Chlorophyll fluorescence and vegetative propagation of Taxus

Chlorophyll fluorescence over the course of stem cutting propagation was ex amined in 10 cultivars of Taxus xmedia (Taxus baccata L. x T. cuspidata Sie b. & Zucc.), including 'Brownii', 'Dark Green Pyramidalis', 'Dark Green Spr eader', 'Densiformis', 'Densiformis Gem', 'Hicksii', 'L.C. Bobbink', 'Runya n', 'Tauntoni', and 'Wardii'. The fluorescence value measured was the ratio of variable over maximum chlorophyll fluorescence (F-v/F-m). This value re flects the maximum dark-adapted photochemical efficiency of photosystem II (PSII) reaction centers involved in photosynthesis and is an indirect measu re of plant stress. The objective of this study was to examine F-v/F-m as a method for stock plant selection and for monitoring rooting progress of va rious cultivars. F-v/F-m varied significantly (P less than or equal to 0.05 ) among cultivars, initially and over time. However, there was significant overlap among some cultivars. The F-v/F-m decreased dramatically during col d storage, but usually returned to original levels after several weeks in t he propagation beds. This appeared to be a reflection of the reduction of w ater stress as the cuttings formed roots. Initial stock plant F-v/F-m was n ot correlated (P less than or equal to 0.05) with rooting percentage, root number, root dry weight, or root length, indicating that F-v/F-m is not a r eliable indicator of stock plant rooting potential. Visual assessment is ju st as reliable.