RESUMO
Optical brighteners have attracted interest as adjuvant's in baculovirus-based biological insecticides due to their ability enhance the insecticidal properties of these viruses and protect virus particles from the degrading effects of ultraviolet (UV) radiation. The effects of two types of optical brighteners, Tinopal CBS (a distyryl-biphenyl derivative) and Tinopal C1101 (an ethenediyl benzenesulfonic derivative) at 1 or 3% (wt./vol.), on growth of different crOPs [maize, Zea mays L. (var. HY-311), sorghum, Sorghum vulgare Pers. (var. Silo), tomato, Lycopersicum esculentum L. (var. Floradade IT), or pepper, Capsicum annum L. (var. Cal Won 300)] were examined after once a week application during four weeks. Both compounds significantly affected the growth of maize plants, whereas sorghum plants were affected only at the highest concentration of Tinopal C1101. Neither brightener had negative effects on tomato or peppers plants. Both compounds increased the percentage of reflectance of maize and tomato leaves when analyzed using laboratory and field spectrophotometers. A greenhouse experiment involving single application of 1 and 3% Tinopal C1101 indicated that the stomatal conductance and photosynthetic rate of maize and tomato plants were not significantly affected. We conclude that the effects of optical brighteners on plant growth are more likely to be influenced by differences between plant species than differences between brightener compounds.