摘要:

The 520 nm light-induced absorbance change in wild-type and 4 mutant strains ofChlamydomonas reinhardiwas investigated. In the wild-type strain the absorbance change is composed of at least 2 components, P520 I and P520 II, sensitized by Systems I and II respectively. Some of the properties of these components can be studied by using the appropriate photosynthetic mutant strain. A group of mutant strains modified in the photochemical complex of System II shows only the P520 I absorbance change, whereas a mutant strain deficient in active P700 exhibits only the P520 II absorbance change. The possible relationship between these absorbance changes and the photosynthetic electron transport pathway is discussed.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1969

数据来源: ASPB

摘要:

Malate in beet discs treated in different salt solutions was labeled by a 30 min pulse of14CO2, and subsequent changes in specific activity were followed for several hr. In treatments which resulted in net acid synthesis in response to excess cation absorption, malate specific activity fell slowly after removal of14CO2. In solutions where no net acid synthesis occurred, and from which cation and anion were absorbed equally, malate specific activity fell rapidly when14CO2was removed. The foregoing suggests that the net synthesis of organic acids in response to excess cation absorption leads to the removal of organic anions from cytoplasmic metabolic pools as counter-ions in salt transport to the vacuole.The latter hypothesis was further examined by direct measurement of the distribution of labeled malate between cytoplasm and vacuole using the wash-exchange method of compartmental analysis, previously described for inorganic ions. The method satisfied the criterion of exchange specificity necessary for this purpose. Much higher retention of label in the cytoplasm was observed in KCl solutions (no net synthesis) than in K2SO4solutions (net synthesis) after 3 hr14CO2fixation and subsequent wash-exchange. The observed distribution is consistent with the rapid removal of organic anions to the vacuole during net acid synthesis. The significance of organic acid transport in relation to metabolism is discussed.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1969

数据来源: ASPB

摘要:

The degree of dependence of the growing zone of thePhycomycessporangiophore upon other parts of the stalk was tested by inhibiting glycolysis and oxidative phosphorylation in the stalk below the growing zone. Initially the growing zone is capable of nearly normal growth when the metabolism in the rest of the stalk is inhibited in this way. However, the growing zone appears to become depleted of something normally supplied from below, because after 3 to 4 hr its growth rate slows down and the growth stops much sooner than in normal sporangiophores. The rest of the sporangiophore appears to have a similar degree of local autonomy because isolated sections from below the growing zone can support protoplasmic streaming for 10 to 20 hr.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1969

数据来源: ASPB

摘要:

Pectin esterase (PE) activities in abscission zones, other portions of leaves, and adjacent stem tissues were compared in attached leaves and abscissing petioles (previously debladed) ofColeus blumeiBenth. andPhaseolus vulgarisL.,cv.Canadian Wonder. Earlier findings of Osborne in bean were confirmed and changes in PE activity in coleus were shown to resemble those in bean in some respects. In both plants PE was lower in the distal portion of abscission zones of abscissing petioles than in that portion of attached leaves but this difference was not as large or as consistently clear-cut in coleus as in bean. The general level of PE activity was an order of magnitude lower and changes associated with abscission were smaller in coleus than in bean. Auxin treatment of debladed petioles of coleus prevented abscission and resulted in small increases in PE activity in abscission zones and most of the other regions sampled. The largest increase was observed in the stem tissue adjacent to the attached leaf opposite the debladed, auxin treated one.The activity of coleus PE was highest in the pH range from 7.3 to 7.6. The pH of distal tissue from abscission zones of abscissing petioles was 5.8. This was 0.7 pH units lower than that of proximal tissue from the same zones.PE from both coleus and bean appears to be denatured by freezing and/or thawing.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1969

数据来源: ASPB

摘要:

Isolated fifth internodes ofColeus blumeiBenth. were supplied with3H-IAA at their apical ends. Microradioautography, using thin sections (0.25-0.5 microns) of Epon embedded tissue and liquid emulsion techniques, revealed extremely specific localization of the acetone-insoluble derivatives of IAA. Changes in the patterns of labeling were followed over periods of 3, 24, and 48 hr at various distances from the source of applied auxin. Progressively basipetal labeling of the cell walls of the youngest xylem elements was evident with time. At the end of 24 hr the label was detected also within the cytoplasm or slime of phloem elements. After 24 to 48 hr, labeling of plastids was evident. The results suggest a continued incorporation of IAA derivatives into cell wall precursors.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1969

数据来源: ASPB

摘要:

A technique is presented for a simple, rapid, and reliable means of determining the viability of plant tissue subjected to freezing temperatures. Freezing curves of excised stems ofCornus stoloniferaMichx., and several other genera were studied. Tissue temperature was recorded during freezing of plant stem sections. The heat of crystallization deflected the resultant freezing curves at points where tissue froze. Living stem sections of all genera studied revealed 2 freezing points, while dead tissue exhibited only 1. The influence of variables such as moisture content, sample size, thermocouple placement, and cooling rate on freezing curves was analyzed. Stem samples wrapped in moisture-proof film with a thermocouple inserted into the pith were frozen to a predetermined test temperature, thawed, and subjected to a second freezing cycle. The presence or absence of 2 freezing points in the second freezing cycle was used as a criterion for establishing viability. The results were immediately available and identical to results from regrowth tests which took about 20 days.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1969

数据来源: ASPB

摘要:

Anatomical and ultrastructural details of a translocating 10-cm leaf of sugar beet (Beta vulgarisL. var. Klein Wanzleben) were correlated with translocation rate data. The minor veins were found to be 13 times as extensive as the major veins and measure 70 cm/cm2leaf lamina. Measurements disclosed that a 33-μlength of minor vein services 29 mesophyll cells with the result that translocate moves an average of 73μor 2.2 cell diameters during transport from mesophyll cells to a minor vein. High-resolution, freeze-dry autoradiography revealed that assimilates accumulate in organelle-rich cells of the minor vein phloem. Correlation of phloem volume and loading rate for minor veins yielded an uptake rate of 735μmoles of sucrose per g fresh weight of phloem. The arrangement and structural features of minor veins appeared to be consistent with the concept that vein loading precedes translocati

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1969

数据来源: ASPB

摘要:

Glycolate and glyoxylate stimulated 100% to 300% the rate of oxygen evolution byScenedesmusin the light in the absence of added carbon dioxide. This stimulation occurred either aerobically or anaerobically, and was sensitive to CMU. Aerobic dark respiration was stimulated 25% to 100% by glycolate. This phenomenon was best demonstrated with synchronizedScenedesmusat the stage of cell division. For glycolate stimulation of oxygen evolution, a dark preincubation of 1 minute or less was necessary. In comparative test with other compounds of metabolism and photosynthesis, the stimulation of oxygen evolution was greatest by glycolate and glyoxylate. In a proposed scheme glyoxylate serves as a terminal hydrogen acceptor from NADPH produced by photosynthesis, and it thereby stimulates oxygen evolution when carbon dioxide is not available. Transformation of glycolate to glyoxylate in these cells would have to occur in the absence of oxygen.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1969

数据来源: ASPB

摘要:

Optimum conditions for the extraction and assay by ATP-pyrophosphate exchange of the aminoacyl-sRNA synthetases of the various tissues of french bean (Phaseolus vulgaris) seeds and seedlings are described. Extracts of plumules, after passage through Sephadex G-25, were assayed for synthetase activity using an amino acid mixture as substrate, when a 30 to 100-fold stimulation of exchange above the endogenous level was obtained. This marked enhancement of exchange by added amino acids is largely attributed to the use of dilute extracts.The total synthetase activity of the cotyledons was studied in relation to germination. Synthetase activity was highest in the dry cotyledon; activity decreased in proportion to the loss of protein during germination,i.e.the specific activity of the synthetases remained constant for at least the first 6 days of germination. With a few minor exceptions, the specific activity of the individual synthetases remained constant during germination.The absolute activity of the synthetases of the plumule and radicle increased exponentially during germination. The specific activity of the synthetases in both tissues increased approximately 2-fold during the first 2 to 3 days of germination, then gradually decreased. However the asparaginyl-, valyl-, and histidinyl-sRNA synthetases in the plumule did not conform with this general pattern.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1969

数据来源: ASPB

摘要:

Deficiencies of each macronutrient (N, P, K, Ca. Mg, S, and Fe) decreased the specific activity of nitrate reductase fromTriticum aestivumL. seedlings. Nitrate content was decreased by N, P, K, Ca, and Mg deficiencies and unaffected by S and Fe deficiencies. Glutamic acid dehydrogenase activity was decreased by N, P, and S deficiencies, unchanged by K deficiency, and increased by Ca, Mg, and Fe deficiencies. Glutamine synthetase activity closely paralleled nitrate reductase activity and was decreased by deficiencies of N, P, K, Ca, Mg, and S. Glutamic-oxaloacetic transaminase was not sensitive to macronutrient deficiencies. High14C-leucine incorporation into tissue sections of N-, P-, K-, Ca-, and S-deficient seedlings did not appear indicative of protein synthesis rates in intact seedlings. Nutritional deficiencies apparently depleted endogenous amino acid pools and caused less inhibition of exogenous14C-leucine incorporation into protein.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1969

数据来源: ASPB