Circadian rhythm of photosynthesis inKappaphycus alvarezii(Rhodophyta): independence of the cell cycle and possible photosynthetic clock targets

Abstract

Various processes in the output pathway of the circadian clock are thought to act as important clock targets resulting in the circadian rhythms of photosynthesis observed in various algae. Examples of such processes are synchronization of the cell cycle, pigmentation, and light or dark reaction of photosynthesis. The newly detected, robust photosynthetic circadian rhythm in the red macroalga Kappaphycus alvarezii was investigated in more detail with respect to rhythmically changing components within the photosynthetic apparatus. The following major results were obtained; (1) The growing tips of Kappaphycus (0 -2 cm) were found to exhibit a diurnal and circadian rhythm of nuclear division like many other algal species, (2) The circadian photosynthetic rhythm was apparent in the actively growing and dividing tip portions (0 -2 cm) as well as in older portions (2 -4 cm) with little remaining mitotic activity. The Kappaphycus rhythm seems therefore to be independent of the cell cycle, at least in the older portions of the thallus, (3) During real (L : D cycle) or subjective (LL) dark phases, net photosynthetic capacity (P max ) dropped drastically in young (tip) parts of the thallus, and a, the 'light affinity' parameter, decreased likewise. The net result of these two changes was an increase in the light saturation point, E k . Dark respiration did not change rhythmically from one circadian maximum to the next circadian minimum. DF/F m ' dropped during real and subjective night phases, while non-photochemical quenching (NPQ) increased. Low temperature (77 K) emission spectra with an excitation wavelength of 580 nm exhibited a larger increase of the 720 : 685 nm as well as the 720 : 696 nm emission quotients compared with spectra at 440 nm excitation for samples harvested in the middle of the subjective dark phase indicating changes in energy trapping from the phycobilisomes to the photosystems.

The effect of irradiance and temperature on the photosynthesis and growth of a cultivated red alga Kappaphycus alvarezii (Solieriaceae) from Vietnam, based on in situ and in vitro measurements

“…Hence, physiological characteristics of this species including growth, photosynthesis, and carrageenan yields have also been extensively reported through field and laboratory studies over the past three decades (e.g., Glenn and Doty 1990;Hurtado-Ponce et al 2001;Muñoz et al 2004;Wakibia et al 2006;Hayashi et al 2007). Indeed, a number of previous studies have also contributed to elucidating the photobiology of this species, especially in tropical waters under intense photosynthetic active radiation and UV radiation (Ganzon-Fortes et al 1993;Aguirre-von-Wobeser et al 2001;Granbom et al 2001;Jacobsen et al 2003;Schubert et al 2004Schubert et al , 2006Schmidt et al 2010;Reis et al 2011).…”

Light and temperature effects on photosynthetic activity of Eucheuma denticulatum and Kappaphycus alvarezii (brown and green color morphotypes) from Sulawesi Utara, Indonesia

“…Due to their economic value, these carrageenophytes have been subjects of extensive research, including studies on the ecophysiology of these species, particularly on determining their photobiology under intense photosynthetically active radiation (PAR) and ultraviolet (UV) radiation (Aguirre‐von‐Wobeser et al ; Granbom et al ; Jacobsen et al ; Schubert et al , ; Schmidt et al ,), as well as on clarifying optimum farming conditions for maximum production and control of epiphytic filamentous algae (EFA; Borlongan et al , ).…”

Dark survival in a warming world

“…Strong circadian rhythms in oxygen production in continuous white light, expression of light harvesting complex genes and nuclear division have all been demonstrated. Dark respiration has not been found to vary with circadian rhythm, but effective quantum yield (DF/F m 0 ) and non-photochemical quenching have [39]. The regulation of cellular processes such as photosynthesis by circadian rhythms is thus an important short-term adaptive response to daily darkness.…”

“…It is thought that circadian rhythms provide an anticipation of environmental change (e.g. in light), which provides an adaptive advantage [39]. Strong circadian rhythms in oxygen production in continuous white light, expression of light harvesting complex genes and nuclear division have all been demonstrated.…”