E. Monge

Mineral composition of peach leaves affected by iron chlorosis

Abstract The effect of Fe chlorosis on the mineral composition of field grown peach tree leaves was studied in two different areas. No significant differences in total Fe content were found, whereas 2,2’ bipyridyl extractable Fe, K and the K/Ca ratio were significantly affected in both experiments. Phosphorus and the P/Fe ratio were significantly affected only in one experiment.

Extraction of iron from plant leaves by Fe (II) chelators

Abstract In the working conditions used for the extraction of iron with 1,10‐phenanthroline (o‐phe) or 2–2’ Bipyridyl (Bipy) from plant material, in vitro photoreduction of ferric ions occurs. Nevertheless, iron in plant extracts was found to be independent of the illumination conditions where the sample was maintained during the extraction. Ferric iron added to a plant extract was completely reduced in the darkness. These data seem to indicate that if extraction of ferric iron occurred, it would be reduced and measured as ferrous iron. Thus, the form of iron being extracted may be better called “active”; or “labile”; instead of ferrous iron. The use of o‐phe for the study of iron deficiency may give misleading conclusions, because of the simultaneous extraction of chlorophyll degradation products. The use of either Bipy or a purification step involving C18 cartridges is suggested. A high correlation between “active”; iron and chlorophyll in peach trees was found.

Changes in photosynthetic pigment composition in higher plants as affected by iron nutrition status

Abstract The effect of iron deficiency on the amount of photosynthetic pigments per unit leaf area was investigated into two fruit tree species, apricot and pear, grown in the field. Iron deficiency reduced the amount per area of all pigments, but the extent of the reduction depended on the particular pigment affected. The concentration of lutein per unit area was the least affected by iron deficiency. When compared to green leaves, iron deficient leaves which had lost about 85 percent of their chlorophyll a and other pigments, conserved about 30 percent of their lutein Tper area). The relationships between neoxanthin and chlorophyll a, and between β‐carotene and chlorophyll a were practically linear. The ratio between chlorophyll a and chlorophyll b increased only when the chlorophyll a content fell below 6–8 μg cm‐2, i.e. in fully chlorotic leaves.

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.

Photosynthetic Pigment Composition of Higher Plants Grown under Iron Stress

Iron deficiency causes a reduction in the thylakoid membrane system in higher plants (1). This reduction is acompannied by a decrease in all membrane components, including the light harvesting pigments chlorophylls and carotenoids, A decrease in the chlorophylls/carotenoids ratio has often been reported (2,3). The reason for this appears to be the relatively minor decrease in xanthophylls, by comparison to the decreases in chlorophylls and carotenes (2,4). The chlorophyll a/chlorophyll b ratio may also change under iron deficiency (5, see also 1), although no significant changes in the chlorophyll a/chlorophyll b ratio of green and chlorotic sugar beet leaves were found by Spiller and Terry (6).

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.