Acclimatisation of orchids using plant growth-promoting bacteria and humic acids

ABSTRACT Acclimatisation of orchid seedlings propagated in vitro is a slow process that can be accelerated with the use of plant growth-promoting microorganisms and humic substances. The aim of this study was to evaluate the plant’s response to inoculation with plant growth-promoting bacteria and humic acids, as well as to their combined use, during the period of acclimatisation of Cymbidium sp. orchids. The treatments were control; application of humic acids; inoculation with Stenotrophomonas maltophilia; inoculation with Burkholderia cepacia; inoculation with S. maltophilia and B. cepacia; inoculation with S. maltophilia combined with application of humic acids; inoculation with B. cepacia combined with application of humic acids; inoculation with S. maltophilia and B. cepacia combined with application of humic acids. A total of 150 days after acclimatisation, the plants were biometrically and nutritionally evaluated. Inoculation with the bacterial strains separately promoted seedlings with greater N content; however, only inoculation with S. maltophilia, resulted in plants with more total dry matter in relation to the control. There was no response from application of humic acids in an isolated manner or in combination with the bacterial strains. The results indicate the biotechnological potential of the bacteria S. maltophilia in promoting the growth of the Cymbidium sp. orchid.