bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of a day at low irradiance of a maize crop
Authors: Massimino D. , André M. , Richaud C. , Daguenet A. , Massimino J. , Vivoli J.
Published: April 2006

During the growth of maize (Zea mays L.cv. INRA F7× F2) under constant climatic conditions, the effects of reductions in irradiance simulating a cloudy day were studied. Hourly and daily measurements made in an assimilation chamber (C2 3A) showed important and lasting effects in root activity. After reduction of photosynthesis, it took approximately 2 hours to start a lowering of the uptake of NO3− and NH4+, three hours for K+ and four hours for phosphate. Root respiration started to fall after 3 hours. The level to which these activities were reduced also varied. Phosphate uptake was reduced by a mean of 27%, nitrate uptake by 47%, and K+ uptake by 55% while the root respiration was reduced by 55%. After return to the initial irradiance, root activities took 3 days to recover their initial rates. Shoot respiration was re‐established after one day, while the effects on photosynthesis and transpiration were immediate. The delay of the effect of a change of photosynthesis on the activities of the root, indicates the existence of considerable metabolic reserves. Over longer periods, root metabolism depends on photosynthetic assimilates, but in the short term it is much more dependent on the level of metabolic reserves than on the direct flow of photosynthetic translocates.
Growth, peroxidase activity, and protein content in stem pith and callus tissues from haploid and diploid Nicotiana tabacum plants
Authors: Kraus Jane E. , Handro Walter , Dietrich Sonia M. C.
Published: April 2006

Pith segments isolated from haploid and diploid Nicotiana tabacum cv. IAC‐70 plants from five different heights in the stem, were cultured in vitro on MS‐62 medium supplied with 0.5 mg/l IAA and 0.02 mg/l kinetin. Pith tissues of haploid plants showed greater growth potential than those of diploids; peroxidase activity was higher in the calluses of diploid tissues whereas protein content was higher in those of haploids. After three subcultures the growth pattern was inversed, as were the results for peroxidase activity and protein content. After the onset of culture, peroxidase activity in haploid explants dropped sharply, reaching values lower than in diploid tissues 40 d later, but after three subcultures these values were higher than those for diploid calluses. The results are discussed from the viewpoint of a possible relationship between greater polyploidization in haploid tissues on the one hand and growth decrease and peroxidase activity increase on the other.
Development of leaf thickness for Plectranthus parviflorus – Influence of photosynthetically active radiation
Authors: Nobel Park S. , Hartsock Terry L.
Published: April 2006

Photosynthetically active radiation (PhAR) is apparently the environmental factor having the greatest influence on leaf thickness for Plectranthus parviflorus Henckel (Labiatae). A four‐fold increase in leaf thickness from 280 to 1170 μm occurred as the PhAR was raised from 1.3 to 32.5 mol m−2 day−1. Compared to a constant PhAR of 2.5 mol m−2 day−1, a PhAR of 32.5 mol m−2 day−1 for one week during the first week (with return to 2.5 mol m−2 day−1 during the second and third weeks) led to an increase in final leaf thickness by 323 μm (to 802 μm). When increased PhAR was applied during the second week the increase in final thickness over the control was 217 μm, and when increased PhAR was applied during the third week it was 99 μm. However, leaf thickness was not simply responding to total daily PhAR, since a leaf 450 μm thick could occur at a low instantaneous PhAR for a long daytime (total daily PhAR of 1.5 mol m−2 day−1) and at a high PhAR for a short daytime (4.5 mol m−2 day−1). Total daily CO2 uptake (net photosynthesis) was approximately the same in the two cases, suggesting that this is an important factor underlying the differences in leaf thickness. Leaf thickness is physiologically important, since thicker leaves tend to have greater mesophyll surface area per unit leaf area (Ames/A) and hence higher photosynthetic rates.
The chemical form and physiological function of nickel in some Iberian Alyssum species
Authors: Brooks R. R. , Shaw S. , Asensi Marfil A.
Published: April 2006

The form of nickel in leaves of Iberian subspecies of Alyssum serpyllifolium Desv. was investigated. Subsp. lusitanicum T. R. Dudley and P. Silva (from N.E. Portugal) and subsp. malacitanum Rivas Goday (from Southern Spain) were hyperaccumulators of nickel (>1000 μg/g Ni) whereas their non‐accumulating precursor (subsp. serpyllifolium) was not. Nickel existed mainly as a water‐soluble polar complex in the vacuoles. Small concentrations of nickel did however exist in cell fractions, particularly in the mitochondria where enzyme systems are located. Gas‐liquid chromatography on the purified nickel complexes showed that this element is associated principally with malic and malonic acids which are present in high concentrations in the hyperaccumulators but not in subsp. serpyllifolium. It is suggested that production of malic acid is a mechanism whereby hyperaccumulators can tolerate unfavourable edaphic factors such as nickel‐rich soils. Presence of nickel in the mitochondria can presumably block the citric acid cycle by deactivating malic dehydrogenase leading to build‐up of malic acid in the vacuoles which could then absorb excess nickel by a complexing reaction and lead to its diffusion back into the vacuoles from the mitochondria, hence unblocking the citric acid cycle. It is postulated that the chemical evidence suggests that the two hyperaccumulators are not conspecific and that subsp. malacitanum should be promoted to full specific rank.
Effect of carbon dioxide enrichment on chlorophyll content, starch content and starch grain structure in Trifolium subterraneum leaves
Authors: Cave George , Tolley Leslie C. , Strain B. R.
Published: April 2006

Trifolium subterraneum (cv. Dinninup) responds to enriched atmospheric CO2 in a manner similar to that described by Madsen (1968 and 1976) for tomato. In immature leaves, the total chlorophyll content per unit dry weight and the chlorophyll a:b ratio are significantly lower in plants grown at 0.10 vol% CO2. Although fully expanded mature leaves partially overcome the deficit in chlorophyll content, the chlorophyll a:b ratio remains substantially lower in these high CO2 grown plants. The large amount of starch accumulated as irregularly shaped grains appears to disrupt normal chloroplast structure in clover plants grown in enriched atmospheric CO2. These results indicate the chlorotic appearance of leaves from high CO2 grown clover plants is due to a decrease in chlorophyll content per dry weight possibly resulting from large starch grains and starch accumulation altering normal chloroplast structure and function.
Short‐term pigment changes in Norway spruce needles
Authors: Hawkins C. D. B. , Lister G. R. , Fink R. P. , Vidaver W. E.
Published: April 2006

The photosynthetic pigment contents and the chlorophyll fluorescence induction in Norway spruce [Picea abies (L.) Karst.] needles were monitored at 3 h intervals over a 10 day period. This covered 6 days of high insolation, one day of low insolation, followed by three more days of high insolation. During the first six days only small changes in mean pigment contents were observed but we interpret them as suggesting a daily rhythm in total chlorophyll content with two maxima and minima. The day of low insolation was paralleled by larger pigment changes, mostly an increase in chlorophyll b along with a decrease in carotenoid content. With the resumption of high insolation, pigments gradually return to their previous levels. During the entire period chlorophyll a fluorescence induction remained relatively constant. These short‐term responses may reflect features of thylakoid organization in relation to pigment content and suggest possible long‐term adaptive mechanisms in non deciduous conifers.
Effects of bud removal in Scots pine (Pinus silvestris) seedlings
Authors: Gezelius Kerstin , Ericsson Anders , Hällgren Jan‐Erik , Brunes Laila
Published: April 2006

One‐ and two‐“year”‐old seedlings of Pinus silvestris L., from which the buds had been removed, were studied for five weeks during the second and third growth period, respectively. Intact seedlings were used as controls. The seedlings were cultivated under controlled conditions in a climate chamber. The growth of the seedlings was determined and the one‐“year”‐old needles assayed for changes in net photosynthesis and ribulose bisphosphate carboxylase activity and in the levels of protein, Kjeldahl nitrogen, chlorophyll and starch.

In the control the carboxylase activity and the content of protein, Kjeldahl nitrogen and starch in the needles increased in the beginning of the “summer” and decreased during the shoot growth period. The starch content was higher after bud removal (decapitation), since the carbohydrate could not be utilized for the growth of the new shoot. Decapitation did not affect the growth rate of the roots.

The content of Kjeldahl nitrogen and total and soluble protein in the needles was higher in the decapitated seedlings during the period of shoot elongation in the control. Total nitrogen, but not protein, reached high levels, indicating accumulation of non‐protein compounds. The general course of the chlorophyll pattern was not affected. Higher ribulose bisphosphate carboxylase activity than in the control was observed in the later part of the experimental periods. The higher levels of protein and nitrogen as well as of carboxylase activity after decapitation support the interpretation that soluble protein, including the carboxylase, and possibly other nitrogen compounds in the older needles are used for growth of the shoot. The loss of protein and nitrogen and of carboxylase activity in the control did not seem to be due to mineral deficiency in the substrate.

Despite higher levels of carboxylase activity and similar chlorophyll concentrations, light‐saturated net photosynthesis was lower after decapitation. The ratio between photosynthesis and photorespiration was not affected.
Translocation of labelled assimilates following photosynthesis of 14CO2 by the field bean, Vicia faba
Authors: Crompton Hilary J. , Lloyd‐Jones C. P. , Hill‐Cottingham D. G.
Published: April 2006

When whole plants were exposed to 14CO2, almost the same amount of radioactivity was taken up initially by each leaf regardless of its position on the stem and of the presence of beans at that node. Thus, although developing beans are a powerful sink for assimilated carbon, they do not increase the CO2 uptake by adjoining leaves.

The distribution of labelled assimilates 6 hours after feeding 14CO2 to a single leaf for 1 hour varied with both the position of the treated leaf and the stage of development of the plant. Before any flowers were set most of the radioactivity from all expanded leaves moved downwards to the roots and the stem below the treated leaf (lower stem). Later, during pod‐fill, the upper leaves maintained this supply to the roots and lower stem, whilst most of the carbon translocated from the lower and mid‐stem leaves went to the beans. However, we found no exclusive relationship between a leaf and the supply to beans developing on the same node.

The amount of radioactivity moving out of a source leaf at a fruiting node increased over successive samplings up to 48 h; the pattern of distribution of the 14CO2 however remained virtually unchanged.
Cytophotometric study and statistical analysis of ploidy evolution in cultured tissues of Nicotiana tabacum
Authors: de Boucaud Marie‐Thérèse , Gaultier Jean‐Maurice
Published: April 2006

Evolution of the ploidy in four strains of Nicotiana tabacum ev. P 19 was studied by cytophotometry after transformation of the cultured tissues into protoplast suspensions.

The limits of these variations were analysed numerically and statistically. The method used is capable of wide application. It can be used to predict the evolution of the average ploidy level of a strain maintained on a given medium if the average ploidy level of the explant is known. Comparison is made relative to a standard of known ploidy (diploid protoplasts). Increase of the average ploidy level is faster when the explant is mainly diploid (leaf parenchyma) than when it is composed of more heterogeneous tissues as regards ploidy (shoot tip). The appearance of a random drift depends on the composition of the culture medium: it is immediate in one medium (MS2), but is preceded by a phase of relative stability in another medium (MS1) which is richer in kinetin.

While the results presented specifically concern the strains cultured on media MS1 and MS2, the statistical method employed is applicable to cultures of any species for which one can experimentally justify a linear regression analysis.
Differences in salt tolerance of three sugar beet genotypes
Authors: Marschner H. , Kylin A. , Kuiper P. J. C.
Published: April 2006

The effect of increasing NaCl concentrations (up to 150 mM) on growth and mineral composition of three genotypes of sugar beet (Beta vulgaris L., MONOHILL, ADA and FIA) has been studied. Growth was stimulated or little affected in water culture by 50 mM NaCl in all 3 genotypes. Further increase in NaCl concentration depressed growth in ADA more than in MONOHILL, whereas in FIA growth did not significantly differ from the untreated control. In all 3 genotypes, particularly in FIA, increasing NaCl concentrations decreased potassium content in the shoots more than in the fibrous and storage roots. Simultaneously, the accumulation of sodium and chloride in the shoots was considerably higher in FIA than in ADA, where in contrast larger proportions of these ions were retained in the roots. The results demonstrate considerable genotypic differences in salt tolerance of sugar beet and indicate a positive correlation between salt tolerance and accumulation of sodium and chloride in the shoots. FIA but not ADA may be suited for a breeding programme of sugar beet for improved salt tolerance.
Genotypic differences in the response of sugar beet plants to replacement of potassium by sodium
Authors: Marschner H. , Kuiper P. J. C. , Kylin A.
Published: April 2006

The effect of replacing 50% or 95% of the potassium by sodium on growth and on potassium and sodium levels in three genotypes of sugar beet (MONOHILL; ADA; FIA) has been studied in water culture over a period from 2 to 9 weeks.

In all three genotypes there was a preferential uptake of potassium compared to sodium. Nevertheless, at high sodium supply most of the potassium was replaced by sodium, particularly in the leaves. At the same supply the accumulation of sodium in the leaves increased in the following order: ADA < MONOHILL < FIA. Even with high dominance of sodium in the medium, the youngest leaves of FIA held about 0.5 mmol potassium per g dry matter, and potassium was evidently translocated from old leaves to the new growth.

Effects of sodium on growth became more important with time. After 9 weeks, 50% replacement of potassium by sodium increased growth of all plant organs of the three genotypes. Replacing 95% of potassium by sodium depressed growth of the storage root in MONOHILL and particularly in ADA, with simultaneous enhancement of leaf growth in the latter. In FIA, however, this treatment further stimulated both leaf and, particularly, storage root growth. Sodium in comparison with potassium increased the sucrose concentration in leaves and storage roots. The highest sucrose concentration in the storage roots of ADA and FIA was obtained in the treatment with 95% sodium.

The results demonstrate pronounced genotypic differences in sugar beet with respect to the response to sodium. FIA has the most natrophilic behaviour and might be a promising genotype for breeding programmes for adaptation of sugar beet plants to soils high in sodium.
Effect of abscisic acid on CO2 exchange in Lemna gibba
Authors: Tillberg Elisabeth , Dons Christian , Haugstad May , Nilsen Stein
Published: April 2006

The effects of abscisic acid (ABA) on photosynthesis, dark respiration, and photorespiration were studied in Lemna gibba L. plants. The initial concentration of ABA in the nutrient solution was 10−7M and in a few experiments, 10−6M. The cultures were grown in the same solution for time periods ranging from one hour to 12 days. Net photosynthesis, measured as CO2 uptake by infrared gas analyser technique, was inhibited after four hours of ABA treatment and reached a minimum after four to seven days depending on the time of the year. After 12 days a substantial recovery of photosynthesis was observed. Dark respiration was significantly stimulated after two to seven days of ABA treatment but then returned to the control level. The transient effects of ABA on photosynthesis and dark respiration corresponded to the previously measured time course of [14C]‐ABA uptake by Lemna. Photorespiration measured as oxygen inhibition of photosynthesis was not affected by ABA.
Passive uptake of K+(86Rb+) in sunflower roots at low external K+ concentrations
Authors: Pettersson Sune
Published: April 2006

Passive fluxes of K+ (86Rb) into roots of sunflower (Helianthus annuus L. cv. Uniflorus) were determined at low K+ concentration (0.1 and 1.0 mM K+) in the ambient solution. Metabolic uptake of K+ was inhibited by 10−4M 2,4‐dinitrophenol (DNP). K+ (86Rb) fluxes were studied both continuously and by time differentiation of uptake. In high K+ roots passive uptake was directly proportional to the K+ concentration of the uptake solution, indicating free diffusion. This assumption was supported by the fact that passive Rb+ uptake was not affected by high K+ concentrations. In low K+ roots the passive uptake of K+ was higher than in high K+ roots. The increase was possibly due to carrier‐mediated K+ transport. As K+ effluxes were quantitatively similar to influxes, it is suggested that passive K+ fluxes represent exchange diffusion without relation to net K+ transport.
Changes of membrane‐associated Mg2+‐activated ATPase of cucumber roots during calcium starvation
Authors: Matsumoto Hideaki , Kawasaki Toshio
Published: April 2006

The properties of membrane‐associated ATPase of cucumber (Cucumis sativus cv. Seiriki No. 2) roots cultured in a complete medium (complete enzyme) and in a medium lacking Ca2+ (Ca2+‐deficient enzyme) were investigated. The basal activity of membrane‐associated ATPase increased during Ca2+ starvation, while Mg2+‐activation of the enzyme decreased and even resulted in inhibition by high Mg2+ concentration at the late stage of the Ca2+ starvation. The complete enzyme had low basal activity and showed a Mg2+‐activated hyperbolic reaction curve in relation to ATP concentration. Ca2+‐deficient enzyme with high basal activity showed a biphasic reaction curve and Mg2+‐activation was seen only at high ATP concentrations. Activation of membrane‐associated ATPase by various cations was decreased or lost during Ca2+ starvation. The basal ATPase activity of Ca2+‐deficient enzyme increased for various substrates including pyrophosphate, p‐nitrophenyl phosphate, glucose‐6 phosphate, β‐glycerophosphate, AMP, ADP and ATP. Mg2+‐activation was found only for ADP and ATP in both the complete and Ca2+‐deficient enzymes, but the activation for ATP was greatly reduced by Ca2+ starvation. The heat inactivation curves for basal and Mg2+‐activated ATPase did not differ much between the complete and Ca2+‐deficient enzyme. The delipidation of membrane‐associated enzyme by acetone affected the protein content and the basal activity slightly, but inhibited the Mg2+‐activated ATPase activity clearly with somewhat different behaviour between the complete and Ca2+‐deficient enzyme.
Survival of Solanum tuberosum suspension cultures to –14°C: The mode of action of proline
Authors: Hellergren J. , Li P. H.
Published: April 2006

Normally suspension cultures of potato, Solanum tuberosum, can survive only to a freezing temperature of –2°C. The treated cultures were able to survive at much lower freezing temperature after the addition of l‐proline of 0.43 M or more to the suspension medium and treatment for 1.5 h. Cultures could survive to ‐14°C with 0.87 M proline treatment. Treatments with higher concentration than 0.87 M resulted in no additional freezing survival. Microscopical observations of the treated cultures before freezing showed that proline induced plasmolysis, which was initiated at the 0.43 M level and reached maximum at 0.87 M. The mode of action of proline, appears to be due to the removal of excessive intracellular water by the osmotic gradient. Sucrose at about the same concentration acted in the same way as proline. The cryoprotective role of proline and sucrose is discussed in relation to the action of the permeant dimethylsulfoxide.
Fusicoccin structure‐activity relationships: In vitro binding to microsomal preparations of maize coleoptiles
Authors: Ballio A. , Federico R. , Scalorbi D.
Published: April 2006

The ability of a number of fusicoccin (FC) derivatives and analogues to compete with tritiated dihydro‐FC in a binding test to microsomal preparations of maize (Zea mays L. variety XL 342) coleoptiles has been investigated. The binding affinity of each compound, expressed as the concentration of unlabeled ligand at which the maximum specific binding of labeled dihydro‐FC is displaced by 50% (IC50), has allowed to quantitate structure‐activity relationships by this test. The results largely confirm previous data of in vivo assays, and show that a. the role of the glucose moiety is only secondary to that of the aglycone, b. an unsubstituted OH on C‐8 and the configuration at C‐3 and C‐9 are important for an efficient binding, c. the conformation of the 8‐membered ring probably affects the interaction with the FC‐binding sites.
Hydroxycinnamic acid amides and ripening to flower of Nicotiana tabacum var. xanthi n.c.
Authors: Cabanne Ferdinand , Dalebroux Marc A. , Martin‐Tanguy Josette , Martin Claude
Published: April 2006

Two kinds of hydroxycinnamic derivatives can be found in tobacco: esters and amides. They do not accumulate in the same way during development. Esters, especially chlorogenic acids, are always present in all organs, whereas amides are observed only during certain periods in specific organs (from 47 days after sowing, in apical leaves, anthers and ovaries). A relationship has been found between accumulation of amides and flowering of plants grown at 20°C. By comparing amide accumulation as well as leaf emergence rate, both at a temperature that allows flowering (20°C) and at a temperature that inhibits flowering (30°C), it appears that amides begin to accumulate whenever a plant is ripening to flower.
Promotive effect of polyvinylpolypyrrolidone on pollen embryogenesis in Datura innoxia
Authors: Tyagi Akhilesh K. , Rashid A. , Maheshwari S. C.
Published: April 2006

Pollen embryos of Datura innoxia Mill are produced in larger numbers from anthers on agar‐gelled medium containing polyvinylpolypyrrolidone than on control. The best response is observed with 0.5% polyvinylpolypyrrolidone. The effect is possibly due to adsorption of substances (phenolics) emanating from cultured anthers and inhibiting the development of pollen grains into embryos.
The inhibition of exogenous NAD(P)H oxidation in plant mitochondria by chelators and mersalyl as a function of pH
Authors: Möller Ian M. , Palmer John M.
Published: April 2006

The oxidation of exogenous NADH by Jerusalem artichoke (Helianthus tuberosus L.) tuber mitochondria was strongly inhibited at pH 7.2 by EDTA, EGTA and mersalyl and by chlorotetracycline in the presence of Ca2+. This inhibition disappeared at pH 5.5 where about 50% activity was found as compared to controls at pH 7.2. The rate of oxidation of NADPH at pH 5.5 was the same as for NADH but it was inhibited by 50% by both EDTA and mersalyl.

Mitochondria from Arum maculatum spadices oxidised NADH and NADPH with pH optima of 7.2 and 6.5, respectively. In the presence of EDTA the optima shifted to 6.7 and 5.9, respectively, due to an inhibition at higher pH and a lack of inhibition at lower pH. At pH 6.7 NADH oxidation was completely insensitive to both EDTA and mersalyl whereas the oxidation of NADPH was inhibited by more than 50%. The inhibition of NAD(P)H oxidation by chelators at neutral pH was due to the removal of Ca2+ from the membranes in both types of mitochondria. The differences observed in the properties of NADH and NADPH oxidation suggest that two different dehydrogenases are involved. Because of the strong pH‐dependence and the changes in chelator‐sensitivity in the physiological pH‐range 6–8 it is suggested that the properties of NAD(P)H oxidation provide the cell with important means of metabolic regulation.
Tentoxin‐induced loss of plastidic polyphenol oxidase
Authors: Vaughn Kevin C. , Duke Stephen O.
Published: April 2006

Tentoxin‐treated mung bean plants are shown to lack chloroplast polyphenol oxidase (PPO) by enzymatic, electrophoretic and cytochemical analysis. Incorporation of PPO (a protein coded by nuclear DNA) into the plastid may occur via concentration of the protein into inner envelope‐derived vesicles. PPO integration into the plastid is apparently blocked by a tentoxin treatment although fraction I protein (and hence the proteins for chloroplast ribosome production) is not affected by this fungal toxin. Both apical and etiolated plastids from teotoxin‐treated plants lack PPO. Thus, it is unlikely that the primary effect of tentoxin is due to the binding of the chloroplast coupling factor, as previously supposed.
Role of β‐amylase in starch metabolism during soybean seed development and germination
Authors: Hildebrand D. F. , Hymowitz T.
Published: April 2006

Differences in starch metabolism during seed development and germination of two soybean [Glycine max (L.) Merrill] genotypes with normal seed β‐amylase activity [‘Williams’ (Sp1b and ‘Altona’ (Sp1b)] and two soybean genotypes with undetectable seed β‐amylase activity [‘Chestnut’ (Sp1au) and ‘Altona’ (Sp1)] were investigated. Starch and soluble sugar profiles were essentially the same during seed development and germination. Total amylase activity of Williams and Altona (Sp1b) peaked just prior to seed maturity and then dropped off slowly; whereas, the total amylase activity of Chestnut and Altona (sp1) was very low throughout seed development and germination. The differences in amylase activity between Altona (Sp 1 b) and Altona (sp 1) was also seen in leaves. α‐Amylase activity was similar in the four genotypes when β‐amylase was inhibited with Hg2+ but was higher in the two genotypes with normal β‐amylase activity when β‐amylase was inhibited with heat plus Ca2+. Low levels of starch phosphorylase activity were detected throughout seed development and germination, and the activity was similar in three of the genotypes and higher in Altona (sp 1).

The protein, oil and oligosaccharide contents of mature seeds of the four genotypes were similar. Altona (sp 1 b) and (sp 1), which appear to be near isogenic lines, were not different in any morphological character or yield.

Altona (Sp 1 b) showed greater hydrolysis of soybean seed starch than Altona (sp 1), but the evidence indicates that the mutation resulting in greatly reduced or missing β‐amylase activity has no effect on starch metabolism of developing and germinating soybean seeds.
Brassinolide, a growth‐promoting steroidal lactone
Authors: Mandava N. Bhushan , Sasse Jenneth M. , Yopp John H.
Published: April 2006

Brassinolide (BR), a naturally‐occurring steroidal lactone was compared with GA3 and kinetin for activity in a number of bioassays. BR was highly active in elongation bioassays employing the dwarf pea epicotyl and etiolated bean hypocotyl that are responsive to GA3 but not IAA (at 0.01 to 10 μM). The elongation of the cucumber hypocotyl elicited by BR and GA3 was reduced far more than that elicited by IAA, following removal of the cotyledons. BR, like GA3 also inhibited betacyanin accumulation in Amaranthus seedlings and prevented adventitious root initiation in hypocotyls of mung bean, dwarf bean and cucumber. Application of BR promoted rather than retarded senescence of Rumex leaves.

While almost half as effective as kinetin in promoting expansion of cucumber cotyledons, BR was ineffective in cytokinin bioassays involving expansion of dwarf pea epicotyl hooks, dark synthesis of betacyanin in Amaranthus and retardation of Xanthium leaf disc senescence. Unlike the case with IAA, BR does not interact synergistically with GA3. BR has proven active in promoting stem elongation in plant bioassays responsive to either IAA or GA3, or to both phytohormones. This effect, coupled to its effect on adventitious root formation, qualifies BR as a unique plant growth substance.
Interaction of Ancymidol and benzyladenine in control of growth of juvenile Hedera helix
Authors: Clark James R. , Hackett Wesley P.
Published: April 2006

The growth of the juvenile form of Hedera helix L. was greatly suppressed by soil drench treatment with the growth retardant, Ancymidol. Treated plants were smaller in stature, had fewer nodes and shorter internodes, accumulated less dry weight, had reduced leaf area, and lowered shoot: root ratios than untreated plants. In contrast, shoot tip application of the cytokinin, benzyladenine, increased stem diameter and shoot:root ratio over that of controls.

When Ancymidol and benzyladenine were applied together, reductions in plant growth were not evident – plants appeared as the untreated controls. The implications of this interaction are discussed.
Effect of chlorate, nitrogen source, and light on chlorate toxicity and nitrate reductase activity in soybean leaves
Authors: Harper James E.
Published: April 2006

Growth chamber studies were conducted to assess the relationship between nitrate reductase (NR) activity and development of chlorate (KClO3) toxicity symptoms in leaflets of soybeans [Glycine max (L.) Merr.]. Fourteen day‐old soybean seedlings, grown in NO3 ‐ or urea‐nutrient solutions, were exposed to various KClO3 concentrations (0 to 2.0 mM) and light levels (100, 67, 33 and 0% of full light which was 750 μE m−2s−1) for 24 h. Visual KClO3 toxicity symptoms were noted and NR activity was measured.

Toxicity symptoms (interveinal chlorosis) were evident within 24 h following addition of 0.5 mM KClO3 to the nutrient solution, regardless of N nutrition, and symptom severity increased with increased KClO3 concentration (up to 2.0 mM). Leaflet NR activity was lower following 24 h KClO3 treatments at concentrations of 0.5 mM and higher, indicating that ClO3 ‐ or some reduction product of ClO3 ‐ likely ClO2 ‐ was detrimental to enzyme functionality. The light study supported involvement of NR activity in KClO3 toxicity in that comparison of control and KClO3 treated plants exposed to decreased light levels revealed a decrease in NR activity of control plants parallel to a decrease in severity of KClO3 toxicity symptoms of treated plants. Urea‐grown plants, which have an apparent constitutive NR enzyme, were used to verify that the KClO3 toxicity symptoms were not simply N starvation symptoms due to competition of ClO3 ‐ and NO3 ‐ for uptake and reduction. In vivo NR assays also ruled out that ClO3 ‐ was decreasing NR activity through competition with NO3 ‐ for reduction sites. The close relationship between KClO3 toxicity symptoms and NR activity, in response to light treatments, suggested that KClO3 toxicity symptoms were associated with reduction of ClO3 ‐ to ClO2 ‐ by the NR enzyme. However, the possibility that a more direct photochemical reaction occurred in the presence of KClO3 to produce the toxicity symptoms could not be ruled out.
Shifts in the optimal temperature for nocturnal CO2 uptake caused by changes in growth temperature for cacti and agaves
Authors: Nobel Park S. , Hartsock Terry L.
Published: April 2006

When the day/night air temperatures were raised from 10°C/10°C to 30°C/30°C, the optimal tempearture for nocturnal CO2 uptake by six species of cacti and three species of agave shifted from an average of 12°C to an average of 20°C. The maximum rate of CO2 uptake was higher for Agave americana at the higher ambient temperature, lower for A. deserti, and much lower for A. utahensis, consistent with the relative mean temperatures of their native habitats. For the cactus Coryphantha vivipara, which had the greatest temperature shift observed (13°C), the halftime was 8 days for the upward shift and 4 days for the downward shift. The halftimes for the comparable shifts averaged 1.6 days for three other species of cacti and less than 1 day for two agave species. The shifts in the optimal temperature for nocturnal CO2 uptake were in response to changes in nighttime temperature, at least for C. vivipara, and reflected temperature responses of both the stomates and the chlorenchyma.
Rooting of etiolated stem segments of Populus robusta – interaction of temperature, catechol and sucrose in the presence of IAA
Authors: Pal Mohinder , Nanda K. K.
Published: April 2006

Etiolated stem segments of Populus robusta Schneid. were cultured in test solutions each containing 2.0 mg/1 of IAA in combination with varying concentrations of catechol or sucrose or both at 10 ± 2°C, 25 ± 1°C and 35 ± 1°C in the dark. Cuttings did not root in catechol in the presence of IAA alone at 10 ± 2°C. There was no mortality in this culture solution at this temperature. However, cuttings rooted in this culture solution at 25 ± 1°C and 35 ± 1°C and also showed mortality, which was more severe at 35 ± 1°C than at 25 ± 1°C and more severe at higher than at lower concentrations of catechol. Rooting occurred on cuttings in catechol in the presence of IAA and sucrose even at 10 ± 2°C and was strongly promoted at 25 ± 1°C and 35 ± 1°C. The mortality of segments caused by catechol was markedly lowered in the presence of sucrose at these temperatures. Sucrose thus antagonised the toxic effect of catechol.
Induction of anthocyanin synthesis in relation to embryogenesis in a carrot suspension culture: Correlation of metabolic differentiation with morphological differentiation
Authors: Ozeki Yoshihiro , Komamine Atsushi
Published: April 2006

A system in which anthocyanin synthesis could be induced under a defined condition, was established in a carrot suspension culture. A cell suspension culture of carrot (Daucus carota L. cv. Kurodagosun) was subcultured for more than a year in a medium containing 5 × 10−7M 2,4‐dichlorophenoxyacetic acid (2,4‐D). At every subculture the cultures were sieved through nylon screens and the cells and cell clusters collected in the size range of 31–81 μm were transferred to a fresh medium. When the cells were transferred to a medium without auxin, synthesis of anthocyanin was induced. Zeatin promoted anthocyanin synthesis in a medium lacking auxin, with maximum yields of anthocyanin obtained at 10−7 to 10−8M zeatin, 2,4‐D at higher concentrations than 10−7M inhibited anthocyanin synthesis completely. The sieved cells were fractionated by Ficoll density gradient centrifugation. Somatic embryos were formed in the fraction of higher density (>14% of Ficoll) in a medium containing 10−7M zeatin but lacking auxin, while synthesis of anthocyanin was hardly observed. On the other hand, cells in the fraction of lower density (<12% of Ficoll) synthesized anthocyanin in the same medium, but formed few embryos. Forty to fifty percent of the total cells in this lighter cell fraction synthesized anthocyanin at a maximum. The similarity between anthocyanin synthesis and embryogenesis was observed in the time course as well as in the effects of growth regulators. The correlation between metabolic and morphological differentiation is discussed.
Influence of abscisic acid on unidirectional fluxes and intracellular compartmentation of K+ and Na+ in excised barley root segments
Authors: Behl Rudolf , Dieter Jeschke Wolf
Published: April 2006

Using compartmental analysis, unidirectional fluxes of K+ and Na+ and their intracellular compartmentation in excised barley (Hordeum distichon L. cv. Kocher‐perle) root segments have been measured during a steady state in the presence or absence of ABA. Almost all flux rates were altered in the presence of external ABA, in particular the xylem transport R’ and the plasmalemma influx Øoc (see below) were strongly inhibited in the steady state. At the same time the presence of ABA induced a strong increase in the vacuolar K+ and Na+ content Qv and a decrease in the cytoplasmic one (Qc). Since the fluxes of an ion and its vacuolar or, in particular, cytoplasmic concentrations are interrelated, the ratios of fluxes originating from the cytoplasm and the cytoplasmic ion content were taken into account. On this basis ABA had the following effects: a) the secretion of K+ or Na+ to the xylem vessels was drastically inhibited; b) the plasmalemma K+ or Na+ efflux Øco was moderately stimulated and c) the tonoplast influx Øcv of Na+ was stimulated, while the tonoplast influx of K+ appeared to be unchanged (the decrease in Øcv being due to the decreased cytoplasmic K+ content). By a similar argument, also the apparent inhibition of the plasmalemma influx Øoc of K+ and Na+ in the steady state merely is an indirect effect of ABA. It only reflects the strong ABA‐induced decrease in the xylem transport, that governs the magnitude of Øoc in the steady state. The results are discussed with reference to possible regulatory functions of ABA. In this respect it is suggested that – in particular under conditions of stress – ABA might regulate cellular metabolic processes by changing the cytoplasmic K+ level.
Efficiency of the first steps of sulfate utilization by maize hybrids in relation to their productivity
Authors: Saccomani M. , Cacco G. , Ferrari G.
Published: April 2006

The genetic variability of the efficiency of the first steps of sulfate utilization and its correlation with productivity were evaluated in nine maize hybrids. 35SO42− uptake by excised roots, uptake by intact plant roots, translocation to leaves, and ATP sulfurylase in leaves were taken into account. Uptake rate by roots of intact plants did not show any pulse within 7 to 12 days from emergence, in contrast with the previously observed behaviour of excised roots during root elongation. The uptake rate of intact plants was positively correlated with that of excised roots, but the variability within the nine genotypes tested was less. Productivity was positively correlated with sulfate uptake by both intact plant and excised roots, the level of significance being higher in the first case. Translocation to leaves and ATP sulfurylase activity were not correlated to productivity. Therefore, in the case of sulfate, the grain yield of commonly cultivated maize hybrids appeared to be controlled more by the root uptake step than by the activation and translocation steps.
The photostability of different chlorophyll forms in dark grown leaves of wheat
Authors: Axelsson Lennart
Published: April 2006

Formulae were developed for calculation of the relative amount of different pigment forms of dark grown leaves of wheat, present before and after photoreduction of the protochlorophyllide. Three pigment forms were calculated from in vivo absorption spectra: the photoreducible protochlorophyllide with absorption maximum at 650 nm and the two chlorophyll(ide) forms with absorption maximum at 684 nm and 673 nm, respectively. The formulae were used to study the changes of the pigment forms at repeated photoreduction of the protochlorophyllide, and at a repeated treatment involving photoreduction of the protochlorophyllide followed by partial photo‐decomposition of the chlorophyllide formed.

Five consecutive photoreductions and reaccumulations of protochlorophyllide were carried out by high intensity irradiations of one second (red light, 700 W m‐2) given at intervals of 3 h. The results show that the pool size of reaccumulated protochlorophyllide decreased sharply with the number of photoreductions performed. The absorption spectrum of the chlorophyllide formed at each photoreduction proceeded through the Shibata shift (transformation of the 684‐form to the 673‐form) and the late red‐shift (transformation of the 673‐form to other pigment form(s) in the dark).

High intensity irradiation for ten minutes (red light, 700 W m‐2) immediately after each phototransformation caused a photodecomposition of about three quarters of the newly formed chlorophyllide (which was in the 684‐form) while the earlier formed chlorophyll(ide) (in the 673‐form) appeared not to be decomposed. This partial photodecomposition of the chlorophyllide had no effect on further accumulation of protochlorophyllide in the dark, and the absorption spectrum of the remaining chlorophyllide proceeded through the Shibata shift. The partial photodecomposition caused an inhibition of the late red‐shift, and the accumulated chlorophyll(ide) remained in the 673‐form.
Mass propagation of globe artichoke (Cynara scolymus): Evaluation of different hypotheses to overcome vitrification with special reference to water potential
Authors: Debergh P. , Harbaoui Y. , Lemeur R.
Published: April 2006

In search of a technique for rapid clonal propagation and sanitation of Cynara scolymus L. we have been confronted with the problem of vitrification.

We only succeeded in overcoming this problem by raising the agar concentration of our medium to 1.1% instead of 0.6%. By using the Chardakov‐method and direct measurement of the water potential with a thermocouple psychrometer we were able to prove that this result was attributable to the matric potential.
The effect of different carbon and nitrogen sources on the activity of glutamine synthetase and glutamate dehydrogenase in lupine embryonic axes
Authors: Ratajczak L. , Ratajczak W. , Mazurowa H.
Published: April 2006

Embryos of yellow lupine (Lupinus luteus L. cv. Jantar), deprived of cotyledons, were incubated for 72 h in media containing various combinations of saccharose, ammonia, nitrate, glutamine and asparagine. Induction of glutamine synthetase (GS) was observed in embryos in media containing saccharose while the activity of this enzyme was inhibited by glutamine, asparagine and ammonia in the absence of sugar. The above mentioned nutritional factors had an opposite effect on the activity of glutamate dehydrogenase (GDH). Changes in glutamate dehydrogenase activity were preceded by reverse changes in the activity of glutamine synthetase. The possibility of GDH repression by GS in lupine embryos is discussed.
DNA changes during sequential leaf senescence of tobacco (Nicotiana tabacum)
Authors: Dhillon Sukhraj S. , Miksche Jerome P.
Published: April 2006

Age related DNA changes in tobacco (Nicotiana tabacum) leaf nuclei were investigated by Feulgen cytophotometry, thermal denaturation, renaturation, and DNA‐DNA hybridization studies during sequential leaf senescence. Cytophotometric Feulgen‐DNA comparison measurements between young and senescing nuclei displayed 18% reduction in Feulgen‐DNA values, with a corresponding decrease in nuclear area in senescing nuclei. Hydrolysis kinetics indicated that the loss was not due to compactness of the DNA as the curves for older nuclei were consistently lower than curves generated from younger nuclei. DNA loss in senescing nuclei was associated with a decrease in euchromatin or shift from euchromatin to facultative heterochromatin. Purified DNA from young and senescing leaf nuclei did not display different thermal profiles nor did hydroxylapatite chromatography reassociation curves. DNA‐DNA hybridization in free solution from young and senescing leaf DNA performed by a Gilford thermo‐programmer system indicated that DNA of senescing tobacco nuclei reassociated more slowly than DNA from young nuclei and the mixture of young and senescing leaf DNA displayed intermediate reassociation values. The study indicates that the DNA changes during senescence involve a complex phenomenon which includes the possibility of small single strand nicks undetectable by thermal denaturation, and a loss of small double strand fragments which were detectable only by precise DNA‐DNA free solution reassociation and not by hydroxylapatite chromatography reassociation.
Lack of correlation between overall protein synthesis and the onset of cell elongation in germinating embryos of Haplopappus gracilis
Authors: Galli Maria Grazia , Levi Marisa , Sparvoli Elio
Published: April 2006

10−5M abscisic acid (ABA) completely inhibits germination or (if seeds deprived of integuments are used) embryo elongation in Haplopappus gracilis (Nutt.) Gray. Nevertheless, considerable rates of protein and RNA synthesis were found in embryos grown in abscisic acid, at least during the early hours after sowing. On the contrary, seeds grown in cycloheximide + fusicoccin (a powerful promoter of cell expansion), where protein synthesis is almost completely inhibited, show full protrusion of radicle, thus simulating a “germination” process. These results suggest that some of the most important events involved in seed germination, i.e. protein and RNA synthesis, and cell elongation which leads to radicle protrusion, may not necessarily be linked together and are possibly regulated by different control mechanisms. Moreover, when seeds or embryos are grown in abscisic acid + fusicoccin, protein synthesis is considerable, cell elongation is greater than in water controls at least for 12 h, and germination in its early stages appears to be normal; but DNA synthesis and cell division are not resumed, possibly since some other factor is required. All these findings propose a reevaluation of criteria for defining successful germination.
Inhibition of photosynthetic electron transport by amphotericin B
Authors: Sandmann Gerhard , Böger Peter
Published: April 2006

By assaying partial reactions of the photosynthetic electron transport system using thylakoids from spinach as well as from the algae Bumilleriopsis, Dunaliella, and Anabaena, it was demonstrated that the polyene antibiotic amphotericin B has no specific effect on plastocyanin. Pretreating spinach and algal thylakoids with this antibiotic decreased photosystem‐II as well as photosystem‐I activity regardless of whether the membranes contained plastocyanin or cytochrome c‐553. Different sensitivity of cell‐free electron transport activity against this antibiotic was observed due to the species used. With Dunaliella, the photosystem‐II region was inhibited more strongly than photosystem‐I, while Bumilleriopsis chloroplasts– although not containing plastocyanin – exhibited a stronger inhibition of the photosystem‐I region. Apparently, amphotericin B mainly solubilizes redox compounds that form connecting pools in the photosynthetic electron transport chain.
Influence of indole‐butyric acid, boron, myo‐inositol, vitamin D2 and seedling age on adventitious root development in cuttings of Phaseolus aureus
Authors: Jarvis B. C. , Booth A.
Published: April 2006

Adventitious roots develop in stem cuttings of Phaseolus aureus Roxb. seedlings when treatment with indole‐butyric acid (IBA) is followed by treatment with boron. Root development varies according to the age of seedlings from which cuttings are taken. Increased root number is associated with expansion of the first leaf pair but subsequently declines, whereas root growth increases with increasing seedling age. Removal of leaves furing the first 72 h of treatment impairs root initiation whereas root growth is diminished by removal of leaves at any time during the first 120 h of treatment. IBA stimulates movement of 14C‐IAA out of leaves. Vitamin D2 and myo‐inositol stimulate rooting of intact cuttings provided cuttings are subsequently supplied with boron. Hypocotyls excised from cuttings pretreated with IBA develop roots in response to myo‐inositol in the absence of boron. It is proposed that endogenous auxin, arising in the leaves, and myo‐inositol have roles in root initiation whilst the role of boron is suggested as one of initiating or maintaining transport from the leaves.