Applications of chlorophyll fluorescence for stock quality assessment with different types of fluorometers

Abstract

We demonstrate some stress detection and stock quality applications of fluorescence to conifer seedlings using two types of fluorometers: an integrating fluorometer (IF) 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 (r2> 0.90 with visible injury). Fv/Fvm from the IF was highly correlated with quantum yield (φ) from the EARS (r> 0.94). The relationship betweenφ p and visible injury in white spruce was strongest whenφ p was measured at low light levels. Freezing-stressed Sitka spruce (Picea sitchensis [Bong.] Carr.) seedlings also showed decreased φ. Values of φ in the dark were about 20? higher than in the light (400λ mol m-2s-1PPFD, photosynthetic photon flux density); but the two φs were highly correlated (r 2= 0.99). Heating Sitka spruce seedlings showed that φ decreased linearly as duration at 40x00B0;C increased. Although there was some recovery inφ 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 Fv/Fmdiffered. Moderate stress was detected by the PAM as higher qNand lowerφ p, and by the IF as delayed FtM2. For severe stress, the PAM detected lower Fv/Fm, qN, qP, and φ, and FM2disappeared 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. NOTE: All parameters, abbreviations and symbols, unless specifically defined in the text, are defined in Table 1. Endorsement or rejection of any particular fluorometer is not implied.