In vitro establishment and anatomical analysis of Bauhinia holophylla (Bong.)

Abstract

Bauhinia holophylla (Bong.) Steud. is an endemic legume of the Brazilian Savanna that has economic and medicinal importance. The natural and conventional propagation occurs through seeds, whose production occurs during a few months per year. Currently, the Brazilian Savanna agricultural expansion aggravates the propagation and conservation of B. holophylla species. Considering the few studies about the environmental factors effects on germination and growth of B. holophylla, micropropagation is a promising alternative for seedlings production and species conservation. The aim of this work was to establish a protocol for in vitro seed germination, shoots induction and elongation of B. holophylla explants. To obtain in vitro seedlings, seeds were germinated on culture medium WPM 50 and 100%, MS 50 and 100% of salts concentration or water + agar. After 30 days, nodal segments of B. holophylla from seedlings were isolated and inoculated into WPM culture medium supplemented with the 6-benzylaminopurine (BAP) at concentrations of 0, 0.48, 8, 16 μM. After induction of shoots, the explants were inoculated in WPM culture medium containing different concentrations of gibberellic acid (GA3): 0, 5, 10 and 20 μM. In the experiments the following parameters were evaluated: germination percentage, oxidation, stem length, leaf number and number of nodes. At the end of the multiplication experiment, leaves were collected for histological analysis. For in vitro seeds germination, the water + agar substrate showed higher percentages of germination (91%), not differing from the culture media MS 50% and WPM 100%. However, for growth parameters, the best culture medium was WPM 100%. For nodal segments multiplication, there was a significant increase on shoot number related with BAP concentration. For shoots elongation, there was reduction on stem size with the increase of GA3 concentration. In the anatomical analyses, the development of palisade and spongy parenchyma and vascular bundles was observed in B. holophylla in vitro leaves.