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1.
Downward flux of water through roots (i.e. inverse hydraulic lift) in dry Kalahari sands 总被引:17,自引:0,他引:17
E.-D. Schulze M. M. Caldwell J. Canadell H. A. Mooney R. B. Jackson D. Parson R. Scholes O. E. Sala P. Trimborn 《Oecologia》1998,115(4):460-462
Downward transport of water in roots, in the following termed “inverse hydraulic lift,” has previously been shown with heat
flux techniques. But water flow into deeper soil layers was demonstrated in this study for the first time when investigating
several perennial grass species of the Kalahari Desert under field conditions. Deuterium labelling was used to show that water
acquired by roots from moist sand in the upper profile was transported through the root system to roots deeper in the profile
and released into the dry sand at these depths. Inverse hydraulic lift may serve as an important mechanism to facilitate root
growth through the dry soil layers underlaying the upper profile where precipitation penetrates. This may allow roots to reach
deep sources of moisture in water-limited ecosystems such as the Kalahari Desert.
Received: 1 January 1998 / Accepted: 1 April 1998 相似文献
2.
Joseph J. Hendricks John D. Aber Knute J. Nadelhoffer Richard D. Hallett 《Ecosystems》2000,3(1):57-69
Nitrogen controls on fine root substrate quality (that is, nitrogen and carbon-fraction concentrations) were assessed using
nitrogen availability gradients in the Harvard Forest chronic nitrogen addition plots, University of Wisconsin Arboretum,
Blackhawk Island, Wisconsin, and New England spruce-fir transect. The 27 study sites encompassed within these four areas collectively
represented a wide range of nitrogen availability (both quantity and form), soil types, species composition, aboveground net
primary production, and climatic regimes. Changes in fine root substrate quality among sites were most frequently and strongly
correlated with nitrate availability. For the combined data set, fine root nitrogen concentration increased (adjusted R
2 = 0.46, P < 0.0001) with increasing site nitrate availability. Fine root “extractive” carbon-fraction concentrations decreased (adjusted
R
2 = 0.32, P < 0.0002), “acid-soluble” compounds increased (adjusted R
2 = 0.35, P < 0.0001), and the “acid-insoluble” carbon fraction remained relatively high and stable (combined mean of 48.7 ± 3.1% for
all sites) with increasing nitrate availability. Consequently, the ratio of acid-insoluble C–total N decreased (adjusted R
2 = 0.40, P < 0.0001) along gradients of increasing nitrate availability. The coefficients of determination for significant linear regressions
between site nitrate availability and fine root nitrogen and carbon-fraction concentrations were generally higher for sites
within each of the four study areas. Within individual study sites, tissue substrate quality varied between roots in different
soil horizons and between roots of different size classes. However, the temporal variation of fine root substrate quality
indices within specific horizons was relatively low. The results of this study indicate that fine root substrate quality increases
with increasing nitrogen availability and thus supports the substrate quality component of a hypothesized conceptual model
of nitrogen controls on fine root dynamics that maintains that fine root production, mortality, substrate quality, and decomposition
increase with nitrogen availability in forest ecosystems in a manner that is analogous to foliage. 相似文献
3.
Hydraulic lift: consequences of water efflux from the roots of plants 总被引:29,自引:0,他引:29
Hydraulic lift is the passive movement of water from roots into soil layers with lower water potential, while other parts
of the root system in moister soil layers, usually at depth, are absorbing water. Here, we review the brief history of laboratory
and field evidence supporting this phenomenon and discuss some of the consequences of this below-ground behavior for the ecology
of plants. Hydraulic lift has been shown in a relatively small number of species (27 species of herbs, grasses, shrubs, and
trees), but there is no fundamental reason why it should not be more common as long as active root systems are spanning a
gradient in soil water potential (Ψs) and that the resistance to water loss from roots is low. While the majority of documented cases of hydraulic lift in the
field are for semiarid and arid land species inhabiting desert and steppe environments, recent studies indicate that hydraulic
lift is not restricted to these species or regions. Large quantities of water, amounting to an appreciable fraction of daily
transpiration, are lifted at night. This temporary partial rehydration of upper soil layers provides a source of water, along
with soil moisture deeper in the profile, for transpiration the following day and, under conditions of high atmospheric demand,
can substantially facilitate water movement through the soil-plant-atmosphere system. Release of water into the upper soil
layers has been shown to afford the opportunity for neighboring plants to utilize this source of water. Also, because soils
tend to dry from the surface downward and nutrients are usually most plentiful in the upper soil layers, lifted water may
provide moisture that facilitates favorable biogeochemical conditions for enhancing mineral nutrient availability, microbial
processes, and the acquisition of nutrients by roots. Hydraulic lift may also prolong or enhance fine-root activity by keeping
them hydrated. Such indirect benefits of hydraulic lift may have been the primary selective force in the evolution of this
process. Alternatively, hydraulic lift may simply be the consequence of roots not possessing true rectifying properties (i.e.,
roots are leaky to water). Finally, the direction of water movement may also be downward or horizontal if the prevailing Ψs gradient so dictates, i.e., inverse, or lateral, hydraulic lift. Such downward movement through the root system may allow
growth of roots in otherwise dry soil at depth, permitting the establishment of many phreatophytic species.
Received: 2 June 1997 / Accepted: 24 September 1997 相似文献
4.
Yingxin Huang Xueyong Zhao Hongxuan Zhang Wisdom Japhet Xiaoan Zuo Yayong Luo Gang Huang 《Journal of Plant Biology》2009,52(3):210-219
We monitored the allometric effects for greenhouse-grown Agriophyllum squarrosum plants in response to variations in population density and the availability of soil nutrients and water. Biomass allocations
were size-dependent. The plasticity of roots, stems, leaves, and reproductive effort was “true” in response to changes in
nutrient content. At a low level of soil minerals, plants allocated more resources to the development of roots and reproductive
organs than to leaves, but data for stem allocations were consistent for tradeoffs between the effects of nutrients and plant
size. The plasticities of leaf allocation and reproductive effort were “true” whereas those of root and stem allocations were
“apparent” in response to fluctuations in soil water, being a function of plant size. Decreasing soil water content was associated
with higher leaf allocation and lower reproductive effort. Except for this “apparent” plasticity of leaf allocation, none
was detected with population density on biomass allocation. Architectural traits were determinants of the latter. For roots,
the determining trait was the ratio of plant height to total biomass; for stems and reproduction, plant height; and for leaves,
the ratio of branch numbers to plant height. 相似文献
5.
The importance of root gravitropism for inter-root competition and phosphorus acquisition efficiency: results from a geometric simulation model 总被引:15,自引:1,他引:14
We have observed that low soil phosphorus availability alters the gravitropic response of basal roots in common bean (Phaseolus vulgaris L.), resulting in a shallower root system. In this study we use a geometric model to test the hypotheses that a shallower
root system is a positive adaptive response to low soil P availability by (1) concentrating root foraging in surface soil
horizons, which generally have the highest P availability, and (2) reducing spatial competition for P among roots of the same
plant. The growth of nine root systems contrasting in gravitropic response over 320 h was simulated in SimRoot, a dynamic three-dimensional geometric model of root growth and architecture. Phosphorus acquisition and inter-root competition
were estimated with Depzone, a program that dynamically models nutrient diffusion to roots. Shallower root systems had greater P acquisition per unit
carbon cost than deeper root systems, especially in older root systems. This was due to greater inter-root competition in
deeper root systems, as measured by the volume of overlapping P depletion zones. Inter-root competition for P was a significant
fraction of total soil P depletion, and increased with increasing values of the P diffusion coefficient (De), with root age, and with increasing root gravitropism. In heterogenous soil having greater P availability in surface horizons,
shallower root systems had greater P acquisition than deeper root systems, because of less inter-root competition as well
as increased root foraging in the topsoil. Root P acquisition predicted by SimRoot was validated against values for bean P
uptake in the field, with an r
2 between observed and predicted values of 0.75. Our results support the hypothesis that altered gravitropic sensitivity in
P-stressed roots, resulting in a shallower root system, is a positive adaptive response to low P availability by reducing
inter-root competition within the same plant and by concentrating root activity in soil domains with the greatest P availability.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
Transverse hydraulic redistribution by a grapevine 总被引:4,自引:0,他引:4
Root hydraulic redistribution has been shown to occur in numerous plant species under both field and laboratory conditions. To date, such water redistribution has been demonstrated in two fundamental ways, either lifting water from deep edaphic sources to dry surface soils or redistributing water downward (reverse flow) when inverted soil Ψs gradients exist. The importance of hydraulic redistribution is not well documented in agricultural ecosystems under field conditions, and would be important because water availability can be temporally and spatially constrained. Herein we report that a North American grapevine hybrid (Vitis riparia × V. berlandieri cv 420 A) growing in an agricultural ecosystem can redistribute water from a restricted zone of available water under a drip irrigation emitter, laterally across the high resistance pathways of the trunk and into roots and soils on the non-irrigated side. Deuterium-labelled water was used to demonstrate lateral movement across the vine's trunk and reverse flow into roots. Water redistribution from the zone of available water and into roots distant from the source occurred within a relatively short time frame of 36 h, although overnight deposition into rhizosphere soils around the roots was not detected. Deuterium was eventually detected in rhizosphere soils adjacent to roots on the non-irrigated side after 7 d. Application of identical amounts of water with the same deuterium enrichment level (2%) to soils without grapevine roots showed that physical transport of water through the vapour phase could not account for either downward or transverse movement of the label. These results confirmed that root presence facilitated the transport of label into soils distant from the wetted zone. When deuterium-labelled water was allowed to flow directly into the trunk above the root–trunk interface, reverse flow occurred and lateral movement across the trunk and into roots originating around the collar region did not encounter large disproportionate resistances. Rapid redistribution of water into the entire root system may have important implications for woody perennial cultivars growing where water availability is spatially heterogeneous. Under the predominantly dry soil conditions studied in this investigation, water redistributed into roots may extend root longevity and increase the vines water capacitance during periods of high transpiration demand. These benefits would be enhanced by diminished water loss from roots, and could be equally important to other cited benefits of hydraulic redistribution into soils such as enhancement of nutrient acquisition. 相似文献
7.
The role of roots penetrating various undisturbed soil horizons beneath loose layer in water use and shoot growth of maize
was evaluated in greenhouse experiment. 18 undisturbed soil columns 20 cm in diameter and 20 cm in height were taken from
the depths 30–50 cm and 50–70 cm from a Brown Lowland soil, a Pseudogley and a Brown Andosol (3 columns from each depth and
soil). Initial resistance to penetration in undisturbed soil horizons varied from 2.5 to 8.9 MPa while that in the loose layer
was 0.01 MPa. The undisturbed horizons had a major effect on vertical arrangement of roots. Root length density in loose layer
varied from 96 to 126 km m-3 while in adjacent stronger top layers of undisturbed horizons from 1.6 to 20.0 km m-3 with higher values in upper horizons of each soil. For specific root length, the corresponding ranges were 79.4–107.7 m g-1 (on dry basis) and 38.2–63.7 m g-1, respectively. Ratios of root dry weight per unit volume of soil between loose and adjacent undisturbed layers were much
lower than those of root length density indicating that roots in undisturbed horizons were produced with considerably higher
partition of assimilates. Root size in undisturbed horizons relative to total roots was from 1.1 to 38.1% while water use
from the horizons was from 54.1 to 74.0%. Total water use and shoot growth were positively correlated with root length in
undisturbed soil horizons. There was no correlation between shoot growth and water use from the loose layers. 相似文献
8.
We present a simple framework for modelling root growth and distribution with depth under varying soil water conditions. The framework considers the lateral growth of roots (proliferation) and the vertical extension of roots (root front velocity). The root front velocity is assumed to be constant when the roots descend into an initially wet soil profile. The lateral growth of roots is governed by two factors: (1) the current root mass or root length density at a given depth, and (2) soil water availability at that depth.Under non-limiting soil water conditions, the increase in root mass at any depth is governed by a logistic equation so that the root length density (R
v) cannot exceed the maximum value. The maximumR
v, is assumed to be the same for all depths. Additional dry matter partitioned to roots is initially distributed according to the current root mass at each depth. As the root mass approaches the maximum value, less dry matter is partitioned to that depth.When soil water is limiting, a water deficit factor is introduced to further modify the distribution of root dry matter. It is assumed that the plant is an energy minimiser so that more root mass is partitioned to the wetter regions of the soil where least energy will be expended for root growth. Hence, the model allows for enhanced root growth in areas where soil water is more easily available.Simulation results show that a variety of root distribution patterns can be reproduced due to varying soil water conditions. It has been demonstrated that broad patterns of root distribution reported in the literature can also be simulated by the model. 相似文献
9.
Water relations and root activities of Buchloe dactyloides and Zoysia japonica in response to localized soil drying 总被引:5,自引:0,他引:5
Effects of localized soil drought stress on water relations, root growth, and nutrient uptake were examined in drought tolerant
‘Prairie’ buffalograss [Buchloe dactyloides (Nutt.) Engelm.] and sensitive ‘Meyer’ zoysiagrass (Zoysia japonica Steud.). Grasses
were grown in small rhizotrons in a greenhouse and subjected to three soil moisture regimes: (1) watering the entire 80-cm
soil profile (well-watered control); (2) drying 0–40 cm soil and watering the lower 40 cm (partially dried); (3) and drying
the entire soil profile (fully dried). Drying the 0–40 cm soil for 28 days had no effect on leaf water potential (Ψ
leaf
) in Prairie buffalograss compared to the well-watered control but reduced that in Meyer zoysiagrass. Root elongation rate
was greater for Prairie buffalograss than Meyer zoysiagrass under well-watered or fully dried conditions. Rooting depth increased
with surface soil drying; with Prairie buffalograss having a larger proportion of roots in the lower 40 cm than Meyer zoysiagrass.
The higher rates of water uptake in the deeper soil profile in the partially dried compared to the well-watered treatment
and by Prairie buffalograss compared to Meyer zoysiagrass could be due to differences in root distribution. Root 15N uptake for Prairie buffalograss was higher in 0–20 cm drying soil in the partially dried treatment than in the fully dried
treatment. Diurnal fluctuations in soil water content in the upper 20 cm of soil when the lower 40 cm were well-watered indicated
water efflux from the deeper roots to the drying surface soil. This could help sustain root growth, maintain nutrient uptake
in the upper drying soil layer, and prolong turfgrass growth under localized drying conditions, especially for the deep-rooted
Prairie buffalograss.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
10.
Root dynamics of Melaleuca halmaturorum in response to fluctuating saline groundwater 总被引:1,自引:0,他引:1
Melaleuca halmaturorum is a salt and waterlogging tolerant tree and thus often occurs in saline areas fringing permanent wetlands and in ephemeral swamps. The dominance of this tree in natural groundwater discharge areas may result in M. halmaturorum transpiration making a major contribution to groundwater discharge. To quantify this the seasonal changes in tree water sources in response to fluctuating soil salinity and waterlogging were examined. This study was conducted in a natural system where seasonally fluctuating saline groundwater (64 dS m–1; 0.3–1.2 m deep) allowed the patterns of M. halmaturorum root water uptake to be followed over a 15 month period. Tree water sources were examined using the naturally occurring stable isotopes of water, while new root growth was examined using a field root observation window and from soil cores. The presence of isotopic fractionation of 2H under conditions of soil salinity and waterlogging was tested in a glasshouse experiment. Measurements of soil and leaf water potential were also made to examine the possible water sources and limits to water uptake. No isotopic fractionation was found by tree roots under conditions of salinity and waterlogging. M. halmaturorum trees were active in taking up groundwater at most times and combined this with a shallower soil water source replenished by rainfall in winter. Water uptake was concentrated in the deeper parts of the soil profile when the groundwater was at its deepest and salt had accumulated in the surface soils, at the end of summer. When groundwater rose, at the end of winter, roots responded by extracting water from near the soil surface (0–0.1 m), at the new watertable. This pattern of water uptake in response to groundwater fluctuations and salt accumulation in the surface soil was also reflected in new root tip appearance at the root observation window. Fluctuations in leaf water potential fallowed fluctuations in surface soil (0.1 m depth) water potential at all times. In winter leaf water potential reflected the absolute values of the surface soil water potential but in summer it was between surface soil and groundwater water potentials. We conclude that M. halmaturorum used groundwater in summer and a combination of rainfall and groundwater from the surface soils in winter. The ability to take up water from saline substrates through the maintenance of low leaf water potential, combined with this ability to rapidly alter root water uptake in response to changes in soil water availability contributed to the survival of M. halmaturorum in this saline swamp. 相似文献
11.
Patchy desert shrubs magnify the horizontal heterogeneities of carbon source and nutrient availability in an arid ecosystem,
significantly affecting the abundance and activity of the soil microbial community. Since each shrub species develops special
ecophysiological adaptations to the extreme harsh desert environments, previous studies elucidated that the effects of perennial
shrubs on microbial diversity are unequal. The aim of the present study, conducted in the Negev Desert, Israel, was to illustrate
the vertical changes of soil microbial community functionality in the root zone of perennial shrubs. Soil samples were collected
from the 0–50 cm depth at 10-cm intervals under the canopy of Zygophyllum dumosum, Hammada scoparia, and from the open spaces between them, in the wet and dry seasons. Soil moisture and organic matter exhibited a significant
(P < 0.001) plant and depth dependence. The mean basal respiration rates and microbial biomass in soils collected beneath perennial
shrubs were relatively higher than the control during the wet season, however, a contrasting trend was observed at some soil
depths during the dry season. Relatively high abundance and activity of aromatic and carboxylic acid utilizers were observed
in the vicinity of perennial shrubs, and the values recorded during the dry season were generally higher than the corresponding
values during the wet season. In addition, a “mirror effect” in vertical changes of the community-level physiological profile
was observed between Z. dumosum and H. scoparia. This study demonstrated the stratification of the functional aspects in soils under the canopy of perennial shrubs, thus
indicating that the scattered distribution of vegetation not only causes horizontal heterogeneities of the microbial community
in an arid system, but also that the ecophysiological adaptations developed by xerophytes regulate the abundance and saprotrophic
functionality of microorganisms in the root zone. 相似文献
12.
Keirith A. Snyder Jeremy J. James James H. Richards Lisa A. Donovan 《Plant and Soil》2008,306(1-2):159-166
Water movement from roots to soil at night in the process of hydraulic lift (redistribution) rehydrates the rhizosphere and
has been proposed to improve plant nutrient acquisition. Another process that has now been found in many plant species is
nighttime transpiration and this could also affect nutrient relations by influencing supply of mobile nutrients to roots at
night. The effects of these soil/root water relations interactions have not been adequately tested. We chose ten Sarcobatus vermiculatus (Hook.) Torrey shrubs with different magnitudes of hydraulic lift (i.e. diel range in soil water potential) to test the hypothesis
that the magnitude of lift would be positively related to the amount of nitrogen (N) uptake over a period of days. A 15N tracer was injected in the 20–30 cm soil layer at locations with hydraulic lift to determine plant 15N acquisition by shallow roots conducting hydraulic lift. Half of the plants were also placed in large humidified tents (i.e.
“bagged”), which suppressed nighttime transpiration, and thus were expected to have greater magnitudes of hydraulic lift,
although they did not. All plants took up the 15N tracer, but contrary to our hypothesis the magnitude of hydraulic lift had no significant effect on the amount of 15N acquired over a 9-day period following labeling. However, plants that were bagged tended to have lower 15N acquisition (P = 0.07). These data indicate that decreased nighttime transpirational water loss or some other effect of bagging may decrease
nutrient acquisition by these nutrient-limited phreatophytic shrubs and more generally suggests a possible nutritional benefit
of nighttime transpiration by plants. This suggestion needs more thorough testing to elucidate an important potential link
between plant water and nutrient relations. 相似文献
13.
You-Cai Xiong Feng-Min Li Bing-Cheng Xu Kenneth C. Hodgkinson 《Journal of Plant Growth Regulation》2006,25(2):120-136
Absract Non-hydraulic root-sourced signal (NRS) is so far affirmed to be a unique “early-warning” response to soil drying in plants,
but little is known about the quantitative effect of this early-warning mechanism on crop production. To evaluate the link
of NRS to a drought tolerance profile, a pot-culture study was carried out in a plant growth chamber with eight spring-wheat
(Triticum aestivum L.) cultivars bred in semiarid China. The NRS was judged to begin when there was a significant lowering of stomatal conductance
without any change in leaf relative water content (RWC), and the hydraulic root signal (HRS) was judged to begin when leaf
RWC changed significantly. Soil water contents (SWC), at which the NRS and HRS were switched on, differed among the eight
cultivars. For “Monkhead” and “Jinby,” representing “old” cultivars, the NRS and HRS were initiated successively at about 60% FWC (field water capacity) and 45%
FWC, respectively. Conversely, “Longchun8139-2” and “Plateau 602” (recent cultivars) showed the NRS and HRS occurring between 70% FWC and 35% FWC, a much wider range. The events of the other
four non-old cultivars were generally intermediate. This threshold range (TR) of soil FWCs between the onset of NRS and HRS
also narrowed over the successive developmental stages from seedling to seed filling. Fewer survival days (SD), lower maintenance
rate of grain yield (MRGY), and higher lethal leaf water potentials (LLWP) had been found in old cultivars. Widening TR was
significantly correlated with increasing SD and MRGY (r = 0.8713** and 0.7318*, respectively), and with decreased LLWP (r = 0.8591**). This survey of different-decade cultivars suggests that advances in grain yield and drought tolerance would
be made by targeted selection for a wider TR of root-sourced signals. 相似文献
14.
Liao Hong Rubio Gerardo Yan Xiaolong Cao Aiqin Brown Kathleen M. Lynch Jonathan P. 《Plant and Soil》2001,232(1-2):69-79
Root gravitropism may be an important element of plant response to phosphorus availability because it determines root foraging in fertile topsoil horizons, and thereby phosphorus acquisition. In this study we seek to test this hypothesis in both two dimensional paper growth pouch and three-dimensional solid media of sand and soil cultures. Five common bean (Phaseolus vulgaris L.) genotypes with contrasting adaptation to low phosphorus availability were evaluated in growth pouches over 6 days of growth, and in sand culture and soil culture over 4 weeks of growth. In all three media, phosphorus availability regulated the gravitropic response of basal roots in a genotype-dependent manner. In pouches, sand, and soil, the phosphorus-inefficient genotype DOR 364 had deeper roots with phosphorus stress, whereas the phosphorus-efficient genotype G19833 responded to phosphorus stress by producing shallower roots. Genotypes were most responsive to phosphorus stress in sand culture, where relative root allocation to the 0–3- and 3–6-cm horizons increased 50% with phosphorus stress, and varied 300% (3–6 cm) to 500% (0–3 cm) among genotypes. Our results indicate that (1) phosphorus availability regulates root gravitropic growth in both paper and solid media, (2) responses observed in young seedlings continue throughout vegetative growth, (3) the response of root gravitropism to phosphorus availability varies among genotypes, and (4) genotypic adaptation to low phosphorus availability is correlated with the ability to allocate roots to shallow soil horizons under phosphorus stress. 相似文献
15.
K. Brooksbank D. A. White E. J. Veneklaas J. L. Carter 《Trees - Structure and Function》2011,25(4):735-744
Salinity caused by land clearing is an important cause of land degradation in the Western Australian wheatbelt. Returning
a proportion of the cleared land to higher water use perennial vegetation is one option for reducing or slowing the salinisation
of land. Over the course of a year patterns of water use by Eucalyptus kochii subsp borealis (C. Gardner) D. Nicolle, a mallee eucalypt species, were monitored in three landscape positions with different water availability.
One treatment had groundwater at 2 m, a second at 4.5 m and a third had groundwater below a silcrete hardpan thought to be
impenetrable to roots. Hydraulic redistribution was observed in all landscape positions, and rates were positively correlated
with the magnitude of soil water potential gradients within the soil. High rates of hydraulic redistribution, facilitated
by abundant deep water may increase tree water use by wetting surface soils and reducing stomatal closure. This effect may
be countered by increased soil evaporation of water moved from root to soil following hydraulic redistribution; the net volumes
of redistributed water though lateral roots was calculated to be the equivalent of up to 27% of transpiration. 相似文献
16.
Over two consecutive years in the North Bank Plain Zone of Assam, India, during the spring growing season (February–June)
of- 2006 and 2007 we examined effects of morpho-physiological characteristics of rice (Oryza sativa L.) plants in relation to methane (CH4) emission from paddy fields. Traditional cultivar “Agni” and modern improved cultivar “Ranjit” were grown in light textured
loamy soil under irrigation. A higher seasonal integrated methane flux (E
sif) was recorded from “Agni” compared to “Ranjit”. Both cultivars exhibited an emission peak during active vegetative growth
and a second peak at panicle initiation. Leaf and tiller number, leaf area, length, and volume of root were greater in “Agni”,
but grain yield and yield-related parameters such as increased photosynthate partitioning to panicles at the expense of roots
were greater in “Ranjit”. “Ranjit” also photosynthesed faster than “Agni” during panicle development but slower than “Agni”
at tillering. In both the years, a higher soil organic carbon content was recorded in plots of “Agni”. Our results suggest
that in “Agni” enhanced diversion of photosynthate to roots resulted in more substrate being available to methanogenic bacteria
in the rhizosphere. Additionally, the more extensive vegetative growth of this cultivar may enhance methane transport from
the soil to the above-ground atmosphere. 相似文献
17.
Klaas G. J. Nierop Boris Jansen Jos A. Hageman Jacobus M. Verstraten 《Plant and Soil》2006,286(1-2):269-285
Extractable and solvent insoluble, ester-bound lipids were analysed in an acid, sandy soil profile under Corsican pine. The n-alkanes and alkanoic acids from the soil profile showed rather poor correlations with those from the pine needles and roots, while the n-alkanol composition in the mineral horizons strongly indicated the presence of lipids derived from a previous grass vegetation. Although the ester-bound lipids (ω-hydroxyalkanoic acids and α,ω-alkanedioic acids (>C24)) suggested that plant sources other than pines were present in the mineral soil horizons their composition was less contaminated and a clear distinction between needle and root input could be discerned. The divergent clustering of soil horizons and plant materials by individual and combined compound classes emphasized the usefulness of both extractable lipids and cutin/suberin in unravelling (past) vegetation and tissue history and contributions to soil organic matter. 相似文献
18.
宽窄行栽植模式下三倍体毛白杨根系分布特征及其与根系吸水的关系 总被引:4,自引:0,他引:4
采用剖面法对宽窄行栽植模式下三倍体毛白杨(triploid Populus tomentosa)的根系分布特征进行了研究;采用管式TDR系统对土壤剖面含水率变化动态进行了连续观测,并据此计算林木根系吸水速率,以探讨土壤含水率、根系分布和根系吸水分布之间的相关关系。研究结果表明:毛白杨的总平均根长密度在林带两侧和不同径向距离处非常接近(P>0.05);但在不同土层间变化很大(P<0.01),其中0-20和60-150 cm土层为根系主要分布区域,其根系所占比例共达86%;不同径阶间的根长密度差异显著(P<0.01),且其比例关系会随空间位置的改变而发生变化。不同栽植方位下,林带东侧毛白杨根系分布的浅层化程度高于西侧,且在径向240-280 cm内其0-0.5 mm的极细根显著多于西侧(P<0.05)。因此,宽窄行栽植模式下,深度和径阶是毛白杨根系分布的主要影响因子,而栽植方位会对其形态构型产生影响。毛白杨根系吸水模式受细根分布的影响,但会随土壤剖面水分有效性分布的变化而变化:当表土层水分有效性增加时,根系吸水主要集中在表土层;当表土层水分有效性降低时,深层土壤根系的吸水贡献率会逐渐增加;当土壤剖面水分条件异质性较高时,根系吸水主要集中在根系密度与水分有效性均较高的区域;当土壤剖面水分分布均匀且不存在水分胁迫时,根系吸水分布与细根分布最为一致。 相似文献
19.
Root Growth and Water Uptake by Maize Plants in Drying Soil 总被引:16,自引:0,他引:16
Sharp, R. E and Da vies, W. J. 1985. Root growth and water uptakeby maize plants in drying soil. J. exp. Bot. 36: 14411456. The influence of soil drying on maize (Zea mays L.) root distributionand use of soil water was examined using plants growing in thegreenhouse in soil columns. The roots of plants which were wateredwell throughout the 18 d experimental period penetrated thesoil profile to a depth of 60 cm while the greatest percentageof total root length was between 2040 cm. High soil waterdepletion rates corresponded with these high root densities.Withholding water greatly restricted root proliferation in theupper part of the profile, but resulted in deeper penetrationand higher soil water depletion rates at depth, compared withthe well watered columns. The deep roots of the unwatered plantsexhibited very high soil water depletion rates per unit rootlength. Key words: Maize, roots, water deficit, soil water depletion 相似文献
20.
The responses to precipitation of Haloxylon ammodendron (C.A. Mey.) Bunge (Chenopodiaceae), a small xerophilous tree growing on contrasting textured soils, were evaluated under
no, natural, and double precipitation treatments during the entire growing season of 2006. The contrasting textured soils
are sandy and heavy textured, and both are the original habitat of H. ammodendron at the south edge of Gubantonggute Desert, Central Asia. Photosynthesis, leaf water potential, transpiration, water use efficiency
and leaf biomass production were monitored throughout the growing season. Root distribution of H. ammodendron was evaluated at the end of the experiment. Overall, this small tree did not show significant response to a large summer
precipitation pulse or precipitation treatments, in terms of photosynthetic carbon assimilation on either soil. The leaf water
potential, transpiration, and water use efficiency appeared to be highly sensitive to a large precipitation pulse and precipitation
treatments in sandy soil; and leaf biomass production was also much higher for plants in sandy than that of heavy-textured
soil. In sandy soil, defoliation occurred when pre-dawn leaf water potential dropped below −3.0 MPa, while in heavy-textured
soil, defoliation occurred when pre-dawn leaf water potential dropped below −3.75 MPa. For similar above-ground parts, the
small trees at the sandy site developed much deeper root systems and had nearly double the surface area of feeder roots compared
to those at the heavy-textured site. Partially owning to the deeper and larger root system, H. ammodendron growing at coarse-textured site was in better water conditions than those at heavy-textured site under the same climatic
conditions. 相似文献