Sung Yung Yoo, Jong Yong Park, Doo Won Lee, Sun-Hee Woo, Tae Seok Ko, Tae Wan Kim

The objective of this study was to find a rapid determination of the air-drying stress of sorghum (Sorghum bicolor L.) leaves using portable chlorophyll fluorescence imaging instrument. To assess the photosynthetic activity of sorghum leaves, an imaging analysis of the photochemical responses of sorghum was performed with chlorophyll fluorescence camera. The observed chlorophyll imaging photos were numerically transformed to the photochemical parameters on the basis of chlorophyll a fluorescence. Chlorophyll a fluorescence imaging (CFI) method showed that the rapid decrease in F_m of leaf was occurred under air-drying stress. Although F_v/F_m ratios values in air-drying stressed sorghum leaves were not changed, all other photochemical parameters such as F_m, F_v, F_p and F_t were lowered after air-drying stress. In air-drying stressed sorghum leaves, it showed to increase in nonphotoquenching (NPQ) and decrease in ΦPSII. Thus, ΦPSII and NPQ were available to determine nondestructively the air-drying stress of sorghum leaves. In our study, it was clearly indicated that the air-drying could be a stress in sorghum leaves. The CFI analysis and its related parameters are applicable as a rapid indicating technique for the determination of air-drying stress.