ABSTRACT
This research was carried out aiming at evaluating the effects of nitrate and ammonium ions on nutrient accumulation, biochemical components and yield of Italian zucchini (cv. Caserta) grown in a hydroponic system under salt stress conditions. The experiment was carried out in a greenhouse utilizing an experimental design in randomized blocks, arranged in a 2 x 5 factorial scheme, with 4 replications. The treatments consisted of two forms of nitrogen (nitrate - NO3- and ammonium - NH4+) and 5 electrical conductivity levels of irrigation water (ECw) (0.5, 2.0, 3.5, 5.0 and 6.5 dS m-1). The analysis of the results indicated that supply of N exclusively in NH4+ form promotes greater damage to the leaf membrane and reduction in accumulation of macronutrients and higher Na+/K+, Na+/Ca++ and Na+/Mg++ ratios in the shoots of zucchini plants. Electrical conductivity of irrigation water above 2.0 dS m-¹ reduces the accumulation of nutrients in shoot and yield of Italian zucchini plant. The toxicity of NH4+ under Italian zucchini plants overlap the toxicity of the salinity, since its fertilization exclusively with this form of nitrogen inhibits its production, being the NO3- form the most suitable for the cultivation of the species.
Este trabalho foi desenvolvido com o objetivo de avaliar os efeitos dos íons nitrato e amônio sobre o acúmulo de nutrientes e produção da abobrinha italiana (cv. Caserta) cultivada em sistema hidropônico sob estrese salino. O experimento foi conduzido em casa de vegetação utilizando o delineamento experimental em blocos casualizados, arranjados em esquema fatorial 2 x 5, com 4 repetições. Os tratamentos foram constituídos de duas formas de nitrogênio (nitrato - NO3- e amônio - NH4+) e cinco níveis de condutividade elétrica da água de irrigação (CEa) (0,5; 2,0; 3,5; 5,0 e 6,5 dS m-¹). As análises dos resultados indicaram que suprimento de N exclusivamente em forma de NH4+ promove maiores danos na membrana foliar e redução no acúmulo de macronutrientes e maiores relações Na+/K+, Na+/Ca++ e Na+/Mg++ na parte aérea das plantas de abobrinha. A irrigação com água a cima de 2,0 dS m-¹ reduz o acúmulo de nutrientes na parte aérea das plantas e a produção de abobrinha. A toxicidade do NH4+ sob abobrinha italiana sobrepõe-se à toxicidade da salinidade, pois a fertilização exclusiva com esta forma de nitrogênio inibe sua produção, sendo a forma NO3- a mais adequada para o cultivo da espécie.
Subject(s)
Cucurbita pepo , Salt Stress , Hydroponics , Ammonium Hydroxide/administration & dosage , Ammonium Hydroxide/adverse effects , Ammonium Hydroxide/toxicity , Homeostasis , Nitrogen/administration & dosage , Nitrogen/adverse effectsABSTRACT
The search for new instruments to promote an appropriate cervical preparation has led to the development of new rotary instruments such as TripleGates. However, to the best of the authors' knowledge, there is no study evaluating TripleGates effect on the “risk zone” of mandibular molars. Objectives : The aim of this study was to evaluate the effects of a crown-down sequence of Gates-Glidden and TripleGates burs on the remaining cervical dentin thickness and the total amount of dentin removed from the root canals during the instrumentation by using cone beam computed tomography. The number of separated instruments was also evaluated. Material and Methods : Mesial roots of 40 mandibular first molars were divided into 2 equal groups: crown-down sequence of Gates-Glidden (#3, #2, #1) and TripleGates burs. Cervical dentin thickness and canal area were measured before and after instrumentation by using cone beam computed tomography and image analysis software. Student’s t-test was used to determine significant differences at p<0.05. Results : No significant differences (p>0.05) were observed between the instruments, regarding the root canal area and dentin wall thickness. Conclusion : Both tested instruments used for cervical preparation were safe to be used in the mesial root canal of mandibular molars. .