Physiological responses of microclonally propagated willow to excessive levels of UV-B radiation
Abstract
Willow plantations represent a rapidly deployable source of lignocellulosic biomass for bioenergy and a reservoir of bioa c tive compounds for pharmaceutical use. However, their physiological resilience to increasing ultraviolet-B (UV-B; radiation with a wavelength of 280–320 nm), under current climate change scenarios, remains insufficiently characterised. This study evaluated the physiological responses of the microclonally propagated willow clone ‘Zhytomyrska-1’ to acute UV-B treatments. Our exp e riments were focused on leaf pigmentation and nitrogen-related status as indicators of stress. Uniform in vitro -derived plantlets were acclimatised in greenhouse conditions and divided into four groups: non-irradiated control and three UV-B treatments r e ceiving single acute doses of 5, 10, and 15 kJ/m². Non-destructive leaf measurements were performed with a portable multipi g ment meter (MPM-100) at seven time points during a two-month period post-exposure to capture short-, medium- and long-term effects. We determined relative chlorophyll, flavonol, and anthocyanin indices, and the nitrogen balance index (NBI) as an int e grative parameter for leaf nitrogen status. Data were analysed by both one-way and two-way ANOVA to separate the effects of dose, time and their interaction. Time (developmental stage and seasonal progression) was the dominant factor driving variation in all measured parameters, excluding anthocyanin. The contents of chlorophyll and flavonol were increased at later stages of the vegetation, on days 66 and 70. Meanwhile, the nitrogen balance index tended to decrease at the time points 10–17 days, but this effect was absent after UV-B ir radiation at 15 kJ/m², where the nitrogen balance index remained relatively stable during the st u died period. Compared to the impact of time, the effects of UV-B radiation were weaker and less consistent, in some cases i n creasing the levels of chlorophyll and the nitrogen balance index, while decreasing th e levels of anthocyanins. Overall, the willow clone ‘Zhytomyrska-1’ demonstrated relative physiological stability across the tested UV-B dose range, suggesting resilience to mo d erate increases in UV-B comparable to regional annual doses.References
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