C‘lKOADIAN PER1OI)ICITI f W IN PHYTOPLANKTON
349
blage ”, but t91ie alternntive hypothesis of an entrainment by nutrient
concentrations in t h e environmont wiis not’ discarded.
It woiild be outside both thc. niithor’s competence und the scope
of thiH rcview to rtllnte in dctriil the interniil mc~chnnisms of the photosynthetic periodicity, which i N ]tot, i L mctttmr of plnnktology, but rather
physiology imtl biochcrnistry : iimong the current problems are, for
inetuncc., whcthnr C:O,-fixing renct>ions of photoRyntheRi8 (ribulosediI)hosphocitr~)oxylrlsu and other enzymo assays) or light reactions
itre concerned (Hweeney, 1905, I !Wb ; Hellebu~t et nl., 1967 ; Brown
pt a/., 1972 ; tZush and Swtbeney, 1972 ; Wiilt,h(lr and Edmunds, 1973).
Homc other considcriitions ilre ivportd in Sournia (1973).
( ’. I triplications for prirnnr!/ pro(luc&ion mensurement.s
‘l’ha cwiticnoc~ that photosynthetic capitcity, either per unit volume
of seii water. or per cell or per unit, of chlorophyll a, varies up to ten-fold
from diiy to night htw n considerable bearing on the measurement of
primnry production in light incubators. Citn a standard time of sampling
be estitbliahecl? How mtLy values originating from various times be
coml)aretf? \\‘hat is daily production! Not only the I4C and oxygen
methods, but also indirect apprortches such as the “ chlorophyllrtditition ” mothod (Ryther and Yentmh, 1057) are concerned.
Unfortxmatcly, these questions, however fundamental they may
be, cannot he mswercd today. Although the photosynthetic rhythm
is largely endogenous, it evidently depends also on a number of factors
the influence of which is open to investigation, namely : light (amount,
composition iind daylength), nutrients, taxonomic position, experimental proccdure and others. The t,iming of the cycle may vary (me
rtbove) ant1 its rimplitude i H not, rdeted to tlaylength only (unexplained
v;triability is mentioned hy New house, I968 rind .Jitts, 1969). Thus, as
stilted alrcndy for several praincterfi in the present review, no simple
modcl ciin bc rtpplied incliscrimintttcly to rill caxes.
AH for the ~umpliiig time, 1)oty (.I aE. (1967) made the following
choice. ‘l’lieir die1 curve (which is ntypical, by the way: see above)
outs the niciin hourly production line a t two points, just after sunrise
Itrid just before sunset. Either of them, or prcferiibly the first bne, may
be used as n reference time sinco hourly production is then just one
twenty-fourth of daily production. Nevertheless, the authors note
that ” the relntionships can be expected to change with different techniques, populntions, seiwons and settings ” . . . which Newhouse (1967)
proves to btb true : the intersect,ion points obtsined sirnilarly for imothcr
owan area were f h n d eidicr and later rcspectively.
fnsteud of wing a given standard tirrte, some range of samltling
349
blage ”, but t91ie alternntive hypothesis of an entrainment by nutrient
concentrations in t h e environmont wiis not’ discarded.
It woiild be outside both thc. niithor’s competence und the scope
of thiH rcview to rtllnte in dctriil the interniil mc~chnnisms of the photosynthetic periodicity, which i N ]tot, i L mctttmr of plnnktology, but rather
physiology imtl biochcrnistry : iimong the current problems are, for
inetuncc., whcthnr C:O,-fixing renct>ions of photoRyntheRi8 (ribulosediI)hosphocitr~)oxylrlsu and other enzymo assays) or light reactions
itre concerned (Hweeney, 1905, I !Wb ; Hellebu~t et nl., 1967 ; Brown
pt a/., 1972 ; tZush and Swtbeney, 1972 ; Wiilt,h(lr and Edmunds, 1973).
Homc other considcriitions ilre ivportd in Sournia (1973).
( ’. I triplications for prirnnr!/ pro(luc&ion mensurement.s
‘l’ha cwiticnoc~ that photosynthetic capitcity, either per unit volume
of seii water. or per cell or per unit, of chlorophyll a, varies up to ten-fold
from diiy to night htw n considerable bearing on the measurement of
primnry production in light incubators. Citn a standard time of sampling
be estitbliahecl? How mtLy values originating from various times be
coml)aretf? \\‘hat is daily production! Not only the I4C and oxygen
methods, but also indirect apprortches such as the “ chlorophyllrtditition ” mothod (Ryther and Yentmh, 1057) are concerned.
Unfortxmatcly, these questions, however fundamental they may
be, cannot he mswercd today. Although the photosynthetic rhythm
is largely endogenous, it evidently depends also on a number of factors
the influence of which is open to investigation, namely : light (amount,
composition iind daylength), nutrients, taxonomic position, experimental proccdure and others. The t,iming of the cycle may vary (me
rtbove) ant1 its rimplitude i H not, rdeted to tlaylength only (unexplained
v;triability is mentioned hy New house, I968 rind .Jitts, 1969). Thus, as
stilted alrcndy for several praincterfi in the present review, no simple
modcl ciin bc rtpplied incliscrimintttcly to rill caxes.
AH for the ~umpliiig time, 1)oty (.I aE. (1967) made the following
choice. ‘l’lieir die1 curve (which is ntypical, by the way: see above)
outs the niciin hourly production line a t two points, just after sunrise
Itrid just before sunset. Either of them, or prcferiibly the first bne, may
be used as n reference time sinco hourly production is then just one
twenty-fourth of daily production. Nevertheless, the authors note
that ” the relntionships can be expected to change with different techniques, populntions, seiwons and settings ” . . . which Newhouse (1967)
proves to btb true : the intersect,ion points obtsined sirnilarly for imothcr
owan area were f h n d eidicr and later rcspectively.
fnsteud of wing a given standard tirrte, some range of samltling