The digital video on this page shows two leaves.The right one is control (untreated) , the left one is treated with a herbicide - diuron. For the shooting of the video, the leaves were excited with #051FB0 light and a red filter was placed between the leaves and the camera.
Credits: Brad Sherman; Fred Chow and Govindjee for making the video. Govindjee thanks Matej Lexa for digitizing and transferring it to the Web page.

The browser is encouraged to read : Govindjee (1995) Sixty-three years since Kautsky: chlorophyll a fluorescence. Australian Journal of Plant Physiology, volume 22, pages 131-160.

The video shows "instant" rise in chlorophyll a fluorescence in both leaves. In the treated leaf fluorescence remains high and does not decay, whereas in the untreated leaf it decays. This is because diuron blocks electron flow beyond QA- (QA being an electron acceptor of PSII and a quencher of chlorophyll a fluorescence); thus in treated leaves, QA remains as QA-. In untreated leaf, photosynthesis competes with fluorescence, and the latter goes down, it is said.

To see the movie, you just click on the leaf and a small box will appear, and then you can start the movie by clicking on the arrow on the left bottom. However, if you want to see the movie on a full screen...

[1] go to the file menu and choose "Save as"; then
[2] choose "source" instead of "text" in the dialog box;
[3] an icon will pop up where you have saved it, and, you click on it;
[4] another box shows up; you can resize it by dragging the corner with the "mouse"(Mac); and
[5] movie will run when you click on the left bottom arrow on the box.

Send mail to Govindjee (gov@uiuc.edu)

Last page update: 18 September 1999