caa a22 4500 465821804 CHVBK 20180323112137.0 cr unu---uuuuu 170327e19900601xx s 000 0 eng 10.1007/BF00047548 doi (NATIONALLICENCE)springer-10.1007/BF00047548 Ritterbusch A. Biologisches Institut II, Abteilung Botanik, Albert-Ludwigs-Universität, Schänzlestr. 1, 7800, Freiburg, FRG aut The measure of biological age in plant modular systems [Elektronische Daten] [A. Ritterbusch] Phytomorphology — if concerned with development — often concentrates on correlative changes of form and neglects the aspects of age, time and clock, although the plant's spatial and temporal organisation are intimately interconnected. Common age as measured in physical time by a physical process is compared to biological age as measured by a biological clock based on a biological process. A typical example for a biological clock on the organ level is, for example, a shoot. Its biological age is measured by the biological time unit of a plastochron, which itself is defined by the cyclic-periodic initiation of the leaves. In a controlled environment biological age may replace physical age. However, biological and physical age are not necessarily linearly convertible into each other. In stationary or steady state conditions the repetitive initiation of any organ, unit or "module” of an articulate plant or plant "modular system” may define the biological time unit. A linear — monotonous biological process, e.g. axis elongation, may also define a biological time unit as a certain amount of additional growth, e.g. of length. One may speak of "periodical” and of "continuous plastochron” or, perhaps, of "plastochron” and "rheochron”. A precise measure of biological age is the generalized plastochron index applying to any modular system and module respectively. However, one should be aware that it is based on two clocks, one of them referring to the periodic process of module initiation for counting the integer plastochrons and the other to the continuous plastochron of module growth for the determination of the fraction of one plastochron. The application of the concepts is restricted to phases of stationary or steady state growth and development. In certain cases of non-stationary or non-steady state conditions a normalized-age concept may apply. Kluwer Academic Publishers, 1990 Ontogenesis nationallicence module nationallicence metrical nationallicence relational nationallicence biological nationallicence physical age nationallicence normalized age nationallicence periodical nationallicence continuous plastochron nationallicence plastochron index nationallicence Acta Biotheoretica Kluwer Academic Publishers 38/2(1990-06-01), 113-124 0001-5342 38:2<113 1990 38 10441 https://doi.org/10.1007/BF00047548 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00047548 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Ritterbusch A. Biologisches Institut II, Abteilung Botanik, Albert-Ludwigs-Universität, Schänzlestr. 1, 7800, Freiburg, FRG aut NATIONALLICENCE 773 0- Acta Biotheoretica Kluwer Academic Publishers 38/2(1990-06-01), 113-124 0001-5342 38:2<113 1990 38 10441 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer