493 Effect of Photoselective Screens in the Development and Productivity of Red and Yellow Sweet Pepper J.Q. Santana, M.A. Balbino, T.R. Tavares, R.S. Bezerra, J.G. Farias and R.C. Ferreira Agronomy and Food Engineering College Federal University of Goiás Goiânia Brazil Keywords: Capsicum annuum var. annuum, protected cultivation, crop ecology, photosynthetically active radiation Abstract Photoselective screens promote better solar radiation quality and attenuate the extreme climatic conditions allowing greater efficiency in the vegetables production in protected crops. In Brazil the sweet pepper is traditionally cultivated in field conditions, but recently there have been investments in screenhouses and greenhouses. This research evaluated the effect of photoselective blue and red screens on the vegetative development and productivity of yellow and red sweet peppers. The experiment was conducted from 19 June to 29 October 2011, in Goiânia, Goiás, Brazil (16°35’47”S; 49°16’47”W, 730 m). The ‘Eppo’ (yellow) and ‘Margarita’ (red) hybrids from Syngenta Seeds were cultivated in three treatments: two shading screenhouses with field plots as control. Stem diameter and length, number of leaves, leaf area, total plant mass and mass of leaves were measured. At 40 days the total number, weight, length, diameter and number of fruits lost by sunscald or rotting were measured. The blue and red screens have promoted greater stem growth and smaller number of leaves and fruits. There was no statistical difference for leaf area, showing there is compensation between number and leaf area. The total fruit production per plant occurred in decreasing order from field conditions, to red screen followed of blue. However, the losses by sunscald and rotting was greater than 35% in field conditions, while in the screenhouses the losses were less than 5%. In this way, the production of commercial fruits per plant was higher under red screenhouse than under the blue screenhouse and in the field. The photoselective red screen promoted greater plant growth and a slight increase (4%) in the commercial fruits yield for Brazilian Midwest climatic conditions. INTRODUCTION In the north, south and in the southeast Brazilian regions, where the climate is temperate and semi-tempered, the cultivation in protected environment aimed to minimize the effects of winter ensuring that way, continuous production of food. In tropical regions as the midwest of Brazil the average annual temperature is above 20°C, with only two defined seasons (dry and wet). Thus, the production of vegetables is predominantly in open conditions, with high productivity, especially in the dry season. However, in the last 10 years the use of screened and greenhouses to produce vegetables and fruits of high commercial value has increased in order to gain in productivity and quality, especially in the rainy season. The market has launched several models of screens to replace the black shading whose main objective is to protect the plants from direct solar radiation. These materials of low density polyethylene (LDPE) are of various colors (blue, red, yellow, gray) with specific functions. The red color screens transfer more of the solar radiation wave spectrum in the red and far red and diffuse solar radiation passing through the screen, being efficient in plant development (Li, 2006). The blue screens of the spectrum providing solar radiation at a wavelength of 440-490 nm, intensify the phototropism and photosynthesis (Rodrigues, 2002). Several studies (Shahak et al., 2006; Rajapakse and Shahak, 2007; Shahak et al., Proc. 7 th IS on Light in Horticultural Systems Eds.: S. Hemming and E. Heuvelink Acta Hort. 956, ISHS 2012