Daniel J. Winstead

The Pennsylvania State University

Myungjin Lee

The Pennsylvania State University

Maria J. de Lima Brossi

The Pennsylvania State University

Erin L.Connolly
The Pennsylvania State University

Francesco Di Gioia

The Pennsylvania State University

Abstract

Although representing a small proportion of solar radiation, ultraviolet (UV) radiation (280–400 nm) has been shown to greatly affect growth, photomorphogenesis, and secondary metabolism in plants. Given the implications to crop physiology and nutritional quality, there is interest in understanding the effects of supplemental UVA and UVB radiation on the growth and phytonutrient content of nutrient-dense crops, like microgreens. We conducted a greenhouse study to evaluate the effect of supplemental UVA, UVB, and combined UVAB radiation on yield, mineral profiles, and antioxidant components of two varieties of pea (Pisum sativum L.) microgreens: ‘Field Pea’ and ‘Dwarf Grey Sugar Pea.’ After full germination, pea shoots were exposed to sunlight for one day and then were exposed to supplemental treatments of UVA (1.83 W/m 2 ), UVB (0.61 W/m m 2 ) + UVB (0.61 W/m 2 2 ), or UVA (1.55 W/ ) radiation for 3-, 6-, or 12-h/day for 6 days. The supplementary UVA treatment significantly increased fresh yield and dry weight in pea microgreens, with 12-h of UVA having the highest yield. Conversely, exposure to supplementary UVB and UVAB produced a loss in yield with all exposure times above 3- h/day. Exposure to UVA radiation had no significant effect on total phenolic content (TPC) and total antioxidant activity (TAA), while the exposure to UVB and UVAB radiation showed a significant decrease of both TPC and TAA with exposure times above 3-h/day. UVB supplementary radiation reduced pea shoot mineral accumulation, while UVA positively influenced mineral content only in ‘Dwarf Grey Sugar Pea’. These results suggest that exposure to supplementary UVB radiation (0.61 W/m 2 ) for longer than 3-h/day, regardless of the exposure to UVA radiation, results in significant losses in yield and antioxidant synthesis in pea microgreens.