SIMULATIONS OF MICROCLIMATE IN GREENHOUSES AIMING THE ACCLIMATIZATION OF MICROPROPAGATED SEEDLINGS OF BANANA CV. GRANDE NAINE

In acclimatization processes, the environment control takes over a part of vital importance, since in in vitro condition banana seedlings do not efficiently operate the absorption of light. water and nutrients. Therefore, they should be Submitted to controlled environments under feasible conditions Of luminosity, temperature (around 28 degrees C, with minimum of 18 degrees C and maximum of 34 degrees C), and relative humidity above 75%. For this purpose, it was installed five mini tunnels with controlled temperature and relative humidity. For the control of temperature it was used pad-fan evaporative coolers at 28/25 degrees C. For the control of relative humidity it was used fogging during the day at 75% Under intermittence of 6s at each 40s. For temperature and relative humidity monitoring, it was installed three aspirate psychrometers in each mini tunnel connected to a data logger for daily acquisition every 60s. Temperature and relative air humidity were adequate for plants development, however significant differences were observed between the different environment conditions. For luminosity Study, under transparent plastic film (low density polyethylene) of 100 mu m thickness, it was used four meshes with average shading in the PAR spectrum band (400 to 700nm) of 69.92%, 50.73%, 29.73%, and 57.77%, being the first three in red color (with top level at 580nm, and abrupt reduction after that), the fourth mesh was black (linear behavior). The fifth tunnel had only transparent plastic film, showing 12.74% of solar radiation interception. These values were obtained from paired samples (mesh and plastic film) for the first four tunnels, and only the transparent plastic film for the last, using a spectral radiometer (400 to 1100nm), with spectral resolution of 2nm. Inside and outside of each environment it was obtained global and PAR irradiance by using calibrated photovoltaic sensors at 9:00, 12:00, and 3:00, under clean and cloudy sky, during the summer of 2004/05, and winter of 2005. The red mesh presented differentiated transmittances at the PAR spectrum band which established an interesting material for acclimatization studies. Results show bigger reductions on the PAR spectrum band for the red mesh, regardless of time. solar radiation. or seasons. which agree with the results obtained by the spectral radiometer