Aspects of the Aging Process in Cambium and Xylem

The aging processes in a living tree are of a very complex nature; they occur at different time intervals and in different dimensional spaces. The aging processes within a Vegetation period are most obvious in the leaves: the swelling bud develops into young, pale leaves in spring, which grow to füll size and obtain a firmer epidermis. After weeks and months they become discoloured after the first early frosts in autumn; the aging process, beginning when the leaves develop, gradually comes to a standstill, necrobiosis sets in and takes a rapid course. In the same space of time, cambium and xylem have also undergone an aging process which, however, is a process that will continue after the winter rest period and after the resumption of Vegetation activity. Cambium and xylem thus age both with the rhythm of unit time and the integral passage of time. — While there is no lower limit to unit time, it can at most comprise a period of Vegetation; long-term development is unlimited. In the measurable ränge the most aged trees are over 4,000 years old, äs determined on Pinus pinaster trunks of a virgin pine forest in the higher regions of Arizona. However, this limit is entirely accidental and applies only unilaterally to the group of ring forming trees of temperate climatic zones. The biological phenomenon of the timelessness of organisms or organs capable of dividing thus becomes decisive for the individual age of tree: if the aging process is not subject to qualitative modifications äs in the above example of the leaves, necrobiosis will at best involve certain tissues and not the individual äs such. Individuais in which the aging process occurs only in the quantitative respect lose their age, they become timeless. Life äs such is timeless; aging and death are fixed points in life due to environmental circumstances which do not äs such correspond to its basic concept. However, of the more highly organized organisms, only individual tree relics are witnesses to this unbroken vitality.