Techniques for experiments with pot plants

Summary Simple, standardized techniques for the raising of pot plants on glasshouse benches are described. The techniques are especially suitable for the statistical assessment of quantitative and qualitative variations in plant populations by the geneticiest, plant breeder and plant physiologist.     

Growth effects of the vesicular-arbuscular mycorrhizal fungusGlomus constrictum on maize plants in pot trials

Maize plants were inoculated withGlomus constrictum in soil of low phosphorus content amended with five rates of P in the form of Ca₃(PO₄)₂. Maize dry matter yield was increased by addition of P up to 30 and/or 60 mg P/kg soil, above that it began to decrease to reach at 100 mg P/kg a value similar to that of the control. At all P levels used, the shoot and root (total plant) dry mass of inoculated plants was significantly increased compared with the non-inoculated controls and this increment ranged in some cases between 50 and 70%. Development of vesicular-arbuscular mycorrhizal fungus (VAM) monitored in terms of P contents in dry matter of maize revealed that the P content of plants not inoculated withG. constrictum was not influenced by P addition to soil. On the other hand, P content of maize plants inoculated with VAM was dramatically increased by increasing P levels of soil and was maximum at 30 mg P; above that it began to decline. Mycorrhizal root infection (expressed as percentage of root length infected) increased by increasing the P concentrations above the soil basal level up to 80 mg P where the infected root length was 72% of the total root length after 28 d of planting. The increase in VAM spore formation in soil was similar to that of root infection except that the highest spore number was sieved from soil at 60 mg P/kg soil.     

Accumulation and toxicity of chloride in bean plants

Summary Chloride tends to accumulate in tissues, particularly leaves, of some plants to toxic levels. Chloride accumulation in plants is closely related to Cl concentration in the external solution and the genotype.An experiment was conducted to study the rate of Cl accumulation in bean plants under greenhouse conditions and to determine the toxic levels of this anion in the leaves of red kidney beans. Plants were grown in large tanks containing a basal nutrient solution, salinized with either NaCl or Na₂SO₄ to produce 80 meq/l solutions of these two salts. Control plants were grown in nonsalinized nutrient solutiosn. Salt-treated plants were harvested at different time intervals and analyzed. Chemical analysis of leaves showed that accumulation of chloride was different from that of other ions derived from salines. The leaf-Cl accumulation was shown to be dependent on Cl concentration of the culture solution as well as the duration of the experiment. The data also revealed two processes of rapid Cl accumulation in the leaves of bean plants when a relatively high concentration of this ion is present in the external solution. These are: (a) a rapid Cl accumulation occurring between transplanting and the first harvest; (b) a second rapid Cl accumulation occurring after the fourth harvest to the end of the experiment leading to a toxic concentration of Cl in the leaves. The second rapid absorption period was absent for the other ions derived from salines.     

Accumulation of vismione A in regenerated plants ofVismia guianensis DC

Summary The accumulation and tissue localization of antitumoral vismione A in the in vitro regenerated plants ofVismia guianensis DC. were investigated. Chemical and light and electron-microscope analyses revealed that vismione A, detected as phenolic black globules in the vacuoles, was accumulated in the leaf, mainly in the palisade, and in small amounts in the primary body of the stem (epidermis and first cortical layer). Vismione A is neither present in the secretory cavities and ducts of the leaf nor in the secretory ducts of the stem. In the leaves of the regenerated plants, the amount of vismione A reached 0.5% FW, compared to 0.1% in the leaves of the parent plant. The optimization of the in vitro regeneration of plants was obtained in MS medium enriched with BAP (1 ppm). The best results for the rooting of regenerated plants were achieved with MS medium containing half-strength salts and 10^–5 MIBA.Abbreviations APT attached proton test - BAP 6-benzyl-aminopurine - CC column chromatography - 2,4-D 2,4-dichlorophenoxyacetic acid - EtOAc ethyl acetate - IBA indole-3-butyric acid - MeOH methanol - MS Murashige and Skoog - NAA -naphthaleneacetic acid - NMR nuclear magnetic resonance - TEM transmission electron microscopy - TLC thin layer chromatography - UV ultraviolet     

Accumulation of a metallo-carboxypeptidase inhibitor in leaves of wounded potato plants

Mechanical wounding of young potato plants induces over a two fold increase in inhibitory activity against the bovine pancreatic metalloexopeptidase carboxypeptidase A. This increase in inhibitory activity in both wounded and unwounded leaves parallels the increases of two inhibitors of bovine serine endopeptidases, trypsin and chymotrypsin. This suggests that the Proteinase Inhibitor Inducing Factor is regulating the synthesis and accumulation of inhibitors of two different mechanistic classes of proteases found in animals and microorganisms. These increases in antiproteolytic activities due to wounding support the hypothesis that this response is part of a defense mechanism directed against plant pests.     

Accumulation and radial transport of ions from potassium salts by cucumber roots

Accumulation of K(+) is insensitive to the anion supplied with it at a solution concentration below 1 mm. Rates of K(+) transport to the xylem from the same solutions are, however, dependent upon the anion present and decrease in the order NO(3) (-) > Cl(-) > SO(4) (2-). Parallel effects on rates of exudation and anion transport result from kind and concentration of anion supplied and time of exposure to the solution. When high K salt concentrations are used, only linear relationships are found between solution concentrations and transport rates. However, ion concentration in the exudate increases more than external solution concentration, while exudation rate is unaffected. It is suggested that some of the ions transported are from compartments within the cells. At high solution concentrations KNO(3) results in more exudation and in higher ion concentration in the exudate than is found with KCl.     

Accumulation of magnetic nanoparticles in plants grown on soils of Apsheron peninsula

The disclosure of magnetic nanoparticles in five plant species growing in Apsheron peninsula have been detected by the EPR method. The EPR spectra of these nanoparticles proved to be similar to those of synthesized magnetic nanoparticles. The result demonstrated that plants are capable of absorbing magnetic nanoparticles from the soil. The accumulation of nanoparticles in plants is confirmed by the presence of a broad EPR signal whose maximum position of the low-field component changes from g = 2.38 and halfwidth of the signal of 32 mT at room temperature to g = 2.71 and 50-55 mT at 80 K. The intensity of the broad EPR signal for plants grown in radioactively contaminated areas (170-220 mkR per h) was substantially lower compared with plants grown on clean soil. The parameters of the broad EPR signal and its dependence on the temperature of recording were identical with those for synthetic magnetic nanoparticles. The photosynthetic activity and changes in the genome of irradiated plants by the analysis of PCR products were studied.     

Accumulation of magnetic nanoparticles in plants grown on soils of Apsheron peninsula

Magnetic nanoparticles in five plant species growing on the Apsheron peninsula have been detected by the EPR method. The EPR spectra of these nanoparticles proved to be similar to those of synthesized magnetic nanoparticles. The result demonstrated that plants are capable of absorbing magnetic nanoparticles from the soil. The accumulation of nanoparticles in plants is confirmed by the presence of a broad EPR signal whose maximum position of the low-field component changes from g = 2.38 and half-width of the signal of 32 mT at room temperature to g = 2.71 and 50–55 mT at 80 K. The intensity of the broad EPR signal for plants grown in radioactively contaminated areas (170‐220 μR/h) was substantially lower compared with plants grown on clean soil. The parameters of the broad EPR signal and its dependence on the temperature of recording were identical with those for synthetic magnetic nanoparticles. The photosynthetic activity and changes in the genome of irradiated plants by the analysis of PCR products were studied.     

梁子湖湿地植物的氮磷积累特征

采用野外测定结合室内分析的方法,探讨了梁子湖湿地植物对氮磷的积累特征。结果表明,湿地不同植物种类对氮磷的积累特征明显不同。浮游植物积累各种营养物质量最多,其体内全氮量平均为29.07g.kg-1,全磷量平均为9.53g.kg-1。梁子湖湿地各类植物氮磷含量的大小依次为浮游植物>浮叶植物>沉水植物>水稻>挺水植物。各类植物中氮磷积累的大小依次为浮叶植物>挺水植物>沉水植物>沼泽植物>水稻。梁子湖湿地水生植物氮磷营养元素的吸收系数大于湿生植物,各类植物氮元素的吸收系数均大于磷。     

Accumulation and reduction of nitrate in cereal plants dependent on N supply

Summary In pot experiments the NO ₃ ^– accumulation and the occurrence of nitrate reductase (NR) capacity of wheat plants were investigated depending on late N applications at tillering, shooting and heading. NO ₃ ^– is preferentially accumulated in the stems, while NR dominates in the leaves. NO ₃ ^– accumulation is enhanced by late N treatments especially if N supply at seeding is sufficient. NR capacity of the plants is stimulated by late nitrogen supply, but its increment rates decrease with increasing NO ₃ ^– accumulation.     

Contribution of plants to N 2 O emissions in soil-winter wheat ecosystem: pot and field experiments

Outdoor pot and field experiments were conducted to assess the role of growing plants in agricultural ecosystem N₂O emissions. N₂O emissions from plants were quantified as the difference in soil-crop system N₂O emissions before and immediately after cutting plants during the main growth stages in 2001–02 and 2002–03 winter wheat seasons. Emissions of N₂O from plants depended on biomass within the same plant developmental status. Field results indicated that the seasonal contribution of N₂O emissions from plants to ecosystem fluxes averaged 25%, ranging from 10% at wheat tillering to 62% at the heading stage. The fluxes of N₂O emissions from plants varied between 0.3 and 3.9 mg N₂O-N m⁻² day⁻¹ and its seasonal amount was equivalent to 0.23% of plant N released as N₂O. A N₂O emission coefficient (N₂O_E, mg N₂O-N g⁻¹ C day⁻¹), defined as N₂O-N emission in milligrams from per gram carbon of plant dry matter within a day, was represented by a 5-fold variation ranging from 0.021 to 0.004 mg N₂O-N g C⁻¹ day⁻¹. A linear relationship (y=0.4611x+0.0015, r ²=0.9352, p < 0.001) between N₂O_E (y) and plant dark respiration rate (x, mg CO₂-C g C⁻¹ day⁻¹) suggested that in the absence of photosynthesis, some N₂O production in plant N assimilation was associated with plant respiration. Although this study could not show whether N₂O was produced or transferred by winter wheat plants, these results indicated an important role for higher plant in N₂O exchange. Identifying its potential contribution is critical for understanding agricultural ecosystem N₂O sources.     

Facilitation in the conceptual melting pot

1. Here we present an introduction to this issue's Special Feature arising from the British Ecological Society Symposium: Facilitation in Plant Communities (20–22 April 2009).
2. Papers in the Special Feature demonstrate the benefits that arise from cross-system application of general concepts, for example, the well-known stress gradient hypothesis. Such comparisons challenge our definition of facilitation, as well as our pre-conceptions on the nature of intermediary organisms.
3. We suggest that under some circumstances a clear definition of the two-way nature of interactions is essential, e.g. when considering the evolutionary implications of facilitation. In other cases, however, we can perhaps be more relaxed, e.g. when facilitation is a component of conservation ecology.
4. Synthesis . Overall we believe that establishing facilitation as an independent concept has driven substantial progress towards a clearer understanding of how ecological systems work. Through the links established by work such as that presented in this Special Feature, we believe this field will continue to make rapid progress and aid ecological understanding in general.     

Root length density and water uptake distributions of winter wheat under sub-irrigation

As the critical information to study flow transport in soil–plant systems, root distributions and root-water-uptake (RWU) patterns have been studied extensively. However, most root distribution data in the past were collected under surface irrigation. Less research has been conducted to characterize root distributions under sub-irrigation. The objectives of this study were to (1) test if the generalized function of normalized root length density (NRLD) in the literature was applicable to root distributions of winter wheat under natural sub-irrigation, which provides water from subsurface by capillary rise from the water table, and (2) estimate RWU distributions of winter wheat under natural sub-irrigation. Column experiments were conducted to study the distributions of root length density (RLD) and RWU of winter wheat (Triticum aestivum L. cv. Nongda 189) during a growing period of 57 days from planting to tillering stages under surface irrigation and natural sub-irrigation. Data of root distributions and soil water content were collected in the experiments with different treatments of irrigation levels. Results showed that the RLD distributions of winter wheat under both surface irrigation and natural sub-irrigation were of similar patterns. The NRLD distributions under sub-irrigation were adequately characterized by the generalized function. An inverse method was employed to estimate the average RWU rate distributions of winter wheat. In addition, based on the potential RWU coefficient and the NRLD function, a simple approach was developed to predict RWU rates at different depths. The predicted RWU rates had a good agreement with the estimated RWU rate distributions using the inverse method.Section editor: R. E. Munns     

Accumulation and volatilization of different chemical species of selenium by plants

Selenium (Se) removal from polluted waters and soils is especially complicated and highly expensive. Phytoremediation has been suggested as a low-cost, efficient technology for Se removal. Plants remove Se by uptake and accumulation in their tissues, and by volatilization into the atmosphere as a harmless gas. Unraveling the mechanisms of Se uptake and volatilization in plants may lead to ways of increasing the efficiency of the phytoremediation process. The objectives of this study were: (i) to determine the effect of different Se forms in the root substrate on the capacity of some plant species to take up and volatilize Se; (ii) to determine the chemical species of Se in different plant parts after the plants were supplied with various forms of Se; and (iii) to determine the influence of increasing sulfate levels on plant uptake, translocation, and volatilization of different Se species. Plants of broccoli (Brassica oleracea var. botrytis L.), Indian mustard (Brassica juncea L.), sugarbeet (Beta vulgaris L.) and rice (Oryza sativa L.) were grown hydroponically in growth chambers and treated for 1 week with 20 μM Se as Na₂SeO₄, Na₂SeO₃ or L-selenomethionine (SeMeth) and increasing sulfate levels. The data show that shoots of SeO₄-supplied plants accumulated the greatest amount of Se, followed by those supplied with SeMeth then SeO₃. In roots, the highest Se concentrations were attained when SeMeth was supplied, followed by SeO₃, then SeO₄. The rate of Se volatilization by plants followed the same pattern as that of Se accumulation in roots, but the differences were greater. Speciation analysis (X-ray absorption spectroscopy) showed that most of the Se taken up by SeO₄-supplied plants remained unchanged, whereas plants supplied with SeO₃ or SeMeth contained only SeMeth-like species. Increasing the sulfate level from 0.25 mM to 10 mM inhibited SeO₃ and SeMeth uptake by 33% and 15–25%, respectively, as compared to an inhibition of 90% of SeO₄ uptake. Similar results were observed with regard to sulfate effects on volatilization. We conclude that reduction from SeO₄ to SeO₃ appears to be a rate-limiting step in the production of volatile Se compounds by plants. Inhibitory effects of sulfate on the uptake and volatilization of Se may be reduced substantially if Se is supplied as, or converted to, SeO₃ and/or SeMeth rather than SeO₄. Received: 27 February 1998 / Accepted: 30 March 1998     

Accumulation of di-n-butylphthalate in plants and its effect on pigment and protein content

Seedlings of radish ( Raphanus salivas L. cv. Cherry Belle) and wheat ( Triticum aestivum L. cv. Starke II, Weibull) placed in air containing vapour of di- n -butyl-phthalate accumulate phthalate to a concentration that is 10⁶ times that of the surrounding air within 3 days. Particularly high accumulation is found in the cuticular and wax layers. Plants earlier found not to respond to di- n -butylphthalate (wheat) show toxic symptoms (carotenoid and chlorophyll deficiency in strong light, conco-mittant with chloroplast destruction and swollen mitochondria) when the phthalate concentration is further increased by addition to the nutrient medium. Phthalate-affected, white leaves lack the protein moieties normally belonging to the light harvesting complex.