Juan Manuel Soto

Phenolic compounds and oxidative metabolism in green bean plants under nitrogen toxicity

The objective of the present work was to determine the effect of nitrogen toxicity on the metabolism of phenolic compounds and of oxidative stress in Phaseolus vulgaris L. cv. Strike. The nitrogen was applied to the nutrient solution as NH4NO3 at 5.4, 10.8, 16.2, 21.6 and 27 mM. The results indicate that the application of 27 mM N can be defined as toxic, as it drastically depressed growth of the green bean plants in our experiment. In addition, the abiotic stress from the application of this N dosage inhibited the enzymes polyphenol oxidase, peroxidase and cata-lase, and stimulated phenylalanine ammonia-lyase and superoxide dismutase activities. The result was foliar accumulation of phenolic compounds and hydrogen peroxide (H2O2). The accumulation of H2O2 also apparently caused a reduction in biomass production.

CHEMICAL TREATMENTS IN “GOLDEN DELICIOUS SPUR” FRUITS IN RELATION TO RUSSETING AND NUTRITIONAL STATUS

The impact of chemical products on mineral nutritional status and russeting in ‘Golden Delicious Spur’ was studied. In addition, we sought to define the nutrients responsible for russeting in order to avoid imbalances in their concentrations in the fruit. Lime-sulphur (lime and sulphur, T1), ProVide (gibberellic acid GA4+7, T2), calcium nitrate (8.5% N and 11.5% Ca, T3), Microthiol Special (micronized wettable sulphur at 80%, T4), Packhard (8% Ca, 6% carboxylic acid, 0.5%B, T5), and Dithane (ethylene-bis dithiocarbamate of manganese 62%, Mn 16% and Zn 2%, T6) were applied to apple trees at the onset of flowering, at petal drop, and at the onset of fruit development. The ProVide and Microthiol treatments reduced the damaged fruit area and the percentage of damaged fruits in comparison to control (trees without application, T0). The application of calcium nitrate and Dithane increased the percentage of damaged area in relation to control, whereas the use of Packhard increased the percentage of fruits with russeting. In conclusion, our results indicate that russeting is more influenced by the formulation of the chemical products than by the nutrient content in the fruits, although we found a highly significant reduction and inversely proportional relationship between the Mn concentrations and the appearance of russeting.