Qualidade de sementes de pitaias submetidas ao estresse hídrico.

Abstract

Dragon fruit are cacti grown in tropical and subtropical regions. Its cultivation in Brazil is still incipient with areas located in the states of the South and Southeast and, more recently, in semi-arid regions of the Northeast, where water resources are scarce. Despite being characterized as a species tolerant to water deficiency, pitaya shows great sensitivity to this factor during the germination process. Because it is necessary to evaluate the germination performance under stress conditions, the present work aims to evaluate the effect of water stress on the germination performance of dragon fruit species. The experiment was conducted in a completely randomized design in a 2 x 6 factorial scheme, corresponding to two pitaya species (Hylocereus undatus, Hylocereus costaricensis) and six water potential gradients (0; -0.2; -0.4; -0, 6; -0.8 and -1.0 MPa) using Polyethylene glycol 6000 as an osmotically active agent, using four replicates of 50 seeds per treatment. The following variables were analyzed: percentage, first count, speed index, average time, average germination speed, radicle length, shoot length and seedling fresh mass. The data obtained were submitted to analysis of variance by the F test with 5% of significance. The averages obtained for the species were compared by Tukey test, while the data for water potentials were submitted to regression analysis. The reduction of the osmotic potentials of the imbibition water causes decreases in the quality and vigor of the seeds of H. undatus and H. costaricensis. Osmotic potentials below -0.6 MPa completely restrict the physiological manifestations of H. undatus and H. costaricensis seeds.