The effects of white mistletoe on growth and development parameter of the cilicican fir

Mistletoe is a hemi-parasitic plant that affects the growth and development of its host in many ways. The objective of this study is to determine and evaluate the effects of white mistletoe (Viscum album L. subsp. abietis (Wiesb.) Abromerit) on the long-term growth and development dynamics of Cilician Fir (Abies cilicica (Antoine & Kotschy) Carrière) in relation to varying mistletoe infection severity. To do this, needle samples were taken from uninfected branches of infected and uninfected trees, and morphological, anatomical, stomatal traits and photosynthetic pigment contents of needles were measured. Increment cores were taken from the mistletoe infected and uninfected trees, and anatomical traits were measured and counted for each annual ring for the last 20 years of growing period. In addition, early wood, late wood and annual ring width were measured, and basal area increment was calculated for each annual ring for the same period. The results indicated that morphological, anatomical and stomatal traits and chlorophyll content of needles decreased with increasing infection severity. Reduced dimensions in anatomical traits were only evident in needles from moderate and severe infection classes, while chlorophyll content decreased in only severely infected trees. Radial lumen diameter of early and late wood tracheid decreased with increasing infection severity. Double wall thickness of early and late wood tracheid increased in the lightly and moderately infected trees and decreased in severely infected trees. The results also indicated that radial growth of trees were affected significantly by the mistletoe infection. The magnitude of these effects increased with the increasing infection severity, especially during the last ten years of growing periods of mistletoe-infected trees.