ABSTRACT. Cowpea planting season is crucial for high yield and should comprise the period of the year that warrants the best climatic conditions for cowpea cultivation. Thus, the objective of this study was to evaluate the influence of water availability and temperature on the performance of cowpea cultivars. A greenhouse experiment was conducted using a 4 × 2 × 5 factorial arrangement, with four replications. Factors included four levels of soil moisture (25, 50, 75, and 100% of water holding capacity), two growing seasons (mild and hot), and five cowpea cultivars (Carijó, Itaim, Pujante, Rouxinol, and Tapahium). The number of pods and seeds per plant, seed production, water use efficiency, shoot dry mass, root dry mass, and physiological parameters were evaluated. Seed production was higher during the mild season than during the hot season and increased linearly with increasing soil water availability. Photosynthetic activity and transpiration were higher during the hot season than during the mild season, with their reduction under a water availability of 25% regardless of the growing season. Total chlorophyll content decreased with excess water. Regardless of water availability, temperature was the most limiting climatic factor for cowpea performance. Cultivars Carijó, Itaim, and Tapahium exhibited a lower reduction in productive potential when grown in the hot season.

RESUMO Considerando-se que mudanças nos parâmetros climáticos interferem diretamente na produtividade das culturas, objetivou-se avaliar o impacto de mudanças nas concentrações de dióxido de carbono, temperatura e disponibilidade hídrica do solo na produção, eficiência do uso de água e qualidade de cebola (Allium cepa L. cv. IPA 11). Foram avaliados quatro níveis de disponibilidade de água no solo (40, 60, 80 e 100 %) e duas concentrações de CO2 atmosférico (770 e 390 ppm), em três experimentos com diferentes regimes de temperatura (18-24-30, 22-28-34 e 26-32-38 ºC), em câmera de crescimento Fitotron. Também foram avaliados a eficiência do uso de água, diâmetro e peso dos bulbos, massa seca da parte aérea, firmeza da polpa, teor de sólidos solúveis, pH e acidez titulável. O aumento da temperatura reduz a produção, e maior disponibilidade de água no solo eleva a produção de bulbos de cebola IPA 11. O regime de temperatura de 18-24-30 ºC e a disponibilidade hídrica de 76,72 % proporcionam melhor eficiência no uso de água para a cultura da cebola.

ABSTRACT Considering that changes in climatic parameters directly interfere in crop yields, this study aimed to evaluate the impact of changes in carbon dioxide concentrations, temperature and soil water availability on production, water-use efficiency and onion (Allium cepa L. cv. IPA 11) quality. Four levels of soil water availability (40, 60, 80 and 100 %) and two concentrations of atmospheric CO2 (770 and 390 ppm) were evaluated in three experiments with different temperature regimes (18-24-30, 22-28-34 and 26-32-38 ºC), in Phytotron growth chambers. The water-use efficiency, bulb diameter and weight, shoot dry weight, pulp frmness, soluble solids content, pH and titratable acidity were also evaluated. The increase in temperature reduces the production, and a higher soil water availability increases the production of IPA 11 onion bulbs. The temperature regime of 18-24-30 ºC and the water availability of 76.72 % provide the best water-use efficiency for the onion crop.

RESUMO O déficit hídrico e as altas temperaturas são os fatores abióticos que mais restringem o crescimento e desenvolvimento das plantas. Entretanto, seus efeitos dependem da fase de desenvolvimento da cultura, da duração e da intensidade do estresse. Com isso, objetivou-se com esse trabalho, avaliar o desenvolvimento do feijão-caupi submetido à restrição hídrica em diferentes fases fenológicas e ao aumento da temperatura do ar. O experimento foi conduzido com a cultivar Carijó, em câmaras de crescimento, em arranjo fatorial de 4x3x2, sendo as disponibilidades hídricas (25, 50, 75, and 100%,) as fases fenológicas (vegetativa, floração e enchimento das vagens) e os regimes de temperatura (T°1: 20-26-33 °C e T°2: 24.8-30.8-37.8 °C) , respectivamente. A redução da disponibilidade hídrica nas fases vegetativa e na floração ocasionou queda na produção de sementes. A porcentagem de flores abortadas foi maior para as plantas mantidas no regime de temperatura com um aumento de 4.8 °C, com consequentemente, redução na produção de sementes. O aumento da disponibilidade hídrica, favoreceu a produção de massa seca da parte aérea e da raiz. O aumento de 4,8 °C não afetou o peso da massa seca da parte aérea e das raízes, porém, reduziu cerca de 83% da eficiência de uso da água pela planta. Verificou-se as maiores atividades enzimáticas da CAT GPX e SOD nas plantas submetidas ao regime de temperatura de com um aumento de 4.8 °C. Apenas a APX apresentou menor atividade enzimática com o aumento da temperatura. A cv. Carijó apresenta maior sensibilidade ao aumento de 4,8 °C na temperatura do ar do que aos déficits hídricos.

ABSTRACT Water deficit and high temperatures are abiotic factors that most limit plant growth and development. However, its effects depend on crop development stage and on stress duration and intensity. Thus, the objective of was to evaluate the development of cowpea subjected to water restriction in different phenological stages and to increase in air temperature. The experiment was conducted with the cultivar ‘Carijó’, in growth chambers, in a 4 x 3 x 2 factorial arrangement, corresponding to levels of water availability (25, 50, 75, and 100%,), phenological stages (vegetative, flowering and pod filling) and temperature regimes (T°1: 20-26-33 °C e T°2: 24.8-30.8-37.8 °C), respectively. Reduction of water availability in the vegetative and flowering stages caused decrease in grain production. The percentage of aborted flowers was higher in plants maintained under an increased temperature of +4.8 °C, with consequent reduction in grain production. Higher water availability values favored shoot and root dry mass production. Increase of 4.8 °C did not affect shoot and root dry mass but reduced water use efficiency by about 83%. The highest enzymatic activities of CAT, GPX and SOD were found in plants subjected to the temperature of +4.8 °C. Only APX showed lower enzymatic activity with increasing temperature. The cv. ‘Carijó’ is more sensitive to the 4.8 °C increase in air temperature than to water deficits.

RESUMEN La temperatura es uno de los elementos climáticos que afectan la mayoría del proceso de germinación y el desarrollo de las plántulas. Por lo tanto, el objetivo de este estudio fue evaluar la germinación y el desarrollo de plántulas de los cultivares de frijol caupí a temperatura creciente. Para este propósito, las semillas de los cultivares Acauã, Carijó, Guariba, Gurguéia, Itaim, Juruá, Pajeú, Potengi, Pujante, Nightingale, Tapahium y Tumucumaque se mantuvieron en la cámara de germinación a temperaturas de 20, 25, 30, 35 y 40°C, con fotoperiodo de 12 horas. Las semillas de frijol caupí tienen un rendimiento óptimo de germinación y desarrollo de plántulas a temperaturas en el rango de 30.49 - 35.48°C. Los cultivares presentaron un porcentaje de germinación superior al 91% por debajo de 40°C, sin embargo, no se observó formación de plántulas normales. La temperatura de 20°C proporcionó una germinación superior al 96%, pero con un período más largo para germinar. El rango de temperatura entre 30 y 35°C favoreció el índice de velocidad de germinación, el tiempo promedio y la velocidad de germinación de la semilla, con temperaturas óptimas que varían entre los cultivares. La tasa más alta de plántulas normales se observó a temperaturas entre 25 y 35°C.

ABSTRACT Temperature is one of the climatic elements that affect germination and seedling development. Thus, the objective of this study was to evaluate germination and seedling development in cowpea cultivars under increasing temperatures. Seeds from the cultivars Acauã, Carijó, Guariba, Gurguéia, Itaim, Juruá, Pajeú, Potengi, Pujante, Rouxinol, Tapahium, and Tumucumaque were kept in a germination chamber at temperatures of 20, 25, 30, 35 and 40°C, with a photoperiod of 12 h. Cowpea seeds have optimal germination performance and seedling development at temperatures in the range of 30.49 - 35.48°C. The cultivars presented a germination percentage above 91% under 40°C; however, the seedlings were abnormal. The temperature 20°C provided germination above 96% but required a longer period to germinate. The temperature range between 30 - 35°C favored the germination speed index, an average time, and seed germination speed, with optimum temperatures varying between the cultivars. The highest normal seedling rate was observed at temperatures between 25 and 35°C.

RESUMO O aumento dos níveis de CO2 e da temperatura podem afetar o crescimento e a produtividade das plantas. Objetivou-se avaliar o impacto do aumento da concentração de dióxido de carbono e da temperatura no desenvolvimento de cultivares de feijão-caupi. O experimento foi conduzido em câmaras de crescimento, com controle de CO2 e temperatura. O delineamento experimental foi inteiramente casualizado, em arranjo fatorial 4 x 3 x 2 [cultivar x temperatura (diurna/noturna) x CO2], com três repetições. Foi avaliada a duração das fases vegetativa e reprodutiva do feijão-caupi e, ao final do experimento, quantificado o número de vagens por planta, número de grãos por vagem, peso das sementes, peso da matéria fresca e seca da parte aérea. A temperatura afeta o desenvolvimento das cultivares de feijão-caupi, sendo que as temperaturas de 29 ºC (dia)/23 ºC (noite) proporcionam sementes com maior peso. O aumento de CO2 incrementa o número de vagens e de sementes e o peso das sementes. A cultivar BRS Tapaihum apresentou maior número de vagens e de sementes e peso de sementes. Além disso, as temperaturas de 32 ºC (dia)/29 ºC (noite) provocam maior abortamento de flores nas cultivares BRS Pujante e BRS Tapaihum.

ABSTRACT The increase of CO2 concentrations and temperatures may affect the plant development and production. This study aimed to evaluate the impact of the increased temperature and carbon dioxide concentration on the development of cowpea cultivars. The experiment was conducted in growth chambers, with control of CO2 and temperature. A completely randomized design was carried out, in a 4 x 3 x 2 factorial arrangement [cultivar x temperature (day/night) x CO2], with three replicates. The duration of the cowpea vegetative and reproductive phases was evaluated and, at the end of the experiment, the number of pods per plant, number of grains per pod, seed weight, shoot fresh and dry matter weight were quantified. Temperature affects the development of cowpea cultivars, and the temperatures of 29 ºC (day)/23 ºC (night) lead to a higher seed weight. The increase of CO2 leads to a higher number of pods and seeds and seed weight. The BRS Tapaihum cultivar presented the highest number of pods and seeds and seed weight. In addition, the temperatures of 32 ºC (day)/29 ºC (night) lead to a greater flower abortion in the BRS Pujante and BRS Tapaihum cultivars.