Influence of Elevated CO₂and Air Temperature on Photosynthesis, Shoot Growth, and Fruit Quality of 'Fuji'/M.9 Apple Tree

Abstract

본 시험은 기후변화의 영향과 관련하여 기온 및 <TEX>$CO_2$</TEX> 농도 상승이 '후지'/M.9 사과나무의 광합성 및 과실품질에 미치는 영향을 알아보고자 지난 4년(2009-2012)동안 시험이 이루어졌다. 처리구들은 'Ambient' (대기온도+대기 <TEX>$CO_2$</TEX> 농도), 'High <TEX>$CO_2$</TEX>'(대기온도+상승 <TEX>$CO_2$</TEX> 농도), 'High Temp'. (상승온도+대기 <TEX>$CO_2$</TEX> 농도), 'High <TEX>$CO_2$</TEX>+High Temp'. (상승온도+상승 <TEX>$CO_2$</TEX> 농도)이었다. 상승온도 처리구들은 대기온도보다 <TEX>$4^{\circ}C$</TEX> 상승시켰고, 상승 <TEX>$CO_2$</TEX> 농도 처리구들은 <TEX>$700{\mu}mol{\cdot}mol^{-1}$</TEX>로 유지하였다. 4년 동안 매년 처리기간은 4월말부터 11월초까지였다. <TEX>$CO_2$</TEX> 상승은 기공전도도와 잎의 엽록체함량(SPAD 계량기 값)을 감소시켰으나, 광합성속도, 세포 내 <TEX>$CO_2$</TEX> 농도(Ci) 및 잎의 전분함량은 증가시켰다. 수체생장에 있어, 기온 상승은 나무당 총 신초수와 총 신초생장량을 증가시켰으나, <TEX>$CO_2$</TEX> 상승은 평균 신초장을 감소시켰다. 과실품질에 있어, <TEX>$CO_2$</TEX> 상승은 착색, 가용성 고형물 함량, 및 에틸렌 발생량을 증진시켰다. 결론적으로, <TEX>$CO_2$</TEX> 농도가 상승되면 생육초기에 사과나무의 광합성속도가 증가되었으나 생육후기에는 <TEX>$CO_2$</TEX> 상승에 따른 광합성속도 증진 효과가 감소되었다. 반면에 기온 상승은 생육초기 광합성속도를 감소시켰으나 생육후기에 광합성속도를 증진시키는 경향이 있었다. <TEX>$CO_2$</TEX>와 기온의 동시 상승은 각 요인에 의한 광합성 감소 정도가 줄어드는 경향이 있었다. This study was conducted to find out the influence of elevated atmospheric <TEX>$CO_2$</TEX> concentrations and air temperature on photosynthesis and fruit quality of 'Fuji'/M.9 apple trees and to investigate these to the effects of climate change during the last four years (2009-2012). The treatments employed were: 'Ambient' (ambient temperature + ambient <TEX>$CO_2$</TEX> concentration); 'High <TEX>$CO_2$</TEX>' (ambient temperature + elevated <TEX>$CO_2$</TEX> concentration); 'High Temp'. (elevated temperature + ambient <TEX>$CO_2$</TEX> concentration); and 'High <TEX>$CO_2$</TEX> + High Temp'. (elevated temperature + elevated <TEX>$CO_2$</TEX> concentration). The elevated temperature plots were maintained at <TEX>$4^{\circ}C$</TEX> higher than ambient air temperature, while the elevated <TEX>$CO_2$</TEX> plots were maintained at 700 <TEX>${\mu}mol{\cdot}mol^{-1}$</TEX>. Annual treatment period was applied from end of April to beginning of November for four years. Results showed that elevated <TEX>$CO_2$</TEX> decreased stomatal conductance and leaf SPAD value, but increased photosynthetic rate, intercellular <TEX>$CO_2$</TEX> concentration (Ci), and starch content of mesophyll tissue. In the vegetative growth, elevated temperature increased total number of shoot and total shoot growth per tree, but elevated <TEX>$CO_2$</TEX> decreased average shoot length. In the fruit quality, elevated <TEX>$CO_2$</TEX> increased soluble solid content, fruit red color, and ethylene production. In conclusion, elevated <TEX>$CO_2$</TEX> increased photosynthetic rate of apples during the early growth, but effect of increased photosynthetic rate due to elevated <TEX>$CO_2$</TEX> was decreased during latter growth stage. Elevated temperature, on the other hand, tended to decrease photosynthetic rate of apples during the early growth, but that tended to increase during latter growth stage. Both elevated <TEX>$CO_2$</TEX> and temperature tended to decrease the degree of decreased photosynthetic rate due to each factor.