bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nutrient requirements and stress response of Populus simonii and Paulownia tomentosa
Authors: Hui‐jun Jia , Ingestad Torsten 
Published: April 2006

The aim of this investigation was to estimate the optimum nutrient requirements and responses to low relative nutrient addition rates of seedlings of two important broadleaf tree species in China, Populus simonii Carr. and Paulownia tomentosa (Thunb.) Steud. In preliminary experiments the optimum nutrient proportions were estimated under high concentration conditions. The nutrients consumed were replaced by means of daily additions determined by pH and conductivity titrations without changing the nutrient solutions. A relatively high K level was needed in relation to nitrogen; higher than in birch or grey alder seedlings. To obtain a high relative growth rate, suitable proportions by weight were 100 N:70 K:14 P:7 Ca:7 Mg for the Populus seedlings and 100 N:75 K:20 P:8 Ca:9 Mg for the Paulownia seedlings.In studies of nutrient stress responses the relative nutrient addition rate was used as the treatment variable under low conductivity conditions. The responses and relationships were similar to those described for birch, grey alder and Salix. The relative addition rate, and there was also a strong linear regression between relative growth rate and nitrogen status. Relative growth rates were high and the maximum weight increase was about 19% day−1 in Populus and over 25% day−1 in Paulownia. The nitrogen productivity of Paulownia was very high, 0.26 g dry weight (g N)−1 h−1, and for Populus it was 0.16 g dry weight (g N)−1 h−1.
The composition of lipids and fatty acids determined at various stages of haploid and diploid generations in the fern Adiantum capillus‐veneris
Authors: Sato Naoki , Furuya Masaki 
Published: April 2006

The composition of lipids and fatty acids was determined at various developmental stages of gametophytes and sporophytes in the fern Adiantum capillus‐veneris L. When the lipid content was expressed per g fresh weight, triacylglycerol was a major reserve lipid in spores and remained the dominant lipid in the gametophytes up to the 15th day after germination, but it was a minor one in the pinnae of sporophytes. In contrast, triterpenoids were abundant in sporophytes but not detected in gametophytes. When the content of fatty acids was expressed in percentage of the total fatty acids, the content of arachidonic acid in phosphatidylcholine and linolenic acid in diacyglyceryltrimethylhomoserine and phosphatidylcholine was significantly higher in both pinnae and petioles of sporophtes than in gametophytes. Significant differences in fatty acid composition of phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol and triacylglycerol were also noted between gametophytes and pinnae of sporophytes. All these differences were attributed to the difference of generation rather than tissue differences or age.The content of monogalactosyldiacylglycerol, hexadecatrienoic acid in monogalactosyldiacylglycerol, and 3‐trans hexadecenoic acid in phosphatidylglycerol was higher in the pinnae of sporophytes than in gametophytes or in young leaves of sporophytes. Electron microscopy of the ultrastructure of chloroplasts indicated that the high content of these components was consistent with the development of chloroplasts in pinnae.
Are two photoreceptors involved in the flowering of a long‐day plant?
Authors: Tanada Takuma 
Published: April 2006

The effect of daylength extension with narrow spectral bands on the flowering of a long‐day plant, Brassica campestris L. cv. Ceres, was investigated to obtain clues to the identity of the photoreceptor involved. Extension of a 9 h photoperiod with 5 h of light pulses at various wavelengths resulted in maximal flowering occurring after irradiation at 710 nm, less at 730 nm, and none at 550, 660 and 750 nm. Flowering at 710 and 730 nm was negated by simultaneous exposures at 550 nm, but not at 660 nm. A short preirradiation at 660 nm enabled a following irradiation at 750 nm to induce flowering. This latter induction was prevented by 550 nm irradiation.Short flashes of light at 710 nm induced flowering that was negated by a following flash at 550 nm but not at 660 nm. The negation by 550 nm radiation was prevented by subsequent flashes at 710 nm, indicating photoreversibility. A flash at 660 nm enabled subsequent light flashes at 750 nm to initiate flowering that was reversed by a following 550 nm flash.From the results showing the necessity of red and far‐red lights, it is proposed that flowering in this long‐day plant is due to two photoreceptors ‐ one is phytochrome and the other an unknown pigment with far‐red, green photoreversible properties. By using fluence response data, it is deduced that the unidentified photoreceptor has weak absorption bands in the far‐red, but has a strong absorption band in the green. Flowering is induced when effects of red light absorbed by phytochrome interact with effects of far‐red light absorbed by the unidentified photoreceptor.
Effects of water stress on the water relations of Phaseolus vulgaris and the drought resistant Phaseolus acutifolius
Authors: Parsons Lawrence R. , Howe Teresa K. 
Published: April 2006

The tepary bean (Phaseolus acutifolius Gray var. latifolius), a drought resistant species, was compared under water stress conditions with the more drought susceptible P. vulgaris L. cvs Pinto and White Half Runner (WHR). In order to better understand the basis for the superior drought resistance of tepary, this study was designed to determine the relationships among leaf water potential, osmotic potential, turgor potential, and relative water content (RWC).Plants were prestressed by withholding irrigation water. These stress pretreatments changed the relation between leaf water potential and relative water content of both species so that prestressed plants had lower water potentials than controls at the same leaf RWC. Tepary had lower water potentials at given RWC levels than Pinto or WHR; this can account for part of the superior resistance of tepary. In all genotypes, prestressed plants maintained osmotic potentials approximately 0.2 MPa lower than controls. Tepary reached osmotic potentials that were significantly lower (0.15 to 0.25 MPa) than Pinto or WHR. Both control and prestressed tepary plants had 0.05 to 0.25 MPa more turgor than Pinto or WHR at RWC values between 65 and 80%. Both prestressed and control tepary plants had greater elasticity (a lower elastic modulus) than Pinto or WHR. This greater turgor of tepary at low RWC values could be caused by several factors including greater tissue elasticity, active accumulation of solutes, or greater solute concentration.Tepary had significantly lower osmotic potentials than the P. vulgaris cultivars, but there was little difference in osmotic potential between Pinto and WHR. Knowledge of differences in osmotic and turgor potentials among and within species could be useful in breeding for drought resistance in Phaseolus.
Effects of cold on CO2 exchange in winter rape leaves
Authors: Maciejewska Urszula , Tomczyk Jerzy , Kacperska Alina 
Published: April 2006

The influence of temperature on the CO2 exchange rates was investigated in winter rape plants (Brassica napus L. var. oleifera cv. Górczański) subjected to cold (2°C) pretreatment. After one or two days of cold pretreatment both photosynthesis and dark respiration still readily responded to changes in the temperature of measurement. Prolongation of plant exposure to cold caused not only a marked depression of photosynthesis but also photosynthesis became less temperature and light dependent. In contrast, prolonged cold pretreatment only slightly affected the sensitivity of dark respiration to temperature. In the cold‐pretreated plants the rate of dark respiration was higher that that in the untreated ones at comparable temperatures of measurement. To obtain a full reversion of the cold‐induced changes in photosynthesis and dark respiration rates the plants had to be exposed to higher (25°C) temperature for 3–7 days.It seems that low temperature brings about two types of effects in plants with regard to photosynthesis and respiration: a direct response consisting in the rapid and readily reversible reduction of both photosynthesis and respiration; and an indirect one which consists in long lasting modifications of photosynthesis and dark respiration rates and may be related to the cold‐induced changes in biochemical properties in photosynthetic and respiratory systems.
Flavonol content of guard cell and mesophyll cell protoplasts isolated from Vicia faba leaves
Authors: Weissenböck G. , Schnabl H. , Sachs G. , Elbert Chr. , Heller F.‐O. 
Published: April 2006

Guard cells of the lower epidermis of leaflets of Vicia faba L. cv. Weißkernige Hangdown contain several kaempferol 3,7‐O‐glycosides. This was demonstrated for the first time by the use of isolated, highly purified guard cell protoplasts for flavonol estimation and quantitation. From a total of ca 12 kaempferol glycosides, three were identified by comparative thin layer chromatography and high performance liquid chromatography as kaempferol 3‐O‐glucoside 7‐O‐rhamnoside (major component), 3‐O‐rhamnogalactoside 7‐O‐rhamnoside and 3,7‐O‐bisglucoside (minor components). On average, the total flavonol content was estimated to be 85 fmol protoplast−1. From comparative investigations including alkaline‐induced (green) fluorescence characteristics of flavonols and UV‐microscopical studies we suggest that kaempferol glycosides are present in guard cells and epidermal cells in similar quantities, and that these compounds are in the vacuole.By contrast, mesophyll protoplasts have a low flavonol content (one sixth that of guard cells). In spite of the different total flavonol contents, individual components of each cell‐type are the same. However, they show differences in their quantitative distribution.
Influence of osmotic stress on the respiration of potato tuber callus
Authors: van der Plas Linus H. W. , Wagner Marijke J. 
Published: April 2006

Potato tuber (Solanum tuberosum L. cv. Bintje) callus shows a decrease in fresh weight and an increase in dry weight upon transfer to nutrient medium supplemented with 0.3 or 0.5 M mannitol. The osmolarity of the intracellular fluid increases simultaneously. Probably mannitol is taken up from the medium till the osmolarity of the tissue is in equilibrium with that of the medium. After osmotic adaptation, on a medium with 0.5 M mannitol, growth is negligible, although the tissue retains its viability.Respiration increases upon transfer to medium with extra mannitol, especially when expressed on a fresh weight basis. On this basis cytochrome and alternative pathway capacities do not change appreciably. The respiratory increase is exclusively caused by an increased engagement of the alternative pathway. The participation of this pathway in uninhibited respiration increases from about 10 to 90% upon transfer to medium with extra mannitol. The increase in respiration is partly correlated with the decrease in fresh weight upon transfer. Per disc, the capacities of the cytochrome and alternative pathway decline. Yet, total respiration per disc significantly increases due to the increased participation of the alternative pathway. This results in an almost equal ATP‐production per disc before and after transfer. We suggest, that the alternative pathway functions as a reserve capacity in potato callus, which is switched on when ATP‐production coupled to the cytochrome pathway is impaired.
Long distance transport of potassium in cereals during grain filling in detached ears
Authors: Haeder Hans‐Eckhard , Beringer Helmut 
Published: April 2006

Ears of wheat plants (Triticum aestivum L. cv. Kolibri), which were given different and uniform K+‐nutrition in two experiments, were cut at 2, 4 and 6 weeks after anthesis at 15 cm below the ear. These detached ears were fed 30 mM (experiment 1) or 15, 30, 60 or 90 mM86Rb‐K2 malate (experiment 2) and 146 mM [14C]‐sucrose. After a pulse period of 6 and 4 h, respectively, the ears were transferred to identical non‐labeled solutions for additional 0, 4, 8 or 20 h.About 50% of the K+ and sucrose supplied was absorbed by detached ears. This rate declined with plant age and decreasing transpiration. Within the 6 and 4 h uptake period less than 7% of the absorbed K+, but 20% of the sucrose taken up were incorporated into the grain. During the chase period labeled K+ in the grain increased to 15% and 14C even to 50% of total tracer uptake. Incorporation of labeled K+ into the grain was not affected by the previous K+ nutrition of the plant and was proportional to the K+ concentration in the uptake solution. Transition of K+ from xylem into phloem during its acropetal transport is assumed. No evidence was found that the grain itself could control its uptake of K+.
The growth and gravitropic responses of wild‐type and auxinresistant mutants of Arabidopsis thaliana
Authors: Mirza Javed I. , Olsen Gunn M. , Iversen Tor‐Henning , Maher E. Paddy 
Published: April 2006

Growth and gravitropism have been studied in three mutant strains of Arabidopsis thaliana L, that are resistant to auxin‐herbicide. Two of the mutations are allelic and recessive (aux‐1 and aux‐2) and are unlinked to a dominant mutation, Dwf, which confers a very high level of auxin‐resistance and is apparently lethal when homozygous. The aux‐1 and Dwf strains have altered response to gravity whereas aux‐2 appears to be gravitropically normal.After 96 h in the normal, vertical position only minor differences in elongation were observed between roots of wild‐type, aux‐1 and aux‐2, but the hypocotyls of aux‐1 were significantly retarded compared with the gravitropically normal aux‐2 and wild‐type. In the progeny of selfed Dwf plants, where both normal (dwf) and agravitropic (Dwf) seedlings are present, the Dwf seedlings had much longer roots and shorter hypocotyls than dwf+. During 22 h of continuous stimulation the optimum angle for gravitropism in wild‐type roots and hypocotyls was 135° (i.e. the organ points obliquely upwards), with decreasing responses in the order 90° and 45°. The agravitropic nature of the roots of aux‐1 was confirmed as no significant response was obtained at any of the stimulation angles. In marked contrast, the negative gravitropic response of aux‐1 hypocotyls was greater than the wild‐type response in terms of the final angle attained at 22 h, but between 6 and 22 h the elongation rate was lower in aux‐1. After varying stimulation periods in the horizontal position, the curvature which had developed, decreased rapidly and almost disappeared during ensuing rotation on clinostats (2 and 4 rpm). Rotation on the clinostats had no effect on the agravitropic behaviour of aux‐1.
Ultrastructure and movements of cell organelles in the root cap of agravitropic mutants and normal seedlings of Arabidopsis thaliana
Authors: Olsen Gunn M. , Mirza Javed I. , Maher E. Paddy , Iversen Tor‐Henning 
Published: April 2006

The root anatomy and ultrastructure of the agravitropic Arabidopsis thaliana L. mutants Dwf and aux‐1 were compared with the gravitropic mutant aux‐2 and the wild type (WT) in an attempt to find an explanation for the lack of response to gravity. No differences were found in the organization of the root cap. The central part of the cap (columella) contains 5 storeys of developing, functioning and degenerating statocytes. Their ultrastructure is very similar in all four types of plant. Particular attention was paid to the distribution of rough endoplasmie reticulum (ER). Both in the WT and the mutants the ER is concentrated in the distal part at the “floor” of the cell.Light micrographs were used to compare the sedimentation rates of movable cell structures in normal and agravitropic root statocytes. A longitudinal movement of amyloplasts and nuclei was observed when the roots were inverted. In WT and aux‐2 the rates were on average 6.3 μm h−1 (amyloplasts) and 2.1 μm h−1 (nucleus). In aux‐1 the sedimentation rates were significantly lower: 2.4 and 0.6 μm h−1, respectively. Based on magnified electron micrographs of normal and inverted statocytes a morphometrical analysis of the distribution and redistribution of amyloplasts, nuclei, mitochondria, vacuoles and ER was made. The only significant difference was found in the redistribution of amyloplasts between aux‐1 and the gravitropical normal types.
Resolution and characterization of multiple cytosolic phosphatases capable of hydrolyzing fructose‐1,6‐bisphosphate in spinach and soybean leaves
Authors: Pharr David M. , Huber Steven C. 
Published: April 2006

The apparent activity of cytoplasmic fructose bisphosphatase (EC 3.1.3.11) in crude extracts of spinach (Spinacia oleracea L.) and soybean (Glycine max [L.] Merr.) leaves was only partially dependent on Mg2+. At least two major non‐chloroplastic fructose bisphosphatases that differed in dependence on Mg2+ were chromatographically resolved from spinach leaves. The Mg2+‐dependent enzyme had an apparent Michaelis constant of 4 μM for fructose‐1,6‐P2, was highly specific, and was strongly inhibited by fructose‐2,6‐P2. Enzyme activity was inhibited by physiological levels of fructose‐6‐P.Both species also contained at least one major enzyme, the activity of which was independent of Mg2+. These enzymes had pH optima near neutrality, Michaelis constants of 25 to 30 μM for fructose‐1,6‐P2, and were inhibited by AMP. Although hexose monophosphates were not metabolized, the enzymes were not specific for fructose‐1,6‐P2: phosphate was released from phosphoenolpyruvate and ribulose‐1, 5‐P2, and with fructose‐1,6‐P2, as substrate, Pi release was about 1.5‐fold greater than fructose‐6‐P production. It is concluded that only the Mg2+‐dependent fructose bisphosphatase, previously characterized, functions in the photosynthetic sucrose formation pathway. Inhibition of the Mg2+‐dependent enzyme by fructose‐6‐P may be involved in regulation of sucrose formation.
Phosphorus nutrition of barley, buckwheat and rape seedlings. I. Influence of seed‐borne P and external P levels on growth, P content and 32P/31P‐fractionation in shoots and roots
Authors: Schjørring Jan K. , Jensén Paul 
Published: April 2006

Schjørring, J. K. and Jensén, P. 1984. Phosphorus nutrition of barley, buckwheat and rape seedlings. I. Influence of seed‐borne P and external P levels on growth, P content and 32P/31P‐fractionation in shoots and roots.Seedlings of barly (Hordeum vulgare L. cvs Salka and Zita), buckwheat (Fagopyrum esculentum Moench) and rape (Brassica napus L. ssp. napus ev. Line) were grown at 8 or 10 different external P levels in the range 0‐2000 μM. Apart from P, the nutrient solutions were complete. In some experiments with barley and rape, 32P‐labelled phosphate was used. Root fresh weights of buckwheat and rape decreased when the external P supply exceeded the level required for maximal root development. In all three species, the roots constituted a decreasing proportion of the total plant fresh weight as the external P level increased. The shoot/root fresh weight ratio increased linearly with the P concentration of the roots. The ratio between the P concentration in shoots and roots increased with the P status of the seedlings grown at low to intermediate external P levels, but decreased at higher P levels. The proportion of total seedling‐P held in roots consequently reached a minimum value and thereafter increased as the P status of the seedlings increased. This indicates that some control mechanism counteracted the accumulation of harmful P levels in the shoots. 32P‐Phosphate uptake by seedlings of barley and rape grown in solutions with 2 μM P overestimated the actual net phosphorus uptake by a factor of 6 to 7, indicating a marked fractionation of 32P and 31P. For seedlings grown in solutions with 25 μM P (barley) or 50 μM (rape) no fractionation occurred. The relative excess of 32P in high P seedlings accumulated in the roots. It is suggested that the fracionation was caused by efflux of low specific activity phosphorus and by diffusion of free phosphate ions across the plasmalemma of the root cells in response to a difference in the concentration gradient between the two P isotopes.
Non‐steady state xylem transport of fifteen elements into the tomato leaf as measured by gamma‐ray spectroscopy: A model
Authors: Wolterbeek H. Th. , van Luipen J. , de Bruin M. 
Published: April 2006

A model describing the transport of elements through the xylem vessels into the leaf of a red cherry tomato (Lycopersicon esculentum Mill cv. Tiny Tim) in a non‐steady state situation is presented. The model describes the upward movement of ions as a mass‐flow of the xylem fluid with dissolved elements, with lateral ion escape represented by a first‐order process. The model is fitted to data obtained in an experiment in which 15 elements were applied in a solution to a cut stem part with attached leaf and were measured simultaneously by gamma‐ray spectroscopy. The model is in good agreement with the transport into the leaf of K+ Na+, Rb+, Cs+, Yb3+, Sm3+ Zn2+, Co2+, Cu2+, Sb(SO4)2 AsO3+4, WO2+4; and Mo7O6+24.Only indirect data could be obtained for Cd2+ and La3+ because of their apparently high affinity for charged sites in the cell walls and high escape constant, respectively. The escape constants were relatively low for all anions, probably due to the presence of a large number of negative charges in the cell walls.
Betaine accumulation in salt‐stressed sorghum
Authors: Grieve C. M. , Maas E. V. 
Published: April 2006

Two analytical methods for measuring betaine were compared in a study of betaine accumulation in salt‐stressed sorghum. Spectrophotometric determination of betaine as the p‐bromophenacyl ester is highly sensitive and specific. However, a periodide assay was found to be more convenient for screening numerous plant samples without undue sacrifice in accuracy.The accumulation of betaine in grain sorghum [Sorghum bicolor (L.) Moench] cvs NK 265 and Double TX was measured in salt‐stressed plants grown hydroponically and in the field and in drought‐stressed potted plants. Neither drought nor mild salinity (‐0.2 MPa) stress was effective in stimulating betaine accumulation. However, when the osmotic potential of the culture solution was lowered to ‐0.8 MPa, betaine levels in the shoots rose rapidly for 12 days after initiation of salination, and then declined, apparently because of dilution by plant growth. In young leaf blades, betaine was strongly accumulated up to 70–75 μmol (g dry weight)−1; the concentration in leaf sheaths was less than 6 μmol (g dry weight)−1.In the field, betaine levels in salt‐stressed sorghum increased 6‐ to 7‐fold over the basal level of the control plants. In a comparable study of two wheat species (Triticum aestivum L. cv. Probred and T. durum Desf. cv. 1000‐D), betaine increased only 3‐ to 4‐fold over unstressed plants.