Costa & Leal (2009) observed that in hydroponic production of lettuce, variety Vera, in three greenhouses, one without evaporative cooling and CO2 injection, another with injection of CO2 and without evaporative cooling and a third, with CO2 injection and evaporative cooling (acclimatized), the environment with evaporative cooling and CO2 injection promoted the best development of plants with larger leaves.

In acclimatized environment with evaporative cooling, Costa & Leal (2008) found greater accumulation of leaf biomass and greater leaf area of strawberry plants than in non — acclimatized environments, regardless of the season (Table 1).

For five cultivars of lettuce (Veronica, Vera, Cinderella, Isabela, Veneranda) under four different environmental conditions (Black screens with 30%, 40%, 50% shading and without the screen) in the region of Caceres-MT/Brazil, Queiroz et al. (2009) found that the Veronica cultivar was the most productive during the winter of 2008 and shading of 40% was best for most cultivars.

RDM (g)

Table 3. Root dry mass (RDM) of cucumber seedlings at 23 days after sowing for the various hybrids (H) in environments (A) and substrate (S) studied.

In tomato production in greenhouses with and without aluminized screen, Gent (2007) verified that the use of the screen with 50% shading increased commercial fruit production by 9% compared to the environment without the screen, verifying the beneficial use of this screen type in protected environments. Comparisons between the mobile aluminized screens with 40, 50 and 60% shading and the environment with polyethylene plastic film painted with lime, were evaluated by Fernandez-Rodriguez et al. (2001) in tomato production and it was found that the screens minimize energy consumption during periods of low temperatures.

With the objective of evaluating cucumber seedlings in function of environmental conditions, polystyrene trays with 72 and 128 cells and substrates with percentages of organic compound in Aquidauana-MS/Brazil, Costa et al. (2009c) conducted an experiment in six environmental conditions: plastic greenhouse with a height of 2.5 m; nursery with a black monofilament screen with 50% of shading and height of 2.5 m; nursery with an aluminized screen with 50% of shading and height of 2.5 m; nursery covered with native coconut palms with height of 1.8 m; plastic greenhouse with height of 4.0 m, zenithal opening and thermo-reflective screen over the black monofilament screen with 50% of shading and height of 3.5 m. The authors concluded that the greenhouses promoted better results for cucumber seedlings.