Bioremediation of gasoline contaminated soil by a bacterial consortium amended with poultry litter, coir pith and rhamnolipid biosurfactant.

The aim of the present study was to find methods for enhancing rates of hydrocarbon biodegradation in gasoline contaminated soil by ex situ bioremediation. Red soil (RS) was treated with gasoline-spilled soil (GS) from a gasoline station and different combinations of amendments were prepared using (i) mixed bacterial consortium (MC), (ii) poultry litter (PL), (iii) coir pith (CP) and (iv) rhamnolipid biosurfactant (BS) produced by Pseudomonas sp. DS10-129. The study was conducted for a period of 90 days during which bacterial growth, hydrocarbon degradation and growth parameters of Phaseolus aureus RoxB including seed germination, chlorophyll content, shoot and root length were measured. Approximately 67% and 78% of the hydrocarbons were effectively degraded within 60 days in soil samples amended with RS + GS + MC + PL + CP + BS at 0.1% and 1%. Maximum percentage of seed germination, shoot length, root length and chlorophyll content in P. aureus were recorded after 60 days in the above amendments. Further incubation to 90 days did not exhibit significant improvements. Statistical analysis using analysis of variance (ANOVA) and Duncan's multiple range test (DMRT) revealed that the level of amendments, incubation time and combination of amendments significantly influenced bacterial growth, hydrocarbon degradation, seed germination and chlorophyll content at a 1% probability level. All tested additives MC, PL, CP and rhamnolipid BS had significant positive effects on the bioremediation of GS.     

Mineral nutrition and growth of tropical maize as affected by soil acidity

Soil constraints linked to low pH reduce grain yield in about 10% of the maize growing area in tropical developing countries. The aim of this research was to elucidate the reasons for this maize yield reduction on an oxisol of Guadeloupe. The field experiment had two treatments: the native non-limed soil (NLI, pH 4.5, 2.1 cmol Al kg^–1, corresponding to 20% Al saturation), and the same soil limed 6 years prior to the experiment (LI, pH 5.3, 0 cmol Al kg^–1). The soils were fertilized with P and N. The above-ground biomass, root biomass at flowering, grain yield and yield components, leaf area index (LAI), light interception, radiation-use-efficiency (RUE), P and N uptake, soil water storage, and soil mineral N were measured during the maize cycle. The allometric relationships between shoot N concentration, LAI and above-ground biomass in LI were similar to those reported for maize cropped in temperate regions, indicating that these relationships are also useful to describe maize growth on tropical soils without Al toxicity. In NLI, soil acidity severely affected leaf appearance, leaf size and consequently the LAI, which was reduced by 60% at flowering, although the RUE was not affected. Therefore, the reduction in the above-ground biomass (30% at flowering) and grain yield (47%) were due to the lower LAI and light interception. At flowering, the root/shoot ratio was 0.25 in NLI and 0.17 in LI, and the root biomass in NLI was reduced by 64% compared to LI. Nitrogen uptake was also reduced in NLI in spite of high soil N availability. Nevertheless, shoot N concentration vs aboveground biomass showed a typical decline in both treatments. In NLI, the shoot P concentration vs above-ground biomass relationship showed an increase in the early stages, indicating that P uptake and root-shoot competition for the absorbed P in the early plant stages controlled the establishment and the development of the leaf area.     

The position of localized soil compaction determines root and subsequent shoot growth responses

Plants growing in soils typically experience a mixture of loose and compact soil. The hypothesis that the proportion of a root system exposed to compact soil and/or the timing at which this exposure occurs determines shoot growth responses was tested. Broccoli (Brassica oleracea var. italica cv. Greenbelt) seedlings were grown in pot experiments with compact, loose and localized soil compaction created by either horizontal (compact subsoils 75 or 150 mm below loose topsoil) or vertical (adjacent compact and loose columns of soil) configurations of loose (1.2 Mg m(-3)) and compact (1.8 Mg m(-3)) soil. Entirely compact soil reduced leaf area by up to 54%, relative to loose soil. When compaction was localized, only the vertical columns of compact and loose soil reduced leaf area (by 30%). Neither the proportion of roots in compact soil nor the timing of exposure could explain the differing shoot growth responses to localized soil compaction. Instead, the strong relationship between total root length and leaf area (r(2)=0.92) indicated that localized soil compaction reduced shoot growth only when it suppressed total root length. This occurred when isolated root axes of the same plant were exposed to vertical columns of compact and loose soil. When a single root axis grew through loose soil into either a shallow or deep compact subsoil, compensatory root growth in the loose soil maintained total root length and thus shoot growth was unaffected. These contrasting root systems responses to localized soil compaction may explain the variable shoot growth responses observed under heterogeneous conditions.     

Selecting plants and nitrogen rates to vegetate crude-oil-contaminated soil

Phytoremediation can be effective for remediating contaminated soils in situ and generally requires the addition of nitrogen (N) to increase plant growth. Our research objectives were to evaluate seedling emergence and survival of plant species and to determine the effects of N additions on plant growth in crude-oil-contaminated soil. From a preliminary survival study, three warm-season grasses--pearlmillet (Pennisetum glaucum [L.] R. Br.), sudangrass (Sorghum sudanense [Piper] Stapf [Piper]), and browntop millet (Brachiaria ramosa L.)--and one warm-season legume--jointvetch (Aeschynomene americana L.)--were chosen to determine the influence of the N application rate on plant growth in soil contaminated with weathered crude oil. Nitrogen was added based on total petroleum hydrocarbon-C:added N ratios (TPH-C:TN) ranging from 44:1 to 11:1. Plant species were grown for 7 wk. Root and shoot biomass were determined and root length and surface area were analyzed. Pearlmillet and sudangrass had higher shoot and root biomass when grown at a TPH-C:TN (inorganic) ratio of 11:1 and pearlmillet had higher root length and surface area when grown at 11:1 compared with the other species. By selecting appropriate plant species and determining optimum N application rates, increased plant root growth and an extended rhizosphere influence should lead to enhanced phytoremediation of crude-oil-contaminated soil.     

Response of Populus tremula to heterogeneous B distributions in soil

Background

Poplars accumulate inordinate amounts of B in their leaves and are candidate plants for the remediation of B contaminated soil. We aimed to determine the effect of heterogeneous B distribution in soil by comparing the growth and B accumulation of young Populus tremula trees growing in soil with heterogeneous and homogeneous B distributions.

Methods

The first of two experiments focused on the tolerance and B accumulation of P. tremula under heterogeneous soil B distributions, while the second was designed to study fine root growth under such conditions in detail.

Results

Growth and B accumulation of P. tremula were unaffected by the spatial distribution of B. Root and shoot growth were both reduced simultaneously when leaf B concentrations increased above 800 mg kg^?1. In the heterogeneous soil B treatments, root growth was more reduced in spiked soil portions with B concentrations >20 mg kg^?1. Fine root length growth was stronger inhibited by B stress than secondary growth.

Conclusions

The root growth responses of P. tremula to B are primarily a systemic effect induced by shoot B toxicity and local toxicity effects on roots become dominant only at rather high soil B concentrations. Local heterogeneity in soil B should have little influence on the phytoremediation of contaminated sites.     

Importance of soil-water relations in assessing the endpoint of bioremediated soils

This study was conducted to investigate water movement in hydrocarbon contaminated soils. Three soils were studied, a hydrocarbon contaminated soil, the same soil after 3 years of bioremediation, and a control soil from the same site. There was a critical soil water content around 18% (bioremediated soil) and 20% (contaminated soil), above which the sorptivity of the contaminated soil was near that of the control soil. For soils with water contents below this value, there was a strong divergence in sorptivity between contaminated and control or bioremediated soils. Results suggest that water availability in contaminated soils will be highly dependent on soil water properties as water potential approaches the permanent wilting point (-1.5 MPa matrix potential).Infiltration of water into air dry (2% m.c. w/w) hydrocarbon contaminated soils was up to three orders of magnitude slower than for the control soil. For air dried soils, the infiltration rate of the contaminated and bioremediated soils was constant with time. This was in contrast to the control soil where infiltration rate was a function of the reciprocal of the square root of time.     

Above-ground competition does not alter biomass allocated to roots in Abutilon theophrasti

We tested whether plants allocate proportionately less biomass to roots in response to above-ground competition as predicted by optimal partitioning theory. Two population densities of Abutilon theophrasti were achieved by planting one individual per pot and varying spacing among pots so that plants in the two densities experienced the same soil volume but different degrees of canopy overlap. Density did not affect root:shoot ratio, the partitioning of biomass between fine roots and storage roots, fine root length, or root specific length. Plants growing in high density exhibited typical above-ground responses to neighbours, having higher ratios of stem to leaf biomass and greater leaf specific area than those growing in low density. Total root biomass and shoot biomass were highly correlated. However, storage root biomass was more strongly correlated with shoot biomass than was fine-root biomass. Fine-root length was correlated with above-ground biomass only for the small subcanopy plants in crowded populations. Because leaf surface area increased with biomass, the ratio between absorptive root surface area and transpirational leaf surface area declined with plant size, a relationship that could make larger plants more susceptible to drought. We conclude that A. theophrasti does not reallocate biomass from roots to shoots in response to above-ground competition even though much root biomass is apparently involved in storage and not in resource acquisition.     

Phytoremediation of dye contaminated soil by Leucaena leucocephala (subabul) seed and growth assessment of Vigna radiata in the remediated soil

The present study was investigated for soil bioremediation through sababul plant biomass (Leucaena leucocephala). The soil contaminated with textile effluent was collected from Erode (chithode) area. Various physico-chemical characterizations like N, P, and K and electrical conductivity were assessed on both control and dye contaminated soils before and after remediation. Sababul (L. leucocephala) powder used as plant biomass for remediation was a tool for textile dye removal using basic synthetic dyes by column packing and eluting. The concentration of the dye eluted was compared with its original concentration of dye and were analyzed by using UV–vis spectrophotometer. Sababul plant biomass was analyzed for its physico-chemical properties and active compounds were detected by GC–MS, HPTLC and FTIR. Plant growth was assessed with green gram on the textile contaminated soil and sababul had the potential of adsorbing the dye as the contaminated soil and also check the growth of green gram.     

不同氮磷添加浓度对豆科3种树木幼苗生长及生物量分配的影响

选取海南尖峰岭热带山地雨林中不同功能类群的豆科树木幼苗（代表低氮需求的长脐红豆Ormosia balansae Drake、中氮需求的荔枝叶红豆Ormosia semicastrata Hance f. litchifolia How和高氮需求的猴耳环Archidendron clypearia（Jack）I.C.Nielsen）为对象,设置5个浓度梯度的氮（N）添加和2个浓度梯度的磷（P）添加养分控制实验,研究苗木的生长表现。结果显示：（1）氮添加条件下,3个树种幼苗的苗高、总叶面积、根长、根表面积、生物量5个指标对中高浓度氮添加的敏感性大小均为长脐红豆 > 猴耳环 > 荔枝叶红豆;其中,叶总面积对氮肥浓度变化的响应最敏感,长脐红豆的根长、根表面积以及猴耳环根长的响应敏感性次之。（2）长脐红豆和猴耳环幼苗的根冠比受氮肥添加浓度的影响不显著;荔枝叶红豆幼苗的根冠比则随氮肥添加浓度的升高而增大,这种适应策略反映出荔枝叶红豆幼苗对添加中高浓度氮肥有较强的耐受能力。（3）磷添加条件下,长脐红豆和猴耳环幼苗的生长速率为低磷>高磷,表明这2个树种在幼苗阶段为低氮、低磷需求;荔枝叶红豆在低氮处理下的生长速率为高磷>低磷,表明该树种幼苗阶段为低氮、高磷需求。     

Habitat-specific responses of seed germination and seedling establishment to soil water condition in two Rheum species in the high Sino-Himalayas

Knowledge of how germination and seedling establishment respond to soil water condition is crucial for plant conservation under global warming and land-use changes. We tested the flooding and drought tolerance of two plant species with different occurrences along a soil water gradient by assessing seed germination, seedling survival, seedling growth, and root characteristics. In the high Sino-Himalayas, Rheum alexandrae typically occurs in wetlands, R. nobile in scree or open slope with well-drained soils. Seeds and seedlings of the two species were subjected to different soil water conditions in controlled greenhouse experiments. Seed germination in both species was inhibited by high soil water content; however, seeds of R. alexandrae were more tolerant to flooding, especially to submergence. Seedling survival, biomass accumulation, root diameter, and root porosity of R. alexandrae increased significantly with increased soil water content, but submergence was lethal for seedlings. Seedling survival, biomass accumulation, and root length of R. nobile increased significantly in response to reduced soil water content. These results indicate that in the two species, seed germination and seedling establishment in response to different soil water condition are habitat-specific. Because both species are susceptible to moderate changes in soil water condition, their species-specific requirements with respect to this factor should be a consideration when planning their conservation.     

Phenotypic plasticity of <Emphasis Type="Italic">Chenopodium murale</Emphasis> across contrasting habitat conditions in peri-urban areas in Indian dry tropics: Is it indicative of its invasiveness?

Phenotypic plasticity is an important plant trait associated with invasiveness of alien plants that reflects its ability to occupy a wide range of environments. We investigated the phenotypic response of Chenopodium murale to resource variability and ontogeny. Its plant-level and leaf-level traits were studied at high-resource (HR) and low-resource (LR) sites in peri-urban areas in Indian dry tropics. Plants at LR had significantly higher root length, root/shoot biomass ratio, stem mass and root mass fractions. Plants at HR had higher shoot length, basal diameter, leaf mass fraction and leaf area ratio. Leaf-level traits like leaf area and chlorophyll a were also higher here. Mean plasticity indices for plant- and leaf-level traits were higher at HR. With increasing total plant biomass, there was significant increase in the biomass of leaf, stem, root, and reproductive parts, and root and shoot lengths, whereas root/shoot length ratio, their biomass ratio, and leaf and root mass fractions declined significantly. Allocation to roots and leaves significantly decreased with increasing plant size at both sites. But, at any size, allocation to roots was greater at LR, indicative of optimization of capture of soil nutrients, whereas leaf allocation was higher at HR. Consistently increasing stem allocation equaled leaf allocation at comparatively higher shoot lengths at HR. Reproductive biomass comprised 10–12% of the plant’s total biomass. In conclusion, the success of alien weed C. murale across environmentally diverse habitat conditions in Indian dry tropics can be attributed to its high phenotypic plasticity, resource utilization capability in low-resource habitats and higher reproductive potential. These characteristics suggest that it will continue to be an aggressive invader.     

Effects of soil temperature on root and shoot growth traits and iron deficiency chlorosis in sorghum genotypes grown on a low iron calcareous soil

Iron deficiency chlorosis (FeDC) is a common disorder for sorghum [Sorghum bicolor (L.) Moench] grown on alkaline calcareous soils. Four sorghum genotypes were grown in growth chambers on a low Fe (1.3 g/g DTPA-extractable), alkaline (pH 8.0), calcareous (3.87% CaCO₃ equivalent) Aridic Haplustoll to determine effects of different soil temperatures (12, 17, 22 and 27°C at a constant 27°C air temperature) on various root and shoot growth traits and development of FeDC. As soil temperature increased, leaf chlorosis became more severe, and shoot and root dry weights, root lengths, and leaf areas increased markedly. Shoot/root ratios, shoot weight/root length, leaf area/shoot weight and leaf area/root weight and root length also increased while root length/root weight decreased as soil temperature increased. Severe FeDC developed in all genotypes even though genotypes had previously shown different degrees of resistance to FeDC. Genotypes differed in most growth traits, especially dry matter yields, root lengths, and leaf areas, but most traits did not appear to be related to genotype resistance to FeDC. The most FeDC resistant genotype had the slowest growth rate and this may be a mechanism for its greater resistance to FeDC.     

Influence of organic and inorganic soil amendments on plant growth in crude oil-contaminated soil

Phytoremediation can be a viable alternative to traditional, more costly remediation techniques. Three greenhouse studies were conducted to evaluate plant growth with different soil amendments in crude oil-contaminated soil. Growth of alfalfa (Medicago sativa L., cultivar: Riley), bermudagrass (Cynodon dactylon L., cultivar: Common), crabgrass (Digitaria sanguinalis, cultivar: Large), fescue (Lolium arundinaceum Schreb., cultivar: Kentucky 31), and ryegrass (Lolium multiflorum Lam., cultivar: Marshall) was determined in crude oil-contaminated soil amended with either inorganic fertilizer, hardwood sawdust, papermill sludge, broiler litter or unamended (control). In the first study, the addition of broiler litter reduced seed germination for ryegrass, fescue, and alfalfa. In the second study, bermudagrass grown in broiler litter-amended soil produced the most shoot biomass, bermudagrass produced the most root biomass, and crabgrass and bermudagrass produced the most root length. In the third study, soil amended with broiler litter resulted in the greatest reduction in gravimetric total petroleum hydrocarbon (TPH) levels across the six plant treatments following the 14-wk study. Ryegrass produced more root biomass than any other species when grown in inorganic fertilizer- or hardwood sawdust + inorganic fertilizer-amended soil. The studies demonstrated that soil amendments and plant species selection were important considerations for phytoremediation of crude oil-contaminated soil.     

Influence of Pericarp,Cotyledon and Inhibitory Substances on Sharp Tooth Oak (Quercus aliena var. acuteserrata) Germination

In order to explore the mechanism of delayed and uneven germination in sharp tooth oak (Quercus aliena var. acuteserrata) (STO), mechanical scarification techniques were used to study STO root and shoot germination and growth. The techniques used were: removing cup scar (RS), removing the pericarp (RP), and cutting off 1/2 (HC) and 2/3 (TC) cotyledons. Germination percentage and root and shoot length for Chinese cabbage (Beassica pekinensis) seeds (CCS) were also investigated for CCS cultivated in a Sanyo growth cabinet watered by distilled water and 80% methanol extracts from the acorn embryo, cotyledon and pericarp with concentrations of 1.0 g, 0.8 g, 0.6 g and 0.4 g dry acorn weight per ml methanol. The results showed that the majority of roots and shoots from acorns with RP and HC treatment emerged two weeks earlier, more simultaneously, and their total emergences were more than 46% and 28% higher, respectively. TC accelerated root and shoot emergence time and root length, but root and shoot germination rate and shoot height had no significant difference from the control. Positive consequences were not observed on all indices of RS treatment. The germination rates of CCS watered by 1.0 g·ml⁻¹ methanol extracts from the embryo and cotyledon were significantly lower than those from the pericarp, and all concentrations resulted in decreased growth of root and shoot. Methanol extracts from pericarp significantly reduced root length of CCS, but presented little response in germination percentage and shoot length. The inhibitory effect was gradually increased with the increasing concentration of the methanol extract. We conclude that both the mechanical restriction of the pericarp and the presence of germination inhibitors in the embryo, cotyledon and pericarp are the causes for delayed and asynchronous germination of STO acorns.     

Influence of biochar and compost on phytoremediation of oil-contaminated soil

The use of pyrolyzed carbon, biochar, as a soil amendment is of potential interest for improving phytoremediation of soil that has been contaminated by petroleum hydrocarbons. To examine this question, the research reported here compared the effects of biochar, plants (mesquite tree seedlings), compost and combinations of these treatments on the rate of biodegradation of oil in a contaminated soil and the population size of oil-degrading bacteria. The presence of mesquite plants significantly enhanced oil degradation in all treatments except when biochar was used as the sole amendment without compost. The greatest extent of oil degradation was achieved in soil planted with mesquite and amended with compost (44% of the light hydrocarbon fraction). Most probable number assays showed that biochar generally reduced the population size of the oil-degrading community. The results of this study suggest that biochar addition to petroleum-contaminated soils does not improve the rate of bioremediation. In contrast, the use of plants and compost additions to soil are confirmed as important bioremediation technologies.     

Allocation,within and between organs,and the dynamics of root length changes in two birch species

Spatial and temporal dynamics of biomass allocation within and between organs were investigated in seedlings of two birch species of contrasting successional status. Seedlings of Betula alleghaniensis Britt (yellow birch) and B. populifolia Marsh (gray birch) were grown for 6 weeks at two nutrient levels in rectangular plexiglass containers to allow non-destructive estimates of root growth, production and loss. Leaf area and production were simultaneously monitored. Yellow birch responded more to nutrient level than gray birch in terms of total biomass, shoot biomass, leaf area and root length. Yellow birch also flexibly altered within-organ allocation (specific leaf area, specific root length and specific soil amount). In contrast, gray birch altered between-organ allocation patterns (root length:leaf area and soil amount:leaf area ratios) more than yellow birch in response to nutrient level. Yellow birch showed greater overall root density changes within a very compact root system, while gray birch showed localized root density changes as concentric bands of new root production spread through the soil. Species differ critically in their responses of standing root length and root production and loss rates to nutrient supply. Early successional species such as gray birch are hypothesized to exhibit higher plasticity in varied environments than later successional species such as yellow birch. Our results suggest that different patterns of allocation, within and between plant organs, do not necessarily follow the same trajectories. To characterize thoroughly the nature of functional flexibility through ontogeny, within- and between-organ patterns of allocation must be accounted for.     

Bioremediation of Pb-contaminated soil based on microbially induced calcite precipitation

To remediate lead (Pb)-contaminated soils, it is proposed that microbially induced calcite precipitation (MICP) would provide the best alternative to other remediation technologies. In this study, Pb bioremediation in soils was investigated using the calcite-precipitating bacterium Kocuria flava. Results indicate that the Pb is primarily associated with the carbonate fraction in bioremediated soil samples. The bioavailability of Pb in contaminated soil was reduced so that the potential stress of Pb was alleviated. This research provides insight into the geochemistry occurring in the MICP-based Pb-remediated soils, which will help in remediation decisions.     

Growth promotion effect of Fusarium spp. PPF1 from bermudagrass (Cynodon dactylon) rhizosphere on Indian spinach (Basella alba) seedlings are linked to root colonisation

A rhizosphere fungus was isolated from roots of bermudagrass (Cynodon dactylon) and identified as Fusarium spp. PPF1. A pot experiment was conducted to test its ability to promote the vegetative growth of Indian spinach seedlings (Basella alba). Indian spinach seeds were sown in sterilised field soil amended with wheat grain inoculum of PPF1 at the rate of 0.5 and 1.0% w/w, and plants were grown for 21?days in a net house. Significantly, higher germination percentage and vigour index were observed due to application of PPF1 in the potting soil. Treatment with PPF1 also significantly increased shoot length, shoot fresh weight, shoot dry weight, root length, root fresh weight, root dry weight, leaf area and leaf chlorophyll content of cucumber plants compared to non-treated control. The growth promotion rate increased with the increasing concentration of inoculum of PPF1 applied to the soil. The fungus was re-isolated from the roots of cucumber plants at higher frequencies, while a positive co-relation was found between the root colonisation ability and the plant growth enhancement by the isolate. These results suggest that growth promotion effect of Fusarium spp. PPF1 on Indian spinach (B. alba) are linked to root colonisation ability of the fungus.     

干旱胁迫下柳枝稷在露天矿区土壤中的种子萌发和生长特性

将能源植物用作矿区生态修复物种,对矿区的经济发展和生态环境具有重要意义。以能源植物柳枝稷为研究对象,通过盆栽试验,分析其在对照、轻度、中度以及重度干旱胁迫下柳枝稷幼苗在矿区土壤基质和非矿区土壤基质下的生长特性,并结合不同干旱胁迫下矿区土壤基质中种子萌发特征,揭示柳枝稷对干旱胁迫的响应机制和对矿区土壤的生态适应性。试验结果表明：（1）柳枝稷种子发芽总数、发芽率、发芽势以及发芽指数在轻度胁迫下达到最大值,活力指数在对照组最高,而在重度胁迫下,各项指标均达到最小值;种苗各生长指标在轻度胁迫下最小,幼苗根长和鲜重在重度胁迫下最高,芽长和芽重在其余三组胁迫下相差不大。（2）干旱胁迫使两种土壤基质下的柳枝稷株高降低,枯叶率增加,在对照、轻度胁迫和重度胁迫下能够保持叶片水分含量和分蘖数稳定;矿区土壤基质中,柳枝稷根体积在轻度胁迫下最大,中度胁迫下根长最长,重度胁迫下根数最多;根冠比随着干旱胁迫的加剧表现出先减后增的趋势,在轻度胁迫下最小,在重度胁迫下最大。（3）与非矿区土壤基质相比,柳枝稷在矿区土壤基质下根冠比更大,其余生长指标均更小;随着干旱胁迫的加剧,柳枝稷在矿区土壤基质下的株高、枯叶率、叶片相对含水量以及分蘖数与非矿区土壤基质下变化趋势一致。综上,柳枝稷在矿区土壤下的生长特性比在非矿区土壤下表现更差;在轻度干旱胁迫下各项生理指标表现更好,在中度和重度干旱胁迫下虽然其生长发育受到限制,但能通过调整生物量配比确保自身存活。因此,柳枝稷在矿区土壤环境下具有一定的抗旱性和抗贫瘠性,将其作为矿区生态修复品种具有可行性。     

When the going gets tough: Responses of Sorghum bicolor L. (cv. Tegemeo) seedlings to soil penetration resistance

Summary

Sorghum bicolor L. (cv. Tegemeo) seedlings were grown for nine days in soil at field capacity packed to give a uniform penetration resistance (PR) of either 0.25, 1.00 or 1.75 MPa. Root biomass was not significantly affected by soil PR treatment. However, as PR increased to 1.75 MPa, the diameter of the seminal root axis increased by 52% whilst its length decreased by 30%. Shoot growth, in terms of oven dry (OD) weight and photo-synthetic area, was reduced in both the 0.25 MPa and 1.75 MPa treatments compared to the 1.00 MPa treatment. A reduced nutrient, water or oxygen supply to the roots were discounted as possible causes of the root and shoot responses to soil PR. It is suggested that the changes in root morphology between treatments were a direct result of the changes in soil PR. For shoot growth, in the 0.25 MPa treatment it is suggested that shoot growth was reduced as a result of an increase in the carbon sink strength of the roots.