Increased susceptibility to photoinhibition in pre‐existing needles experiencing low temperature at spring budbreak in Sakhalin spruce (<i>Picea glehnii</i>) seedlings

<jats:p> <jats:bold>The seasonal changes in photosynthetic properties in 1‐year‐old needles of Sakhalin spruce (<jats:italic>Picea glehnii</jats:italic>) were measured using the chlorophyll fluorescence technique at various temperatures (5, 10, 20, 25 and 30°C). In the course of seasonal change, a temporary decrease in the quantum yield of PSII electron transport (Φ<jats:sub>PSII</jats:sub>) was observed just before budbreak. A decline in photochemical quenching (<jats:italic>q</jats:italic><jats:sub>P</jats:sub>) was observed at the same time as that of Φ<jats:sub>PSII</jats:sub> but only at the two lowest temperatures (5 and 10°C). Photochemical efficiency of open PSII (<jats:italic>F</jats:italic><jats:sub>v</jats:sub>′/<jats:italic>F</jats:italic><jats:sub>m</jats:sub>′) also declined just before budbreak at 25 and 30°C. An increase in thermal energy dissipation as indicated by a decrease in <jats:italic>F</jats:italic><jats:sub>v</jats:sub>′/<jats:italic>F</jats:italic><jats:sub>m</jats:sub>′ before budbreak was not significant at lower temperatures (5 and 10°C) in spite of the declines in <jats:italic>q</jats:italic><jats:sub>P</jats:sub>. This implies that thermal energy dissipation necessitated by the decline in Φ<jats:sub>PSII</jats:sub> might not be sufficiently strong to prevent a decline in <jats:italic>q</jats:italic><jats:sub>P</jats:sub> at lower temperatures. On the other hand, at higher temperatures no decline was observed in <jats:italic>q</jats:italic><jats:sub>P</jats:sub> because Φ<jats:sub>PSII</jats:sub> decreased to a relatively small extent, therefore thermal energy dissipation is sufficient in coping with the excessive energy accumulation in PSII. Seedlings of Sakhalin spruce exposed to ambient air temperature below 10°C before budbreak exhibited photoinhibition indicated by a decrease in the maximal photochemical efficiency of PSII (<jats:italic>F</jats:italic><jats:sub>v</jats:sub>/<jats:italic>F</jats:italic><jats:sub>m</jats:sub>) after an overnight dark adaptation. The present study suggests that 1‐year‐old shoots of Sakhalin spruce have an increased susceptibility to photoinhibition at low temperature just before budbreak.</jats:bold> </jats:p>