The measure of biological age in plant modular systems

Abstract

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.

Plant Architecture: A Dynamic, Multilevel and Comprehensive Approach to Plant Form, Structure and Ontogeny

“…Under given conditions, the duration of these phases may be more or less fixed for a species (Wareing, 1959;Zimmerman, 1972;Hackett, 1985) and it is thus possible to identify a mean specific age in which a plant will be able or unable to express a particular feature. According to plant species, this 'chronological' (Ritterbusch, 1990) or 'calendar' (Gatsuk et al, 1980) age may be expressed in days or years after germination and it is known that it may be strongly modified by environmental factors (Doorenbos, 1954;Zimmerman, 1972;Gatsuk et al, 1980). At a given moment, a plant may thus be characterized not only by its 'chronological' or 'calendar' age but also by a set of biological criteria that indicates its 'stage' of development variously referred to as 'biological age' (Levin, 1966;Roloff, 1989;Gleißner, 1998), 'physiological age' (Robbins, 1957;Schaffalitzky de Muckadell, 1959;Grubb, 1977), 'ontogenic age' (Passecker, 1977) or 'age state' (Uranov, 1975;Gatsuk et al, 1980).…”

A temporal and morphological framework for flower development inAntirrhinum majus

“…In plants this can be most naturally done using plastochron number or index, which reflects time if plastochron number is constant throughout development (Erickson and Michelini 1957). We adopt this approach here, as it provides a strict temporal framework for mapping developmental events and growth patterns (Ritterbusch 1990a(Ritterbusch , 1990b; Ritterbusch and Wunderlin 1989).…”

Stolon growth and branching in Glechoma hederacea L.: an application of a plastochron index

“…In this application, a plastochron was the unit of biological time (Ritterbusch, 1990) equal to the interval between the moment when an attached ramet reached a particular stage of development, and the moment when the next attached ramet along the stolon reached the same stage. The plastochron index (PI) was equal to the number of ramets along the primary stolon.…”

“…Instead of using an genetic (Bell & Tomlinson, 1980) or responsive anthropogenic time scale, it may be preferable to (Grime, Crick & Rincon, 1986; study the development of morphology relative to a 1987a-c). In either case, variations in clone struc-biological time scale, such as the plastochron index ture may be described quantitatively in terms of (PI) (Erickson & Michelini, 1957; Maksymowych various parameters of growth (Harper & Bell, 1979;1973;Ritterbusch, 1990). The plastochron index Hutchings & Slade, 1988).…”

“…However, it is best to assume that p does not correlate perfectly with time, and use it as an ordinal, which specifies various intermediate stages of development within each plastochron. Even if only condition ( 1) is approximately met, the PI will have a good correlation with time, because the bulk of the PI is usually n. When environmental conditions change, conditions (1) and (3) will be broken, but development will probably be better correlated w-ith the plastochron index than the astronomic clock (Vendeland et al, 1982;Ritterbusch, 1990). PI does not need to be linearly correlated with time for most ecological applications.…”