Invivo chlorophyll fluorescence as a possible indicator of the dormancy stage in Douglas-fir seedlings

Abstract

Invivo chlorophyll fluorescence and photosynthetic pigment contents of current-year needles from five populations of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco, var. menziesii Franco and var. glauca (Beissn.) Franco) were monitored at 3- to 4-week intervals over 2 years. The results were compared with the reported stage of seedling dormancy to ascertain whether this technique would be suitable for indicating dormancy status. Minimum values of fluorescence-induction parameters, indicating winter photosynthetic inactivation, were observed during the coldest period. The lower the temperature and the greater the irradiance, the greater the apparent inactivation. An increase in chlorophyll a to chlorophyll b ratios and a decrease in total chlorophyll to carotenoid ratios, indicating a relative increase in protective carotene pigments, was associated with this period. Maximum values for the fluorescence parameters were observed during periods of maximum growth. It appears that a rapid and inexpensive means of screening for Douglas-fir's dormancy status could be developed using invivo chlorophyll fluorescence analyses.