bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of plant hormones and carbohydrates in the growth and survival of coppiced Eucalyptus seedlings
Authors: Taylor J. S. , Blake T. J. , Pharis R. P.
Published: April 2006

Depending on the species, coppicing (decapitation) may promote vigorous growth (Eucalyptus camaldulensis Dehn), or cause rapid senescence and death (Eucalyptus obliqua L'Herit). In seedlings of the latter species, the presence of a small upwardly directed shoot on the decapitated stump prevents or delays decline. Coppiced seedlings of E. camaldulensis and E. obliqua, with and without a remaining shoot, were analyzed for starch and soluble sugars (with the anthrone method), gibberellin‐like substances (GAs) and cytokinin‐like substances (by bioassay), and ethylene (by gas‐liquid chromatography) before and after decapitation.

Levels of soluble sugars declined similarly in both varieties of eucalypts, and starch reserves appeared adequate for sprouting, and did not diminish following decapitation of the susceptible species.

Decapitation did not markedly alter the relatively high amounts of GAs in roots and shoots of E. obliqua, the susceptible species, although increased levels of Gas were observed in the stumps of seedlings left with 1 shoot after decapitation. The overall levels of GaS were relatively low in the roots and stems of the resistant E. camaldulensis, but higher in the shoots. Marked qualitative changes in GAs with decapitation were apparent in the shoots of E. camaldulensis. A single major GA peak occurred prior to decapitation but afer decapitation several additional peaks of GA‐like activity appeared.

Cytokinin‐like activity was initially low in all tissues, but increased dramatically in stump and shoot tissue following decapitation. Increases ranged from approximately 5‐fold (stump tissue of either species, minus‐shoot treatment) to approximately 40‐fold (shoot tissue of the resistant E. camaldulensis seedlings left with 1 shoot). In both E. camaldulensis and E. obliqua ethylene production increased to a peak 7 days after decapitation provided a shoot had been retained. This ethylene peak precedes a marked upturning of the retained shoot, and was not present in the stumps of totally decapitated seedlings. For totally decapitated seedlings ethylene evolution in E. obliqua (the susceptible species), but not E. camaldulensis (the resistant species), had ceased by 15 days.
Polyamine biosynthesis and titer during various developmental stages of Phaseolus vulgaris
Authors: Palavan Narçin , Galston Arthur W.
Published: April 2006

The activities of arginine decarboxylase (ADC; EC 4.1.1.19) and ornithine decarboxylase (ODC; EC 4.1.1.17) as well as polyamine content were examined in Phaseolus vulgaris L. cv. Taylor's Horticultural before and during anthesis, during fruit development and throughout vegetative growth. The specific activities of polyamine biosynthetic enzymes were highest in all rapidly growing tissues, e.g., root apices, hypocotyls, young internodes, young leaves, flower buds, young pods and pericarps. They were lowest in mature, non‐growing tissues. Similarly, the content of the major polyamines (putrescine, spermidine, spermine) is highest in rapidly growing tissues, and lowest in mature tissue. These correlations reinforce the growing connection between polyamines and rates of cell division and metabolic activity during both vegetative and reproductive development.
Development of regulation mechanisms for SO42‐ influx in spring wheat roots
Authors: Jensén Paul , König Tomas
Published: April 2006

The development of SO42‐ influx in roots and sulfur transport to shoots was followed in 35S‐tracer experiments for sulfur‐deficient spring wheat (Triticum aestivum L. cv. Svenno) seedlings pretreated for various time periods (0–24 h) in nutrient solutions with SO42‐. Effects of the metabolic inhibitor 2,4‐dinitrophenol (DNP) and the protein synthesis inhibitor cycloheximide (CH) on SO42‐ influx were also evaluated. The SO42‐ influx appears feedback‐regulated by the internal sulfur level of the roots. Regulation may be achieved solely by a rapidly changed SO42‐ carrier activity through an allosteric effect by the intracellular SO42‐ concentration of the roots, followed first by induction of carrier synthesis and then by repression of carrier synthesis after transfer of the roots from SO42‐‐deficient nutrient solutions to solutions with SO42‐. A Hill plot of the partly sigmoidal relationship between SO42‐ influx and intracellular sulfur concentration in the roots gave a Hill coefficient of ‐4.2, indicating negative cooperativity between a minimum number of four interacting allosteric binding sites for sulfur on each carrier entity. DNP‐experiments showed that SO42‐ influx was mainly metabolic, especially after short pretreatment in SO42‐ at an external SO42‐ concentration of 0.1 mM. Pretreatment with CH rapidly prevented new SO42‐ carriers from being formed. Long CH pretreatment (24 h) and different SO42‐ pretreatments reduced SO42‐ influx below the non‐metabolic level obtained by uptake experiments with DNP, indicating the existence of SO42‐ carriers mediating passive SO42‐ transport across the plasmalemma of the root cells. SO42‐ influx was further decreased for the CH pretreated (24 h) plants by the presence of both CH and DNP in the experimental nutrient solution. This probably indicates the diffusive part of the non‐metabolic SO42‐ influx in the present experiments. Finally, it is suggested that there is a feedback signal between root and shoot, regulating sulfur transport upwards.
Effect of root zone carbon dioxide enrichment on ethylene inhibition of carbon assimilation in potato plants
Authors: Govindarajan A. G. , Poovaiah B. W.
Published: April 2006

Potato plants (Solanum tuberosum L. var. Russet Burbank) treated with 1 μl ethylene 1−1 of air showed an inhibition of CO2 assimilation by 18%. The inhibition occurred after 3 h of exposure to ethylene and was not mediated through closure of the stomata. The enrichment of the root zone with CO2 almost completely abolished the ethylene inhibition of CO2 assimilation which was apparently due to an increase in the intercellular concentration of CO2 in leaves following enrichment. The effect of application of CO2 to the root zone on ethylene inhibition of CO2 assimilation seemed to last for a few days. Potato plants treated with aminoethoxyvinlglycine (AVG) showed an increase in fresh and dry weight as compared to non‐treated plants. Our results indicate that both CO2 and AVG alter the effect of ethylene and promote growth in plants by inhibiting ethylene action and biosynthesis, respectively.
Lipid and pigment changes during shoot initiation in cultured explants of Pinus radiata
Authors: Douglas Trevor J. , Villalobos Victor M. , Thompson Michael R. , Thorpe Trevor A.
Published: April 2006

Cotyledon explants of radiata pine contain principally lipid and protein reserve materials, which decline during shoot initiation. This process was followed phytochemically and ultrastructurally. Fatty acid and sterol analyses indicated that there were both quantitative and qualitative changes in the different classes of lipid. The most pronounced changes were an increase in the linolenic acid content of the polar lipids and the appearance of stigmasterol during shoot initiation. There was also a continued increase in chlorophyll and carotenoid levels, which paralleled chloroplast development. It appears that the changes observed were similar to those that occur in cotyledons during normal seedling development.
A two‐fold action of benzyladenine on chlorophyll formation in etiolated cucumber cotyledons
Authors: Dei Mitsuru
Published: April 2006

Treatment of 3‐day‐old excised etiolated cotyledons of cucumber (Cucumis sativus L. cv. Aonagajibai) with benzyladenine (BA) in the dark stimulates chlorophyll (Chl) formation during the lag phase (designated as ‘lag elimination’) and accelerates the steady‐state rate of Chl formation under subsequent continuous illumination with white light. The separation of this two‐fold effect is possible using two different methods of BA treatment in darkness: a brief BA treatment followed by various periods of water treatment in darkness, or various periods of continuous dark BA treatment. In either treatment, BA rapidly eliminates the lag phase (the fast‐appearing effect) and after a longer time period accelerates the steady‐state rate (the late‐appearing effect). With a brief BA treatment, both effects decay rapidly. In contrast, with continuous BA treatment, none of the effects decay after reaching their maxima, particularly in cotyledons excised 2 days after sowing and aged for a long period before the onset of BA treatment. These facts indicate that BA acts as a trigger in stimulating Chl formation. The relationship between the actions of BA and light is discussed.
Growth and translocation of C and N in wheat (Triticum aestivum) grown with a split root system
Authors: Lambers Hans , Simpson Richard J. , Beilharz Vyrna C. , Dalling Michael J.
Published: April 2006

The root system of wheat seedlings (Triticum aestivum L. SUN 9E) was pruned to two seminal roots. One of the roots was supplied with different levels of NO3, the other was deprived of N. Root respiration and the increment of C and N in roots and shoots were measured to determine the C/N ratio of the phloem sap feeding the N‐deprived roots. Thus it was possible to determine translocation of N from the shoots to the roots. It was calculated that the C/N ratio of phloem sap feeding roots of plants growing at optimal and suboptimal N supply was ca 54. A supra‐optimal N supply reduced, whilst shading increased, the C/N ratio of phloem sap. At optimal N supply 11% of all N transported to the shoots was retranslocated to the roots. Both a supra‐optimal and a limiting N supply increased translocation of N back to the roots to 18% of the N translocated to the shoot, whilst shading of the plants decreased the proportion cycled to 7%. At the optimal N supply, 40% more N was translocated to the roots from the shoot than was incorporated by them. At a lower supply of N, 80% more N was imported from the shoots than was incorporated by these roots. It is suggested that the distribution of N between roots and shoots predominantly occurs in the shoots. The specific mass transfer rate in seminal roots was determined. The highest value was found for roots grown with an optimal N supply: 1.1 mg carbohydrate s−1 cm−2 (sieve tube) which is well within the range observed for other plant organs. Roots supplied with NO3 produced more and longer laterals than N‐deprived roots. It is suggested that this is due to the effect of NO3 on import of carbon and other components transported in the mass flow with carbon.
Kinetin application to roots and its effect on uptake, translocation and distribution of nitrogen in wheat (Triticum aestivum) grown with a split root system
Authors: Simpson Richard J. , Lambers Hans , Dalling Michael. J.
Published: April 2006

The root systems of wheat seedlings (Triticum aestivum L. cv. SUN 9E) were pruned to two seminal roots. One of the roots was supplied with a suboptimal level of NO3, the other was deprived of N. Different levels of kinetin were supplied to the NO3‐deprived roots. Root respiration and the increment of C and N in the roots were measured to determine the C/N ratio of the phloem sap feeding the NO3‐deprived roots. Thus, it was possible to determine retranslocation of N from the shoots to the roots, as affected by the rate of kinetin application. It was calculated that the C/N ratio of phloem sap feeding roots growing without kinetin was ca 61. Kinetin application increased this ratio to ca 75, partly due to decreased translocation of N from the shoots back to the roots. Kinetin application decreased the proportion of N that was retranslocated to the roots after translocation to the shoots. Kinetin increased the rate of NO3 uptake per root and the rate of N incorporation in both roots and shoots by ca 60%, but had no effect on shoot dry matter production. In control plants at most 70% of the N incorporated in the NO3‐fed roots could have been imported from the shoots, whilst kinetin application reduced this value to ca 40%. Thus root growth was not fully dependent on a supply of N via the phloem.

It is concluded that cytokinins affect the pattern of N‐translocation in wheat plants by increasing incorporation of N in dry matter of the shoot, thus leaving less for export. Cytokinins did not play a major role in the regulation of shoot growth and the shoot to root ratio of the present plants.
Genetic differentiation in Plantago major: Ca2+‐ and Mg2+‐stimulated ATPases from roots and their role in phenotypic adaptation
Authors: Kuiper Daan
Published: April 2006

The Mg2+‐ and Ca2+‐stimulated ATPase activities of the microsomal fractions of the roots of four inbred lines of Plantago major L. were followed at two levels of mineral nutrition. In addition the response of a transfer of plants from one condition to the other was studied. Kinetic properties of the ATPases (Km and Vmax) were calculated and used to differentiate between genetic differences among the inbred lines and the plasticity within each inbred line. The Vmax values of the ATPase activity differed significantly between the lines and were directly related to seed number per capsule (low Vmax→ 11 seeds per capsule, high Vmax→ 33 seeds per capsule). In addition, the Vmax values of the ATPase acitivty may be related to ecological strategy. Plasticity of enzyme activity is expressed in differences in the Vmax values of the ATPase activity, as a response to nutritional level or changes of the strength of the nutrient solution. Differences in this plasticity in the four selected lines and in rapidity of response to a change in mineral nutrition were directly related to the ecological strategy. These results are discussed in relation to the strategy of the genotypes for survival in the field. The presence of plasticity in line 4 (ssp. pleiospema) makes this genotype behave like an annual plant, following a ruderal strategy. The absence of plasticity in line 1 (ssp. major) fits a more competitive strategy.
The antagonism of IAA‐induced hydrogen ion extrusion and coleoptile growth by diclofop‐methyl
Authors: Shimabukuro M. A. , Shimabukuro R. H. , Walsh W. C.
Published: April 2006

Diclofop‐methyl (DM) (ester) was readily absorbed by peeled and unpeeled coleoptiles of wheat, Triticum aestivum L. cv. Waldron, and oat, Avena sativa L. cv. Garry. Substantial absorption of diclofop (acid) occurred only in peeled coleoptiles of the two species. IAA‐induced acidification in peeled coleoptiles of both species was inhibited by 100 μM DM or diclofop (acid) during a 3 to 4 h period. There was no recovery of acidification after DM or diclofop inhibition in oat coleoptiles; however, acidification in wheat coleoptiles recovered from inhibition by DM but not from diclofop. The recovery from DM inhibition may be due to a reduction in the diclofop pool derived from DM by efflux and metabolism (detoxification) in peeled wheat coleoptiles. Diclofop was not detoxified in oat coleoptiles. IAA‐induced elongation of unpeeled oat coleoptiles was inhibited totally by 100 μM DM but not by 100 μM diclofop after 3.3 h of treatment. Wheat coleoptile elongation was relatively unaffected by either DM or diclofop. Basal elongation (no IAA) of both wheat and oat coleoptiles was inhibited by DM and diclofop. The inhibition by DM appeared to be irreversible, whereas the inhibition by diclofop was overcome by the addition of 10 μM IAA.
Ontogenetic changes in potassium transport in xylem of tomato
Authors: Widders Irvin , Lorenz Oscar A.
Published: April 2006

The influence of plant ontogeny on xylem exudate K+ concentrations and K+ transport to the shoot was studied in both nutrient‐solution and field‐grown tomato plants (Lycopersicon esculentum).

K+ concentrations in xylem exudate from decapitated plants decreased during tomato plant development from a high of 12 mM to a low of 5 mM. In the nutrient‐solution plants, the most rapid decline occurred during the vegetative growth phase, while in field‐grown plants, the xylem K+ concentrations remained high during an‐thesis and then subsequently declined. The rapid decline in nutrient‐solution plants might be related to a decrease in the absorptive efficiency of the root system. In field‐grown plants, a reduction in the availability of assimilates to the root might account in part for the decrease in xylem exudate K+ concentrations. The volume (ml h−1 plant−1) and the net rates of K+ exudation (mmol h−1 plant−1) decreased dramatically as the fruits approached maturity. Since only a small reduction in xylem exudate K+ concentrations occurred during fruiting, the hydraulic conductivity of the root system decreased as the tomato plants aged. It is proposed that the ontogenetic changes in xylem transport of K+ contribute to a reduction in leaf free space K+ concentration which would explain the decline in tomato leaf K+ concentrations.
Studies on the distribution of Na and CI in two species of lupin (Lupinus luteus and Lupinus angustifolius) differing in salt tolerance
Authors: Van Steveninck R. F. M. , Van Steveninck M. E. , Stelzer R. , Läuchli A.
Published: April 2006

The distribution of K, Na and CI in various tissues was studied in two species of lupin, Lupinus luteus L. (ex. Portugal) and L. angustifolius L. (cv. Kubesa) under conditions of NaCl‐induced salinity stress. L. luteus appeared more tolerant to salt and less effective in excluding Na and Cl from its above‐ground parts than L. angustifolius. Electron probe X‐ray microanalysis of vacuolar contents of individual root cells of salt‐treated L. luteus showed a decreasing gradient of Na and CI contents from the epidermis inwards, but in the inner cortical cells adjacent to the pericycle/endodermis, Na levels were again high while Cl remained low. L. luteus may be inefficient in restricting entry of Na into the shoot because of a limited capacity for Na storage in the vacuoles of root cells. In addition, this species appears to exclude Cl from the vacuoles of inner cortical root cells but not from its symplastic pathway. In the leaves of L. luteus, Cl levels were particularly high towards the lower surface (abaxial side), while Na accumulated in the adaxial side of the leaf. Likewise, different cells of the petiole appeared to place unequal demands on Na and Cl for osmotic adjustment. It is suggested that excess Na in the adaxial side of the leaf and the generally high levels of Na and CI in the foliage may explain the 50% fresh weight stimulation which was observed in L. luteus but not in L. angustifolius at 50 mM NaCl. However, the halophytic response of L. luteus is limited to moderate concentrations of NaCl since 100 mM NaCl caused severe necrosis and leaf abscission.
The apical control of lateral bud development in excised shoot tips of Cuscuta reflexa cultured in vitro
Authors: Maheshwari Ramesh , Sreekrishna Shailini
Published: April 2006

Excised shoot tips of Cuscuta reflexa Roxb. (dodder), a rootless and leafless angiospermic plant parasite, were cultured in vitro for the study of the control of lateral bud development by the apex. In a chemically defined medium lacking hormones, the basal bud alone developed into a shoot. The addition of coconut milk to the growth medium induced the activation of multiple lateral buds, but only a single bud developed further into a shoot. The decapitation of this shoot induced the development of another shoot and the process could be repeated. This showed the controlling effect of the apex in correlative control of bud development. Application of indole‐3‐acetic acid to the shoot tip explant delayed the development of the lateral bud. Gibberellic acid A3 induced a marked elongation growth of the explant and reinforced apical dominance. The direct application of cytokinin to an inhibited bud relieved it from apical dominance. A basipetally decreasing concentration gradient of auxin may prevail at the nodes. Bud outgrowth is probably stimulated by cytokinin produced locally in the bud.
Effect of flooding on tomato cultivars: The relationship between proline accumulation and other morphological and physiological changes
Authors: Aloni Beny , Rosenshtein Gila
Published: April 2006

Flooding of the root system of tomato plants (Lycopersicon esculentum) caused cessation of leaf elongation, leaf epinasty, formation of adventitious roots, and increase in diffusive resistance associated with the wilting of leaves at the first stage of the stress. Upon development of adventitious roots, the wilted leaves regained their turgor and the diffusive resistance slowly decreased at a rate slower than that at which water potential increased. In the course of flooding, proline accumulated but after 11 days dropped back to the control level. The extent of proline accumulation in various tomato cultivars was positively correlated with the extent to which their leaf water potential dropped, but was not correlated with the changes in their diffusive resistance. Cultivars which accumulated the highest proline levels were those which showed the most severe injury, with only one cultivar as an exception. However, only in the cultivars producing high levels of proline was the return of leaf turgor followed by resumption of leaf elongation. In cv. ‘Hosen’, which was severely injured by the stress, but accumulated a low level of proline, leaf elongation was not resumed. The results suggest that proline accumulation is an indicator of the cultivar's sensitivity to dehydration associated with the flooding stress, and confirm the notion that proline may play a role in the post‐stress recovery process.
Translocation of nitrogen in a vegetative wheat plant (Triticum aestivum)
Authors: Simpson Richard J. , Lambers Hans , Dalling Michael J.
Published: April 2006

The translocation of nitrogen was studied in vegetative wheat plants (Triticum aestivum L. cv. SUN 9E) grown with a limited supply of nitrogen. The concentration of nitrogen in xylem sap exuding from the excised roots was the same as the nitrogen concentration in the transpiration stream. Translocation of nitrogen to the shoot was, therefore, calculated as the product of the transpiration rate and the concentration of nitrogen in xylem exudates. On the 22nd day from sowing more nitrogen was translo‐cated to the shoot than it incorporated, and 56% of the nitrogen translocated to the shoot was retranslocated to the roots. The nitrogen retranslocated to the roots was more than adequate to supply the requirements of the roots for growth, and the balance of the retranslocated nitrogen was reloaded into the xylem stream. Expressed as a proportion of the total increment of nitrogen in the plant on day 22, between 79 and 100% of the nitrogen absorbed by the plant was “cycled'’ in the plant (root → shoot → root → shoot). It is suggested that the size of this mobile reserve of nitrogen may vary depending on the growth requirement of the plant, its nitrogen‐uptake capacity and the contribution of nitrogen from mobilisation of leaf protein during senescence.
Translocation and utilization of carbon in wheat (Triticum aestivum)
Authors: Lambers Hans , Simpson Richard J. , Beilharz Vyrna C. , Dalling Michael J.
Published: April 2006

Wheat (Triticum aestivum L. cv. SUN 9E) was grown in a growth chamber under conditions of low soil nitrogen. Translocation of carbon to the roots and the subsequent utilization of these carbohydrates was determined. In vegetative plants (22 days old), 21.5 mg C day−1 were translocated to the roots. 29% of this was incorporated into dry matter, 32% was respired (28% via the cytochrome and 4% via a SHAM‐sensitive, presumably the alternative nonphosphorylating, pathway) and 39% was translocated back to the shoots, mainly in the form of amino acids. – The rote of root maintenance respiration during the vegetative phase was estimated to be 0.7 mg O2 h−1 (g dry weight of roots)−1 and the root growth respiration to be 0.41 g O2 (g dry weight of roots)−1. Total carbohydrate utilization due to root respiration via the alternative, nonphosphorylating pathway during the major part of the growth period was calculated to be only ca 6% of carbohydrate utilization for grain growth. The rate of specific mass transfer (SMT) of sugars in the sieve tubes was estimated from the data on C‐translocation and data on the total area occupied by sieve tubes in a cross section of the root system. SMT was calculated to be 0.8 mg sucrose s−1 cm−2, which is very similar to the published value on SMT for other organs, except roots.
Roles of auxin and gibberellic acid in growth and maturation of epicotyls of Vigna angularis: Cell wall changes
Authors: Nishitani Kazuhiko , Masuda Yoshio
Published: April 2006

The effects of auxin and gibberellic acid on cell wall composition in various regions of epicotyls of azuki bean (Vigna angularis Ohwi and Ohashi cv. Takara) were investigated with the following results. (1) Young segments excised from apical regions of the epicotyl elongated in response to added 10−4M indole‐3‐acetic acid (IAA). When the segments were supplied with 50 mM sucrose, the IAA‐induced segment growth was accompanied by enhanced overall synthesis of cell wall polysaccharides, such as xyloglucans, polyuronides and cellulose. This IAA effect on the cell wall synthesis is a consequence of extension growth induced by IAA. Gibberellic acid (GA) at 10−4M synergistically enhanced the IAA‐induced cell wall synthesis as well as IAA‐induced extension growth, although GA by itself neither stimulated the cell wall synthesis nor extension growth. In the absence of sucrose, cell wall synthesis was not induced by IAA or GA. (2) In mature segments excised from basal regions of the epicotyl, no extension growth was induced by IAA or GA. GA enhanced the synthesis of xylans and cellulose when the segments were supplied with 50 mM sucrose. IAA had no effect on the cell wall synthesis. These findings indicate that synthesis of polyuronides, xyloglucans and cellulose, which occurs during extension growth of the apical region of the epicotyl, is regulated chiefly by auxin whereas synthesis of xylans and cellulose during cell maturation in the basal region of the epicotyl is regulated by GA.
The simultaneous use of 14CO2 and 15N2 labelling techniques to study the carbon and nitrogen economy of legumes grown under natural conditions
Authors: Warembourg Fernand R. , Montange Denis , Bardin René
Published: April 2006

A method based on simultaneous short‐term exposure to 14CO2 and 15N2 is described for studying nitrogen fixation and distribution in legumes relative to carbon assimilation and use. Equipment designed to accomodate experiments under natural conditions with very little disturbance of the N2 fixing association is used. It permits continuous measurement and regulation of variables such as air temperature, humidity and CO2 concentration as well as soil aeration. Measurements of distribution and use of assimilates, respiration of nodulated roots, quantitative N2 fixation and the distribution and fate of fixed N as a function of time lead to a precise estimation of C and N budgets for each labelling period. When experiments are done at several phenological stages they give a new insight into the complex C and N interrelations in legume symbiosis.

A series of trials throughout the growth period of Glycine max (L.) Merr. cv. Hodgson demonstrated the sensitivity of the method. The development of the plants from vegetative to reproductive stages was accompanied by a complete change in the distribution patterns of current assimilates and products of nitrogen fixation. Maximum sink strength moved from the leaves to the pods and seeds which ended up receiving 70% of the incoming C and 35% of the fixed N. The fact that up to 85% of fixed N in the plants was in the reproductive organs at maturity can be accounted for by remobilisation from vegetative parts.

The respiration of nodulated roots utilized 33% of carbon translocated to below‐ground plant parts before nitrogen fixation started, but as much as 50% during the period of optimal fixation. The advantages and limitations of the isotopic method described are critically discussed as a prelude to future investigations.
Effects of desiccation on the 77°K fluorescence properties of the liverwort Porella navicularis and the isolated lichen green alga Trebouxia pyriformis
Authors: Öquist Gunnar , Fork David C.
Published: April 2006

The liverwort Porella navicularis and the isolated lichen green alga Trebouxia pyriformis were desiccated in darkness and light. Low temperature (77°K) fluorescence emission spectra were deconvoluted into band components by RESOL. The reasons for the desiccation‐induced decreases of fluorescence yield, particularly of the PSII emission bands, were analyzed by following fluorescence kinetics of PSI and PSII during PSII trap closure at 77°K, and by the determination of two point relative action spectra for PSI and PSII emissions upon excitation of chlorophyll a or b preferentially.

It was concluded that the pronounced loss of FII in Porella was largely accomplished by a strong decrease in the rate constant for fluorescence (kFII), whereas the energy transfer from PSII to PSI, (kT(II→I)), was unaffected or slightly decreased. Desiccation of Porella also decreased α, the fraction of absorbed light distributed initially to PSI. Unlike Porella, Trebouxia responded to desiccation by only a small decrease in fluorescence. The drop in FII was probably due to a 10–20% increase in kT(II→I); kFII was unaffected. No significant changes in α were observed in Trebouxia. A general lowering of the fluorescence yields of both species was probably also mediated by some PSII reaction center quenching of Fv in the dry samples. The results of two point relative action spectra confirmed the above findings and it was assumed that the more pronounced effects of light drying compared to that of dark drying, were mediated by changes in similar parameters. The difference in desiccation responses between Porella and Porphyra (Öquist and Fork 1982) are discussed and assumed to be related to the different habitats of these two species, deep shade vs exposed sun, respectively.
Seasonal and physiological aspects of the isolation of tobacco protoplasts
Authors: Cassells Alan C. , Cocker Frances M.
Published: April 2006

The viability of tobacco (N. tabacum– L. cv. Xanthi‐nc) protoplasts isolated during the winter months is affected by membrane calcium, total calcium, plant age and supplementary lighting. Feeding calcium nitrate and calcium chloride helps to increase protoplast stability. Feeding is important because it increases membrane calcium, but it also has other beneficial effects which may be connected with increased nitrate and chloride (anion) uptake and cation/anion interaction. Whatever optimal feeding regime is chosen, it must be used in conjunction with the correct harvesting practice, which depends on whether or not supplementary light is given. Plants grown without supplementary light are best harvested between 8–9 weeks. If supplementary light is given, older plants (with and without supplementary calcium feeding) of approx. ten weeks are better for protoplast isolation. Plants grown under supplementary light have low leaf shape index (LSI) values (i.e. wider leaves) compared to plants in low light.

Spring and summer calcium feeding treatments had no significant effect on increasing total or membrane calcium. Likewise, there was no significant correlation between total/membrane calcium and percentage protoplast viability from days 0–5; and protoplasts isolated from plants grown in shade and fed with calcium salts, were no more stable than protoplasts from control plants. Irrespective of the feed treatments given, spring and summer plants older than about fifty days and grown under shaded and normal light conditions, produced poor protoplasts despite the fact that there was more calcium present in the membranes compared to protoplasts of younger plants. This decrease in percentage protoplast viability appears to be associated with changes in leaf shape. As plants age from 49–63 days, the leaf shape index (LSI) values increase (i.e. leaves are becoming narrower) and % protoplast viability decreases.
Phytochrome‐membrane interactions as a factor in stomatal opening
Authors: Roth‐Bejerano Nurit , Nejidat Ali , Itai Chanan
Published: April 2006

Red light enhances stomatal opening in Commelina communis L. This light effect is reversed by far‐red irradiation. Pretreatment with filipin, which competitively inhibits phytochrome binding to membranes, also inhibits light‐enhanced opening. The pretreatment with filipin is more inhibitory if preceded by red irradiation, than after far‐red irradiation. Similar results are obtained with cycloheximide and low temperature, which retard phytochrome synthesis more than its degradation. This result may indicate an enhanced release of phytochrome in the Pfr form from binding sites rather than release of phytochrome in the Pr form. This points towards the possibility that phytochrome degradation and its release from binding sites are coupled.
Leucine uptake by tomato leaf tissue under low temperature: Preincubation dependence of uptake reduction
Authors: Paull Robert E.
Published: April 2006

The uptake of 3H‐leucine by leaf fragments of Lycopersicon esculentum Mill. cv. Rutgers and L. hirsutum Humb. & Bonpl., a wild tomato, was studied. Two altitudinal races of L. hirsutum were used which differed in chilling tolerance. The temperature dependence of uptake was initially similar for all plant varieties. However, at temperatures below about 11°C, uptake progressively decreased in the more chilling‐sensitive varieties (L. esculentum, Low‐altitude L. hirsutum), but not in the more chilling‐tolerant (high‐altitude L. hirsutum) with increasing preincubation time. More than 60 min preincubation was required for this effect, and it was greatest at the lower temperatures. When leaf fragments, chilled for short periods of time (>22 h), were returned to 22°C, initial rates of uptake were recovered within 2 h. The relationship between membrane lipid changes and membrane protein activity under chill stress is discussed.
Physiology of rice tungro virus disease: Proline accumulation due to infection
Authors: Mohanty Santosh K. , Sridhar R.
Published: April 2006

Tungro virus infection stimulates proline accumulation in leaves of rice (Oryza sativa L.), especially in a sensitive cultivar, Taichung Native 1. Disease‐induced proline accumulation increases with the severity of the disease. Proline also accumulates in senescing, detached healthy rice leaves. The magnitude of proline accumulation in these leaves was further accentuated by ABA and retarded by kinetin. In the absence of drought stress, virus infection induces severe symptoms (stunting) in a drought tolerant cultivar (Lalnakanda 41) when compared to cultivars with intermediate (MW 10) and high sensitivity (Cauvery) to drought. Thus tungro virus mimics water stress in inducing proline accumulation in rice leaves. In both cases a common factor, ABA, may mediate proline accumulation. In drought stress, proline accumulation is associated with tolerance, while in virus stress, proline accumulation is connected with sensitivity. It is, therefore, clear that proline cannot always act to relieve physiological stress.
In vitro rooting of cloned shoots in Pinus pinaster
Authors: Rancillac M. , Faye M. , David A.
Published: April 2006

In vitro plantlet regeneration will be a sueful tool in reforestation only when rooting problems are overcome. Our study was therefore focused on Pinus pinaster rooting conditions.

Methods were used which permit multiple axillary (instead of adventitious) bud production in order to obtain genetically identical explants and hence to procure more homogeneous resutls. The hormonal treatment efficiency was then tested on several clones for rooting. Different substrates were compared. A mixture of peat and perlite (1/3, v/v) permitted rooting and the further development of the root system if humidity was properly controlled. The use of an agar medium avoided this difficulty; it supported root induction but resulted in limited growth.

For hormonal treatment, explants, submitted to a 12‐day‐period with NAA (10−6M) and then subcultured in an auxin‐free medium, gave rooting percentages ranging from 80 to 100%. In terms of rooting quality (intensity, growth rate and branching ability), a 15‐to 19‐day‐period of auxin treatment was more effective.

Application of this optimal treatment to several clones revealed slight differences within clones and between clones (80 to 100% of rooting according to the clone). Regenerated plantlets were able to undergo an autotrophic growth after transplantation under greenhouse conditions.
Evaluation of parameters affecting the yield, viability and cell division of Pinus pinaster protoplasts
Authors: David H. , David A. , Mateille T.
Published: April 2006

Various factors affecting the yield and viability of Pinus pinaster Ait. cotyledon protoplasts and the mitotic activity of or regenerated cells are described. A study of the effect of sterilization procedures of the plant material showed that whereas the organs collected from disinfested seedlings allow for good yield and viability of isolated protoplasts, germination under non‐sterile conditions favours a greater germinating capacity and stronger mitotic activity. Numerous clusters of from 10 to 15 cells were formed after 20 days of culture when a 5% aqueous solution of calcium hypochlorite was used as a sterilizing agent.

The effects of an additional purification of the enzymes showed that although yield and viability of the protoplasts are only slightly improved, the more highly purified enzymes on the other hand enhanced the mitotic activity markedly. Between the two total enzyme concentrations used (0.2 and 0.4%, and in which the relative ratio of each element was unchanged), only the lowest level supplied a debris‐free protoplast suspension; mitotic activity occurred only in that case.

Comparison of the populations of cotyledon protoplasts collected from seedlings at two different growth stages (not fully‐developed or fully‐expanded cotyledons) did not reveal any appreciable difference in their size distribution. Neither was the extent of cellular viability affected by the degree of cell differentiation at the time of collecting. On the other hand, the yield of protoplasts and the mitotic activity of the regenerated cells were greater when partially‐developed organs were used. Moreover a pretreatment of the elongating cotyledons with a mineral (half‐strength MS macronutrients and full‐strength micronutrients) and hormonal (15 μM BAP, 0.5 μM NAA) solution improved cell division frequency.
Divalent cation inhibition of barley root plasma membrane‐bound Ca2+‐ATPase activity and its reversal by monovalent cations
Authors: Caldwell Charles R. , Haug Alfred
Published: April 2006

The inhibitory action of divalent cations on the Ca2+‐ATPase activity of a plasma membrane‐rich microsome fraction isolated from the roots of barley (Hordeum vulgare L. cv. Conquest) was investigated. Using electron paramagnetic resonance spectroscopy to measure cation‐induced changes in membrane lipid properties, it was demonstrated that certain divalent cations (Ca2+, Cd2+, UO2+2) inhibit the Ca2+ ATP‐ase by restriction of lipid polar head group mobility and not by alteration of membrane surface potential. Monovalent cations which stimulate the Ca2+‐ATPase of barley roots (Na+, K+, ethanolamine HCl) can also reverse the Ca2+‐ATPase inhibition by Cd2+. The degree of Na+ reversal of Cd2+‐induced Ca2+‐ATPase inhibition was influenced by the nature of the anion.
Ethylene‐promoted formation of aerenchyma in seedling roots of Zea mays L. under aerated and non‐aerated conditions
Authors: Konings Hendrik
Published: April 2006

The role of ethylene in the formation of lysigenous cortical cavities (aerenchyma) in seedling roots of Zea mays L. cv. Capella, has been studied under aerated and non‐aerated conditions. Passing roots from air to aerated water or from an aerated nutrient solution to a non‐aerated solution, promoted cavity formation and was accompanied by an increase of the endogenous ethylene concentration. When the endogenous ethylene concentration of roots in aerated nutrient solutions, which otherwise would not produce much cavities, was enhanced by applying ethylene gas (0.1 and 1.0 μl 1‐1 in air) or the ethylene precursor 1‐aminocyclopropane‐1‐car‐boxylic acid, cavity formation was promoted. When, on the contrary, the endogenous ethylene concentration of the roots was reduced by adding the inhibitors of ethylene biosynthesis, cobalt ions and aminooxyacetic acid, or when the ethylene action was prevented by silver ions, cavity formation was prevented. It is concluded that endogenous ethylene controls the induction of cavity formation in the roots.
Mitochondrial activity during shoot formation and growth in tobacco callus
Authors: Brown Daniel C. W. , Thorpe Trevor A.
Published: April 2006

Mitochondria isolated from tobacco (Nicotiana tabacum L. cv. Wisconsin 38) callus growing on either shoot‐forming or non‐shoot forming medium show an increase in state 3 and state 4 respiration and a drop in respiratory control and ADP/O ratios after subculture. the protein content of the mitochondria fraction and the activity of succinate dehydrogenase, malate dehydrogenase, cytochrome c oxidase and catalase also increase after subculture but there is no apparent difference between shoot‐forming and non‐shoot‐forming tissue. For mitochondria assayed at their native osmolarities, a trend of higher respiration rates and respiratory control as well as lower levels of cyanide‐resistant respiration was observed for shoot‐forming tissue. Generally, differences were greatest after day 9 in culture, the time during which primordia formation occurred in the shoot‐forming callus. These patterns are in concert with the view that the shoot‐forming process has a high energy requirement which must be realized during the time of primordia formation.
The effect of δ‐aminolevulinic acid on red light‐induced unrolling of dark‐grown barley leaf sections
Authors: Sundqvist Christer , Briggs Winslow R.
Published: April 2006

Unrolling of sections from dark grown barley leaves (Hordeum vulgare L. cv. Klages) was stimulated by red irradiation. The unrolling started after a lag phase of 6‐8 h and was completed after 24 h. The effect of several keto and amino acids on leaf unrolling was compared with their effect on coleoptile segment expansion growth. Of the substances tested δ‐aminolevulinic acid had the most inhibitive effect on leaf unrolling and the least inhibitive effect on coleoptile segment expansion growth. Prolonged treatment caused a strong inhibition of the unrolling but with a short tretment, a stimulation of the unrolling occurred. The inhibitive effect of δ‐aminolevulinic acid was only found if the treatment started within 6‐8 h after the red irradiation. Kinetin and gibberellic acid could decrease the inhibitory effect of δ‐aminolevulinic acid. A possible role for δ‐aminolevulinic acid working as a triggering substance for leaf unrolling is discussed.
Effect of 2‐chloroethylphosphonic acid on capsule formation and alkaloid content in Papaver somniferum
Authors: Hsu An‐Fei C. , Forman Howard I.
Published: April 2006

Application of different concentrations of ethephon (2‐chloroethylphosphonic acid) to Papaver somniferum L. at the times of stem elongation, bud, and capsule formation produced different effects. Ethephon (10‐2M) retarded growth of the plant and inhibited capsule formation during stem elongation, significantly reduced capsule size during the flowering period, but did not alter capsule development during capsule formation. When applied during the period of stem elongation, ethephon (10‐3M and 10‐4M) reduced capsule size; alkaloid accumulation was reduced by ethephon at a concentration of 10‐3M, but slightly increased by 10‐4M. Ethephon (10‐3M and 10‐4M) did not alter capsule development or alkaloid content significantly when applied during bud formation, but stimulated capsule size and alkaloid content when applied during capsule formation. Pretreating the plants with Ag+ (silver nitrate) did not reverse the ethephon effect. The results suggest that capsule maturation and alkaloid accumulation in P. somniferum are modified by ethylene, which is produced as a result of exogenous ethephon treatment.
Effects of SO2on photosynthesis and ribulose bisphosphate carboxylase in pine tree seedlings
Authors: Hällgren Jan‐Erik , Gezelius Kerstin
Published: April 2006

Fumigations of 4–7 week old seelings ofPinus silvestris, with ca 400 μg SO2m‐3for 4–5 days resulted in a decrease both in net photosynthetic rate and in the levels of ribulose bisphosphate carboxylase activity of the primary needles. The effect on net photosynthesis was reversible. No visible damages were observed on the needles. Lower concentrations, ca 200 μg SO2m‐3, for ca 6 days inhibited net photosynthesis reversibly. The effect on net photosynthesis was not the result of stomata closure or of increased respiration. A dose‐response relation for the inhibition of net photosynthesis and ribulose bisphosphate carboxylase is suggested. A similar relation was observed for the chlorophyll content of the needles. The reversible inhibition of photosynthesis was evident only at high quantum flux density, and the quantum yield of photosynthesis at rate limiting quantum flux was not affected. This was also suggested from an experiment with Scots pine in the field.
Uptake of radioactivity by Lemna gibba from 1–14C‐indole‐3‐acetic acid applied to the medium
Authors: Bhatnagar Punam , Tillberg Elisabeth
Published: April 2006

Lemna gibba plants were incubated aseptically on medium containing labelled 10‐7M indole‐3‐acetic acid (IAA‐1‐14C). Most of the radioactivity disappeared from the culture medium during a 24 h light period. A high percentage of the loss was due to photolysis and only a low percentage of the radioactivity was recovered in the plants. Uptake of 14C by the plants was strongly stimulated by light. The radioactivity taken up by the plants was the sum of photosynthetically taken up 14CO2 and 14C taken up in IAA. Analyses with the indolo‐α‐pyrone fluorescence method revealed that the free IAA content was almost the same in plants grown in control and in IAA media for 5 h, whereas the amount of IAA which could be liberated by alkaline hydrolysis was doubled by the presence of IAA in the medium.
Regulation of phosphate influx in barley roots: Effects of phosphate deprivation and reduction of influx with provision of orthophosphate
Authors: Lefebvre Daniel D. , Glass Anthony D. M.
Published: April 2006

Barley plants were grown in nutrient solutions, which were maintained at either 0 (‐P) or 15 μMorthophosphate (+P). After 11 days phosphate influx into the intact roots of the ‐P plants began to increase by comparison with +P plants. During this period differences became apparent between the treatments in absolute growth rates, as well as in the root:shoot ratios. Phosphate influx in the ‐P plants continued to increase as a function of time, to a maximum value of 2.4 μmol (g fresh wt)‐1h‐1at 16 days after germination. This rate was 6 times higher than influx values for +P plants of the same age. During the period of enhanced uptake phosphate was strongly correlated (r2= 0.77) with root organic phosphate concentration. – The enhancement of inorganic phosphate influx into intact roots of ‐P plants was rapidly reduced by the provision of 15 μMorthophosphate. Typically, within 4 h of exposure to this concentration of phosphate, influx values fell from 1.80 ± 0.20 to 0.75 ± 0.03 μmol (g fresh wt)‐1h‐1, while inorganic phosphate concentrations of the roots increased from 0.12 to 1.15 μmol (g fresh wt)‐1during the same period. Hill plots of the influx data obtained during this period, treating root inorganic phosphate as an inhibitor of influx, gave Hill coefficients close to 2. The rapidity of the reduction of influx associated with increased root inorganic phosphate together with the Hill plot data provide evidence for an allosteric inhibition of influx by internal inorganic phosphate.