Figure 2.

(a) Anatomy of a chlorotic pine needle showing autofluorescent structures. The red fluorophore is residual chlorophyll in the transfusion tissue. Sequential excitation at 355, 488, and 633 nm with corresponding emission at 400–500 (blue), 500–570 (green), and 650–750 nm (red). Scale bar = 200 µm. (b) Autofluorescence of a healthy needle using spectral imaging to more precisely detect the green ferulate fluorescence in the phloem tissue and to exclude chlorophyll fluorescence. Excitation 355 nm with emission at 420–460 nm (blue) and 495–550 nm (green). Scale bar = 100 µm. (c) Autofluorescence of a healthy needle using blind spectral unmixing to more precisely detect the green ferulate fluorescence in the phloem and to exclude chlorophyll fluorescence. Excitation 355 nm with emission at 400–800 nm. Scale bar = 100 µm.