bluuebunny/crossref_metadata_2025 huggingface dataset:
The regulation of glycolysis and electron transport in roots
Authors: Day David A. , Lambers Hans , Azcón‐Bieto Joaquín
Published: April 2006

The respiration of roots and isolated root mitochondria was investigated in Phaseolus vulgaris L., Spinacea oleracea L.; Triticum aestivum L., and Zea mays L. Although the respiration of both intact roots and isolated mitochondria displayed resistance to cyanide and sensitivity to SHAM, the percentage resistance and inhibition in roots was not the same as that in the mitochondria, with the exception of wheat. Adding FCCP to roots stimulated oxygen uptake and equalized the effects of SHAM and cyanide on roots and mitochondria. In spinach and maize roots, FCCP stimulated both the cytochrome and alternative pathways, while in bean roots, only the alternative pathway was stimulated. FCCP had little effect on wheat root respiration rates. Potential in vivo rates of oxygen uptake were estimated by expressing rates obtained with isolated mitochondria on a fumarase activity basis, and fumarase activity on a root weight basis. In wheat roots the potential rate was approximately equal to the measured in vivo rate; in the other species the potential rates were substantially greater than measured rates, but approximately equal to uncoupled in vivo rates. Key glycolytic intermediates in roots were measured, and it was found that the phosphofructokinase and pyruvate kinase reactions were displaced far from equilibrium, the degree of displacement being approximately equal in roots with little, and roots with substantial, alternative path engagement. Thus, although glycolysis is controlled, the regulation of this pathway appears to be quite flexible. The results are discussed in terms of possible regulatory mechanisms.
CO2 enrichment, drought stress and growth of Alaska pea plants (Pisum sativum)
Authors: Paez Alejandra , Hellmers Henry , Strain Boyd R.
Published: April 2006

The interaction of CO2 enrichment and drought on water status and growth of pea plants was investigated. Pisum sativum L. (cv. Alaska) plants were grown from seeds in growth chambers using 350 and 675 μl I1 CO2, a photon flux density of 600 μmol M‐2 S‐1, a 16 h photoperiod and a temperature regime of 20/14°C. The drought treatment was started at the beginning of branch initiation and lasted for 9 or 11 days. The water status of the plants was monitored daily by measuring total leaf water potential and stomatal conductance. The total leaf water potential of well‐watered plants was not affected by the CO2 level. Under draughting conditions total leaf water potential decreased, with a slower decrease under the high CO2 regime, due, at least in part, to reduced stomatal conductance. Upon rewatering, total leaf water potential and stomatal conductance recovered within one day. High CO2 counteracted the reduction in height and, to some extent, leaf area that developed in low CO2 unwatered plants. Additional CO2 had no effect on branch number and did not prevent the complete inhibition of branch development that resulted from drought stress. Removing the drought conditions resulted in a rapid recovery of the internal water status and also a rapid recovery of most, but not all, plant growth parameters.
Varietal differences in uptake and utilization of nitrogen and other macro‐elements in seedlings of barley, Hordeum vulgare
Authors: Perby Harald , Jensén Paul
Published: April 2006

Growth and uptake of N, P, S, K, Ca and Mg in barley (Hordeum vulgare L.) were studied in water culture using young plants of 17 cultivars. Large varietal differences were obtained in dry weight production and mineral accumulation. The differences were not the same for plants grown in high‐ and low‐salt media. For plants grown under both conditions there was a good correlation between dry weight production and total N content. Total shoot contents of K and Ca were closely correlated with shoot dry weight. Utilization of P and S in high‐ and low‐salt plants and Mg in low‐salt plants was variable in relation to dry weight production in both types of nutrient conditions. The correlation between dry weight and total content of Mg in high‐salt plants was good. These differences in mineral economy between young barley plants were partly caused by varietal differences in relative growth rate, and in high‐salt seedlings also by differences in seed content of N. The significance of root size, and of uptake, root‐shoot partitioning and use‐efficiency of specific elements differed; all four factors were important for P and S, but had varying impact on K, Mg and Ca. For N, differences in root size and ion accumulation were the most important factors causing varietal variation in mineral nutrition. – In a special experiment seedlings of barley were transferred to N‐free nutrient solution after six days of adequate N supply. There was no significant varietal differences in use‐efficiency ratio of N. Root/shoot partitioning of N was unaffected.
In vitro rooting of the apple rootstock M 26 in adult and juvenile growth phases and acclimatization of the plantlets
Authors: Welander Margareta
Published: April 2006

In order to obtain optimum conditions for in vitro propagation of the apple rootstock M 26 (Malus pumila Mill.) in adult and juvenile growth phases, several rooting experiments were performed. Supraoptimal concentrations of indole‐3‐butyric acid (IBA) added to the rooting media resulted in profuse callus formation. Since extensive callus production is detrimental to the survival of the plantlets, modified culture conditions were established to reduce callus formation. A reduction of the time of exposure to IBA to 5 days and, thereafter, transfer to a hormone‐free medium did not eliminate callus production. Exposure to darkness during the root initiation phase increased rooting. When the rooting medium was based on the Lepoivre formula instead of the Murashige and Skoog formula, callus formation was reduced. Optimum conditions for rooting were obtained at much lower concentration than earlier reported, being 1.25 μM for the juvenile and 0.5 μM for the adult growth phase in the range of IBA concentrations tested. Anatomical studies revealed that root initials are formed after 5 days of IBA‐treatment. Therefore, we transferred shoots directly to non‐sterile conditions after the root‐inducing phase. This resulted in a 90% survival of the plantlets. Subculture on hormone‐free medium can thus be eliminated when the optimum auxin concentration is known.
Correlative changes in sucrose uptake, ATPase activity and membrane fluidity in carnation petals during senescence
Authors: Adam Zach , Borochov Amihud , Mayak Shimon , Halevy Abraham H.
Published: April 2006

Apparent sucrose uptake. ATPase activity and membrane fluidity changes were studied during the development and senescence of carnation flowers (Dianthus caryophyllus L., cv. Cerise Royallette). Typical changes associated with senescence of a cut flower, such as respiration, ethylene production and fresh weight, were measured. Concomitant with a rise in respiration and ethylene production and a decline in fresh weight, a sharp decrease in apparent sucrose uptake was observed. Sucrose uptake was pH dependent (pH optimum, 5.5) and influenced by membrane integrity. Apparently, the activity of ATPase is related to sucrose uptake, because similar changes occurred during flower development. In addition, the activity of ATPase was well correlated with membrane fluidity.

It is suggested that sucrose uptake is controlled by ATPase activity, which in turn is modulated by membrane lipid fluidity. The decline in membrane fluidity associated with senescence leads to a corresponding reduction in ATPase activity and sucrose uptake. Further evidence supporting this view comes from experiments in which senescence was enhanced by 1‐aminocyclopropane‐l‐carboxylic acid. It shortened the time to decline in fresh weight, rise in respiration and ethylene production. In parallel, reduction in membrane fluidity, ATPase activity and sucrose uptake were observed.
Callus of Pinus roxburghii (Chir pine) and its cytology
Authors: Mehra P. N. , Anand Manju
Published: April 2006

Callus was initiated form different vegetative parts of 3 to 5‐week‐old seedlings of Pinus roxburghii Sargent. Best results were obtained on Murashige and Skoog's revised medium supplemented with 4 mg1−1 NAA or 2,4‐D, 1 mg1−1 kinetin and 15% coconut milk. Callus was grown successfully for more than a year without deterioration in its growth. Growth rate studies on the calli form cytoledon explants were undertaken with different concentrations of auxins and cytokinins. Histogenic differentiation of tracheids ocurred in all the calli, with the formation of bordered pits preceding the reticulate thickenings of the tracherary walls. Cells in the 4 to 12‐week‐old calli were predominantly diploid, though a few polyploid and aneuploid cells were also noticed. Chromosome bridges and laggards were observed in a number of cells.
Stomatal and non‐stomatal contribution in the decline in leaf net CO2 uptake during rapid water stress
Authors: Cornic Gabriel , Prioul Jean‐Louis , Louason Geneviève
Published: April 2006

A simple method is proposed for quantitative evaluation of Stomatal and non‐stomatal components of the decline in leaf CO2 uptake during rapid water stress. The changes in leaf conductance were measured during the stress and were used to calculate the photosynthetic rate which would be observed if Stomatal closure were the only cause of the decline in photosynthesis. Photosynthesis‐CO2 response curves, determined just before the stress, were used for this calculation. The difference between the calculated and the actual rate is a measure of the non‐stomatal effect of water stress.

This analysis was tested on Sinapis alba submitted to rapid and severe water stress by excising leaves or roots. Experiments were performed at saturating light conditions under high (61 Pa), normal (34 Pa) or low (11 Pa) ambient CO2 pressure. The non‐stomatal effect on de‐rooted plants reaches a maximum at the beginning of the stress and is dependent on the CO2 pressure: after 45 min its influence is still about 100°, 70° and 8°, respectively, at high, normal and low CO2. In the excised leaf system in which desiccation was more rapid, the non‐stomatal effect accounted for nearly 100° of the assimilation decline whatever the CO2 pressure.
Localization of newly synthesized indoIe‐3‐methylglucosinolate (= glucobrassicin) in vacuoles from horseradish (Armoracia rusticana)
Authors: Helmlinger Jürgen , Rausch Thomas , Hilgenberg Willy
Published: April 2006

The presence and concentration of indole‐3‐methylglucosinolate [= glucobrassicin; 0.49 μmol (g dry weight)‐1] and its 1‐methoxy derivative [0.38 umol (g dry weight)−1] in Armoracia rusticana P. Gärtner, B. Meyer and Scherb, storage roots were measured. The storage tissue contains L‐tryptophan [1.63 μmol (g dry weight)‐1], which is the common precursor amino acid of the indoleglucosinolates. Tissue cylinders convert [14C]‐l‐tryptophan efficiently to the indoleglucosinolates (25%) in vivo. The conversion of [14C]‐l‐tryptophan to indole‐3‐methylgluco‐sinolate shows biphasic kinetics.

A fraction rich in vacuoles was prepared from tissue sections to which [14C]‐l‐tryp‐tophan had been fed and allowed to be metabolized. The predominantly vacuolar location of both L‐tryptophan and the indoleglucosinolates is demonstrated by correlation with the vacuolar marker acid phosphatase.

The significance for the regulation of the indoleglucosinolate biosynthesis and the role of indole‐3‐methylglucosinolate as a potential auxin precursor are discussed.
Regulation of the activity of the alternative oxidase in callus forming discs from potato tubers
Authors: Linus H. W. , van der Plas  , Wagner Marijke J.
Published: April 2006

Callus‐forming discs from potato tubers lose 80% of their starch during one month of incubation on nutrient medium containing either 0, 3 or 6% (w/v) sucrose. The content of soluble sugar in the discs varies from 5 mg (incubated without sucrose) to 22 mg (on 3% sucrose) and 40 mg (on 6% sucrose) per g fresh weight. The activity of the cytochrome pathway (Vcyt) increases during the first week of incubation on all media. Thereafter Vcyt decreases again on 0% sucrose medium, while it remains constant on 3 and 6% sucrose media. Alternative pathway capacity (Valt), absent in freshly sliced tissue, shows a sharp increase during the first days of incubation, independent of the sucrose concentration in the medium. This capacity further increases during prolonged incubation on 3 and 6% sucrose but decreases on 0% sucrose.

The in vivo activity of the alternative pathway (the participation in uninhibited respiration, ϱValt) varies with the sucrose concentration and with the culture time. In tissue incubated for 2‐3 weeks on 6% sucrose as much as 45% of the electrons are transfered to oxygen via the alternative pathway. In this tissue the factor Q (the part of the alternative pathway capacity that is operative) is about 0.8, while in tissue incubated on 0 and 3% sucrose media p generally does not exceed 0.5.

When chloramphenicol, an inhibitor of mitochondrial protein synthesis, is added to the medium together with 3% sucrose, the increase in Vyet does not occur, while the induction of Valt during the first week of incubation is the same as without chloramphenicol. A greater part of the alternative pathway capacity becomes operative in this tissue, leading to values of Q of almost 1 after prolonged incubation. Apparently, incubation on high sugar medium leads to extra participation in respiration of the energetically inefficient alternative oxidase pathway Excess sugar leads to wasteful respiration suggesting that the alternative oxidase functions as an ‘energy overflow’.
Induction of urease by urea analogues in Evernia prunastri thallus
Authors: Vicente C. , Nieto J. M. , Legaz María Estrella
Published: April 2006

Urease activity in Evernia prunastri (L.) Ach. thallus is induced by incubation of lichen samples on 20 mM N,N‐dimethylformamide and 20 mM N‐formylurea or 40 mM thiourea although, in these two last cases, activity subsequently decreases again. The induction of enzyme activity is repressed by including 40 μM cycloheximide in the medium. Filtration through Sepharose 6B of cell‐free extracts from thalli incubated on 20 mM N,N‐dimethylformamide shows a main peak of urease activity which has a molecular weight of about 560000 dalton. However, those extracts from thalli floated on 20 mM N‐formylurea and 40 mM thiourea show several peaks of similar enzyme activity, which have molecular weights of about 1 100000, 670000, 260000 and 140000 dalton and 1 100000, 670000 and 140000 dalton respectively.

A time‐course of urease activity could be related to the accumulation of lichen phenols in the thallus for samples incubated on N,N‐dimethylformamide and thiourea.
Inhibition of photosynthetic activity by UV‐B radiation in radish seedlings
Authors: Tevini M. , Iwanzik W.
Published: April 2006

Inhibition of primary photosynthetic reactions by UV‐B radiation (280 nm‐320 nm) was demonstrated in radish leaves (Raphanus sativus cv. Saxa Treib). Detached radish cotyledons from 10‐day‐old seedlings were irradiated with continuous white light and increasing UV‐B irradiances using cut‐off filters with increasing transmission for shorter wavelengths (WG 360, WG 345, WG 320, WG 305, WG 295, WG 280). Photosynthetic activity measured in terms of chlorophyll fluorescence induction (Kautsky effect) after 2, 4, 6, 8 and 24 h irradiation decreased in a wavelength dependent way with increasing UV‐B irradiance and irradiation time.

Radish seedlings grown for 10 days from the time of germination under the same UV‐B irradiation conditions exhibited similar reductions of the variable fluorescence as detached cotyledons irradiated for short time periods. They additionally had lower initial fluorescence at high UV‐B radiation levels, although the chlorophyll content per leaf area increased. In contrast to short term experiments, the plastoquinone and flavonoid content increased with increasing UV‐B irradiance when based on leaf area.
The effects of ultraviolet‐B radiation on plant competition in terrestrial ecosystems
Authors: Gold Warren G. , Caldwell Martyn M.
Published: April 2006

Evidence regarding the interaction of ultraviolet‐B (UV‐B, 280‐320 nm) radiation and plant competition in terrestrial ecosystems is examined. The competitive interactions of some species pairs were affected even by ambient solar UV‐B radiation (as exists without ozone depletion), when compared to control pairs grown without UV‐B. Also, the total shoot biomass of these species pairs was depressed under ambient UV‐B. Relatively large increases in UV‐B radiation (approximating a 40% ozone layer reduction when weighted with the generalized plant action spectrum) altered the competitive interactions of some species pairs grown in pots under field conditions, but did not affect the total shoot biomass production of those pairs. Recent field experiments have examined the competitive interactions of wheat (Triticum aestivum L. cv. Bannock) and wild oat (Avena fatua L.) under a simulated increased UV‐B regime resulting from a 16% ozone layer reduction when weighted with the generalized plant action spectrum. This increase in UV‐B altered the competitive interactions of these two species without affecting the total shoot biomass production of the species pair. The manner in which increased UV‐B affected the relative competitive abilities of the two species was highly dependent upon the environmental conditions during the early life stages of the plants. The implications of these results for both agricultural and natural plant communities are discussed.
Changes in ATP sulfurylase and adenosine 5′‐phosphosulfate sulfotransferase activity during autumnal senescence of beech leaves
Authors: Brunold Christian
Published: April 2006

The decrease in extractable activity of ribuloscbisphosphate carboxylase (EC 4.1.1.39), ATP sulfurylase (EC 2.7.7.4) and adenosine 5′‐phosphosulfate sulfotransferase and the content in chlorophyll and protein was compared in leaves of cloned beech trees (Fagus sylvatica L.) during autumnal senescence. Leaves excised at the same time but containing different amounts of chlorophyll gave extracts with correspondingly varying amounts of ribulosebisphosphate carboxylase activity. Leaves which had almost completely lost this enzyme activity contained still appreciable ATP sulfurylase and adenosine 5′‐phosphosulfate sulfotransferase activity and soluble protein. For all components determined, there was a period lasting until mid or end of October during which there was no or only a small decrease. They were then all lost rapidly from the leaves. The specific activity of ribulosebisphosphate carboxylase decreased during this phase of rapid loss, whereas it remained essentially constant for ATP sulfurylase and adenosine 5′‐phosphosulfate sulfotransferase. During this period, the mean half life of ribulosebisphosphate carboxylase was shorter than the one of ATP sulfurylase and of adenosine 5′‐phosphosulfate sulfotransferase. These experiments clearly show that ribulosebisphosphate carboxylase was preferentially lost from beech leaves during autumnal senescence as compared to ATP sulfurylase and adenosine 5′‐phosphosulfate sulfotransferase.
The effects of time of seed production on the germination response of Spergularia marina
Authors: Okusanya Olubukanla T. , Ungar Irwin A.
Published: April 2006

Germination studies were carried out with seeds of Spergularia marina L. Griseb produced over an interval of six months (June‐November). The response of the seeds to light and dark, various constant and alternating temperature regimes, and salinity were determined. In addition, the effects of soil moisture status at the time of seed production on the subsequent germination response of seeds were also determined. Light was an absolute requirement for germination. While a constant temperature regime did not generally favour germination of seed of any month, alternating temperature greatly enhanced germination with an optimum at 5/15°C in all seeds. When imbibed in solutions of different salinities, seeds collected in July and October behaved like true halophyte seeds whereas those collected in June. August, September and November behaved like glycophyte seeds.

High concentration of gibberellic acid (3 000 μM) stimulated dark germination in the June and November seed lots, but in light, low GA3 concentration (300 μM) stimulated germination most. The addition of kinetin (30 μM) plus gibberellic acid enhanced germination in the dark in contrast to GA3 alone; kinetin alone stimulated a very low percentage germination.

The moisture status of the soil at the time seeds were produced did not affect the germination response of an early seed crop (July) but affected that of the later seeds (August).

Judging from the different germination responses, it appears that the seeds belong to at least two physiological groups, one which appears to need either a dark‐wet or cold‐wet pretreatmem for high germination to occur; and the other group which does not need pretreatmem. The ecological significance of these varied responses is discussed in relation to the survival of the species in its habitat.
Regulation of leaf senescence, grain‐filling and yield of rice by kinetin and abscisic acid
Authors: Ray S. , Mondal W. A. , Choudhuri M. A.
Published: April 2006

Senescence of rice (Oryza sativa L. cv. Jaya) leaves was regulated with kinetin and abscisic acid (ABA) sprays at the reproductive stage. The effect of such sprays on grain‐filling and yield was analyzed. Spraying 100‐day‐old plants with kinetin solution (100 μg ml‐1) significantly delayed senescence as indicated by higher total chlorophyll and protein levels in the three uppermost leaves compared with the controls. In contrast, spraying with ABA (15 μg ml‐1) significantly promoted foliar senescence. The number of spikelets per panicle, number of panicles, percentage filled grains, panicle weight and grain yield per plant and the mobilization and harvest indices were significantly increased by kinetin treatment, while ABA decreased most of them. The possibility of increased grain‐filling and thus, yield due to delayed foliar senescence by kinetin treatment and decreased grain‐filling due to hastening of senescence by ABA is discussed.
Alternative pathway respiration in vivo of potato tuber callus grown at various temperatures
Authors: Hemrika‐Wagner Anneke M. , Verschoor Ernst J. , van der Plas Linus H. W.
Published: April 2006

During incubation of potato tuber discs (Solanum tuberosum L. cv. Bintje) on a callus‐inducing medium at 28°C, a high capacity of in vivo alternative pathway respiration develops (75% of uninhibited respiration is azide‐resistant). When callus induction takes place at 8°C, only 45% of respiration is resistant to azide. In the lag phase of growth the activity of alternative pathway is low. during the exponential growth phase the activity reaches its maximal rate. This in vivo activity is of the same size at both culture temperatures. As a consequence a greater part of alternative pathway capacity is operating in uninhibited respiration during growth at low temperatures.
Control of galactosyl‐sugar metabolism in relation to rate of germination
Authors: Main E. L. , Pharr D. M. , Huber S. C. , Moreland D. E.
Published: April 2006

The storage sugars stachyose and raffinose (galactosyl derivatives of sucrose) are metabolized early during germination of soybean [Glycine max (L.) Merr.] seeds. The activities of four enzymes involved in the catabolism of these sugars were monitored in soybean cotyledons and embryonic axes during a 7‐day germination period. An increase in enzyme activities correlated with a decline in galactosyl sugars. In embryonic axes, uridine diphosphate glucose (UDPglc)‐hexose‐l‐P uridyltransferase (EC 2.7.7.12), an enzyme characteristic of the Leloir pathway, predominated over galactose‐1‐phosphate uridyltransferase (EC 2.7.7.10), an enzyme characteristic of the pyrophosphorylase pathway; whereas in cotyledons, the situation was reversed. There were differences between two cultivars. Ransom and Amsoy, in the levels of UDPglc‐4‐epimerase (EC 5.1.3.2); but not in glucose‐1‐phosphate uridyltransferase (EC 2 7.7.9). An accelerated aging treatment had a significant effect on the development of embryonic axes, as measured by dry weight. In vitro aging of seeds reduced the rate of growth and resulted in higher levels of galactose‐containing sugars and significantly lower levels of UDPglc‐hexose‐l‐P uridyltransferase. Thus, reduced development may be related to inability to mobilize or utilize stored carbon reserves. However, it has not been proved that the reduced enzyme activity is responsible for the effects of accelerated aging on growth and sugar metabolism.
2,4‐Dichlorophenoxyacetic acid inhibition of potassium transport in barley seedlings
Authors: François Guido , Dewit Maria , Neirinckx Louis
Published: April 2006

Growth, potassium uptake and translocation as well as transpiration rates were measured in intact low‐salt barley seedlings (Hordeum vulgare L. cv. Union) in the presence of different 2,4‐D concentrations at pH 6.5. Growth was only affected at 10‐3M.

Above 10‐7M 2,4‐D both uptake by the roots and transport to the shoots were inhibited. The inhibition at 10‐5M remained constant for at least 24 h. Furthermore inhibition of uptake was measurable within 1 h. Excised roots and roots of intact plants showed the same uptake pattern.

It is suggested that the observed effects were caused by 2,4‐D‐induced changes in uptake and translocation systems in the roots. Pre‐treatment with 10‐5M 2,4‐D had no effect upon subsequent potassium uptake. Transpiration was reduced within 1 h in 10‐4 or 10‐3M 2,4‐D, probably due to changes in water transport or root permeability.
Anatomical aspects of hormonal regulation of abscission in citrus – The shoot‐peduncle abscission zone in the non‐abscising stage
Authors: Huberman Moshe , Goren R. , Zamski E.
Published: April 2006

Although mature citrus fruits [Citrus sinensis (L.) Osbeck cv. Shamouti] did not abscise at the peduncle‐shoot abscission zone (AZ–A) when incubated in ethylene environment, abscission processes did occur in a limited number of cell layers situated in the inner bark, the starch sheath region, and in the pith of AZ–A. These processes were regulated by 2,4‐D and ethylene treatments. Cells responding to the “separation processes”, particularly in the ethylene treatment, underwent either (a) cell wall swelling, dissolving and breakdown, or (b) growth and expansion in a radial plane. Further away from the dissolving area, the response of some cells of the mid and outer bark took the form of divisions or growth in a circumferential plane, while other cells remained unchanged. Non‐responding tissues of the outer bark formed a “sleeve” of undissolved cells, and the vascular cylinder produced no abscission in AZ–A. It is concluded that the partial cell wall dissolution in AZ–A explains the increased activity of cellulase and polygalacturonase in the non‐abscising AZ–A of the mature fruit (Greenberg et al. 1975. Physiol. Plant. 37: 1–7).
Changes in nitrogen levels and free amino acids in rooting cuttings of mulberry (Moms alba)
Authors: Suzuki Takeo , Kohno Kiyoshi
Published: April 2006

Total and protein nitrogen in bark and wood of parent stems of mulberry (Morns alba L. cv. Ichinose) decreased readily and to the same extent during leafing‐out of the buds, but the decrease in wood was less marked than in bark. Simultaneously, soluble nitrogen in both bark and wood also declined but the depletion was less marked than that of total and protein nitrogen. During the same period total nitrogen in the new shoots and adventitious roots increased drastically; however, the increase in total nitrogen in the growing parts during rooting was almost the same as the decrease in total nitrogen in the parent stems. Proline, the prevalent amino acid in wood and bark of the parent stems, decreased drastically during rooting, whereas during the same period asparagine in the developing buds, callus and adventitious roots increased markedly and became the predominant amino acid. The amount of arginine was relatively high in bark of the parent stems but Low in wood and the buds. The level of arginine in bark decreased considerably during the experiments (as did that of proline). The results suggest that the nitrogen required by the growing parts (sinks) in the rooting cuttings comes mainly from protein breakdown in bark of the parent stems (source), although stored protein in wood (source) and soluble nitrogen in bark and wood (sources) also play a part in storage of nitrogen. Asparagine is suggested to be the main nitrogen transport compound in the new growth of the tree and the initiating roots of cuttings.
Soybean root and nodule nitrate reductase
Authors: Hunter William J.
Published: April 2006

Nitrate reductase (NR) activity was followed in root and nodule from Glycine max (L.) Merr. (Cv. Tracy) inoculated with Rhizobium japonicum. Initially, a plus NO3‐ in vivo assay was used. When chlorate‐resistant mutants were used as inoculum, nodule NR activity was reduced by about 90%. indicating that the bacteroid accounts for much of the normal nodule's NR. With plants 3 to 15 weeks of age nodule NR activity (g fresh weight)‐1 was highest in young plants and root activity highest in old plants. Root and nodule total NR activity increased with plant age and were often not greatly different. Root NR activity correlated with plant NO3‐ supply and increased from 0.8 to 11.4 μmol plant‐1 h‐1 as NO3‐ was increased from 0 to 3 mM. In contrast, nodule NR activity was high in plants grown without NO3‐ and did not appear to increase as nitrate supply to the plant was increased. Nodule activity was 6 to 14 μmol NO2‐ plant‐1 h‐1. Use of a minus NO3‐ in vivo assay had little affect on root NR activity, but greatly reduced nodule activity. Root tissue was found to have 5 to 38 times more NO3‐ than nodule tissue. It is concluded that low nitrate levels within the nodule limit NR activity and that it is improbable that the nodule is a major site of plant nitrate reduction.
Ethylene, indoleacetic acid and apical dominance in peas: A reappraisal
Authors: Blake Terence J. , Reid David M. , Rood Stewart B.
Published: April 2006

Decapitation of peas (Pisum sativum L. cv. Greenfeast) promoted sprouting of the lower buds with the most active growth in the first week occurring in the bud at the lowest fully expanded leaf node. Addition of 3‐indolyl acetic acid (IAA; a 0.03 M solution, applied al 10 and 25 μg/plant) inhibited bud outgrowth whether added to the cut stump or injected above or below the lowest leaf node. Ethylene evolution by the nodal region decreased following decapitation, but increased greatly if IAA was added to the cut stump. Ethylene gas (3, 15 and 1 500 ul/l) or the precursor ACC (l‐aminocyclopropane‐I‐carboxylic acid) reduced bud outgrowth while factors which scrub ethylene (mercuric perchlorate). inhibit ethylene synthesis (canaline), or prevent its action (silver nitrate), enhanced bud growth on decapitated plants, It was concluded that auxin‐induced inhibition of bud growth through an increase in ethylene synthesis is a more logical hypothesis than the direct inhibition by auxin per se since a) acropetal movement of the inhibitory principle occurred whereas [14C] IAA movement in stems was basipetal, b) a decline in the levels of ethylene evolution was correlated with bud outgrowth in decapitated plants and c) exogenous application of chemical agents which increase or decrease ethylene level or response lead to correlative decreases or increases in bud outgrowth, respectively.
Interaction between Pfr and growth substances in the germination of light‐requiring Kalanchoë seeds
Authors: Dedonder A. , Rethy R. , Frederieq H. , De Greef J. A.
Published: April 2006

Seeds of Kalanchoë blossfeldiana Poelln. cv. Feucrblüte, incubated on gibberellic acid, become very light‐sensitive through a synergism between the far‐red absorbing form of phytochrome and the growth substance, which results in high physiological activity of short far‐red (FR) exposures. On 2 × 10‐3M gibberellic acid (GA3), one saturating FR pulse is somewhat more effective than one saturating red light (R) irradiation. Fluence‐response curves for R and FR confirm this observation. At lower GA3 concentrations, this difference disappears and the effects of one saturating R and FR pulse decrease in an identical way with the GA3 concentration. When two saturating irradiations, separated by 24 h are given, the effect of FR falls off faster than that of R at low GA3 concentrations. Consequently, the second irradiation must have a different impact in comparison with the first one. Of the other growth substances tested, only a mixture of gibberellins A4 and A7 had an analogous, still more pronounced effect than GA3. Abscisic acid (ABA) inhibits the phytochrome‐mediated germination of Kalanchoë, both in the absence and presence of GA3. An antagonism between ABA and GA3 was demonstrated.
Photochromic pigments in akinetes and pigment characteristics of akinetes in comparison with vegetative cells of Anabaena variabilis
Authors: Björn Gunvor Solveig , Braune Wolfram , Björn Lars Olof
Published: April 2006

Since akinete germination is triggered by light and the action spectrum for this process has features in common with the spectra of the two photochromic pigments, phycochromes b and d, a search was made for the presence of these phycochromes in akinetes of the blue‐green alga. Anabaena variabilis Kützing. Allophycocyanin‐B was also looked for, since the action spectrum for akinete germination points to a possible participation of this pigment too. Isoelectric focusing was used for purification of the pigments. The different fractions were investigated for phycochromes b and d by measuring the absorbance difference spectra: for phycochrome b. 500 nm irradiated minus 570 nm irradiated, and for phycochrome d, 650 nm irradiated minus 610 nm irradiated. For determination of allophycocyanin‐B. fourth derivative analysis of absorption spectra was made for some of the fractions from the isoelectric focusing column. Phycochrome b was also assayed for by measuring in vivo absorption difference spectra. The assays were positive for all three pigments.

The complete photosynthetic pigment systems were also studied by in vivo fluorescence measurements on both akinetes and vegetative cells of Anabaena variabilis. Fluorescence emission and excitation spectra at selected emission wavelengths were measured at room temperature and liquid nitrogen temperature. The energy transfer from phycoerythrocyanin to phycocyanin is very efficient under all conditions, as is the energy transfer from phycocyanin to allophycocyanin at room temperature. At low temperature, however, phycocyanin is partly decoupled from allophycocyanin, particularly in the akinetes; the energy transfer from allophycocyanin to chlorophyll a is less efficient at low temperature in both types of cells, but especially in akinetes. Delayed light emission was measured for both types of cells and found to be very weak in akinetes compared to vegetative cells. From this study it would seem that akinetes lack an active photosystem II, although the 691 nm peak in the 570 nm excited low temperature fluorescence emission spectrum proves the presence of photosystem II chlorophyll, and also its energetic connection to the phycobilisomes.
Cinétique de la rhizogenèse adaptative à la sécheresse. Relation avec I'évolution des paramètres hydriques et morphologiques chez leSinapis alba, à deux niveaux d'énergie lumineuse
Authors: Sabatier G. , Vartanian N.
Published: April 2006

Kinetics of adaptive drought rhizogenesis, as related to growth and water deficits inSinapis alba, attwo irradiance levels.

The rhizogenic activity inSinapis albaL., subjected to progressively increasing water deficit during growth, shows a sigmoidal pattern of kinetics with three phases: initiation or latent phase, rapid exponential increase, and stationary phase. This pattern remains unchanged if the level of irradiance during growth is reduced. The same number of short tuberized roots is obtained as under high irradiance, although initiation of rhizogenesis appears to be delayed by a few days. However, this delay is not observed if the rhizogenesis is analyzed as a function of the water potential of aerial organs or as a function of the soil water deficit. Since the rate of dehydration depends upon the evaporative demand, which is modulated by high or low irradiance, drought rhizogenesis seems to be directly related to water deficits in the soil‐plant system. The onset of drought rhizogenesis, starting at the end of the growth period of the aerial organs, appears concomitant with the transpiration decline which is induced by water stress at both irradiance levels.
Mechanical properties and polysaccharide nature of the cell walls of maize root
Authors: Masuda Yoshio , Pilet Paul‐Emile
Published: April 2006

Changes in mechanical properties and chemical nature of the cell walls of the different zones along elongating maize (Zea mays L. cv. LG 11) roots were analyzed and the following results were obtained. (1) The apical region 2 to 5 mm from the tip of 15 mm long roots showed rapid elongation whereas the region 8–10 mm from the tip showed very little growth. (2) The minimum stress‐relaxation time (To) and the mean stress‐relaxation rate (R) of the cell wall were small whereas the maximum stress‐relaxation time (Tm) was large in the region where cell elongation was optimum. The To and R increased and the Tm decreased gradually towards the base of the root. (3) The amounts of non‐cellulosic polysaccharides of the cell wall were highest in the region 1.5–2.5 mm from the tip, decreasing until 5 mm from the tip, and then increasing towards the base. However, the proportion of this fraction in the total cell wall polysaccharides was highest in the extreme tip (cap and meristem, 0–1 mm) and decreased towards the base. (4) Major neutral sugars constituting the non‐cellulosic polysaccharides of the cell wall were xylose, arabinose, galactose and glucose, with minor amounts of rhamnosc. mannose and fucose. The 1–15 mm region was on the whole rich in glucose and xylose and contained arabinose to a lesser extent. However, the chemical nature in the apical region, (0–2 mm, was rather special, being rich in galactose and fucose. (5) The cell wall of maize roots contained, as a whole, only little pectic substances but was high in hemicellulose 1 (rich in xylose, arabinose and glucose) and hemicellulose 2 (rich in glucose and xylose). (6) It appeared that in the elongating region (apical 2 to 5 mm) the cell elongation rate (CET) showed a rather good correlation with the parameters of mechanical properties (To, Tm and R) and with neutral sugar compositions in the non‐cellulosic polysaccharides.
Comparison of the effects of auxin and fusicoccin on phosphate absorption by aged potato tuber discs
Authors: Poder Danielle , Hounnant Annick , Penot Michel
Published: April 2006

Auxin (IAA, 5 × 10−5M) partially prevents the increase in the rate of phosphate uptake during ageing of potato tuber discs (Solatium tuberosum L. cv. Bintje), whereas fusicoccin (FC, 10−5 M) stimulates it. After the development of enhanced phosphate transport capacity, the response to fusicoccin is greater than with fresh discs. Complementary experiments on K+ (86Rb) absorption show that FC also slightly enhances the rate of K+ uptake, while IAA has no much effect. It is suggested that IAA acts specifically on the development of a mechanism which occurs during the ageing period, while FC action may be more directly linked to the system of phosphate transport itself.
Effects of propylene and oxygen on the ethylene‐producing system of apples
Authors: Butler G. , Bangerth F.
Published: April 2006

Hypobaric conditions and treatments with ethylene and the ethylene analogue propylene were used to investigate effects of oxygen and elhylene on 1‐aminocyclopropane‐1‐carboxylic acid (ACC) content, ACC synthase activity and ethylene production of apples (Malus sylveslris Mill. cv. Golden Delicious). Prcclimacteric apples were stored in air at 6.6 kPa (reduced pressure); 6.6 kPa ventilated with pure O2; 6.6 kPa ventilated with 2600 μl 1−1 C2H4; and in air at 101.3 kPa (atmospheric pressure) for 4 months at 4°C. No ACC synthase activity was detectable in apples stored at 6.6 kPa, whereas ACC synthase activity was induced in apples stored at 6.6 kPa and ventilated with either O2 or C2H4. In a further experiment, preclimacteric apples were stored for 14 days either in air at 20 kPa or at 20 kPa ventilated with pure O2. Both treatments were supplied with 58 500 μl 1−1 propylene from day 0 to day 9 or from day 9 to day 12. Ethylene production of apples treated with propylene from day 0 to day 9 increased earlier than ethylene production of untreated apples. Propylene treatment from day 9 to day 12 did not stimulate ethylene production. Ethylene and propylene induced and stimulated extractable ACC synthase activity and ACC formation of apples. Oxygen enhanced this effect. The results also suggest inhibition of in vivo ACC synthase activity by propylene.
Dimethylsulfoxide action on dark‐ and light‐induced leaflet movements and its necrotic effects on excised leaves of Cassia fasciculata
Authors: Roblin Gabriel , Fleurat‐Lessard Pierrette
Published: April 2006

Dimethylsulfoxide (DMSO) acts on dark‐ and light‐induced movements exhibited by leaflets of isolated leaves of Cassia fasciculate Michx. The closing movement (scotonasty), induced when the leaves are placed in darkness during the normal period of daylight, was inhibited, whereas the opening movement (photonasty), when the leaves arc transferred to light during the normal period of darkness, was promoted. The concentration for significant effects of DMSO was 1% (v/v) when applied over a 3‐h period. After five days, a necrosis of the leaflets was observed for DMSO concentrations as small as 0.1%, applied over a 6‐h period. Complete abscission took place if 3% DMSO was applied for more than 30 min.
K/Na selectivity at the plasmalemma of cortical root cells and preferential release of sodium to the xylem vessels in roots of Atriplex hortensis
Authors: Stelter Wilfried , Jesehke Wolf Dieter
Published: April 2006

Using excised roots of Atriplex hortensis L., cv. Gelbe Gartenmelde, the uptake, accumulation and xylem transport of K+ and Na+ have been measured. Influx as well as xylem transport proved to discriminate little between K+ and Na+, when considered in relation to the external solution. Both K+ and Na+ inhibited the uptake and xylem transport of each other to about the same degree. Measurements of intracel‐lular Na+ fluxes by means of compartment analysis indicated that the low degree of K/Na discrimination during uptake was due to low influx selectivity. Moreover, K+/Na+ exchange at the plasmalemma was not very efficient in Atriplex roots. In order to establish the basis of the low K/Na discrimination in xylem transport, the rates of K+ and Na+ transport were related to the cytoplasmic K+ and Na+ concentrations to yield the selectivity ratio of transport, S(transport) = (ϕcx(K) × [Na+]c)/(ϕcx(Na) × [K+]c). Under all conditions this ratio was far below one indicating that Na+ was favoured during xylem release in excised roots of Atriplex at low external concentrations. The implications of this discrimination in favour of Na+ are discussed with respect to salt tolerance of A. hortensis.
Role of cell wall in freezing tolerance of cultured potato cells and their protoplasts
Authors: Tao Dali , Li P. H. , Carter J. V.
Published: April 2006

Cultured potato (Solanum tuberosum L., cv. Red Pontiac) cells suspended in PEG 1000 solutions of 0.6 and O.S osmol exhibited significantly different freezing tolerance from the same cells when suspended in PEG 6000 solutions of the same osmolalities. Cells suspended in PEG 6000 showed cytorhysis instead of plasmolysis. Cells in 0.2 and 0.4 osmol PEG 1000 had LT50(1 of −2.5°C, but the LT50 decreased to −7.50C as the osmolality increased to 0.8 osmol. In PEG 6000 the LT50 remained at −2.50C for all osmolalities used, up to and including 0.8 osmol.

Released protoplasts suspended in 0.5 M sucrose had LT50 of −21.5°C, compared to −12°C for whole cells suspended in the same medium. These results lend credence to an involvement of the cell wall in freezing injury of cultured potato cells, and are interpreted in terms of the generation of a mechanical stress between cell wall and plasma membrane during the freeze‐thaw cycle.
Effect of the crown on uptake and transport in embryonic shoots of Picea abies
Authors: Jansson Eva , Jensén Paul , Bornman Chris H.
Published: April 2006

Embryonic shoots of Picea abies (L.) Karst, isolated from 10‐year‐old trees, were excised either with or without the crown. Various short‐term uptake experiments (3, 6 and 24 h) and one long‐term uptake experiment (4 weeks) were performed with these shoots to obtain information about the physiological role of the crown as translocation barrier for different substances. Transport through the embryonic shoots was followed in both acropetal and basipetal directions using radiolabelled substances supplied in an agarified Schenk and Hildebrandt medium. The medium was labelled with [14C]‐IAA and/or [32P]‐phosphate, or with [35S]‐sulphate and 86Rb (as a tracer for K+). The experiments were conducted in light at 20°C, with the exception of one of the short‐term experiments, which was carried out at 5°C to evaluate the connection between transport and metabolism. The main observation is that the crown in its collenchymatous stage of development acts as a selective barrier both acropetally and basipetally for transport of substances such as [14C]‐IAA and [32P]‐phosphate or their metabolized forms. This could explain why the embryonic shoot when cultured plus or minus its crown shows different growth and developmental patterns in vitro.
The effect of brassinosteroid on auxin‐induced ethylene production by etiolated mung bean segments
Authors: Arteca Richard N. , Tsai De‐Sheng , Schlagnhaufer Carl , Mandava N. Bhushan
Published: April 2006

Brassinosteroid, an analogue of brassinolide, (BR) (2α, 3α, 22β, 23β‐tetrahydroxy‐24β‐methyl‐B‐homo‐7‐oxa‐5α‐cholestan‐6‐one), was tested in conjunction with indole‐3‐acetic acid (IAA), naphthaleneacetic acid (NAA), 2,4‐dichlorophenoxyacetic acid (2,4‐D), indole‐3‐butyric acid (IBA), indole‐3‐propionic acid (IPA), indole‐3‐pyruvic acid (IPyA), indole‐3‐aldehyde (IAld), indole‐3‐carbinol (ICB) or tryptophan (TRP) for its effects on ethylene production by etiolated mung bean (Vigna radiata (L.) Rwilcz cv. Berken) hypocotyl segements. The enhancement of ethylene production due to BR was greatest in conjunction with 1 μM IBA, 2,4‐D, IAA, or NAA (these increases were 2580, 2070, 890, and 300%, respectively). When increasing concentrations of IBA, 2,4‐D, IAA, or NAA were used, there was a decrease in the percentage stimulation by BR. Both IPyA and IPA had different optimal concentrations than the other auxins tested. Their BR‐enhanced maximum percentage stimulations (1430 and 1580%) were greatest with 5 μM IPya and 10 μM IPA, respectively. There was a marked reduction in the percentage stimulation by BR with either 100 μM IPyA or IPA. The inactive indoles (IAld, ICB, or TRP) did not synergize with BR at any of the concentrations tested. Four hours following treatment those segments in contact with 1 μM BR with or without the addition of 10 μM IAA began to show a stimulation in ethylene production above the control and this stimulation became greater over the following 20 h. It was necessary for BR to be in continual contact with the tissue to have a stimulatory effect on auxin‐induced ethylene production. When segments excised from greater distances below the hypocotyl hook, were treated with either IAA alone or in combination with BR, there was a decrease in ethylene production with increasing distance. There was no effect of hypocotyl length on BR stimulation of auxin‐induced ethylene production; however, there was a definite decrease in ethylene production when IAA was applied alone.