Physiological aspects and production of coriander using nutrient solutions prepared in different brackish waters /Aspectos fisiológicos e produção do coentro sob soluções nutritivas preparadas em diferentes águas salobras

HIGHLIGHTS: Differences caused by cationic natures are even more evident than an increase in concentration up to a certain threshold. The prevalence of [Na.sup.+] in water caused less damage to the photosynthetic apparatus than the prevalence of [Ca.sup.2+]or [Mg.sup.2+]. There is no influence of the cationic nature at high levels of salt concentration in the nutrient solution. The analysis of chlorophyll fluorescence is one of many ways to quantify the salt damage to photosynthetic performance and crop production. Thus, the present study aimed to evaluate the photochemical efficiency and production of coriander, cultivar 'Verdão', as a function of the electrical conductivity levels of the nutrient solution and the cationic nature. The experimental design was in randomized blocks, in a 4 * 3 factorial scheme, with four replicates. The treatments consisted of four electrical conductivities of the nutrient solutions (ECns = 1.6, 3.2, 4.8, and 6.4 dS [m.sup.-1]) and three kinds of water of different cationic natures ([Na.sup.+]; [Ca.sup.2+]; [Mg.sup.2+]), which were prepared with the dissolution of different salts - NaCl, Ca[Cl.sub.2].2[H.sub.2]O, and Mg[Cl.sub.2].6[H.sub.2]O in supply water (ECw = 0.12 dS [m.sup.-1]), that is, three predominant cationic natures. The study was carried out in a greenhouse between November and December 2019 at the Fertigation and Salinity Laboratory of the Agricultural Engineering Department of the Universidade Federal Rural de Pernambuco. It was found that the increase in the electrical conductivity of the nutrient solution affected reaction centers, photochemical activity, and carboxylation efficiency and resulted in reductions in stomatal conductance, [CO.sub.2] assimilation rate, and therefore, in the biomass production of coriander. Different cationic prevalence in water causes differences in the intensity of salt damage, especially with increasing concentration. Key words: Coriandrum sativum L., gas exchange, chlorophyll a fluorescence A análise da fluorescência da clorofila é uma das muitas formas de quantificar o dano salino no desempenho fotossintético e na produção agrícola. Assim, o presente estudo teve como objetivo avaliar a eficiência fotoquímica e a produção do coentro, cultivar Verdão em função dos níveis de condutividades elétricas da solução nutritiva e da natureza catiônica. O delineamento experimental foi em blocos ao acaso, em esquema fatorial 4 * 3, com quatro repetições. Os tratamentos consistiram na expo