Photosynthetic performance of twigs and stems of trees with and without stress

A normal tree leaf is thought to be green (although sometimes reddish in th e so-called "blood"-forms or yellowish in the so-called "aurea"-forms). Tha t also stems can appear greenish or even green is not directly evident. Nev ertheless, photosynthetic activity is to be measured in the cortical tissue s of woody shrubs and trees. The chlorophyll-containing tissue within the s tem is able to use the stem-internal CO2 and the light penetrating the rhyt idome to photoassimilate and produce sugars and starch. It is therefore of interest of how much light penetrates the bark of trees and how much carbon dioxide is necessary for a functioning photosynthesis and even more how se nsitive this bark photosynthesis responds to acidic or otherwise contaminat ed rain or mist, soaking the bark of twigs and stems.