Luis Heras

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.

Plant analysis interpretation based on a new index: Deviation from Optimum Percentage (DOP)

Abstract The objective of the present work is to introduce a new index (DOP: Deviation from Optimum Percentage), as an alternative methodology for plant mineral analysis interpretation. The DOP index is calculated for each of the analyzed elements by applying the following general formula: DOP = [(C x 100yCref] ‐ 100, where C is the nutrient concentration in the sample to assess and Cref is the optimal nutrient concentration used as a reference value. The calculations used to obtain the DOP index can be easily implemented in a microcomputer. An optimum nutritional situation for any element is defined by a DOP index equal to zero. The DOP index permits to know the nutrient limitation order in a given sample, giving information similar to that obtained with the DRIS method. Furthermore, the DOP indexes indicate wether a element is in defect (negative indexes) or excess (positive indexes). For comparison, the DOP index has been applied, together with other traditional methods including the DRIS approach, to ...

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.

Relationships between yield and leaf nutrient contents in peach trees : early nutritional status diagnosis

Abstract The objective was to determine to what extent foliar nutrient contents in different stages of the vegetative cycle are related to yield. The study was conducted on 180 peach trees (Prunus persica, L. Batsch) in several orchards located in the Ebro Basin. Leaf sampling (at 60, 90, 120, 150, and 180 days after full bloom) and crop harvesting were carried out individually on each of the 180 trees. Leaf samples were analyzed for N, P, K, Ca and Mg. The relationships of mineral analysis data (nutrient contents and their ten binary ratios) with yield were explored by applying three different calculation procedures. First, we analyzed the degree of significance of the differences in nutrient contents and binary ratios between two blocks of trees, separated according to yield level. This degree of significance was highest for leaf samples taken 60 and 120 days after full bloom, although the differences in K content and N/P and Ca/Mg ratios were not significant 120 days after full bloom. Second, we analyz...

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).

Zeaxanthin Formation in Etiolated Leaves

Carotenoids and chlorophylls are essential compounds in the chloroplasts thylakoid membranes, but some carotenoids, in particular violaxanthin, are also located in the chloroplast envelope (1). Plastids from plants germinated and grown in the dark (etioplasts) have no photosynthetic activity and their lipidic structure is arranged in prolamelar bodies which are surrounded by membrane-containing carotenoids called prothylakoids (2). Although several authors report a structural role for carotenoids in chloroplast biogenesis (2), the two major functions are: pigments for light harvesting and photoprotection of enzymes, lipids and chlorophyll (3).