摘要:

The dominant plant species in native pine forests in Israel (Pinus halepensis. Cistus salviifoliusandC. creticus) regenerate from seeds after wildfires. The future structure of the regenerating forest is determined largely by the spatial distribution of the seedlings, which depends on the response of the seeds to conditions in the upper layer of the soil. The pH and osmotic potential (π) of the soil water in this layer is strongly affected by the ash which covers the burned forest floor. The effects of pH and π on the germination of the wild species noted above and the effect of pH on the germination of two crops, radish(Kaphanus sativus radicula)and oat(Avena sativa)were studied in a growth chamber. Bis‐Tris propane and CAPS [3‐(cyclohexylamino)‐l‐propanesulfonic acid] buffer solutions (pH 6–11), as well as mannitol solutions (down to –1.5 MPa) were used. The upper soil layer from a recently burned forest had pH 9 and π–0.08 MPa. Under this pH the germination ofP. halepensisandC. creticuswas reduced by ca half, and ofC. salviifoliusby 40%. Germination of radish and oats was reduced by ca 80%. Osmotic potential of –0.1 MPa did not have a significant effect on the germination of any of the species studied. We conclude that the high pH of the soil, caused by ash, is an important environmental factor that controls the regeneration of the forest plant community. Seed adaptation to the high pH may be decisive in determinig the plants' fate the fir

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00185.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The determination of the various endogenous cylokinins and their distribution among organs is important in understanding their role in growth and development in the intact plant. Cytokinins in young plants ofPhaseolus vulgariswere purified by immunoaffinity chromatography and HPLC, and characterised by UV spectra. Zeatin nucleotide (zeatin riboside‐5′‐monophosphate) and isopentenyladenine nucleotide (isopentenyladenosne‐5′‐monopnosphate) were the most abundant cytokinins in all organs. Their identities were confirmed by GC‐MS. The levels of zeatin, zeatin riboside, isopentenyladenine and isopentenyladenosine never exceeded 5% of the nucleotides, as assessed by a methodology that preserves cytokinin nucleotides. Three extraction methods were compared with qualitatively similar results, though differing in their suppression of nucleotidase activity. Cytokinin nucleotide levels were greater in the stems and petioles than in the roots and leaves on a per gram fresh weight basis, and were greater in the stems than in the other organs on a per plant basis. Levels of the zeatin and isopentenyladenine nucleotides were about equal in the stems and leaves, but in the petioles the zeatin nucleotide levels were about twice the level of isopentenyladenine nucleotide, while in the roots they were about half the isopentenyladenine nucleotide level. The importance of considering the cytokinin form

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00186.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

We examined changes in the protein composition of cytoplasmic ribosomes in etiolated barley leaves following illumination. Cytoplasmic ribosomes were isolated from greening barley leaves by sucrose density gradient centrifugation, and were analyzed by radical‐free highly reducing polyacrylamide gel electrophoresis (RFHR‐PAGE). Eighty‐nine proteins were resolved from the ribosomal fraction; among them, 8 proteins changed their copy numbers depending on the stage of greening. We designated these as phase dependent ribosomal proteins (PD1–PD8). Two of the proteins (PD1 and 5) present in the ribosomes of etiolated leaves showed a decrease in level during greening. In contrast, the levels of 6 ribosomal proteins (PD2, 3, 4, 6, 7 and 8) increased as greening proceeded. N‐terminal amino acid sequence of PD8 showed high homology to rat ribosomal protein L34. The ribosomal proteins that appeared after illumination were not found in any fraction of the etiolated leaves, suggesting that they were synthesized after the onset of illumination. Copy numbers of other ribosomal proteins did not change during

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00187.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Starch and sucrose metabolism of one‐ and two‐year‐old needles of Norway spruce (Picea abies[L.] Karst., about 30 years old) was investigated from three months before until three months after bud break at a natural site. We distinguish different metabolic states according to the extractable activities of enzymes (α‐amylase [EC 3.2.1.1], ADP‐glucose pyrophosphorylase [AGP, EC 2.7.7.27], D‐enzyme [EC 2.4.1.25], starch phosphorylase [STP. EC 2.4.1.1]), sucrose phosphate synthase [SPS, EC 2.4.1.14], sucrose syntbase [SS, EC 2.4.1.13]. acid invertase [AI, EC 3.2.1.261) and pool sizes of related metabolites (starch, glucose, fructose, sucrose, raffinose, stachyose, fructose 6‐phosphate [F6P], glucose 6‐phosphate [G6P], fructose 2,6‐bisphosphate [F26BP], and inorganic phosphate [P1]). The period ending with bud break was characterized by high rates of net photosynthesis, a pronounced decrease in the amount of soluble sugars, and a steep rise in starch (from the detection limit to approximately 600 nmol glycosyl units [mg dry weight]‐1). In parallel, the extractable activity of AGP increased, while D‐enzyme was on a relative high level when compared with the period after bud break. With respect to sucrose metabolism, F26BP, an inhibitor of sucrose synthesis, decreased from 1 to 0.4 pmol (mg dry weight)‐1. This was complemented by SPS activity, which was due to both increased protein levels shown by immunoblotting and activation under metabolite control (high levels of G6P and a low Pi/G6P ratio). This indicates a high capacity of synthesis of starch and sucrose in the period before bud break. These observations are in accordance with estimates of photosynthetic carbon gain, which indicate that in early spring large amounts of carbon from current photosynthesis are exported out of the needles. In addition, the content of nonstructural carbohydrates (expressed as hexoses) increased in the bark of the stem. This could also be a consequence of an enhanced carbon export from the needles.After the onset of bud break, starch concentration decreased in all tissues under investigation. In contrast, the level of total nonstructural carbohydrates in the outermost sapwood nearly doubled from bud break until the end of sampling. In the needles, net photosynthesis was reduced by about 75% and a decrease in SPS activity and protein level were found together with lower G6P concentration, and an increased Pi/G6P ratio. These results suggest that during that period sucrose synthesis was reduced in the older needles. In addition, under conditions of reduced photosynthesis, carbon demand of current year needles was in part ensured by the mobilization of starch in the older needles.Taken together our data show that before bud break carbon metabolism of mature leaves is related with the sink demands of storage organs. After bud break the accumulated assimilate pools in needles and stem, mainly the bark, are mobilized and support carb

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00188.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Nodulated (T202) and non‐nodulated (T201) isolines of soybean (Glycine max[L.] Merr.) were cultivated in a rotated paddy field in Niigata, Japan. The pods, and seeds were harvested at 7‐day intervals until maturity, and the subunit compositions of seed storage proteins were analyzed by SDS‐PAGE. The β‐subunit of β‐conglycinin could scarcely be detected in the non‐nodulated isoline, T201, at any period throughout seed development, although it was a major component in T202. The accumulation of α′‐ and α‐subunits of β‐conglycinin, together with the acidic and basic subunits of glycinin, appeared about one week later in seeds of T201 than in those of T202, perhaps due to a shortage of nitrogen and growth retardation. Northern hybridization could not detect the β‐subunit mRNA in immature T201 seeds, while it was pronounced in T202. These results indicate that the suppression of the β‐subunit in the non‐nodulating isoline T201 is regulated at the level of mRNA accumulation. The α′(α)‐subunit mRNAs were actively expressed in both isolines. Total nitrogen concentration was consistently lower in T201 than T202. No significant difference was observed in either the free amino acid or ureide concentrations in seeds, although the concentration of sucrose was considerably lower in T201 seeds and pods compared with T202. This result indicates the possibility that β‐subunit accunmlation was regulated not only directly by total nitrogen concentration but also by carbohydrate concentrations.Nitrogen regulation of storage protein subunit levels of soybean seed were evaluated using T201 and T202. Greenhouse‐grown plants were subjected to different levels and timing of nitrate treatments. The culture solution (2, 5 or 10 mMNO3–was supplied from flowering, 42 days after planting (DAP), until maturation (137 DAP), or switched from 2 to 10 mM, or from 10 to 2 mMat 61 DAP. With a continuous 2 mMNO3–treatment, seed dry weight and N concentration of the T201 plants were significantly lower than those in the T202 plants due to the lack of N2fixation by the non nodulated T201 plants. However, when adequate NO3was supplied, N concentration and dry weight were similar in T201 and T202 seeds. When 5 mMNO3was supplied, the subunit proportion of the seed storage protein was similar in non‐nodulating and nodulating isolines. On the other hand, when plants received a low level of NO3(2 mM), the β‐conglycinin proportion was lower in T201 than in T2O2. Furthermore, in the nodulating T202 plants treated with 10 mMNO3–the proportion of β‐conglycinin increased markedly.The results indicate that non‐nodulated T201 has a normal, non‐defective, β‐subunit gene and that limited N availability decreases accumulation of β‐conglycinin, whereas high N availability increases the proportion of β‐conglycinin in soybean seeds, irres

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00189.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Provenances of seedlings of Scots pine (Pinus sylvestrisL.) from northern Finland (65°N) and cuttings from trees of the same species about 30 to 40 years in age were studied in 3 artificial deacclimation experiments during the winter and spring of 1994. The deacclimation conditions varied in terms of temperature rise and photoperiods. Frost resistance and the pH of the cell effusate were studied in order to investigate the possibility of a connection between them. Complete deacclimation was achieved, as shown by a frost resistance of –60°C to –65°C in the seedlings and –8O°C in the cuttings at the beginning of the experiment and decreased to above –10°C by the end. The frost resistance and pH of the cell effusate responded significantly to the increase in temperature that marked the onset of the deacclimation process, whereas the response to different photoperiods was only slight. A highly significant correlation was found between frost resistance and the pH of the cell effusate. These variables were also significantly correlated with the freezing test temperature, indicating the condition of plasmalemma and tonoplast; and with sampling day, indicating the response to deacclimation. In the light of these findings, it is concluded that the pH of the cell effusate with certain reservations, can be used as a time saving, alternative viability test when determining fros

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00190.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Copper interferes with numerous physiological processes and can be toxic at low concentrations. We examined the effect of a 2‐week exposure to various concentrations of copper on the structure of the nucleus in maize root meristem cells by transmission electron microscopy. Copper uptake and distribution in the plants, as well as DNA synthesis were also investigated. Treatment with Cu induced alterations in the structure of the nucleus, resulting mainly in a greater density of chromatin. Morphometric analysis showed that the part of the condensed chromatin in the nucleus might be increased by Cu, an observation that was correlated with decreased DNA synthesis as measured by incorporation of3H‐thymidine. Copper may therefore play a role in chromatin structure and one of the manifestations of Cu toxicity is an alteration in the structure of the nucleus, leading to decreased DNA synthe

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00191.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The donor‐recipient fusion method was used to combine the cytoplasm ofBrassica lournefortiiwith the nucleus ofB. napusfor the production of cytoplasmic male sterile (CMS) plants. X‐ray‐irradiated mesophyll protoplasts ofB. tournefortiiwere fused with iodoacetamide (lOA)‐inactivated hypocotye protoplasts ofB. napus. Selective conditions of IOA concentrations and X‐ray doses were determined, which resulted in recovery of fusion products and inhibition of further growth of unfused parental cells. In total, 54 plants were obtained from different fusion experiments, of which 25 were verified as cybrids or partial hybrids. Mitochondrial DNA (mtDNA) analyses using 5 mitochondrial gene probes revealed that 20 of the 25 fusion‐derived plants had mtDNA either identical, or with varying degrees of similarity, toB. lournefortii. These plants were classified into four groups on the basis of pollen viability and number. Seven plants were categorised as male sterile since they did not produce pollen or had non‐viable pollen. Of the male sterile plants, five had a mtDNA pattern identical toB. tournefortiiand a nuclear DNA content corresponding toB. napus. The nuclear‐mito‐chondrial constitution of these plants thus indicates that the combination ofB. tournefortiicytoplasm with theB. napusnucleus results in CMS. Furthermore, mtDNA analysis of the two additional male sterile plants which displayed a rearranged mtDNA, revealed that the only mtDNA similarity shared among all male sterile plants was specific forB. tournefortii atp6pattern. This indicates that theatp6region ofB. tournefortiimay be involved in the

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00192.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The profile of chaitinases (EC 3.2.1.14) in mature carrot (Daucus carotaL. cv. Eagle) roots was studied. Multiple chitinase bands (8–10) were observed in native and sodium dodecylsulfate‐denaturing polyacrylamide gels. The molecular masses of these chitinases were estimated to be from 20 000 to 40 000. One major chitinase was purified and found to be an acidic protein with pI at 4.3 and a molecular mass of 39 500. The optimum pH for enzymatic activity was around 5 and the optimum temperature was 25°C. The enzyme was stable at pHs below 8 and temperatures below 60°C. The protein did not have a chitin‐binding domain, but showed some similarity to the amino acid composition of tobacco class I chitinase. The N‐terminal amino acid sequence did not resemble any of the described classes of chitimases. This chitinase did not possess lysozyme activity and showed antifungal activity when tested againstTric

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00193.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Chloroplast development and chlorophyll biosynthesis are co‐regulated. To understand the mechanism of regulation of chloroplast biogenesis by chlorophyll, development of the photosynthetic apparatus was monitored during greening of etiolated barley leaf discs in the presence of levulinic acid, an inhibitor of chlorophyll biosynthesis. Although not a direct inhibitor of carotenoid biosynthesis, treatment by levulinic acid resulted in a linear reduction in both chlorophyll and carotenoid contents. Chlorophyll biosynthesis appeared to control that of carotenes. In the presence of levulinic acid, photosystem II (PSII) activity decreased while photosystem I (PSI) activity increased when expressed on a chlorophyll basis. However, the activities of both photosystem I and II decreased when expressed on a per plastid basis. As expected, in the presence of low amounts of chlorophyll, the light‐harvesting chlorophyll‐protein complex II (LHCPII) was not visible in Coomassie‐stained gels in 20 mMlevulinic acidtreated tissues, but was detected as a faint band by immunoblotting. This small amount of the LHCPII induced significant amounts of grana stacking, which was monitored as an increase in the ratio of variable to maximum fluorescence. When levulinic acid was washed from the leaf discs and the latter allowed to green in its absence, the chlorophyll and carotenoid contents and the photosynthetic activities approached the control values. Levulinic acid could be used to arrest the light‐induced chloroplast development at a desired phase of greening and removed by washing the leaves to restore the developmental process without any apparent toxic effect. Results demonstrate that biosynthesis of carotenes is regulated by that of chlorophylls and extremely low amounts of the LHCPII can induce grana

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00194.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY