Assessment of Photosynthetic Function by Analyzing Dynamic Change in Chlorophyll Fluorescence Intensity Induced by a Pulsed Pressure Reduction

Research Project

Project/Area Number	21688018
Research Category	Grant-in-Aid for Young Scientists (A)
Allocation Type	Single-year Grants
Research Field	Agricultural information engineering
Research Institution	Ehime University
Principal Investigator	TAKAYAMA Koutaro Ehime University, 農学部, 講師 (40380266)
Project Period (FY)	2009 – 2010
Project Status	Completed (Fiscal Year 2010)
Budget Amount *help	¥22,230,000 (Direct Cost: ¥17,100,000、Indirect Cost: ¥5,130,000) Fiscal Year 2010: ¥3,380,000 (Direct Cost: ¥2,600,000、Indirect Cost: ¥780,000) Fiscal Year 2009: ¥18,850,000 (Direct Cost: ¥14,500,000、Indirect Cost: ¥4,350,000)
Keywords	農業工学 / 植物応答 / 生体情報計測 / 植物診断
Research Abstract	We tried to develop a chlorophyll fluorescence imaging system to measure the mesophyll conductance without touching the plant body. Initially, we provided that the mesophyll conductance can be expressed with a relative index that is defined as the reciprocal of the response time of chlorophyll fluorescence emission to a rapid reduction of air pressure around the photosynthesizing leaf. A mature tomato leaf attached to the plant was fixed in the transparent acrylic leaf chamber with the inner size of 100 ml and acclimated to light (provided by blue LED) condition for stable photosynthesis. The chamber was hermetically closed and the air inside the chamber was immediately sucked Mby a manually powered pump. The air pressure inside the chamber decreased from 101.3 kPa to 50.7 kPa within 3 seconds and kept the air pressure less than 49 kPa for 10 seconds. During this procedure, the chlorophyll fluorescence intensity emitted by the leaf was continuously measured with the chlorophyll fluorescence imaging system at a frame rate of 13 fps. The response of chlorophyll fluorescence emission with the prompt reduction of air pressure was quite rapid and the chlorophyll fluorescence intensity increased within 0.05 second after the reduction of air pressure. Hence, we concluded that it is impossible to quantify the mesophyll conductance with this measurement systems and hypothesis. On the other hand, we found that the developed chlorophyll fluorescence imaging system and measuring method can be used to measure the photosynthetic rate. The Mchlorophyll fluorescence intensity increased just after the reduction of air pressure and reached to a peak at about 3 seconds after the reduction of air pressure. The height of the peak showed a strong correlation with the photosynthetic rate measured under different CO_2 concentrations.