Fluorescent light-independent computer-assisted imaging of shape changes and movements of Arabidopsis plants : with digital cameras and infra-red light

A high pass cut-off filter (850 nm) installed in the cameras eliminates fluorescent light (up to 750 nm) before reaching the image sensor. Infrared (IR) Light Emitting Diodes (LED at 950 nm) provide the constant source of abject (plants or part of them) illumination. With the system described, an image has a resolution of 582 x 752 = 437664 pixels with 256 gray levels and can be acquired/treated each second by a computer. Tests of performance show that a very small leakage of fluorescent light can occur (~0.48%) when a piece of paper covering almost the full range of gray levels (0-255) was examined, whereas no leakage was observed when objects were contrasted. No apparent biological effect was observed with IR, as inferred by the typical etiolated aspect of Arabidopsis seedlings germinated in the absence of fluorescent light. In the same plant, a clear circadian rhythm is observed with the cotyledon movement. However, leaf surface kinetics examined during 3 1/2 days in adult plants cultivated in L:D (12:12 h) displayed a more complex "behavior" of growth and movements.