APPLICATIONS OF CHLOROPHYLL FLUORESCENCE FOR STOCK QUALITY ASSESSMENTWITH DIFFERENT TYPES OF FLUOROMETERS

We demonstrate some stress detection and stock quality applications of fluorescence to conifer seedlings using two types of fluorometers: an integrating fluorometer (TF) for laboratory use, and two field-portab le pulse-modulated instruments, the EARS-PPM (EARS) and PAM-2000 (PAM) . Freezing tests showed that as temperature decreased, the IF and EARS detected decreased fluorescence in white spruce (Picea glauca [Moench .] Voss) seedlings (r(2) >0.90 with visible injury). Fv/F-m from the I F was highly correlated with quantum yield (phi p) from the EARS (r >0 .94). The relationship between phi p and visible injury in white spruc e was strongest when phi p was measured at low light levels. Freezing- stressed Sitka spruce (Picea sitchensis [Bong.] Carr.) seedlings also showed decreased phi p. Values of phi(p) in the dark were about 20% hi gher than in the light (400 mu mol m(-2) s(-1) PPFD, photosynthetic ph oton flux density); but the two phi ps were highly correlated (r(2)=0. 99). Heating Sitka spruce seedlings showed that phi p decreased linear ly as duration at 40 degrees C increased. Although there was some reco very in phi p, after 5 days, it was a good indicator of subsequent gro wth. Desiccation tests showed that the PAM and IF both detected water stress in jack pine (Pinus banksiana Lamb.) seedlings but the values f or F-v/F-m differed. Moderate stress was detected by the PAM as higher q(N) and lower phi p, and by the IF as delayed Ft(M2), For severe str ess, the PAM detected lower F-v/F-m, q(N), q(p), and phi p, and F-M2 d isappeared from IF curves. Gross photosynthesis (Gp), measured by the EARS, can be used as be a quick estimator of net photosynthesis (P >0. 90), but its use as an estimator of seedling quality requires further study.