Photoautotrophic growth response of in vitro cultured coffee plantlets to ventilation methods and photosynthetic photon fluxes under carbon dioxide enriched condition

Effects of two ventilation methods (forced and natural) and two photosynthe tic photon fluxes (PPF, 150 and 250 mu mol m(-2) s(-1)) on the photoautotro phic growth of in vitro cultured coffee (Coffea arabusta) plantlets were in vestigated. Number of air exchanges was 2.7, 5.9 and 3.9 h(-1) for forced l ow rate, forced high rate and natural ventilation, respectively. Single nod e cuttings of in vitro cultured coffee plantlets were cultured on Florialit e, a mixture of vermiculite and cellulose fibers with high air porosity, em erged in liquid half strength basal MS medium, without sucrose, vitamins an d plant growth regulators. The study included 40 days in the in vitro stage and 10 days in the ex vitro stage. Mean fresh and dry weights, leaf area, shoot and root lengths and net photosynthetic rate per plantlet were signif icantly greater in forced high rate treatments compared with those in natur al and forced low rate treatments. PPF had a distinct effect on shoot lengt h suppression and root elongation of coffee plantlets in forced high rate t reatments. The control of carbon dioxide concentration inside the culture b ox according to the plant demand when growing was easy with the forced vent ilation method in photoautotrophic micropropagation.