bluuebunny/crossref_metadata_2025_split huggingface dataset:
Induction and release of secondary seed dormancy in genetically pure lines of Avena fatua
Authors: Tilsner Heidy R. , Upadhyaya Mahesh K. 
Published: April 2006

Induction and release of secondary dormancy in genetically pure dormant (AN‐51, Mont 73) and non‐dormant (CS‐40, SH‐430) lines of wild oat (Avena fatua L.) were studied. These lines differed with regard to the optimal period of anaerobiosis necessary for induction of dormancy, and/or the degree (% of seeds acquiring dormancy) and duration of the dormancy induced. Secondary dormancy could be induced more effectively in the after‐ripened seeds of dormant lines than in the non‐dormant lines, where only a short‐term dormancy could be induced (in 5–7 week‐old‐seeds). Higher anaerobiosis temperatures were more effective in inducing dormancy in all lines studied. Thus, as with primary dormancy, wild oat biotypes exhibit genetic variability in their secondary dormancy behaviour and factors like temperature can modify the expression of this trait.The germination stimulants kinetin, isopentenyl adenine, sodium azide, potassium nitrate, ethanol and substituted phthalimides, which break primary dormancy in wild oats, stimulated germination of secondarily dormant seeds (line AN‐51). Since these chemicals are structurally diverse, primary and secondary dormancies appear to be similar in part in their regulation.Salicylhydroxamic acid, an inhibitor of cyanide‐insensitive (alternative) respiration, did not inhibit: 1, spontaneous release of secondary dormancy in the line SH‐430; and 2, stimulation of germination of secondarily dormant AN‐51 seeds by various chemicals (except azide), suggesting that this respiratory pathway is not necessary for the release of induced dormancy.
Initiation and development of wound tissue and roots on hypocotyl cuttings of Pinus sylvestris in vitro
Authors: Grönroos Roland , von Arnold Sara 
Published: April 2006

The rooting of hypocotyl cuttings from 20‐day‐old seedlings of Pinus sylvestris L. cultured in vitro is discussed. About 40% of the cuttings cultured on medium lacking activated charcoal produced roots during the first two months. When activated charcoal was added to the medium, either root formation (75% formed roots) or wound tissue growth (95% formed large wound tissues) was stimulated in different experiments. These large wound tissues did not develop any roots. The anatomical changes in the basal part of the cuttings were similar during the first two weeks in all the cuttings studied. A vascular cylinder composed of short tracheids with many pores developed. Thereafter the differentiation process became varied. The amount of wound tissue produced and the time for rooting differed among the cuttings. Tracheid nests which were in contact with the vascular system in the hypocotyl via short tracheids were observed after three weeks. Subsequently, roots developed from the tracheid nests. The longer root formation was delayed, the larger the wound tissue became.Short tracheids were found close to the wound tissue surface. Their ability to adsorb nutrients and water is discussed.
Hardening, abscisic acid, proline and freezing resistance in two winter wheat varieties
Authors: Lalk Irmtraut , Dörffling Karl 
Published: April 2006

Two varieties of winter wheat (Triticum aestivum L.) differing in freezing resistance (“Holme” from Sweden, freezing resistant, and “Amandus” from Germany, less freezing resistant) were hardened for five weeks by gradually reducing the day/night temperature from 20°C/15°C during the first week to 2° C/0° C during the fifth week and the photoperiod from 15 to 9 h. This treatment increased the freezing resistance of both varieties in comparison to unhardened control plants. Hardening caused an increase in osmolarity of cell sap and in the levels of proline and abscisic acid (ABA). Increase in osmolarity preceded the increase in ABA level, and proline levels increased later than ABA levels. Holme had higher values of osmolarity as well as higher levels of ABA and proline. but the differences between the two varieties were significant only for proline. Since the pressure potential remained constant or increased slightly during the hardening period, it is suggested that the accumulation of ABA is due to the hardening process and not to simple water stress caused by cold‐induced inhibition of water uptake by the root.Spraying hardened plants with 10−4 M ABA 24 h before a freezing test increased freezing resistance in both varieties, but did not obliterate the differences in freezing resistance between the two varieties. Spraying hardened plants with an aqueous proline solution (10%, w/v) was without effect on freezing resistance. It is concluded that the hardening procedure causes an accumulation of ABA in winter wheat leaves and that ABA is involved in the chain of events leading to freezing resistance.
Dual effect of 2, 4‐D on ethylene production and ripening of tomato fruit tissue
Authors: Vendrell Miguel 
Published: April 2006

Tomato fruits (Lycopersicon esculentum Mill. cv. Indian River) were treated with aqueous solutions of 2, 4‐dichlorophenoxyacetic acid (2, 4‐D) and the effects on respiration, ethylene production, and ripening were examined. 10‐3 and 10‐5M 2, 4‐D solutions were used. Dipping treatment of whole fruit picked at the 74% stage of development, gave an increase in respiration and ethylene production, the effect being directly related to 2, 4‐D concentration. Ripening was advanced relative to control fruit.Tomato disks cut from the pericarp tissue of fruit picked at the 81% stage of development were vacuum‐infiltrated with the same 2, 4‐D solutions. In these disks the increase in respiration continued longer compared to control disks. Ethylene production was considerably increased, and after an initial recovery the 2, 4‐D‐treated disks showed another increase at a much faster rate than controls. However, contrary to what could be expected from this increase in ethylene, ripening was delayed. Nevertheless, all disk samples showed advance ripening compared to whole fruit of the same age, indicating that they could not recover completely from the effect of cutting and treatment.The results showed that 2, 4‐D causes a dual effect in tomato fruit tissue: an increase in ethylene production which promotes ripening, and a delay in ripening. This last effect, depending on the uniformity of the auxin distribution and its concentration, prevails.
Enzymes of assimilatory sulfate reduction in leaves of Pisum sativum: Activity changes during ontogeny and in vivo regulation by H2S and cyst(e)ine
Authors: von Arb Christoph , Brunold Christian 
Published: April 2006

Enzyme activities of assimilatory sulfate reduction were measured in leaves of Pisum sativum L., cv. Vatters Frühbusch, during their ontogenetic development, and during treatment with H2S and cyst(e)ine. Ribulose bisphosphate (RuBP) carboxylase (EC 4.1.1.39) and ferredoxin‐dependent nitrite reductase (Fd‐NiR, EC 1.7.7.1) were measured for comparison. In etiolated pea leaves, ATP‐sulfurylase (ATPase, EC 2.7.7.4), adenosine 5′‐phosphosulfate sulfotransferase (APSSTase), ferredoxin‐dependent sulfite reductase (Fd‐SiR, EC 1.8.7.1) and O‐acetyl‐L‐serine sulfhydrylase (OASSase, EC 4.2.99.8) activities were measured in appreciable rates, while neither RuBP carboxylase nor Fd‐NiR activities could be detected.During the first 2–7 days after transfer into the light all enzyme activities increased. After reaching maximal activities, ATPase, APSSTase, and Fd‐SiR activities decreased in all leaves to low or indetectable levels during the following 3–6 days. RuBP carboxylase, Fd‐NiR and OASSase, on the other hand, decreased slowly and were still at high levels of activity at the end of the experiment.Fumigation of pea plants with 1.5 μl l−1 H2S delayed the initial increase and the subsequent decrease of ATPase activity by 1–3 days. APSSTase activity decreased for 1–2 days, increased rapidly during the next 4–6 days and retained a high level of activity until the end of the experiment as did Fd‐SiR. One to two days after the beginning of fumigation the leaves started to accumulate high amounts of cyst(e)ine.When pea plants with excised roots were placed on a nutrient solution containing cyst(e)ine, APSSTase activity decreased more on 0.2 and 0.5 mM than on 1.0 mM. Fd‐SiR activity was only slightly decreased on 1.0 mM cyst(e)ine. Neither Fd‐NiR nor RuBP carboxylase activities were affected.
The dynamics of the flavour precursors, the S‐alk(en)yl‐L‐cysteine sulphoxides, during leaf blade and scale development in the onion (Allium cepa)
Authors: Lancaster Jane E. , McCallion Barbara J. , Shaw Martin L. 
Published: April 2006

This study was undertaken to determine the patterns of accumulation and loss of the flavour precursors. (+) S‐1‐propyl‐L‐cysteine sulphoxide, (+) trans‐S‐1‐propenyl‐L‐cysteine sulphoxide, and (+) S‐1‐methyl‐L‐cysteine sulphoxide, during the development and senescence of the leaf blades and scales of a brown onion (Allium cepa L. cv. Pukekohe Longkeeper).The levels of the flavour precursors were related to the ontogeny of the individual leaf blade and scale, and the ontogeny of the entire plant. Leaf blades which developed on a young or bulbing onion contained all 3 flavour precursors (total of about 50–70 mg leaf−1); but as each attached scale developed, the leaf blades lost their flavour precursors. All 3 flavour precursors increased in the developing scales and decreased in the senescing scales. Leaf blades which developed on an older, ripening onion contained, and then lost, only (+) S‐1‐propyl‐L‐cysteine sulphoxide, whilst the scales accumulated only (+) S‐1‐propyl‐L‐cysteine sulphoxide; (+) S‐1‐methyl‐L‐cysteine sulphoxide and (+) trans‐S‐1‐propenyl‐L‐cysteine sulphoxide were minimal. In the main scales of the onion, which did not senesce during ripening, there was a transition between these two patterns. These scales accumulated all 3 flavour precursors with (+) S‐1‐propyl‐L‐cysteine sulphoxide remaining constant at about 30 mg/scale; however there was a 10 fold loss of the other 2 flavour precursors (from 20 to about 2 mg/scale). The base plate (true stem) contained mainly (+) S‐1‐propyl‐L‐cysteine sulphoxide, which increased 5 fold in amount during bulbing. The other 2 flavour precursors were present at much lower levels.A recycling of flavour precursors is suggested, with the leaf blades supplying flavour precursors to scales, and in turn older senescing scales recycling their flavour precursors to developing younger scales.
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.
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.
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.
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.
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

AbstractWith 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

AbstractA 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

AbstractWith 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

AbstractThe 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.