A aplicação foliar de Mo e Co atenua o desbalanço de N em maracujazeiro?

Abstract

Knowledge about the nutritional balance at initial phenological stage is mandatory to circumvent limitations on the nutritional availabilities required by the plant species. However, little is elucidated to passion fruit [Passiflora edulis Sims. f. flavicarpa Degener] about nitrate (NO3-) and ammonium (NH4+) deprivation stress to initial growth phenological stages. Our hypothesis tested the benefits of foliar application (spray) of molybdenum (Mo) and cobalt (Co) under different availability (N %) from a single source of nitrogen (NO3-) in the contents of photosynthetic pigments and plant growth during the initial phenological stage of development. The essential mineral elements were supplied with the Hoagland and Arnon nº01 nutrient solution, which is deprived of NH4+. The treatments employed were low, moderate and high supplies of mineral elements (25%, 50% and 100% N) combined with the absence / presence of Co and Mo spray. The experiment was conducted in a factorial scheme with a completely randomized design and the data of growth and plant production (dry matter content and photosynthetic pigments) were analyzed by ANOVA and ANCOVA, respectively. Plant growth measures in response to treatments were studied using the ‘Scott-Knott’ procedure, and significant effects and interactions were explored by average post hoc comparisons (Tukey test). From the results, we observed that the spray of Co and Mo reduced the discrepancies between the plant growth in different availability of N. In addition, we verified that the content of photosynthetic pigments was higher with low supply of nutrients (25% N) without Co and Mo spray, which enables us to reject our null hypothesis and accept the alternative hypothesis. Thus, we conclude that the combined foliar application of Mo and Co in different availability of N attenuated plant stress due to NO3- deficiency and NH4+ deprivation during the early stage of vegetative development of young plants of P. edulis in nursery.