Temperature responses of ribulose bisphosphate carboxylase and photosynthetic capacity in arctic and tropical phytoplankton

Abstract

When assayed near respective in situ temperatures, ribulose blsphosphate carboxylase (RuBPC) exhibits a greater response to increasing temperature in arctic than in tropical phytoplankton. This was also true when the Arrhen~us activation energy (E,) was compared for a range of intermediate temperatures. This difference in temperature response and E, for RuBPC is consistent with the temperature response of photosynthetic capacity, but is contrary to the general observation that coldenvironment ectotherms (organisms whose internal temperature conforms to that of the environment) have physiological processes with lower E,'s. Analysis suggests that the genotypic adaptation of qualititative enzyme temperature responses in marine phytoplankton is related to the vertical structure of the environment and to a suite of variables of which temperature is only one. Quantitatively, however, arctic phytoplankton do not appear to adapt to cold by increasing RuBPC levels per unit pigment biomass.

Photoadaptation of sea-ice microalgae in springtime: photosynthesis and carboxylating enzymes

“…The high activity of RuBPC compared to PePC and PePCk clearly shows that C3-carboxylation dominated over p-carboxylations. This corresponds to data of Smith & Platt (1985), who showed for Arctic phytoplankton that RuBPC was the only enzyme tightly linked to photosynthetic capacity. For marine phytoplankton, Appleby et al (1980) and Descolas-Gros & Fontugne (1985) observed that RuBPC dominated over the PePC and PePCk.…”

“…After 3 additional minutes of prelncubation, the samples were inoculated with NaHI4CO3 (100 pl, 5 yCi) and incubated at 20°C for 40 min. This temperature is adequate for enzyme activities according to the results of Li et al (1984) for 3 carboxylatlng enzymes in Arctic phytoplankton, and Descoslas-Gros & De Billy (1987) and Smith & Platt (1985) for RuBPC in respectively cultures of Antarctic diatoms and Arctic phytoplankton. The reaction was stopped by the addition of 0.5 m1 6 N HC1.…”

Temperature regulation of nitrate uptake: A novel hypothesis about nitrate uptake and reduction in cool‐water diatoms

“…7A,B). The observation that NR activity in Skeletonema costatum is maximal around 10-15ЊC (Packard et al 1971;Kristiansen 1983;Dohler 1991) and inactivated above 20ЊC (Gao et al 1993(Gao et al , 1997 and the observation that RUBISCO activity is maximal at Ͼ30ЊC (Li et al 1984;Smith and Platt 1985;Descolas-Gros and de Billy 1987) are not yet available and therefore are not included. The linear regression is significant at the P Ͻ 0.001 level.…”

Ecophysiology of Polar Algae

“…However, Arctic phytoplankton do not appear to acclimate to cold by increasing Rubisco content per unit pigment biomass 0. C. Smith and Platt 1985).…”