C. F. Alcaraz

Effects of foliar sprays containing calcium, magnesium and titanium on plum (Prunus domesticaL.) fruit quality

An experiment was performed in which Ti(4+)-ascorbate was sprayed onto plum trees in several combinations with other commercial compounds containing Ca2+ and Mg2+ to study the effects on the commercial quality of fruits, with special focus on improving their resistance against postharvest handling damage. All the treatments containing titanium increased the tree performance (branch elongation, flowering and fruit setting intensities) and fruit size. At harvest fruits from the Ti-treated trees showed improved resistance to compression and penetration, as well as a decrease in weight-loss during postharvest storage. A similar response was obtained for the external colour, though all the treatments seemed to delay somewhat the apparent ripening status. Nevertheless, the fruits from Ti-treated trees showed a better behaviour in the evolution of the colour parameters during storage than did the control fruits. Titanium application significantly increased the calcium, iron, copper and zinc concentrations in peel and flesh. This improvement in the calcium absorption is explained as a consequence of the beneficial effect of titanium on the absorption, translocation and assimilation processes.

Why titanium is a beneficial element for plants

Titanium (Ti) has been considered as an inert element for a long time. However, since the 1930s its promotive effect on plant metabolism has begun to be appreciated. After the first observation, experiments have been conducted which suggest the promotive effects on plant physiology leading us to propose it as beneficial element. This review presents results for establishing the basis for its beneficiality and examines its possible mechanism of action.

Effect of ascorbic acid addition to peppers on paprika quality

The use of ascorbic acid addition to foods to protect pigments from oxidation has been widely applied. Control or ascorbic acid-added paprika peppers were processed in a similar way as for paprika manufacture. During the process, lipoxygenase activity, total colour, red/yellow pigment ratio and ascorbic acid levels were measured. In general, an increase of total colour and red pigments was observed in ascorbic acid-treated samples. The lipoxygenase activity was depressed in ascorbic acid-treated fruits on the first day of processing. However, the activity was increased again, at second day, when the ascorbic acid was oxidised, showing a close relationship between enzyme activity and the antioxidant. After the process, ascorbic acid was also added to half of the paprika from control peppers and its quality and stability of the pigments against light or heat was compared to the paprika from ascorbic acid-added peppers. At the end of the treatment a better quality was observed in paprika obtained from the ascorbic acid-added peppers. ©1997 SCI

Influence of ferredoxin levels on nitrate reductase activity in iron deficient lemon leaves

Abstract The relationship between nitrate reductase activity and ferredoxin levels in lemon tree leaves was studied. The experiments were carried out on leaves from full‐nutrient sufficient trees as the reference, and on leaves from trees with several nutritional stresses, mainly iron chlorosis from trees growing under Fe‐stressed conditions. Iron deficiency reduced leaf ferredoxin concentration and consequently decreased nitrate reductase activity. Fe(II) infiltration treatments of intact leaves, as well as several incubation assays, permit to deduce the dependence of the enzymatic nitrate reduction of the leaf ferredoxin levels.

Effect of titanium leaf spray treatments on ascorbic acid levels of Capsicum annuum L. fruits

Abstract Ascorbic acid content is an important quality factor in Capsicum fruits for paprika obtention because its role as natural protector of the pigment stability due to its antioxidant properties. For increase its natural fruit levels, four Capsicum cultivare, growing in both greenhouse and field conditions were treated with titanium (Ti) via leaf spray. In all the cases, the fruits from Ti‐treated plants increased the ascorbic acid contents against its corresponding untreated controls. In the most of the cases, the highest ascorbic acid levels were obtained in fruits from plants that received two Ti‐treatments. Fruit response to Ti was more marked in the field experiments than for the greenhouse crops.

Nitrogen, Phosphorus, and Sulfur Nutrition in Broccoli Plants Grown Under Salinity

ABSTRACT Broccoli (Brassica oleracea L. var. ‘Italica’) is a recognized health-promoting vegetable and shows a moderate sensitivity to salinity. As very little is known about the effect of salt stress on broccoli plants, the objective was to evaluate nitrogen (N), phosphorous (P), and sulfur (S) nutrition in plants grown under saline conditions. For this objective, the contents of nitrate, phosphate, and sulfate, and total nitrogen, phosphorus, and sulfur, as well as related metabolic enzymes, were determined for plants grown with 0, 20, 40, 60, 80, or 100 mM sodium chloride (NaCl) for two weeks. Nitrate, phosphate, and sulfate concentration in leaves and roots showed a maximum at 40–60 mM NaCl. Up to these salt levels, broccoli plants showed a normal development, but over these salt levels, broccoli plants showed a decrease of nitrate reductase and an increase of the acid phosphatase. From 60 to 100 mM NaCl, the nutritional disorders indicated that the threshold of resistance was exceeded.

Effect of Ti (IV) on Fe activity in Capsicum annuum

Abstract Capsicum annuum , L. Plants (cv Bunejo) were treated with Ti 4+ ascorbate via soil, via leaves, and via soil plus via leaves. The Fe activity was measured through the catalase and peroxidase enzymes and the active fraction of Fe (Fe 2+ ) and Ti was determined in leaves, fruits, chloroplasts and chromoplasts. The Ti concentration increased in leaves and chloroplasts with Ti-treatments, but this did not bring about any variation in fruits and chromoplasts. The activities studied were enhanced by the application of Ti, and the Fe 2+ concentration was higher in the isolated organelles and in the leaves and the fruits of the Ti treated plants. These results support the previous hypothesis that Ti 3+ Ti 4+ , owing to its low redox potential, improves the Fe activity in plants, inducing a shift of the equilibrium Fe 2+ Fe 3+ towards Fe 2+ improving the Fe nutritional status of plants.

Effect of titanium (IV) application on some enzymatic activities in several developing stages of red pepper plants

Abstract The effect of two titanium (IV) compounds, titanium ascorbate and titanium chloride, on some enzymatic activities, such as catalase, peroxidase, lipoxygenase and nitrate reductase in seeds, embryos, and seedlings and adult plants of red pepper (Capsicum annuum L.), was studied. A stimulatory effect of titanium was observed for every iron‐depending enzyme studied at all developing stages as well as for nitrate reductase but only for whole plants. This occurs because Ti+3/Ti+4 catalizes the activity of iron and enhances iron‐dependent enzymes.

Iron deficiency in citrus limon: effects on photo‐chlorophyllase synthetic pigments and chlorophyllase activity

Abstract The photosynthetic pigment composition of chlorotic leaves of Citrus limon L. cv. Verna, grown in the field under iron deficiency conditions was determined. A Fe‐polyflavonoid was used as fertilizer to control iron chloro‐ sis. The photosynthetic pigment content and the chlorophyllase activity were determined at 20 day intervals during the deficiency recovery period and compared to untreated similar material. The corresponding differences among treated and untreated control material were analyzed. Iron application increased the levels of all pigments, but the extent of the increase depended on the pigment affected. The chlorophylls/carotenoids and s‐carotene/xantophylls ratios were increased as chlorosis diminished. A multivariance analysis was performed with the data obtained which revealed that chlorophyll a and s‐carotene had the highest correlation coefficient. The chlorophyllase activity did not show significant changes, but it was lower in the treated leaves than in the untreated control le...

Leaf spray with Ti(IV) ascorbate improves the iron uptake and iron activity in Capsicum annuum L. plants

Leaves of paprika pepper (Capsicum annuum L., cv Negral) plants sprayed with Ti(IV)-ascorbate showed an important increase of iron and titanium concentrations, as well as of the activity of peroxidase and catalase enzymatic systems. Leaf-Ti increase is similar for both greenhouse and field crop experiments, but increases in leaf Fe are more marked in plants growing under field conditions.