Applications of chlorophyll fluorescence for stock quality assessment with 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-portable 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 IF was highly correlated with quantum yield (phi p) from the EARS (r >0.94). The relationship between phi p and visible injury in white spruce 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% higher than in the light (400 mu mol m(-2) s(-1) PPFD, photosynthetic photon flux density); but the two phi ps were highly correlated (r(2)=0.99). Heating Sitka spruce seedlings showed that phi p decreased linearly as duration at 40 degrees C increased. Although there was some recovery in phi p, after 5 days, it was a good indicator of subsequent growth. Desiccation tests showed that the PAM and IF both detected water stress in jack pine (Pinus banksiana Lamb.) seedlings but the values for 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 stress, the PAM detected lower F-v/F-m, q(N), q(p), and phi p, and F-M2 disappeared 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.