Exploring the role of phytohormones in modulating in vitro orchid growth

Abstract

Orchids have a high ornamental potential due to their diversity of colors, shapes, and sizes. However, improper extraction by traders and collectors can lead to the risk of these species' extinction. Therefore, this research aimed to evaluate the use of naphthaleneacetic acid (ANA) and 6-benzylaminopurine (BAP) in the in vitro growth of Pseudolaelia corcovadensis, Macradenia paraensis, and Maxillaria brasiliensis. The experiment was carried out in the Plant Tissue Culture Laboratory with endemic orchids: Pseudolaelia corcovadensis, Macradenia paraensis, and Maxillaria brasiliensis. The experiment was set up in a completely randomized design in a 4 x 3 factorial scheme, with a total of 12 treatments and 10 replications each: T0 - MS medium (100%); T1 - MS medium (100%) + 0.5 mg L^-1of ANA; T2 - MS medium (100%) + 0.5 mg L^(-1) of ANA and 0.5 mg L^(-1) of BAP; and T4 - MS medium (100%) + 0.5 mg L(^-1) of BAP. The treatments were performed using MS medium, and the plants were kept in laboratory conditions until 120 days of age, when contamination and growth were assessed. The statistical analysis highlighted a high rate of contamination during the repotting cycles. Even with contamination, the orchids showed vegetative growth using phytohormones. This observation allows us to conclude that 100% MS medium should be used for Maxillaria brasiliensis, and 100% MS medium + 0.5 mg L^-1ANA proved to be the most satisfactory for Macradenia paraensis and Pseudolaelia corcovadensis.