Aspectos morfoanatômicos da estaquia de Selenicereus setaceus (Salm-Dyck) A. Berger ex Werderm. (Cactaceae)

Mello, C. C.Rowe, N. P.Soffiatti, P.Zuffellato-Ribas, K. C.SantAnna-Santos, B. F.

Abstract The cerrado pitaya (Selenicereus setaceus) is a Cactaceae with strong potential in the fruit market. For that reason, propagation cutting is an interesting alternative for fixing desirable characteristics for the species. Therefore, this work aimed to investigate the origin and morphoanatomy of adventitious roots from this species' cuttings, an essential step to develop alternatives to its management. The first experiment was carried out in spring and tested peat-carbonized pine bark and peat-expanded perlite as substrates. The second was carried out in autumn, and tested three substrates: vermiculite-carbonized rice husk, sand and bio-stabilized pine bark, vermiculite, charcoal mill and additives. The following variables were evaluated: rooting (%), number of roots per cutting, length of the three largest roots (cm) per cutting, survival (%) and sprouting (%). Fresh samples were cross-sectioned and stained with toluidine blue for the anatomical analyses. In spring, the sprouting and the number of roots were higher when the peat-expanded perlite was used. In autumn, the substrate used had no significant influence on the number of roots, only on the rooting percentage and the mean root length. In addition, in spring, the number and mean length of the roots were also higher when the peat-expanded perlite substrate was used compared to autumn. Thus, it is not recommended to prepare cuttings in autumn, as there is no sprouting. In the pith and the cortex, mucilaginous cavities and starch are abundant, ensuring water and energy supply, which probably influence the species' excellent rooting capacity. The formation of adventitious roots occurs from the interfascicular cambium, and these cross the perivascular fibres, cortical bundles, and the collenchyma, which, therefore, do not act as anatomical barriers. In regions where the periderm has already replaced the epidermis, there is no adventitious root formation, indicating that this tissue is a barrier to rooting. Although this species is recognized for its easy rooting, the type of substrate and the season influenced the variables assessed here.