TURNOVER OF PHOSPHATE COMPOUNDS IN CHLORELLA CELLS UNDER PHOSPHATE EFICIENCY IN DARKNESS

1. With the view to get information as to the mode of phosphatetransfer among the intracellular phosphorous compounds undernonphotosynthesizing conditions, investigation was made on thechanges of P-distribution occurring when the algal cells wereincubated in a P-deficient medium in the dark. 2. During the incubation, appreciable decrease of P-contentwas observed only in the fraction of polyphosphate "B". In parallelwith this decrease, an increase of P occurred only in the RNAfraction,indicating that, under non-photosynthesizing conditions, RNAis synthesized with the expenditure of phosphorus of polyphosphate"B". 3. By comparing the present results with those obtained earlierunder photosynthesizing conditions, the effect of light on themode of intracellular mobilization of phosphorous compoundswas discussed. (Received June 8, 1961; )     

PHOSPHATE ACCUMULATION BY COLONIES OF NOSTOC

1. Evidence was obtained which supports the hypothesis that thefirm colonies of Nostoc verrucosum, but not the softer onesof N. commune, can accumulate phosphate from the environmentby non-active means.
2. This accumulation of phosphate was reducedby pre-treating thecolonies with chelating agents, whilst thepresence of CaCl₂in the medium led to an increase.

(Received February 2, 1967; )     

PREVENTION OF PHOSPHATE - INDUCED MITOCHONDRIAL SWELLING

The prevention of phosphate-induced mitochondrial swelling in the whole retina of the rabbit was studied with the electron microscope. It was found that a mixture of ATP, Mg⁺⁺, and bovine serum albumin protected the mitochondria in vitro. This finding confirmed the results obtained spectrophotometrically with isolated rat liver mitochondria by Lehninger.     

KINETICS OF PHOSPHATE TRANSPORT BY SYNECHOCOCCUS LEOPOLIENSIS (CYANOPHYTA): EVIDENCE FOR DIFFUSION LIMITATION OF PHOSPHATE UPTAKE1

The kinetics of phosphate transport by Synechococcus leopoliensis (Racih.) Komarek was investigated. Deviations from Michaelis-Menten kinetics were observed at law concentrations of phosphate and the deviations were consistent with diffusion limitation of transport. Activation energy analysis of the transport process at two concentrations, one at carrier saturation and the other at zero added phosphate yielded activation energies of 11.9 and 5.6 kcal/mole respectively at 25° C. The first is consistent with an enzyme limited process and the second with diffusion limitation through the unstirred layer.     

PHOSPHATE ION AS A PROMOTER CATALYST OF RESPIRATION

The active component of phosphate solutions, in relation to promoter action on oxidising enzymes, is the PO₄ ^'''''' ion. This is shown by the demonstration of a hyperbolic relationship between per cent production of CO₂ (of Elodea) and pPO₄, the measure of the phosphate ion potential. This is consistent with the rate of respiration as affected by changing pPO₄ through change of total phosphate concentration while pH is kept constant. The equation for this relationship is (CO₂ – a) (pPO₄ – b)ⁿ = K where a, b, n, and K are constants and n = 1. The same relationship to phosphate ion concentration, expressed by the equation (Activity of enzyme) (pPO₄)ⁿ = K, where n and K are constants and n varies from 1 to 6 under different conditions, appears to hold for some other enzyme actions, including those of peroxidase and pancreatic lipase.     

光呼吸对光合过程中磷代谢的影响

与光呼吸受抑制的 2％O_2浓度下相比,在 21％O_2浓度下.离体甘薯叶细胞光合作用最适介质无机磷浓度较低.另外,在21％O_2浓度下,降低甘薯叶细胞介质 NaHCO_3浓度,叶细胞光下吸收介质~(32)Pi的量减少;降低完整菠菜叶绿体介质 NaHCO_3浓度,乙醇酸形成相对加强,而介质~(32)Pi掺入到有机磷化合物的量则相对减少.这些结果表明,有利于光呼吸的条件,可降低光合对外界Pi的需求量.     

光呼吸对光合过程中磷代谢的影响

与光呼吸受抑制的 2％O_2浓度下相比,在 21％O_2浓度下.离体甘薯叶细胞光合作用最适介质无机磷浓度较低.另外,在21％O_2浓度下,降低甘薯叶细胞介质 NaHCO_3浓度,叶细胞光下吸收介质~(32)Pi的量减少;降低完整菠菜叶绿体介质 NaHCO_3浓度,乙醇酸形成相对加强,而介质~(32)Pi掺入到有机磷化合物的量则相对减少.这些结果表明,有利于光呼吸的条件,可降低光合对外界Pi的需求量.