NH4+/NO3- RATIO IN THE PRODUCTION OF BIOMASS AND THE NUTRITIONAL CONTENT OF Portulaca oleracea L.

Abstract

The plants absorb N as ammonium (NH4 +) and as nitrate (NO3 -), but the ammoniacal form favors the initial vegetative development of the plant in some species. The objective this study was to evaluate the genotypes of San Gregorio (V1 ) and Americana (V2 ) purslane (Portulaca oleracea L.), originally from Xochimilco, Mexico City, in hydroponics, with the NH4 +/NO3 - : 0/100, 25/75, 50/50 and 100/0 ratios. The evaluation included: plant height, number of leaves and branches in time, stem diameter, chlorophyll content (SPAD), fresh and dry biomass, and concentration of NO3 -, N, P, K, Ca and Mg of the shoot at the harvest. The 25/75 ratio of NH4 +/NO3 - increased plant height, number of leaves and branches and stem diameter in both genotypes, with the exception of the number of leaves in V1 , in which the 0/100 ratio increased it. This last relation favored the higher production of fresh and dry biomass of the shoot, and water content in the V2 genotype, with estimated percentages of 9.0, 8.0 and 6.0% of NH4 +. The presence of NH4 + in the solution decreased the concentration of NO3 -, K, Ca and Mg in the shoot, with slightly lower values in V1 , and increased that of N and P.