Honey bee (Apis mellifera ligustica) acetylcholinesterase enzyme activity and aversive conditioning following aluminum trichloride exposure

Background Aluminum is the third most prevalent element in the earth’s crust. In most conditions, it is tightly bound to form inaccessible compounds, however in low soil pH, the ionized form of aluminum can be taken up by plant roots and distributed throughout the plant tissue. Following this uptake, nectar and pollen concentrations in low soil pH regions can reach nearly 300 mg/kg. Inhibition of acetylcholinesterase (AChE) has been demonstrated following aluminum exposure in mammal and aquatic invertebrate species. In honey bees, behaviors consistent with AChE inhibition have been previously recorded; however, the physiological mechanism has not been tested, nor has aversive conditioning. Results This article presents results of ingested aqueous aluminum chloride exposure on AChE as well as acute exposure effects on aversive conditioning in an Apis mellifera ligustica hive. Contrary to previous findings, AChE activity significantly increased as compared to controls following exposure to 300 mg/L Al3+. In aversive conditioning studies, using an automated shuttlebox, there were time and dose-dependent effects on learning and reduced movement following 75 and 300 mg/L exposures. Conclusions These findings, in comparison to previous studies, suggest that aluminum toxicity in honey bees may depend on exposure period, subspecies, and study metrics. Further studies are encouraged at the moderate-high exposure concentrations as there may be multiple variables that affect toxicity which should be teased apart further.

Germination and vigor of lettuce seeds (Lactuca sativa L.) pelleted with homeopathic preparations Alumina and Calcarea carbonica subjected to toxic levels of aluminum.

Background: aluminum toxicity is the most important factor limiting the growth of plants in acid soils, whereas current treatments are unfeasible. For this reason, alternatives are sought for, among which homeopathic treatment. Aims: this study aimed at evaluating the influence of homeopathic preparations Alumina 6cH, Alumina 12cH, Calcarea carbonica 6cH and Calcarea carbonica 12cH on the germination and vigor of lettuce seeds subjected to toxic levels of aluminum in paper-solution. At the same time, it was sought to develop a new procedure to apply homeopathic preparations in plants (pelleting). Methods: the statistical design was entirely randomized (CRD) with 6 treatments and 4 repetitions. Treatments included: 1) pelleted seeds/talc + Alum 6 cH; 2) pelleted seeds/talc + Alum 12cH; 3) pelleted seed/talc + Calc 6cH; 4) pelleted seeds/talc + Calc 12cH; 5) pelleted seeds/talc + distilled water; 6) non pelleted seeds (control). Variables evaluated were: germination percentage (GP), germination speed index (GSI) and radicle length (RL). Results: there was significant difference in GSI and RL – variables that reflect the vigor of seeds - between the samples treated with homeopathic preparations and the controls Conclusions: homeopathic preparations Alumina 6cH and 12cH and Calcarea carbonica 6cH and 12cH had significant effect on the vigor of lettuce seeds subjected to stress conditions.

Selection of upland rice lines in advanced yield trials and response to abiotic stress

Tirtana A, Purwoko BP, Dewi IS, Trikoesoemaningtyas. 2021. Selection of upland rice lines in advanced yield trials and response to abiotic stress. Biodiversitas 22: 4694-4703. Breeding programs to obtain superior upland rice varieties with high productivity and adaptive in dryland must be prioritized to maximize the potential of dryland. This research aimed to obtain information on the agronomic performance of upland rice lines in advanced yield trials and select the best lines with high productivity and tolerance to drought stress and aluminum toxicity. Advanced yield trials were conducted from November 2016 until March 2017 in Bogor and Sukabumi using a randomized complete block design, where three replications were nested in the environments. Aluminum and drought stress evaluations were conducted at Muara Research Station, Bogor, in May-June 2018 and September-October 2018. Based on the selection index, twelve lines were selected with superior agronomic characters and high yield potential. These lines had characteristics as follows: days to harvesting (110.2-116.0 days), number of filled grains (70.6-101.3 grains), number of unfilled grains (27.9-58.4 grains), and productivity (2.2-2.9 tons ha-1). Evaluation of drought tolerance showed four lines with better drought tolerance than the drought-sensitive check IR20. The aluminum tolerance evaluation obtained two tolerant lines and nine lines with moderate responses to aluminum toxicity. The selected lines need to be further evaluated in multilocation trials.

Uncovering the transcriptional response of popcorn (Zea mays L. var. everta) under long-term aluminum toxicity

To date, the investigation of genes involved in Al resistance has focused mainly on microarrays and short periods of Al exposure. We investigated genes involved in the global response under Al stress by tracking the expression profile of two inbred popcorn lines with different Al sensitivity during 72 h of Al stress. A total of 1003 differentially expressed genes were identified in the Al-sensitive line, and 1751 were identified in the Al-resistant line, of which 273 were shared in both lines. Genes in the category of “response to abiotic stress” were present in both lines, but there was a higher number in the Al-resistant line. Transcription factors, genes involved in fatty acid biosynthesis, and genes involved in cell wall modifications were also detected. In the Al-resistant line, GST6 was identified as one of the key hub genes by co-expression network analysis, and ABC6 may play a role in the downstream regulation of CASP-like 5. In addition, we suggest a class of SWEET transporters that might be involved in the regulation of vacuolar sugar storage and may serve as mechanisms for Al resistance. The results and conclusions expand our understanding of the complex mechanisms involved in Al toxicity and provide a platform for future functional analyses and genomic studies of Al stress in popcorn.

Silicon Application Induced Alleviation of Aluminum Toxicity in Xaraés Palisadegrass

Aluminum (Al) toxicity is a major abiotic constraint for agricultural production in acidic soils that needs a sustainable solution to deal with plant tolerance. Silicon (Si) plays important roles in alleviating the harmful effects of Al in plants. The genus Urochloa includes most important grasses and hybrids, and it is currently used as pastures in the tropical regions. Xaraés palisadegrass (Urochloa brizantha cv. Xaraés) is a forage that is relatively tolerant to Al toxicity under field-grown conditions, which might be explained by the great uptake and accumulation of Si. However, studies are needed to access the benefits of Si application to alleviate Al toxicity on Xaraés palisadegrass nutritional status, production, and chemical–bromatological composition. The study was conducted under greenhouse conditions with the effect of five Si concentrations evaluated (0, 0.3, 0.6, 1.2, and 2.4 mM) as well as with nutrient solutions containing 1 mM Al in two sampling dates (two forage cuts). The following evaluations were performed: number of tillers and leaves, shoot biomass, N, P, K, Ca, Mg, S, B, Cu, Fe, Mn, Zn, Al, and Si concentration in leaf tissue, Al and Si concentration in root tissue, neutral detergent fiber (NDF), and acid detergent fiber (ADF) content in Xaraés palisadegrass shoot. Silicon supply affected the relation between Si and Al uptake by increasing root Al concentration in detriment to Al transport to the leaves, thereby alleviating Al toxicity in Xaraés palisadegrass. The concentrations between 1.4 and 1.6 mM Si in solution decreased roots to shoots Al translocation by 259% (from 3.26 to 1.26%), which contributed to a higher number of leaves per plot and led to a greater shoot dry mass without affecting tillering. Xaraés palisadegrass could be considered one of the greatest Si accumulator plants with Si content in leaves above 4.7% of dry mass. In addition, Si supply may benefit nutrient-use efficiency with enhanced plant growth and without compromising the chemical–bromatological content of Xaraés palisadegrass.