TY  - JOUR
AU  - Busch, F.
AU  - Hüner, N. P. A.
AU  - Ensminger, I.
TI  - Increased air temperature during simulated autumn conditions does not increase photosynthetic carbon gain but affects the dissipation of excess energy in seedlings of the evergreen conifer Jack Pine
JO  - Plant physiology
VL  - 143
SN  - 0032-0889
CY  - Rockville, Md.: Soc.
PB  - JSTOR
M1  - PreJuSER-56247
SP  - 1242 - 1251
PY  - 2007
N1  - Record converted from VDB: 12.11.2012
AB  - Temperature and daylength act as environmental signals that determine the length of the growing season in boreal evergreen conifers. Climate change might affect the seasonal development of these trees, as they will experience naturally decreasing daylength during autumn, while at the same time warmer air temperature will maintain photosynthesis and respiration. We characterized the down-regulation of photosynthetic gas exchange and the mechanisms involved in the dissipation of energy in Jack pine (Pinus banksiana) in controlled environments during a simulated summer-autumn transition under natural conditions and conditions with altered air temperature and photoperiod. Using a factorial design, we dissected the effects of daylength and temperature. Control plants were grown at either warm summer conditions with 16-h photoperiod and 22 degrees C or conditions representing a cool autumn with 8 h/7 degrees C. To assess the impact of photoperiod and temperature on photosynthesis and energy dissipation, plants were also grown under either cold summer (16-h photoperiod/7 degrees C) or warm autumn conditions (8-h photoperiod/22 degrees C). Photosynthetic gas exchange was affected by both daylength and temperature. Assimilation and respiration rates under warm autumn conditions were only about one-half of the summer values but were similar to values obtained for cold summer and natural autumn treatments. In contrast, photosynthetic efficiency was largely determined by temperature but not by daylength. Plants of different treatments followed different strategies for dissipating excess energy. Whereas in the warm summer treatment safe dissipation of excess energy was facilitated via zeaxanthin, in all other treatments dissipation of excess energy was facilitated predominantly via increased aggregation of the light-harvesting complex of photosystem II. These differences were accompanied by a lower deepoxidation state and larger amounts of beta-carotene in the warm autumn treatment as well as by changes in the abundance of thylakoid membrane proteins compared to the summer condition. We conclude that photoperiod control of dormancy in Jack pine appears to negate any potential for an increased carbon gain associated with higher temperatures during the autumn season.
KW  - Carbohydrate Metabolism
KW  - Carbon: metabolism
KW  - Carbon Dioxide: metabolism
KW  - Chlorophyll: metabolism
KW  - Energy Metabolism
KW  - Fluorescence
KW  - Photoperiod
KW  - Photosynthesis
KW  - Pigments, Biological: metabolism
KW  - Pinus: growth & development
KW  - Pinus: metabolism
KW  - Saskatchewan
KW  - Seasons
KW  - Seedling: metabolism
KW  - Temperature
KW  - Pigments, Biological (NLM Chemicals)
KW  - Carbon Dioxide (NLM Chemicals)
KW  - Chlorophyll (NLM Chemicals)
KW  - Carbon (NLM Chemicals)
KW  - J (WoSType)
LB  - PUB:(DE-HGF)16
C6  - pmid:17259287
C2  - pmc:PMC1820919
UR  - <Go to ISI:>//WOS:000244757700016
DO  - DOI:10.1104/pp.106.092312
UR  - https://juser.fz-juelich.de/record/56247
ER  -