Time-course development of 14C specificactivity of chlorophyll a, carbon, and proteins in algal cultures

We evaluated the suitability of N,N-dimethylformamide (DMF) for extraction and measurement of chlorophyll in phytoplankton and compared the extraction efficiencies of DMF, dimethyl sulfoxide (DMSO)–acetone, and 90% acetone. Absorbance spectra and specific absorption coefficients of chlorophylls a, b, and c in DMF and 90% acetone are similar. Acidification of 100% DMF extracts of pure chlorophyll a and healthy algal cultures produced acid ratios approximating 1.7. Thus, equations derived from the extinction coefficients of chlorophylls in 90% acetone can be applied to DMF extracts. DMF and DMSO–acetone each extract chlorophyll from green and blue-green algae more effectively than does 90% acetone. DMF is a better extractant than is DMSO–acetone for chlorococcalean species, especially when pigment concentrations are high, but the difference, although significant, is slight. The three solvents are equally efficient in extracting chlorophyll from samples composed of chrysophytes and flagellated chlorophytes. The lack of grinding when using either DMF or DMSO–acetone is a considerable convenience. The potential for destabilized spectrophotometer readings and contamination of the investigator due to the incomplete mixing of DMSO and acetone is eliminated when pure DMF is used.

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EFFECTS OF PREHARVEST IRRIGATION CUTOFF DURATION ON FRENCH PRUNE TREE PERFORMANCE

HortScience ◽

10.21273/hortsci.25.9.1172a ◽

1990 ◽

Vol 25 (9) ◽

pp. 1172a-1172

Author(s):

G. S. Sibbett ◽

D. Goldhamer ◽

S. Southwick ◽

R.C. Phene ◽

J. Yeager ◽

...

Keyword(s):

Water Deprivation ◽

Time Course ◽

Fruit Size ◽

Soluble Solids ◽

Course Development ◽

Predawn Leaf Water Potential ◽

The Third ◽

Fruit Drop ◽

Tree Fruit ◽

Tree Performance

Variable lengths of water deprivation immediately prior to harvest were imposed on mature French prune trees for four consecutive years. Irrigation cutoff durations were about 45, 37, 30, 22, 17 and 12 days prior to harvest during 1986-89.Predawn leaf water potential best reflected water deprivation length and reached minimum values of about -1.5 MPa with the most severe cutoff. Magnitude of peak stomatal conductance was reduced and occurred earlier in the day with longer cutoff regimes.Rate and time-course development of preharvest fruit drop was variable from year-to-year, but there were no significant differences in total drop between cutoff treatments. Only in the fourth year, following three years of no difference were tree fruit load and yield significantly reduced but then only with the most severe cutoff. Soluble solids were higher and drying ratios lower with the longer cutoffs. Fruit size was significantly reduced in the third year of the experiment. Trunk circumferences were significantly lower only with trees subjected to the longer cutoff regimes.

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Sixty-Three Years Since Kautsky: Chlorophyll a Fluorescence

Functional Plant Biology ◽

10.1071/pp9950131 ◽

1995 ◽

Vol 22 (2) ◽

pp. 131 ◽

Cited By ~ 511

Author(s):

e Govindje

Keyword(s):

Energy Transfer ◽

Excitation Energy ◽

Chlorophyll A ◽

Chlorophyll A Fluorescence ◽

Time Course ◽

Electron Flow ◽

Excitation Energy Transfer ◽

Oxygenic Photosynthesis ◽

Acceptor Side ◽

Starting Point

In 1931, using their eyes as instruments, H . Kautsky and A . Hirsch related the time course of chlorophyll a fluorescence with photosynthesis in a less-than-one-page article in Naturwissenschaften (see Kautsky's photograph). Chlorophyll a fluorescence is now being used by hundreds of investigators as a probe for various aspects of photosynthesis-from excitation energy transfer in picosecond time scale to CO2 fixation in minutes . It is not only a much used, but also a much abused, tool. It is used because of it being a non-invasive, rapid and a highly sensitive probe, and misused because it is sometimes not recognised that it is affected by various photosynthetic and other reactions. I submit that, like any other technique, if it is used with care and with due regard for its time dependence and competing parameters. it will remain as the one-most powerful tool for probing excitation energy transfer, primary photochemistry, electron flow on both the donor and the acceptor side of photosystem II (PSII) of oxygenic PSII. Further, it is very useful in the quick assay of PSII mutations, and down- regulation and other adjustments to stress (excess light, heat, heavy metal, nutrients and certain herbicides). In this paper, I will present my viewpoint, not a review, on the conceptual and experimental developments in this field. Whenever appropriate, and without any shame and humility, I will include some of my involvement in the excitement surrounding this field. I hope that this paper will serve as a starting point for further discussion of not only the history, but the practical use of chlorophyll a fluorescence as an intrinsic probe of stresses to plants, as well as individual reactions of oxygenic photosynthesis, when combined with other parallel measurements.

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Time course of phrenic activity and respiratory pressures during airway occlusion in cats

Journal of Applied Physiology ◽

10.1152/jappl.1981.51.1.99 ◽

1981 ◽

Vol 51 (1) ◽

pp. 99-108 ◽

Cited By ~ 22

Author(s):

N. M. Siafakas ◽

H. K. Chang ◽

M. Bonora ◽

H. Gautier ◽

J. Milic-Emili ◽

...

Keyword(s):

Time Course ◽

Course Development ◽

Airway Occlusion ◽

Time Profiles ◽

Inspiratory Muscles ◽

Inspiratory Activity ◽

Proportional Increase ◽

Relationship Of ◽

The Relationship ◽

Hypoxic Mixtures

The morphology of integrated ("moving time average") phrenic electroneurograms (EPHR) and of tracheal (Ptr) and transdiaphragmatic (Pdi) pressure waves during occluded inspirations was studied in eight anesthetized cats breathing air and various hypercapnic and hypoxic mixtures. The shape of the rising part of EPR-, Ptr-, and Pdi-time profiles varied between animals (from convex to concave), but in each animal it remained virtually unchanged by hypoxia and hypercapnia. The shape of the Ptr and Pdi occlusion waves reflected the shape of EPHR. The relationship of EPHR to Pdi and Ptr did not change with chemical drive. It is concluded that central inspiratory activity (CIA) (as reflected by EPHR and its mechanical transforms Pdi and Ptr) increases in amplitude with stimulation of breathing but that the profile of CIA remains essentially unchanged. However, substantial differences in the time course development of phrenic activity, Pdi, and Ptr exist between cats. The fixed interrelationships among EPHR, Pdi, and Ptr indicate a proportional increase in activity among all inspiratory muscles with increased chemical drive.

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Time-course development of differentiated hepatocarcinoma and lung metastasis in transgenic mice

Journal of Hepatology ◽

10.1016/0168-8278(91)90819-w ◽

1991 ◽

Vol 13 (2) ◽

pp. 227-239 ◽

Cited By ~ 61

Author(s):

Nathalie Dubois ◽

Myriam Bennoun ◽

Isabelle Allemand ◽

Thierry Molina ◽

Gisèle Grimber ◽

...

Keyword(s):

Transgenic Mice ◽

Lung Metastasis ◽

Time Course ◽

Course Development

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Chloroform–Methanol Extraction of Chlorophyll a

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f85-005 ◽

1985 ◽

Vol 42 (1) ◽

pp. 38-43 ◽

Cited By ~ 63

Author(s):

Lindsay W. Wood

Keyword(s):

Hydrogen Sulfide ◽

Chlorophyll A ◽

Room Temperature ◽

Ph Control ◽

Absolute Methanol ◽

Separatory Funnel ◽

Chloroform Layer ◽

Extraction Mixture ◽

Chloroform Methanol ◽

Algal Cultures

Chloroform–methanol (2:1, v/v) extracts significantly more (P < 0.001) chlorophyll a from algal cultures and from freshwater and seawater microcosms than does dimethyl sulfoxide, methanol, absolute methanol with hydrogen sulfide, or 90% acetone. For chlorophyte cultures it yields 97% or more of the chlorophyll a within a 4-h steeping period without grinding. It can be used with both calibrated spectrophotometry and fluorometric instrumentation. Sample filtration onto MgCO3-coated filters is recommended to ensure buffering of the extraction mixture. Holding the filters in chloroform–methanol at 4 °C or room temperature in the dark prevents loss of chlorophyll a for at least 10 d. More refined analyses of phaeophytin and other chlorophylls require the use of chloroform–methanol–water (2:2:1.8, by volume) and placement in a separatory funnel. After 24 h the lower (chloroform) layer contains all of the chlorophyll. Strict pH control is required for pheophytin determinations.

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Synthesis of thylakoid membrane proteins by chloroplasts isolated from spinach. Cytochrome b559 and P700-chlorophyll a-protein.

The Journal of Cell Biology ◽

10.1083/jcb.85.2.435 ◽

1980 ◽

Vol 85 (2) ◽

pp. 435-445 ◽

Cited By ~ 55

Author(s):

R E Zielinski ◽

C A Price

Keyword(s):

Chlorophyll A ◽

Time Course ◽

Deae Cellulose ◽

Thylakoid Membranes ◽

Cytochrome B559 ◽

Radioactive Label ◽

Chloroplast Translation ◽

Thylakoid Membrane Proteins ◽

Triton X ◽

Pigment Protein Complex

Intact chloroplasts, purified from spinach leaves by sedimentation in density gradients of colloidal silica, incorporate labeled amino acids into at least 16 different polypeptides of the thylakoid membranes, using light as the only source of energy. The thylakoid products of chloroplast translation were visualized by subjecting membranes purified from chloroplasts labeled with [35S]methionine to electrophoresis in high-resolution, SDS-containing acrylamide gradient slab gels and autoradiography. The apparent mol wt of the labeled products ranged from less than 10,000 to greater than 70,000. One of the labeled products is the apoprotein of the P700-chlorophyll a-protein (CPI). The CPI apoprotein is assembled into a pigment-protein complex which is electrophoretically indistinguishable from the native CPI complex. Isolated spinach chloroplasts also incorporate [3H]leucine and [35S]methionine into cytochrome b559. The radioactive label remains with the cytochrome through all stages of purification: extraction of the thylakoid membranes with Triton X-100 and urea, adsorption of impurities on DEAE cellulose, two cycles of electrophoresis in Triton-containing polyacrylamide gels and electrophoresis in SDS-containing gradient gels. Cytochrome b559 becomes labeled with both [3H]leucine and [35S]methionine and accounts for somewhat less than 1% of the total isotopic incorporation into thylakoid protein. The lipoprotein appears to be fully assembled during the time-course of our labeling experiments.

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