter and must composition (pH, o Brix, titratable acidity, malic and tartaric content). At harvest it was characterized also the musts of covered and uncovered grapes ( o Brix, reduced sugar, relative density, total acidity, tartaric and malic content, pH and must yield). POC modifi es the microclimate in canopy and clusters infl uencing the grape ripening. Due to reduction of photosynthetically active radiation, that slows the sugar accumulation, the POC grapevines should be harvest after compared to conventional grapes. Index terms: plasticulture, microclimate, ripening, management.

Potencial produtivo de videiras cultivadas sob cobertura de plástico

The objective of this work was to evaluate the effect of plastic cover on the yield components of grapevine (Vitis vinifera L.) cultivar Moscato Giallo. The experiment was carried out in 2005/2006 and 2006/2007 crop seasons, in Flores da Cunha, RS, Brazil, in two vineyard areas, one covered with an impermeable plastic film and other without covering (control). The microclimate was evaluated in terms of air temperature, air relative humidity, photosynthetically active radiation and wind speed above canopy and close to clusters. The yield components were evaluated in a completely randomized design, in ten plants randomly selected in each area. Measures were made for production per plant, yield per hectare, clusters per vine, clusters per square meter, twigs per square meter, weight and length of clusters, weight of rachis, number of berries per cluster, diameter of berries, and skim/pulp ratio. Plastic cover promotes yield increases, does not affect pulp/skin ratio, and promotes production stability, independently of climate conditions in each season.

Caracterização físico-química do mosto e do vinho Moscato Giallo em videiras cultivadas sob cobertura de plástico

The objective of this work was to evaluate the plastic overhead cover (POC) effect on must and wine composition of the cultivar Moscato Giallo. In 2006 vintage, it was performed a completely randomly designed experiment, in a vineyard covered with an impermeable plastic cloth, and without covering as control. From each vineyard, three microvinification (20 L) were elaborated. Physico-chemical analysis were performed for: musts - o Brix, reducer sugar contents, density, total acidity, tartaric acid, malic acid and pH; and wines - density, alcohol degree, acidity, volatile acidity, pH, dry extract, reducer sugar contents, ashes, I 420, volatile compounds and minerals. The must of the covered vineyard presented higher yield, but lower sugar content, due to delay on ripening. As consequence, the POC wines showed lower alcohol degree, but with the benefit of a lower ethyl- acetate and volatile acidity levels. The POC microclimate also caused a decrease of some minerals (mainly P and K) in the wines. POC improved the enological quality, however, this demands delay in the harvest date to achieve the adequate physiological and technological maturation of grapes.

Anatomy, chlorophyll content and photosynthetic potential in grapevine leaves under plastic cover

The present study evaluated the anatomy, chlorophyll content and photosynthetic potential of grapevine leaves grown under plastic cover. The experiment was carried out in vineyards of Moscato Giallo cultivar covered and uncovered with plastic. A block design with 10 selected plants was used for each area (covered and uncovered). Twelve leaves (six of them fully exposed to solar radiation and six grown under shaded conditions) were collected from each area and were fixed and analyzed microscopically (thickness of the adaxial and abaxial epidermis and of the palisade and spongy parenchymas). Chlorophyll content and photosynthetic potential were determined in the vineyard at veraison and after harvest. Plastic covering increased the thickness of the palisade parenchyma in exposed and shaded leaves due to solar radiation restriction. However, the leaves from the covered vineyard did not have the same response to the restriction of solar radiation, as observed in the uncovered vineyard. The thickness of the adaxial and abaxial epidermis and of the spongy parenchyma did not vary due to solar radiation restriction. Chlorophyll content increased in the leaves of covered plants. The photosynthetic potential of the vines is not affected by solar radiation restriction imposed by plastic cover due to anatomical modification in leaves.

Cobertura plástica sobre o vinhedo e suas influências nas características físico-químicas do mosto e do vinho

ABSTRACT – The aim of this study was to evaluate plastic overhead covering (POC) influence on must and wine of Moscato Giallo cultivar. In two harvests the 2006 and 2007 vintages an experiment was carry out in a completely randomized design. It was performed in a vineyard covered with an impermeable plastic cloth and without covering as control. From each vineyard, three microvinification (20 L) were elaborated. Physico-chemical analysis of musts ( o Brix, reduce sugar content, density, total acidity, tartaric acid, malic acid e pH) and wines (density, alcohol degree, acidity, volatile acidity, pH, dry extract, reduce sugar content, ashes, 420 index, volatile compounds and minerals) were analyzed. According to results POC (raffia type with 160 μm) grapes showed more yield must. However due to delay maturation showed lower sugar concentration. Wine produced with POC grapes had lower alcohol graduation. Another hand, the better sanity of grapes resulted in lower tenors of ethyl acetate and volatile acidity. POC system demands delay in harvest to achieve the same sugar concentration and alcohol graduation compared to grapes from open sky. Index terms: Vitis vinifera, plasticulture, microclimate, enological quality.