1063-0740/04/3005- © 2004
Russian Journal of Marine Biology, Vol. 30, No. 5, 2004, pp. 341–353.
Original Russian Text Copyright © 2004 by Biologiya Morya, Leletkin, Dyukareva, Popova, Skriptsova.
The growth of the algal thallus is commonly consid-
ered a steady increase in size and weight. The growth is
quantiﬁed by measuring the range of variation of the
selected characteristics per unit of time, i.e., by the
absolute increment or absolute growth rate
= , (1)
is the change in the length, area, or weight of
the thallus over the period of observation
. In the
beginning of the last century, another criterion was sug-
gested for comparison of growth rates in individuals of
different sizes. This was relative increment
= , (2)
was the initial value of the selected variable .
Since 1927, the relative increment has commonly
been quantiﬁed by the value that is calculated accord-
ing to the formula
and is referred to as the mean speciﬁc growth rate or
growth rate between the two points of time
However, the application of this measure has certain
limits, since a formal consequence of equation (3) is
that the growth follows the “principle of compound
interest”; i.e., at any given moment of time (
), the rela-
tive growth rate is the same and, consequently,
In the case of nonexponential growth, the speciﬁc
growth rate calculated according to formula (3) “is a
kind of abstraction” (for details, see ).
At certain stages of the life cycle, the size and
weight of macrophyte thalli decrease and
negative values. These changes are not in formal agree-
ment with the deﬁnition of growth. In these cases, the
term “negative growth” is used , as opposed to time
intervals during which thalluses exhibit “positive
0) (termed below as growth).
The growth rate depends on the thallus structure,
rearing, and environmental conditions, as well as on the
size of the specimen . The growth rate of the alga
can change over time even in a stable environment. If
observations cover a long period of time, changes in
can be due to a shift from one developmental stage to
another (for instance, when the reproductive stage fol-
lows the phase of vegetative growth; see ).
Within the duration of one vegetative stage, the
growth rate of macroalgae either remains constant or
changes along with changes in weight. The pattern of
changes in the growth rate over time differs in different
algae, since thalli grow mostly due to cell division in
specialized tissues (meristems), whose relative amount
and position within the thallus vary with species.
Theoretically, growth with a constant speciﬁc
growth rate can occur only if the relative number of
dividing cells in the thallus and the duration of cytoki-
nesis remain the same over the selected time interval.
With a high probability, one can expect these conditions
to be realized in the algae whose growth is due to the
proliferation of nonspecialized cells, which do not form
Changes in Thallus Weight and Size in the Green Alga
under Artificial Conditions
V. A. Leletkin, E. V. Dyukareva, L. I. Popova, and A. V. Skriptsova
Institute of Marine Biology, Far East Division, Russian Academy of Sciences,
Vladivostok, 690041 Russia
Received November 24, 2003
—From August to October 2002, daily measurements of the thallus weight and area were taken in
sporophytes and male and female gametophytes of
at similar developmental phases. The algae
were reared in aquaria at a constant temperature (22
C); illumination was applied for 12h a day at a pho-
tosynthetically active radiation intensity of 400
s). All generations showed a linear increase in the thal-
lus weight and area over time with the same relative daily increment (8 to 15%). Generations differed signiﬁ-
cantly in time to onset of sporogenesis or gametogenesis. The female gametophyte, sporophyte, and male game-
tophyte began to release gametes or spores in 7, 10, and 15 days, respectively. A scheme for the distribution of
cells among age groups is proposed. The scheme seems to account for the linear pattern of thallus growth.
, growth, sporogametogenesis, reproduction.