Environmental and developmental effects on the biosynthesis of UV‐B screening pigments in Scots pine (Pinus sylvestris L.) needles

Abstract

The major UV-B screening pigments of the epidermal layer of Scots pine ( Pinus sylvestris ) needles are flavonol 3-oglycosides (F3Gs) esterified with hydroxycinnamic acids at positions 3 ¢¢ and 6 ¢¢ . Acylation is the last step in biosynthesis and is catalysed by position-specific hydroxycinnamoyl transferases (3 ¢¢ and 6 ¢¢ HCT). The UV-B dependence of these enzyme activities was studied in primary needles of Scots pine seedlings grown under different UV-B conditions in environmentally controlled sun simulators. 6 ¢¢ HCT activity was induced upon UV-B irradiation while 3 ¢¢ HCT activity was not induced but showed high constitutive values. To investigate the biosynthesis of diacylated F3Gs during needle development under natural conditions, the HCT activities and metabolite contents were analysed in needles of field-grown mature pine trees. Accumulation of diacylated compounds as well as of 6 ¢¢ HCT activity occurred transiently in the first year of needle development only. In contrast, 3 ¢¢ HCT activity exhibited broad maxima in two consecutive years during needle growth. The data suggest that acylated F3Gs are first formed as soluble compounds which are then translocated into the cell wall to be bound by their hydroxycinnamoyl residues.

Effects of ultraviolet (UV) exclusion on the seasonal concentration of photosynthetic and UV‐screening pigments in Scots pine needles

“…6). This trend is in agreement with results from Kaffarnik et al (2006) who showed that under field conditions, the concentration of soluble DCA increased sharply during early needle development and continuously decreased until the end of the second growing season, likely due to its progressive translocation to the cell wall. Diacylated flavonol glycosides, and particularly DCA, are efficient UV-screening pigments.…”

Ultraviolet and photosynthetically active radiation can both induce photoprotective capacity allowing barley to overcome high radiation stress

“…1 and 3). Other authors also report that both UV and high PAR can induce flavonoid accumulation (G€ otz et al, 2010;Kaffarnik et al, 2006). Thus, our results reinforce the importance of taking both PAR and UV acclimation into consideration when considering plant responses to UV-B radiation (Krizek, 2004;G€ otz et al, 2010).…”

Ozone affects shikimate pathway genes and secondary metabolites in saplings of European beech (Fagus sylvatica L.) grown under greenhouse conditions

“…8). A similar behavior has been described in 60-year-old European beech in a free-air chronic ozone field study (Bahnweg et al 2005), as well as in mature Scots pine and Norway spruce trees, where a deposition of the soluble fraction into cell walls during leaf ontogeny has been suggested (Heilemann and Strack 1990; Kaffarnik et al 2006). In the present study, we observed the appearance of 3,3 0 ,4,4 0 -tetramethoxybiphenyl in response to ozone exposure.…”