Does molybdenum and cobalt foliar spray mitigate nitrate starvation and ammonium deprivation stress?

Abstract

Knowledge about the nutritional balance at the initial phenological stage is mandatory to overcome limitations on nutritional availabilities required by the plant species. However, little is elucidated about nitrate (NO3-) and ammonium (NH4+) deprivation stress. Our hypothesis tested is that there are benefits of the foliar application (spray) of molybdenum (Mo) and cobalt (Co) under different availabilities (ionic strength, IS) from the presence of nitric sources (CaNO32-) and absence of ammonium (NH4H2PO4) in root application (hydroponic cultivation) at the initial phenological growth stage. Nutrient supply was carried out with a nutrient solution, which is deprived of NH4+. Treatments were 25%, 50%, and 100% IS, supplied via hydroponic cultivation, combined with the absence/presence of Co/Mo spray. Plants were randomly distributed into 17 blocks (replicates) with 6 treatments conducted in a factorial scheme and data were analyzed by ANOVA and ANCOVA. We observed that Co/Mo spray diminished plant growth discrepancies between treatments at different IS’s. In addition, contents of photosynthetic pigments were higher at 25% IS without Co/Mo spray. Thus, we concluded that Mo and Co spray can alleviate NO3- starvation/NH4+ deprivation stress during the initial growth phenological stages of yellow passion fruits.