Light drives vegetative phenology of Cattleya intermedia (Orchidaceae): a key factor for the establishment of plants translocated into a fragment of subtropical Atlantic Forest

Despite Orchidaceae is a key component of the epiphytic flora of tropical and subtropical forests, phenological studies of this group are rare, mainly due to technical difficulties in observing epiphytes, the reduced abundance of wild specimens, and to the evergreen characteristic of these plants. We monitored shoot and root production of translocated young plants of the epiphytic orchid Cattleya intermedia Graham at the edge and in the interior of a subtropical Atlantic Forest fragment, and investigated their relationship with temperature, luminosity, photoperiod, rainfall and air humidity. Individuals propagated in vitro were translocated in the spring and inspected monthly for 3 years for shoot and root production. Shoot production at the edge of the forest was positively related with photoperiod and luminosity. In the interior, this relationship was characterised by a 1-month time delay. The highest concentrations of plants with shoot production occurred in spring and summer in both environments. Interior plants were more likely to produce roots in spring and summer, while edge plants were more likely to produce roots in summer. Edge plants produced fewer roots when rainfall was high, while interior plants produced more roots when interior air humidity was high. The influence of light availability for translocated plants was demonstrated by the different responses of shoot growth at the edge and in the interior of the forest and by the relationship with the seasonal variation of this variable. Thus, light becomes a key factor for the establishment of translocated C. intermedia and must be considered in the choice of their habitats.