In a greenhouse covered with transparent low density polyethylene, in Piracicaba — SP/Brazil, utilizing red, blue, black thermo-reflective screens (aluminized screen) all with 70% shading at 1.0 m above the cultivation bench, Holcman & Sentelhas (2006) evaluated the growth and development of the bromeliad (Aechmea fasciata) and concluded that the red screen resulted in the highest biometric values, however, the thermo-reflective screen was more favorable for the cultivation showing the best microclimate.

Seedlings of jasmine-oranges (Murraya exotica L) in full sun, under a white screen (30% shading) and black screen (50% shading), in Sao Cristovao-SE/Brazil, presented higher emergence in full sun and under the white screen; higher rate of emergence and number of leaves were observed in full sun, and greater dry matter of aerial part was found under both screens (Arrigoni-Blank et al., 2003). It is recommended to produce seedlings of jasmine — orange first in full sun and after emerge under a white screen with 30% shading (Tables 11 and 12).

Table 11. Mean values of the germination rate, plant height and number of leaves of jasmine orange (Murraya exotica) on different substrates and light conditions. Sao Cristovao-SE, 2000. Full sun Clarite® 30% Sombrite® 50% Substrate Dry weight of leaves Soil + sand 1:1 0.067 bcC * 0.142 bB 0.216 aA Soil + vermiculite + cattle manure 1:1:1 0.102 abC 0.232 aA 0.184 abB Soil + sand + cattle manure 1:1:1 0.055 cB 0.150 bA 0.166 bA Sand + cattle manure 1:1 0.131 aB 0.174 bA 0.182 abA Dry weight aerial part Soil + sand 1:1 0.091 bC 0.176 bB 0.271 aA Soil + vermiculite + cattle manure 1:1:1 0.124 abC 0.284 aA 0.223 abC Soil + sand + cattle manure 1:1:1 0.069 bB 0.184 bA 0.130 bA Sand + cattle manure 1:1 0.155 aB 0.218 bA 0.222 abA Dry weight of roots Soil + sand 1:1 0.061 aB 0.090 bB 0.142 aA Soil + vermiculite + cattle manure 1:1:1 0.087 aB 0.177 aA 0.106 aB Soil + sand + cattle manure 1:1:1 0.062 aB 0.117 bA 0.110 aA Sand + cattle manure 1:1 0.095 aB 0.129 bA 0.212 aAB * * Means followed by same uppercase letters in the rows, and same lowercase letters in the columns do not differ by the Tukey test at 5%; Adapted from Arrigoni-Blank et al. (2003)

Table 12. Mean values of dry weight of leaves, dry weight of the aerial part and dry weight of roots of jasmine orange (Murraya exotica) on different substrates and light conditions. Sao Cristovao-SE, 2000.

3. Conclusions

There are diverse crops produced and evaluated with regards to different growing environments, where yields and qualities are influence by the type, size and shape of the environment, covering material, climate, location, seasonality, interactions with containers and substrates and other factors.

Polyethylene film and shading screens used either individually or together, minimize direct radiation to the plant, depending on the format of the environment and the time of day, preventing this radiation from causing damage to plant tissues.

Matrix planting of vegetables, fruit, flowers and forest species, as well as acclimation and production of seedlings often requires initial shading with screens that present different degrees of shading, therefore care must be taken to select the mesh so that it does not cause irregular plant growth.

The protected environment maximizes the productive potential of plants and to obtain successful yields correct management of the environment is necessary along with the use of trained labor.