1,210 publications from this institution
The Bismarck palm (Bismarckia nobilis Hildebr. & H. Wendl), with blue-gray leaves, is an important ornamental palm commonly planted along the highways in central and south Florida. During May of 2017, severe discoloration of the younger leaves of a Bismarck palm was observed in a roadside landscape in Manatee County, Florida. Symptoms of Texas Phoenix palm decline can include premature fruit drop, death of inflorescences, more than usual discoloration of the oldest leaves, and death of the spear leaf. The presence of the 16SrIV-D phytoplasma was confirmed on Bismarck palm.
Much of the research geared toward understanding the nitrogen (N) cycle, and how management options affect it, has failed to examine one of the potentially most important pools of N in the system, dissolved organic N (DON). As DON forms the critical link between solid organic N and the subsequent production of ammonium and nitrate, it is surprising that it is remains relatively understudied, particularly in relation to low-input agricultural systems. Ligand exchange between the dissolved organic matter and carboxyl or hydroxyl groups on the surface of soil minerals is thought to be an important mechanism for sorption, although a number of other mechanisms have also been proposed. Nonproteinaceous amino acids are also of significance, particularly in the rhizosphere, where, for example, their excretion by graminaceous plant roots aids the uptake of Fe and possibly other micronutrients from soil. Uptake may occur via a single transporter that is capable of transporting many different amino acids.
This study was conducted to evaluate the efficiency of diammonium phosphate (DAP), agricultural limestone (lime), and green‐waste compost mixed with 30% treated sewage sludge (GCS) applied alone or in combination as chemical immobilization treatment using tomato as a test crop. Mine waste was collected from an abandoned copper‐mine tailing site at Mynydd Parys, Anglesey (UK). Lime was applied at the rate of CaCO 3 equivalent (CCE, pH = 7), DAP at the rate of 23 g P per kg substrate, and 10% by weight, GCS as sole application. Half rate of each amendment was also tested as a combined treatment and an untreated substrate (control). Plant‐available metals (Cd, Cu, Fe, Pb, and Zn) were measured in substrate with conventional diethylenetriaminepentaacetic acid (DTPA) and sequential Ca(NO 3 ) 2 extraction. Plant–dry biomass yield was significantly ( p < 0.001) increased by the combined application of all the three amendments while sole application of DAP reduced yield by 4‐fold compared to unamended soil probably due to P toxicity. Addition of lime reduced the DTPA‐extractable Cu, Fe, and Zn by 75%, 81%, and 85%, respectively, while Pb availability was reduced by 88% in combined DAP + lime + GCS treatment compared to control. The extraction capacity of DTPA was higher than that of Ca(NO 3 ) 2 by 3‐fold for Cu and Fe, 8‐fold for Pb, and 2‐fold for Zn. The leaf‐tissue concentrations of Cu and Fe were reduced by 77% and 83% in the lime + GCS amendment, respectively, while both Pb and Zn were reduced by 89% and 33%, respectively, in substrate treated with the combined application of all three amendments. These results suggest that alkaline amendments (both lime and GCS) were effective in reducing the phytoavailability of Cu, Fe, and Zn while DAP mixed with either GCS or lime was effective in reducing Pb availability.
Brachiaria decumbens and Brachiaria ruziziensis are used as fodder crops in central and south America. Both species are very resistant to aluminium (Al) toxicity, Brachiaria decumbens being completely unaffected by 200 μM Al treatment, while the less resistant...
The widespread use of plastic products in agriculture has introduced micro-nano plastics (MNPs) and dibutyl phthalate (DBP) into soil ecosystems, disrupting microbial communities and altering metabolite profiles. However, their effects on the rhizosphere soil characteristics of medicinal plants like dandelion remain understudied. This study systematically examined the impact of PS NPs and DBP on rhizosphere microbial communities and metabolites by integrating high-throughput sequencing with liquid chromatography-mass spectrometry. Results demonstrated that individual and combined exposures to PS NPs and DBP decreased soil pH, organic matter content, and enzyme activities while reshaping the diversity, structure, and composition of rhizosphere bacteria and fungi. Notably, bacterial network stability and complexity increased under combined exposure, while fungal networks became more simplified, with a 33.72 % decrease in positive correlations. We identified potential PS NPs and DBP-degrading bacteria and biomarkers, including Nocardioides, Pseudarthrobacter, and Arenimonas. We revealed that co-exposure elevated differential soil metabolites associated with tyrosine metabolism and steroid biosynthesis. The significant positive associations between rhizosphere microorganisms and metabolites highlighted that metabolite accumulation was a key microbial response mechanism to stress. However, within the complex soil environment, the compensatory actions of microorganisms and metabolites were insufficient to mitigate the detrimental effects of PS NPs and DBP, resulting in continued inhibition of dandelion growth by 38.66 %. Consequently, these findings highlight that soil fungi and metabolism play key roles in responding to stress and influencing crop growth, providing novel insights into the impact of nanoparticle and plasticizer exposure on medicinal plant cultivation.
Biostimulants and bioinoculants offer the potential to enhance nutrient use efficiency within agricultural cropping systems and thus reduce the amount of mineral fertilizers needed to support crop growth. Considerable uncertainty, however, exists about their efficacy under different management regimes. The present field-based study investigated the effects of phosphorus (P) solubilizing bacteria (PSB) and mycorrhizal (AMF) inoculants in the presence of a range of mineral-based P fertilizers, including triple superphosphate (TSP), struvite and rock phosphate (RP), on the growth, yield, and P uptake of barley (Hordeum vulgare L.). Two consecutive field experiments performed in a low P soil (Eutric Cambisol) revealed that the bioinoculants (PSB and AMF) promoted plant P uptake and grain yield. Moreover, in comparison to P fertilizers lacking bio-inoculants, the application of external P sources combined with bio-inoculants led to significant increases in leaf P concentration, total P uptake, plant dry matter, grain P concentration, and crop yield. Grain yield significantly correlated with P uptake by roots and above-ground parts (i.e. stems, leaves, and spikes) as well as grain P concentration in both seasons. It is concluded that bioinoculants can help improve sustainable P use ultimately leading to greater sustainability of cropping systems and resilience in soil P cycling.
Plant roots and leaves can be colonized by human pathogenic bacteria, and accordingly some of the largest outbreaks of foodborne illness have been associated with salad leaves contaminated by E. coli O157. Integrated disease management strategies often exploit cultivar resistance to provide a level of protection from economically important plant pathogens; however, there is limited evidence of whether the genotype of the plant can also influence the extent of E. coli O157 colonization. To determine cultivar-specific effects on colonization by E. coli O157, we used 12 different cultivars of lettuce inoculated with a chromosomally lux-marked strain of E. coli O157:H7. Lettuce seedlings grown gnotobiotically in vitro did exhibit a differential cultivar-specific response to E. coli O157 colonization, although importantly there was no relationship between metabolic activity (measured as bioluminescence) and cell numbers. Metabolic activity was highest and lowest on the cultivars Vaila-winter gem and Dazzle respectively, and much higher in endophytic and tightly bound cells than in epiphytic and loosely bound cells. The cultivar effect was also evident in the rhizosphere of plants grown in compost, which suggests that cultivar-specific root exudate influences E. coli O157 activity. However, the influence of cultivar in the rhizosphere was the opposite to that in the phyllosphere, and the higher number and activity of E. coli O157 cells in the rhizosphere may be a consequence of them not being able to gain entry to the plant as effectively. If metabolic activity in the phyllosphere corresponds to a more prepared state of infectivity during human consumption, leaf internalization of E. coli O157 may pose more of a public health risk than leaf surface contamination alone.
Hyphal walls and, where possible, sclerotial walls of the plant pathogenic fungi Sclerotium cepivorum, S. rolfsii, S. tuliparum, Sclerotinia narcissicola, S.fructigena and Rhizoctonia solani have been examined by electron-microscope techniques and analytical methods, including X-ray diffraction, infrared absorption spectroscopy and paper chromatography. Infrared data, sugar analysis of hydrolysates and lytic experiments indicate that the composition of the walls of S. tuliparum differs markedly from that of other species of Sclerotium but is similar to Rhizoctonia. The other Sclerotium species are similar in wall composition to the species of Sclerotinia investigated.
S ummary Critical point‐drying is the standard method of preparation for scanning electron microscope studies of mycorrhizas. However, a number of recent studies on various biological specimens have shown disadvantages associated with this technique. These can be overcome by cryofixation, where specimens are frozen in liquid nitrogen and viewed in the frozen‐hydrated state. Three distinct types of mycorrhiza of Sitka spruce [Picea sitchensis (Bong.) Carr.] were critical point‐dried or cryofixed, and were examined for differences in the preservation of both surface features and internal morphology after fracturing or cutting the material transversely. Surface features were better preserved in frozen‐hydrated mycorrhizas than in critical point‐dried ones. Surface cementing matrix seen in the former was partially or entirely removed by critical point‐drying. Some distortion of both fungal and plant cells also occurred after the latter treatment, and cell contents retained in frozen‐hydrated specimens were often lost after critical point‐drying. Fractured frozen‐hydrated material revealed surface features of the cortical cells and lobed Hartig net hyphae.
No abstract is provided for this article.
pH is known to be a primary regulator of nutrient cycling in soil. Increasing soil acidity in agricultural systems has the potential to slow down N cycling and reduce N losses from leaching thereby enhancing sustainability and reducing pollution. We conducted a field experiment to investigate the impact of acidity on N leaching in arable and grassland agricultural systems. The results showed that nitrate (NO3 −) concentrations in soil water were greater under arable than under grassland. Soil acidification significantly lowered NO3 − concentrations in soil water over winter and spring under grassland, whilst in cereal plots a similar effect was only observed in spring. Our results suggest that soil acidification decreased nitrification causing an accumulation of NH4 + which was not subject to leaching. Dissolved organic nitrogen (DON) concentrations in soil water were significantly greater under arable than grassland. Soil acidification lowered concentrations of DON in soil water, usually to a greater extent in grassland than in arable plots. It was concluded that it may be possible to use careful soil pH management as a tool to control NO3 − leaching without compromising the quality of drainage water, and that this may be more effective on grassland than on arable crops.
