ACTION SPECTRA FOR PHOTOSYNTHESIS AND LIGHT‐STIMULATED ION TRANSPORT PROCESSES IN HYDRODICTYON AFRICANUM

mentioning

confidence: 99%

Light-enhanced Chloride Uptake by Wheat Laminae

MacDonald¹,

Macklon²

1975

“…Several inhibitors of electron transport however, did reduce the Cl-fluxes, indicating some involvement with electron flow within the energy apparatus and perhaps a requirement for both systems. Cl-influx was inhibited by the absence of 02 (17,24). Raven (24) has suggested this requirement may indicate the participation of pseudocyclic electron transport with Cl-uptake.…”

mentioning

confidence: 99%

Light and Calcium Interactions in Chlorella Inhibited by Sodium Chloride

Chimiklis¹,

Karlander²

1973

Analysis of NaCl toxicity in Chlorella sorokiniana showed decreased growth rates, increased dry weight per cell, increased intracellular Na+ and Cl-, more total chlorophyll per cell, a decreased chlorophyll a to chlorophyll b ratio, increased rates of 02 evolution, and decreased rates of CO2 fixation when the extracellular concentration of NaCl was increased from zero to 0.3 M. Cultures did not grow at concentrations greater than 0.3 M NaCl unless 10 mM calcium salts were present. Inclusion of that concentration of Ca2+ extended the tolerance to 0.5 M NaCl before growth stopped. Increasing the light intensity from 1.2 to 9.4 mw/cm2 increased growth rates for cultures in 0.10 to 0.45 M NaCl. At 14 mw/cm2 added Ca2+ reduced growth rates of cultures in 0.3 M NaCl compared to controls without added Ca2 . Maximal growth rates for cultures in NaCl media were achieved by addition of 10 mM CaSO4 and maintenance of the light intensity at 9.4 mw/cm2. The maximal growth rate of the organism was 9.6 doublings/day achieved at 2.7 mw/cm2 for control cultures. In 0.3 M NaCl the growth rate was 4.3 doublings/day at 2.7 mw/cm2 and 8.2 doublings/day at 9.4 mw/cm2 with 10 mM CaSO4 added.Increasing light intensities from 2.7 to 9.4 to 14 mw/cm2 decreased Physiological mechanisms of salt tolerance have been primarily concerned with ionic compositions and fluxes. Regulation of ionic composition in marine algae consists of Na+ exclusion with accumulation of K+ and C1-and generally requires cellular energy and the presence of Ca2`(27). Studies of ionic fluxes in the red marine alga Gracilaria foliifera (12), in the fresh water algae Hydrodictyon africanum (23) and Chlorella pyrenoidosa (2), and on the internodal cells of Nitella translucens (18) have demonstrated light-dependent active transport for Na+ exclusion and K+ and Cl-accumulation. Work on the red marine alga Porphyra perforata showed a requirement for Ca2+ in the medium for intracellular retention of K+ (7).Two considerations indicate that light-dependent ion fluxes in green plants are controlled by photosynthetic rather than respiratory energy. First, light generally has little effect on ion fluxes in nongreen tissue, and second, the action spectrum of ion fluxes in green tissue matches that of chlorophyll absorption (23). The activation of K+ and Cl-fluxes in Nitella was separated respectively between photosynthetic systems II and I (18). Under conditions of either DCMU inhibition or far red light irradiation, where system I was functional, K+ absorption was not affected and Cl-absorption was reduced compared to conditions where both photosystems were operative (2, 18, 24). The selective participation of these systems was also reported in Chlorella pyrenoidosa (2) and Hydrodictyon africanum (24). System I was also implicated in Na+ efflux (24).Direct involvement of ATP from cyclic photophosphorylation for light-dependent Na+ and K+ fluxes was established by using uncouplers of phosphorylation. Addition of carbonylcyanide-m-chlorophenylhydrazone (2,17,25,28) and i...

“…Although there is some evidence that phytochrome can act as a photoreceptor regulating potassium movement in leaf cells (19), the light enhancement of ion uptake by green cells is not generally regarded as being associated with a phytochrome system (5,8,18). The inhibition of light-enhanced uptake by DCMU points to photosynthesis or some partial reaction thereof as supplying the energy.…”

Section: Discussionmentioning

confidence: 99%

Energy Supply and Light-enhanced Chloride Uptake in Wheat Laminae

MacDonald¹,

Macklon²,

MacLeod³

1975

The light-supported component of 36CI uptake from 5 mM K'6C1 by green laminae, either chopped or vacuum-infiltrated, of Triticum aestivum L. seedlings has been determined by subtraction of dark uptake values from light uptake values and the energy sources for the uptake elucidated on the basis of the effects of 3-(3,4-dichlorophenyl)-1,1 dimethylurea (DCMU), carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP), antimycin Al (AA), and N2 on light and dark uptake.