Chapter 1: The Characeae Plant

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1.5.4.4 Temperature
Storage temperature can affect germination of characeae (Casanova and Brock 1996), so that
winter germinating species will only germinate after they have been exposed to cues to the
onset of winter. The rate at which characeae germinate can be related to the ‘day-degrees’
they have experienced (Casanova 1994). Some species occur only in tropical regions, others
have a temperate distribution (Casanova 1993) and many populations experience seasonal
changes in biomass (Fernández-Aláez et al.2002).
1.5.4.6 Depth
Characeae are often the deepest inhabitants of lakes (Dale 1986), and there can be a high
diversity of species in individual lakes, zoned in relation to depth (de Winton et al. 1991).
They have been recorded to 30 m in USA (Stross et al. 1995), 15m depth in New Zealand (de
Winton et al. 1991; Casanova et al. 2007) and 12m depth in Tasmanian lakes (T. Dugdale,
personal communication). Classical studies relating characeae distribution to depth have
generally held light attenuation to be responsible for the determining the lower depth limits of
characeae communities (Wood 1950; Spence 1982; Andrews et al. 1984; Vant et al. 1986).
Some species exhibit definite biomass maxima at certain depths (de Winton et al. 1991;
Asaeda et al. 2007), and allocate more biomass to sexual reproduction at shallower depths
than in deeper water (Casanova 1994; Asaeda et al 2007). Depth can influence allocation of
resources to, and therefore the size and morphology of oospores (Boszke and Bociag 2008).
Depth, along with light availability, can affect the development of internodes and shoot
lengths, with thalli collected from deeper water exhibiting elongated internodes and
branchlets compared to thalli collected from shallower parts of the same water bodies
(Asaeda et al. 2007).
1.5.5 Culturing characeae
In many cases characeae can be harvested from the field and introduced into informal culture
with very little effort. Shoots, along with water from their habitat, can be placed in a vessel,
and given adequate light (e.g. on a window-sill; Karling 1924; Casanova and Brock 1996),
will persist, and sometimes grow, for weeks, if not months. Simple aeration of the water
through a bubbler can prevent the proliferation of bacteria and production of anoxic
conditions, a particular problem for species from brackish and saline water-bodies. This
method can provide simple, if undefined, cultures of characeae for experimental purposes.