Detecting leaf necrosis and branch dieback of transplantation-shocked kousa dogwood trees by thermography Fei W ANG*, Haruhiko Y AMAMOTO**, Yasuomi IBARAKI **, Kiyoshi I WAYA **, Hisashi Y OSHIKOSHI **, and Naru T AKAYAMA ** *The United Graduate School of Agriculture Science, Tottori University **Faulty of Agriculture, Yamaguchi University Abstract Leaf necrosis and branch dieback of the newly transplanted dogwood trees triggered by the prolonged dried period and sudden rise in temperature was observed in the study. Attached and detached leaves and branches were detected by a thermo infrared camera under the conditions including outdoor envi- ronment, indoor window sunlight and incandescent light. Different thermo imaging characteristics were found between necrotic part and living part of both leaves and branches. The detection of the outdoor attached leaves indicated higher temperatures at the necrotic part than living part, seemingly being attributable to the high water content and transpiration cooling effect in the living part. However, the detached leaves change their temperatures at necrotic part faster than that of living part， largely due to the lower water content. Significantly amplified variation of imaging temperature between the live and dead parts of detached leaves and branches during the heating and cooling process indicated that there was potential to detect the leaf necrosis and branch dieback by viewing the temperature fluctuation of Kousa dogwood ( Cornus kousa) trees with thermography. Key words: Amplified image temperature, Branch dieback, Kousa dogwood, Leaf necrosis, Ther- mography, Transplanting shock. Received; February 26, 2009. Accepted; October 6, 2009. 1. Introduction Water is essential for life and constitutes a large part of the fresh weight of most herbaceous plants. In the complicated architecture of woody plants, over 50％ of the fresh weight is also made of water (Kramer, 1983). Under extreme water stress conditions, many of them can survive the lethal desiccation at expense of partial organs, such as abscission or death of leaves or branches (Orshan, 1954, 1989; Addicott, 1973, 1982; Kramer, 1983; Kozlowski, 1973, 1976; Günthardt-Goerg and Vollenweider, 2007), although significant plasticity and diversity appeared among plant species. Kousa dogwood (Cornus kousa) is a showy landscape tree species with slightly swollen nodes and opposite leaves and branches at node positions. During serious water stress, leaf necrosis is often occurred on leaf tip and margins of them and the branch dieback symptoms are also initialed from top of their crown. All of these become the foundation for distinguishing the dead parts from the living parts of them. Water, with larger specific heat capacity, latent heat of melting and evaporation value (Fitter and Hay, 2002), is often used as a coolant in normal human lives. The transpiration cooling effect in plants is also a process involving excessive energy dissipation. The existence of water caused the temperature variation of many trees more gentle than that of air. Their transpiration system is mainly responsible for keeping temperature below the injurious levels under direct sunshine. In a typical experiment, it was estimated that about 75 ％ of absorbed energy was used to evaporate water in transpiration (Thomas et al ., 1973) to avoid damage from excessive light or heat energy. The temperature of soil water covered by crown is often lower than air temperature in summer clear days. During the hottest summer days, a temperature difference around 15-20 ℃ between the deep layer soil and air can be expected. Full Paper J. Agric. Meteorol. (農業気象) 66 (2): 81-90, 2010 81