Micropropagação de duas espécies de Vellozia (Velloziaceae) da Chapada Diamantina, Bahia: aspectos fisiológicos e bioquímicos

Abstract

Chapada Diamantina is predominantly composed of rupestrian fields, presenting endemic species that contribute to the ornamentation of the landscape, such as Vellozia pyrantha and Vellozia punctulata, which were used in this study. The aim of this study was to establish micropropagation protocols for these species. The in vitro cultivation of V. punctulata and V. pyrantha was carried out through the establishment with disinfected seeds inoculated in MS ⅓ medium, 15 g L-1 sucrose, and 7 g L-1 agar; the aerial part of the seedlings was the selected explant, which was transferred for in vitro multiplication, facilitated by benzylaminopurine (BAP) at concentrations of 0.00; 4.44; 8.88; 17.76 µM for V. pyrantha explants. The shoots, obtained after in vitro multiplication, were rooted in vitro, and the addition of activated charcoal to the medium and two types of sealing of the containers (PVC or cotton) were tested. The microplants were acclimatized in greenhouses. In the micropropagation of V. pyrantha, during the multiplication stage, an average of 9.35 shoots were obtained using 8.88 µM of BAP. The charcoal favored the length of the aerial part (CPA) and root part (CPR), while the number of roots and CPR were favored by the use of the cotton seal. There was a survival rate of 80 to 95% of the plants after 30 days of acclimatization, allowing the inference that micropropagation is an efficient technique for the production of V. pyrantha seedlings. When micropropagating V. punctulata, two strategies were tested for in vitro multiplication, with salt stress induction using NaCl (0; 10; 20; 40; and 80 mM), and the use of the plant growth regulator BAP (0.00; 4.44; 8.88; 13.32; 17.76 µM). The salt stress, induced with the concentration of 40 mM NaCl, produced 2.53 shoots, while the use of BAP promoted the emergence of 7.6 shoots at the concentration of 10.72 µM. During the regeneration period of the shoots induced by stress, proline quantification was carried out; on the 30th day of in vitro cultivation in the medium without NaCl, 1.77 µg of proline was observed, and 16.41 µg in the medium containing 40 mM NaCl. Only the shoots obtained with BAP were transferred for in vitro rooting, where it was observed that the sealing with cotton favored this stage. The acclimatization of V. punctulata showed a survival rate above 92.5%, and the prior use of cotton sealing in rooting resulted in increased fresh and dry mass of the aerial and root parts in the acclimatized plants. This study established the first micropropagation protocol for the species V. pyrantha and V. punctulata, proving the efficiency of the technique, and it took 240 days to obtain the microplants from in vitro germination.