bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photochemical Characteristics of Mesophyll and Bundle Sheath Chloroplasts from C4 Plants
Authors: RAGHAVENDRA AGEPATI S. , DAS V. S. R. 
Published: April 2006

AbstractMesophyll and bundle sheath chloroplasts were isolated by differential grinding from the leaves of two NADP‐ME C4 plants, Setaria italica Beauv. cv. H‐1, Pennisetum typhoides S & H. cv. AKP‐2, and a NAD‐ME C4 species Amaranthus paniculatus L. The mesophyll chloroplasts of C4 plants possessed slightly lower Km for ADP and Pi than those of bundle sheath chloroplasts.The Hill reaction activities and noncyclic photophosphorylation rates of the bundle sheath chloropiasts from S. italica and P. typhoides were less than one‐fifth of those by the mesophyll chloroplasts. But the bundle sheath chloroplasts of A. paniculatus exhibited high rates of Hill reaction, cyclic as well as noncyclic photophosphorylation. The pigment‐ and eyiochrome composition suggested a relative enrichment of PS 1 in bundle sheath chloroplasts of S. italica and P. typhoides. The chain exists in both mesophyll and bundle sheath chloroplasts. As much as 35–52% of leaf chlorophyll was located in the bundle sheath chloroplasts. The photochemical activities of bundle sheath chloroplasts are significant though a major part of leaf photochemical potential is associated with the mesophyll chloroplasts.
Changes in Ion Transport in Spring Wheat during Ontogenesis
Authors: JENSÉN PAUL 
Published: April 2006

AbstractThe influence of plant age on free space uptake to the root, rate of continuous uptake and translocation of potassium and sulphate was investigated during about 100 days in intact, high‐salt plants of spring wheat (Triticum aestivum L. cv. Svenno). The plants were grown in a green‐house in complete nutrient solution. For the short term uptake experiments, the test solutions were labelled with 36Rb+ and 35S‐sulphate.Free space uptake to the roots increased during the entire growth period. The SO2‐4 free space uptake was divided into a Water Free Space (WFS) fraction and a labile‐bound fraction. The labile‐bound SO2‐4 was considered to be constant during development, and the WFS fraction of SO−24 could then be computed. WFS increased from 2% of total cell volume in 1‐day‐old plants to 30% in 100‐day old plants, apparently due to an increasing proportion of freely permeable root cells. As the WFS fraction of the free space uptake was known, the binding capacity (BC) of K+(86Rb−) of the cell walls and at the cytoplasmic surfaces could be computed. It is suggested that the increasing BC for cations with age was due to an increasing proportion of soluble pectate in the cell walls.Except for the initial 20 days, the continuous ion uptake rate decreased during development. It is suggested that the low uptake rate in young plants is limited by the energy supply to the roots and that the decreased uptake in older plants is due to the increasing proportion of metabolically inactive and collapsed roots. At the end of the cultivation period the ion uptake rate increased at the same time as there was a shift from active to passive ion uptake. This was shown by uptake experiments with 2,4‐dinitrophenol (2,4‐DNP).By changing the air humidity around the shoots and using 2,4 DNP, it was shown that ion and water uptake were closely linked to root activity in young plants but that transpiration pull became gradually more important for water uptake with age.
Influence of Nitrogen and Sucrose in the Medium and of Irradiance of the Stock Plants on Root Formation in Pelargonium Petioles Grown in vitro
Authors: WELANDER TORKEL 
Published: April 2006

Abstract In vitro root formation was studied in petiole explants from Pelargonium×hortorom Bailey cv. Radio exposed to different irradiance (2.5. 11.6 or 23.0 W/m2). Optimal root formation was found when stock plants were subjected to 2.5 W/m2 and explants were grown on a medium with 20 g/I of sucrose and 5.0 mM of nitrogen. The number of roots per explant decreased with increasing nitrogen or sucrose concentrations in the growth medium and with increasing irradiance applied to the stock plants. Variation in temperature (17, 21 or 25°C) did not affect root formation. The number of roots per explant was higher in explants from young petioles than in explants from older petioles.The initial nitrogen content of the explants was highest at the lowest irradiance. The content of reducing sugars and sucrose increased with increasing irradiance. The endogenous levels of lysine, arginine and ornithine were highest at 2.5 W/m2 and the levels of proline. alanine, γ‐aminobutyric acid, glutamic acid, glutaminc, aspartic acid and asparagine were highest at 23.0 W/m2.With rising nitrogen concentration in the medium, the final endogenous content of nitrogen in the explants increased, whereas the content of reducing sugars decreased. When the sucrose concentration in the medium increased, the endogenous content of reducing sugars rose, and the nitrogen level was lowered. Variations in the nitrogen concentration in the growth medium influenced the final level of free amino acids in the explants.
Changes in the Endogenous Cytokinins of Bark and Buds ofSalix babylonica as a Result of Stem Girdling
Authors: VAN STADEN J. , BROWN N. A. C. 
Published: April 2006

AbstractGirdling of 1‐year‐old Salix babyionica L. plants resulted in an early accumulation of compounds which co‐chromatographed with cytokinin glucosides in both the bark and buds below the girdle. In the bark the cytokinin glucosides were present in high levels in both girdled and non‐girdled plants. In the buds of non‐girdled plants. however, glucoside concentration was initially low but then increased rapidly after ringing and reached a maximum level prior to any visible signs of bud swell. With the onset of lateral shoot growth the glucoside cytokinins decreased while the cytokinins that co‐chromatographed with zeatin and its derivatives increased. As the cytokinin glucosides are generally considered to be storage forms, their accumulation in the bark and buds below the girdle apparently does not reflect synthesis but rather transport towards a more competitive sink. In the case of Salix plants the lateral buds would appear to have the ability to hydrolyze these glucosylated zeatin derivatives and then to utilize them for bud development. It is suggested that in the presence of a functional root system lateral buds do not synthesize cytokinins de novo, but that they do have the metabolic capacity to convert cytokinins transported to them.
Critical Water Potential for Stomatal Closure in Sitka Spruce
Authors: BEADLE C. L. , TURNER N. C. , JARVIS P. G. 
Published: April 2006

AbstractSteady state rates of net photosynthesis and stomatal conductance at high water potentials were measured under controlled conditions in a leaf chamber on Sitka spruce [Picea sitchensis (Bong.) Carr.] shoots detached from the forest canopy or on seedlings. The water supply to the seedlings was terminated by excision and the shoot water potential (or critical water potential) and osmotic potential at the onset of stomatal closure measured. The turgor potential was calculated. The initial osmotic potential before insertion of the shoot into the chamber was also measured. Shoot water potential and osmotic potential at stomatal closure, and initial osmotic potential were significantly higher (less negative) in foliage from the lowest level in the canopy compared with foliage in the upper canopy, and higher in shoots of seedlings transferred to low light than in those at high light. Critical water potential also varied with season, being higher in July than in October and November. In all except one instance, turgor potential at the onset of stomatal closure was negative, possibly because of dilution of the cell sap by the extracellular water during the estimate of osmotic potential.Over all the experiments variation in critical water potential was correlated with variation in critical osmotic potential and, to a lesser extent, the initial osmotic potential. However, turgor potential at the critical potential varied from +0.6 to ‐4.6 bar. This suggests that difference in turgor between the guard cells and subsidiary cells, which controls stomatal aperture, is only loosely coupled with the bulk leaf turgor and hence that bulk leaf turgor is not a good index of the turbor relations of the guard cells.
Effects of Ca2+ and Temperature on K+ Content Distribution along Roots of Wheat, Rice and Cucumber
Authors: ZSOLDOS FERENC , KARVALY BÉLA 
Published: April 2006

AbstractThe effects of Ca2+ and temperature on the K+ contents of root segments of wheat (Triticum aestivum L. cv. Aurora), rice (Oryza sativa L. cv. Dunghan Shali) and cucumber (Cucumis sativus L. cv. Csemege Fürtös) were investigated with special regard to the low‐temperature anomaly of the K+ uptake of thermophilic plants. The anomaly occurred in those root segments where the K+ contents turned out to be highest. The K+ contents of the apical root sections of thermophilic species responded in general to Ca2+ in more pronounced ways than those of wheat, at both 0 and 25°C. The concerted actions of a purely physical process with negative temperature coefficient and of the special thermotropic properties of the membranes are suggested to be responsible for the low‐temperature anomaly. A strict discrimination between the Viets‐effect on the content (classical Viets‐effect) and on the uptake is proposed. The classical Viets‐effect seems to be related to alterations in both active transport and exchange processes.
Lowering of Endogenous Lipoxygenase Activity in Pisum sativum Foliage by Cytokinin as Related to Senescence
Authors: GROSSMAN SHLOMO , LESHEM YA'ACOV Y. 
Published: April 2006

AbstractCytokinin (CK), when applied to intact pea plants, considerably lowered endogenous lipoxygenase levels. Furthermore it was demonstrated that the triggering of senescence induced by leaf detachment was invariably accompanied by a significant increase of lipoxygenase activity and the CK application considerably decelerates lipoxygenase increment. It is suggested that the lipoxygenase repression induced by CK is a contributing mechanism to the overall antisenescence action of the hormone, and that this may have biological implications.
Physiology of Rice Tungro Virus Disease: Increased Cytokinin Activity in Tungro‐Infected Rice Cultivars
Authors: SRIDHAR R. , MOHANTY SUSANTA K. , ANJANEYULU A. 
Published: April 2006

AbstractTungro virus infection decreased the chlorophyll content in the susceptible rice (Oryza sativa) cultivar ‘Taichung Native 1’, while it increased the pigment in the less‐susceptible cultivar ‘IR 20’ during the later stages of infection. The virus was recovered from the infected susceptibile cultivar as early as 3 days after inoculation. Relatively low amounts of virus were recovered from the less‐susceptible cultivar between 12 and 30 days after inoculation. The senescence of detached leaves of virus‐infected less‐susceptible cultivar incubated in water in darkness was considerably delayed compared to healthy leaves. The cytokinin activity in the extracts from inoculated less‐susceptible cultivar was 69% higher than in the extracts from the healthy plants.
Response of Eucalyptus occidentalis to Water Stress Induced by NaCl
Authors: ITAI CHANAN 
Published: April 2006

Abstract Eucalyptus occidentalis plants were exposed to NaCl in their culture solution for various time. Determination of cytokinin, abscisic acid, 14C leucine incorporation of E. occidentalis, a xerophyte, does not differ from the response of mesophytes to such treatments.
Rapid, Blue‐Light Induced Transpiration in Avena
Authors: SKAAR H. , JOHNSSON A. 
Published: April 2006

AbstractThe transpiration responses of primary Avena leaves to blue‐light pulses were investigated. Only light with wave length shorter than 524 nm can produce the rapid transpiration response. The action spectrum has a maximum around 450 nm. The rapid transpiration response induced by blue‐light pulses successively disappeared in long‐term experiments if the plant was kept in darkness between the pulses. However, if visible light was given to the plant between the pulses, the rapid response was restored.The magnitude of the rapid transpiration response was investigated under different conditions of background illumination and blue‐light exposure. Saturation of the response was obtained with an irradiation level of 1.5–2 mW.cm−2 (5 min pulses) and with a pulse duration of 4 min (pulse irradiance 2 mW.cm−2). A pulse duration of 3 s was sufficient to produce a significant rapid response at an irradiation level of 2 mW.cm−2.
Different Effects of Tris and Histidine on a Membrane Bound NaK ATPase from Sugar Beet Roots
Authors: LINDBERG SYLVIA , HALLMÉN GUN 
Published: April 2006

AbstractA membrane fraction of sugar beet roots prepared in the presence of dithiothreitol contains (Na++ K++ Mg2+) ATPase activity. This activity was studied in the presence of different concentrations of Tris and histidine. Tris was found to interact with the ATPase in the following way: (1) Tris at 50 mM increases, in the absence of Na and/or K, the activity in an uncompetitive way with respect to MgATP. (2) Concentrations of Tris > 50 mM cause inhibition in the absence of Na and K when the ratio between MgATP and Tris is relatively low. (3) Though Tris at 50 mM stimulates similarly to Na, it can not substitute for Na in the Na + K activation. (4) In the presence of Na and K, Tris acts as a competitive inhibitor. Histidine has little influence on the rate both in the presence and absence of Na and/or K.
Inactivation of Nitrate Reductase of the Yeast, Rhodotorula glutinis
Authors: ITO NOBUAKI , SUZUKI YONEZO 
Published: April 2006

AbstractNitrate reductase (NR) from the yeast, Rhodotorula glutinis var. salinaria was composed of two enzymatic components, diaphorase and terminal nitrate reducing moieties. The enzyme used NADPH as electron donor and FAD as cofactor. The synthesis of nitrate reductase was promoted specifically by nitrate and repressed by ammonium and amino acids. Nitrate reductase from this yeast had an inactive as well as an active form. Inactive enzyme was reactivated by oxidation with ferricyanide in vitro. Hydroxylamine promoted the formation of inactive enzyme in vivo. Ammonium could neither promote the inactivation nor reduce the total level of nitrate reductase activity. Nitrate could protect nitrate reductase from inactivation caused by nitrogen starvation or hydroxylamine.
Photodecomposition of Monogalactosyl Diglyceride Mediated by Chlorophyll
Authors: SELSTAM EVA 
Published: April 2006

AbstractIn acetone extracts the presence of chlorophyll a and b caused enhanced photodecomposition of monogalactosyl diglyceride. Irradiation of isolated etioplasts containing chlorophyllide and monogalactosyl diglyceride caused photodecomposition of chlorophyllide but not of monogalactosyl diglyceride. In irradiated etiochloroplasts containing chlorophyll a and monogalactosyl diglyceride both components were photodecomposed. During photodecomposition of monogalactosyl diglyceride the fatty acid composition remained constant.
Seasonal Changes in Total Free Sugar Content of Field Cocoa Plants
Authors: OWUSU J. K. , ADOMAKO D. , HUTCHEON W. V. 
Published: April 2006

AbstractAs part of a study of factors affecting the vegetative and reproductive characteristics of cocoa, Theobroma cacao L., (viz. leaf flushing, flowering, cherelle wilt, pod setting and pod growth), seasonal changes in total free sugar levels of the bark and wood of field cocoa trees growing under medium shade provided by Gliricidia sepium Steud. trees were studied over a period of 13 months. On dry weight basis, sugar content of the bark (13 to 63 mg/g) was higher than that of the wood (9 to 40 mg/g). Free sugar content was significantly correlated with sunshine hours for the whole period, except October‐November 1975, and March 1976 when pod load, and flowering and leaf flushing respectively, caused considerable reduction in free sugar levels. The peaks of flowering and flushing coincided with those of sunshine hours and free sugar levels. The results, analysed in terms of the prevailing microclimatic conditions, suggest that light is a limiting factor for photsynthesis of shaded cocoa and that the reported stimulation of flowering and leaf flushing, which accompany shade removal, may be attributed to increased sugar status of the trees due to increased photosynthetic activity.
Leucine Uptake and Incorporation by Convolvulus Tissue Culture Cells and Protoplasts under Severe Osmotic Stress
Authors: RUESINK ALBERT W. 
Published: April 2006

AbstractThe uptake and incorporation of radioactive leucine by Convolvulus arvensis L. suspension culture cells were studied under various osmotic conditions to provide information about the effects of osmotic stress at the cellular level and about the suitability of various osmotica for stabilizing protoplasts. When manitol, sorbitol, sucrose, or a mixture of CaCl2 and KCl was added to the cells at a concentration normally used to stabilize protoplasts, the uptake of leucine was inhibited by 50 to 60% and incorporation by 37% with no major differences detected among these osmotica. NaNO3 of a similar osmotic strength exerted considerably more inhibition, an inhibition that was reversed by as little as 10 mM simultaneous CaCl2. None of the osmotica altered leucine or protein leakage from the tissue. In general, external solute concentrations below 0.36 osmolal slightly enhanced uptake and incorporation. At successively higher concentrations, uptake and incorporation decreased in a linear fashion, with no apparent discontinuity in the rate of decrease as the cells plasmolyzed. Cycloheximide inhibited both the uptake and the incorporation of leucine in all osmotic situations tested, exerting a much stronger inhibition upon the uptake by control tissue than upon that by cells in osmotica. Different cellulase enzyme preparations varied considerably in their effects on subsequent leucine uptake and incorporation.
Relation between Nitrogen Nutrition, Cytokinin Activity and Tuberization in Solanum tuberosum
Authors: SATTELMACHER B. , MARSCHNER H. 
Published: April 2006

AbstractIn water‐culture experiments with potato plants (Solanum tuberosum L. cv. Ostara), the influence of tuberization initiated by a 7‐day period of nitrogen withdrawal (discont. N) on the cytokinin activity in shoots, roots and exudate was studied. Plants with a constant supply of nitrogen (cont. N) were used as control. — Whereas no tuberization could be observed with cont. N, discont. N led to tuberization already 2 days after nitrogen withdrawal and all plants had been induced after another 4 days. In the roots of plants with discont. N, there was a temporary increase in cytokinin activity, whereas the activity decreased steadily with cont. N. In the exudate, cytokinin activity was greatly reduced during nitrogen withdrawal, whereas this activity in the exudate increased steadily with cont. N. — In the shoot with cont. N cytokinin activity decreased steadily, but with discont. N, after an initial decrease, the activity increased steeply. This increase is mainly or exclusively caused by a shift between the water‐soluble and butanol‐soluble fractions of the cytokinins in favour of the latter. The shift in cytokinin activity of the shoot is assumed to be in causal connection with an increased photosynthetic activity after the onset of tuber growth as ‘sink’ for assimilates.
Cytokinin Activity in Stolons and Tubers of Solanum tuberosum during the Period of Tuberization
Authors: SATTELMACHER B. , MARSCHNER H. 
Published: April 2006

AbstractIn water‐culture experiments with potato plants (Solanum tuberosum L. cv. Ostara), changes in cytokinin activity in the stolon tips and newly formed tubers during tuberization were studied. Tuberization was induced by withdrawing nitrogen from the nutrient solution. — The cytokinin activity was low in the stolon tips prior to tuberization, but increased considerably in both stolon tips and young tubers during tuberization. At the same time qualitative changes in the cytokinin spectrum occurred. These qualitative changes are reversible if ‘regrowth’ of young tubers is brought about by a sudden high supply of nitrogen. — Despite the close correlation between tuberization and cytokinin activity, it is assumed that cytokinins are not directly responsible for the onset of tuberization, although they play an important role in tuber growth.
The Metabolism of the Herbicide Diphenamid (N‐N‐dimethyl‐2,2‐diphenyl‐acetamide) in Cell Suspensions of Soybean (Glycine max)
Authors: DAVIS D. G. , HODGSON R. H. , DUSBABEK K. E. , HOFFER B. L. 
Published: April 2006

AbstractThe fate of the herbicide diphenamid was determined in cell suspensions of soybean [Glycine max (L.) Merr. ‘Wilkin’] at different stages of cell growth: early log phase (3 to 7 d), log phase (7 to 14 d), and stationary phase (14 to 18 d). [Carbonyl‐14C]‐diphenamid was added to the suspensions as an acetone solution. Neither diphenamid (2 to 3 μM) nor acetone (0.5% v/v) was phytotoxic. The 14C‐labeled products were identified tentatively by thin layer chromatographic comparison with reference compounds. The major metabolic products formed were N‐hydroxymethyl‐N‐methyl‐2,2‐diphenylacetamide, N‐methyl‐2,2‐diphenylacetamide, 2,2‐diphenylacetamide, and two polar metabolites (0.9 to 25% of the applied 14C activity) that appeared to be glucose conjugates; one an acidic glucoside. All metabolites were found in both the cell extract and the culture medium, except for the acidic glucoside, which was recovered in small amounts only from the cell extracts. These products were the same as those recovered from intact plants. Similar results were obtained from cell suspensions of different ages. The rate of metabolism by log phase cells was slightly less than the rate for either young or old cells. The results indicated that soybean cell suspensions can be used to obtain reliable information on the fate of agricultural chemicals in soybeans.
Effect of Water Stress on the Temperature Optima of Net CO2 Exchange for Two Desert Species
Authors: NOBEL PARK S. , LONGSTRETH DAVID J. , HARTSOCK TERRY L. 
Published: April 2006

AbstractThe temperature dependence of net CO2 exchange was determined at various soil water potentials for two sympatric desert species. Notholaena parryi D. C. Eat. (Pteridaceae) and Encelia farinosa Gray (Compositae). As water stress increased, the temperature optimum of apparent (net) photosynthesis shifted 7 to 10°C downward and the maximum rate decreased for both species. The downward shift in temperature optimum with water stress was the result of a greater fractional stomatal closure with increasing temperature and a lowering of the temperature where maximal CO2 residual conductance of the mesophyll cells occurred. This lowering of the temperature for maximal CO2 residual conductance appears to reflect (1) a greater effect of water stress on gross photosynthesis than on respiration plus photorespiration and (2) the higher temperature optimum for respiration plus photorespiration than for gross photosynthesis. The downward shift in the temperature optimum of apparent photosynthesis can have a significant effect on the predicted carbon balance of plants as the soil water potential decreases.