Banca de QUALIFICAÇÃO: ALISON ROCHA DE ARAGAO

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : ALISON ROCHA DE ARAGAO
DATA : 02/06/2025
HORA: 14:00
LOCAL: Google Meet (online)
TÍTULO:

SILICON IMPROVES SALT TOLERANCE IN MELON (Cucumis Melo) BY NEUTRALIZING REACTIVE OXYGEN SPECIES, AND ENHANCING ANTIOXIDANT DEFENSE MECHANISMS

MODEL OF GROWTH VERSUS ELECTRICAL CONDUCTIVITY OF NUTRIENT SOLUTION OF MELON CULTIVARS UNDER SOILLESS CULTURE SYSTEM

PALAVRAS-CHAVES:

Cucumis melo L.; Vegetative growth; Water absorption; Salinity; Fertigation; Salinity stress; oxidative stress; antioxidant enzymes; mineral balance

PÁGINAS: 35
RESUMO:

Soil salinity is one of the main limiting factors for agricultural production, affecting plant growth and metabolism. This study evaluated the effects of different salinity levels (0.5, 2.5, and 4.5 dS m⁻¹) and silicon application (2 mmol L⁻¹) on growth, biochemical responses, and ionic balance of two melon cultivars (Acclaim and Caribbean Gold). Increased salinity reduced plant height in both cultivars, with decreases of up to 19% (Acclaim) and 18% (Caribbean Gold) under high salinity. Silicon partially mitigated these effects, being more effective in Caribbean Gold, where it promoted up to a 25% increase in leaf potassium content and reduced sodium accumulation by 14%. In Acclaim, silicon stabilized leaf biomass and the K/Na ratio, though with lower efficiency. Biochemical analyses revealed distinct antioxidant strategies: Acclaim maintained high basal catalase (CAT) activity, while Caribbean Gold increased the activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX) under stress, especially with silicon. Furthermore, Caribbean Gold showed a greater reduction in electrolyte leakage (9%) and malondialdehyde (MDA) levels (14%) with silicon, indicating more effective protection against oxidative damage. It is concluded that Caribbean Gold exhibits greater physiological plasticity in response to silicon, while Acclaim displays greater intrinsic metabolic stability. Silicon proved to be a promising strategy to alleviate the effects of salinity, especially in more sensitive cultivars, by supporting ionic balance and protection against oxidative stress. These findings highlight the importance of varietal selection and nutritional management for cultivation under saline conditions. To exploit the full potential of melons, it is essential to provide an adequate electrical conductivity (EC) of the nutrient solution during critical growth stages. EC, an estimate of the total ionic concentration in the nutrient solution, is crucial for plant development. Inadequate management of EC can impair growth and productivity due to toxicity or nutrient deficiency. The aim of our study was to evaluate the effect of electric conductivities (ECs) of nutrient solution on the vegetative growth of three melon cultivars in soilless culture. The plants were cultivated at the University of Almería (Spain) in a controlled chamber in a pot with 0.5 L of coconut fiber. The treatments with standard macro- and micronutrient content were the EC supplied at 2.0, 3.0, 4.0, 5.0, 6.0 dS m-1. The parameter measured were vegetative growth, absorption of water, nitrate and potassium from fertigation. Controlling the pH and electrical conductivity (EC) of the drainage solution is crucial in fertigation for soilless systems. This study observed an initial solution pH of 5.8, which increased by an average of 0.22 in the first week and 0.53 by the fourth week, with the most variation in the 'Jadeal' cultivar. EC increased progressively, with weekly changes ranging from 21.9% to 35.04%, varying according to the nutrient solution's EC. The highest water uptake occurred between 3.0 and 4.0 dS m-1 for 'Caribbean Gold' and 'Finura', and between 3.0 and 6.0 dS m-1 for 'Jadeal', with reduced uptake at higher and lower EC values. Nitrate and potassium absorption patterns mirrored water uptake, peaking within specific EC ranges. Optimal growth was observed at 3.0 to 4.0 dS m-1, with significant reductions in growth at sub-optimal and supra-optimal EC levels. These findings underscore the importance of precise EC control in fertigation to optimize plant development.

MEMBROS DA BANCA:
Externo à Instituição - JACKSON SILVA NÓBREGA - UFERSA
Externo à Instituição - FRANCISCO VANIES DA SILVA SA - UFERSA
Presidente - 1632114 - PATRICIA LIGIA DANTAS DE MORAIS