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Environmental influences on the productivity of three desert succulents in the south-western United States 总被引:1,自引:0,他引:1
Abstract Net CO2 uptake over 24 h periods for shoots of Agave deserti, Ferocactus acanthodes, and Opuntia ficus-indica was measured under the ranges of water status, air temperature, and photo-synthetically active radiation (PAR) that occur in the south-western U.S.A. An environmental productivity index (EPI) was constructed indicating the overall influence of these three factors on net CO2 uptake. Using growth chambers whose conditions were changed monthly to simulate the environmental conditions at a field site, the observed shoot dry weight increases per unit surface area changed in concert with monthly changes in EPI. The observed dry weight gain of the shoot was 17–19% lower than the predicted shoot net CO2 uptake, which could be accounted for by carbon diversion to the roots. Mean monthly EPI was also predicted for 21 sites in the south-western U.S.A. All three species had low EPIs in the Colorado River basin, which has low annual rainfall and high summer temperatures, and in the north-central part of the region, which has low temperatures and low PAR during winter when water is available. The two native species, A. deserti and F. acanthodes, had high EPIs beyond their range in coastal southern California, where competition by other vegetation for PAR may limit net CO2 uptake. Such regions as well as south-central California and south-central Arizona had high EPIs for all three species, indicating that these areas would be appropriate for the cultivation of O. ficus-indica. 相似文献
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Diel water movement between parenchyma and chlorenchyma of two desert CAM plants under dry and wet conditions 总被引:3,自引:2,他引:3
Abstract. Electric-circuit analogue models of the water relations of crassulacean acid metabolism (CAM) succulents such as Agave deserti and Ferocactus acanthodes have predicted diel movement of water between the water-storage parenchyma and the photo-synthetic chlorenchyma. Injection of tritiated water into either tissue in the laboratory confirmed substantial and bidirectional water movements, especially under conditions of wet soil. For A. deserti , water movement from the water-storage parenchyma to the chlorenchyma increased at night as the chlorenchyma osmotic pressure increased. Although nocturnal osmotic pressure increases and transpiration for both species were minimal in the field under dry conditions, diel changes in the deuterium: hydrogen ratio (expressed as ΔD) were similar for the water-storage parenchyma and the chlorenchyma. Such indication of [substantial mixing of water between the tissues over a 24-h cycle was more evident under wet conditions in the field. For A. deserti , ΔD then increased by 32%o from the afternoon to midnight and was essentially identical in the water-storage parenchyma and the chlorenchyma. For F. acanthodes , the diel changes in ΔD were one-third those of A. deserti , and ΔD was always slightly higher for the chlorenchyma than for the water-storage parenchyma, apparently reflecting the lower surface-to-volume ratio of A. deserti. In summary, data obtained using radioactive and stable isotopes strongly supported model predictions concerning diel cycles of internal water distribution for these CAM species. 相似文献
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Nobel P 《American journal of botany》1997,84(7):949-955
To investigate root distribution with depth, which can affect competition for water, surface areas of young and old roots were determined in 4-cm-thick soil layers for the C3 subshrub Encelia farinosa Torrey and A. Gray, the C4 bunchgrass Pleuraphis rigida Thurber, and the CAM (crassulacean acid metabolism) leaf succulent Agave deserti Engelm. At a site in the northwestern Sonoran Desert these codominant perennials had mean rooting depths of only 9-10 cm for isolated plants. Young roots had mean depths of 5-6 cm after a winter wet period, but 11-13 cm after a summer wet period. Young roots were most profuse in the winter for E. farinosa, which has the lowest optimum temperature for root growth, and in the summer for P. rigida, which has the highest optimum temperature. Roots for interspecific pairs in close proximity averaged 2-3 cm shallower for A. deserti and a similar distance deeper for the other two species compared with isolated plants, suggesting partial spatial separation of their root niches when the plants are in a competitive situation. For plants with a similar root surface area, the twofold greater leaf area and twofold higher maximal transpiration rate of E. farinosa were consistent with its higher root hydraulic conductivity, leading to a fourfold higher estimated maximal water uptake rate than for P. rigida. Continuous water uptake accounted for the shoot water loss by A. deserti, which has a high shoot water-storage capacity. A lower minimum leaf water potential for P. rigida than for A. deserti indicates greater ability to extract water from a drying soil, suggesting that temporal niche separation for water uptake also occurs. 相似文献
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《植物学报(英文版)》2005,47(3)
A better understanding of the mechanisms of water uptake by plant roots should be vital for improving drought resistance and water use efficiency (WUE). In the present study, we have demonstrated correlations between root system hydraulic conductivity and root characteristics during evolution using six wheat evolution genotypes (solution culture) with different ploidy chromosome sets (Triticum boeoticum Bioss., T. monococcum L.: 2n = 2x = 14; T. dicoccides Koern., T. dicoccon (Schrank) Schuebl.: 2n = 4x = 28;T. vulgare Vill., T. aestivum L. cv. Xiaoyan No. 6: 2n = 6x = 42). The experimental results showed that significant correlations were found between root system hydraulic conductivity and root characteristics of the materials with the increase in ploidy chromosomes (2x→6x) during wheat evolution. Hydraulic conductivity of the wheat root system at the whole-plant level was increased with chromosome ploidy during evolution, which was positively correlated with hydraulic conductivity of single roots, whole plant biomass,root average diameter, and root growth (length, area), whereas the root/shoot ratio had an inverse correlation with the hydraulic conductivity of root system with increasing chromosome ploidy during wheat evolution. Therefore, it is concluded that that the water uptake ability of wheat roots was strengthened from wild to modern cultivated species during evolution, which will provide scientific evidence for genetic breeding to improve the WUE of wheat by genetic engineering. 相似文献
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Water uptake and structural plasticity along roots of a desert succulent during prolonged drought 总被引:3,自引:0,他引:3
Desert succulents resume substantial water uptake within 1–2 d of the cessation of drought, but the changes in root structure and hydraulic conductivity underlying such recovery are largely unknown. In the monocotyledonous leaf succulent Agave deserti Engelm. substantial root mortality occurred only for lateral roots near the soil surface; nearly all main roots were alive at 180 d of drought. New main roots were initiated and grew up to 320 mm at soil water potentials lower than – 5·0 MPa, utilizing water from the shoot. The hydraulic conductivity of distal root regions decreased 62% by 45 d of drought and 70% thereafter. After 7 d of rewetting, root hydraulic conductivity was restored following 45 d of drought but not after 90 and 180 d. The production of new lateral roots and the renewed apical elongation of main roots occurred 7–11 d after rewetting following 180 d of drought. Hydraulic conductivity was higher in the distal region than at midroot and often increased again near the root base, where many endodermal cells lacked suberin lamellae. Suberization and xylem maturation were influenced by the availability of moisture, suggesting that developmental plasticity along a root allows A. deserti to capitalize on intermittent or heterogeneous supplies of water. 相似文献
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Induction of rooting in the microshoots of Plumbago zeylanica was achieved on halfstrength basal Murashige and Skoog's medium supplemented with 0.25 mg dm–3 indole-3-butyric acid. Rooting was totally inhibited when the microshoots were cultured in vitro under continuous light, however, maximum percentage of microshoots rooted when incubated in continuous light for 4 weeks before transfer to the rooting media. Peroxidase activity increased markedly during root induction indicating a key role of peroxidase in rooting of microshoots of Plumbago zeylanica in vitro. 相似文献
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Aurélie Vocanson Jean Roger-Estrade Hubert Boizard Marie-Hélène Jeuffroy 《Plant and Soil》2006,281(1-2):121-135
Spring peas are known to be very sensitive to compaction, particularly when sowing takes place soon after winter. Winter peas, which are sown in autumn, should present an opportunity to sow the crop in better soil structural conditions than for spring peas, because of more favourable moisture conditions at that time. As environmental conditions have a big influence on root systems, it is important to determine the effects of soil structure on pea root systems for different cultivars and sowing dates. A spring pea cultivar and a winter pea cultivar were both sown at two dates (one in autumn and one in spring) on soils with different plough-layer structures (compacted and uncompacted) at two sites in 2002 and one site in 2003. Soil structure was characterised by bulk density and the percentage of highly compacted zones in the ploughed layer. Root distribution maps were produced every month, from February to maturity. Root development was described in terms of general root dynamics, root elongation rate (RER) in the subsoil, final maximum root depth (Dmax) and root distribution at maturity. Root depth dynamics depended on compaction and its interaction with climatic conditions. The effects of compaction on RER in the subsoil depended on the experimental conditions. Dmax was reduced by 0.10 m by compaction. Compaction also reduced root distribution between 10 and 40% in the ploughed layer only. Pea cultivars differed in sensitivity to soil compaction, with a direct effect on the final depth explored by roots. These results are discussed in terms of their relevance to water and nutrient uptake. 相似文献
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High-Temperature Preconditioning and Thermal Shock Imposition Affects Water Relations,Gas Exchange and Root Hydraulic Conductivity in Tomato 总被引:4,自引:0,他引:4
D. Morales P. Rodríguez J. Dell'Amico E. Nicolás A. Torrecillas M.J. Sánchez-Blanco 《Biologia Plantarum》2003,47(2):203-208
Potted tomato plants (Lycopersicon esculentum Mill. cv. Amalia) were submitted to three different treatments: control (C) plants were maintained at day/night temperature
of 25/18 °C; preconditioned plants (PS) were submitted to two consecutive periods of 4 d each, of 30/23 and 35/28 °C before
being exposed to a heat stress (40/33 °C lasting 4 d) and non-preconditioned (S) plants were maintained in the same conditions
as the C plants and exposed to the heat stress. The inhibition of plant growth was observed only in PS plants. Heat stress
decreased chlorophyll content, net photosynthetic rate and stomatal conductance in both PS and S plants. However, PS plants
showed good osmotic adjustment, which enabled them to maintain leaf pressure potential higher than in S plants. Furthermore,
at the end of the recovery period PS plants had higher pressure potential and stomatal conductance than in S plants.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Water flow and water storage in Agave deserti: osmotic implications of crassulacean acid metabolism 总被引:1,自引:4,他引:1
Abstract Water flow and water storage were investigated for Agave deserti, a desert succulent showing crassulacean acid metabolism (CAM). The anatomy and water relations of the peripheral chlorenchyma, where CAM occurs, and the central water-storage parenchyma were investigated for its massive leaves so that these tissues could be incorporated as discrete elements into an electrical-circuit analogue of the whole plant. The daily cycling of osmotic pressure was represented by voltage sources in series with the storage capacitors. With soil water potential and leaf transpiration rate as input variables, axial water flow through the vascular bundles and radial flows into and out of storage during the day/night cycle were determined. The predominantly nocturnal transpiration was coincident with increases in cell osmotic pressure and in titratable acid of the leaf chlorenchyma. In the outer layers of the chlorenchyma, water potential was most negative at the beginning of the night when transpiration was maximum, while the water-storage parenchyma reached its minimal water potential 9 h later. The roots plus stem contributed 7% and the leaves contributed 50% to the total water flow during maximal transpiration; peak water flow from the soil to the roots occurred at dawn and was only 58% of the maximal transpiration rate. Over each 24-h period, 39% of the water lost from the plant was derived from storage, with flow into storage occurring mainly during the daytime. Simulations showed that the acid accumulation rhythm of CAM had little impact on water uptake from the soil under the conditions employed. In the outer chlorenchyma, water potential and water flows were more sensitive to the day/night changes in transpiration than in osmotic pressure. Nevertheless, cell osmotic pressure had a large influence on turgor pressure in this tissue and determined the extent to which storage was recharged during the latter part of the night. 相似文献
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Influences of Root Diameter, Tree Age, Soil Depth and Season on Fine Root Survivorship in Prunus avium 总被引:2,自引:0,他引:2
The rapid turnover of the fine root system is a major pathway of carbon and nutrient flow from plant to soil in forest ecosystems.
In order to quantify these fluxes there is a need to understand how fine root demography is influenced by edaphic, environmental
and plant ontogenetic factors. We studied the influence of four major factors (season, depth, root diameter and tree age)
on the survivorship and longevity of fine roots of Prunus avium L. (wild cherry) over two years in North East Scotland. Survival analysis of data derived from minirhizotron observations
showed that, for the range of root diameters studied, an increase in root diameter of 0.1 mm was associated with a 16% decrease
in the risk of death. Depth was also an important factor; roots present at a depth of 10 cm had significantly lower survivorship
than did roots at all lower depths studied. The effects of tree age and season on root production were more complex. Roots
of old trees were more likely to die in the spring and roots of young trees were more likely to die in the autumn. Our data
illustrate the complex factors that must be taken into account when scaling up information from individual observations of
root longevity to model the contribution of fine roots to C and nutrient fluxes in forest ecosystems. 相似文献
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菜豆根构型对低磷胁迫的适应性变化及基因型差异 总被引:48,自引:0,他引:48
利用特殊设计的营养袋纸培养和分层式磷控释砂培等根系生长系统结合计算机图像分析技术,以基根根长在生长介质各层的相对分布和基根平均生长角度为指标,定量测定菜豆(Phaseolus vulgaris L.)根构型在低磷胁迫下的适应性变化及其与磷效率的关系。结果表明,菜豆根构型对低磷胁迫具有适应性反应,在缺磷条件下基根向地性减弱,基根在生长介质表层相对分布增多、基根平均生长角度(与水平线夹角)变小,从而导 相似文献
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The arrest of DNA synthesis and termination of cell division in basal meristematic cells as well as the resumption of these processes as related to the initiation of lateral root primordia (LRP) were studied in tissues of Triticum aestivumroots incubated with 3H-thymidine. All cells of the stelar parenchyma and cortex as well as most endodermal and pericycle cells left the mitotic cycle and ceased proliferative activity at the basal end of the meristem and at the beginning of the elongation zone. Some endodermal and pericycle cells started DNA synthesis in the basal part of the meristem and completed it later on during their elongation, but they did not divide. In the cells of these tissues, DNA synthesis resumed above the elongation zone, the cells being located much closer to the root tip than the first newly dividing cells. Thus, the initiation of LRP started much closer to the root tip than it was previously believed judging from the distance of the first dividing pericycle cells from the root tip. DNA synthesizing and dividing cells first appeared in the stelar parenchyma, then, in the pericycle, and later, in the endodermis and cortex. It seems likely that a release from the inhibition of DNA synthesis allows the cells that completed mitotic cycle in the basal part of meristem in the G1phase to cease the proliferative arrest above the elongation zone and to continue their cycling. The location of the first DNA synthesizing and dividing cells in the stelar parenchyma and pericycle did not strictly correspond to the LRP initiation sites and proximity to the xylem or phloem poles. This indicates that LRP initiation results from the resumption of DNA synthesis in all pericycle and stelar parenchyma cells that retained the ability to synthesize DNA and occurs only in the pericycle sector situated between the two tracheal protoxylem strands, all cells of which terminated their mitotic cycles in the G1phase. 相似文献
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The relationship between shoot hydraulic conductance (L) and stomatal sensitivity to changes in leaf water status was studied in the saplings of six deciduous tree species. L increased significantly in sequence: Acer platanoides < Tilia Cordata < Padus avium = Quercus robur < Salix caprea = Populus tremula. L was higher in the trees grown in soil with a higher nitrogen content and lower in the trees grown under mild water stress or kept in darkness for several days. L was higher in July than in September in all the species. L correlated positively with maximum photosynthesis, stomatal conductance and stomatal sensitivity to an increase in leaf water potential, but negatively with stomatal sensitivity to a decrease in leaf water potential. The correlations between L and any other parameter were approximated by three different curves: data for water-stressed plants fit to the first, data for plants kept in darkness fit to the second and all the other data fit to the third curve. The reasons of the differences of shoot hydraulic conductance in the different experimental sets and the mechanisms which may cause the correlation between L and the other characteristics are discussed. 相似文献
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The beta-ray gauging technique was used to measure the relativechanges occurring in the water content of sour orange and sweetlime leaves as a result of soil wetting and drying cycles. Promethium-147served as the radiation source and was found suitable for measuringchanges in citrus leaf thickness within the range of 20 mg/cm2(when soil moisture content was at pot capacity)to 10 mg/cm2 (when soil moisture dropped to wilting point).By using the correlation between beta-ray gauging measurements,leaf thickness, and relative turgidity, it is possible to determinethe status of water in citrus leaves under different soil moistureconditions. 相似文献
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营养生长期植物冠根比及其对环境因子的响应 总被引:1,自引:0,他引:1
将光强、温度和土壤水势等环境因子对植物光合、呼吸、同化物运输及生长等生理过程的影响结合起来,并考虑到各生理过程之间的交互作用,建立了一个营养生长期内植物条根比变化及对环境因子综合响应的模型。模型的运行结果表明,该模型与许多实验现象均相吻合。 相似文献
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Aim The interactions between primary sensory neurons and cardiac myocytes are still unclear. In the present study, the co-culture
model of dorsal root ganglion (DRG) explant and cardiac myocytes was used to characterize the morphological relationship between
primary sensory nerve endings and cardiac myocytes and to investigate whether cardiac myocytes could induce substance P (SP)
and calcitonin gene-related peptide (CGRP) synthesis in DRG neurons and release from DRG neurons in the neuromuscular co-cultures.
Methods The formation of neuromuscular junctions was observed with scanning electron microscopy (SEM). SP and CGRP expression were
detected by immunocytochemistry. Basal SP and CGRP release and capsaicin-evoked SP and CGRP release were analyzed by radioimmunoassay
(RIA). Results In this study, neuromuscular junctions were observed in the co-cultures of DRG explant and cardiac myocytes. SP-immunoreactive
(IR) and CGRP-IR neurons were detected in both neuromuscular co-cultures and DRG explant cultures, but the number of SP-IR
and CGRP-IR neurons migrating from DRG explant was significantly increased in neuromuscular co-cultures. Capsaicin-evoked
SP and CGRP release but not basal SP and CGRP release in neuromuscular co-cultures increased significantly as compared with
that in the cultures of DRG explant alone. Conclusions The results implicated that the morphological relationship between sensory nerve terminal and cardiac myocyte is much more
close in vitro than it is in vivo. Cardiac myocytes may induce sensory neuropeptide synthesis and capsaicin-evoked neuropeptide
release in neuromuscular co-cultures. Further experiment needs to be performed about the significance of neuropeptide synthesis
and capsaicin-evoked neuropeptide release induced by target cardiac myocytes.
Zhen Liu and Huaxiang Liu contributed equally to this article. 相似文献
20.
Novel Methods of Measuring Hydraulic Conductivity of Tree Root Systems and Interpretation Using AMAIZED (A Maize-Root Dynamic Model for Water and Solute Transport) 总被引:3,自引:0,他引:3
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Steady-state and dynamic methods were used to measure the conductivity to water flow in large woody root systems. The methods were destructive in that the root must be excised from the shoot but do not require removal of the root from the soil. The methods involve pushing water from the excised base of the root to the apex, causing flow in a direction opposite to that during normal transpiration. Sample data are given for two tropical (Cecropia obtusifolia and Lacistema aggregatum) and two temperate species (Acer saccharum and Juglans regia cv Lara). A hysteresis was observed in the relationship between applied pressure and resulting flow during dynamic measurements. A mathematical model (AMAIZED) was derived for the dynamics of solute and water flow in roots. The model was used to interpret results obtained from steady-state and dynamic measurements. AMAIZED is mathematically identical with the equations that describe Munch pressure flow of solute and water in the phloem of leaves. Results are discussed in terms of the predictions of AMAIZED, and suggestions for the improvement of methods are made. 相似文献