Silicon (Si) as silicic acid, Si(OH)4 offers several benefits to the growth of plants, especially under adverse environmental conditions. Therefore, the present study aimed to assess the role of exogenous Si treatments (0.5 and 1.0 mM) in the tolerance of Fagopyrum esculentum Moench to Al stress applied at two different concentrations (0.2 and 0.4 mM). A set of agrophysiological, biochemical and antioxidant parameters were evaluated during the investigation. The exogenous Si application to Fagopyrum esculentum plants exposed to Al treatments significantly modulated the physiological and antioxidant responses to overcome the Al phytotoxicity and provide beneficial effects. The results indicated that the application of different doses of Al significantly affected the physiological parameters viz., plant growth, tolerance index, biomass accumulation (BA), relative water content (RWC), lipid peroxidation (LP), membrane stability index (MSI) and reduced glutathione (GSH) content. Likewise, aluminum -treated leaves also displayed increased hydrogen peroxide accumulation signifying the extent of the damage in F. esculentum. However, the individual and combined doses of silicon (Si) yielded beneficial effects on the physiological and antioxidant attributes. Multivariate analysis also suggested that individual and combined doses of Si improved physiological (root length (RL), shoot length (SL), root and shoot tolerance index (TI), BA, RWC, MSI and osmolytes) and modulates antioxidant defense enzymes (SOD, APX, GPX, CAT, GR and GST). The study reveals that exogenous Si application acts as a potent stress -modulating agent either via the formation of aluminum -silicate complexes or by improving the efficiency of antioxidant enzymatic activities in Al -contaminated soils. (c) 2024 SAAB. Published by Elsevier B.V. All rights reserved.

Questions: Are there changes in species composition of the oceanic, Low-Arctic tundra vegetation after 40 years? Can possible changes be attributed to climate change? Location: Ammassalik Island near Tasiilaq, Southeast Greenland. Methods: Species composition and cover of 11 key vegetation types were recorded in 110 vegetation survey plots in 1968-1969 and in 11 permanent plots in 1981. Recording was repeated in 2007. Temporal changes in species composition and cover between the surveys were tested using permutation tests linked with constrained ordinations for vegetation types, and Mann-Whitney tests for individual species. Changes in vegetation were related to climate change. Results: Although climate became warmer over the studied period, most of the vegetation types showed minor changes. The changes were most conspicuous in mire and snowbed vegetation, such as the Carex rariflora mire and Hylocomium splendens snowbed. In the C. rariflora mire, species number and cover of vascular plants and cover of bryophytes increased, whereas in the H. splendens snowbed species numbers of vascular plants, bryophytes, and also lichens increased. Lichen richness increased in the Carex bigelowii snowbed and cover of bryophytes in the Salix herbacea snowbed. No such changes occurred in the Alchemilla glomerulans meadow, Alchemilla alpina snowbed and Phyllodoce coerulea heath. There was no change of species composition within the Salix glauca scrub, A. alpina snowbed, lichen grassland and the Empetrum nigrum and Phyllodoce coerulea heaths. Most changes resulted from increasing frequency or cover of some species; there were very few decreasing species. Most of the increasing species indicate drier substrate conditions. Conclusions: Only minor changes in species composition and cover were detected in the vegetation types studied. These changes were probably caused by milder winters and warmer summers during the years before the 2007 sampling. Climate warming may have reduced the duration of snow cover and soil moisture, particularly in snowbed and mire habitats, where species composition change was most pronounced. However, its magnitude was insufficient to cause a major change in species composition. Thus, on the level of plant community types, tundra vegetation near Tasiilaq was rather stable over the last 40 years.