Effect of Temperature on Photosynthesis and Fruit Quality of 'Mihong' Peaches under High CO₂ Concentrations

We investigated the effects of elevated temperatures on the photosynthetic characteristics and fruit quality of the 'Mihong' peach (Prunus persica) under high carbon dioxide concentrations based on climate change scenario RCP 8.5. We simulated three different temperature conditions (control; the average temperature in normal years in Jeonju city, C+3.4 degrees C, C+5.7 degrees C) and 700 mu mol center dot mol(-1) CO2 (expected in the mid-21st century). The average photosynthetic rates were 10.64, 10.21, and 8.18 mu mol center dot m(-2)center dot s(-1) at C+3.4 degrees C, control, and C+5.7 degrees C, respectively. The chlorophyll content in the control and C+3.4 degrees C increased compared to that at the early stage of growth, but that of C+5.7 degrees C decreased rapidly. The fruit weight was the highest for C+3.4 degrees C (158.2 g), followed by C+5.7 degrees C (129.5 g) and the control (127.3 g). The shoot length increased at C+3.4 degrees C and C+5.7 degrees C when compared to the control, and there was no significant difference in the other growth characteristics. The carbohydrate content was the highest at C+3.4 degrees C, and the nitrogen content increased as the temperature increased. Moreover, the C/N ratio decreased as the temperature increased but there was no significant difference. The rate of floral bud differentiation decreased as temperature increased, and that of C+5.7 degrees C was the lowest due to the low C/N ratio, vegetative growth dominance, and early defoliation. Furthermore, the floral bud density was low in the C+5.7 degrees C treatment. These findings indicate that a temperature increase of 5.7 degrees C under 700 mu mol center dot mol(-1) CO2 conditions will negatively affect the physiological response and fruit quality of the early-maturing peach variety 'Mihong,' and yield is expected to decrease in the following year.