Morphological and biochemical responses of broccoli florets to supplemental ultraviolet-B illumination

The effect of different doses of supplemental ultraviolet-B (UV-B) illumination on yield, plant growth, biochemical changes and antioxidant activity of broccoli florets was evaluated. The broccoli plants were grown under three different supplemental UV-B illumination doses (2.2, 8.8 and 16.4 kJ m(-2)d(-1)) in the glasshouse. Plant height decreased with increasing supplementary UV-B illumination dose. However, leaf thickness increased with increasing UV-B dose. Chlorophyll content in the leaves also increased during the growing period. The lowest chlorophyll content was found at 16.4 kJ m(-2)d(-1) UV-B dose. Total yield decreased with supplemental illumination, especially at 16.4 kJ m(-2)d(-1) illuminated dose. Total dry matter, total soluble solids, carotenoids, chlorophyll a and b content in broccoli florets decreased with increasing UV-B illumination dose. Conversley, ascorbic acid, sinigrin, total phenolic, and flavonoid content and antioxidant activity increased in UV-B illuminated florets. Surprisingly, glucotropaeolin content, one of the forms of glucosinolate in broccoli, was not affected significantly by UV-B illumination or enhanced by UV-B illumination doses.