Intensive Reclamation of Landfills and Polygons for Solid Waste Disposal

This research proposed the use of one of the most effective complexons – oxyethylidenediphosphonic acid, namely its derivative compound – phenyldiacetic acid,for the active sorption matrices of humus of mineral origin. The application of active components that stimulate plant growth and photosynthesis processes in hybrid preparations during reclamation were also proposed. Keywords: recultivation of landfill, plant growth stimulation, phytoremediation

Visualising plant colonisation by beneficial bacteria: a key step to improve the understanding of plant–microbe interactions

Plants contain diverse microorganisms that interact with their hosts and with each other. Beneficial bacteria can be utilised on crops to protect plants against biotic and abiotic stresses and to stimulate plant growth. However, the behaviour of specific microorganisms on and within plants is still underexplored. Knowledge of bacterial colonisation behaviour and the precise ecological niches in a natural environment of a target strain can lead to better application and utilisation of these microorganisms for crop enhancement, in different plant soil environments, and for both biocontrol and biofertilisation approaches in organic and integrated protection systems. Understanding colonisation characteristics will also provide information on putative new strategies for maximising inoculation efficiency and thus crop enhancement. In this chapter, we set out how beneficial bacteria can colonise their host plants under various conditions and demonstrate how an understanding of plant colonisation can be used to improve bacterial application approaches.

Identification of endophytic and rhizosphere bacteria in rice (Oryza sativa L.) in the experimental field at Payakumbuh State Agriculture Polytechnic, West Sumatra, Indonesia

The decrease of soil fertility and fewer soil microorganisms will lower crop production, particularly rice, thus threatening the national food security program. This study is (a) to isolate and identify the bacteria in the endophytic and rhizosphere of rice plants (b) to study the bacteria from the endophytic and rhizosphere of rice plants which potentially stimulate plant growth. The experiment was carried out at the Laboratory of Food Crop Cultivation at Payakumbuh State Agriculture Polytechnic, Limapuluh Kota Regency, West Sumatra for four months. The sampling method was carried out by random sampling at rice planting in the Payakumbuh State Agriculture Polytechnic Experimental Field. Endophytic bacteria were taken from the root tissue of rice plants, and rhizosphere bacteria were taken from a layer of soil around rice roots. Isolation of bacteria was carried out by using the pour plate and scratchplate methods. Four bacteria were identified using the 16S rRNA sequencing method. The identification results showed that in the rice root tissue found the bacteria Chromobacterium rhizoryzae and Brevibacillus brevis. In the rice rhizosphere, Bacillus pseudomycoides and Bacillus thuringiensis are found. Bacteria are dominated by the Bacillus genera which can stimulate plant growth.

Characterization of plant growth promoting rhizobacteria of maize

Isolation and characterization of rhizobacteria are an effort to determine the ability of root colony bacteria to produce various compounds that can be used for various purposes of bio-fertilizer formulations and microbial-based industrial interests. This study aims to characterize biochemically, morphologically and physiologically as well as the ability of root bacteria in maize to produce hormones that can stimulate plant growth. There is a wide variety of isolates morphologically and biochemically, besides that there is the ability of bacterial isolates to physiologically dissolve phosphate, fix nitrogen, produce ACC-deaminase, IAA and GA enzymes.

Free Amino Acids and Methylglyoxal as Players in the Radiation Hormesis Effect after Low-Dose γ-Irradiation of Barley Seeds

Low-dose γ-irradiation can stimulate plant growth and development; however, the knowledge on the molecular mechanisms of such stimulation is yet fragmented. Irradiation of seeds leads to the mobilisation of endosperm resources and reallocation of available nitrogen to facilitate development. Based on the metabolomic analysis, several metabolites possibly involved in radiation stimulation were studied using the HPLC approach in barley cultivars after γ-irradiation of seeds. The comparison of changes in metabolite concentrations and changes in morphological traits after irradiation revealed seven metabolites that may be involved in the growth stimulation after γ-irradiation of barley seeds. Among them are free amino acids, such as γ-aminobutyric acid, β-alanine, arginine, lysine, glutamine, methionine, and a signalling compound methylglyoxal.

Effects of Supplemental Cations on Growth and Nitrogen Accumulation in Canna indica L.

The effects of supplemental cations on growth, nitrogen, and mineral accumulation were assessed in Canna indica L. Similar sized 45 days-old plants were grown on a nutrient solution modified from Hoagland and Arnon (1950). The different cations were added to generate 6 treatments (n=4): (i) control (no cation added), (ii) 2.5 mM K+, (iii) 2.5 mM Ca2+, (iv) 75 mM Na+, (v) 1.25 mM K+ + 1.25 mM Ca2+ and (vi) 2.5 mM Ca2+ + 75 mM Na+, respectively. An experiment was carried out in the greenhouse for 49 days. The study found that supplemental K+ and K++ Ca2+ increased plant growth and total biomass. The highest SER was found in plants receiving supplemental K+. In contrast, SERs, leaf areas, and total biomass decreased in Na+ or Na++Ca2+ supplemented plants. The accumulated NO3- concentration (at the whole plant level) was also highest in the plants with supplemental K+ and K++Ca2+. The total nitrogen accumulation was higher in the K+, Ca2+, and K++Ca2+ supplemented plants than in the control plants. The results suggest that supplemental cations particularly K+ can enhance plant growth and nitrogen accumulation in C. indica. Therefore, cation supplementation could be an alternative technique to stimulate plant growth and improve nitrate removal in constructed wetlands. Keywords: Constructed wetland, Nitrate removal, Potassium, Tropical wetland plants

Plant Uptake of Lactate-Bound Metals: A Sustainable Alternative to Metal Chlorides

Global agricultural intensification has prompted investigations into biostimulants to enhance plant nutrition and soil ecosystem processes. Metal lactates are an understudied class of organic micronutrient supplement that provide both a labile carbon source and mineral nutrition for plant and microbial growth. To gain a fundamental understanding of plant responses to metal lactates, we employed a series of sterile culture-vessel experiments to compare the uptake and toxicity of five metals (Zn, Mn, Cu, Ni, and Co) supplied in lactate and chloride salt form. Additionally, primary root growth in plate-grown Arabidopsis thaliana seedlings was used to determine optimal concentrations of each metal lactate. Our results suggest that uptake and utilization of metals in wheat (Triticum aestivum L.) when supplied in lactate form is comparable to that of metal chlorides. Metal lactates also have promotional growth effects on A. thaliana seedlings with optimal concentrations identified for Zn (0.5–1.0 µM), Mn (0.5–1.0 µM), Cu (0.5 µM), Ni (1.0 µM), and Co (0.5 µM) lactate. These findings present foundational evidence to support the use of metal lactates as potential crop biostimulants due to their ability to both supply nutrients and stimulate plant growth.

Impact of a bacterial consortium on the soil bacterial community structure and maize (Zea mays L.) cultivation

Microorganisms are often applied as biofertilizer to crops to stimulate plant growth, increase yields and reduce inorganic N application. The survival and proliferation of these allochthonous microorganisms in soil is a necessary requisite for them to promote plant growth. We applied a sterilized or unsterilized not commercialized bacterial consortium mixed with cow manure leachate used by a farmer as biofertilizer to maize (Zea mays L.) in a greenhouse experiment, while maize development and the bacterial community structure was determined just before the biofertilizer was applied a first time (day 44), after three applications (day 89) and after six application at the end of the experiment (day 130). Application of sterilized or unsterilized biofertilizer with pH 4.3 and 864 mg NH4+-N kg−1 had no significant effect on maize growth. The application of the biofertilizer dominated by Lactobacillus (relative abundance 11.90%) or the sterilized biofertilizer changed the relative abundance of a limited number of bacterial groups, i.e. Delftia, Halomonas, Lactobacillus and Stenotrophomonas, without altering significantly the bacterial community structure. Cultivation of maize, however, affected significantly the bacterial community structure, which showed large significant variations over time in the cultivated and uncultivated soil. It was concluded that the bacteria applied as a biofertilizer had only a limited effect on the relative abundance of these groups in uncultivated or soil cultivated with maize.

Comparative Study of Biostimulant Properties of Industrially and Experimentally Produced Humic Substances

Demand for new biological technologies in agriculture is ever growing, particularly with respect to the need of restoring the soil organic matter and soil fertility. Products of natural origin are developed to stimulate plant growth and productivity. Humic substances (HS) are the decay products of living matter, with high molecular weight and complex structure. Nowadays, HS are industrially produced from various materials like peat, lignin, soil and compost. The objective of this study is to make a comparison of the impact of HS of different origin on plant development. In total, eight different HS were used; four were extracted from various materials and four were commercially available products. To evaluate the stimulating effect, three different species of plants were used (Triticum aestivum, Sinapis alba, Lepidum sativum). The tests were carried out on Phytotestkit plates, germinating the seeds in different solutions of HS in various concentrations in dark, with or without added nutrient solution. Then, the growth parameters were measured. All tested products showed increase in at least some concentrations compared with the control sample. Significant differences in the stimulating effect of HS depending on their origin were found.