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Title: NIGHT TEMPERATURE HAS A MINIMAL EFFECT ON RESPIRATION AND GROWTH IN RAPIDLY GROWING PLANTS

Author
item Frantz, Jonathan
item COMETTI, NILTON - BRAZIL
item BUGBEE, BRUCE - UTAH STATE UNIVERSITY

Submitted to: Annals of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2004
Publication Date: 5/24/2004
Citation: Frantz, J., Cometti, N.N., Bugbee, B. 2004. Night temperature has a minimal effect on respiration and growth in rapidly growing plants. Annals Of Botany. 94:155-166.

Interpretive Summary: Plant growth depends on efficient photosynthesis and respiration. In high temperatures, respiration may be inefficient and in low temperatures, respiration may not be adequate. Most studies of respiration in plants are short-term measurements (minutes to hours) on plant parts (e.g. leaf disks, whole leaves, or roots) and these results are used to extrapolate across the whole plant and plant communities for entire growing seasons. In this study, we measured communities of soybean, tomato, and lettuce respiration and photosynthesis, including roots, continuously for between 25 and 37 days. Upon canopy closure at about Day 16, the night temperatures were lowered or raised by 8 degrees Celsius (16 degrees Celius range for night temperature) for the remainder of the trials. Respiration increased only 20 to 46% for each 10 degrees Celsius rise in temperature (total respiration Q 10 of between 1.2 and about 1.5), and that sensitivity did not acclimate even after 20 days of treatment. This change resulted in between 6 and 16% less efficient growth (carbon retention) across the temperature range depending on the species. Differences in efficiency of growth did not result in differences in dry matter gain, however, because of differences in total daily light interception between treatments, but small growth differences would be likely in either longer periods of time or more uniform light environments. These findings indicate that whole-plant respiration of rapidly growing plants has a small sensitivity to temperature, and that sensitivity does not change among the species tested, even after 20 days of treatment. Finally, the magnitude of temperature effect on whole plants suggests that the role of respiration as a carbon loss of the plant system is overstated in most research and models, especially in rapidly growing plants. This work suggests that maintaining a cooler night temperature than day temperature does not help or hurt plants, and night time respiration has a minimal effect on plant productivity. This information should help anyone who grows plants including growers, who can lower costs with cool night-time temperatures, and researchers, who can simplify interpretation of results by not altering the thermoperiod for their research.

Technical Abstract: Carbon gain depends on efficient photosynthesis and adequate respiration.  The effect of temperature on photosynthetic efficiency is well understood.  In contrast, the temperature response of respiration is based almost entirely on short-term (hours) measurements in mature organisms to develop Q-10 values for maintenance and whole-plant respiration.  These Q-10  values are then used to extrapolate across whole life cycles to predict the influence of temperature on plant growth.  In this study, night temperature in young, rapidly growing plant communities was altered from 17 to 34 degrees Celsius for up to 20 days.  The day temperature was maintained at 25 degrees Celsius. Carbon dioxide gas-exchange was continuously monitored in 10 separate chambers to quantify the effect of night-temperature on respiration, photosynthesis, and the efficiency of carbon gain (carbon use efficiency).   Respiration increased only 20 to 46% for each 10 degrees Celsius rise in temperature (total respiratory Q-10 of between 1.2 to about 1.5).  This change resulted in only a 2 to 12% change in carbon use efficiency, and there was no effect on cumulative carbon gain or dry mass.  No acclimation of respiration was observed after 20 days of treatment.  These findings indicate that whole-plant respiration of rapidly growing plants has a small sensitivity to temperature, and that sensitivity does not change among the species tested, even after 20 days of treatment.  Finally, our results support respiration models that separate respiration into growth and maintenance components.