Photosynthetic activity of Scots pine ( Pinus sylvestris L.) needles during winter is affected by exposure to SO 2 and NO 2 during summer

• Published in: New Phytologist
• Main Author: STRAND, MARTIN
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1993
• Subjects: Northern Sweden
• Online Access: http://dx.doi.org/10.1111/j.1469-8137.1993.tb04539.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1469-8137.1993.tb04539.x; https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.1993.tb04539.x

SUMMARY A 50‐year‐old stand of Scots pine ( Pinus sylvestris L. with a mean height of 12 m. located 60 km northwest of Umeå in northern Sweden, was furnigated with SO 2 and NO 2 from June to September in 1998 and 1989. SO 2 and NO 2 were released from vertical vent‐pipes arranged ina circle with a diameter of 60m. During fumigation, the average concentrations of both SO 2 and NO 2 in the centre of the circle were 10–15 nl l ‐1 . Measurements of CO 2 evolution and chlorophyll a fluorescence of needles were made under laboratory conditions. For samples collected in January of 1989 and 1990, the light‐ and CO 2 ‐saturated rate of O 2 evolution at 20°C in needles of trees exposed to SO 2 + NO 2 was lower than in needles of trees exposed to ambient clean air. Furthermore, the photochemical efficiency of photosystem II, as indicated by the ratio of variable to maximum fluorescence was lower for needles of fumigated trees, in samples collected in December 1989 and January 1990. These results suggest that low concentrations of SO 2 + NO 2 may have significant long‐term effects n the photosynthetic apparatus in needles of Scots pine. The observed responses may be triggered by unfavourable environmental conditions during autumn and winter. However, no evidence for a greater sensitivity to prolonged freezing stress at –19°C was found in needles of trees exposed to SO 2 + NO 2 when measured in December or January.