ABSTRACT Safflower crops is usually intended for production of seeds to oil extraction. The objective of this work was to evaluate the chlorophyll index, biometric characteristics and water use efficiency of safflower plants grown under different nitrogen and potassium rates and controlled soil water tension. The experiment was conducted in a greenhouse, in pots containing 8 dm3 of a Oxisol. A complete randomized block experimental design in a 5x5 factorial arrangement was used, with four replications, consisting of five nitrogen rates (0, 60, 120, 180 and 240 mg dm-3) and five potassium rates (0, 50, 100, 150 and 200 mg dm-3). The safflower number of leaves, stem diameter, chlorophyll index, number of capitula, shoot, root and total dry weights, water consumption and water use efficiency were evaluated. Data were subjected to analysis of variance (F test) at 5% of probability and to polynomial regression. The nitrogen and potassium fertilization, as independent factors, affected the safflower plants. The chlorophyll index, biometric characteristics and water use efficiency of safflower showed better responses under nitrogen rates of 82 to 168 mg dm-3. The responses of chlorophyll index, biometric characteristics and water use efficiency of safflower increased 10 to 60% with potassium fertilization. | RESUMO O cártamo destina-se à produção de grãos para a obtenção de óleo vegetal. Objetivou-se avaliar o índice de clorofila, as características biométricas e a eficiência no uso da água de plantas de cártamo sob doses de nitrogênio e potássio. O experimento foi conduzido em casa de vegetação, em vasos contendo 8 dm3 de um Latossolo Vermelho. O delineamento experimental foi blocos casualizados, com esquema fatorial 5x5 correspondente a cinco doses de nitrogênio (0, 60, 120, 180 e 240 mg dm-3) e cinco doses de potássio (0, 50, 100, 150 e 200 mg dm-3), com quatro repetições. Avaliou-se o número de folhas, diâmetro de caule, índice de clorofila, número de capítulos, massa seca da parte aérea, massa seca de raízes, massa seca total, consumo de água e eficiência no uso da água. Os dados foram submetidos a 5% de probabilidade de erro a análise de variância pelo teste F e regressão polinomial. O índice de clorofila, as características biométricas e a eficiência no uso da água das plantas de cártamo apresentaram melhores respostas nas doses de nitrogênio entre 82 a 168 mg dm-3. A adubação potássica nas plantas de cártamo proporcionou respostas crescentes com incrementos de 10 a 60% para o índice de clorofila, nas características biométricas e na eficiência de uso da água. As respostas a adubação com nitrogênio e potássio no cártamo ocorrem com efeito isolado.

ABSTRACT Watermelon has great economic relevance, but edaphoclimatic factors and inadequate management have favored the salinization of the water used for irrigation, which is a limiting factor for the growth and production of the crop. However, it is considered that the use of growth regulators belonging to the group of cytokinins and auxins may contribute to the development and yield of crops, even under adverse conditions such as salinity. Thus, the objective was to evaluate the influence of cytokinin and auxin proportions on the growth and quality of watermelon irrigated with saline water. The experimental design was completely randomized, with four replicates and 5 x 2 factorial, referring to five proportions of growth regulators (0/100; 25/75; 50/50; 75/25 and 100/0%) corresponding to concentrations of 1.0 and 10.0 mg L−1 of forchlorfenuron (CPPU)/ indoleacetic acid (IAA), and two salinity levels, one composed of water without adding salt (0.3 dS m-1) and the other with 2.0 dS m−1 electrical conductivity. The proportions of cytokinin and auxin influenced the growth and quality of watermelon subjected to salinity in irrigation water. The 25/75% (CPPU/IAA) proportion favored smaller decreases in leaf area and total dry mass under a saline condition of 2.0 dS m−1. For fresh and dry fruit mass, the 75/25% (CPPU/IAA) proportion favored smaller reductions. Fruit firmness and soluble solids were favored by the proportions 25/75 and 50/50% (CPPU/IAA) at EC of 2.0 dS m−1. Acidity was only influenced by the proportion of 50/50% (CPPU/IAA) between the electrical conductivity levels.