Effects of experimental warming on net photosynthetic rate of Quercus variabilis seedlings

This study was conducted to investigate the effects of experimental warming on net photosynthetic rate of Quercus variabilis seedlings. One-year-old Q. variabilis seedlings were planted in 1m x 1m plots (n=4) in April 2010 and warmed with infrared lamps. Air temperature in the warmed plots was 3°C higher than that of control plots. Net photosynthetic rate was measured using the Handheld Photosynthesis System (CI-340, CID Bio-Science, USA) in May and July 2012. Net photosynthetic rate (μmol CO2 m-1 s-1) was significantly higher in warmed plots (6.24±0.60) than in control plots (10.22±0.98) in May, 2012 whereas there was no significant difference between warmed plots (14.84±0.60) and control plots (15.43±0.75) in July. Higher net photosynthetic rates of warmed plots in May might be caused by advanced leaf unfolding [Han et al., unpublished data; Jo et al., 2011]. However, there was no difference in net photosynthetic rate derived from saturation of chlorophyll contents in July, 2012 [Jo et al., 2011]. Previous studies reported increases in photosynthetic rate, growing season length and plant growth under warming [Jo et al., 2011; Yin et al., 2008]. In a few cases, photosynthesis was not altered by warming treatment because of photoinhibition [Yin et al., 2008]. To examine the effect of changes in physiological traits on seedling, long-term and multi-factor studies are needed.