bluuebunny/crossref_metadata_2025 huggingface dataset:
Germination of Cicer arietinum seeds and thiourea‐induced phytotoxicity
Authors: Rodriguez D. , Matilla A. , Aldasoro J. , Hernández‐Nistal J. , Nicoläs G.
Published: April 2006

Thiourea, hydroxyurea, phenylthiourea, methylurea, methylthiourea, thiosemicarbazide and 2,2‐dithiodipyridine affected the germination of Cicer arietinum L. cv. Castellana (chick‐pea) seeds. Microscopic observations of the subapical zone of the radicle showed that thiourea induced an increase in cell volume and length when compared with control seeds germinated at 25° or 30°C in water. These results emphasize the importance of the processes controlling solute and water uptake during early germination of chick‐pea seeds. In contrast to this stimulation of volume increase, the thiourea‐treated seedlings were unable to synthesize chlorophyll when exposed to light. This toxic effect was reduced when thiourea was administered only during the first few hours of germination. Thiourea also caused an increase in the uptake of 3H‐thymidine and 14C‐leucine but it decreased their incorporation into DNA and protein, respectively. These results suggest a stimulation of plasmalemma exchange activities, but toxic or inhibitory effects on other metabolic processes necessary for normal development of seedlings.
Effect of thiourea on the ionic content and dark fixation of CO2 in embryonic axes of Cicer arietinum seeds
Authors: Hernández‐Nistal J. , Aldasoro J. , Rodriguez D. , Matilla A. , Nicolás G.
Published: April 2006

During the first 12 h of germination of Cicer arietinum L. (cv. Castellans) seeds, K+ is first lost into the surrounding medium and is later reabsorbed. Thiourea accelerates this reabsorption. Since there is an increase in the mobilization of K+ in response to thiourea, a greater accumulation of malate due to the carboxylation of phosphoenolpyruvic acid takes place as compared with that occurring in water. The subapical zone of the radicle accumulates the greatest amounts of water, K+ and malate. The variation in the “in vitro” activity of phosphoenolpyruvate carboxylase does not explain the difference in malate in response to the different treatments, consequently there must be chemical changes in the cytoplasm which favour this carboxylation “in vivo”. These results show that thiourea accelerates the mobilization of K+ and stimulates the dark fixation of CO2 in embryonic axes of Cicer arietinum.
Mycobiont‐cyanobiont interactions during dark nitrogen fixation by the lichen Peltigera aphthosa
Authors: Rai Amar N. , Rowell Peter , Stewart William D. P.
Published: April 2006

Acetylene reduction (nitrogenase activity) by excised cephalodia of Peltigera aphthosa Willd. slowly declined on transfer of the cephalodia from light to darkness. The decline was more rapid in the absence of CO2 or when phosphoenolpyruvate carboxylase activity was inhibited by adding maleic acid or malonic acid. When glutamine synthetase (GS) activity was totally inhibited by adding l‐methionine‐dl‐sulphoximine (MSX) the decline in nitrogenase activity in the absence of CO2 still occurred. However, this loss of activity did not occur when the mycobiont was disrupted using digitonin (0.01 % w/v) and the fixed NH4+ was released into the medium. The data suggest that dark CO2 fixation by the fungus supplies carbon skeletons which remove newly fixed NH4+ produced by the cyanobacterium. When such carbon skeletons are not available MH4+ accumulates and inhibits nitrogenase activity even in the absence of GS activity. It is probable that NH4+ and a product of GS exert independent inhibitory effects on nitrogenase activity.
Water stress injuries and tolerance as related to potassium efflux from winter rape hypocotyls
Authors: Shcherbakova Anna , Kacperska Alina
Published: April 2006

Desiccation‐ or immersion‐induced injuries in isolated winter rape (Brassica napus L. var. oleifera cv. Górczański) hypocotyls were highly correlated with potassium efflux and were reversible if the tissue damage was not severe (i.e. when less than 20% of electrolytes leaked from stressed tissue). The time‐course of leakage of potassium and other electrolytes showed that increased membrane permeability might result from stress‐induced disturbances in membrane integrity. Increased stress tolerance in hypocotyls predehydrated to a water saturation deficit of about 60% seemed to be due to stabilization of membrane structure rather than to promotion of a repair mechanism. The hardening effect of predehydration was more effective for potassium efflux than for efflux of other electrolytes.
Hormonal regulation of sex expression in Momordica charantia
Authors: Ghosh S. , Basu P. S.
Published: April 2006

Sex expression in a monoecious cucurbit, Momordica charantia L. (long–fruited variety ‘Karela’) can be regulated by application of gibberellin A3 (GA3), indole‐3‐acetic acid (IAA) and 3‐hydroxymethyl oxindole (HMO), an oxidation product of IAA, all of which promote female flowering. Both IAA and HMO accelerated ethylene evolution in the seedlings of this plant. While a low concentration of Ethrel promotes flowering, the effect was reversed with increased concentrations. Surprisingly, GA3 was the most effective growth regulator in increasing, femaleness. In untreated plants, levels of endogenous GA‐like substance increased progressively up to the age of 60 days, at which the ratio of male to female flowers was minimum.
Influence of spectral quality on the growth response of intact bean plants to brassinosteroid, a growth‐promoting steroidal lactone. II. Chlorophyll content and partitioning of assimilate
Authors: Krizek Donald T. , Mandava N. Bhushan
Published: April 2006

The chlorophyll content and partitioning of assimilate of bean (Phaseolus vulgaris L. ‘Pinto′) plants were determined 6 days after treatment of the second internode (I2 with 5 μg of brassinosteroid (BR), a growth‐promoting steroidal lactone. Plants were grown for 6 days under equal levels (90 μmol s‐1 m‐2) of photosynthetic photon flux density (PPFD) provided by cool white fluorescent (CWF) or incandescent (INC) lamps and equal levels of far‐red (28 W m‐2, 700–800 nm) radiation provided by the same INC or far‐red (FR) fluorescent lamps. Brassinosteroid treatment had no appreciable effect on total biomass production but caused a decrease of 15–20% dry matter distribution in the upper portion of the shoot, a small (4%) but constant increase in dry matter in l2 and a large (11–16%) increase in dry matter in the lower portion of the shoot (especially I1). Treatment with BR increased assimilate accumulation in the primary leaves, especially under INC and FR lamps, and reduced dry matter in the trifoliate leaves. BR also caused a 16–21% reduction in total leaf area and even a greater reduction in area of the trifoliate leaves, but significantly increased specific leaf weight of the primary leaves and the first trifoliate leaf and the amount of dry matter in the lateral shoots under all radiation sources. In comparison to controls, BR treatment increased dry matter accumulation in the treated internode 3.3x under CWF and 1.6x under INC or FR. BR treatment also increased chlorophyll content in the primary leaves under all radiation sources and in the trifoliate leaves under CWF and INC lamps. These findings suggest a possible mobilization role of BR and establish the importance of adequate PPFD (and photosynthate) for maximum swelling and splitting response to brassinosteroid.
Soybean leaf urease: Comparison with seed urease
Authors: Kerr P. S. , Blevins D. G. , Rapp B. J. , Randall D. D.
Published: April 2006

Soybeans, Glycine max (L.) Merr., from ureides for transport of nitrogen from the root nodule to the shoot. The most direct routes for ureide utilization include the degradation of ureide‐derived urea to NH3 and CO2. Ureolytic activity was found in leaf disks of soybean and exhbited optimal activity at pH 7 in the presence of a high concentration of urea (250 mM). In vitro studies showed neither urea amidolyase nor urea dehydrogenase activity in soybean leaves and the ureolytic activity was characterized as urease. Several biochemical properties of soybean leaf urease were determined and compared to seed urease properties. Soybean leaf urease differed from that of seed in five ways: pH optima (5.25 and 8.75), apparent Km (0.8 mM), no inhibition by hydroxyurea, faster electrophoretic mobility and no cross‐reactivity with soybean seed urease antibodies. The data suggest that urease is the primary urea metabolizing enzyme present in soybean leaves. The properties of soybean leaf urease support the conclusion that a unique isozyme of urease is present in leaf tissue.
Mode of interference of chlorosis‐inducing herbicides with peroxisomal enzyme activities
Authors: Feierabend Jürgn , Kemmerich Petra
Published: April 2006

In rye leaves (Secale cereale L. cv. Petkus “Kustro”) bleached in the presence of the chlorosis‐inducing herbicides aminotriazole, haloxidine, San 6706 or difunone in white light of 54.2 W m‐2 (5000 lx), catalase activity was very low. In addition, the activities of glycolate oxidase and hydroxypyruvate reductase were strongly diminished in treatments with San 6706 and difunone. The lowering of the peroxisomal enzyme activities was observed in red, but not in blue light and did not occur after treatment with the non‐bleaching pyridazinone derivative San 9785. The deficiencies of the peroxisomal enzymes did not appear to be involved in the initiation of the chlorosis. Instead they are probably produced as secondary consequences of the bleaching. Low peroxisomal enzyme activities were also obtained without herbicide treatment by growing the leaves in an atmosphere of 2% O2 and 3% CO2, but in this case were not accompanied by an increased sensitivity of the Chl to photooxidative bleaching. The peroxisomal enzymes reached as high activities as in untreated controls when the herbicide‐treated leaves were grown at a low light intensity of 0.106 W m‐2 (10 lx). After transfer of herbicide‐treated leaves grown under 0.106 W m‐2 to 306 W m‐2 (30 000 lx), catalase was strongly inactivated, even at 0°C. In treatments with San 6706 and difunone the increase of the activities of glycolate oxidase and hydroxypyruvate reductase was either stopped, remaining unchanged, or the enzymes were slightly inactivated after exposure to 306 W m‐2 (30 000 lx). The observations suggest that the inactivation of peroxisomal enzymes results from photooxidative events in the chloroplasts.
Phytochrome control of skotodormancy release in Grand Rapids lettuce achenes
Authors: Georghiou K. , Thanos C. A.
Published: April 2006

Light‐requiring Grand Rapids lettuce (Lactuca sativa L.) achenes develop skotodormancy when imbibed in darkness for 7 days at 25°C. Redried skotodormant achenes maintain this type of dormancy upon subsequent rehydration. At 25°C full germination of skotodormant achenes can be induced by continuous and intermittent red light illumination as well as by several brief red irradiations given daily. One brief (10 min) red light irradiation can partly break skotodormancy at 20°C, while at lower temperatures the same treatment results in full induction of germination. Phytochrome control of the release from skotodormancy is proven by a) the dependence of the germination response on the relative sequence of red and far‐red light in cyclic irradiations, and b) the reversion of red action by subsequent far‐red irradiation. The time course of germination of skotodormant achenes treated with intermittent red light depends upon the length of dark interval between the light pulses. Germination is considerably delayed compared to that of non‐skotodormant ones, induced by a single brief red light treatment. This fact in combination with the requirement, over a long period of time, of Pfr action for full manifestation of germination, indicates that skotodormancy is a deeper form of dormancy. It is concluded that the germination of lettuce achenes may always be subjected to phytochrome control.
Stomatal response to ATP mediated by phytochrome
Authors: Nejidat Ali , Itai Chanan , Roth‐Bejerano Nurit
Published: April 2006

External ATP stimulated stomatal opening in epidemal strips of Commelina communis L. in darkness following brief irradiation with white or red light. ATP had no effect in darkness after irradiation with far red light or in continuous light. Mg2+ stimulated stomatal response to ATP, which was shown to be taken‐up by the tissue. This implies that a Mg‐stimulated ATPase, that interacts with Pfr, may be involved in stomatal opening.
Compression wood in rooted cuttings of Douglas‐fir
Authors: Starbuck C. J. , Roberts A. N.
Published: April 2006

Rooted cuttings of three clones of Douglas‐fir [Pseudotsuga menziesii (Mirb.) Franco] were growing plagiotropically two seasons after propagation. The oblique growth habit of cuttings was due, in part, to dorsoconvex curvature of the wood of the original 12‐cm cuttings after rooting. In cross sections taken 1.5–2.0 cm from the bases of cutting stems, the total widths of xylem and compression wood were significantly greater on the morphologically upper (convex) than on the lower sides of the stems. This was due to an asymmetry in the growth ring produced the season following rooting. In nearly every cross section examined, 80–90% of the width of the upper side of this growth ring was compression wood. Examination of cross sections taken 1.5–2.0 cm from the distal ends of the wood of original cuttings revealed a shift in the position of compression wood formation during the second season. As the distal portions of their stems were displaced from the vertical by curvature, cuttings of two clones produced compression wood on their lower sides in this region. Cuttings from the third clone, which showed the least basal curvature, continued forming compression wood on their upper sides in the distal portions of the original cuttings.
Respiration during seed maturation
Authors: Miller Marna Geyer , Leopold A. Carl , Obendorf Ralph L.
Published: April 2006

The contribution of cytochrome and alternative pathways to respiration during soybean [Glycine max (L.) Merr. cv. Chippewa 64] seed formation and maturation was measured by oxygen consumption of embryonic axis and cotyledon tissues and of mitochondria isolated from immature seeds. Respiration rates (dry weight basis) declined duing the last month of seed maturation. Cyanide sensitive respiration (cytochrome pathway) accounted for 80 to 90% of total oxygen consumption throughout seed formation and maturation. The proportion of the total respiration resistant to 1 mM cyanide and inhibited by 1 mM salicylhydroxamic acid (alternative pathway) did not exceed 6%. A residual oxygen consumption, accounting for 5 to 15% of total respiration, persisted in the presence of both inhibitors. Likewise, virtually no alternative respiration was found in mitochondria prepared from immature seeds. The alternative respiratory pathway seems absent during soybean seed formation and maturation regardless of whether grown in the greenhouse or field.
Effect of light in the control of growth by auxin and its inhibitor(s) in the sunflower
Authors: Muir Robert M. , Zhu Liang‐ji
Published: April 2006

Diffusates from the hypocotyl and leaves of sunflower seedlings (Helianthus annuusL. cv. Mammoth) contain both auxin and inhibitor(s) of auxin‐induced growth. The auxin activity has been evaluated with the conventional Avena coleoptile bioassay employing negative curvature, The inhibitor activity has been determined with a newly developed bioassay, measuring the positive curvature response of the Avena coleoptile. This bioassay has been standardized by the response to 2,3,5‐triiodo‐benzoic acid. Diffusates from plants in darkness have higher auxin activity and lower inhibitor activity than diffusates from plants in light. Irradiation at 730 nm promotes auxin synthesis in leaves, and! irradiation at 660 nm promotes synthesis of the inhibitor.
Blue‐light reactivation of spinach nitrate reductase inactivated by acetylene or cyanide. Effects of flavins and oxygen
Authors: G. Mauriño Sofia , A Maria , Aparicio Pedro J. , Maldonado José M.
Published: April 2006

Nitrate reductase (NADH: nitrate oxidoreductase, EC 1.6.6.1) of spinach (Spinacia oleracea L.) leaves, inactivated in vitro by acetylene, was reactivated by irradiation with blue light. Red + infrared, green or white light of the same irradiance were less effective. The dehydrogenase activity of the nitrate reductase complex was not required for pliotoreactivation. Photoreactivation of cyanide‐inactivated nitrate reductase was greatly enhanced by the addition of 1 and 20 μ of either FMN or FAD; however, flavins showed a much smaller stimulatory effect on photoreactivation of acetylene‐inactivated enzyme. The effect of flavins was higher under anaerobic conditions. This might imply the direct ievolvement of excited flavins in the photoreactivation mechanism. Besides promoting photoreactivation, blue light irradiation led simultaneously to a gradual inactivation of the enzyme especially under air and 20 μ FMN, eventually abolishing the recovered activity of the enzyme.
Uptake and distribution of calcium, magnesium and potassium in cucumber of different age
Authors: Bengtsson B. , Jensén P.
Published: April 2006

Uptake and distribution of Ca+, Mg2+ and K2+ were investigated in plants of cucumber (Cucumis sativus L. var. Cila) which had been cultivated for 12, 19, 32, or 53 days in complete nutrient solution with 1.0 mM Ca2+, 2.0 mM Mg2+ and 2.0 mM K+. The + concentration was about the same in roots and shoots, while the Ca2+ and Mg2+ concentrations were low in roots compared to shoots. The K+ concentration decreased with increasing leaf age, while the Ca2+ and Mg2+ concentrations increased, except in older plants with flowers and fruits, where an increased concentration was found in the youngest leaves. This is discussed in connection with increased indoleacetic acid (IAA) synthesis in the shoot. Excision of leaves at different levels from 21‐day‐old plants, followed by uptake for 24 h from the nutrient solution on days 22 and 23, resulted in no immediate reduction in Ca2+ (45Ca) uptake. Transport of Ca2+ increased to leaves above and below the excision point and total Ca2+ uptake remained at the same level as for the intact plant. It is suggested that regulation of Ca2+ uptake is primarily achieved in the root while the distribution in the shoot is regulated by the accessability of negative binding sites.
N‐phenyl indolyl‐3‐biityraitiide and phenyl indole‐3‐thiolobutyrate enhance adventitious root primordium development
Authors: Haissig Bruce E.
Published: April 2006

N‐phenyl indoryl‐3‐butyramide (NP‐IBA) and phenyl indole‐3‐thiolobutyrate (P‐ITB) are new synthetic auxins that enhance rooting of bean (Phaseolus vulgaris cv. Top Crop) hypocotyl cuttings and jack pine (Pinus banksiana Lamb.) seedling cuttings. In comparison with an equal concentration of indole‐3‐butyric acid (IBA), NP‐IBA treatment resulted in greater rooting of bean and jack pine seedling cuttings. IBA and P‐ITB treatment at equal concentration were equally effective in inducing rooting of bean cuttings. However, in comparison with an equal concentration of IBA, P‐ITB treatment promoted greater rooting of jack pine seedling cuttings, but P‐ITB treatment was less effective than NP‐IBA treatment. Application of crystalline chemical to jack pine seedling cuttings indicated lesser toxic effects and earlier and greater root‐promoting effects of P‐ITB and NP‐IBA treatments, in comparison with IBA treatment. The earlier rooting of NP‐IBA‐treated jack pine seedling cuttings was positively related to increase in fresh weight of basal 1 cm stem before primordia were initiated. Weight of basal steins of NP‐IBA‐treated cuttings initially increased during propagation at day 2 in comparison with the control, and at day 3 in comparison with IBA‐treated cuttings. Results that were obtained with seedling jack pine cuttings were generally confirmed for cuttings from 7‐year‐old trees.
Internode length in Pisum. III The effect and interaction of the Na/na and Le/le gene differences on endogenous gibberellin‐like substances
Authors: Potts Wendy C. , Reid James B.
Published: April 2006

In the garden pea (Pisum sativum L.), shoots of the extremely short plants with the mutant na (phenotype nana) are found by bioassay to contain undetectable levels of gibberellin‐like substances. This is confirmed by the use of near isogenic lines differing at the Na locus. Thus, mutant na appears to block a step early in the pathway of gibberellin synthesis. It is suggested that the polar gibberellin‐like substance found in the apical portion of shoots of tall (Le) but not dwarf (le) peas could be GA1. Extracts of shoots of na Le peas treated with GA20 (the major active gibberellin in dwarf peas) possess a large amount of GA1‐like activity whereas extracts of shoots of na le peas treated with GA20 possess a much reduced amount. Thus, gene Le may allow the conversion of a less active gibberellin (GA20) into one more active in stimulating elongation in the pea (the GA1‐like compound). In contrast to their influence in the shoot, the na and Le genes do not appear to be operative in controlling the gibberellin content of developing seed, indicating that organ specific gibberellin biosynthesis and metabolism occur in peas.
Growth of Populus euramericana
Authors: Pieters G. A.
Published: April 2006

Growth curves of successive leaves of Populus euramericana (Dode) Guinier ‘Robusta’ have been determined. With ample supply of water and nutrients the growth of a poplar shoot follows a fixed pattern: an initial logarithmic acceleration phase followed by a stationary phase in which leaves of equal size are produced at a constant rate. Analysis of growth curves of leaves enabled the growth curves of leaf primordia to be predicted. These primordial growth curves are compared to the indirectly determined growth curves of primordia by measuring the lengths of successive leaf primordia in the apex during the stationary phase of growth. The increase in length of successive leaves in the acceleration phase of growth continues for a longer period at high than at low irradiace. The relative growth rates of leaf primordia, leaves and internodes are discussed in terms of shoot growth and phyllotaxis.
Abscisic acid inhibits phloem loading of sucrose
Authors: Vreugdenhil D.
Published: April 2006

The effect of abscisic acid (ABA) on the uptake of sucrose by discs from castor bean (Ricinus communis L. cv. Zanzibarensis) cotyledons was investigated. Incubation on ABA solutions for one hour or longer significantly inhibited sucrose uptake. The effect was measurable at ABA concentrations as low as 0.1 μM. The inhibition was due to a lowering of the apparent Vmax of the sucrose‐carrier system, the Km being unaffected. Uptake of sucrose was coupled to proton uptake but ABA had no detectable effect on the latter process. It is suggested that ABA exerts an effect on the phloem loading of sucrose by enhancing the efflux of sucrose. In leaf discs from three other plant species (Beta vulgaris L., Petunia hybrida L. and Phaseolus vulgaris L.) ABA exerted a similar effect. The results are discussed with respect to source‐sink relationships.
Acides‐aminés et amines libres ?explants foliaires de Nicotiana tabacum cultivés in vitro sur des milieux induisant la rhizogenèse ou la caulogenèse
Authors: Malfatti H. , Vallée J. C. , Perdrizet E. , Carré M , Martin C.
Published: April 2006

Free amino acids and amines in leaf explants of Nicotiana tabacum cultivated in vitro on media inducing rhizogenesis or caulogenesis.

Foliar explants of Nicotiana tabacum cv. Xanthi n.c. were cultivated on three different media: (1) a basal medium without hormone, so that no differentiation occurred in the explants; (2) with auxin added; and (3) with auxin plus cytokinin added, where the additions (2) and (3) promote rhizogenesis and caulogenesis, respectively. The content of free amino acids and amines of the three kinds of explants were investigated. In the two media lacking cytokinin, the explants contained great amounts of five amino acids (asparagine, glutamine, proline, glutamic acid and histidine) and of one aromatic amine, tyramine. In the cytokinin containing medium, only two amines accumulated in the explants: one aliphatic polyamine (putrescine) and one aromatic amine (phenethylamine). The increase in amino acids began immediately on the first days of culture. It was related neither to a more active proteolysis nor to the breaking of the correlations from the mother plant. It was induced by the addition of nutritional elements into the medium. On the other hand, the accumulation of aromatic amines occurred after a few days of culture and was transitory. A decrease was observed after the first emergence of new organs. The relation between the accumulations of these aromatic compounds and formation of roots or shoots is discussed.
Effect of plant growth hormones and polyamines on ornithine decarboxylase activity during the germination of barley seeds
Authors: Kyriakidis Dimitrios A.
Published: April 2006

Gibberellic acid (GA3) and β‐indolylacetic acid (IAA), two of the well known growth hormones, induce four fold the activity of ornithine decarboxylase (ODC) during the germination of barley seeds (Hordeum vulgare L. var. Beca). The optimal concentration for induction of ODC was 10–5M for GA3 and 10–3M for IAA. When 10–3M of a polyamine, putrescine or spermidine, is added to the growth medium, ODC activity is significantly inhibited. This inhibition is due to the induction of a protein inhibitor of ODC (antizyme), whose apparent molecular weight is 16 000 ± 2 000 daltons. Addition of GA3 to cultures which have been grown for 50 or 98 h in the presence of polyamines, abolishes the observed inhibition of ODC activity, while in the reverse experiment, addition of polyamines at 50 or 98 h does not affect the ODC activity induced by GA3. Cadaverine, a physiological plant diamine, enhances ODC activity; whereas 1,8‐diaminooctane (the alkyl analogue of spermidine) does not have any effect.
Altering the sensitivity of strawberry plants to exogenous abscisic acid
Authors: Kubik Marek , Antoszewski Roman
Published: April 2006

Abscisic acid (ABA) causes the closure of stomata. By means of an infrared gas analyzer it was found that changes in the physiological status of Fragaria grandiflora Duch. cv. Red gauntlet, caused by pretreatment with exogenous ABA, decreased the sensitivity to the next dose of the hormone. A similar decrease of sensitivity to ABA may be obtained by shortening the light period. It is proposed that this decrease in sensitivity to ABA may be due to adaptation of guard cells to an excess of ABA.
Parasitic and mutualistic associations between a mycorrhizal fungus and soybean: The effect of phosphorus on host plant‐endophyte interactions
Authors: Bethlenfalvay Gabor J. , Bayne Henry G. , Pacovsky Raymond S.
Published: April 2006

Soybean [Glycine max (L.) Merr. cv. Kent] plants were colonized by the vesicular‐arbuscular mycorrhizal (VAM) fungus Glomus fasciculatum (Thaxt. sensu Gerd.) Gerd. and Trappe in pot cultures using an inert medium and a nutrient solution. Phosphorus was provided initially as 0, 25,50, 100 or 200 mg hydroxyapatite [HAP, Ca10(PO4)6(OH)2] per pot. Under the low (0 mg HAP) and high (100 and 200 mg HAP) P regimes, VAM plants showed 20, 25 and 38% growth retardation, respectively, relative to non‐colonized controls. At 50 mg HAP, VAM plant growth was significantly enhanced (14%). Dry weight and P content of both VAM and control plants increased with increased P availability throughout the HAP gradient. Intraradical VAM fungal biomass increased linearly with increasing P availability. Extraradical VAM fungal biomass was smaller than the intraradical component of the fungus at the lowest and highest levels of P addition in the growth medium. The ratio of extra‐ to intraradical mycelium, a suggested index of VAM fungal effectiveness, was greatest for the 50 mg HAP treatment, coinciding with growth enhancement of the host plant. This enhanced growth of the host at an intermediate P level was apparently a result of increased P uptake by the endophyte.
Lipid composition of prolamellar bodies and prothylakoids of wheat etioplasts
Authors: Ryberg Margareta , Sandelius Anna Stina , Selstam Eva
Published: April 2006

Prolamellar bodies and prothylakoids were fractionated from etioplasts of wheat (Triticum aestivum L., cv. Starke II, Weibull) and characterized with emphasis on lipid composition. The two fractions contained the same lipid classes. Glycolipids (monogalactosyl diacylglycerol, digalactosyl diacylglycerol, and sulphoquinovosyl diacylglycerol) were the dominating complex lipids. Phospholipids (mainly phosphatidyl choline and phosphatidyl glycerol) constituted between 10 and 15 mol% of the total amounts of polar lipids. Free sterols and sterol esters were present in low amounts (ca 6 mol%). Saponins could not be detected. The contents of glycolipids and protochlorophyllide were higher in the prolamellar body fraction than in the prothylakoid fraction on a protein basis, as was the protochlorophyllide content on a glycolipid basis. The molar ratio of monogalactosyl diacylglycerol to digalactosyl diacylglycerol was higher in the prolamellar body fraction (1.8) than in the prothylakoid fraction (1.2).

Since the same chemical constituents were found in the two membrane fractions we propose that the difference in ultrastructure between prolamellar bodies and prothylakoids is due to different relative amounts of lipids (glycolipids), protochlorophyllide, and proteins in the two membrane systems.
Grafting experiments on the nature of the decline in N2 fixation during fruit development in soybean
Authors: Malik Nasir S. A.
Published: April 2006

A decline in nitrogen fixation at the time of pod‐filling is persistently seen in soybeans. This phenomenon was studied by grafting experiments. Young scions with 3 nodes were grafted near the base of fruiting stocks which had passed their peak of nitrogen fixation. These grafts produced a second peak of nitrogen fixation on the same root system, indicating that the decline is reversible. If the scions were grafted near the apex of the fruiting stocks then the second peak of nitrogen fixation was very small. Thus, the translocation system could have an important role in regulating the decline in nitrogen fixation. Grafting of a second shoot of the same age as the rootstock, after the decline in nitrogen fixation, did not reduce the rate of decline even when the fruits from the scion were removed. It appears that physiological changes in different components of the shoot jointly regulate the decline in the rate of nitrogen fixation in soybeans.
Sporulation et mycosporines chez un champignon imparfait: Ascochyta fabae
Authors: Pittel Jean‐Louis , Bourguignon Brigitte , Arpin Noël
Published: April 2006

Sporalation and mycosporins in the Deuteromycete Ascochyta fabae.

To investigate the sporogenic activity of mycosporins, a strain of Ascochyta fabae Speg., in which conidiogenesis and mycosporin synthesis are easily induced, has been selected. In darkness, few mature pycnidia and little mycosporin are produced. Dry weight and mycosporin production were followed during mycelial growth and the conidiogenic phase, in both illuminated and non‐illuminated cultures: Mycosporin production appears closely linked with the morphogenic differentiation; its synthesis starts when the exponential growth is over. There is a good correlation between conidiogenesis and mycosporin production.

Irrespective of illumination, there is no increase in the rate of sporulation when maycosporins are added at different concentration levels. This cannot be explained by impermeability of the hyphae to mycosporins since uptake starts after a lag phase of 7 days and then proceeds until 15 to 20 days; at the same time the mycelium of A. fabae keeps its sporulation competence until 16 days after transfer to complete darkness. Mycosporin accumulated into conidiospores – 3 to 5% of dry weight – is not metabolized during the germination; on the contrary, a slight synthesis occurs after 20 h of germination.

Mycosporins thus seem to be secondary metabolites appearing as products from a type of metabolism that occurs at a very low level during mycelial growth and increases its activity during reproductive morphogenesis in numerous species of fungi.
Variation in the relationship between nitrogen fixation, leghemoglobin, nodule numbers and plant biomass in alfalfa (Medicago sativa) caused by treatment with arsenate, heavy metals and fluoride
Authors: Porter John R.
Published: April 2006

Potential relationships between alfalfa (Medicago sativa L. cv. Vernal) acetylene reduction activity (ARA) and leghemoglobin content, nodule numbers, shoot biomass, root biomass, or total plant biomass were estimated using linear regression analysis after treatment with a range of concentrations of arsenate, Cd2+, Cu2+, Pb2+, Zn2+, and F–. There were highly significant positive linear regressions between ARA and all the other plant values in the control plants, but this linear relationship was significantly altered between ARA and one or more of the other parameters in all treatments. There was also evidence for an alteration of the slope in some of the treatments when compared to control treatments even though a linear model was still applicable.
Frosthardiness development in Pinus sylvestris: The involvement of a K+‐stimulated Mg2+‐dependent ATPase from purified plasma membranes of pine
Authors: Hellergren J. , Widell S. , Lundborg T. , Kylin A.
Published: April 2006

Purified plasma membranes were prepared from needles of Scots pine (Pinus sylvestris L., Provenance Sodra Ydre), and the behavior of a K+ stimulated Mg2+‐dependent ATPase was studied. The microsomal fraction (1000‐30 000 g) was used for partition in a dextranpolyethylene glycol two‐phase system. Both upper and lower phases were washed twice with new upper and lower phase, respectively, yielding the fractions U3 and L3. After staining with STA (silicotungstic acid) and examining with an electron microscope, an enrichment of the plasma membranes in the U, phase was seen. This fraction was also enriched in K+ stimulated Mg2+‐dependent ATPase. The ATPase was rather specific towards ATP compared to other nucleosides, and had a pH optimum between 6 and 7. The activity of this ATPase was followed during a frost hardening‐dehardening cycle and showed an increased activity towards the end of the hardening period, whereas the activity decreased to normal during the dehardening period.
The exudation of solutes during senescence of oat leaves
Authors: Trippi Victorio , Thimann Kenneth V.
Published: April 2006

Exudation of cations and of amino acids from detached oat seedling leaves (Avena sativa L. cv. Victory) floated on water or solutions was measured under varied conditions. A small amount of exudation in the first 4 h, greater in the dark than in white light, is followed, one to 8 days later, by a relatively great increase which approximately accompanies senescence. This second increase is delayed by kinetin and is accelerated by abscisic acid or methyl jasmonate. both of which accelerate senescence. A nitrogen atmosphere (in darkness) causes immediate large exudation, mainly of potassium ions, and this is effectively delayed by light. There are two exceptions to the parallel between exudation and senescence; n‐pentanol, which strongly delays senescence in darkness, nevertheless increases exudation both of potassium and of amino acids, probably due to a direct effect on the plasmalemma. Cycloheximide, which also delays senescence, increases the exudation somewhat. Kinetin prevents or delays exudation under all conditions. Thus, the permeability of the plasmalemma increases greatly along with other criteria of senescence, but this change is probably not the principal cause of the senescence syndrome. Some of the effects are considered to result from reduction in available energy and others from a direct influence on plasmalemma permeability.
Membrane‐bound coupling factor ATPase activity during light‐induced chloroplast development in Euglena gracilis
Authors: Timko Michael P. , Schiff Jerome A.
Published: April 2006

Dark‐grown non‐dividing cells of Euglena gracilis Klebs var. bacillaris Cori were exposed to light for up to 72 h and thylakoid membrane fractions were isolated by sedimentation in sucrose step gradients at various stages of development. The membrane‐bound coupling factor (CF1)‐ATPase activity of these prothylakoids (0 h of light) and developing thylakoid membranes (12 to 72 h of light) was characterized by its cation specificity and sensitivity to inhibitors. The enzyme at all stages of development was activated by Mg2+ and to a lesser extent by Ca2+; Mn2+ was found to activate, as well as or better than Mg2 + at comparable concentrations. The activity of the enzyme was almost completely inhibited by dicyclohexylcarbodiimide (DCCD; 0.3 mM), but was insensitive to oligomycin, valinomycin and carbonyl cyanide P‐trifluoromethoxyphenylhydrazone (FCCP). Low concentrations of NH4CI gave a slight stimulation of enzyme activity, whereas high concentrations of the uncoupler were inhibitory. The specific activity of the membrane‐bound CF,‐ATPase was highest in prothylakoid membranes. Specific activity decreased on a thylakoid protein or chlorophyll basis during the first 12 h of development, and achieved a steady state level by 48 h following light induction. Estimates of total CF1‐ATPase activity per cell indicate that the time for major synthesis of the enzyme is between 12 and 3d h ol development. These results suggest that following an initial lag period in membrane development lasting about 12 h, there is a formation of CF1‐ATPase that accompanies further thylakoid membrane development.
Adaptation to sub‐ and supraoptimal temperatures of inbred maize lines differing in origin with regard to seedling development and photosynthetic traits
Authors: Stamp P. , Geisler G. , Thiraporn R.
Published: April 2006

Six inbred lines of maize (Zea mays L.) from cool temperate regions (C) and from warm regions (W) were grown at 14, 22, 30 and 38°C up to the same physiological age, the full expansion of the third leaf. Generally, plants developed smaller shoot dry weights and leaf areas at extreme temperatures. The shoot:root ratio was lowest at 22°C and highest at 30°C. Most lines had a minimum for specific leaf dry weight at 30°C, but W lines had a second lower minimum at 14°C. Phosphofructokinase activity scarcely reacted to temperature between 22° and 38°C; at 14°C one C line and all W lines had rather low activities. Generally, the chlorophyll content increased steeply from 14 to 22°C and decreased somewhat from 30 to 38°C. In C lines the carotenoid level decreased from 14 to 38°C. No uniform temperature response was found for PEP carboxylase activity, but the highest activity was mostly attained at 38°C. RuBP carboxylase activity increased considerably from 14 to 22°C and remained comparatively constant at higher temperatures. The highest activity of NADP malate dehydrogenase was found at 22°C, with a decrease up to 38°C and with second lowest values at 14°C. C lines possessed larger leaf areas, shoot dry weights and higher shoot:root ratios than W lines at 14 and 22°C, and higher specific leaf dry weights over the whole temperature range. The genotypic pattern of shoot dry weight at 14°C corresponded reasonably well with that of phosphofructokinase activity. A better adaptation of C lines to suboptimal temperatures was mostly clearly indicated for photosynthetic traits which have a well proven relationship with the chloroplast membranes: chlorophyll, carotenoids and RuBP carboxylase. The least distinct effects of origin were observed at 38°C; a tendency prevailed for a better performance of C lines with regard to phosphofructokinase, carotenoids, RuBP carboxylase and NADP malate dehydrogenase.
4‐Desmethylsterol composition of citrus rootstocks of different salt exclusion capacity
Authors: Douglas T. S. , Walker R. R.
Published: April 2006

Fibrous roots from seedlings of three citrus rootstocks (Rungpur lime, Kharna khatta and Etrog citron) grown hydroponically for 6 weeks in the presence or absence of 50 mM NaCl were analysed for their content of free, esterified, and glycosidic sterols. Leaf chloride analyses indicated that Rangpur lime was a good Cl‐ excluder and the other two rootstocks were Cl‐ accumulators.

On a dry weight basis and in the absence of NaCI only the free 4‐desmethyIsterol levels showed significant rootstock differences. Kharna khatta had the highest, and Rangpur lime the lowest, free stcrol levels. Sitostcrol was the major component of all sterol fractions of Rangpur lime, the esterified fraction of the other rootstocks, and the glycosidic sterol fraction of Kharna khatta. The ratio of sitosterol to stigmasterol was highest in Rangpur lime and lowest in Etrog citron in all cases and the ratio of apos;more‐planar apos; to apos;less‐planar apos; free sterols was highest in Etrog citron and lowest in Rangpur lime.

Treatment with 50 mM NaCI resulted in an increase in free sterol levels in Rangpur lime and a decrease in Kharna khatta. Steryl ester levels were unaffected in Rangpur lime but were significantly reduced in the other rootstocks. In all three sterol fractions the sitosterol/stigmasterol ratio was decreased. A decrease in the ratio of apos;more‐planarapos; to apos;less‐planarapos; free sterols was observed only in Kharna khatta and, more notably, Etrog citron. Salt‐induced changes in the apos;more‐planar apos; to apos;less‐planar apos; free sterol ratio correlated well with salt exclusion capacity.
Transport and redistribution of selenium in the bean plant (Phaseolus vulgaris)
Authors: Arvy Marie‐Pierre
Published: April 2006

After incubation for 3 h with (75Se) selenate, the selenium distribution in the bean plant (Phaseolus vulgaris L. cv. Contender) through a 29‐day period showed an uneven distribution: roots and trifoliate leaves were richer in 75Se than stem and primary leaves. The high selenium concentration of roots resulted from the retention of selenate by the root cells: at the end of the 29‐day period about 60° of the radioactivity was always ethanol‐soluble, and when analysed by paper chromatography, proved to be selenate. By contrast, much of the radioactivity of the leaves was ethanol‐insoluble, 75Se being quickly captured in metabolic processes which immobilize it. During plant development, a portion of the total selenium remains mobile and is continually mobilized to the younger organs which display a rapid growth rate. This delivery results from a progressive liberation of selenate retained by mature organs, especially the roots, and from turnover in older leaf tissues, especially the trifoliate leaves.
Indole‐3‐methylglucosinolate biosynthesis and metabolism in clubroot diseased plants
Authors: Rausch Thomas , Butcher Dennis N. , Hilgenberg Willy
Published: April 2006

lndole‐3‐methylglucosinolate biosynthesis and metabolism in roots of Brassica napus (swede, cv. Danestone II) infected with Plasmodiophora brassicae Wor. were investigated with a pulse feeding technique developed to infiltrate intact tissue segments with labelled substrates. Infected root tissue metabolized [14C]‐L‐tryptophan to indole‐3‐methylglucosinolate, indole‐3‐acetonitrile, and some other lipophilic indole compounds. The incorporation of radioactivity into these compounds was significantly enhanced in infected tissue compared with control tissue. A time course study showed a high turnover of indole‐3‐methylglucosinolate and indole‐3‐acetonitrile in infected tissue. However, thioglucoside glucohydrolase activity was not changed in infected tissue compared with control tissue. Disc electrophoresis revealed the same isoenzyme in both tissues. Control and infected tissues both rapidly hydrolyzed [14C]‐indole‐3‐acetonitrile in vivo. The possibility of a disease specific biosynthesis of indole‐3‐acetic acid from indole‐3‐methylglucosinolate as the result of a changed compartmentation is discussed.
Nutrition of winter wheat during the life cycle. I. Yield and accumulation of dry matter and minerals
Authors: Berczi Alajos , Olah Zoltan , Erdei Laszlo
Published: April 2006

Mineral uptake by winter wheat (Trilicum aestivum L. cv. Martonvasari 8) was studied throughout the life cycle. Accumulation of macronutrients (i.e. total nitrogen, phosphorus, potassium, sodium, magnesium and calcium) and the water content of roots and shoots of plants grown in complete nutrient solution were higher than those of plants grown in two types of soils. The supply of macronutrients was in some cases limiting for soil‐grown plants as revealed by a comparison of available and accumulated amounts of these nutrients. Their supply was abundant, however, for solution‐grown plants. This led to a doubling of grain yield for the latter plants with a three fold increase in accumulation of dry matter and a five‐fold increase in fresh weight. The efficiency ratios of solution‐grown plants to soil‐grown plants were approximately 1 for N and Na, 0.5 for Mg and Ca, and 0.3 for P and K.
Nutrition of winter wheat during the life cycle. II. Influx and translocation of potassium and phosphorus
Authors: Erdei László , Oláh Zoltán , Bérczi Alajos
Published: April 2006

Changes in the K, Na and P content of solution‐grown and soil‐grown winter wheat (Triticum aestivum L. cv. Martonvásári 8) were followed during the life cycle. In parallel experiments the influx of K+(86Rb) and H232PO‐4 and the translocation of these ions to the shoot were also measured. The K content increased during the seedling and tillering stages (autumn and winter period), but then decreased rapidly as the temperature rose. The influx and translocation of K+ increased during vegetative growth and declined in the generative phase. Na+ replaced K+ when K+ uptake was limited. The P content changed less than the K content, but influx was maximal during elongation. Both influx and translocation slowed greatly in the grain‐filling period. For both minerals the ratio of influx to net uptake was estimated for the life cycle. This ratio was high for the soil‐grown plants but low for the solution‐grown plants, suggesting that the supply of K and P was limiting the growth of the former but not of the latter plants. It is suggested that the transport of K and P during the life cycle is regulated by metabolism‐dependent direct routes (i.e. negative feedback mechanisms) during vegetative growth and by passive, indirect routes in the generative stage. The possibility of hormone‐directed transport processes is also discussed.
Cyanide‐resistant respiration in roots and leaves. Measurements with intact tissues and isolated mitochondria
Authors: Lambers Hans , Day David A. , Azcón‐Bieto Joaquín
Published: April 2006

A comparison was made between the oxygen uptake of roots and leaves and of mitochondria isolated from the same tissues. Ten species were included in this study: three legumes, one C3‐monocotyledon, one C4‐monocotyledon, the rest non‐leguminous C3‐dicotyledons. Root and leaf respiration in all species examined displayed substantial resistance to KCN (0.1–1.0 mM) and the cyanide‐resistant respiration was completely inhibited by salicylhydroxamic acid (SHAM; 10–20 mM). SHAM alone inhibited oxygen uptake to varying degrees, depending on the species. Mitochondria were isolated from roots and leaves of many of the species examined and also displayed cyanide‐resistant oxygen uptake, which was sensitive to both SHAM and tetraethylthiuram disulfide (disulfiram). Concentrations of SHAM greater than 2 mM caused inhibition of the cytochrome path as well as of the alternative path in isolated mitochondria. Respiration rates of intact roots and leaves in the presence of varying concentrations of SHAM alone were plotted against those obtained in the presence of both SHAM and KCN. This plot showed that in vivo the cytochrome pathway was not affected by 10 or 20 mM SHAM in the external solution. We conclude that the activity of the alternative pathway in intact roots and leaves can be reliably estimated by comparing SHAM‐sensitivity and cyanide‐resistance of respiration.