Biological and Phytochemical Screening of Plants

The Determination of Nucleic Acids

INTRODUCTION 342 IN VIVO ACTIVATION STUDIES 342 STUDIES WITH INTACT CHLOROPLASTS 344 Light-Dependent Enzyme Activation 344 Effects of Inhibitors 346 Light-Induced Change in Stromal pH 348 Light-Induced Change in Stromal M� Concentration 348 STUDIES WITH ENZYME SYSTEMS 350 Mechanisms of Light Activation 350 Effector-mediated mechanisms 350 lon-mediated mechanisms 353 Protein-mediated mechanisms 353 Mechanisms of Deactivation in the Dark 358 DEVELOPMENTAL ASPECTS 359 ACTIVATION OF MEMBRANOUS ENZYMES 360 OXIDANT·LINKED ACTIVATION 361

Role of Light in the Regulation of Chloroplast Enzymes

Scenedesmus sp. was grown in chemostats at a fixed growth rate (p) in an inorganic medium with nitrogen to phosphorus atomic ratios (N:P) ranging from 5 to 80, to investigate the effect of double nutrient limitation. There was no additive or multiplicative effect of the two nutrient limitations: below the optimal cell N:P of30, growth was determined solely by N limitation and above 30, by P limitation. Cell N remained constant up to the optimal ratio and increased linearly with N:P above it. The level of cell P was high at low N:P (N-limited state) but decreased rapidly until N:P approached the optimal and remained constant at a low level at high N:P (P-limited state). Protein was the major fraction in which excess N accumulated under P limitation. Cell free amino acids were a constant proportion of cell N at all N:P ratios. RNA concentration was the same regardless of N:P, it9 level being determined by p independent of the type of limiting nutrients. Cell carbon (C) concentration was higher in the P-limited than in the N-limited state. The C fixation rate per unit chlorophyll a, however, was constant under both P- and N-limited states because the variation in chlorophyll a content was similar to that of C. The apparent maximum uptake rate for nitrate (V) in N- and P-limited cultures decreased with increasing cell N or N:P. In N-limited cultures the half-saturation constant (Km) also decreased at higher cell N or N:P. The variation of V appeared to be affected by the level of free amino acids. Transitions between states of nitrogen contain the two nutrients in an N to P and phosphorus limitation of phytoplank- atomic ratio (N:P) of about 15 (Redfield ton growth are common in both lakes 1958; Ryther and Dunstan 1971), I found and coastal seawaters. Such transitions the optimal cellular N:P of Scenedesmus

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1978.23.1.0010

Effects of N:P atomic ratios and nitrate limitation on algal growth, cell composition, and nitrate uptake 1

(I) Inorganic components . . . . . . . (a) Nitrate . . . . . . . . . (b) Cation-anionuptake . . . . . . (2) Organic compounds . . . . . . . (a) Amino acids and other organic nitrogenous compounds (b) Organic acids . . . . . . . . (3) Effects on flowering . . . . . . . (4) Ammonium plus nitrate as a nitrogen source . . . ( 5 ) Metabolic changes characteristic of ammonium toxicity . VII . Summary . . . . . . . . . . VI . Physiological effects of nitrogen sources . . . .

Ammonium and nitrate nutrition of plants

https://escholarship.org/content/qt6m392350/qt6m392350.pdf?t=p0wtwg

Detection of steroids in paper chromatography

The labeling of intermediate compounds and photosynthetic cofactors during photosynthesis and periods of darkness by Chlorella pyrenoidosa in the presence of 32P-labeled phosphate and 14CO2 have heen investigated. Algae adapted to photosynthesis in air were used, and the level of carbon dioxide was maintained at approximately 0.04 % and at constant specific radioactivity during the course of the experiments.



The transient changes which occur in the levels of labeled fructose-1,6-diphosphate and in sedoheptulose-1,7-diphosphate, and in the corresponding monophosphates when the light is turned off suggest a light activation of the diphosphatase enzymes which decays after about 2 minutes of darkness. It is suggested that a light-dark switch in enzymic activities permits photosynthesis and glycolysis to occur in light and dark respectively with the same enzymic apparatus.



The greatly diminished rate of disappearanec of the carboxylation substrate, ribulose-1,5-diphosphate, after about 2 minutes suggests that there is also a light activation of the carboxylation reaction in vivo. Large transient changes in the level of pyrophosphate between light and dark indicate that there may be an unstable cofactor which decomposes to give pyrophosphate during or alter killing of the algal cells. The possibility that this cofactor is involved in an activation of Carbon dioxide for the carboxylation reaction in vivo is suggested.



Light-dark transient changes in labeling of other compounds of the photosynthetic carbon reduction cycle and related compounds were determined, and possible significance of these changes is discussed.(PDF DAMAGED)

/pdf/light-dark-transients-in-levels-of-intermediate-compounds-3hil0fmqve.pdf

Light‐Dark Transients in Levels of Intermediate Compounds during Photosynthesis in Air‐Adapted Chlorella

https://escholarship.org/content/qt56v6f9pg/qt56v6f9pg.pdf?t=p0hg6q

Photosynthesis by isolated chloroplasts I. Diffusion of labeled photosynthetic intermediates between isolated chloroplasts and suspending medium

https://escholarship.org/content/qt6c96j0rj/qt6c96j0rj.pdf?t=p0fw55

Regulatory effects of ammonia on carbon metabolism in photosynthesizing chlorella pyrenoidosa

https://escholarship.org/content/qt1td7h2ds/qt1td7h2ds.pdf?t=p0hh1t

Martha Kirk

Papers

Detection of steroids in paper chromatography

Light‐Dark Transients in Levels of Intermediate Compounds during Photosynthesis in Air‐Adapted Chlorella

Photosynthesis by isolated chloroplasts I. Diffusion of labeled photosynthetic intermediates between isolated chloroplasts and suspending medium

Regulatory effects of ammonia on carbon metabolism in photosynthesizing chlorella pyrenoidosa

Dynamics of the photosynthesis of carbon compounds. I. Carboxylation reactions.