Jesús Val

New Insights into the Properties of Pubescent Surfaces: Peach Fruit as a Model

The surface of peach (Prunus persica ‘Calrico’) is covered by a dense indumentum, which may serve various protective purposes. With the aim of relating structure to function, the chemical composition, morphology, and hydrophobicity of the peach skin was assessed as a model for a pubescent plant surface. Distinct physicochemical features were observed for trichomes versus isolated cuticles. Peach cuticles were composed of 53% cutan, 27% waxes, 23% cutin, and 1% hydroxycinnamic acid derivatives (mainly ferulic and p-coumaric acids). Trichomes were covered by a thin cuticular layer containing 15% waxes and 19% cutin and were filled by polysaccharide material (63%) containing hydroxycinnamic acid derivatives and flavonoids. The surface free energy, polarity, and work of adhesion of intact and shaved peach surfaces were calculated from contact angle measurements of water, glycerol, and diiodomethane. The removal of the trichomes from the surface increased polarity from 3.8% (intact surface) to 23.6% and decreased the total surface free energy chiefly due to a decrease on its nonpolar component. The extraction of waxes and the removal of trichomes led to higher fruit dehydration rates. However, trichomes were found to have a higher water sorption capacity as compared with isolated cuticles. The results show that the peach surface is composed of two different materials that establish a polarity gradient: the trichome network, which has a higher surface free energy and a higher dispersive component, and the cuticle underneath, which has a lower surface free energy and higher surface polarity. The significance of the data concerning water-plant surface interactions is discussed within a physiological context.

Inhibition of vegetative growth in red apple cultivars using prohexadione-calcium

Summary Prohexadione-Ca (ProCa) has been evaluated as a growth inhibitor in the vigorous red apple cultivars ‘Fuji’ and ‘Royal Gala’. Greatest inhibition of shoot growth was obtained when ProCa was first sprayed at about 200 mg l–1 from full bloom (FB) up to 12 d after full bloom (DAFB). Shoot regrowth often occured later in the growing season, and a second application of ProCa was then needed to maintain growth inhibition. Inhibition of shoot growth was due mainly to a reduction in internode length. No effects on yield have been found, except for cv. ‘Royal Gala’, where an increase in crop-load and a decrease in fruit size were recorded. Fruit quality parameters were not affected; but, in cv. ‘Fuji’, the red colouration of fruit was promoted by ProCa, particularly when repeated sprays of the chemical (at 125 or 250 mg l–1) were made. Changes in hue, chroma and lightness were recorded on both the blushed and shaded sides of fruit. No effects on fruit colour were seen in ProCa-treated cv. ‘Royal Gala’ trees.

Effect of Pre-Harvest Calcium Sprays on Calcium Concentrations in the Skin and Flesh of Apples

ABSTRACT During 2004 and 2006, experiments were conducted that measured the absorption of calcium (Ca) by the fruit and assessed the effects of Ca sprays on the skin and flesh of apples. Frequent (1 spray/month for 2 or 4 months) Ca treatments increased the concentration of Ca in the skin, but not in the flesh of fruit, and several sprays were needed to promote a prolonged increase in the concentration of Ca in the skin. Calcium sprays did not influence the concentrations of magnesium (Mg) and potassium (K). Foliar analyses confirmed the absorption of topical Ca by the apple tree following the Ca sprays as the concentration of Ca in leaves increased.

A rapid wet digestion method for plant analysis

Analysis of nutrients in plant material requires previous digestion. Although a variety of digestion methods arc used, they are usually time-consuming procedures to digest and prepare the samples. Calcination methods, using classical muffles furnaces, allow the treatment of a high number of samples but the process requires at least 24–48 hours. Sulfuric acid based wet digestion methods, have generally the inconvenient of low Fe and Al recoveries (Bowman, 1989), and the analysis is restricted to ICP. In this work, total P, Ca, Mg, K, Fe, Mn, Zn, and Cu, in lucerne leaves (Medicago sativa L.) were determined. The solutions for analysis were prepared by an improved wet digestion method (7–8 min) based on the addition of hydrogen peroxide to the sample previously introduced in concentrated HNO3, followed by moderate heating (100 °C). Ca, Mg, Fe, Mn, Zn and Cu were determined by AAS and ICP, K, by AES, and P by colorimetry. Standard addition of iron in the leaf samples avoided the interference of HNO3 in AAS determination of Fe. The results are compared with the obtained by classical dry calcination (muffle) and other wet methods.

Visual Detection of Calcium by GBHA Staining in Bitter Pit-affected Apples

Bitter pit is a physiological disorder of apple fruits apparently caused by a localized calcium deficiency or imbalance in fruits associated with low levels of calcium in the flesh. A new, highly selective method using glyoxal bis(2-hydroxyanil, GBHA) was tested to reveal the presence of calcium within the fruit as a red stain. Water-soluble and insoluble calcium was analyzed by capillary electrophoresis and atomic absorption spectroscopy in pitted regions, adjacent sound areas and pulp from sound apples. Both methods, selective calcium staining and mineral analysis, showed that calcium accumulates in the pitted areas of apples affected by bitter pit. However, in mechanically inflicted wounds, the pulp of the apple was heavily stained but not the corresponding fingerprint, indicating a similar mechanism of insoluble calcium accumulation but a different distribution of soluble calcium compared to the pits.

Polypeptide pattern of apple tissues affected by calcium-related physiopathologies

Polypeptides from the apple pulp of Smoothee Golden Delicious and White Renete apples were resolved by 1-D denaturing sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). According to the electropherograms, there were lower concentrations of 88, 74, 70.6 and 47.5-42kDa proteins in bitter pit spots. Proteins weighing 30 and 26kDa were rare in sound pulp but frequently appeared in pits and adjacent tissue. Finally, a novel 18kDa protein was found in bitter pit spots in both varieties, and also in chemically induced corky lesions either by magnesium infiltration or ammonium oxalate cortical injections. The available data suggested that the novel protein might be an inhibitor of pectinmethylesterase, a small heat stress protein (smHSP) or a product of the Ypr-10 gene family identified with ‘Mal d 1’, the main allergen of apples. To elucidate the possible smHSP nature of the 18kDa, a set of apples were heated at 40°C for 20h, developing this protein in both the oxidised tissue and in the adjacent.

EFFECTS OF PACLOBUTRAZOL ON DRY WEIGHT AND MINERAL ELEMENT DISTRIBUTION AMONG FRUITS AND SHOOTS OF “CATHERINE” PEACH TREES

ABSTRACT Fruits and shoots of “Catherine” peach trees were analyzed to study the effects of the application of increasing rates of paclobutrazol (PP333) on the distribution of carbon and mineral elements among these organs, and mineral element concentration in leaves were determined to explain the changes observed. PP333 application did not result in differences in dry matter allocation to fruits, while it dramatically decreased the allocation to shoots. PP333 did not affect mineral element concentration in the different parts of the fruits, while increased concentrations of most elements were observed in terminal shoots, although the total amount was less in treated trees due to the reduction in shoot weight. Both in fruits and in shoots, an increase in the water content was observed. In leaves, the patterns of variation of mineral element concentration changed following the application of PP333, indicating greater exports of nitrogen (N), potassium (K), copper (Cu), and zinc (Zn), and greater accumulation of phosphorus (P), calcium (Ca), magnesium (Mg), and manganese (Mn).The results are discussed in terms of fruit–shoot competition relationships among these organs in peach trees.

Effects of paclobutrazol application and fruit load on microelement concentrations in peach leaves

‘Catherina’ peach trees (Prunus persica (L.) Bastch.) were soil-treated at full-bloom with paclobutrazol (Pbz) or left untreated and one month later fruit-thinned to leave four different cropping levels from full crop to none. Leaf samples were harvested on different dates from July 9 to 31 October and analysis of mineral elements made by AAS. The concentrations of Fe and Mn were always greater in leaves from Pbz treated trees than in the controls, while Zn and Cu concentrations remained unaffected. On all sampling dates, the concentration of Mn decreased linearly with increasing levels of cropping. No effects of the cropping level were observed in the concentrations of the other elements analysed.

Physiological effects of prohexadione-calcium in apple trees: effects on parameters related to photoproductivity

Summary Different prohexadione-Ca (RegalisTM, Pro-Ca) treatments were applied as foliar sprays to ‘Royal Gala’ and ‘Smoothee Golden Delicious’ apple trees to asses its effects on different physiological traits, under the growing condition of the Middle Ebro Valley (Spain). The application of Pro-Ca resulted in a decrease in leaf area, as well as fresh and dry leaf weights, and an increase in specific leaf weight. Greater light penetration through the canopy was recorded, indicative of a lower canopy density, resulting both from the inhibition of shoot growth and leaf extension growth. In addition, increases in leaf chlorophyll concentrations, and photosynthetic rates were found, which could account for the lack of effect of Pro-Ca on overall tree growth.

Effects of paclobutrazol and crop-load on mineral element concentration in different organs of "Catherine" peach trees

ABSTRACT The concentration of mineral elements in leaves and shoots of “Catherine” peach [Prunus persica (L.) Batsch.] trees with different crop-loads and treated with or without 2 g paclobutrazol (PP333) was analyzed. For most elements, the concentrations in the leaf varied linearly along the growing season, the concentrations of nitrogen (N), potassium (K), copper (Cu), and zinc (Zn) decreasing, those of calcium (Ca), magnesium (Mg), and manganese (Mn) increasing, while the concentration of iron (Fe) did not follow a clear pattern. PP333 increased concentration of calcium (Ca), Mg, Fe and Mn, and a decrease in K, while the pattern of change of concentration of N varied so that more N was exported from leaves of PP333 treated trees than from untreated trees. Crop-load also affected leaf N, Mg, and Mn concentration, but no effects were observed on K, Ca, and Fe concentration. In terminal shoots, PP333 increased the concentrations of all elements except K and Mg, and the level of cropping induced changes in the behavior of several elements: K, Mg, Fe, Mn, and Cu concentrations increased with crop-load in control trees, while in PP333-treated trees, they either decreased (Fe, Mn, and Cu) or remain unchanged (K and Mg), and phosphorus (P) concentration decreased both in PP333-treated or untreated trees. It is concluded that mineral element distribution among leaves and shoots is affected by PP333 and by the level of cropping.