ABSTRACT Salinity is one of the main challenges in agriculture, especially in arid and semi-arid regions. Salicylic acid application may be a strategy to mitigate the harmful effects of salt stress on plant growth. Basil (Ocimum basilicum ) is a medicinal, spice, and ornamental plant grown around the world that has its growth reduced by salt stress. Therefore, the objective was to evaluate salicylic acid in mitigating the damage caused by salt stress in ‘Cinnamon’ basil. Growth was evaluated at 90 days after the start of irrigation with saline water. Salicylic acid application attenuates the harmful effects of salt stress on the number of leaves, number of inflorescences, leaf dry mass, inflorescence dry mass, root dry mass, seed mass, leaf area, leaf area ratio, specific leaf area, leaf mass ratio, root mass ratio, inflorescence mass ratio, Dickson quality index, sclerophilia index, robustness quotient and shoot root ratio. Salt stress decreased plant height, stem diameter, stem dry mass, and stem mass ratio of basil ‘Cinnamon’. Salicylic acid can be used to lessen the harmful effects of salt stress on basil ‘Cinnamon’.

ABSTRACT Several abiotic factors, such as water availability, significantly affect the development of forest species found in the understory. This research aimed to evaluate morphophysiological characteristics in plants of Erythroxylum pauferrense submitted to different water regimes. The experiment was developed in a greenhouse at the Federal University of Paraíba, Campus II, Areia, Paraíba, Brazil. The experimental design was in randomized blocks, with five water treatments [100%, 80%, 60%, 40% and 20% of the pot capacity (PC)] and four replications. Growth attributes, morphofunctional aspects, gas exchange, chlorophyll fluorescence and chlorophyll indices were evaluated. The data were submitted for analysis of variance, and in cases of significance, polynomial regression analyses were performed. The plants of Erythroxylum pauferrense submitted to 100% and 80% water levels of the PC present greater development and morphophysiological performance. In comparison, the evaluated parameters were significantly reduced in the regime of greater water stress (20% of the PC). Thus, the water regime of 80% of PC is the most recommended for producing seedlings of Erythroxylum pauferrense, promoting greater growth and significant changes in morphofunctional aspects, gas exchange, chlorophyll fluorescence and chlorophyll indexes.

RESUMO Vários fatores abióticos, como a disponibilidade de água, afetam significativamente o desenvolvimento das espécies florestais encontradas no sub-bosque. Esta pesquisa teve como objetivo avaliar características morfofisiológicas em plantas de Erythroxylum pauferrense submetidas a diferentes regimes hídricos. O experimento foi desenvolvido em casa de vegetação na Universidade Federal da Paraíba, Campus II, Areia, Paraíba, Brasil. O delineamento experimental foi em blocos ao acaso, com cinco tratamentos hídricos [100%, 80%, 60%, 40% e 20% da capacidade do vaso (PC)] e quatro repetições. Foram avaliados atributos de crescimento, aspectos morfofuncionais, trocas gasosas, fluorescência da clorofila e índices de clorofila. Os dados foram submetidos à análise de variância e, nos casos de significância, análises de regressão polinomial. As plantas de Erythroxylum pauferrense submetidas a regimes hídricos de 100% e 80% da PC apresentam maior desenvolvimento e desempenho morfofisiológico. Em comparação, os parâmetros avaliados foram significativamente reduzidos no regime de maior estresse hídrico (20% da PC). Assim, o regime hídrico de 80% de PC é o mais recomendado para produção de mudas de Erythroxylum pauferrense, promovendo maior crescimento e alterações significativas nos aspectos morfofuncionais, trocas gasosas, fluorescência da clorofila e índices de clorofila.

ABSTRACT Basil (Ocimum gratissimum - Lamiaceae), is a sub-shrub plant species with great economic importance for several regions, and studies on its growth, physiology, and reproduction become needed. The aimed research was to obtain a regression equation to estimate leaf area of O. gratissimum. 250 basil leaves were collected and the linear dimensions (length and width) and real leaf area of each leaf were measured. From these data, the products between length and width, length and length were calculated. Equations were obtained using regression models: linear, linear without intercept, quadratic, cubic, power, and exponential. The best equation was selected based on determination coefficient, Pearson’s correlation coefficient, Willmott’s agreement index and CS index, Akaike information criterion, mean absolute error and root mean square error. All equations proposed using the product between length and width (LW) can be used to predict the leaf area of O. gratissimum. However, the equation LA=0.54*LW1.03 (power model) is the most recommended to estimate the leaf area of this species.

ABSTRACT Ocimum basilicum L. (basil) is an annual herb belonging to the Lamiaceae family that has economic importance for many regions around the world. Thus, ecophysiological studies are needed to assess this species growth and dispersal. This work aimed to obtain equations from regression models that meaningfully estimate the leaf area of basil cultivars using linear dimensions of leaves. For this purpose, 300 leaves from 'Italiano Roxo' and 500 leaves from 'Folha Fina' cultivar were collected from plants cultivated in a greenhouse. Then, the length, width, and leaf area of each leaf were measured, and product of length by width were calculated. The equations were adjusted using the simple linear, linear without intercept, quadratic, cubic, power, and exponential regression models. Criteria for selecting the best equations were highest determination coefficient and Willmott's agreement index, lowest Akaike information criterion and root mean square error, and BIAS index closest to zero. All the equations fitted using the product of length by width (L.W) can estimate the leaf area of basil cultivars. Thus, basil leaf area can be estimated through a non-destructive method using linear dimensions of leaves. However, the equation ŷ = 0.8175*LW0.9307 is the most suitable for 'Italiano Roxo' and ŷ = 0.6335*LW for 'Folha Fina'.

Abstract Climatic variation throughout the day influences the ecophysiological performance of plants at different growth stages and phases. Therefore, this work aimed to evaluate the effect of climatic variation on ecophysiological aspects of T. roseoalba and H. heptaphyllus at different hours of the day and indicate the ideal time for measuring ecophysiological variables in these species. The research was carried out in a greenhouse at the forest nursery of the Federal University of Paraíba, Campus II, in the municipality of Areia, Paraíba state, Northeastern Brazil. The experimental design was completely randomized, consisting of 10 evaluation times throughout the day (from 8 am to 5 pm), with 1 h hour interval between each evaluation. Temperature and air relative humidity inside and outside the greenhouse were evaluated to understand the effect on gas exchange (net assimilation rate of CO2, stomatal conductance, transpiration rate, internal concentration of CO2, and vapor-pressure deficit) and chlorophyll a fluorescence (initial, maximum, and variable fluorescence, photochemical quenching, and electron transport rate). Data were submitted to canonical correlation analysis and principal component analysis to verify the relationship between climatic and ecophysiological variables. For both species, higher correlation was found between internal and external relative humidity with all the ecophysiological variables analyzed, except for initial fluorescence. Thus, climatic factors influenced the photosynthetic performance of T. roseoalba and H. heptaphyllus plants, and 8 am to 9 am is indicated for carrying out ecophysiological evaluations in both species.

ABSTRACT The determination of leaf area is fundamental for studies related to plant growth and physiology. Thus, non-destructive methods allow an accurate estimate of the leaf area through linear dimensions of the leaves. The research objective was to construct allometric equations to estimate the leaflet area of peanut cultivars. Then, 2,605 leaflets were collected from six peanut cultivars (IAC Caiapó, IAC 8112, Runner IAC 886, BRS Havana, BRS 151 L7, and IAC Tatuí), with more than 400 leaflets sampled for each cultivar. We measured the length, width, product between length and width, and leaflet area. Linear and non-linear models (linear, linear without intercept, power, and exponential) were built, and the best equation was chosen using the statistical criteria: highest coefficient of determination (R2), Pearson’s linear correlation coefficient (r), Willmott’s agreement index (d), lowest Akaike information criterion (AIC), and root mean square of the error (RMSE). It was found that the models that used the product between length and width were the most suitable for estimating the leaflet area of peanut cultivars. Given the little intraspecific morphological variability, it was possible to group the cultivars, and model y ^ = 0.875 * LW0.929 was indicated to estimate the peanut leaflet area accurately, regardless of the cultivar.

Resumen El agua en las regiones semiáridas contiene sales en exceso. Cuando no se dispone de agua de buena calidad, es necesario utilizar estrategias que permitan el uso de agua salina. El objetivo de este estudio fue evaluar los efectos de la aplicación del regulador del crecimiento vegetal en el cultivo de albahaca bajo estrés salino. El experimento se llevó a cabo en un diseño de bloques al azar, en la matriz “Compuesto Central de Box”. Se evaluó la altura de la parte aérea, el diámetro del tallo, el área de la hoja, las masas secas y las características químicas del suelo. La salinidad del agua de riego provoca la reducción de los parámetros de crecimiento de la albahaca, con la excepción de la masa seca de inflorescencia. Las aplicaciones del regulador del crecimiento vegetal tienen efecto sobre el crecimiento de la albahaca cuando las plantas se riegan con agua salina.

Abstract The water in semiarid regions contains salts in excess. When good quality water is not available it is necessary to use strategies that can make feasible the use of saline water. The aim of this study was to evaluate the effects of the application of the plant growth regulator on the culture of basil stressed with salt. The experiment was carried out in a randomized block design by the matrix “Central Box Compound”. Shoot height, stem diameter, leaf area, dry masses and soil chemical characteristics were evaluated. The salinity of the irrigation water causes reduction of the basil growth parameters, with the exception of the inflorescence dry mass. Plant growth regulator applications have effect on basil growth when plants are irrigated with saline water.

Abstract The aim of this study was to evaluate the initial growth of Agonandra brasiliensis Miers ex Benth. & Hook. F. in response to different levels of shading and doses of controlled-release fertiliser (CRF). The experiment was conducted at Embrapa Roraima in Boa Vista, in a completely randomised experimental design and a 2 x 5 factorial scheme, of two luminosity levels (50 and 30%) and five doses of CRF (formulation 18-05-09, NPK) (0, 0.5, 1, 2 and 3 g L-1 substrate), with five replications, each consisting of five plants. At 240 days after transplanting, the growth characteristics were evaluated, and the influence of the light levels and the CRF dose was recorded on these characteristics, either individually or interactively. It is suggested that plants of Agonandra brasiliensis be fertilised with a dose of 2 g L-1 CRF and grown in an environment with 50% of luminosity to maximize growth and efficiency in the production of high-quality seedlings.

ABSTRACT Bell pepper (Capsicum annuum) is one of the most consumed vegetables around the world. Balanced fertilization is essential for growing this vegetable. The objective of this study was to evaluate the yield and morphological attributes of bell pepper under doses and times of application of biological fertilizers. Two experiments were carried out with applications of biological fertilizers prepared from manure and enriched organic compounds with cattle manure and sheep manure. The experimental design was a randomized complete block design, in a 4 x 3 + 1 factorial scheme, with three replications, referring to doses of biological fertilizers (100, 200, 300 and 400 L ha-1), times of application (0, 30 and 60 days after transplanting - DAT) and control. The evaluated variables were: total fruit weight (TFW), number of commercial fruits (NCF), number of non-commercial fruits (NNCF), fruit weight (FW), fruit diameter (FD), fruit length (FL), resistance of fruit peel (RFP), number of flower buds (NFB) and productivity (P). Biological fertilizers caused positive effects on TFW, NCF, FW and P of bell pepper. The application of cattle manure at 60 DAT and sheep manure at 30 DAT promoted a larger fruit diameter. The FW, FL and RFP were influenced by the doses and times of application of biological fertilizers. The application of biofertilizers is efficient in the production of bell pepper.

RESUMO Agonandra brasiliensis é uma árvore de florestas tropicais, com ampla ocorrência na região do Cerrrado brasileiro. Apesar do seu potencial como madeira e para reflorestamento, eficientes protocolos para a produção de mudas ainda estão em falta. Objetivou-se avaliar características morfológicas para a qualidade de mudas de A. brasiliensis, em condições de viveiro, em função do volume do recipiente e dose de fertilizante de liberação controlada. O experimento foi realizado em esquema fatorial 2 x 5, testando-se dois volumes (1,8 L e 2,2 L) de recipiente e cinco doses (0 g L-1, 1 g L-1, 2 g L-1, 4 g L-1 e 8 g L-1) do fertilizante encapsulado Forth Cote® (formulação NPK 15-09-12). As parcelas constituíram-se de cinco mudas homogêneas transplantadas em sacos de polietileno (15 cm x 35 cm) com substrato de areia média lavada. As seguintes características foram mensuradas: comprimento da parte aérea; diâmetro do caule; incrementos em comprimento e diâmetro; matéria seca total; matéria seca da parte aérea e da raiz e a razão entre elas. Também foi determinado o Índice de Qualidade de Dickson. A qualidade das mudas para caracteres morfológicos como comprimento da parte aérea, diâmetro de caule e matéria seca total foi especialmente favorecida por tratamentos que combinaram o fertilizante de liberação controlada em dose aproximada de 5,0 g L-1 e recipiente com volume de 2,2 L.

ABSTRACT Agonandra brasiliensis is a tree from tropical forests, with a wide occurrence in the Brazilian Savannah region. Despite its potential as wood and for reforestarion, efficient protocols for its seedling production are still lacking. This study aimed to assess morphological characteristics for the seedling quality of A. brasiliensis, under nursery conditions, as a function of container volume and controlled-release fertilizer dose. The experiment was carried out in a 2 x 5 factorial scheme, testing two container volumes (1.8 L and 2.2 L) and five doses (0 g L-1, 1 g L-1, 2 g L-1, 4 g L-1 and 8 g L-1) of the encapsulated fertilizer Forth Cote™ (formulation NPK 15-09-12). The plots consisted of five homogeneous seedlings transplanted in polyethylene bags (15 cm x 35 cm) with washed medium sand substrate. The following characteristics were measured: shoot length; stem diameter; increases in length and diameter; total dry matter; shoot and root dry matters and the ratio between them. The Dickson Quality Index was also obtained. The seedling quality for morphological traits, such as shoot length, stem diameter and total dry matter, was especially favoured by treatments combining the controlled-release fertilizer at a dose around 5.0 g L-1 and container volume of 2.2 L.

RESUMEN La calidad química del suelo es uno de los factores más rápidamente afectados por los procesos de degradación antropogénica, y este es uno de los componentes más importantes para el desarrollo de la agricultura. Por lo tanto, este trabajo tuvo como objetivo evaluar los efectos de las diferentes dosis de estiércol de ganado y polvo de roca en las características químicas del suelo en cultivo de col rizada de mantequilla. Los tratamientos se organizaron en cinco bloques aleatorizados en un factorial de 4x4 en referencia a las diferentes dosis de estiércol bovino (60, 120, 180 y 240 g/planta) combinado con dosis de polvo de roca (6, 12, 18 y 24 g/planta). Cada bloque estuvo constituido por tres parcelas de 18 m de largo y 1 m de ancho, el lecho estuvo compuesto por seis porciones y cada parcela experimental constaba de 14 plantas espaciadas en 0,40x0,40 m. Al final del experimento se analizaron: pH, materia orgánica, P, K, Na, Mg, acidez intercambiable, capacidad de intercambio catiónico (CIC), suma de base y saturación por base. Las dosis de estiércol bovino y MB-4 proporcionaron un aumento en el pH, materia orgánica, concentración de fósforo, potasio, sodio, calcio, magnesio, acidez intercambiable, capacidad de intercambio catiónico, suma de la base y saturación de la base del suelo. Las dosis de 240 g de estiércol de ganado y 24 g de polvo de roca generaron un aumento en las propiedades químicas del suelo.

ABSTRACT Chemical soil quality is one of the factors more quickly affected by anthropogenic degradation processes and is one of the more important components for the development of agriculture. Thus, this study aimed to evaluate the effects of different doses of cattle manure and rock powder on the chemical characteristics of soil cultivated with butter kale. The treatments were arranged in five randomized blocks in a 4x4 factorial for the different doses of bovine manure (60, 120, 180 and 240 g/plant) combined with doses of rock powder (6, 12, 18 and 24 g/plant). Each block was composed of three plots, 18 m long and 1 m wide. The bed was composed of six portions, and each experimental plot consisted of 14 plants spaced at 0.40x0.40 m. At the end of the experiment, the following were analyzed: pH, organic matter, P, K, Na, Mg, exchangeable acidity, cation exchange capacity (CEC), sum of base and base saturation. The doses of bovine manure and MB-4 provided an increase in pH, organic matter, concentration of phosphorus, potassium, sodium, calcium, magnesium, exchangeable acidity, cation exchange capacity, sum of the base and saturation of the soil base. The doses of 240 g of cattle manure and 24 g of rock dust generated an increase in the chemical properties of the soil.

RESUMEN En los últimos años el uso de aguas salinas en la agricultura es una alternativa, principalmente en virtud de la escasez hídrica. Sin embargo, las plantas no toleran altos niveles de sales, por lo que el uso de atenuadores de estrés salino puede ser una estrategia para posibilitar el uso de aguas salinas en la agricultura. En este sentido, este trabajo tiene como objetivo evaluar el efecto de aguas salinas y aplicación de silicio sobre el crecimiento, pigmentos cloroplatísdicos, fluorescencia de la clorofila a y producción de remolacha. El experimento fue conducido en un diseño de bloques al azar, en factorial 5 X 5, referente a cinco niveles de conductividad eléctrica del agua de riego (CEa): (0,5; 1,3; 3,25; 5,2 y 6 dS m-1) y cinco dosis de silicio (0,00; 2,64; 9,08; 15,52 y 18,16 mL L-1), combinadas según la matriz experimental Compuesto Central de Box, con cuatro repeticiones y tres plantas por parcela. El aumento de la conductividad eléctrica en el agua de riego reduce el crecimiento y la producción de remolacha, pero los índices de clorofila, la producción de biomasa y la fluorescencia no están influenciados por el riego con aguas salinas. La aplicación de silicio a través del suelo promueve un incremento en el crecimiento y la fluorescencia de la clorofila a, sin embargo, no reduce el efecto nocivo del estrés salino. La conductividad eléctrica en el agua de riego por encima de 0,50 dS m-1 es suficiente para afectar negativamente el cultivo de la remolacha y la dosis de 9,08 ml L-1 de silicio es la más recomendada para su aplicación.

ABSTRACT In recent years, the use of saline water in agriculture has become an alternative mainly because of water scarcity. However, plants do not tolerate high salt contents; so, the use of salt stress attenuators could enable saline water usage in agriculture. This study aimed to assess the effect of saline water and silicon applications on growth, chloroplastid pigments, chlorophyll fluorescence a and beet production. The experiment was conducted with complete randomized blocks in a 5 x 5 combined factorial arrangement according to the Central Composite of Box experiment matrix for the electrical conductivity in the irrigation water (ECw) and silicon doses (Si), with minimum (- a) and maximum (a) values from 0.5 to 6.0 dS m-1 and from 0.00 to 18.16 mL L-1, totaling nine treatments, with four replicates and three plants per plot. The irrigation water ECw increase reduced growth and beet production, but the chlorophyll contents, biomass and fluorescence production were not affected by salinity. Silicon applications via the soil increased growth and chlorophyll fluorescence a but did not reduce the harmful effect of the salt stress. The irrigation water ECw above 0.50 dS m-1 negatively affected the beet crop. The silicon dose of 9.08 mL L-1 is the most recommended application.

RESUMEN El rábano es una hortaliza de ciclo corto que presenta excelentes propiedades nutricionales y medicinales. Es considerada rústica, pues tolera condiciones adversas, con énfasis en la posibilidad de poder ser regado con agua salada, principalmente cuando se asocia a la atenuación del estrés causado. En este contexto, el presente trabajo tuvo como objetivo evaluar el efecto de conductividades eléctricas del agua de riego y de dosis de ácido ascórbico en el desempeño agronómico e intercambios gaseosos del rábano. El experimento fue conducido en un ambiente protegido, en el Centro de Ciencias Agrarias de la Universidad Federal de Paraíba, Areia, Paraíba (Brasil). El diseño experimental fue hecho en bloques aleatorizados, con cinco dosis de ácido ascórbico (0,0; 0,29; 1,0; 1,71 y 2,0 mM) y cinco conductividades eléctricas del agua de riego (0,5; 1,3; 3,25; 5,2 y 6,0 dS m-1), con cuatro repeticiones. El crecimiento, los intercambios gaseosos y la producción fueron evaluados. Las dosis de ácido ascórbico no fueron significativas. El aumento de las conductividades eléctricas del agua de riego disminuyó el desempeño agronómico y los intercambios gaseosos, salvo para fotosíntesis neta, eficiencia del uso del agua y eficiencia instantánea de carboxilación, que no presentaran importancia. Hubo una relación de la fotosíntesis neta, transpiración, concentración interna de CO2 y eficiencia del uso del agua con la conductancia estomática. El desempeño agronómico y el intercambio gaseoso del cultivo de rábano son influenciados por la salinidad. La aplicación de ácido ascórbico a través de la hoja no influye en el rendimiento agronómico y los intercambios gaseosos del rábano a las dosis probadas.

ABSTRACT The radish is a short-cycle vegetable that has excellent nutritional and medicinal properties. It is considered rustic, meaning it tolerates adverse conditions with the possibility of being irrigated with saline water, which creates stress. In this context, this study aimed to evaluate the effect of electrical conductivities in irrigation water and doses of ascorbic acid on the agronomic performance and gaseous exchanges of radishes. This experiment was carried out in a protected environment at the Agricultural Sciences Center of the Federal University of Paraíba, Areia, Paraíba (Brazil). The experiment design used randomized blocks with five doses of ascorbic acid (0.0, 0.29, 1.0, 1.71 and 2.0 mM) and five electrical conductivities in the irrigation water (0.5, 1.3, 3.25, 5.2 and 6.0 dS m-1), with four replicates. The growth, gas exchange and production were evaluated. The doses of ascorbic acid were not significant. The increase in the electrical conductivities of the irrigation water provided a reduction in the agronomic performance and gas exchanges, except for the net photosynthesis, water use efficiency and instantaneous carboxylation efficiency, which were not significant. There was a relationship between the net photosynthesis, transpiration, internal concentration of CO2 and water use efficiency and the stomatal conductance. The agronomic performance and gaseous exchanges of the radish culture were influenced by the salinity. The foliar application of ascorbic acid did not influence the agronomic yield and gaseous exchanges of the radishes at the tested doses.

Resumen Maracujá-do-mato (Passiflora cincinnata) es una especie adaptada a las condiciones climáticas de la región semiárida brasileña y ampliamente utilizada como portainjertos, sin embargo, los estudios relacionados con la producción de plántulas y su resistencia a estrés abióticos son escasos en la literatura. El objetivo de este estudio fue medir la producción de plántulas de maracuyá bajo el efecto de la conductividad eléctrica en el agua de riego en función de la aplicación de fertilizantes orgánicos. El experimento se desarrolló en la Universidade Estadual da Paraíba, Catolé do Rocha-PB, Brasil, en un diseño experimental completamente aleatorizado, en un esquema factorial de 5 x 3, con seis replicaciones. Los factores evaluados fueron cinco conductividades eléctricas de agua de riego (ECw: 1; 2; 3; 4 y 5 dS m-1) y la aplicación de tres fertilizantes orgánicos (orina de bovino, biofertilizante bovino y humus de lombriz líquida). Se encontró que el aumento de ECw afectó negativamente la morfología y la calidad de las plántulas, mientras que el biofertilizante bovino presentó una mayor eficiencia en comparación con los demás tratamientos. Se concluye que el uso de fertilizantes orgánicos como efectos atenuantes de la salinidad es una estrategia para la producción de plántulas de pasiflora en condiciones de suelos salinos.

Abstract Maracujá-do-mato (Passiflora cincinnata) is a species adapted to the climatic conditions of the Brazilian semi-arid region and widely used as rootstock, however, studies related to the production of seedlings and their resistance to abiotic stresses are scarce in literature. The objective was to study the production of maracujá-do-mato seedlings under the effect of the electrical conductivity on the irrigation water as a function of the application of organic fertilizers. The experiment was developed at the Paraíba State University, Catolé do Rocha-PB, in a completely randomized experimental design, in a 5 x 3 factorial scheme, with 6 replicates. The factors evaluated were five electrical conductivities of irrigation water (ECw: 1; 2; 3; 4 and 5 dS m-1) and application of three organic fertilizers (bovine urine, bovine biofertilizer and liquid earthworm humus). It was verified that the increase of ECw affected the morphology and the quality of the seedlings negatively, while the bovine biofertilizer presented better efficiency in comparison to the others. It is inferred that the use of organic fertilizers as mitigating effects of salinity may be a strategy for production of maracujá-do-mato seedlings in saline conditions.

Resumen El uso de aguas salinas en la agricultura surge como alternativa al aumento en la demanda de agua, principalmente en regiones áridas o semiáridas. Sin embargo, el uso de agua con alto contenido de sales causa disturbios en las plantas pudiendo llevar hasta la muerte de las mismas. Por esta razón, se buscan alternativas para atenuar tales efectos. Actualmente, los antioxidantes se utilizan para mitigar los efectos de las sales en las plantas; entre estos antioxidantes s el ácido ascórbico ha sido frecuentemente mencionado. Basado en lo expuesto, este trabajo tuvo por objetivo evaluar el efecto del riego con aguas salinas combinado con la aplicación de ácido ascórbico, sobre el desarrollo y actividades fotosintéticas de plantas de rábano (Raphanus sativus L.). El experimento fue desarrollado en ambiente protegido en bloques al azar con esquema factorial incompleto 5x5, con cinco conductividades eléctricas del agua de riego (ECw: 0.50, 1.30, 3.25, 5.20 y 6.00 dS m-1) y cinco dosis de ácido ascórbico (AA: 0.00, 0.29, 1.00, 1.71 y 2.00 mM). Las características evaluadas fueron altura de plantas, número de hojas, diámetro de la raíz tuberosa, índice de clorofila a, b, y total, relación de clorofila a/b, fluorescencia inicial, fluorescencia máxima, fluorescencia variable y rendimiento cuántico del fotosistema II. El uso de agua salina influenció todas las variables analizadas en el cultivo del rábano independiente de la utilización del ácido ascórbico. El uso del ácido ascórbico no fue eficiente como atenuante de los efectos de la salinidad del agua de riego sobre el desarrollo y la fluorescencia del cultivo del rábano. Sin embargo, se observó que la aplicación del ácido ascórbico en la dosis de hasta 1.00 mM promueve el aumento en los índices de clorofilas a, b y total del rábano sometido al estrés salino.

Abstract The use of saline or low-quality water in agriculture is an alternative to increasing water demand, especially in arid or semi-arid regions. However, the use of water with high levels of salts causes disturbances in plants, which can lead to their death; thus, alternatives to mitigate these effects are relevant in current agriculture. Currently, antioxidants are used to mitigate the effects of salts in plants, and among them ascorbic acid has been frequently mentioned. Therefore, the aim of this study was to evaluate the effect of irrigation with saline water combined with applications of ascorbic acid on the development and photosynthetic activity of radish (Raphanus sativus L.) plants. This experiment was carried out in a greenhouse with a randomized block design, with the treatments distributed in a 5x5 incomplete factorial scheme, composed of five electrical conductivities of the irrigation water (ECw): 0.50, 1.30, 3.25, 5.20 and 6.00 dS m-1, and five ascorbic acid (AA) doses: 0.00, 0.29, 1.00, 1.71, and 2.00 mM. The evaluated variables were: shoot height, leaf number, tuberous root diameter, chlorophyll a, b and total content, chlorophyll a/b ratio, initial fluorescence, maximum fluorescence, variable fluorescence and quantum yield of photosystem II. The saline water influenced the analyzed variables in the radish crop regardless of the ascorbic acid application. The ascorbic acid was not efficient in attenuating the deleterious effect of salinity in the irrigation water on the development and fluorescence of the radish. However, it was observed that the concentration of 1.00 mM of ascorbic acid promoted an increase in chlorophyll a, b and total in the salt-stressed radish plants.