Architectural Model and Leaf Water Feature of Taxus yunnanensis under Heterogeneous Light Condition

The branching pattern and leaf water feature of Taxus yunnanensis in different light environment were studied in Jingdong of Yunnan Province. The results showed that the architectural model was modified plastically in response to different light conditions, the leaf water feature also has some differences. T. yunnanensis had great stature and wide crown in theses areas where the light is sufficient, the crown fullness ratio was 0.97(almost double those under canopy). The average overall bifurcation ratio in full light environment was 8.57, it was significantly bigger than 6.40 of gap and 4.81 of under canopy, some other architectural parameters such as length of the first order branch, branch angle and leaf angle had the same trend. The leaves displayed significant differently in various light environments, the leaf number of branch in full light was 2.77 times of that in gap and 6.88 times of that under canopy, but all of them had the biggest amount of leaves distributed at the first-order branches. The water saturation deficit increased with the continuous weakening of light intensity, while the tissue density, relative water content and ratio of dry weight to fresh weight reduced with the tapering off of light. It indicated that the leaf’s ability of combating drought, retaining water and resisting water stress increased with the increase of the light intensity. These indicated that T. yunnanensis made some necessary changes in morphological and physiological aspects in order to accommodate it to the change of light environment.