Fucus development

An extensive literature exists to point out the active role of Ca2+ in many biological processes (17) Jaffe has suggested that this might indeed be of relevance to Fucus development (8). We now show how a number of physical properties of Ca2+ strongly suggest such a role and that these factors lead the way to a number of approximations that yield a simple intuitive model for the spontaneous generation of cellular electrophysiological patterns. 

Schoenwaelder MEA (2002b) Physode distribution and the effects of Thallus Sunburn in Hormosira banksii (Fucales, Phaeophyceae). Bot Mar 45 262-266 Schoenwaelder MAE, Wiencke C, Clayton MN, Glombitza KW (2003) The effect of elevated UV radiation on Fucus spp. (Fucales, Phaeophyta) zygote and embryo development. Plant Biol 5 366-377... 

It has been shown experimentally (8) for some single cell systems, notably the fertilized Fucus egg, that at a certain stage of development transcellular ionic currents spontaneously... 

A complete analysis of a Ca2+ type model for the early development of Fucus has been carried out (5.-7). It was found that early developmental phenomena can be quantitatively described using available Fucus transport and fixed Ca2+ binding site data obtained experimentally. An important feature of this type of calculation is that it provides a framework with which one may integrate a wide range of complex experimental data and sort out which experiments are most crucial. Many detailed... 

Figure 2. Self-organized ionic current loops found both experimentally and theoretically in the single-cell state early development of the egg of the seaweed Fucus.

Patterns (a) and (b) correspond to 1 = 1, 2 pattern symmetries, respectively. The 1 = 1 pattern is the normal course of development for Fucus and is the primary developmental event that sets the direction and sense of the later development that allows for the (leaf, stem) — (root) differentiation. The 1 = 2 patterns also are observed experimentally as occasional birth defects where two roots germinate. 

TDGL Formalism. Our object is to obtain a dynamical equation describing the onset of a pattern. The TDGL method has two main features it (l) identifies a few variables that specify the pattern and (2) develops relatively simple equations for these variables in the limit where the system is not too far from the point of marginal stability. We shall develop these ideas specifically in terms of the Fucus-type theory of the previous section and in particular near conditions wherein the X = 1 disturbance just becomes unstable. 

As pointed out above in regard to the hyperpolarizability effect, the lability of a biopattern is closely related to its stability. Consider, for example, the lability of the Fucus egg polarity in its early development. In the absence of an applied gradient, the equations describing the dynamics of the egg are invarient under a rotation of coordinates about the center o the egg. This implies that if we have a solution of tt e form Y(r,t) then fo any ota ion operation R taking a vector r to a new vector r = Rr, r = Jr, then Y(r, t) is also a solution (state) of the Fucus system. This implies that the state Y(r,t) is only marginally stable as follows. Assume Y obeys the equation... 

In the present problem the imperfect bifurcation theory results in clarifying the close analogy of the development of polarity in Fucus with a ferromagnetic transition. To demonstrate this we multiply (kk) by e3 and let ge s m, aX e2 s t and bE e3 = h. Then (kk) becomes 2 3... 

Typically developing systems are in a situation of dynamical patterning. A bifurcation picture is not relevant unless there is time scale separation thus a TDGL formalism is more appropriate as discussed above in dynamicsl self-organization. We are developing such a theory to study lability in Fucus-like polarization phenomena. 

Strong electric fields and currents have been measured in a number of multicellular systems ranging from Fucus at the two cell state, a Cecropia moth oocyte-nurse cell cyncytum, amphibianand rodent limbs in regeneration and man (8, 22, 28, 3) Thus it is imperative to develop a formulation of multicellular phenomena. 

Larter, R. Strickholm, A. Ortoleva, P. Cell, "A Detailed Model of the Electrical Symmetry-Breaking Transition in Early Fucus Egg Development" (submitted for publication). 

As already discussed for the phytoplankton, the distribution of the phytobenthos is also determined by the sahnity gradient. Therefore, its development is considered separately in the individual Baltic districts. Baltic species of marine origin are ecophy-siologically adapted to the lower salinity. The occurrence of endemic macrophytes is doubted. As data exist already from before 1880, the preindustrial reference conditions can be defined in some areas. In total, 48 out of the 422 listed species have not been found after 1970. This does not necessarily mean that species have disappeared as many of them are small ones which can be easily overlooked. Ten nonindigenous macro-phytobenthic species (e.g., Gracilaria vermiculophylla, Fucus evanescens) invaded the Baltic recently (Chapter 16). 

Jaffe LF (1968) Localization in the developing Fucus egg and the general role of localizing currents. Adv Morphog 1 295-328... 

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