Sand Culture System Research Articles

Exogenous myristate promotes the colonization of arbuscular mycorrhizal fungi in tomato.

Arbuscular mycorrhizal fungi (AMF) can establish symbiotic associations with the roots of most terrestrial plants, thereby improving the tolerance of the host plants to biotic and abiotic stresses. Although AMF cannot synthesize lipids de novo, they can obtain lipids from the root cells for their growth and development. A recent study reveals that AMF can directly take up myristate (C14:0 lipid) from the environment and produce a large amount of hyphae in asymbiotic status; however, the effect of environmental lipids on AM symbiosis is still unclear. In this study, we inoculated tomato (Solanum lycopersicum) with AMF in an in vitro dual culture system and a sand culture system, and then applied exogenous myristate to the substrate, in order to explore the effect of exogenous lipids on the mycorrhizal colonization of AMF. We investigated the hyphae growth, development, and colonization of AMF, and examined the gene expression involved in phosphate transport, lipid biosynthesis, and transport. Results indicate that exogenous lipids significantly stimulated the growth and branching of hyphae, and significantly increased the number of hyphopodia and mycorrhizal colonization of AMF, with arbuscular abundance and intraradical spores or vesicles being the most promoted. In contrast, exogenous myristate decreased the growth range and host tropism of the germ tubes, and largely inhibited the exchange of nutrition between symbionts. As a result, exogenous myristate did not affect the plant growth. This study suggests that lipids promote mycorrhizal colonization by enhancing the growth and development of AMF hyphae and increasing their contact opportunities with plant roots. To the best of our knowledge, this is the first report that shows that lipids promote the colonization of AMF. Our study highlights the importance of better understanding the roles of environmental lipids in the establishment and maintenance of AM symbiosis and, thus, in agricultural production.

Compacted soil adaptability of Brassica napus driven by root mechanical traits

Soil compaction due to mechanized farming operations is a recurrent issue affecting crop growth and yield. Yet, how soil compaction affects plant functions and ecological strategies is poorly known. With Brassica napus, i.e. a widespread crop species as study object, we aim to understand (i) how soil compaction impacts root and shoot traits related to the plant’s well-being, nutrient acquisition of Brassica napus with different mechanical robustness, as well as their trade-offs, and (ii) how such impacts vary among different cultivars. To do this, we cultivated six cultivars of Brassica napus in non-compacted (control) and compacted (treatment) soils, respectively, in a sand culture system. After harvesting, a series of mechanical, morphological and chemical traits of roots and/or shoots were measured. Results showed that soil compaction significantly limited root penetration depth and root system establishment in morphological traits, leading further to significant reduction in nutrients acquisition and plant biomass accumulation. However, soil compaction significantly increases the average root diameter and root/shoot ratio, and facilitate more root exudates secretion (e.g. organic acids and polysaccharides) of Brassica napus cultivars. The Brassica napus cultivars with large root mechanical traits (e.g. root tensile force, root tensile strength and modulus of elasticity) had higher root cellulose and lignin concentrations and showed a stronger response in maximum root depth and specific root length compared with Brassica napus cultivars with small root mechanical traits in compacted treatment, which resulted in the greater fine root length and more root exudates secretion at root-soil interface. Furthermore, deep rooting enhanced nutrients acquisition and further biomass accumulation in compacted soil. Totally, the Brassica napus cultivars with large root mechanical traits with more fine roots and root exudates were critical for Brassica napus root penetration into a deep soil layer in compacted soil.

Molybdenum-induced effects on nitrogen absorption and utilization under different nitrogen sources in Vitis vinifera

ABSTRACT Nitrogen (N) in different forms has been demonstrated to play significant roles in plants. However, little is known about molybdenum (Mo) effects on N absorption and utilization in grapevine seedlings grown under different N sources. The present study used a sand culture system to analyze the impact of Mo application (0 μM; 1 μM) on N absorption and utilization in grapevine (Vitislabrusca × V. vinifera ‘Shine Muscat’ (rootstock 3309 m)) young potted seedlings under different N sources (NO3 −, NH4NO3 and NH4 +). The different N forms and Mo application significantly influenced dry matter accumulation, and root architecture and activity. The effects of Mo on total N content followed the order of (NH4NO3 > NO3 − > NH4 +). Moreover, Mo and N induced VvMOT1 and VvNRT1.1 expression synergistically. Mo supply altered the utilization of NO3 −, NO2 −, and NH4 + in grapevines under different N sources. NH4NO3 showed the highest effect while NH4 + the least. Furthermore, the 15N-labeling experiment showed that the 15N content in shoot and root and the 15N-use efficiency were the highest after Mo application under NH4NO3 source, indicating the synergistic effects of Mo with the co-application of NO3 − and NH4 + sources. The study’s findings provide insights on Mo and N fertilizer utilization for cultivation and production practices in fruits.

Wheat growth responses to soil mechanical impedance are dependent on phosphorus supply

Increased mechanical impedance induced by soil drying or compaction causes reduction in plant growth and crop yield. However, how mechanical impedance interacts with nutrient stress has been largely unknown. Here, we investigated the effect of mechanical impedance on the growth of wheat seedlings under contrasting phosphorus (P) supply in a sand culture system which allows the mechanical impedance to be independent of water and nutrient availability. Two wheat genotypes containing the Rht-B1a (tall) or Rht-B1c (gibberellin-insensitive dwarf) alleles in the Cadenza background were used and their shoot and root traits were determined. Mechanical impedance caused a significant reduction in plant growth under sufficient P supply, including reduced shoot and root biomass, leaf area and total root length. By contrast, under low P supply, mechanical impedance did not affect biomass, tiller number, leaf length, and nodal root number in both wheat genotypes, indicating that the magnitude of the growth restriction imposed by mechanical impedance was dependent on P supply. The interaction effect between mechanical impedance and P level was significant on most plant traits except for axial and lateral root length, suggesting an evident physical and nutritional interaction. Our findings provide valuable insights into the integrated effects of plants in response to both soil physical and nutritional stresses. Understanding the response patterns is critical for optimizing soil tillage and nutrient management in the field.

Effects of pH and Mineral Nutrition on Growth and Physiological Responses of Trembling Aspen (Populus tremuloides), Jack Pine (Pinus banksiana), and White Spruce (Picea glauca) Seedlings in Sand Culture.

Responses of trembling aspen (Populus tremuloides), jack pine (Pinus banksiana), and white spruce (Picea glauca) seedlings to root zone pH ranging from 5 to 9 were studied in sand culture in the presence of two mineral nutrition levels. After eight weeks of treatments, effects of pH on plant dry weights varied between the plant species and were relatively minor in white spruce. Higher nutrient supply significantly increased dry weights only in trembling aspen subjected to pH 5 treatment. There was little effect of pH and nutrition level on net photosynthesis and transpiration rates in white spruce and jack pine, but net photosynthesis markedly declined in aspen at high pH. Chlorophyll concentrations in young foliage decreased the most in trembling aspen and jack pine. The effects of high pH treatments on the concentrations of Mg, P, Ca, Mn, Zn, and Fe in young foliage varied between the plant species with no significant decreases of Fe and Zn recorded in trembling aspen and white spruce, respectively. This was in contrast to earlier reports from the studies carried out in hydroponic culture. The sand culture system that we developed could be a more suitable alternative to hydroponics to study plant responses to pH in the root zone. Plant responses to high pH appear to involve complex events with a likely contribution of nutritional effects and altered water transport processes.

Laccaria bicolor Mobilizes both Labile Aluminum and Inorganic Phosphate in Rhizosphere Soil of Pinus massoniana Seedlings Field Grown in a Yellow Acidic Soil.

Plant growth is often limited by highly activated aluminum (Al) and low available phosphorus (P) in acidic soil. Ectomycorrhizal (ECM) fungi can improve their host plants' Al tolerance by increasing P availability while decreasing Al activity in vitro or in hydroponic or sand culture systems. However, the effect of ECM fungi on inorganic P (IP) and labile Al in acidic soil in the field, particularly in conjunction with Al treatment, remains poorly understood. The present study aimed to determine the influence of ECM fungal association on the mobilization of IP and labile Al in rhizosphere soil of host plants grown in the field with external Al treatment and the underlying nutritional mechanism in plant Al tolerance. To do so, 4-week-old Pinus massoniana seedlings were inoculated with three ECM isolates (Laccaria bicolor 270, L. bicolor S238A, and L. bicolor S238N) and grown in a Haplic Alisol field with or without Al treatment for 12 weeks. Results showed that L. bicolor association enhanced the available P depletion and facilitated the mobilization of IP and labile Al, in turn improving the capacity of host plant to use Al-bound P, Ca-bound P, and occluded P, particularly when P. massoniana seedlings were inoculated with L. bicolor S238A. Inoculation with L. bicolor isolates also enhanced the solubility of labile Al and facilitated the conversion of acid-soluble Al into exchangeable Al. Our findings suggested that ECM inoculation could enhance plant Al tolerance in the field by mobilizing IP to improve the P bioavailability but not by decreasing Al activity.IMPORTANCE Here, we reveal the underlying nutritional mechanism in plant Al tolerance conferred by ectomycorrhizal (ECM)-fungus inoculation in the field and report the screening of a promising ECM isolate to assist phytoremediation and afforestation using Pinus massoniana in acidic soil in southern China. This study advances our understanding of the contribution of ECM fungi to plant-ECM-fungus symbiosis and highlights the vital role of ECM-fungus inoculation in plant Al tolerance. In addition, the results described in the present study confirm the importance of carrying out studies in the field rather than only in vitro studies. Our findings strengthen our understanding of the role of ECM-fungus association in detecting, utilizing, and transporting unavailable nutrients in the soil to enhance host plant growth and adaptability in response to adverse habitats.

Buffered delivery of phosphate to Arabidopsis alters responses to low phosphate.

Arabidopsis has been reported to respond to phosphate (Pi) stress by arresting primary root growth and increasing lateral root branching. We developed a system to buffer Pi availability to Arabidopsis in gel media systems by charging activated aluminum oxide particles with low and sufficient concentrations of Pi, based on previous work in horticultural and sand culture systems. This system more closely mimics soil chemistry and results in different growth and transcriptional responses to Pi stress compared with plants grown in standard gel media. Low Pi availability in buffered medium results in reduced root branching and preferential investment of resources in axial root growth. Root hair length and density, known responses to Pi stress, increase in low-buffered Pi medium. Plants grown under buffered Pi conditions have different gene expression profiles of canonical Pi stress response genes as compared with their unbuffered counterparts. The system also eliminates known complications with iron (Fe) nutrition. The growth responses of Arabidopsis supplied with buffered Pi indicate that the widely accepted low-Pi phenotype is an artifact of the standard gel-based growth system. Buffering Pi availability through the method presented here will improve the utility and accuracy of gel studies by more closely approximating soil conditions.

Salinity tolerance among a large range of bermudagrasses (Cynodon spp.) relative to other halophytic and non-halophytic perennial C4 grasses

The increasing demand on potable water has resulted in a greater reliance on poorer quality water, including saline sources, for maintaining forage and turfgrasses in agricultural and urban landscapes. Consequently, it will be crucial to identify grasses that can tolerate saline irrigation water. This study aimed to determine salinity tolerance among a large range of bermudagrasses relative to other perennial C4 grasses and test the relationship between salt tolerance and drought resistance. We report the salinity tolerance of 70 genotypes of mostly Australian bermudagrass ecotypes that were compared to halophytic cultivars of seashore paspalum (Paspalum vaginatum Swartz) and a non-halophytic cultivar of Queensland blue couch (Digitaria didactyla Willd) using a flood and drain sand culture system with salt treatments 1–40dSm−1. For the first time for C4 grasses, salt tolerance was determined by comparing total biomass of the grasses with and without salt treatment. Large genetic variation in salinity tolerance was identified and six bermudagrasses collected from saline habitats had salinity tolerance equal to that of seashore paspalum under the salinity treatments used in this study. There was no correlation between salt tolerance and drought resistance phenotypes determined from our previous research. Canopy temperature differential during salt stress was negatively correlated (r=−0.71 to −0.91, P<0.001) to salt tolerance and has potential to be used for screening bermudagrasses for salt tolerance using flood and drain sand culture. Salinity levels above 20dSm−1 for 8 weeks appeared to be effective for detecting large variation for salt tolerance in bermudagrass.

Contribution of glomalin to Pb sequestration by arbuscular mycorrhizal fungus in a sand culture system with clover plant

Glomalin (a glycoprotein) is produced by arbuscular mycorrhizal fungi and has the ability to sequester toxic heavy metals. We hypothesized that an increase in the concentration of Pb would lead to increased glomalin production and consequently higher Pb-sequestration. In a two compartment pot culture experiment, clover plants (Trifolium repens L.) were inoculated with arbuscular mycorrhizal fungus, Rhizophagus irregularis, in sterile washed sand and then treated with Pb concentrations of 0, 150, 300 and 450 μM as Pb(NO3)2. The root compartment (RC) was isolated from the hyphal compartment (HC) by nylon mesh (37 μm). The glomalin was extracted from both RC and HC and assayed by using Bradford method and monoclonal antibody MAb32B11. The amount of sequestrated Pb was determined after wet digestion of glomalin. The results showed that the amount of Bradford reactive and immunoreactive glomalin is not correlated with hyphal biomass at different Pb levels. There was a positive and significant relationship between the percentage of root colonization and both immunoreactive and Bradford reactive glomalin. The content of Bradford and immunoreactive glomalin in both RC and HC was significantly increased by rising Pb levels, compared to the unleaded control. The maximum immunoreactive glomalin in HC (10.04 μg/mg hyphae) and in RC (7.79 μg/mg root) was recorded at 450 μM of Pb, which was markedly different from other levels of Pb. Total Pb sequestrated by HC glomalin enhanced as the level of Pb increased and it was 665.72 μg Pb/mg HC glomalin at 450 μM of Pb, while the total Pb sequestrated by RC glomalin was enhanced as the levels of Pb increased up to 300 μM (228.91 μg Pb/mg RC glomalin). Also, there were positive and significant correlations between both immunoreactive and Bradford reactive glomalin in HC with the amount of Pb sequestration. Consequently, this study provides evidence on the role of glomalin in Pb sequestration which should be considered for biostabilization of toxic elements in polluted sites.

The effect of impedance to root growth on plant architecture in wheat.

Background and aimsWe were interested in the effect of impedance to root growth on root and shoot architecture of wheat. It is known that Rht-1 semi-dwarfing alleles decrease the degree of leaf stunting due to root impedance. We compared commercial wheat cultivars containing different Rht-1 alleles to determine whether leaf stunting caused by root impedance differed between cultivars. We investigated effects of impedance to root growth on the angular spread of roots.MethodsThe wheat cultivars Avalon, Robigus and Battalion, carrying semi-dwarfing alleles of Rht-1, and cv. Cadenza, carrying the tall, wild-type allele, were grown under two levels of soil strength in a sand culture system designed to allow the mechanical impedance of the root growth environment to be adjusted independently of water and nutrient availability.ResultsImpeded roots grew more steeply than non-impeded roots: the angular spread of roots decreased from 55° to 43° from the vertical, but the genotypic effects were weak. Root impedance reduced leaf elongation and the number of tillers. Leaf area and total root length provided a common relationship across all genotype x treatment combinations. Leaf stunting in Cadenza was more severe.ConclusionOur data support the hypothesis that the severity of leaf stunting due to root impedance is related to the Rht allele. Impeded roots had a smaller angular spread.

Effects of root iron plaque on selenite and selenate dynamics in rhizosphere and uptake by rice (Oryza sativa)

Iron plaque commonly forms on rice root surfaces under flooded conditions. However, little is known about the role of iron plaque in Se movement from rhizosphere to plant. A compartmented soil-quartz sand culture system was applied to investigate the effects of iron plaque on Se uptake by rice and document Se speciation dynamics in soil solution under flooded conditions. Rice seedlings were planted in a nylon bag containing sand and surrounded by soil amended with Se combined at rates of 0 or 0.5 mg of Se kg−1 of soil in the form of selenate or selenite. Plants were harvested at seedling stage and at maturity. Fe and Se concentrations in soil solution, in DCB extracts and Se concentrations in rice roots and shoots were determined. A visible reddish coating on root surfaces could be observed when sampled at the seedling stage and at maturity. Iron plaque on root surfaces greatly influenced Se uptake and had a higher affinity for selenite. The distribution of Se in different components of rice seedlings followed iron plaque > shoot > root, while it followed shoot > root > iron plaque at maturity. The addition of Se initially increased the soluble Se concentrations, and selenate was the main species in soil solution. Iron plaque greatly influenced Se uptake and might act as a pool to Se uptake during rice growth. Selenate or selenite addition to paddy soil showed the same effect in increasing Se concentrations in rice grain.

Variations of growth, nitrogen accumulation and nitrogen use efficiency among 18 willow clones under two nitrogen regimes

Willows (Salix spp.) have excellent capacity for acquiring nutrients, and are widely used for removing excess nutrients in wastewater purification system. In this study, 18 willow clones were evaluated in terms of growth parameters, nitrogen (N) accumulation and N use efficiency under two N regimes (low N and high N) with a sand culture system. Clonal differences were observed in biomass production, relative growth rate, N accumulation and use efficiency under two N regimes, which were contributed to the clone level. For all clones, nitrogen use efficiency was lower under high N condition than under low N condition. Nitrogen removal efficiency differed by 7-fold (low N regime) and 10-fold (high N regime) based on shoot N contents between the lowest and the highest clone. Among all the clones, J799 had the highest N content in shoots, showing largest N removal potential. These results confirmed that growth analysis and nutrient use strategy are efficient method of selecting Salix clones for improving the N removal potential.

Effect of nutrient solution and foliar fertilizers on the characteristics of growth and yield of potato plant Solanum tuberosum L. by sand culture systems

This study was carried out in green houses at the Twaitha site of Agricultural research directorate, Ministry of Science and Technology during 10 December 2010 to 20 February 2011. The study included effect of combination to fertilizer nutrient solution and foliar application on plants potato in the developing sand culture system Randomized Complete Block Design RCBD were adapted this study 8 treatments of fertilizer. F0 without fertilizer, F1nutrient solution, F2 spray megafol activated amino, F3 spray magnum urea &amp; phosphate, F4 spray agroleaf composite balanced, F1F2 nutrient solution + spraying megafol, F1F3 nutrient solution +spraying magnum and F1F4 nutrient solution + spraying agroleaf . L.S.D. were used to compare the means at 5% level of significances: - The results showed superiority of all treatments fertilizer (nutrient solution with the fertilizer) to the attributes under study compared with control treatment F0, treatment of F1F4 significantly increased number of stem, high of plant cm, leaf area Dcm2 and dry weight of shoots of sand culture reached 4.33 stem/plant ,61.67 cm ,97.35 Dcm2 , 30.40 g Compared with the control treatment. And treatment F1F4 was significantly increased the yield of plant reached 672.00g and no significantly difference with F1F3, F1F2 treatments, while the ratio decreased in the F0 treatment reached 229.00g.

The involvement of gibberellin signalling in the effect of soil resistance to root penetration on leaf elongation and tiller number in wheat

The concept of root-sourced chemical signals that affect shoot growth in response to drought is widely reported; in particular the role of ABA in regulating stomatal conductance has received much attention. ABA, alone, does not fully explain all the effects of abiotic stresses in the root zone on shoot architecture. An increase in mechanical impedance, which can occur on even relatively modest soil drying, results in reduced root and shoot growth, processes that are potentially regulated by gibberellins (GAs). In this study we explored the role of mechanical impedance and exogenous gibberellin (GA3) on root and shoot architecture in wheat seedlings containing the Rht-B1a (tall), Rht-B1b (semi-dwarf) or Rht-B1c (dwarf) alleles in the April-Bearded or Mercia backgrounds. Our experiments were based on the use of the sand culture system which allows the mechanical impedance of the root growth environment to remain constant and independent of water and nutrient availability. We investigated the effects of the application of exogenous GA3 to the root system. We found that impeding soil reduced leaf elongation in the tall and semi-dwarf lines, confirming the stunting effect of mechanical impedance which is widely reported. However, leaf elongation in the dwarf lines was not affected by root impedance. Application of GA3 to the roots restored leaf elongation in the tall and semi-dwarf lines growing in impeding soil, with some growth response even in the dwarf line, the longest leaves being obtained when GA was applied to impeded roots of a tall line. Both exogenous GA and root impedance reduced the number of tillers, but there was no interaction with the Rht genotype. The genetic background did not affect the results. We suggest that the GA signalling pathway has an unidentified role in the leaf elongation response to mechanical impedance to root growth.

Physiological Responses and Tolerance Threshold to Cadmium Contamination in Eremochloa Ophiuroides

Plant tolerance is one of the preconditions in soil phytoremediation. The physiological responses and tolerance threshold of centipedegrass (Eremochloa ophiuroides) were investigated under eight different Cd concentrations (0, 60, 120, 180, 240, 300, 360, and 420 mg Cd kg−1) in a sand culture system. The results showed that turf quality, leaf relative water content (RWC), leaf electrolyte leakage (EL), leaf osmotic potential did not show significant changes under 180 mg Cd kg−1 compared with the control, and relative growth rate (RGR), turf density, leaf chlorophyll content, photochemical efficiency (Fv/Fm) did not show significant changes under 240 mg Cd kg−1 compared with the control throughout the whole experiment. Regression analysis was used to determine the threshold Cd concentrations for each physiological parameter and the most sensitive parameter occurred by RWC of 197 mg Cd kg−1 which was chose as Cd tolerance threshold in centipedegrass because under this concentration the plant did not show any significant difference with the control in all growth and physiological parameters measured in this experiment. The phytoextration rate of centipedegrass reached 0.87% in 36 d under 180 mg Cd kg−1 treatment.

Estimating total nitrogen deposition in agroecosystems in northern China during the wheat cropping season

Atmospheric nitrogen (N) deposition has been poorly documented in northern China, an in- tensive agricultural and industrial region with large emissions of NHx and NOy. To quantify N deposition, total airborne N deposition was determined at three agricultural sites using a manual integrated total ni- trogen input (ITNI) system during growth of winter wheat (Triticum aestivum L.) and Italian ryegrass (Lolium multiflorum Lam.) from September 2005 to May 2006. Total estimated N deposition averaged 54.9 and 43.2 kg N/hm 2 across the three sites when wheat was grown to flowering and maturing, respectively. The aver- age value was 50.2 kg N/hm 2 when ryegrass was the indicator plant. Both indicator species gave similar total airborne N input results. The intermediate level of N supplied resulted in the highest N deposition, and the ratio of N acquired from deposition to total N content of the whole system decreased with increasing N supply to the roots. The contribution of atmospheric N to the total N content of the wheat and ryegrass sand culture systems ranged from 10% to 24%.

Mobility and plant-availability of Cd(II) and Pb(II) adsorbed on zeolite and bentonite

The objective of this work was to study the desorption behaviour and plant-availability of Cd(II) and Pb(II) adsorbed on zeolite and bentonite in a batch and a pot (sand) culture experiment. In a sequential desorption experiment Cd(II) and Pb(II) desorption from the zeolite (at 50, 75 and 100% of maximum adsorption capacity, SC max) equilibrated with 0.01 M Ca(NO 3) 2 was lower as compared to bentonite at all the metal ion loading rates. Amounts of 3, 14 and 31% of the initially adsorbed Pb(II) were desorbed from the bentonite but only 1, 3 and 5% from the zeolite. The corresponding desorbed quantities of Cd(II) were 53, 65 and 71% for bentonite and 41, 33 and 21% for zeolite. In the pot (sand) culture experiments in a greenhouse, corn seedlings were planted in pots filled with quartz sand mixed with zeolite or bentonite enriched with Cd(II) or Pb(II). The concentration of Cd(II) and Pb(II) in the corn roots and shoots grown in the enriched bentonite–sand culture system was significantly higher than those planted in the enriched zeolite–sand culture indicating a stronger immobilizing of Cd(II) and Pb(II) by the zeolite.

Tolerance of seven perennial grasses to high nickel in sand culture

Environmental context.High concentrations of Ni in soil may occur either naturally or as a result of human activities. We used a sand culture system to investigate the suitability of seven perennial grasses for the revegetation of Ni-contaminated sites. This study provides information on the toxic effects of Ni on plant growth and gives consideration to the health of animals consuming these plants, thereby increasing the accuracy of risk assessments. Abstract.Although grasses are commonly used to revegetate disturbed areas, comparatively little is known regarding the tolerance of perennial grasses to toxic levels of trace metals. A sand culture experiment was conducted to investigate the tolerance of seven perennial grasses to high concentrations of Ni. The activity of Ni2+ in solution that resulted in a 50% reduction in shoot growth ranged from 50 µM for Sabi grass (Urochloa mosambicensis (Hack.) Dandy cv. Saraji) to 13 µM for curly Mitchell grass (Astrebla lappacea (Lindl.) Domin). In most grasses, growth in the high-Ni2+ treatments resulted in shoot Ni concentrations at or above the toxicity threshold for consumption by cattle (100 µg Ni g–1). Based upon their tolerance to Ni, and the extent to which they translocate Ni to the shoots, Sabi grass, signal grass (Brachiaria decumbens Stapf. cv. Basilisk) and buffel grass (Cenchrus ciliaris (L.) cv. Biloela) appear well suited for the phytostabilisation of Ni-contaminated sites in subtropical and tropical regions.

Measurement and Interpretation of Salinity Tolerance in Four Perennial Grasses

ABSTRACT Whilst the topic of soil salinity has received a substantive research effort over the years, the accurate measurement and interpretation of salinity tolerance data remain problematic. The tolerance of four perennial grass species (non-halophytes) to sodium chloride (NaCl) dominated salinity was determined in a free-flowing sand culture system. Although the salinity tolerance of non-halophytes is often represented by the threshold salinity model (bent-stick model), none of the species in the current study displayed any observable salinity threshold. Further, the observed yield decrease was not linear as suggested by the model. On re-examination of earlier datasets, we conclude that the threshold salinity model does not adequately describe the physiological processes limiting growth of non-halophytes in saline soils. Therefore, the use of the threshold salinity model is not recommended for non-halophytes, but rather, a model which more accurately reflects the physiological response observed in these saline soils, such as an exponential regression curve.

Tolerance of perennial grasses to high copper in sand culture

Environmental context. Copper (Cu) is an essential element for the growth of plants, but various anthropogenic activities such as mining, smelting, disposal of wastes, and the use of Cu-containing fungicides have resulted in substantial Cu contamination at sites throughout the world. We used a sand-culture system to investigate the tolerance of seven perennial grasses to toxic levels of Cu. This study provides information to assist in the selection of grasses for the revegetation and stabilisation of Cu-contaminated sites. Abstract. Although perennial grasses are commonly used to revegetate and stabilise disturbed sites, comparatively little is known of their tolerance to Cu. High Cu in solution reduced growth in all grasses, with the critical solution Cu concentration (corresponding to a 50% reduction in shoot fresh mass) ranging &gt;5-fold, from 1.7 μM in Queensland blue grass (Dichanthium sericeum (R.Br.) A. Camus) to 10 μM in Sabi grass (Urochloa mosambicensis (Hack.) Dandy cv. Saraji). An increase in Cu in solution resulted in elevated Cu concentration in shoots of all but one species, increasing from 6 to 11 μg g–1 at 0 μM Cu to 13 to 25 μg g–1 at 11 μM Cu. The comparatively small magnitude of this increase to a concentration below the animal toxicity threshold suggests that phytotoxicity is likely to be of more environmental concern than is the uptake of Cu into the shoots (and its subsequent consumption by fauna).