The excess of salts present in the water can limit the hydroponic cultivation of melon in semi-arid regions of the Brazilian Northeast, making it necessary to use strategies that allow the use of these waters. Among these strategies, the use of elicitor substances stands out, such as salicylic acid. In this context, this study aimed to evaluate the effect of foliar application of salicylic acid in mitigating the harmful effects of salt stress on the morphophysiology and production of 'Gaúcho' melon cultivated in a hydroponic system. A completely randomized design was adopted in a split-plot scheme, with four levels of electrical conductivity of the nutrient solution - ECsn (2.1, 3.2, 4.3, and 5.4 dS m-1) considered the plots and four salicylic acid concentrations - SA (0, 1.5, 3.0, and 4.5 mM), the subplots, with six replications. The foliar application of salicylic acid concentrations did not mitigate the deleterious effects of salt stress on the morphophysiology and yield of melon grown in hydroponic system. The concentration of 4.5 mM of salicylic acid intensified the harmful effects of the salinity of the nutrient solution on gas exchange and fresh weight of hydroponic melon.

In order to study the effect of salicylic acid concentrations on the mitigation of salt stress in melon plants grown on a hydroponic system an experiment was conducted in a greenhouse at Pombal – PB, Brazil, using an NFT (Nutrient Film Technique) system. The experimental design was completely randomized, in a 4 × 4 factorial scheme, corresponding to four levels of electrical conductivity of the nutrient solution—ECns (2.1—control, 3.2, 4.3, and 5.4 dS m⁻¹) and four concentrations of salicylic acid—SA (0, 1.5, 3.0, and 4.5 mM), with six replicates. Salicylic acid at the concentration of 3.2 mM attenuated the effect of nutrient solution salinity on the fresh weight of melon fruits. The saline nutrient solution impairs gas exchange and the relative water content and increases the intercellular electrolyte leakage in the leaf blade of melon plants. However, salicylic acid attenuates the deleterious effects of salinity and attains a maximum yield of melon fruits of 23.82 t ha⁻¹ with foliar application of 1.5 mM at ECns of 3.1 dS m⁻¹. Salicylic acid stimulated the synthesis of total chlorophyll, the CO₂ assimilation rate, and the instantaneous water use efficiency of hydroponic melon up to a concentration of 4.5 mM. The results obtained indicate that the responses of the hydroponic melon plant grown with saline nutrient solution and the application of salicylic acid are not yet fully elucidated.

The objective of this study was to evaluate the salicylic acid applications in attenuating the harmful effects of saline nutrient solution on the physiology and growth of 'Gaúcho' melon cultivated in the NFT hydroponic system. The experiment was conducted in a greenhouse, in Pombal-PB, Brazil. The cultivation system used was the Nutrient Film Technique - NFT hydroponics. A completely randomized split-plot design was used, with the plot referring to four levels of salinity in the nutrient solution - ECns (2.1 control, 3.2, 4.3, and 5.4 dS m-1) and the sub-plot four concentrations of salicylic acid (SA) (0, 1.5, 3.0, and 4.5 mM), applied via foliar spray, with six replications. Nutrient solution of 4.3 and 5.4 dS m-1 electrical conductivity promotes higher maximum and variable fluorescence, respectively. The stomatal conductance, transpiration, stem diameter, main branch length, leaf dry mass, and stem dry mass of ‘Gaúcho’ melon plants decrease with the increase in salinity of the nutrient solution. Salicylic acid increases the initial fluorescence and the main branch length of ‘Gaúcho’ melon plants in hydroponic cultivation. Salicylic acid at a concentration of 1.5 to 4.5 mM did not attenuate the effects of salt stress on the internal CO2 concentration, CO2 assimilation rate, and root dry mass of 'Gaúcho' melon plants.

DANO CELULAR E PIGMENTOS FOTOSSINTÉTICOS DO MARACUJAZEIRO-AZEDO EM FUNÇÃO DA NATUREZA CATIÔNICA DA ÁGUA GEOVANI SOARES DE LIMA1; WESLLEY BRUNO BELO DE SOUZA2; LAURIANE ALMEIDA DOS ANJOS SOARES3; FRANCISCO WESLEY ALVES PINHEIRO4; HANS RAJ GHEYI5 E VALESKA KAROLINI NUNES OLIVEIRA6 1 Unidade Acadêmica de Engenharia Agrícola, Universidade Federal de Campina Grande, UFCG, Rua Aprígio Veloso, 882 - Universitário, Campina Grande, PB, Brasil. E-mail: geovani.soares@p q.cnpq.br. 2 Unidade Acadêmica de Ciências Agrárias, Universidade Federal de Campina Grande, UFCG, Rua Jario Vieira Feitosa, 1770, Bairro dos Pereiros, Pombal, PB, Brasil. E-mail: weslleybruno96@hotmail.com. 3 Unidade Acadêmica de Ciências Agrárias, Universidade Federal de Campina Grande, UFCG, Rua Jario Vieira Feitosa, 1770, Bairro dos Pereiros, Pombal, PB, Brasil. E-mail: lauriane.soares@pq.cnpq.br. 4 Unidade Acadêmica de Engenharia Agrícola, Universidade Federal de Campina Grande, UFCG, Rua Aprígio Veloso, 882 - Universitário, Campina Grande, PB, Brasil. E-mail: wesley.ce@hotmail.com. 5Unidade Acadêmica de Engenharia Agrícola, Universidade Federal de Campina Grande, UFCG, Rua Aprígio Veloso, 882 - Universitário, Campina Grande, PB, Brasil. E-mail: hgheyi@gmail.com. 6 Unidade Acadêmica de Ciências Agrárias, Universidade Federal de Campina Grande, UFCG, Rua Jario Vieira Feitosa, 1770, Bairro dos Pereiros, Pombal, PB, Brasil. E-mail: valeska.karoline2015@gmail.com. 1 RESUMO Este trabalho teve como objetivo de avaliar o dano celular e os teores de pigmentos fotossintéticos do maracujazeiro-azedo em função da natureza catiônica da água de irrigação. O experimento foi desenvolvido sob condições de casa-de-vegetação em Pombal-PB. O delineamento experimental foi o de blocos casualizados, sendo os tratamentos constituídos de seis natureza catiônica da água (S1-Testemunha; S2 - Na+; S3 - Ca2+; S4 - Na+ + Ca2+; S5 - Mg2+ e S6 - Na+ + Ca2+ + Mg2+), distribuídos em delineamento de blocos ao acaso com quatro repetições, sendo a parcela constituída de duas plantas. As plantas do tratamento testemunha (S1) foram irrigadas com água de condutividade elétrica (CEa) de 0,3 dS m-1 e as demais (S2; S3; S4; S5 e S6) foram cultivadas com CEa de 3,0 dS m-1. A irrigação com água de composição Na+ e Na+ + Ca2+ resultou em maior dano celular nos tecidos foliares. A síntese de clorofila a foi inibida pela salinidade de natureza Mg2+ e Na+ + Ca2+ + Mg2+. A salinidade da água afetou negativamente os teores de clorofila b do maracujazeiro-azedo. O uso de água com composição sódica induziu aumento na síntese de carotenoides em plantas de maracujazeiro-azedo. Palavras-chave: Passiflora edulis Sims, estresse salino, semiárido. LIMA, G. S. de; SOUZA, W. B. B. de; SOARES, L. A. dos A.; PINHEIRO, F. W. A.; GHEYI, H. R.; OLIVEIRA, V. K. N. CELL DAMAGE AND PHOTOSYNTHETIC PIGMENTS OF THE SOUR PASSION FRUIT IN FUNCTION OF THE CATIONIC NATURE OF WATER 2 ABSTRACT This study had the objective of evaluating the cellular damage and the levels of photosynthetic pigments of the sour passion fruit in function of the cationic nature of the irrigation water. The experiment was conducted under greenhouse conditions in Pombal -PB. The experimental design was randomized blocks, with treatments consisting of six cationic nature of water (S1 - Control; S2 - Na+; S3 - Ca2+; S4 - Na++ Ca2+; S5 - Mg2+ and S6 - Na++ Ca2++ Mg2+), distributed in a randomized block design with four replications, and each plot consisting of two plants. The plants of the control treatment (S1) were irrigated with water of electrical conductivity (ECw) of 0.3 dS m-1 while those of the other (S2; S3; S4; S5 and S6) were cultivated with ECw of 3.0 dS m-1. Irrigation with Na+ and Na++ Ca2+ water resulted in greater cellular damage in the leaf tissues. The synthesis of chlorophyll a was inhibited by salinity of Mg2+ and Na++ Ca2++ Mg2+. The salinity of the water negatively affected the chlorophyll b content of the sour passion fruit. The use of water with sodium composition induced an increase in the synthesis of carotenoids in sour passion fruit plants. Keywords: Passiflora edulis Sims, saline stress, semiarid.

He high concentrations of salts present in the water sources of the Brazilian Northeastern semi-arid region stand out as one of the limiting factors for agricultural production, contributing to soil salinization and/or sodification. Thus, it is extremely important to identify strategies to mitigate the effects of salt stress on plants, such as the foliar application of salicylic acid. In this context, the objective of the present study was to evaluate the effect of foliar application of salicylic acid as an attenuator of salt stress on leaf gas exchange, water relations, photosynthetic pigments, and growth of okra cv. Canindé grown in a hydroponic system. The experiment was conducted in a greenhouse, in Pombal, PB, Brazil. The treatments consisted of four levels of electrical conductivity of the nutrient solution - ECns (3.0, 5.0, 7.0, and 9.0 dS m-1) and four concentrations of salicylic acid - SA (0, 1.2, 2.4, and 3.6 mM) distributed in a completely randomized design in a split-plot scheme, considering the ECns levels as the plots and SA concentrations as the subplots, with four replicates and two plants per plot. ECns from 3.0 dS m-1 inhibited the synthesis of photosynthetic pigments, leaf gas exchange, and growth of okra cv. Canindé. Foliar application of salicylic acid at concentrations of up to 3.6 mM does not alleviate the effects of salt stress on water relations, gas exchange and growth of okra. Salicylic acid at a concentration of 1.8 mM stimulates chlorophyll a and b biosynthesis in okra under ECns of 3.0 and 4.0 dS m-1, respectively.

The objective of this study was to evaluate the water status, photosynthetic pigments, and photochemical efficiency of mini watermelon plants under salt stress and phosphate fertilization. The experiment was conducted in pots under greenhouse conditions in Pombal, PB, Brazil. The experimental design used was randomized blocks in a 5 × 4 factorial scheme, with five levels of electrical conductivity of irrigation water - ECw (0.3, 1.3, 2.3, 3.3, and 4.3 dS m^-1) and four doses of phosphorus (60, 80, 100, and 120% of the recommendation), with three replicates. The relative water content in the tissues decreased with the increase in ECw levels in all phosphorus doses, with decreases of 7.05, 7.81 and 8.83% per unit increase in ECw, in plants fertilized with 80, 100 and 120% P₂O₅. On the other hand, ECw levels increased electrolyte leakage, regardless of phosphorus doses of the recommendation. The synthesis of photosynthetic pigments and the quantum efficiency of photosystem II were inhibited by increasing water salinity from 0.3 dS m^-1 in plants grown under phosphorus doses above 60% of the recommendation. Water salinity from 0.3 dS m^-1 reduced chlorophyll b contents, initial, maximum, and variable fluorescence of mini watermelon plants, with a decrease of 11.86, 4.51, 4.53, and 4.54% per unit increment of ECw, respectively.