Chlorophyll fluorescence and vegetative propagation of Taxus

Abstract

Chlorophyll fluorescence over the course of stem cutting propagation was examined in 10 cultivars of Taxus xmedia (Taxus baccata L. x T. cuspidata Sieb. & Zucc.), including 'Brownii', 'Dark Green Pyramidalis', 'Dark Green Spreader', 'Densiformis', 'Densiformis Gem', 'Hicksii', 'L.C. Bobbink', 'Runyan', 'Tauntoni', and 'Wardii'. The fluorescence value measured was the ratio of variable over maximum chlorophyll fluorescence (Fv/Fm). This value reflects the maximum dark-adapted photochemical efficiency of photosystem II (PSII) reaction centers involved in photosynthesis and is an indirect measure of plant stress. The objective of this study was to examine Fv/Fm as a method for stock plant selection and for monitoring rooting progress of various cultivars. Fv/Fm varied significantly (P ≤ 0.05) among cultivars, initially and over time. However, there was significant overlap among some cultivars. The Fv/Fm decreased dramatically during cold storage, but usually returned to original levels after several weeks in the propagation beds. This appeared to be a reflection of the reduction of water stress as the cuttings formed roots. Initial stock plant Fv/Fm was not correlated (P ≤ 0.05) with rooting percentage, root number, root dry weight, or root length, indicating that Fv/Fm is not a reliable indicator of stock plant rooting potential. Visual assessment is just as reliable.