Diazotrophic Bacteria and Nitrogen Fertilization on ATPase Activity in Micropropagated Pineapple Plantlets During Acclimatization

Micropropagated plantlets, after removal from controlled laboratory conditions, require an acclimatization period. Adaptation to the new environment induces anatomical and physiological changes controlled by cellular processes. This study investigated the involvement of the primary proton transport systems of total membranes in pineapple root colonization by diazotrophic bacteria and in the development of plantlets treated with different nitrogen doses, allowing an understanding of nutrient absorption and accumulation dynamics. The experiment followed a randomized block design (RBD) in a factorial scheme (2 × 3 × 2), with two inocula (a mixture of diazotrophic bacteria containing Burkholderia sp. UENF 114111, Burkholderia silvatlantica UENF 117111, and Herbaspirillum seropedicae HRC 54, and another without bacteria), three urea doses (0, 5, and 10 g L−1), and two evaluation (90 and 150 days) and bacterial counting times (30 and 150 days), with three blocks. Diazotrophic bacterial populations were lower in older plantlets. H+ transport mediated by P H+-ATPases changed with acclimatization time. Inoculation did not induce transport; however, the Fmax of V H+-ATPase was lower without nitrogen fertilization. Nitrogen fertilization affected V H+-ATPase proton transport activity in root membranes. The presence of diazotrophic bacteria did not induce proton transport. On the other hand, nitrogen fertilization and acclimatization time affected the proton transport activity mediated by H+-ATPases isolated from roots of micropropagated pineapple.