Effect of ultraviolet radiation the germination rate of tree seeds

Abstract

Extensive use of conifers is highly advisable for urban landscaping, since they are ever-green, low exploited and long-living compared to their deciduous counterparts. The paper presents the effect of ultraviolet (UV) radiation on the germination rate of Thuja occidentalis (2014), Picea fennica (2016) and Pinus sylvestris (2016) seeds exposed to environmentally friendly UV light-emitting diodes (LEDs). We used two sources of UV: the first one consisted of 54 LEDs with power of 2 W, the second one - 81 LEDs of 3 W. UV radiation was mostly within the A range (> 90%) and had a length of 315 nm. It was found out that UV radiation improved the germination rate of Picea fennica seeds from Quality Class 2 to Quality Class 1, i.e. from 75% to 86%, thus reducing the planting rates and, subsequently, the planting costs. After being exposed to the UV dosage of 2 kJ/m2, Thuja occidentalis seeds had 12.8% better germination rate than the control sample, resulting in faster growth and earlier full-grown shoots. UV-A radiation did not have identifiable positive effects on the pine seeds.