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81.
Effects of aluminium on growth and cation uptake in seedlings of Eucalyptus mannifera and Pinus radiata 总被引:1,自引:0,他引:1
This experiment was designed to examine the effects of aluminium (Al) on the growth of Pinus radiata (D. Don) and Eucalyptus mannifera subsp. mannifera (Mudie) seedlings in culture solutions in a glasshouse to help explain the failure of radiata pine trees on some acid, low
fertility soils in Australia on which the native eucalypts flourish. Aluminium (Al) in culture solution increased the growth
of roots and shoots of seedlings of both species but while growth of the eucalypt continued to increase with increases in
Al to 2.222 μM, growth of the pine was largest at 370 μM Al. In addition to total root length, specific root length (length per unit dry weight), a measure of fineness of the root,
increased in the eucalypt seedlings as the substrate Al increased. Growth of the shoots and roots of the pine in the absence
of any added Al was extremely poor suggesting that Al, in low concentrations, may be an essential element or ameliorate some
other factors in solution culture at low pH.
Root and shoot concentrations of K increased with increasing Al, whilst Ca and Mg Concentrations decreased and Mn concentrations
were unaffected in both species. Tissue Ca and Mg concentrations were 2 to 3 times higher in the eucalypt seedlings than the
pine at all levels of added Al due to greater uptake of these elements by the eucalypt. In contrast, at the highest concentration
of Al in the medium, shoot Al concentrations were lower in the cucalypt than in the pine due to a greater proportion of Al
being retained in the eucalypt roots.
These differences between the seedlings in terms of root growth and tissue cation concentrations may help explain the ability
of eucalypt species to maintain vigorous growth on acid soils high in Al and low in Ca and P, where growth of the pines failed. 相似文献
82.
[3H]iso-Pentenyladenine ([3H]iP) was fed for 24 h to the tips of intact and root tip-decapitated Pinus pinea seedlings. Twelve and 24 h after application to the roots of intact plants most of the applied radioactivity (±60%) was transported to the shoot. Root tip removal increased transport of the applied radioactivity to the shoot, but the overall pattern of distribution of radioactivity in the seedling did not change. Large amounts of radioactivity were recovered from the elongation zone of the root. Some radioactivity also accumulated in the older part of the root with well-developed lateral roots. When [3H]iP was applied one day after decapitation, no significant changes in the pattern of radioactivity distribution were found between the intact and decapitated root systems. However, when applied 7 days after decapitation there was a significant increase of radioactivity in the region of the root where lateral roots were emerging. HPLC separation of extracts from the different root sections showed that [3H]iP was extensively metabolized in the root. Six peaks of radioactivity, which co-chromatographed with authentic cytokinin standards, were detected.Abbreviations ABA
abscisic acid
- ADE
adenine
- IAA
indole-acetic acid
- iP
iso-pentenyladenine
- HPLC
high performance liquid chromatography
- [OG]DHZ
O-glycosyldihydrozeatin
- [9R-MP]DHZ
ribosyldihydrozeatin monophosphate
- [9G]iP
iso-pentenyladenine-9-glucoside
- [9R]Z
ribosylzeatin
- [9R]iP
iso-pentenyladenosine
- TLC
thin layer chromatography 相似文献
83.
Long-term effects of elevated CO2 and nutrients on photosynthesis and rubisco in loblolly pine seedlings 总被引:17,自引:13,他引:4
The effects of long-term CO2 enhancement and varying nutrient availability on photosynthesis and ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) were studied on loblolly pine (Pinus taeda L.) seedlings grown in two atmospheric CO2 partial pressures (35 and 65 Pa) and three nutrient treatments (low N, low P, and high N and P). Measurements taken in late autumn (November) after 2 years of CO2 enrichment and nutrient addition showed that photosynthetic rates were higher for plants grown at elevated CO2 only when they received supplemental N. Total rubisco activity and rubisco content decreased at elevated CO2, but there was an increase in activation state. At elevated CO2, proportionately less N was found in rubisco and more N was found in the light reaction components. These results demonstrate acclimation of photosynthetic processes to elevated CO2 through reallocation of N. Loblolly pine grown in nutrient conditions similar to native soils (low N availability) had lower needle N and chlorophyll content, lower total rubisco activity and content, and lower photosynthetic rates than plants grown at high N and P. This suggests that the magnitude of the photosynthetic response to a future, high-CO2 environment will be dependent on soil fertility in the system. 相似文献
84.
InPinus ponderosa Dougl., application of the cytokinins, benzyladenine and 2-isopentenyl adenine, to excised cotyledons, promoted thein vitro formation of meristematic centers which led to bud and shoot production. Meristematic cells showed plastids with poorly developed thylakoid membranes and rudimentary grana, whereas cells in non-meristematic tissues and in growth regulator free medium, had chloroplasts with well developed inner membranes, and more thylakoid membranes and grana than plastids of meristematic cells. Chlorophyll and six polypeptides associated with photosynthesis were present in lower concentrations in cytokinin-treated cotyledons than in those cultured in growth regulator free medium. Both benzyladenine and 2-isopentenyl adenine are effective in inhibiting the accumulation of at least two photosynthetic polypeptides in the first 24 h in culture. The ability of cotyledons to respond in this way to cytokinins is lost after three days in culture in growth regulator free medium prior to treatment with cytokinin. 相似文献
85.
Felix P. Exkenstien 《Developmental neurobiology》1994,25(11):1467-1480
Fibroblast growth factors (FGFs) exhibit widespread mitogenic and neurotrophic activities. Nine members of the family are currently known, and FGF-1 and FGF-2 are present in relatively high levels in CNS. FGF-1 is expressed by a subset of neuronal populations, while FGF-2 is expressed by astrocytes. FGF-1 and FGF-2 lack signal peptides and appear to be present mainly in inracellular compartmens. This suggests that the factors may act as initiators of a repair response after injury. Support for this notion comes from observations that FGF-1 and FGF-2 levels are low during critical phases of development, but high in the adult CNS. A family of transmembrane tyrosine kinase receptors (FGFRs) mediates the effects of FGFs. Four different genes coding for FGF receptors are currently known, three of which are expressed in cell type-specific patterns in the CNS The main receptor variants present in this tissue, however, can by themselves not distinguish between FGF-1 and FGF-2. Additional selectivity may be established by interaction of the FGFs and their receptors with select heparan proteoglycans (HSPGs). Therefore, the precise physiological role of FGFs is determined by the combination of cell type-specific patterns of expression of FGFs, FGFRs and HSPGs together with the mechanisms that regulate the extracellular availability of FGFs. 1994 John Wiley & Sons, Inc. 相似文献
86.
87.
利用树木年轮气候学方法,根据马尾松生长对气候变量具非线性响应,尝试重建江苏暖湿地区过去116年(1874~1990)的年平均气温和降水量。温度的重建效果优于降水量,实测值与重建值两者的缩减误差(RE)分别为0.12和0.10,两者的平均偏差百分率分别为2.3%和20%。绝大部分重建结果可从观测记录和历史文献中得到验证,但在温度较高或降水量较多的若干年份,实测值与重建值有较大偏差。 相似文献
88.
Low Selenium Diet Affects Monoamine Turnover Differentially in Substantia Nigra and Striatum 总被引:2,自引:1,他引:1
Abstract: Turnover of dopamine, noradrenaline. serotonin, and their metabolites has been measured in striatum and substantia nigra of adult female rats that were fed control or selenium-deficient diets for 15 days. In addition, the glutathione peroxidase activity has been studied. The most striking result was the increase of dopamine turnover (63%) and 3- methoxytyramine turnover (55%) in substantia nigra between control and experimental animals. On the other hand, no changes were found in the turnover rate of dopamine and its metabolites in the striatum. Likewise, no changes were found in noradrenaline turnover in substantia nigra. In the striatum, there was a significant increase of serotonin turnover versus no change for 5-hydroxy-3-indoleacetic acid. However, in the substantia nigra, serotonin turnover did not show significant changes, whereas 5-hydroxy-3-indoleacetic acid turnover decreased. At the same time, glutathione peroxidase activity significantly decreased in both structures after selenium-deficient diets. These results suggest that a selenium-deficient diet for a short period of time decreases brain protection. principally in the substantia nigra, against oxidative damage. 相似文献
89.
Veronique Blanchard Rita Raisman-Vozari Marc Savasta Etienne Hirsch France Javoy-Agid Claude Feuerstein Yves Agid 《Journal of neurochemistry》1993,61(2):617-626
Abstract: We developed a rapid and sensitive radioimmunohistochemical method for the quantification of tyrosine hydroxylase (TH) at both the anatomical and cellular level. Coronal tissue sections from fresh-frozen rat brains were incubated in the presence of a TH monoclonal antibody. The reaction was revealed with a 35 S-labeled secondary antibody. TH content was quantified in catecholaminergic brain areas by measuring optical density on autoradiographic films or silver grain density on autoradiographic emulsion-coated sections. Regional TH concentrations determined in the locus ceruleus (LC), substantia nigra pars compacta (SNC), and ventral tegmental area (VTA) were significantly increased by 45% after reserpine treatment in the LC but unchanged in the SNC and VTA. Microscopic examination of TH radioimmunolabeling showed a heavy accumulation of silver grains over catecholaminergic cell bodies. In the LC, grain density per cell was heterogeneous and higher in the ventral than in the dorsal part of the structure. After reserpine treatment, TH levels were significantly increased (57%) in the neurons of the LC but not in those of the SNC or VTA. The data support the validity of this radioimmunohistochemical method as a tool for quantifying TH protein at the cellular level and they confirm that TH protein content is differentially regulated in noradrenergic and dopaminergic neurons in response to reserpine. 相似文献
90.
The nuclear 18S, 5.8S and 25S rRNA genes exist as thousands of rDNA repeats in the Scots pine genome. The number and location
of rDNA loci (nucleolus organizers, NORs) were studied by cytological methods, and a restriction map from the coding region
of the Scots pine rDNA repeat was constructed using digoxigenin-labeled flax rDNA as a probe. Based on the maximum number
of nucleoli and chromosomal secondary constrictions, Scots pine has at least eight NORs in its haploid genome. The size of
the Scots pine rDNA repeat unit is approximately 27 kb, two- or threefold larger than the typical angiosperm rDNA unit, but
similar in size to other characterized conifer rDNA repeats. The intergenic spacer region (IGS) of the rDNA repeat unit in
Scots pine is longer than 20 kb, and the transcribed spacer regions surrounding the 5.8S gene (ITS1 and ITS2) span a region
of 2.9 kb. Restriction analysis revealed that although the coding regions of rDNA repeats are homogeneous, heterogeneity exists
in the intergenic spacer region between individuals, as well as among the rDNA repeats within individuals. 相似文献