bluuebunny/crossref_metadata_2025 huggingface dataset:
Induction of Nitrate Reductase and Peroxidase Activity in the Seedlings of Normal and High Lysine Maize
Authors: SRIVASTAVA H. S. , ASTHANA J. S. , JAIN ABHA
Published: April 2006

Steady state levels of in vivo nitrate reductase activity in the endosperm, scutella, roots and shoots of maize seedlings were higher in normal maize than those in high lysine maize. Activity of peroxidase in the roots, however, was higher in the high lysine cultivar. The nitrate reductase activity increased with the supply of nitrate in all parts of the seedlings of both cultivars, although the rates of increment in the endosperm were lower than those in scutella, roots and shoots. In relation to substrate concentration, a saturation was achieved at 5 to 10 mM of nitrate except in the endosperm, where activity increased slowly up to 100 mM at least. Final levels of enzyme activity were significantly higher in the scutella of normal than in that of high lysine seedlings. In vitro enzyme activity in the roots also increased with the supply of nitrate in both cultivars, reaching maximum at 5 to 10 mM nitrate.
Nitrate Assimilation in Rice Grown under Lowland Conditions
Authors: RAO E. V. S. PRAKASA , PRASAD RAJENDRA , ABROL Y. P.
Published: April 2006

Pattern and extent to which the main shoot of rice (Oryza sativa L.) cv. Pusa 33 assimilates NO3‐ when grown under lowland conditions was determined in a field study. The in vivo NR (nitrate reductase) activity is low as compared to the value in other cereals grown under aerobic soil conditions. The leaf blades had higher NR activity (g fr. wt.)‐1 than the sheaths and stem. Calculation of total NO3‐ (mol) reduced in the main shoot, obtained by integrating the in vivo NR assay values per plant part and per day over the duration for which the various plant parts on the main shoot remained metabolically active, showed that out of the total reduced N at harvest, 16.6% was assimilated via the enzyme nitrate reductase. In the leaf sheaths and stem the NO3‐ was reduced to slightly over 50% of the total NO3‐ that was reduced in the main shoot. The rest of the amount was reduced in the leaf blades.
Efflux of Potassium from Wheat Roots Induced by Changes in the Water Potential of the Root Medium
Authors: ERLANDSSON GUNVOR
Published: April 2006

Effects of rapid or stepwise decrease of the water potential by polyethylene glycol in the root medium on the efflux and uptake of 86Rb‐potassium, and the effect of abscisic acid on the efflux of 86Rb‐potassium were investigated in roots of intact wheat plants (Triticum aestivum L. cv. Weibulls Original Starke II). The efflux of ions increased at both a rapid and a stepwise reduction in water potential, but the effect was less at a stepwise reduction in water potential. Active uptake of ions decreased as much at a stepwise as at a rapid reduction in water potential. Addition of 4 × 10–5 M abscisic acid to the root medium did not affect the efflux of ions. It is suggested that low water potentials affect both membrane permeability and active uptake of ions. The increase of efflux is not induced by increase of ABA only.
Chlorophyll Composition in an Isolated Chlorophyll a‐Protein Complex of Photosystem I
Authors: ANDERSSON LARS , EGNÉUS HANS
Published: April 2006

A P700‐chlorophyll a‐protein complex, solubilized by the detergent Triton X‐100, has been isolated by hydroxyl apatite column chromatography. The chlorophyll composition was determined by thin‐layer chromatography and spectrofluorimetric analysis. This photosystem I reaction centre complex, prepared at pH 7, contained pheophytin a and P700 in a ratio of 2/1, high enough to account for a composition similar to that in the reaction centre of photosynthetic bacteria. Prepared at pH 9, the same ratio was 0.2/1, which excludes pheophytin a from having the same function as that of bacterio‐pheophytin in the photosynthetic bacteria.
The Presence of a Ribonuclease of High Molecular Weight in Sugar Beet Storage Tissue
Authors: GUERRIERO VINCENT , DUNHAM VALGENE L.
Published: April 2006

Soluble ribonuckasie activity in sliced root tissue or sugar beet (Beta vulgaris) decreased to 30% of initial levels during the first 15 hours of aeration in sterile phosphate buffer. Activity increased with continued aeration reaching a maximum at 30 hours (85% of initial levels). Ribonuclease activity was isolated from unaerated tissue and partially purified by precipitation with acid and ammonium sulfate and by Sephadex chromatography. Enzyme activity was linear with respect to enzyme and substrate concentrations. The enzyme exhibited a substrate preference for RNA with no activity in the presence of native or denatured DNA. Elution of the enzyme from a Sephadex G‐150 column indicated a molecular weight of 155,000. This uniquely large ribonuclease had no phosphodiesterase activity, was unaffected by ethylenediamine tetraacetate, and was inhibited by increasing Nig2+ concentrations.
Determination of Indoleacetic Acid from Plant Samples by an Alkali Flame lonization Detector
Authors: SWARTZ H. J. , POWELL L. E.
Published: April 2006

Gas chromatography in which an alkali flame ionization detector is utilized has been shown to be a highly sensitive and selective method for determination of indoleacetic acid and certain other indoles. Methodology for detecting indoleacetic acid in plant samples (Fragaria × ananassa Duch. and Malus pumila Mill.) is described.
Mesure journaliére sur cycle végétatif complet des échanges gazeux: photosynthése, transpiration et respiration nocturne ?une culture de Maïs conduite sur colonnes de sol
Authors: MOUTONNET P. , COUCHAT PH.
Published: April 2006

Daily measurement of gas exchanges during a complete growth cycle: photosynthesis, transpiration and night respiration in a soil culture of maize.

During a complete growth cycle, photosynthesis (P), night‐respiration (R) and transpiration (T) have been measured daily for maize (Zea mays L. cv. INRA F7 × F2) in a self‐regulating growth chamber. P and T varied according to three different kinetics. During the growing period there was a fast and concomitant variation of both P and T, which could be filled to a power function of time. During the fructification period we observed a linear decrease of P and T. Finally, during the senescence period P decreased to zero, whereas T kept a value higher than the evaporation of the naked soil. In the first two periods, the P/T ratio decreased as leaves aged. From this we could deduce that a slow increase of stomatal resistance (RS) and mesophyll resistance (RM) took place. R increased until the panicle appeared; it remained constant during fructification and then it decreased with senescence. Each nitrogen supply induced a transient increase of R. Finally, a water stress led to a greater decrease of P than of R, but the after effect of water stress disappeared a day later. These results were compared with those obtained in hydroponic conditions.
Petiole Pithiness in Celery Leaves: Induction by Environmental Stresses and the Involvement of Abscisic Acid
Authors: ALONI B. , PRESSMAN E.
Published: April 2006

Petiole pithiness in celery, Apium graveolens L., was found to be stimulated by several types of root stress. Flooding of the root zone as well as nutrition deficiency required a prolonged period (25–30 days), but water deprivation had a rapid (2–3 days) effect on pithiness development.

Pithiness development induced by water deprivation is not reversible upon rehydration of whole plants but is reversible upon rehydration of affected petiole slices. The stimulation of water stress‐related pithiness was found to be associated with an increased level of endogenous free abscisic acid (ABA). Exogenously applied ABA stimulated petiole pithiness of detached leaves in a concentration‐dependent fashion.

It is suggested that in celery, ABA is an agent which mediates stimulation of petiole pithiness by water stress.
Residual effects of High Temperature Pre‐Treatments on the Germination of Celery Seeds (Apium graveolens)
Authors: BIDDINGTON N. L. , THOMAS T. H.
Published: April 2006

Celery seeds (Apium graveolens L.) were allowed to imbibe in the dark for different periods at 28. 32. 37 or 41°(the high temperature pre‐treatmem or HTP) prior to transfer to 15, 17, 19.5 or 22°C in white light (the low temperature treatment or LTT). The effect of HTP's at 28. 32 and 37°C was to lower the upper temperature limit for germination and this effect increased with increase in the temperature and duration of the HTP. Increasing exposure to an HTP of 41 °C, however, did not appear to lower the upper temperature limit for germination but reduced the viability of the seeds. This trend of increased inhibition of germination caused by increasingly higher temperatures was reversed when the transfer was to a 22°C LTT after a 4 day HTP at 37°C.

When the temperature of (he HTP was relatively low and transfer was to a low LTT. or if the HTP was of a brief duration, the rate of germination was increased as compared to seeds not given an HTP. However, when the temperature and duration of the HTP were increased, the rate of germination became slower than that of seeds not given an HTP, i.e. the time taken for the seeds to recover from the HTP‐induced dormancy increased with the temperature and duration of the HTP. The decrease in the germination rate was caused by a delay in the start and not a slowing of the rate of embryo elongation within the seed.
Effects of Sulphur Dioxide on Sugar and Free Amino Acid Content of Pine Seedlings
Authors: MALHOTRA S. S. , SARKAR S. K.
Published: April 2006

Treatment of jack pine (Pinus banksiana Lamb.) seedlings with gaseous SO2 resulted in a shift between the reducing and non‐reducing sugars. Increasing concentrations of gaseous SO2 caused an increase in reducing sugars and a decline in the non‐reducing sugars, suggesting a conversion from the latter to the former at high SO2 concentrations. The total amino acid content of the intact tissues also increased with increasing concentrations of gaseous SO2. Gas‐liquid chromatographic analyses of the amino acids indicated that SO2 (1. 34 mg · m‐3 for 96 h) resulted in an increase in the content of alanine, valine, glycine, isoleucine, leucine, threonine, aspartic acid tyrosine, lysine, and arginine, and a decrease in the content of serine and glutamic acid. The enzymatic and other implications of such changes are discussed.
Protein Synthesis in Dormant and Non‐Dormant Cocklebur Seed Segments
Authors: SATOH SHIGERU , ESASHI YOHJI
Published: April 2006

Using the axial and cotyledonary segments of lower cocklebur (Xanthium pensylvanicum Wallr.) seeds, protein synthesis as shown by incorporation of radioactive leucine was examined in relation to their dormant status. During the first 9 h of water imbibition, the protein synthesis was higher in the dormant axes than in the non‐dormant, after‐ ripened ones. When imbibed for more than 12 h non‐dormant axes had a higher activity than dormant ones. This was also the case with the cotyledonary segments.

Cyctoheximide, an inhibitor of protein synthesis, blocked protein synthesis in the axial tissue regardless of its dormant status, and thereby inhibited germination of the non‐dormant seeds. In the dormant seeds, however, cycloheximide at 3 mM slightly stimulated germination without stimulating the C2H4 production. Based on these results, it is suggested that in cocklebur seeds there may be some proteinaceous system which is involved in the maintenance of dormancy.
The Effect of Calcium on the Uptake and Distribution of Sodium in Excised Barley Roots
Authors: NEIRINCKX L. , STASSART J. M.
Published: April 2006

The total uptake and relative distribution of Na+ along the root was investigated in excised barley roots (Hordeum vulgare L. cv. Union) of 6‐day‐old plants cultured on 0.25 mM CaSO4. One technique involved cutting the roots at harvest time after different uptake periods into different segments each 2 cm long. These segments were ashed and sodium was measured by flame photometry. For each experiment two treatments were done, one containing calcium in the uptake solution and one without calcium. A second technique involved the measurement of sodium transport, using labelled 22Na+ solution. Although no significant differences could be found between the calcium containing and the calciumless treatments at 24 h, there were clearcut differences for the first 6 to 8 h. The effect of calcium on the first stages of the sodium uptake was a large accumulation of sodium in the part close to the apex with a translocation close to nil; whereas the sodium taken up in the absence of calcium did not accumulate in such large amounts in the apex region but was immediately transported basipetally.
The Influence of Light and Oxygen on Nitrogenase Activity in the Lichen Stereocaulon paschale
Authors: HUSS‐DANELL KERSTIN
Published: April 2006

Thalli of the lichen Slereocaulon paschale (L.) Fr. were prctreated in the light (light activated) or in the dark (dark starved). In short‐time experiments with both light activated arid dark starved thalli, the nitrogenasc activity was higher in the light than in the dark, Light activated thalli had a very much higher rale of C2H2 reduction than dark starved thalli, both in the light and in the dark. The dark starved lhalli showed increasing nilrogenase activity when incubated in the light.

Either light or oxygen was necessary for nitrogenase activity in light activated thalli. and up to about 10kPa oxygen they showed additive effects. Both in the light and in the dark the nitrogenase activity decreased when the oxygen partial pressure was lower than in normal air. The experimental data thus showed a short‐term effect of light on nilrogenase activity by provision of ATP and reductant, and a long term effect probably by build up of reserves that were later utilized. Any immediate effect of photorespiration on nitrogenase activity could not be found in light activated thalli.
Origin of Cytokinins Transported in the Phloem
Authors: VONK C. R.
Published: April 2006

The origin of cytokinins in the exudate of Yucca inflorescences has been studied. A decrease in nucleotides of both isopenlenyladenine and zeatin was observed after removal of leaves as measured over a three day period. Removal of roots and the greater part of the rhizome resulted in a transient decline of isopenlenyladenincand zeatin nucleotides during 24 h. after which an increase took place. The results strongly indicate that the latter increase is due to cytokinins originating from the leaves.
Apparent Three‐Site Kinetics of Cs+‐Uptake by Yeast
Authors: DERKS W. J. G. , BORST‐PAUWELS G. W. F. H.
Published: April 2006

The concentration dependence of the uptake rate of Cs+ in yeast at low pH is described by a cubic rate equation rather than by a quadratic rale equation. This points to the involvement of three sties in the translocation of Cs+ across the yeast cell membrane. The possibility that one of the three sites is only apparent due to interaction of Cs+ with the electrical double layer of the yeast cell membrane is also considered.
Metabolism of Auxin in Pine Tissues: Naphthaleneacetic Acid Conjugation
Authors: RIOV JOSEPH , COOPER RAYMOND , GOTTLIEB HUGO E.
Published: April 2006

Incubation of sections of various tissues of Pinus pinea L. and Pinus halepensis Mill, with α‐naphthaleneacetie acid‐1‐14C (NAA) resulted in two metabolites which proved to be l‐O‐(α‐naphthylacetyl)‐β‐D‐glucose (NAGlu) and α‐naphthylacetylaspartic acid (NAAsp). NAGlu was purified by means of insoluble polyvinyl‐polypyrrolidone (Polyclar AT) column chromatography and preparative thin layer chromatography and identified by its ‘H‐nuclear magnetic resonance and mass spectra. NAAsp was partially purified by means of preparative thin‐layer chromatography and identified by co‐chromatography with a synthetic standard and hydrolysis to the parent compounds. NAA and L‐aspartic acid. Needles and shoot bark rapidly converted NAA mainly to NAGlu. In contrast, woody roots and shoot wood showed a much slower rate of conjugation with the formation of both NAGlu and NAAsp. Preincubation of wood sections in NAA increased the formation of NAGlu, whereas the formation of NAAsp was almost unaffected.
Resistance to Water Transfer in Desert Shrubs Native to Death Valley, California
Authors: SANCHEZ‐DIAZ MANUEL F. , MOONEY HAROLD A.
Published: April 2006

Differences in plant resistance to water flow, patterns of water transport through stems, and stomatal behavior were studied on three species native to the exceptionally hot and dry habitat of Death Valley, California (—, and Larrea divaricata).

Dawn xylem water potentials in July for Atriplex were — 27.5 bar under natural conditions. Corresponding values for Tidestromia and Larrea were respectively — 8.0 bar and ‐32.0 bar (natural) and — 7.5 bar and — 18.0 bar (irrigated). Recovery of xylem water potential in covered field plants of an irrigated transplant garden reached a maximum value in July of — 9.5 bar in Atriplex, — 5.7 bar in Tidestromia and — 7.0 bar in Larrea.

Resistance to free‐energy transfer was used to study resistance to water transport through the plants. Under field conditions irrigated Atriplex plants gave a whole plant resistance of 20.70 × 106 s cm‐1, as compared lo 18.37 × 106 s cm‐1 for Larrea and 10.01 × 106 s cm‐1 for Tidestromia. Plant resistance to water How computed by this method on Atriplex plants grown under laboratory conditions gave a value of 3.73 × 106 s cm‐1 at 35C.

Paths of water flow in field plants as investigated with injected acid fuchsin indicated a sectorial straight type vessel.

The relationship between transpiration rates and xylem water potentials in Atriplex hymenelytra was linear between transpiration 1.28 μg cm‐2 s‐1 and 2.35 μg cm‐2 s‐1 at 35°C. These results indicate that according to the Van den Honert model for water transport, plant resistance to water flow remained rather constant at this temperature. In Atriplex grown under laboratory conditions there was an adjustment of plant resistance so change in water flux at 9.5°C and 25°C.

When laboratory‐grown plants of Atriplex and Tidestromia were subjected to water stress by withholding water. Tidestromia closed stomata and reduced transpiration rates at higher water potentials than in Atriplex.

The ratio of vapor pressure gradients of leaf/air to leaf diffusion resistance was proportional lo transpiration rates.

It is suggested that Atriplex hymenelytra is a species that combines strong regulation of water loss by stomata with low efficiency of the water transport system. These plants are unable to prevent depression of plant water potential as transpiration increases. On the other hand. Tidestromia oblongifolia has little stomatal regulation of transpiration and a highly efficient water transport system. These plants sustain very high rates of transpiration without significant decrease in plant water potential.
Influence of Nitrogen Form and Nitrogen Absence on Utilization of Assimilates for Growth and Maintenance in Tops and Roots of Lolium multiflorum
Authors: HANSEN G. K.
Published: April 2006

Utilization of assimilates for growth and maintenance of tops and roots of Lolium multiflorum was determined for plants supplied with either nitrate or ammonium. Carbon dioxide exchange rates were measured continuously for tops and roots separately. Three‐day periods were applied for two irradiation levels. On the last day of each three‐day period no nitrogen was supplied to the two treatments. In the nitrate treatment, the coefficient of utilization for converting assimilates into constructive growth (YG) remained unaffected in absence of nitrate. However, in absence of nitrate the maintenance respiration (M) for both tops and roots was only one third of that in presence of nitrate. In the treatment with ammonium the maintenance respiration of the plants was not influenced by the absence of ammonium. However, especially for the tops YG increased in absence of ammonium. In both the treatments, growth respiration of the roots was inefficient compared to that of the tops. Only in the case of absence of nitrate, maintenance respiration of the roots was similar to that of the tops.
Photosynthate Partitioning and Enzymes of Sucrose Metabolism in Sugarbeet Roots
Authors: SILVIUS JOHN E. , SNYDER FREEMAN W.
Published: April 2006

Populations of sugarbeet (Beta vulgaris L.) plants that differed in taproot/leaf weight ratio and in photosynthate partitioning between taproots and fibrous roots did not differ in root/shoot ratio as indicated by relative dry weight distribution. Based on the hypothesis that dry weight distribution is influenced by the metabolism of imported sucrose, we examined the relationships between the activity of the enzymes of sucrose metabolism and dry weight distribution as a function of genotype and ontogeny.

A decreased specific activity of acid invertase in taproots was associated with increased taproot/fibrous root weight ratio at 21 and at 28 days post‐emergence. Alkaline invertase activity was negatively correlated with taproot/fibrous root weight ratio at 28 days. Sucrose synthetase specific activities of taproots were not correlated with dry matter distribution. Acid invertase may influence photosynthate partitioning between the taproot and fibrous roots via regulation of sucrose levels in the region of fibrous root initiation.
Inertness of horseradish peroxidase to 2,4‐dichlorophenoxyacetic acid
Authors: PAUL K. G. , ÖHRMAN B.
Published: April 2006

The possibility of mutual effects of 2,4‐D and horseradish (Armoracia lapathifolia L.) peroxidase on each other has been explored by four procedures. (i) Compounds I, II, and III of horseradish peroxidase (HRP) and H2O2 were exposed to 2,4‐D. (ii) Extracts from batchwise operations of HRP + H2O2 and 2,4‐D were analyzed for oxidation products by means of thin layer chromatography. (iii) The velocity of the IAA oxidase reaction with HRP as catalyst, and (iv) Km and Vs of the overall peroxidation of guaiacol by HRP + H2O2, were determined in the absence and presence of 2,4‐D.

The results failed to show any effect of 2,4‐D; only at very high concentrations did 2,4‐D slightly inhibit the oxidation of IAA by one isoperoxidase. It is concluded that 2,4‐D does not promote growth in plants by hampering a peroxidase‐catalyzed IAA oxidation. It seems probable that 2,4‐D perturbs the isoperoxidase pattern by acting at some step prior to the release of the enzyme from its site of synthesis.
Aspects of DNA, RNA and protein synthesis during somatic embryogenesis in a carrot cell suspension culture
Authors: FUJIMURA TATSUHITO , KOMAMINE ATSUSHI , MATSUMOTO HIDEAKI
Published: April 2006

Changes in DNA, RNA and protein content, incorporation of 3H‐thymidine, 14C‐uridine and 3H‐leucine and template activity of chromatin were investigated in the early process of somatic embryogenesis in a carrot (Daucus carota L. cv. Kurodagosun) cell suspension culture using a synchronous system. An embryogenetic culture in a medium containing 10‐7M zeatin was compared with a non‐embryogenetic culture in a medium containing 10‐7M zeatin and 5 x 10‐7M 2,4‐D. DNA was synthesized very actively prior to and during the formation of globular embryos in the embryogenetic culture. The RNA and protein content per tube increased at an almost constant rate in both cultures, while the rate of incorporation of labelled precursors of RNA and protein rose much more prior to active DNA synthesis in the embryogenetic culture than in the non‐embryogenetic culture. Template activity of chromatin was high in the early stage of embryogenesis in the embryogenetic culture. The results obtained here showed that synthesis and turnover of RNA and protein became active prior to active DNA synthesis in the early stage of embryogenesis, and that these changes at macromolecular levels may play important roles in embryogenesis.
Additive and nonadditive effects of serial applications of gibberellic acid on sugarcane internode growth
Authors: MOORE PAUL H.
Published: April 2006

Sugarcane (Saccharum spp. hybrids) plants were exogenously supplied with, 0, 1.0, 1.5, and 2.0 mg gibberellic acid (GA3) per stalk in single and multiple applications. Increases in stalk fresh weight, total stalk length, and lengths of individual internodes were primarily a function of the interval between applications. Applications produced additive growth responses at 15‐ and 30‐day intervals but not at 0‐ and 45‐day intervals.
Control of K+ (Rb+) influx and transport with changed internal K+ concentration and age in two varieties of barley
Authors: JENSÉN PAUL
Published: April 2006

The influx of Rb+ into the roots of two barley varieties (Hordeum vulgare L. cv. Salve and cv. Ingrid) from a K+‐free 86Rb‐labelled nutrient solution with 2.0 mM Rb+, was checked at intervals from day 6 to day 18. The control plants were continuously grown in complete nutrient solution containing 5.0 mM K+, while two other groups of plants were grown in K+‐free nutrient solution starting on day 6 and between day 6 and day 9, respectively. The pattern of Rb+ influx was similar for both varieties, although their efficiencies in absorbing Rb+ were different. The relationship between Rb+ influx and K+ concentration of the root could be interpreted in terms of negative feedback through allosteric control of uptake across the plasmalemma of the root cells. Hill plots were bimodal, but in the opposite direction. The Hill coefficients, reflecting the minimum number of interacting allosteric binding sites for K+ (Rb+), were low (≤–3.0). It is discussed whether the threshold value, that is the breaking point in the Hill plot, is indicative of a changed efficiency of transporting units for K+ (Rb+) transport to the xylem. Moreover, feedback regulation might be involved in transport of K+ between root and shoot. The variation in K+ concentrations in the roots and shoots of control plants were cyclic but in phase opposition despite an exponential growth. The average K+ concentration varied only slightly with age.
Enhancement of pollen embryo formation in Datura innoxia by charcoal
Authors: TYAGI AKHILESH K. , RASHID A. , MAHESHWARI S.C.
Published: April 2006

In recent years liquid medium has been shown to be better than agar‐gelled medium for production of haploids by anther culture. However, on addition of charcoal to agar medium the anther response in Datura innoxia Mill, increases dramatically and is better than in liquid medium. For anthers with pollen at the premitotic stage, the best result was observed with 1% charcoal in Difco agar and 1.5% in Normal agar. The effect is possibly due to adsorption of substances inhibitory to androgenesis and emanating from anthers, as well as to substances present in the nutrient medium and agar.
Effects of repeated application of water stress on water status and growth of wheat
Authors: SIONIT NASSER , TEARE IWAN D. , KRAMER PAUL J.
Published: April 2006

The effects on water status and growth of controlled cycles of water stress applied at various stages of development were studied on a semi‐dwarf spring wheat (Triticum aestivum L.). The plants were grown in controlled environment chambers of the Duke University Phytetron at 24/18°C with a 12‐h photo‐period at about 600 μE m−2 s−1. Groups of plants were subjected to severe water stress by withholding irrigation, beginning at the 7th leaf, early anthesis, or early dough stages of development. A second cycle started 9 to 13 days after termination of the first cycle and maintained until the flag leaf water potential reached –25 bars at each of the growth stages.

The lower leaves showed sign of wilting as indicated by curling in the first drying cycle at –7 bars and in the second cycle at –9 bars of leaf water potential during all stages of growth. Although these leaves recovered completely upon rewatering, onset of senescence was accelerated by three days in stressed plants. A preliminary drying cycle did not increase the ability of the plants to withstand subsequent stress because of severity of stress. Water stress of –25 bars at all three stages of growth reduced seed yield. The reduction was greater when a second stress cycle was also applied. Stress applied during early anthesis stage produced the smallest and the least number of seeds. The lack of osmotic adjustment probably was due to very rapid and severe development of water stress.
CO2 effects on apical dominance in Pisum sativum
Authors: PAEZ A. , HELLMERS H. , STRAIN B. R.
Published: April 2006

Alaska pea plants (Pisum sativum L.) were grown at 0.10 vol% and 0.035 vol% CO2 to determine the effects of high CO2 concentration upon plant growth and apical dominance. The results showed that a 0.10 vol% CO2 atmosphere significantly increased the rate of lateral branch, flower bud, flower and fruit development over an environment with 0.035 vol% CO2. At plant maturity, however, there were no significant differences in the number of branches or fruits produced at the different CO2 levels. Thus, no evidence was obtained for the loss of apical dominance at the CO2 concentrations tested. Root dry weight was significantly greater in plants grown at 0.10 vol% CO2 than in those grown at 0.035 vol% CO2 and leaf dry weight was significantly lower. However, no significant differences were found in total plant dry weight production at plant maturity.
Perception et réaction géotropiques de l'épicotyle d'Asparagus officinalis
Authors: PERBAL GÉRALD , RIVIERE SIMONNE
Published: April 2006

Geoperception and georeaction in Asparagus officinalis epicotyls

The location and the role of the statenchyma were investigated in Asparagus officinalis epicotyls 1, 2 or 3 cm in length. The statocytes represent a monocellular sheath which comprises the outer layer of the pericycle. Three phases of differentiation (S1, S2, S3) of the statocytes may be distinguished by criteria of cell length, the state of vacuolisation and the sedimentation of amyloplasts and nuclei with respect to gravity. The statenchyma was found to be located only in the first 10 mm of the epicotyl 1, 2 or 3 cm in length; in effect the oldest statocytes (S3) differentiate into sclerenchyma beneath this level.

The geotropic curvature of the epicotyls begins with a positive (downward) curvature and the negative (upward) response is only realized after 15–30 min of geotropic stimulation. The upper limit of the bending is located in the zone containing the mature statocytes (S3), while the lower limit is located much closer to the base of the epicotyl.

Experiments on decapitation of the epicotyls have indicated that the S1 and S2 statocytes do not play an important role in the perception of gravity. However, with S3 statocytes, it has been demonstrated that there is a statistical correlation between the initial rate of curvature of the epicotyls and the length of their sheaths. Thus, the longer the sheath, the more the epicotyls curve.

From the results obtained it is proposed that the statocytes are responsible for the geotropic perception of Asparagus officinalis epicotyls.
Far‐red induced changes of the protochlorophyllide components in wheat leaves
Authors: KLOCKARE BIRGITTA
Published: April 2006

Biosynthesis of chlorophyll is partly controlled by the phytochrome system. In order to study the effects of an activated phytochrome system on the protochlorophyllide (PChlide) biosynthesis without accompanying phototransformation to chlorophyll, wheat seedlings (Triticum aestivum L. cv. Starke II Weibull) were irradiated with long wavelength far‐red light of low intensity. Absorption spectra were measured in vivo after different times in the far‐red light or in darkness. The relationship between the different PChlide forms, the absorbance ratio 650nm636 nm changed with age in darkness, and the change was more pronounced when the leaves were grown in far‐red light. Absorption spectra of dark‐grown leaves always showed a maximum in the red region at 650 nm. For leaves grown in far‐red light the absorption at 636 nm was high, with a maximum at the 5 day stage where it exceeded the absorption at 650 nm. At the same time there was a maximum in the total amount of PChlide accumulated in the leaves, about 30% more than in leaves grown in darkness. But the amount of the directly phototransformable PChlide, mainly PChlide650–657, was not increased. The amount of PChlide628–632, or more probably the amount of (PChlide628–632, + PChlide 636–657) was thus higher in young wheat leaves grown in far‐red light than in those grown in darkness. After the 5 day stage the absorption at 636 nm relative to 650 nm decreased with age, and at the 8 day stage the spectra were almost the same in both types of leaves. Low temperature fluorescence spectra of the leaves also showed a change in the ratio between the different PChlide forms. The height of the fluorescence peak at 632 nm relative to the peak at 657 nm was higher in leaves grown in far‐red light than in dark‐grown leaves. – After exposure of the leaves to a light flash, the half time for the Shibata shift was measured. It increased with age both for leaves grown in darkness and in far‐red light; but in older leaves grown in far‐red light (7–8 days) the half time was slightly longer than in dark‐grown leaves. – The chlorophyll accumulation in white light as well as the leaf unrolling were faster for leaves pre‐irradiated with far‐red light. The total length of the seedlings was equal or somewhat shorter in far‐red light, but the length of the coleoptile was markedly reduced from 8.1 ± 0.1 cm for dark‐grown seedlings to 5.2 ± 0.1 cm for seedlings grown in far‐red light.
Water stress and root formation in pea cuttings
Authors: RASMUSSEN SIGGA , ANDERSEN A. SKYTT
Published: April 2006

Cuttings from eleven day old pea plants (Pisum sativum L. cv. Alaska) grown under either 16 or 38 W m−2 PAR were treated for 24 h with solutions of abscisic acid (ABA). After rooting for 13 days in 16 W m−2 irradiance under mist it was found that 10−5 to 10−4M ABA stimulated rooting (root numbers) while higher concentrations apparently were inhibitory. However, the extension of the rooting period to 17 days indicated that this inhibition was due only to a delay of root emergence. Cuttings from low irradiance took up much less solution than those from high irradiance, giving the appearance of higher sensitivity to ABA. The relative increase of root numbers by optimal ABA tissue concentrations was higher in the cuttings from high irradiance than in those from low irradiance.
Effects of temperature on germination and mitochondrial dehydrogenases in two soybean (Glycine max) cultivars
Authors: HENSON CYNTHIA A. , SCHRADER LARRY E. , DUKE STANLEY H.
Published: April 2006

The effects of eight germination temperatures from 10°C to 35°C on germination and dehydrogenase activities of two soybean (Glycine max [L.] Merr.) cultivars were investigated after 48 h of seedling growth. Axis fresh weights of cv. Chippewa increased as germination temperature increased from 10°C to 35°C. In contrast, axis fresh weights for the cv. Wells increased more slowly with increasing temperature and reached a maximum at c. 25°C. In general, in vitro activities of glutamate dehydrogenase (GDH), NADP‐isocitrate dehydrogenase (NADP‐ICDH), and malate dehydrogenase (MDH) from the axes of cv. Chippewa correlated well with increases in axis fresh weights. GDH and MDH activities from axes of the cv. Wells also reflected increases in axis fresh weights although the correlation was not as evident as for the cv. Chippewa. NADP‐ICDH activity from ‘Wells’ axes was highest at 35°C even though germination was poor at this temperature. GDH and MDH activities from cotyledons of both cultivars were not correlated with axis weight increases. No GDH activity was detected in ‘Wells’ cotyledons from seeds germinated at 35°C.
Fractionation of leaf proteins by differential centrifugation and gel filtration
Authors: LUNDBORG TOMAS
Published: April 2006

The quantity and quality of fractionated leaf proteins from different plant species were investigated. Leaf extracts (pH range 7.0–8.3) were prepared on a laboratory scale from greenhouse cultivated plants. The proteins were fractionated by differential centrifugation followed by gel filtration.

Amaranthus caudatus and Chenopodium quinoa seem favourable for production of non‐green leaf protein concentrates, since the water‐soluble protein comprised nearly 50% of the extracted protein. The chlorophyll‐associated protein in fresh extracts from these species was, however, difficult to sediment. A practical separation of chlorophyll‐associated protein from the chlorophyll‐free proteins will require some kind of pre‐aggregation of the chlorophyll‐associated proteins.

In extracts from Dactylis glomerata, Lolium perenne and Vicia sativa a considerable proportion of the extracted protein sedimented rapidly, but at least for the grasses some of the chlorophyll‐associated protein remained in the supernatants even after centrifugation at 30 000 g for 180 min. Practical separation of all the chlorophyll‐associated protein from the extract requires some kind of pre‐aggregation of the chlorophyll‐associated proteins even for these species. The situation was similar for extracts from Helianthus annuus, but a very high percentage of the total chlorophyll‐associated proteins could be sedimented at low centrifugation speed.

Brassica oleracea was the most suitable species for the removal of the chlorophyll‐associated proteins by centrifugation alone. Moreover, the proportion of chlorophyll‐free protein in the extracts was relatively high, more than 40%.

The in vitro digestibility of membrane‐bound protein fractions was high for species with co‐aggregation of water‐soluble protein and membrane‐bound protein. Causes underlying the different distributions of the chlorophyll‐associated and chlorophyll‐free proteins and the reason for the different size of the chlorophyll‐containing particles are discussed.
Regenerated cell wall of carrot protoplasts isolated from suspension‐cultured cells
Authors: ASAMIZU TETSUYA , NISHI ARASUKE
Published: April 2006

Protoplasts of Daucus carota L. cultured in a synthetic liquid medium resumed cell division after about 4 days of cultivation. During this lag period, nucleic acid and protein showed only slight increases but the protoplasts commenced cell‐wall regeneration soon after the removal of lytic enzymes. The originally spherical protoplasts became ellipsoidal before they underwent division. Radioactive glucose and myo‐inositol were readily utilized by the protoplasts. Most of the radioactivity, however, appeared in extracellular polysaccharides and only a small portion was deposited in the regenerated wall. The sugar composition of new cell wall, as studies by chemical analysis and incorporation of labelled precursors, was shown to be considerably different from that of normal cell wall.
No contribution of the pentose phosphate pathway in dormancy‐breaking of cocklebur seeds
Authors: SATOH SHIGERU , ESASHI YOHJI
Published: April 2006

The role of the oxidative pentose phosphate (PP) pathway in the dormancy‐breaking of cocklebur (Xanthium pennsylvanicum Wallr.) seeds was investigated. D‐[1‐14C]‐glucose or D‐[6‐14C]‐glucose was fed to dormant and non‐dormant lower seeds or to their axial or cotyledonary segments which were imbibed for different durations, and C6/C1 ratios of respired 14CO2 as an index of the PP pathway activity were calculated. Contrary to expectation, there was no significant difference in the C6/C1 ratios between the dormant and non‐dormant seeds or segments during a water imbition period of 24 h, although the PP pathway actually operated already in an early stage of water imbibition. Also concerning the activities of G6PDH and 6PGDH, the key enzymes of this pathway, no difference between the dormant and non‐dormant seeds was found. It was thus concluded that, unlike other seeds, there is no contribution of the PP pathway to the regulation of dormancy of the cocklebur seed.
Photophosphorylation in Scenedesmus in vivo: O2 evolution, ATP pools and transients, and phosphate binding during photoreduction of NO3−, NO2− and CO2
Authors: LARSSON C.‐M.
Published: April 2006

The relation between light‐induced electron transport with NO3−, NO2− or CO2 as acceptors, ATP pools and transients in dark‐light‐dark transitions, and phosphate uptake was examined in phosphorus‐starved cells of Scenedesmus obtusiusculus Chod. Net O2 evolution at saturating light was around 6 μmol × (mg chlorophyll × h)−1 in the absence of any acceptor, but reached average rates of 21, 65 and 145 μmol × (mg chlorophyll × h)−1 upon additions of 5 mM KNO3, KNO2 and KHCO3, respectively. The apparent rate of photophosphorylation in transition experiments was only a few percent of the rate calculated from CO2‐dependent O2 evolution. Blocking non‐cyclic electron transport with DCMU inhibited phosphate assimilation, but acceleration of non‐cyclic electron flow by addition of NO3− or NO2− did not stimulate phosphate assimilation as compared to the situation without an acceptor. A functional non‐cyclic system might primarily be needed for an efficient shuttle transfer of ATP from the chloroplast to the cytoplasm. An inhibition of the non‐cyclic system due to lack of reducible substrates accelerates the cyclic system and thus indicates a regulation mechanism between the two systems.
Factors affecting in vivo nitrate reductase activity in triticale
Authors: LIN WEI HO , KAO CHING HUEI
Published: April 2006

Factors influencing in vivo nitrate reductase activity in triticale (×Triticosecale Wittmack) primary leaves were investigated. Nitrate reductase activity was found to be a function of reaction time or tissue weight. In the range of 1–10 mm, the optimum slice width for nitrate reductase activity in triticale was found to be 1–2 mm. The optimum exogenous nitrate concentration is 300 mM. Substantial nitrite production was obtained even when exogenous nitrate was omitted from the assay. Of the five low molecular weight organic solvents tested, n‐propanol is the most effective in enhancing enzyme activity. The optimum n‐propanol concentration is 1% (v/v). The concentration of phosphate buffer (pH 6) does not affect nitrate reductase activity. Enzyme activity drops significantly below or above pH 6. In our system, nitrite production is enhanced by incubating under nitrogen, instead of air. The highest level of in vivo activity of nitrate reductase was found to be 10–15 cm from tip, which is close to the basal meristem of triticale primary leaves. Younger but physiologically mature leaves have higher nitrate reductase activity than old leaves.
Photosynthetic studies with mesophyll protoplasts from Notonia grandiflora, a crassulacean acid metabolism plant
Authors: CHELLAPPAN K. P. , SEENI S. , GNANAM A.
Published: April 2006

A method is described for rapid enzymatic isolation of mesophyll protoplasts and cells from the crassulacean acid metabolism (CAM) plant Notonia grandiflora DC. The mesophyll protoplasts exhibited high rates of 14CO2 fixation both in the light (45 μmol of CO2 fixed mg−1 Chl h−1) and in the dark (20 μmol of CO2 fixed mg−1 Chl h−1). The protoplasts also showed O2 evolution (40 μmol of O2 evolved mg−1 Chl h−1) without added bicarbonate. Exogenously added bicarbonate had no stimulating effect on the O2 evolution. Analyses of early photosynthetic products in the light showed the formation of both C3 and C4 acids. Aspartate was found to be a predominant photosynthate.
Nitrogen assimilation in citrus trees
Authors: KATO TADASHI
Published: April 2006

Assimilation of 15N‐ammonium and 15N‐nitrate was examined in 3‐year‐old satsuma mandarin (Citrus unshiu Marcovitch) trees. Experiments were designed to establish the time course of incorporation of nitrogen just taken up into amino compounds.

In fine roots, absorbed 15N‐ammonium was actively incorporated into glutamine and then into glutamic acid and asparagine. When feeding 15N‐nitrate, glutamic acid and asparagine were actively synthesized, but glutamine synthesis was comparatively low as compared with that in ammonium feeding. In current leaves and fruits, a clear difference in the labelling patterns of amino acids was found between the ammonium and nitrate feedings. The amino acid most markedly labelled was asparagine in the ammonium feeding and glutamine in the nitrate feeding. Considering the most heavily labelled component in leaves and fruits, the main form of the nitrogen components transported upward in the xylem was discussed.
Action of the herbicides neburon and siduron on membrane permeabilities in potato tuber mitochondria
Authors: GAUVRIT CHRISTIAN
Published: April 2006

The herbicides neburon and siduron are uncouplers of oxidative phosphorylation in potato tuber (Solanum tuberosum L. cv. Bintje) mitochondria. Their effect on the ion permeabilities of the mitochondrial membrane was investigated using the acid‐base pulse technique, swelling experiments and integrity tests. Both herbicides permeabilize the membrane to H+ ions. They have no action on the permeabilities of K+ and Fe(CN)3−6. The swelling observed with Ca2+ was better interpreted as an effect on membrane structure than as a true swelling. Diuron, a parent compound that does not uncouple oxidative phosphorylation, does not act on Ca2+‐induced apparent swelling.
Coumarin effects on Glycine max hypocotyl explants
Authors: JANSSON EVA , SVENSSON SVEN‐BÖRJE
Published: April 2006

Coumarin induced root formation and stimulated fresh weight production in hypocotyl explants of Glycine max L. cultured in vitro. All stimulatory effects caused by coumarin were induced within a relatively narrow range of concentrations between 1–500 μM, yielding optimum dose response curves. When coumarin was combined with kinetin fresh weight increased considerably, at optimum concentrations to a level almost as high as that obtained with NAA (10 μM) and kinetin (10 μM). Root formation was almost completely inhibited when kinetin was added in combination with coumarin. NAA + coumarin had small stimulatory effects on fresh weight. but were inhibitory in root formation. The frequency of rooting per explant, texture and pigmentation were also affected by different treatments.
Effects of artificial frost hardening and winter stress on net photosynthesis, photosynthetic electron transport and RuBP carboxylase activity in seedlings of Pinus silvestris
Authors: ÖQUIST GUNNAR , BRUNES LAILA , HÄLLGREN JAN‐ERIK , GEZELIUS KERSTIN , HALLÉN MONICA , MALMBERG GUNILLA
Published: April 2006

Net photosynthesis of seedlings of Pinus silvestris has been measured and compared with the activities of photosynthetic electron transport and extracted RuBP carboxylase. The effects of prolonged frost hardening (photoperiod 8 h, + 3°C) followed by winter stress at subzero temperatures were analysed. There was a parallel effect of frost hardening and winter stress on the photosynthetic properties of both intact seedlings and isolated chloroplast thylakoids. The activity of extracted RuBP carboxylase was less affected by the treatments. In relation to earlier works we conclude that the decay of net photosynthesis in winter climate is determined by the electron transport properties of the chloroplast thylakoids, i.e. by the pool sizes of photosynthetically active plastoquinone.

The results of this work justify the definition of two phases in the response of conifers towards autumn and winter climates: I. Frost hardening occurs at temperatures slightly above zero and it does not affect the efficiency of photosynthesis as defined by the quantum yield at rate limiting light absorption. II. Winter stress occurs at subzero temperatures and it is characterized by a suppression of the photosynthetic efficiency as a result of damage within the photosynthetic apparatus.