bluuebunny/crossref_metadata_2025 huggingface dataset:
Testing differences in relative growth rate: A method avoiding curve fitting and pairing
Authors: Poorter Hendrik , Lewis Charles
Published: April 2006

A method is discussed to test differences in relative growth rates. This method is based on an analysis of variance, with In‐transformed plant weight as dependent variable. A significant Group × Time interaction indicates differences in relative growth rates between groups. The advantages over the “classical” and “functional” growth analyses are: (1) No pairing procedure is required. (2) More than two groups may be evaluated in one analysis. (3) No decision is required about the polynomial used to fit the data. (4) By partitioning the interaction effect using orthogonal polynomials insight is gained into the nature of differences in relative growth rate. (5) By concentrating attention on the lower order terms of the polynomials, the influence of extraneous variation on conclusions may be minimized.
Does light‐promoted export from Commelina benghalensis leaves result from differential light‐sensitivity of the cells in the mesophyll‐to‐sieve tube path?
Authors: van Bel Aart J. E. , Koops Andries J. , Dueck Tom
Published: April 2006

In contrast to the light‐promoted uptake by mesophyll cells, light slightly inhibited sucrose uptake by stripped leaf disks of Commelina benghalensis L. This phenomenon appeared to result from a light‐promoted vein‐associated release, as light stimulated photosynthate release from stripped disks and inhibited that from mesophyll cells. In the ‐presence of the resorption‐blocker p‐chloromercuriphenylsulfonic acid, (PCMBS) the release of preloaded [14C]‐sugars (sucrose, glucose) and [14C]‐amino acids (alanine, asparagine, proline, valine, α‐aminoisobutyric acid) from stripped disks was doubled in the light. Illumination enhanced by 20 to 60% the release of endogenous leaf cell compounds (sucrose, H2PO‐4, K+, Mg2+, Ca2+) from stripped disks in the presence of PCMBS. Light also increased the export of [14C]‐assimilates from intact leaves by 20% after pulse‐labelling with 14CO2. A model for loading is proposed, based on the differential light sensitivities of the plasma membranes in the mesophyll‐to‐sieve tube path.
In vitro germination of some Western European orchids
Authors: Van Waes J. M. , Debergh P. C.
Published: April 2006

Several germination factors were studied in 23 Western European orchids in order to obtain a germination percentage which approximates the maximum percentage of coloured embryos after an adaptation of the tetrazolium test. The duration of seed pretreatment with Ca(OCl)2+ Tween‐80 was one of the most important factors controlling the germination of Western European orchids. Best germination occurred in continuous darkness at 23°C on dilute media. The nitrogen source had a species related influence. The best results were obtained with casein hydrolysate, although it could nearly be replaced by one amino acid, L‐glutamine. A cytokinin was required by Cypripedium calceolus and Epipactis hellborine but was not necessary for Lisiera ovata and Dactylorhiza maculata.

Experiments with 3 species have shown that the objective, to obtain a germination percentage, which approximated the maximum percentage of coloured embryos, was achieved. This has led to the elaboration of a basic sowing method for European orchids. The application of this method gave good germination responses with 21 of the 23 species tested.
Gibberellin‐biosynthesis and ‐sensitivity mediated stimulation of seed germination of Sisymbrium officinale by red light and nitrate
Authors: Hilhorst H. W. M. , Smitt A. I. , Karssen C. M.
Published: April 2006

Light stimulated seed germination of Sisymbrium officinale (L.) Scop, (hedge mustard) by means of two different mechanisms. Light effect I was absolutely dependent on the simultaneous presence of nitrate. Without nitrate, red (R) irradiated seeds did not escape from the antagonizing action of far‐red (FR) irradiation. The data indicated that nitrate acted as a cofactor at the level of the FR absorbing form of phy‐tochrome (Pfr). The combined action of R and nitrate could be replaced by addition of the gibberellins 4 and 7 (GA,4+7). This action could be inhibited by the growth re‐tardant tetcyclacis, an inhibitor to GA biosynthesis in cell free systems and intact plants. The action of tetcyclacis was fully neutralized by GA4+7. It is concluded that the combination of R and nitrate stimulated GA biosynthesis. Omission of nitrate from the incubation medium enabled the study of light effects apart from G A biosynthesis. In such conditions R stimulated the sensitivity to GA4+7, (light effect II). The two light effects could also be distinguished by their different reactions to the temperature of a pre‐treatment in water and darkness. The sensitivity to R and nitrate was subject to breaking and induction of dormancy. Both processes were stimulated at rising temperatures. Due to a different optimum, breaking of dormancy prevailed at lower temperatures and induction of secondary dormancy at more elevated temperatures. The sensitivity to GA4+7 rose and fell in a comparable way during dark incubation at a broad range of temperatures. The capacity of light to stimulate GA4+7, action did not diminish at higher temperatures, it even tended to rise. The study indicated that seed germination is regulated by an increase in both the levels of GAs and the sensitivity to GAs.
The role of endogenous gibberellins during fruit and seed development: Studies on gibberellin‐deficient genotypes of Arabidopsis thaliana
Authors: Barendse G. W. M. , Kepczynski J. , Karssen C. M. , Koornneef M.
Published: April 2006

Siliqua development was studied in the wild type line Landsberg erecta and the GA‐sensitive mutant ga‐1 of Arabidopsis thaliana (L.) Heynh. Reciprocal crosses between wild type and ga‐l mutant, and self pollinations of either parent have shown that siliqua growth is determined by endogenous GAs originating from maternal tissues and embryo. The ga‐1 mutant either self pollinated or cross‐pollinated with wild type pollen showed reduced siliqua growth, which to a large extent could be overcome by exogenously applied GAs. The siliquae of the ga‐1 mutant possessed very reduced ent‐kaurene synthesizing capacity and no detectable endogenous GA‐activity indicating an early block in the GA‐biosynthetic pathway. Seed weight is not affected by GA‐deficiency during development.
Suppression of nodulation in soybeans by superoptimal inoculation with Bradyrhizobium japonicum
Authors: Takats Stephen T.
Published: April 2006

Symbiotic nodulation of the primary roots of soybeans (Glycine max L. Merrill cv. Pride 216) is regulated by the plant, and is suppressed in response to a high inoculum dose of Bradyrhizobium japonicum USDA strain I–110 (ARS)+ applied at one time to the root. If an optimal dose is followed 10 h later by a superoptimal dose, nodules from the first inoculum near the base of the primary root are suppressed in a dose‐dependent way similar to that observed after single inoculations. The nodules which appear are probably derived from infections initiated by the bacteria in both inocula.
Inhibition of photosynthesis in Phaseolus vulgaris by treatment with toxic concentrations of zinc: effects on electron transport and photophosphorylation
Authors: Van Assche F. , Clijsters H.
Published: April 2006

Dwarf beans (Phaseolus vulgaris L. cv. Limburgse Vroege) were grown on a nutrient medium containing a toxic non‐lethal ZnSO4 concentration. The electron transport and photophosphorylation activities of chloroplasts, isolated from these beans, and from control plants, grown under standard nutrient conditions, were compared. Electron transport was significantly inhibited by Zn2+ treatment. Photosystem 2 activity proved to be more sensitive than photosystem 1 activity.

Inhibition was dependent on electron flow rate. Activity was fully restored with semicarbazide. EDTA‐washed thylakoid membranes were strongly manganese‐deficient. The results suggest that photolysis of water was primarily inhibited, due to a zinc‐induced deficiency in loosely bound manganese at the water‐splitting site. Manganese is probably substituted by zinc, since the zinc content of thylakoids increased five‐fold. Non‐cyclic photophosphorylation capacity was also limited as a result of inhibition of electron transport. Phosphorylation efficiency (ATP/2e ratio) involving both energy conserving sites was hardly affected.
A method for establishing ectomycorrhiza on conifer seedlings in steady‐state conditions of nutrition
Authors: Kähr Monika , Arveby Agneta S.
Published: April 2006

Scots pine (Pinus sylvestris L.), and Norway spruce (Picea abies (L.) Karst.) seedlings, inoculated with Suillus bovinits (L. ex Fr.) O. Kuntze and Paxillus involutus (Batsch) Fr., were grown on sloping plastic plates in growth units. A circulating nutrient solution flowed continuously over the plates. Nutrients in balanced proportions previously found to be appropriate for conifers, were added at a specified relative addition rate, in exponentially increasing amounts. The conductivity of the solution was kept low and stable (<50 μS cm−1). No carbohydrates were added.

Seedling nitrogen concentration and relative growth rate attained steady states in both inoculated and uninoculated treatments. The fungi infected the short roots within a few days and formed typical mantles and Hartig nets. This occurred in all treatments, including conditions of free access to nutrients, in which the nutrient concentration of the seedlings was optimal. The growth rate of the extramatrical mycelium was very high.
Polyethylene glycol and electric field treatment of plant protoplasts: characterization of some membrane properties
Authors: Hahn‐Hägerdal Bärbel , Hosono Kuniaki , Zaehrisson Anders , Bornman Chris H.
Published: April 2006

Petiolar protoplasts of a dihaploid line of winter oilseed rape Brassica napus L. ssp. oleifera were exposed to fusogenic polyethylene glycol (PEG) and electric field treatments. The surface properties and stability of membrane components of the treated protoplasts were investigated by contact angle measurements in aqueous two‐phase systems and differential scanning calorimetry, respectively. The leakage of intracellular components was estimated with respect to amino acids, proteins and DNA. Both fusogenic treatments resulted in the same apparent changes in membrane surface hydrophobicity and the same destabilization of membrane components. However, the PEG‐treated protoplasts were more leaky than both the control and the electric field‐treated protoplasts. The results indicate that the molecular mechanisms of PEG‐ and electrical field‐induced fusion are similar. However, the effects of the latter appear to be less harmful presumably because the parameters for electric field treatment are more easily controlled.
Mannitol metabolism in cultured plant cells
Authors: Thompson Michael R. , Douglas Trevor J. , Obata‐Sasamoto Hamako , Thorpe Trevor A.
Published: April 2006

Uptake and metabolism of [U‐14C]‐mannitol by suspension cultures of Damns carota L. cv. Kirodagosun and Nicotiana tabacum L. cv. Wisconsin 38, and by cotyledon cultures of Pinus radiata D. Don have been studied. Uptake of label ranged from 138 to 906 nmol (g FW)−1 h−1, resulting in absorption of 3 to 22% of the mannitol supplied to the cultures, over a 14 h incubation period. Of the absorbed mannitol 33 to 75% was metabolized, with label appearing in lipid, insoluble, acidic, basic, neutral and CO, fractions. No adaptation to culture with mannitol prior to the experiments was observed, but tobacco showed a decreased ability to metabolize the compound after 8 days in its presence. Because of the rates of uptake observed, and the metabolism of this compound, it is concluded that mannitol is not an ideal osmoticum for long‐term studies with any of these species, though its use in the short‐term remains valid.
Immunohistochemical localization of β‐amylase in resting barley seeds
Authors: Laurière Christiane , Laurière Michel , Daussant Jean
Published: April 2006

The cellular localization of β‐amylase (EC 3.2.1.2) in resting barley seeds was investigated by immunohistochemistry. The monospecificity of the antibodies used was shown by immunoelectrophoresis and western blotting. An adaptation of the immunofluorescence technique allowed the localization of β‐amylase. free of autofluorescence, in the different parts of the seed. In endosperm, there was β‐amylase protein in aleurone layers, only in the starchy endosperm, where the distribution of the enzyme was not uniform. The β‐amylase of starchy endosperm. which can be in a free or a hound form, was mainly localized around starch granules of different sizes. In the embryo. β‐amylase was present only in the part of the scutellum in front of the first leaf. By immunoquantitation after separation of the seed parts, its was shown that the ratio between the amounts of enzyme in embryo and endosperm was less than 1/3000.
Monocarpic senescence in wheat: Influence of sterile glumes and ear
Authors: Biswas A. K. , Mandal S. K.
Published: April 2006

The senescence of sterile glumes, flag leaf and the other two leaves below the ear of wheat (Triticum aestivum L. cv. Sonalika) was studied in relation to grain development and surgical manipulation. The senescence of sterile glumes was faster than that of the leaves in terms of chlorophyll and protein degradation. The flag leaf senesced later than the other two leaves below it. Removal of sterile glumes markedly reduced the harvest index (crop: straw ratio) and average dry weight per grain as compared to removal of the flag leaf. Maximum grain weight was achieved after the glumes had senesced completely. Removal of the ear delayed senescence of all the three leaves. It is concluded that sterile glumes are important suppliers of assimilate for grain filling and that nutrient drainage is the primary cause of the monocarpic senescence in wheat.
Effect of a free radical scavenger, 3,4,5‐trichlorophenol, on ethylene production and on changes in lipids and membrane integrity during senescence of petals of cut carnations (Dianthus caryophyllus)
Authors: Paulin A. , Droillard M. J. , Bureau J. M.
Published: April 2006

Three free radical scavengers were tested: sodium benzoate, propyl gallate and 3,4,5‐trichlorophenol. One of the compounds, namely 3,4,5‐trichlorophenol, was capable of prolonging the vase‐life of carnations (Dianthus caryophylius L. cv. Ember). A delay in the appearance and a much lower intensity of the ethylene peak were associated with this positive effect on the morphology. Also the loss of membrane integrity, the breakdown of fatty acids of polar lipids and the massive production of peroxides occurred much later after treatment with 3,4,5‐trichlorophenol than in the controls. Free radicals thus appear involved in the process of ageing in carnation petals, where they affect ethylene synthesis and where their action on lipids leads to the loss of membrane integrity. It is suggested that the peroxidation plays a fundamental role and that ethylene appears as a by‐product of the senescence process rather than an initiating factor.
Effects of norflurazon, an inhibitor of carotenogenesis, on abscisic acid and xanthoxin in the caps of gravistimulated maize roots
Authors: Feldman Lewis J. , Sun Piera S.
Published: April 2006

Maize seeds were germinated in the dark in the presence of the carotenoid synthesis inhibitor norflurazon and the teveis of abscisic acid, xanthoxin and total carotenoids were measured in the root cap and in the adjacent 1.5 mm segment. In norflurazon‐treated roots abscisic acid levels were markedly reduced, but an increase occurred in the levels of xanthoxin, a compound structurally and physiologically similar to abscisic acid. In the cultivar of maize (Zea mays L. cv. Merit) used for this work, brief illumination of the root is required for gravitropic curving. Following illumination both control and norflurazon‐treated roots showed normal gravitropic curvature, however, the rate of curvature was delayed in norflurazon‐treated roots. Our data from norflurazon‐treated roots are consistent with a role for xanthoxin in maize root gravitropism. The increase in xanthoxin in the presence of an inhibitor of carotenoid synthesis suggests that xanthoxin and abscisic acid originate, at least in part, via different metabolic pathways.
Growth, dry matter partitioning, and diurnal activities of RuBP carboxylase in citrus seedlings maintained at two levels of CO2
Authors: Koch Karen E. , Jones Pierce H. , Avigne Wayne T. , Allen L. Hartwell
Published: April 2006

The long‐term response of citrus rootstock seedlings to CO2 enrichment was examined in Carrizo estrange (Poncirua trifoliata (L.) Raf. x Citrus sinensis (L.) Osbeck] and Swingle citrumelo (P. trifoliate x C. parodist Macf.]. Plaotlets 14 weeks old were transferred to outdoor controlled‐environment chambers and maintained for 5 months from Feb. 14 to July 21. During this period, new growth (cm) of citrange and citrumelo shoots at 660 μl1−1 was 94 and 69% greater, respectively, than at 330 μ1 1−1. Total dry weight of both rootstock shoots had increased by over 100%. Growth of few species is affected this markedly by elevated CO2 levels.

More carbon was partitioned to above‐ground organs in CO2‐enriched citrus seedlings. Stem dry matter per unit length was also 32 and 44% greater in citrange and citrumelo, respectively. Total leaf area was increased by 124% in citrange and 85% in citrumelo due to greater leaf number and size. Variations in overall relative growth rate appeared to be related to the rapid, sequential, flush‐type growth in citrus, in which an entire shoot segment with its associated leaves remains an active sink until fully expanded. RuBP carboxylase (EC 4.1.1.39) activity in leaves of recently‐expanded flushes was higher in citrumelo plants grown at 660 vs 330 μ1 1−1 CO2 and changed diurnally for citrange (but not citrumelo) leaves at both CO2 levels. The results are consistent with the hypothesis that positive long‐term effects of CO2 enrichment may be greater in species or during growth periods where sink capacity for carbon utilization is high.
“Metallothionein‐like” metal complexes in angiosperms; their structure and function
Authors: Robinson N. J. , Jackson P. J.
Published: April 2006

Evidence for the presence of the metal‐binding protein metallothionein, MT, in higher plants is equivocal. Although a number of MT‐like metal complexes have been isolated from plants, the chemical structures of most of these compounds have not been fully elucidated. Recently a novel class of plant peptides, poly (γ‐glutamylcysteinyl) glycines, (γEC)nG, have been discovered. These peptides bind metal ions, and in the presence of such ions the amount of (γEC), G in plant cells increases. The presence of peptide bonds through the γ‐carboxyl group of glutamate, rather than the α‐carboxyl group, suggests that these peptides are not encoded by structural genes but are the products of biosynthetic pathways. Cells which are resistant to supra‐optimal concentrations of certain metal ions over‐produce (γEC)n G. (γEC)n G. may be functional analogues of MT. Whether or not some plants also produce MT is an important question which remains to be answered.
Effects of temperature and irradiance on non‐structural carbohydrate accumulation in barley primary leaves
Authors: Sicher Richard C. , Kremer Diane F.
Published: April 2006

Non‐structural storage carbohydrates were measured in 9‐day‐old barley (Hordeum vulgare L. cv. Brant) primary leaves. Accumulation rates of starch, sucrose and total non‐structural carbohydrates (TNC) were approximately linear when measured between 2‐ and 12‐h of light. Progressively higher TNC accumulation rates were observed at higher irradiance levels (i.e., comparing 250, 550 and 1050 ·mol m−2 s−1). Synthesis of a low‐molecular‐weight fructan also was enhanced by high irradiances. Low irradiance treatments decreased leaf sucrose levels and there was a corresponding increase in the lag period preceding starch synthesis in the light. Increased starch accumulation rates were usually observed when sucrose concentrations were high. These and other results suggested that cytosolic sucrose concentrations affected starch metabolism in the chloroplast. However, sucrose accumulation rates increased and starch storage decreased when barley seedlings were transferred from 20 to 10°C during the light period. Lowering the night temperature from 20 to 10°C for a single dark period 8‐days after planting increased the TNC content of barley primary leaves at the beginning of day nine. In this experiment, TNC accumulation rates of treated and untreated leaves were similar. Changes in the accumulation rate of TNC were usually observed within 2‐ to 4‐h after barley seedlings were exposed to altered environmental conditions. Monitoring rapid changes in leaf carbohydrate levels is a sensitive method for assessing the effects of environmental treatments on photosynthetic metabolism.
Water stress induced cavitation and embolism in some woody plants
Authors: Tyree Melvin T. , Dixon Michael A.
Published: April 2006

A comparison was made of the relative vulnerability of xylem conduits to cavitation and embolism in three species [Thuja occidentalis L., Tsuga canadensis (L.) Carr. and Acer saccharum Marsh.]. Waterlogged samples of wood were air dehydrated while measuring relative water loss, loss of hydraulic conductance, cumulative acoustic emissions (= cavitations) and xylem water potential. Most cavitation events and loss of hydraulic conductance occurred while water potential declined from – 1 to –6 MPa. There were differences in vulnerability between species. Other people have hypothesized that large xylem conduits (e.g. vessels) should be more vulnerable to cavitations than small conduits (e.g. tracheids). Our findings are contrary to this hypothesis. Under water stress, the vessel bearing wood retained water better than tracheid bearing wood. However, within a species large conduits were more prone to cavitation than small conduits.
Identification of abscisic acid from shoots of Salix pentandra
Authors: Jensen Einar , Rivier Laurent , Junttila Olavi , Crozier Alan
Published: April 2006

Abscisic acid isolated from vegetative shoots of Salix pentandra L. has been identified by high performance liquid chromatography and combined gas chromatography‐mass spectrometry.
Metabolism of 1‐aminocyclopropane‐1‐carboxylic acid in ripening apple fruits
Authors: Mansour Raad , Latché Alain , Vaillant Virginie , Pech Jean‐Claude , Reid Michael S.
Published: April 2006

In preclimacteric apple fruits (Malus × domestica Borkh. cv. Golden Delicious) ethylene production is controlled by the rates of 1‐aminocyclopropane‐1‐carboxylic acid (ACC) synthesis, and by its metabolism to ethylene by the ethylene‐forming enzyme and to 1‐(malonylamino)cyclopropane‐1‐carboxylic acid (MACC) by malonyl CoA‐ACC transferase. The onset of the climacteric in ethylene production is associated with an increase in the activity of the ethylene‐forming enzyme in the pulp and with a rise in the activity of ACC synthase. Malonyl transferase activity is very high in the skin of immature fruit, decreases sharply before the onset of the climacteric, and remains nearly constant thereafter. More than 40% of the ACC synthesized in the skin and around 5% in the flesh, are diverted to MACC at early climacteric. At the climacteric peak there are substantial gradients in ethylene production between different portions of the tissue, the inner cortical tissues producing up to twice as much as the external tissues. This increased production is associated with, and apparently due to, increased content of ACC synthase. Less than 1% of the synthesized ACC is diverted to MACC in the flesh of climacteric apples. In contrast, the skin contains high activity of malonyl transferase, and correspondingly high levels [1000 nmol (g dry weight)−1] of MACC.
Characterisation of grain yield and nitrogen level in relation to flag leaf senescence of wheat varieties
Authors: Martín del Molino I. Ma. , Ulloa M. , Martínez‐Carrasco R. , Pérez P.
Published: April 2006

Three wheat cultivars (Triticum aestivum L.), Splendeur, Hobbit and Maris Huntsman grown in pots were compared. Especially when compared to Splendeur, the flag leaf senesced most rapidly in Maris Huntsman, which presented the most rapid loss of moisture, chlorophyll and nitrogen. The uptake of exogenous nitrogen during the post‐anthesis period was lower in the rapidly than in the slowly senescing variety. A higher concentration of free amino nitrogen in the flag leaf at a given sampling date was associated with a lower percentage decrease of soluble proteins at the following date. Acid proteinase activity in the flag leaf was inversely related to moisture percentage and free amino nitrogen level, but unrelated to the nitrogen loss of the flag leaf. Acid proteinase activity in the flag leaf was directly related to grain nitrogen percentage, but inversely related to grain yield. Grain yield was also directly related to the mean soluble protein content of the flag leaf through senescence.
Distribution of indole‐3‐acetic acid in relation to the growth of etiolated Lupinus albus hypocotyls
Authors: Sánchez‐Bravo J. , Ortuño A. , Acosta M. , Sabater F.
Published: April 2006

The free indole‐3‐acetic acid (IAA) in methanolic extracts of etiolated hypocotyls of lupin (Lupinus albus L., from Bari, Italy) was determined by fluorimetry. The distribution of IAA along the hypocotyls was parallel to the growth, but when growth ceased oscillations occurred in the auxin level. These oscillations could be related to processes of differentiation mediated by IAA. The oscillations did not obey any impulses from the apex, since the application of [1‐14C]‐IAA to decapitated plants gives a distribution of radioactivity which also presents an undulatory pattern. Our results support the hypothesis that morphogenesis can be regulated by information transmitted by the translocation of waves of auxin.
Inhibition of flowering in vivo by existing fruits and applied growth regulators in Citrus unshiu
Authors: Garcia‐Luis A. , Almela V. , Monerri C. , Agustí M. , Guardiola J. L.
Published: April 2006

In the Satsuma mandarin (Citrus unshiu Marc.) the presence of the fruit results in a gradual inhibition of flowering and of bud sprouting. This inhibitory effect starts several months before the onset of the winter rest period and lasts until the end of the accumulation of carotenoids in the fruit peel, more than one month after the completion of fruit growth. During all this time and until natural bud sprouting, flowering and bud sprouting are inhibited by exogenous gibberellic acid. Peak responses to this growth regulator coincide with periods of maximal rates of flowering inhibition by the fruit. Kinetin and abscisic acid, applied at the time of peak response to gibberellic acid, inhibited flowering and reduced the number of shoots developed through the reduction of the number of shoots formed per sprouted node, but failed to reduce the number of nodes which sprouted. The same pattern of sprouting was obtained in trees treated with gibberellic acid during the winter rest period or several months earlier. It is concluded that some step leading to flowering and which determines the differences in sensitivity of the buds to this growth regulator has taken place already at this early date.
Non‐stomatal limitation of CO2 assimilation in three tree species during natural drought conditions
Authors: Briggs G. M. , Jurik T. W. , Gates D. M.
Published: April 2006

The effect of drought on CO2 assimilation and leaf conductance was studied in three northern hardwood species: Quercus rubra L., Acer rubrum L. and Populus grandidentata Michx. Leaf gas exchange characteristics at two CO2 levels (320 and 620 μl I−1) and temperatures from 20 to 35°C were measured at the end of a dry period and shortly after 10 cm of rainfall. The effects of drought varied with species, temperature and CO2 level. Calculated values of internal CO2 concentration showed little or no decline during drought. Differences in assimilation, before vs after the rains, were most apparent at the higher CO2 level. These latter two observations indicate nonstomatal disruption of CO2 assimilation during the dry period. In P. grandidentata there was a substantial interaction between drought and temperature, with a resultant shift in the temperature for maximum assimilation to lower temperatures during drought. During drought, internal CO2 concentrations increased sharply in all three species under the combined conditions of high temperatures and the higher CO2 level.
Rhythmicity of L‐phenylalanine ammonia‐lyase activity in Spirodela oligorrhiza. Effects of darkening, abscisic acid and 1‐amino‐2‐phenylethylphosphonic acid
Authors: Knypl J. S. , Janas Krystyna M. , Wolska Malgorzata
Published: April 2006

L‐Phenylalanine ammonia‐lyase (PAL; EC 4.3.1.5) in Spirodela oligorrhiza (Kurz) Hegelm. cultivated in continuous light showed ca 48‐h rhythmicity in the activity. Abscisic acid shifted the oscillation by ca 24 h. 1‐Amino‐2‐phenylethylphosphonic acid, a competitive inhibitor of the enzyme in vitro, markedly increased PAL activity in vivo and nullified the oscillation. Rhythmicity in PAL activity did not occur in darkness. Illumination was a prerequisite for maintaining high PAL activity as well as for the occurrence of the oscillations in the enzyme activity. ‘Average’enzyme activity decreased proportionally to time of cultivation of plants in the stationary culture. Transfer of the plants to fresh medium was connected with the increase of PAL activity to a maximum during the following 1‐2 days. Diurnal oscillation of PAL activity with a maximum at 1800–1900 h, dependent on the presence of glucose or sucrose in the nutrient medium, was also recorded.
The effect of isoproturon on root growth and ultrastructure of the photosynthetic apparatus of two wheat cultivars and a weed
Authors: De Felipe M. R. , Pozuelo J. M. , Lucas M. M. , Fernández del Campo F.
Published: April 2006

The effect of isoproturon [N,N‐dimethyl N′4‐(1‐methyl‐ethyl) phenyl urea] on the germination, growth of root and ultrastructure of the photosynthetic apparatus was investigated in two wheat cultivars (Triticum sativum L. cvs Castan and Esquilache) and a weed (Lolium rigidum Gaud.). No inhibition of germination was apparent in any of the three plants studied. The inhibition of root growth was considerably significant, especially in cv. Esquilache. After 48 h treatment with isoproturon (340 μM), the chloroplasts of the two wheat cultivars were found to be similar, showing a higher number of grana with fewer thylakoids per granum (lower stacking degree), broader grana stacks than in the control and an absence of starch. However, after 60 h of treatment, swelling of the thylakoids occurred in the Esquilache cultivar.

The rye grass was the most affected by the herbicide; at low concentration (3.4 μM) the number and size of the grana decreased considerably and the stroma thylakoids were destroyed. At higher concentration (17 μM), there was a strong accumulation in certain areas of the stroma of a substance with a lipid‐like appearance, probably derived from the disintegrating thylakoids. At the same concentrations some chloroplast envelopes were completely desintegrated.

The Hill reaction of the three plants exhibited a similar sensitivity towards the herbicide.
Respiration, cyanide‐insensitive oxygen uptake and oxidative phosphorylation in cyanobacteria
Authors: Scherer Siegfried , Häfele Ursula , Krüger Gert H. J. , Böger Peter
Published: April 2006

Cyanide‐insensitive oxygen uptake in the dark of 9 species of cyanobacteria was 6–20% of the total oxygen uptake of intact cells. In Phormidium, no cyanideinsensitive oxygen uptake was observed. In intact cells, the I50 value for cyanide was significantly lower in cyanobacteria of the taxonomic sections I to III (1–9 μM) than in those from section IV and V (10–60 μM). Cyanide‐insensitive oxygen uptake in the cell‐free system of Anabaena variabilis was not affected by typical inhibitors of the alternative pathway of plants. Cell‐free oxidation of cytochrome c was completely inhibited by cyanide with an I50 value of 0.5–1 μM. Electron transport of intact cells without cyanide present yielded P/O ratios of 0.7–3.0. The data on oxidative phosphorylation using intact cells and the cell‐free system, indicate that cyanide‐insensitive oxygen uptake is not coupled to ATP formation.
Physiological significance of the binding of acidic isoperoxidases to cell walls of lupin
Authors: Barceló Alfonso Ros , Pedreño M. Angeles , Muñoz Romualdo , Sabater Francisco
Published: April 2006

Intercellular acidic isoperoxidases (EC 1.11.1.7) isolated from exponentially growing lupin (Lupinus albus. L. cv. multolupa) hypocotyls are under the control of exogenously applied auxins. Application of auxins leads to a short‐term reduction in the level of free intercellular peroxidases, and this effect is associated with a binding of these free peroxidases to the cell walls, probably mediated by an acidification of the cell wall. The ratio of free intercellular peroxidases to the total intercellular peroxidase activity, varies along the axis of exponentially growing hypocotyls. It has a V‐shaped distribution with the minimum value in the elongation III‐zone, where high levels of auxins have previously been implied in differentiation. This minimum value coincides spatially with the first signs of cell wall thickening in the hypocotyl cells and, paradoxically, it is out of phase with respect to the maximal cell elongation. On the other hand, the ratio of free intercellular peroxidases reaches its maximal values in both the most undiffercntiated phloem cells and the differentiated xylem cells. High levels of free intercellular peroxidase activity in phloem cells are hard to explain, since phloem cell walls remain unlignified during almost all stages of differentiation. However, association of free intercellular peroxidase activity with xylem cells is clearly associated with the lignification of the xylem cell walls. The physiological significance of the binding vs release of intercellular peroxidase is discussed in relation to the catalytic properties and stability at acidic pH of both the bound and free forms of this enzyme.
Dependence of amino acid composition upon nitrogen availability in birch (Betula pendula)
Authors: Näsholm Torgny , McDonald A. James S.
Published: April 2006

Small birch plants (Betula pendula Roth.) were grown at different rates of exponentially increasing nitrogen supply. This resulted in plants with different relative growth rates and different internal nitrogen concentrations. Within a nitrogen treatment, both of these variables remained constant with time.

Free amino acids were measured in leaves and roots of the seedlings at two different harvests. At greater nitrogen supply, higher concentrations of total amino acid nitrogen were found in roots and leaves. The ratio of amino acid nitrogen to total nitrogen was low albeit greater at higher nitrogen supply. Higher concentrations of amino acid nitrogen were mainly due to high concentrations of citrulline, glutamine, γ‐aminobuitric acid and arginine.

Greater leaf concentrations of amino acid nitrogen at higher nitrogen supply may be related lo increased concentrations in the xylem sap and/or may be indicative of small excesses of nitrogen with respect to current nitrogen usage in protein synthesis.
Yield and Yield Stability in a Balanced System of Widely Differing Population Structures in Zea Mays L.
Authors: Schnell F. W. , Becker H. C.
Published: April 2006

With the view to study heterozygosity and heterogeneity as to their effects and interactions on yield and yield stability in maize, the following four types of population structure were formed from eight inbred lines: Homogeneous populations of homozygous plants (the eight inbred lines themselves); heterogeneous populations of homozygous plants (four blends containing four lines each); homogeneous populations of heterozygous plants (16 single crosses); heterogeneous populations of heterozygous plants (four blends containing four single crosses each, and four double crosses). This material was grown in three environments (years).

At both levels of heterozygosity, the blends did not outyield the means of their respective components grown in pure stands. yield stability of the various structural groups was ranked differently by ecovalence and the mean square for deviations from regression. By transforming the deviation mean squares into coefficients of variation it was possible to reveal improvements of stability not only by heterogeneity but also by heterozygosity, and additionally, an interaction of both factors in the sense of a diminishing return.
Inheritance of Partial Male‐Sterility in Guar
Authors: Stafford R. E.
Published: April 2006

A partial male‐sterility system was found in a released guar, Cyamopsis tetragonoloba (L.) Taub. (2n = 2x = 14), breeding line, TX76‐3285. Partially male‐sterile plants produce some functional pollen, but with suitable genetic markers may be used to facilitate crossing in breeding programs. In addition, self fertilization allows partially male‐sterile plants to be propagated sexually as homozygotes, once placed in breeding lines. The objective of the present study was to determine the inheritance of a partial male‐sterility system in guar. Partial male‐sterility appeared to be controlled by two genes, with one gene acting in a dominant epistatic manner and the second gene by incomplete dominance. The trait was expressed on every raceme beginning at about 4 to 6 weeks after planting in field‐grown plants. The gene symbols, “pms1” and “Pms2” are proposed for the new trait. Segregation data indicated that alleles for pubescence segregated independently of alleles for partial male‐sterility. Partial male‐sterility in guar may be useful in the production of hybrid seed for breeding and genetic research.
The Experimental and Commercial Release of Transgenic Crop Plants
Authors: Dale P. J. , Irwin J. A. , Scheffler J. A.
Published: April 2006

With advances in recombinant DNA methods and transformation procedures, it is possible to transfer genes into crop plants from unrelated plants, microbes and animals. Many of the modifications being carried out, or envisaged, are for disease and pest resistance, product quality and tolerance to environmental stress, but there are additional opportunities to modify crops to give specialized products for industrial or pharmaceutical use. Some of the characteristics of transgenic plants are considered, including: transgene copy number, position, expression, stability, pleiotropy, selectable marker genes and somaclonal variation. There have been several hundreds of field trials with transgenic plants, and the first transgenic varieties are likely to be approved for commercial production in 1993. Before releasing transgenic plants, it is necessary to carry out a risk assessment to determine whether the transgenic variety will behave differently from a conventionally bred variety. Assessment procedures are being harmonized internationally by various organizations. There is a growing commitment to apply these genetic modification methods to crops in developing countries, as genes relevant to their crops and environments become available.
The Inheritance of Aliphatic Glucosinolates in Brassica napus
Authors: Magrath R. , Herron C. , Giamoustaris A. , Mithen R.
Published: April 2006

The inheritance of aliphatic glucosinolates was studied in crosses between synthetic B. napus lines and oilseed rape cultivars. Six unlinked loci are described which determine the aliphatic glucosinolate profile of B. napus. One locus regulates the presence or absence of propyl glucosinolates, while another regulates the expression of pentyl glucosinolates. Two loci regulate the removal of the terminal H3CS‐group from the amino acid derivative to produce alkenyl glucosinolates as opposed to methylthioalkyl and methylsulphinylalkyl glucosinolates, regardless of the length of the alkyl chain. Likewise, another two loci regulate the hydroxylation of both butenyl and pentenyl glucosinolates. The functional alleles at one of the hydroxylation loci results in significantly more hydroxylation than those at the other locus. The large number of aliphatic glucosinolates which have been described in Brassica thus results from an interaction between genes which regulate side chain elongation and genes which modify the structure of the side chain, regardless of its length. The implications of this study for the biosynthesis of aliphatic glucosinolates, the origin of B. napus and the potential to manipulate the leaf and seed glucosinolate profile of oilseed rape are discussed.
Genetic Structure of Three Open‐Pollinated Faba Bean Varieties (Vicia faba L.)*
Authors: Ebmeyer E. , Stelling D.
Published: April 2006

To study the genetic structure of open‐pollinated faba bean varieties, three sets of genotypes were generated from each of the varieties ‘Minica’, ‘Kristall’, and ‘Deiniol’: (1) inbred lines developed by single‐seed descent in bee‐proof isolation cages, (2) intravanetal and (3) intervarietal F1‐hybrids produced by controlled hand crossing. In 1989 and 1990, a total of 144 entries, including the three open‐pollinated source varieties, were grown in single‐row plots with two replications at two locations in Western Germany.

Performance data of the inbred lines revealed relatively large genotypic variability within each variety, for all the characters studied, which was greater in ‘Deiniol’ and ‘Kristall’ than in ‘Minica’. An average yield heterosis of 20 %, 39 % and 57 %, respectively, was found for the intravarietal hybrids, whereas that of the intervarietal hybrids varied between 70 and 73 %. Compared to the mean yield of the inbred lines the superiority of the open‐pollinated source variety was small and not significant in ‘Minica’ (6 %), but it was large and highly significant in ‘Kristall’ (22 %) and ‘Deiniol’ (37 %).

The present investigation revealed in faba bean that similar performance levels of open‐pollinated varieties may result from either high per se performance under inbreeding with low heterosis values or from lower per se performance but with high heterosis values.
Yield Stability in Faba Bean, Vicia faba L. 2. Effects of Heterozygosity and Heterogeneity*
Authors: Stelling D. , Ebmeyer E. , Link W.
Published: April 2006

In order to evaluate the effects of heterogeneity and heterozygosity on yield stability in faba beans, genotypes were generated with contrasting population structures, differing only in their levels of heterogeneity and heterozygosity. All entries were based on either eight or 36 inbred lines, respectively. The population structures tested consisted of pure stands of the inbred lines (1) and of their F1,‐hybrids (2), blends of the inbred lines (3) and of their F1 hybrids (4), four‐component synthetics in different Syngenerations (5), the open‐pollinated source varieties (6) and 36 polycross progenies (7). Five different entry sets (= data sets), each covering several of the seven population structures listed, were grown during 1986 to 1991 in at least four different environments in Western Germany and tested for yield.

Stability parameters, i.e., the regression coefficient and deviation from regression (EBERHART and RUSSELL 1966), and the ecovalence (WRICKE 1962), revealed that yield stability of the different population structures was improved by increasing heterozygosity as well as heterogeneity. But the impact of both factors of diversity on yield stability varied between the different data sets. Positive effects of both factors on yield stability seemed to be additively combined in the hybrid blends (data set I). The same proved to be partly true for the four different Syn‐generations of the nine synthetics tested. Yield advantage of the different heterozygous variety structures over the homozygous ones in creased with increasing yield level at test sites, as indicated by regression coefficients larger than 1.
Selection for Yield and its Components in a Winter Wheat Population under Different Environmental Conditions in Albania
Authors: Collaku A.
Published: April 2006

Wheat breeding programmes in Albania depend upon the use of diverse genetic material of local origin and on special environmental conditions; the present study being conducted under drought stress conditions. Grain yield, yield components, plant height and test weight were estimated in an F5 generation of a winter wheat population at Kamez in 1989—90 and 1990—91 and at Lushnje in 1989—90. The highest values of heritability were observed for plant height, kernel weight and spike length. Due to drought stress the heritability of kernels per spike was low. None of the correlated responses was higher than the direct response for yield. Maximum genetic gain was expected when yield, plant height, spike length, kernels/spike and kernel weight were included in the index.
The Effect of the “D” Genome from Synthetic Wheat Lines in Anther Culture Responses
Authors: Ghaemi M. , Sarrafi A.
Published: April 2006

Synthetic lines of wheat were compared in order to determine the effect of the “D” genome on embryo induction and plant regeneration from anther culture. The experiments were performed using 6 genotypes of wheat in a randomized block design with 4 replications.

In all cases except one, addition of the “D” genome from T. tauschii increased the efficiency of embryo formation and green plantlet production. This positive effect of the “D” genome does not exclude the existence of possible interactions between the three genomes (A, B and D) and/or the effect of each genome separately.
Some remarks on carrot breeding (Daucus carota sativus Hoffm.)
Authors: Stein M. , Nothnagel Th.
Published: April 2006

Carrot breeding in the past 150 years has resulted in varieties with high yield, a short growing period, and excellent root colour. Recently, hybrid varieties have demonstrated good uniformity of roots, a quality accepted by most consumers. By contrast, only a few resistant varieties (mainly open‐pollinated varieties) are offered by seed companies, most being resistant to Alternaria. Hybrid breeding offers a chance of combining good uniformity and different sources of resistance. Efforts in future breeding should concentrate on the improvement of health and the development of genotypes suitable for cultivation in suboptimal climates and regions, as well as for special applications.
Oligonucleotide fingerprinting of tomato DNA
Authors: Kaemmer D. , Weising K. , Beyermann B. , Börner T. , Epplen J. T. , Kahlm G.
Published: April 2006

Hinfl ‐digested DNA samples of wild and cultivated species of tomato were hybridized in gel to different oligonucleotide probes complementary to simple‐sequence repeats. All motifs tested i.e. (GATA)4, (GGAT)4, (CA)8. (CAG)5, (GTG)5, (GAAGTGGG)2 and (CCTA)4, produced multilocus fingerprints in all tomato species and cultivars. The extent of inter‐ and intraspecific polymorphism of the banding patterns varied considerably between different probes, with (GGAT)4, (CCTA)4, (GATA)4 and (CA)8 showing a much higher discriminatory potential than the other probes. Cluster analysis of band‐sharing data yielded dendrograms which were consistent with the known history of tomato cultivation. (GATA)4 was also successfully used for purity testing of breeding lines, as well as for analysing an F1 progeny of a cross between two lines.