bluuebunny/crossref_metadata_2025_split huggingface dataset:
Embryology in Norway spruce (Picea abies). Immunochemical studies on transport of a seed storage protein
Authors: Hakman Inger 
Published: May 2006

One of the main seed storage proteins of Norway spruce (Picea abies), is a salt‐soluble protein with an average molecular mass of 42 kDa. This protein was localized by immunocytochemical methods in ultrathin sections of megagametophytes active in storage protein synthesis, as analyzed by SDS‐PAGE. The megagametophyte in spruce starts accumulating storage materials, proteins and lipids, as the young embryo grows into the gametophytic tissue. It then continues to accumulate these storage products throughout seed development (Hakman 1993). Megagametophytes at an early stage of storage protein accumulation were chosen in this study for analysing the likely transport pathway of the proteins, since only a small amount of lipid had yet accumulated in the cells, and cell organelles were still easy to distinguish. An antibody against the 42 kDa storage protein showed very good reactivity with the 42 kDa protein in immunoblot experiments with total protein extracts from megagametophytes and embryos. In ultrathin sections of the megagametophyte, the antibodies were preferentially localized in the lumen of Golgi cisterna, in Golgi‐associated vesicles, protein deposits close to the vacuolar membrane and in protein storage vacuoles (protein bodies). These observations indicate that the transport is mediated by the Golgi apparatus.Also, proteins present in storage vacuoles in mature zygotic and somatic embryos showed intense labelling with these antibodies in ultrathin sections.
Nicotianamine: mediator of transport of iron and heavy metals in the phloem?
Authors: Stephan Udo W. , Scholz Günter 
Published: May 2006

Recent work has demonstrated that minerals in plants are circulated between root and shoot. This occurs during the whole life time and renders possible response to changing environmental conditions. This mineral circulation occurs through intensive solute exchange between xylem and phloem in roots, stems, and leaves. The transport form of heavy metals such as iron, manganes, zinc and copper in the phloem, whether ionic or chelated, is unclear in most cases.The unusual amino acid nicotianamine (NA) is ubiquitous throughout the plant kingdom. It is a chelator of several divalent transition metals. Its physiological role was investigated with the tomato mutant chloronerva, the only known NA‐free multicellular plant. The mutant also exhibits disturbances of its iron metabolism and that of other heavy metals. This leads, among others, to a typical intercostal chlorosis and progressive iron accumulation in the leaves. From the heavy metal chelating properties of NA and from the phenotype of the mutant chloronerva it is concluded that NA is needed for normal distribution of heavy metals in young growing tissues fed via the phloem. This function could be fulfilled by mediating phloem loading or unloading of heavy metals as well as by preventing their precipitation in the alkaline phloem sap. An attempt is made to explain the chloronerva phenotype in the light of the phloem transport hypothesis of chelated iron.
Exothermic responses of dormant Salix stems during exposure to subzero temperatures
Authors: von Fircks Heinrich A. 
Published: May 2006

Differential thermal analysis (DTA) was used to determine the exothermic responses in dormant stems and excised lengths of stem ofSalix dasyclados Wimmer subjected to artificial freezing treatments.The presence of ice on the surfaces of intact stems restricted the mechanism of freezing avoidance to temperatures above –4°C. In contrast, excised lengths of stem started to freeze as soon as the ambient temperature fell below –2°C, demonstrating that extracellular ice formation takes place earlier if cut surfaces are present. Exposure of dormant excised lengths of stem to subfreezing temperatures for more than 8 weeks did not alter their nucleation temperature not their exothermic differential responses. Early extracellular crystallisation of freezable cellular water provides conditions that allow dormant Salix dasyclados stems or excised lengths of stem to survive extreme freezing stress.Crystallisation of extracellular and cellular water took place in the cortex, and did not result in visual damage or reduced survival. This nucleation of extracellular water took place over the same temperature range whether the excised dormant lengths of stem were partly (bark only) or completely thawed. Exposure of dormant tissue to 20°C for up to 24 h did not alter the level of freezing tolerance, nor did it increase the susceptibility of excised lengths of stem to damage by extreme temperature fluctuations.
The presence of a short redox chain in the membrane of intact potato tuber peroxisomes and the association of malate dehydrogenase with the peroxisomal membrane
Authors: Struglics André , Fredlund Kenneth M. , Rasmusson Allan G. , Møller Ian M. 
Published: May 2006

Peroxisomes and mitochondria were purified from potato tubers (Solanum tuberosum L. cv. Bintje) by differential centrifugation followed by separation on a continuous Percoll gradient containing 0.3 M sucrose in the lower half and 0.3 M mannitol in the upper half. The peroxisomes band at the bottom and the mitochondria in the middle of this type of gradient. Mitochondrial contamination of the peroxisomes was only 2% [as judged by cytochrome c oxidase (EC 1.3.9.1) activity]. Contamination by amyloplasts, plasma membrane and endoplasmic reticulum was also minimal. The peroxisomes were 80% intact as judged by malate dehydrogenase (MDH, NAD−‐dependent; EC 1.1.1.37) latency.The specific activity of NADH‐ferricyanide reductase and NADH‐Cyt c reductase was 0.22 and 0.051 μmol (mg protein)−1 min−1 in freshly isolated peroxisomes, respectively. The active site of the reductase appeared to be on the inner surface of the membrane. The peroxisomes also contained a b‐type cytochrome. Frozen peroxisomes were subfractionated by osmotic rupture followed by centrifugation to separate the soluble proteins from the peroxisomal membrane. About half the MDH and 30% of the NADH‐ferricyanide reductase activity was associated with the membrane but only 6% of the catalase (EC 1.11.1.6) activity. A further wash removed 75% of the residual catalase with only a small loss of MDH or NADH‐ferricyanide reductase activity. MDH appears to be closely associated with the peroxisomal membrane.When the purified peroxisomal membrane was analyzed by SDS‐PAGE followed by silver staining, prominent bands at 22, 40, 41, 48, 53 and 74 kDa were observed. After immunoblotting the purified peroxisomal membrane, a band at 53 kDa showed strong cross‐reactivity with antibodies raised against NADH‐ferricyanide reductase. Since the NADH‐ferricyanide reductase activity in the peroxisomal membrane could be shown to be specific for the β‐hydrogen of NADH, the activity could not be due to contamination by endoplasmic reticulum where the reductase is α‐specific. We conclude that the peroxisomal membrane contains a short redox chain, consisting of a NADH‐ferricyanide reductase and a b‐type cytochrome, similar to that of e.g. the plasma membrane. The role of this redox chain has yet to be elucidated.
Selection in vitro for UV‐tolerant sugar beet (Beta vulgaris) somaclones
Authors: Levall Mats W. , Bornman Janet F. 
Published: May 2006

With a reduced stratospheric ozone concentration, the generation of UV‐tolerant plants may be of particular importance. Among different crop plants there is large variation in sensitivity to UV‐B radiation. This study was undertaken to investigate the possibilities of using somaclonal variation and selection in vitro for improving UV‐B tolerance in sugar beet (Beta vulgaris L.).Sugar beet callus was exposed to UV radiation (280–320 nm, 0.863–5.28 kJ m‐2 day‐1, unweighted) and resultant shoots were selected from surviving cells. After establishment of the plants, they were grown under either visible radiation (114 μmol m‐2 s‐1 PAR) or with the addition of UV radiation (6.3 kJ m‐2 day‐1 biologically effective UV‐B). Screening of regenerants in vivo for tolerance to UV radiation was undertaken 10 months after termination of the UV selection pressure. Screening was done visually and by using a number of physiological parameters, including chlorophyll fluorescence induction, ultraweak luminescence, pigment analysis and total content of UV‐screening pigments. A clear difference between the unselected and the UV‐selected somaclones was observed when visually studying the UV damage and other leaf injury. The observations were supported by the ultraweak luminescence measurements. Unselected plants showed significantly greater damage when subjected to subsequent UV radiation as compared to the selected plants. The clones subjected to UV selection pressure displayed a significantly higher concentration of UV‐screening pigments under subsequent UV radiation. The unselected plants under subsequent UV treatment showed a lower carotenoid concentration when compared to selected plants. However, no significant difference between treatments was found for chlorophyll a/b, or F/Fmax, a measure of photosynthetic quantum yield.
Implications of N acquisition from atmospheric NH3 for acid‐bAse and cation‐anion balance of Lolium perenne
Authors: Wollenweber B. , Raven J. A. 
Published: May 2006

In the atmosphere, ammonia (NH3) is the third most abundant N species which, due to various natural and anthropogenic sources, can locally reach high concentrations. The acquisition of atmospheric NH3 by plant shoots will lead to two opposing effects on acid‐base balance. Absorption and dissolution of NH3 will cause an alkalinisation, while the assimilation of NH3 results in an acidification. Different rates of these processes would lead to an acid‐base imbalance with consequences for the ionic balance of the plant. As there is only a limited capacity for biochemical disposal of excess H+ in shoots, pH regulation may involve a pattern of (in)organic ion flow between shoots and roots followed by H+/OH− extrusion into the media via roots. The acquisition of NH3 as additional N source should lead to a reduction in the ratio of mol H+/OH− gained per mol N assimilated.We have recently investigated the NH3 acquisition by Lolium perenne L. cv. Centurion and studied the effects of gas phase NH3 on growth, acid‐base balance and water‐use efficiency. The experiments, therefore, included the application of a range of 14NH3 to the shoots and of 15N as NO3−, NH4+ or NH4NO3 to the roots. After a summary of the main conclusions from those experiments, we discuss the implications of the use of atmospheric NH3 for the mineral composition of the plants.Over the range of NH3 supplied, plants from all treatments could utilize gas‐phase NH3. Plants receiving NO3− via their roots had a higher capacity to use gaseous NH3 than those growing with NH4+. NH3 assimilation in shoots reduced both the acid load with NH4+ nutrition and the alkaline load with NO3− supply to the roots. The most significant effect of fumigation on the ion balance was an increase in K+ within all treatments, and this effect was highest in the NH4+‐fed plants. The results of the experiments support predictions of a combination of neutralizing biochemical reactions as well as transport of organic anion salts between shoots and roots as possible acid‐base regulation mechanisms of the whole plant.
Effects of N‐supply on the rates of photosynthesis and shoot and root respiration of inherently fast‐ and slow‐growing monocotyledonous species
Authors: Van Der Werf Adrie , van Nuenen Marc , Visser Andries J. , Lambers Hans 
Published: May 2006

Are there intrinsic differences in the rates of photosynthesis, shoot‐ and root‐respiration between inherently fast‐ and slow‐growing monocotyledons at high and low nitrogen supply? To analyze this question we grew 5 monocotyledons, widely differing in their inherent relative growth rate at high and low nitrogen supply in a growth room. Nitrate was exponentially added to the plants, enabling us to compare inherent differences in plant characteristics, without any effect of species differences in the ability to take up nutrients.At high nitrogen supply, the fast‐growing species from productive habitats had a higher photosynthetic nitrogen use efficiency and rate of root respiration than the slow‐growing ones from unproductive habitats. Only minor differences were observed in their rates of photosynthesis and shoot respiration per unit leaf area. At low nitrogen supply, the rates of photosynthesis and shoot‐ and root respiration decreased for all species, even though there were no longer any differences in these processes between inherently fast‐ and slow‐growing species. The photosynthetic nitrogen use efficiency increased for all species, and no differences were found among species.Differences in the photosynthetic nitrogen use efficiency among species and nitrogen treatments are discussed in terms of the utilization of the photosynthetic apparatus, whereas differences in respiration rate are discussed in terms of the energy demand for growth, maintenance and ion uptake and their related specific respiratory energy costs. It is concluded that the relatively high abundance of slow‐growing species compared to fast‐growing ones in unproductive habitats is unlikely to be explained by differences in rates of photosynthesis and respiration or in photosynthetic nitrogen use efficiency.
Possible role of adenylates in the engagement of the cyanideresistant pathway in nutrient‐starved Catharanthus roseus Cells
Authors: Hoefnagel Marcel H. N. , Van Iren Frank , Libbenga Kees R. , Van der Plas Linus H. W. 
Published: May 2006

In Cathuranthus roseus (L.) G. Don cells the cyanide‐resistant pathway is engaged after phosphate or nitrogen starvation. Re‐addition of these nutrients disengaged it again. Re‐addition of phosphate leads to a transient disengagement which becomes only permanent after a second addition of phosphate. Disengagement after re‐addition of nitrogen is slow: it takes 9 days before the activity has disappeared. In this system the mechanism of engagement of the cyanide‐resistant pathway was studied. Addition of phosphate to phosphate‐starved cells induced cell division within 24 h. The disengagement of the cyanide‐resistant pathway was probably only an indirect effect of phosphate because the cellular P, content, which increased rapidly after addition, was low again before the cyanide‐resistant pathway was disengaged. A better correlation was observed between high ADP and adenylate content of the cells and disengagement of the cyanide‐resistant pathway. In addition it appeared that the engagement of the cyanide‐resistant pathway was not the result of a limited carrier capacity of the cytochrome pathway. It is tentatively concluded that the engagement of the cyanide‐resistant pathway in phosphate‐starved cells was the result of a limited adenylate content.After nitrogen addition to N‐starved cells, it took 5 days until the first growth occurred. Before the cyanide‐resistant pathway was disengaged, its activity increased with the increased respiration rate which preceded growth. Within 72 h a higher ADP content was observed, which was still high after 10 days. The stimulation of the cytochrome pathway by uncoupler was small and more or less the same with and without added nitrogen, as long as the cyanide‐resistant pathway was engaged. After disengagement the stimulation by uncoupler was significantly larger. It is suggested that the engagement during N‐starvation was the result of a limited carrier capacity of the cytochrome pathway.Stimulation of the metabolism by re‐addition of phosphate, nitrogen or sucrose resulted in a rapid increase in the levels of uracil nucleotides and uridine diphosphoglucose (UDPG) which are involved in sucrose metabolism.
Genetic study of resistance to inhibitory effects of UV radiation in rice (Oryza sativa)
Authors: Sato Tadashi , Kang Hye Sook , Kumagai Tadashi 
Published: May 2006

Genetic analysis of resistance to the inhibitory effects of UV radiation on growth of rice (Oryza sativa L.) cultivars was carried out. Some experimental plants were grown in visible radiation supplemented with UV radiation containing a large amount of UV‐B and a small amount of UV‐C in a phytotron, while others were grown without UV radiation. The degree of resistance to UV radiation was estimated in terms of the degree of reduction caused by supplemental UV radiation in the fresh weight of the aboveground plant parts and the chlorophyll content per unit fresh weight. Fresh weight and chlorophyll content in F2 plants generated by reciprocally crossing cv. Sasanishiki, a cultivar more resistant to UV radiation, and Norin 1, a cultivar less resistant to such radiation exhibited a normal frequency distribution. The heritabilities of these two properties in F2 plants were low under conditions of non‐supplemental UV radiation. Under elevated UV radiation, the F2 population shifted to the lower range of fresh weight and chlorophyll content, and the means were close to those of Norin 1. The heritabilities of these two properties were the same in the reciprocal crosses, indicating that maternal inheritance was not involved. Inheritance of chlorophyll content per unit fresh weight was further determined in F3 lines generated by self‐fertilizing F2 plants of Sasanishiki and Norin 1. The results showed that the F3 population was segregated into three genotypes, namely, resistant homozygotes, segregated heterozygotes and sensitive homozygotes, with a ratio of 1:65:16.It was thus evident that the resistance to the inhibitory effect of elevated UV radiation in these rice plants was controlled by recessive polygenes.
Influence of irradiance on in vitro growth and proliferation of Vaccinium corymbosum (highbush blueberry) and subsequent rooting in vivo
Authors: Noè Nicola , Eccher Tommaso 
Published: May 2006

The effects of light on in vitro proliferation and subsequent in vivo rooting and acclimatisation of Vaccinium corymbosum were investigated. The shoots were exposed in vitro to different irradiances (total radiation ranging from 55 to 240 μmol m−2 s−1) for 7 to 60 days. In vitro growth and proliferation and the possible consequences on in vivo rooting were observed.As compared to the control treatment (55 μmol m−2 s−1), higher irradiances improved proliferation and rooting ratios only with short applications (7 days). Short but high (210 μmol m−2 s−1) exposures applied at the end of the proliferation phase increased in vivo growth and rooting of the shoots. The shoots treated with strong light for longer times (14 and 28 days) showed both inhibition of growth and red colour of leaves and sprouts, and were less vigorous when transferred in vivo.
Drought and chlorophyll fluorescence in field‐grown potato (Solanum tuberosum)
Authors: Jefferies R. A. 
Published: May 2006

Light interception, stomatal conductance and chlorophyll fluorescence were measured in potato (Solanum tuberosum L.) grown either irrigated, or droughted from the time of plant emergence. Compared with the irrigated treatment, drought reduced both light interception and stomatal conductance. In both treatments, the yields of variable fluorescence in the dark‐ and light‐adapted states (Fy/Fm and F′v/F′m, respectively) were negatively correlated with photosynthetic photon flux density (PPFD) and mirrored daytime changes in PPFD. Photochemical quenching was positively correlated with PPFD, but the dominant effect of F′v/F′m resulted in a decrease in the quantum yield of photosystem II (PSII) electron transport with increasing PPFD.Drought had no significant effect on the functioning of PSII and the balance between photochemical and non‐photochemical quenching was unaffected. Non‐photochemical quenching was not increased by drought and the quantum yield of PSII electron transport was unaffected. It is concluded that, in leaves of droughted plants, excess energy, resultant of stomatal limitation of photosynthesis, was dissipated by photochemical quenching such as increased photorespiration.
Regulation of a petal‐specific ethylene‐induced 70‐kDa protein from Dianthus caryophyllus
Authors: Jiang Wei Bo , Mayak Shimon , Weiss David , Halevy Abraham H. 
Published: May 2006

Ethylene enhances senescence of carnation (Dianthus caryophyllus L.) flowers. Sephacryl S‐200 gel filtration followed by SDS‐PAGE of extracts of petals exposed to ethyiene revealed the increase or appearance of proteins with molecular masses of 70, 60, 35 and 33 kDa, and a concomitant decrease in proteins with molecular masses of 62. 45. 34. 30 and 26 kDa. The 70‐kDa protein, which was not detected in untreated flowers, was isolated and polyclonal antibodies were prepared against it. Its N‐terminal sequence (20 amino acids) was identical to that of a portion of the deduced protein encoded by cDNA clone pSR 12. recently isolated by others from carnation petals. Western blot analyses of petal extracts after various exposure times to ethylene alone or in the presence of translation or transcription inhibitors suggested that accumulation of the 70‐kDa protein is due primarily to ethylene‐induced synthesis. The apparent induction by ethyiene was further supported by data indicating that the protein is not formed in flowers pre‐treated with silver thiosulfale. an inhibitor of ethylene action, prior to exposure to ethylene. Ethylene induction of the protein was found only in petal tissue, and the protein was not detected in other carnation plant organs. Immunological studies revealed that the protein is specifically expressed in carnation petals and not in petals of several other flowers. Southern and northern analyses using an SRI2 cDNA probe indicated that the genomic DNA of petunia, carnation, and gerbera contain fragments homologous to SRI2. Gene expression products were however, only detected in petals of ethylenetreated carnation flowers.
Unusual composition of thylakoid membranes of the resurrection plant Boea hygroscopica: Changes in lipids upon dehydration and rehydration
Authors: Navari‐Izzo Flavia , Ricci Federico , Vazzana Concetta , Quartacci Mike F. 
Published: May 2006

Boea hygroscopica is a resurrection plant that is able to pass from biosis to anabiosis and vice versa following slow dehydration, but loses this ability following a rapid water loss. Fresh leaves were detached from plants grown in well‐watered conditions and subjected to either rapid or slow dehydration and rehydration. Upon rehydration only slowly dried leaves revived. Analysis of thylakoid membranes revealed a rather small amount of total lipids (1,4–2 μmol g−1 dry weight) in comparison with other flowering plants. The main glycolipid was digalactosyldiacylglycerol (DGDG) rather than monogalactosyldiacylglycerol (MGDG) as is common in higher plants.Linoleic acid was the main fatty acid (30–40 mol% of total fatty acids), while linolenic acid was present from 14 to 26 mol%. In both the fresh and rehydrated leaves nearly all lipid components were present in similar amounts. Following dehydration the DGDG/MGDG molar ratio, which was 1.1 in control and rehydrated leaves, doubled by the end of the rapid drying period and was three times as high in slowly dried leaves. The total polar lipid/free sterol molar ratio as well as the free fatty acid level assumed the highest values in the rapidly dehydrated leaves. A shift towards the more unsaturated fatty acids was observed in all lipid classes upon dehydration irrespective of whether it was slow or rapid. Our data show only small differences between rapidly and slowly dehydrated leaves which can be correlated to the capacity of slowly dehydrated leaves to revive.