Untersuchungen zur Sproßvariation der Cupressaceae: 1. Nachweis immerspaltender Periklinalchimären

Abstract

The frequent appearance of white sports in 11 cultivars of Cupressaceae is conditioned histogenetically. Green branches are white-green periclininal chimeras. White sports originate by reduplication of L 1 . The possibility for such a development ia anatomically contained in all cultivars. In all forms the shoot apex consist of two temporarily independent layers. L 1 divides at the sides of the apex only anticlinally. At the top of the apex periclinal divisions in L 1 frequently appear. Axillary buds are initiated without periclinal divisions in L 1 ; they occur on the contrary, at this point regularly in L 2 L 1 and its derivates do not divide periclinally during leaf development. The epidermis of all these cultivars consist in all cases of chlorophyll-deficient tissue. These continually-segregating periclinalw chimeras are relatively stable because of permanent intraindividual natural selection: the buds of the individualized chlorophyll-deficient L 1 -component die off sooner or later. With regard to the direction of cell divisions between homohistical (white-white and green-green) and heterohistical (white-green) shoot apices, no demonstrable differences can be found. Histogenetical results found in chimeras are therefore transferable to corresponding homohistical forms. Dissociations in the direction of the green inner component of chimeras originating spontaneously or provoked by X-ray, were observed for the first time.