Use of colored shade nets has shown benefits in bell pepper and other horticultural crops. There is still, however, limited information on plant growth and physiology of bell pepper crop grown under colored shade nets. The objective was to determine the effects of colored shade nets on plant growth, leaf gas exchange, and leaf pigments of field-grown bell pepper. Experimental design was a randomized complete block with four replications and five shade treatments (black, red, silver, and white nets, and an uncovered control). Mean and maximal air temperature and midday root zone temperature (RZT) were highest in the unshaded treatment. Differences in air temperatures between shade net treatments were smaller compared with the differences in RZT between treatments. Plant fresh weight and stem diameter were reduced in the unshaded treatment, and there were no plant fresh weight and stem diameter differences among shade nets. The incidence of Phytophthora blight (caused by Phytophthora capsici) was greatest in the unshaded treatment. Leaf stomatal conductance (gS) and photosystem II efficiency were reduced and leaf temperature increased in unshaded conditions. Leaf net photosynthesis, gS, internal CO2, and PSII efficiency decreased with increasing leaf temperature. Differences in leaf temperature among shade net treatments were because of differences in solar radiation captured by leaves. Leaf total carotenoids were lowest in unshaded conditions and there were no differences in total carotenoids among the shade nets. Chlorophyll a concentration and chlorophyll a/b ratio was lowest in unshaded conditions. Leaf total phenols, flavonoids, and cupric reducing antioxidant capacity (CUPRAC) values were highest in red net and in unshaded conditions. Trolox equivalent antioxidant capacity (TEAC) values were highest in red net and lowest in silver net. In conclusion, compared with unshaded conditions, shade nets resulted in improved bell pepper plant growth and leaf gas exchange. These responses were due primarily to the reduced leaf and root zone temperatures under shaded conditions, regardless of the color of shade net. The differences in plant growth and function due to color of shade net were inconsistent or minor for most of the plant variables measured.
Financial support was provided by the Georgia Agricultural Experiment Stations. This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number 2014-33610-22604.We thank Jesús Bautista, Gunawati Gunawan, and Nélida Bautista for their invaluable technical support and Jason Brock of the Plant Disease Clinic, University of Georgia, for identification of plant diseases. We appreciate the thorough review of the manuscript by Erick Smith, André Luiz Biscaia Ribeiro da Silva, and the anonymous reviewers.Mention of trade names in this publication does not imply endorsement by the University of Georgia of products named, nor criticism of similar ones not mentioned.J.C.D.-P. is the corresponding author. E-mail: email@example.com.
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