Effects of photoperiod, plant growth regulators and culture media on in vitro growth of seedlings of Cyrtochilum loxense (Lindl.) Kraenzl. an endemic and endangered orchid from Ecuador

Cyrtochilum loxense (Lindl.) Kraenzl. is an endemic and seriously endangered orchid species
endemic in the Loja Province (Southern Ecuador). The main goals of this research were to
analyze how culture media, plant growth regulators and photoperiod affect the growth of C.
loxense. Eight month old plants (approximate 1 – 1.5 cm in height) obtained by in vitro ger-
mination, were cultivated on MS media or Knudson C; MS with three levels of naphthalene
acetic acid (NAA) and 6-benzylaminopurine (BAP) (2/0.5; 1/0.5 y 0.5/ 0.5 mg-1L); and three
photoperiodic regimes (24/0, 16/8, 8/16 h) on MS with and without plant growth regulators. No significant differences of shoot induction were observed on media with and without plant
growth regulators, and all tested photoperiods. The highest growth (1.2 cm) was observed
in plantlets cultivated on growth regulator-free media with a 16/8 photoperiod. Also the shoot
and root formation was better in this species in absence of plant growth regulators. Probably
this response is due to the endogenous hormone levels in the tissues or due to the kind and
concentrations of PGRs used were too low to induce positive morphogenetic responses.