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 Pomegranate is a fruit with potential for exploitation in the Brazilian Northeast as medicine and food. However, the qualitative and quantitative scarcity of water resources is common in this region, requiring the use of water with high salt contents in irrigated agriculture. The adoption of strategies to reduce the harmful effects of salt stress in plants is therefore necessary, and foliar nitrogen (N) fertilization is a promising alternative. The objective of the work, therefore, was to evaluate the photochemical and phytomass aspects of pomegranate seedlings grown under irrigation water salinity and foliar nitrogen fertilization. The experiment was performed in a randomized block design, in an incomplete factorial scheme, with five levels of electrical conductivity of irrigation water - ECw (0.50, 1.15, 2.75, 4.35 and 5.00 dS m-1) and five nitrogen doses - N (0.0, 0.33, 1.15, 1.97 and 2.30 g L-1), totaling nine combinations, generated by the Central Composite Design, with four repetitions and two plants per repetition. Foliar N application at a dose of 1.37 g L-1 increased the production of leaf and root dry phytomass at 90 days after emergence. Salt stress reduced the photochemical activity and phytomass production of pomegranate seedlings, while there was a stimulus by increasing N application up to 2.3 g L-1.

Resumo A romã é uma fruteira com potencial de exploração no Nordeste brasileiro com potencial de uso como composto medicinal e na alimentação. Porém, a escassez qualitativa e quantitativa dos recursos hídricos é comum nesta região, sendo necessário o uso de águas com elevados teores de sais na agricultura irrigada. Assim, é necessário a adoção de estratégias para reduzir os efeitos deletérios do estresse salino sobre as plantas, sendo a adubação foliar nitrogenada uma alternativa promissora. Assim, o objetivo do trabalho foi avaliar os aspectos fotoquímicos e as fitomassas da romãzeira em função da salinidade da água de irrigação e adubação foliar de nitrogênio (N). O experimento foi realizado em delineamento experimental de blocos casualizados, em arranjo fatorial incompleto, com cinco níveis de condutividade elétrica da água - CEa (0,50; 1,15; 2,75; 4,35 e 5,00 dS m-1) e cinco doses de nitrogênio - N (0,0; 0,33; 1,15; 1,97 e 2,30 g L-1), totalizando nove combinações, gerados pela matrix Composto Central de Box, com quatro repetições e duas plantas por repetição. A aplicação foliar de N na dose de 1,37 g L-1, aumentou a produção de fitomassa seca de folhas e da raiz, aos 90 dias após a emergência. O estresse salino reduziu a atividade fotoquímica e a produção de fitomassa das plantas de romã, enquanto houve um estimulo pela aplicação crescente de N até 2,3 g L-1.

ABSTRACT Moringa oleifera (Lam.) is an oilseed rich in unsaturated fatty acids. The seed reserve composition can change according to environmental conditions of precipitation and temperature. Thus, this work aimed to characterize the M. oleifera seed and its vegetable oil from plants cultivated in different states of Northeast Brazil. Seeds and soil samples were collected in Bahia (BA), Ceará (CE), Paraíba (PB), and Rio Grande do Norte (RN). Regarding climate variables, RN and BA had the lowest (395 mm) and highest (880 mm) precipitation during the collection year, respectively. The size and mass of the seeds and almonds, and the characterization of the flour and the oil of the ‘moringa’ seeds were measured. The largest seeds and almonds were collected in BA and the smallest in RN. The highest protein and moisture contents were obtained in the seeds from CE. The seeds from RN had the highest oil content, unsaturated fatty acids, ashes, acidity, and saponification levels. Thus, RN presents the smallest seeds of M. oleifera with higher content of mineral salts (ashes), oil, and monounsaturated fatty acids.

RESUMO Moringa oleifera (Lam.) é uma oleaginosa rica em ácidos graxos insaturados. A composição de reserva da semente pode mudar de acordo com as condições ambientais de precipitação e temperatura. Assim, objetivou-se com este trabalho caracterizar sementes e o óleo vegetal de M. oleifera cultivado em diferentes estados do Nordeste do Brasil. As sementes e amostras de solo foram coletadas na Bahia (BA), Ceará (CE), Paraíba (PB) e Rio Grande do Norte (RN). Em relação às variáveis climáticas, RN e BA apresentaram a menor (395 mm) e a maior (880 mm) precipitação durante o ano de coleta. As sementes e amêndoas foram medidas e realizada a caracterização da farinha e do óleo de moringa. As maiores sementes e amêndoas foram coletadas na BA e as menores no RN. O maior teor de proteínas e umidade foram obtidos nas sementes do CE. As sementes do RN apresentaram o maior teor de óleo, níveis de acidez e saponificação e a maior quantidade de ácidos graxos insaturados. Assim, o RN possui as menores sementes de M. oleifera com maior teor de sais minerais, óleo e ácidos graxos monoinsaturados.

ABSTRACT Nasturtium (Tropaeolum majus) is an ornamental and medicinal plant that has edible flowers. Drought and salt stress decrease flower production and quality, including affecting sugar metabolism and ethylene production. Ethylene can accelerate the nasturtium senescence process, decreasing its postharvest quality. The use of polyamines, mainly spermine, may be a strategy for reducing the harmful effects of these stresses on the metabolism of sugars and phenolic compounds and for decreasing the production of ethylene, which accelerates senescence, in nasturtium flowers. Therefore, the objective here was to evaluate the role of spermine application on sugar and phenolic compounds and on ethylene production in nasturtium flowers grown under drought and salt stress. Two experiments were performed in isolation and at the same time in order to achieve this. Spermine down-regulated ethylene production and up-regulated the content of sugars and phenolic compounds on nasturtium flowers grown under drought and saline stress. Sugars and phenolic compounds down-regulated ethylene production in nasturtium flowers. Spermine can be used to mitigate the harmful effects of drought and salt stress on nasturtium flowers by increasing sugar and phenolic compounds and decreasing ethylene production. Tropaeolum majus quality process polyamines Therefore this downregulated down regulated upregulated up

ABSTRACT Lisianthus (Eustoma grandiflorum) is a cut flower grown due to the wide diversity of colors and longevity in the post-harvest. The leaf area measurement is fundamental in plants because the leaves are directly related to several processes such as transpiration, radiation interception and CO2 fixation that enable the plant to grow. The objective of the work was to determine an allometric equation for estimating the leaf area of lisianthus from linear dimensions. 200 leaves were collected and the leaf length (L), leaf width (W), product between length and width (LW) and real leaf area (LA) were measured. The criteria for determining the best model were the highest determination coefficient (R2), Willmott's concordance index (d), lowest Akaike information criterion (AIC), root mean square error (RMSE) and BIAS index closest to zero. The most suitable model for estimating the leaf area of lisianthus is the linear ŷ = 1.387*LW.

RESUMO: Mesosphaerum suaveolens (L.) Kuntze é uma espécie muito utilizada na medicina popular e que possui um elevado potencial aromático e terapêutico. No entanto, sua exploração em regiões semiáridas pode ser limitada em função do teor de sais na água de irrigação. O objetivo deste estudo foi avaliar o efeito do ácido salicílico (AS) como mitigador do estresse salino sobre o crescimento e trocas gasosas de M. suaveolens. O delineamento estatístico utilizado foi o de blocos casualizados, em esquema fatorial incompleto (Delineamento Composto Central), com cinco condutividades elétricas de água (CEa = 0,5, 1,45, 5,0, 8,55 e 10,0 dS m-1) e cinco doses de AS (0,0, 0,29, 1,0, 1,71 e 2,0 mM). Foram avaliados a altura de plantas, número de folhas, diâmetro do caule, área foliar, comprimento de raiz e relação altura/diâmetro do caule e trocas gasosas (condutância estomática, taxa de assimilação líquida de CO2, transpiração, eficiência instantânea e eficiência intrínseca no uso da água e de carboxilação e a temperatura foliar). A aplicação do AS na dose de 0,9 mM atenua o efeito do estresse salino sobre o número de folhas e área foliar. A aplicação de AS estimula o número de folhas e o crescimento em altura e da raiz, mas não afeta as trocas gasosas. A CEa reduz o crescimento e as trocas gasosas das plantas de M. suaveolens.

ABSTRACT: Mesosphaerum suaveolens (L.) Kuntze is a species widely used in folk medicine and has a high aromatic and therapeutic potential. However, its cultivation in semi-arid regions can be limited by salts in the irrigation water. The objective of this study was to evaluate the effect of salicylic acid (SA) as a mitigator of saline stress on the growth and gas exchange of M. suaveolens. The experimental design used was the randomized blocks in an incomplete factorial scheme (Central Composite Design), with five electrical conductivities water (ECw = 0.5, 1.45, 5.0, 8.55, and 10.0 dS m-1) and five SA doses (0.0, 0.29, 1.0, 1.71, and 2.0 mM). Plant height, number of leaves, stem diameter, leaf area, root length, and height/diameter ratio, and gas exchange (stomatal conductance, net CO2 assimilation rate, transpiration rate, instantaneous, and intrinsic water use efficiency, instantaneous carboxylation efficiency, and leaf temperature) were evaluated. The application of 0.9 mM SA attenuates the negative effect of saline stress on the number of leaves and leaf area of M. suaveolens. The application of SA stimulates the number of leaves, plant height, and root growth, but does not affect the gas exchange of M. suaveolens. ECw reduces the growth and gas exchange of M. suaveolens plants.

RESUMO Os estresses abióticos são uma das principais razões para a baixa produtividade das culturas devido aos distúrbios causados por eles. As poliaminas podem ser aplicadas para mitigar os efeitos nocivos do estresse nas plantas. A capuchinha (Tropaeolum majus L.) é uma planta ornamental, medicinal e comestível encontrada em muitos países. O objetivo deste trabalho foi avaliar o efeito da aplicação de poliaminas e estresse salino no crescimento e nas trocas gasosas foliares de T. majus. Os tratamentos para induzir o estresse salino foram os seguintes: 0 mM NaCl (sem estresse), 40 mM NaCl (estresse moderado), 80 mM NaCl (estresse severo), 40 mM NaCl + espermina (Spm), 40 mM NaCl + espermidina (Spd), NaCl 40 mM + putrescina (Put), NaCl 80 mM + Spm, NaCl 80 mM + Spd e NaCl 80 mM + Put. As poliaminas foram aplicadas semanalmente durante quatro semanas. As aplicações de Spd e Spm atenuaram os efeitos nocivos do estresse salino moderado na altura de plantas e na massa fresca das folhas. A aplicação de Spm atenuou os efeitos nocivos do estresse salino moderado no diâmetro do caule. A aplicação de Spd atenuou os efeitos nocivos do estresse salino moderado sobre o número de botões, massa fresca do caule e massa fresca total. A aplicação de Spm atenuou os efeitos nocivos do estresse salino severo na condutância estomática e na taxa de transpiração e atenuou os efeitos nocivos do estresse salino moderado na condutância estomática, fotossíntese líquida e taxa de transpiração. A aplicação de Spd atenuou os efeitos nocivos do estresse salino moderado na eficiência instantânea do uso da água e na eficiência intrínseca do uso da água. As aplicações de Spm e Spd podem atenuar os efeitos nocivos do estresse salino moderado no crescimento e nas trocas gasosas foliares de capuchinha.

ABSTRACT Abiotic stresses are one of the major reasons for low crop productivity owing to the disturbances caused by them. Polyamines can be applied to mitigate the harmful effects of stress in plants. Nasturtium (Tropaeolum majus L.) is an ornamental, medicinal, and edible plant that is found in many countries. The objective of this work was to evaluate the effect of polyamines application and salt stress on the growth and leaf gas exchange of T. majus. The treatments to induce salt stress were as follows: 0 mM NaCl (no stress), 40 mM NaCl (moderate stress), 80 mM NaCl (severe stress), 40 mM NaCl + spermine (Spm), 40 mM NaCl + spermidine (Spd), 40 mM NaCl + putrescine (Put), 80 mM NaCl + Spm, 80 mM NaCl + Spd, and 80 mM NaCl + Put. Polyamines were applied every week for four weeks. The applications of Spd and Spm attenuated the harmful effects of moderate salt stress on plant height and leaf fresh mass. The application of Spm attenuated the harmful effects of moderate salt stress on stem diameter. The application of Spd attenuated the harmful effects of moderate salt stress on the number of buds, the stem fresh mass, and total fresh mass. The application of Spm attenuated the harmful effects of severe salt stress on stomatal conductance and transpiration rate and attenuated the harmful effects of moderate salt stress on stomatal conductance, net photosynthesis, and transpiration. The application of Spd attenuated the harmful effects of moderate salt stress on instantaneous water use efficiency and intrinsic water use efficiency. The applications of Spm and Spd application can attenuated the harmful effects of moderate salt stress on the growth and leaf gas exchange of nasturtium.

Abstract This study evaluate the effect of drought and heat stress on the quality of C. spectabilis seeds. A completely randomized design in a 4×4 factorial scheme, referring to four osmotic potentials based on Polyethylene glycol (PEG 6000 = 0.0, -0.2, -0.4 and -0.8 MPa) and four temperatures (25, 30 and 35 ºC constant and alternating between 25-35 ºC), with four replications of 50 seeds per plot was used. The germination percentage, first count germination, germination speed index, average germination time, average germination speed, length and dry mass of the root, shoot and seedlings were evaluated. C. spectabilis is sensitive to drought stress during germination and seedling establishment, tolerating up to -0.2 MPa. The physiological quality of seeds is reduced with the decrease of osmotic potentials. The temperature range between 25 and 30 ºC are the one that provide better conditions for the germination of the seeds of this species.

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.

RESUMEN Aedes aegypti L. es el mosquito que transmite el virus de la fiebre amarilla, el dengue, el zika y el chikungunya. La prevención y el control de tales enfermedades generalmente dependen del uso de productos químicos, que causan daños al hombre y al medio ambiente. Por ello, los aceites vegetales con acción larvicida se utilizan como alternativa para controlar este insecto. El objetivo de este trabajo fue evaluar el potencial larvicida de aceites vegetales de Caryocar coriaceum, Mauritia flexuosa, Carapa guianensis, Copaifera langsdorffii, Ricinus communis y Cocos nucifera contra A. aegypti. El experimento se dividió en dos bioensayos. En el primero se realizó un diseño completamente al azar con siete tratamientos (seis aceites vegetales a 500 ppm y un control y cuatro repeticiones). Se evaluó el número de larvas muertas a las 24, 48, 72, 96 y 120 h de exposición. En el segundo bioensayo, se utilizaron los aceites vegetales más eficientes (C. coriaceum y M. flexuosa) en concentraciones 0, 500, 1000, 1500, 2000 y 2500 ppm, con cuatro repeticiones. El número de larvas muertas se evaluó según el primer bioensayo. Todos los aceites utilizados tienen efecto larvicida sobre larvas de A. aegypti de tercer estadio, con mayor eficacia a las 120 h de exposición. Los aceites de C. coriaceum y M. flexuosa mostraron mejor eficacia en el control de larvas, siendo la dosis de 2500 ppm la más recomendada. El LD10, LD50 y LD90 del aceite de M. flexuosa recomendado para controlar larvas son 234, 648 y 1794 ppm, respectivamente.

ABSTRACT Aedes aegyptiL. is the mosquito vector of yellow fever, dengue, zika, and chikungunya viruses. The prevention and control of such diseases usually rely on the use of chemicals, that can cause harm to human health and the environment. Vegetable oils with larvicidal activity are used as an alternative tool to control this insect. This study aimed to evaluate the larvicidal activity of vegetable oils fromCaryocar coriaceum,Mauritia fIexuosa,Carapa guianensis, Copaifera langsdorffii, Ricinus communisandCocos nuciferaagainstA. aegypti larvae. The experiment was divided into two bioassays. In the first, a completely randomized design was used with seven treatments (six vegetable oils at 500 ppm and one control with four replications). The number of dead larvae was evaluated 24, 48, 72, 96, and 120 h after exposure. In the second bioassay, the most efficient vegetable oils from the first bioassay (C. coriaceumandM. flexuosa) were used at the concentrations of 0, 500, 1000, 1500, 2000, and 2500 ppm, with four replications. The number of dead larvae was evaluated according to the first bioassay. All oils used had larvicidal activity on third-instar stage larvae ofA. aegypti, with greater efficiency 120 h after exposure. The oils ofC. coriaceumandM. flexuosaat 2500 ppm had the best efficacy in the larvae control. The LD10, LD50, and LD90 ofM. flexuosaoil recommended for controlling larvae are 234, 648, and 1794 ppm, respectively.

RESUMO Platycodon grandiflorus é uma espécie ornamental que pode ser comercializada como flor de vaso; porém, apresenta ramos florais frágeis e pendentes. Reguladores de crescimento, como o paclobutrazol, são compostos que reduzem o alongamento do caule, permitindo a produção de plantas com formação mais compacta. Objetivou-se avaliar os efeitos de paclobutrazol no crescimento de platycodon, em casa-de-vegetação. O delineamento experimental foi em blocos inteiramente casualizados, em esquema fatorial 4 × 5, com quatro repetições. Os tratamentos consistiram de quatro variedades de platycodon ‘Astra Semi-Double’ (Blue, Lavender, Pink e White) e cinco doses de paclobutrazol (0; 1,25; 2,5; 3,75; e 5,0 mg vaso-1). A aplicação de paclobutrazol não afetou o diâmetro do caule, número de folhas, dias até a antese, número de flores ou botões florais e diâmetro da flor. O comprimento da parte aérea, área foliar e massa seca da parte aérea decresceram com o aumento da dose do regulador de crescimento. Lavender apresentou os maiores valores de comprimento da parte aérea, número de folhas, área foliar e massa seca da parte aérea. Pink teve a antese mais precoce, seguida de Blue e White, enquanto Lavender teve a antese mais tardia. A dose de 3,75 mg vaso-1 de paclobutrazol eficientemente controlou o crescimento e melhorou a qualidade visual de todas as variedades de platycodon.

ABSTRACT Platycodon grandiflorus is an ornamental species that can be marketed as a potted flower; however, it has fragile and bending floral stems. Plant growth regulators, such as paclobutrazol, are compounds that reduce stem elongation, enabling the production of plants with a more compact formation. This study aimed to evaluate the effects of paclobutrazol on platycodon growth, in a greenhouse. A completely randomized blocks experimental design was used in a 4 × 5 factorial scheme, with four replicates. The treatments consisted of four varieties of ‘Astra Semi-Double’ platycodon (Blue, Lavender, Pink and White) and five paclobutrazol doses (0, 1.25, 2.5, 3.75 and 5.0 mg pot-1). The paclobutrazol application did not affect the stem diameter, number of leaves, days until anthesis, number of flowers or flower buds, and flower diameter. The shoot length, leaf area and shoot dry mass decreased with higher doses of the growth regulator. Lavender showed the highest values for shoot length, number of leaves, leaf area and shoot dry mass. Pink had the earliest anthesis, followed by Blue and White, whereas Lavender had the latest anthesis. The dose of 3.75 mg pot-1 of paclobutrazol efficiently controlled the growth and improved the visual quality of all the platycodon varieties.

RESUMO A salinidade é um dos problemas que limitam o desenvolvimento das plantas, sendo as fases de germinação, crescimento e estabelecimento inicial as mais sensíveis ao estresse salino. Erythrina velutina, popularmente conhecida no Brasil como “mulungu”, é uma espécie nativa do bioma Caatinga, que cresce em condições de solo rico em sais. Os danos causados pela salinidade à qualidade de suas sementes e a utilização de técnicas que mitiguem esses efeitos são pouco conhecidos. Assim, o objetivo deste trabalho foi avaliar o ácido salicílico como mitigador do estresse salino na qualidade fisiológica de sementes de mulungu. A qualidade de dois lotes de sementes de dois estados brasileiros (L1: Mossoró, Rio Grande do Norte, e L2: Pentencostes, Ceará) foi avaliada. O delineamento inteiramente casualizado em esquema fatorial 2 (embebição de sementes com ácido salicílico (SA) - água destilada e 1,0 mM SA) × 4 (condutividade elétrica da água de irrigação - ECw - 0,0, 3,0, 6,0 e 9,0 dS m-1) com quatro repetições de 50 sementes cada foi usado. O estresse salino reduz a qualidade das sementes e mudas de mulungu. SA aumenta o vigor das sementes, promovendo melhorias na germinação em condições salinas.

ABSTRACT Salinity is one of the problems that limit plant development, with the germination, growth, and initial establishment stages being the most sensitive to saline stress. Erythrina velutina, popularly known as “mulungu” in Brazil, is a species native to the Caatinga biome, which grows in conditions of soil rich in salts. The damage caused by salinity to the quality of its seeds and the use of techniques that mitigate such effects are little known. Thus, this work aimed to evaluate salicylic acid as a mitigator of saline stress in the physiological quality of mulungu seeds. The quality of two seed lots from two Brazilian states (L1: Mossoró, Rio Grande do Norte, and L2: Pentencostes, Ceará) was evaluated. A completely randomized design in a 2 (seed soaking with salicylic acid (SA) - distilled water and 1.0 mM SA) × 4 (electrical conductivity of irrigation water - ECw - 0.0, 3.0, 6.0 and 9.0 dS m-1) factorial scheme with four replications of 50 seeds each was used. Saline stress reduces the quality of mulungu seeds and seedlings. SA increases the vigor of the seeds, promoting improvements in germination under saline conditions.

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.

RESUMEN El calabacín (Cucurbita pepo L.) presenta un gran potencial económico y productivo en la región semiárida de Brasil, debido a su amplia aceptación por los consumidores y su rápido rendimiento financiero., El proceso de asimilación de nitrato (NO3 -) en plantas C3 como el calabacín estaría relacionado en parte con la fotorrespiración, y el Si acumulado cerca de los estomas reduce la tasa de transpiración, haciendo que el ciclo de fotosíntesis sea más eficiente. Por lo tanto, el objetivo de este estudio fue evaluar la interacción entre el nitrógeno y la fertilización con silicio en el crecimiento, el índice de clorofila y la fluorescencia de la clorofila a en plantas de calabacín. Los tratamientos se distribuyeron en un esquema de parcelas divididas en un diseño de bloques al azar con tres repeticiones. La parcela se formó por niveles de silicio (0 y 6 g/planta) y las subparcelas constituidas por cinco niveles de nitrógeno (30, 60, 90, 120 y 150 kg ha-1), totalizando 30 parcelas experimentales. Se evaluaron masas de hojas, tallos y secas totales, clorofila a, clorofila b, clorofila total, clorofila a/b y fluorescencia de la clorofila a. Las mayores producciones de materia seca de calabacín se obtuvieron en tratamientos sin Si. La aplicación de Si y N juntos influye positivamente en la proporción de clorofila a/b de las plantas de calabacín. La interacción entre Si y N influye positivamente en la fluorescencia máxima, la fluorescencia variable y el rendimiento cuántico del fotosistema II de plantas de calabacín.

ABSTRACT Zucchini (Cucúrbita pepo L.) has a great economic and productive potential in the semi-arid region of Brazil, due to the wide acceptance by consumers and quick financial return. The nitrate (NO3 -) assimilation process in C3 plants such as zucchini is related to photorespiration, and Si accumulated near the stomata reduces the transpiration rate, making the photosynthesis cycle more efficient. The objective of this study was to evaluate the interaction between nitrogen and silicon fertilization on growth, chlorophyll index, and chlorophyll a fluorescence of zucchini plants. The treatments were distributed in a split-plot scheme in a randomized block design with three replicates. The plot was arranged by silicon levels (0 and 6 g/plant) and the subplots constituted by five nitrogen levels (30, 60, 90, 120 and 150 kg ha-1). Leaf, stem and total dry masses, chlorophyll a, chlorophyll b, total chlorophyll, chlorophyll a/b ratio and chlorophyll a fluorescence were evaluated. The highest dry matter productions in zucchini were obtained in treatments without Si. Si and N application together positively influences the chlorophyll a/b ratio of zucchini plants. The interaction between Si and N positively influences the maximum fluorescence, variable fluorescence and quantum yield of photosystem II of zucchini plants.

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.