This study intended to evaluate the contribution of the preformed roots of pineapple micropropagated seedlings cultivar Vitoria on plant growth and nitrogen (N) absorption in the first months of growth. Micropropagated seedlings stayed 75 days in a substrate in greenhouse, when they were transplanted to pots with 5 kg of soil. An incomplete factorial design with five replicates was applied, with three treatments of root pruning (without pruning, half pruning and total pruning), four times of N application (at transplanting, 30, 60 and 90 days after transplant - DAT), and four dates of plant harvest (30, 60, 90 and 120 DAT). In the samplings, dry matter and N accumulation in shoot and root were measured. Root area was determined by digital image analysis, and influx of N into roots was estimated by plant growth analysis. Plants without root pruning presented higher shoot mass, root mass, root area and N accumulation than plants with total root pruning, at every harvest. Application of N at transplanting or 30 DAT provided higher shoot growth at the end of the experiment. Time of N application did not affect root mass and N accumulation, but plants receiving N at transplanting had higher root area at 120 DAT. Plants with total root pruning showed higher influx of N into roots, compensating partially their lower root area. It is concluded that the partial or total root pruning at transplanting of micropropagated seedlings reduced the growth and N accumulation of pineapple plant, and that the N application at transplanting provided higher shoot growth than late N application.
pineapple; Ananas comosus; plant growth analysis; root
