Heavy Metal-Induced Oxidative Stress on Seed Germination and Seedling Development: A Critical Review

Heavy metal contamination in soils can influence plants and animals, often leading to toxicosis. Heavy metals can impact various biochemical processes in plants, including enzyme and antioxidant production, protein mobilization and photosynthesis. Hydrolyzing enzymes play a major role in seed germination. Enzymes such as acid phosphatases, proteases and α-amylases are known to facilitate both seed germination and seedling growth via mobilizing nutrients in the endosperm. In the presence of heavy metals, starch is immobilized and nutrient sources become limited. Moreover, a reduction in proteolytic enzyme activity and an increase in protein and amino acid content can be observed under heavy metal stress. Proline, is an amino acid which is essential for cellular metabolism. Numerous studies have shown an increase in proline content under oxidative stress in higher plants. Furthermore, heat shock protein production has also been observed under heavy metal stress. The chloroplast small heat shock proteins (Hsp) reduce photosynthesis damage, rather than repair or help to recover from heavy metal-induced damage. Heavy metals are destructive substances for photosynthesis. They are involved in destabilizing enzymes, oxidizing photosystem II (PS II) and disrupting the electron transport chain and mineral metabolism. Although the physiological effects of Cd have been investigated thoroughly, other metals such as As, Cr, Hg, Cu and Pb have received relatively little attention. Among agricultural plants, rice has been studied extensively; additional studies are needed to characterize toxicities of different heavy metals on other crops. This review summarizes the current state of our understanding of the effects of heavy metal stress on seed germination and seedling development and highlights informational gaps and areas for future research

Role of Bacterial-Fungal Interactions on Heavy Metal Phytotoxicity in Serpentine Soil

This study was conducted to understand the role of bacterial–fungal interactions on heavy metal uptake by Zea mays plants. A pot experiment was conducted for 90 days with Z. mays in serpentine soil inoculated with a Gram-negative bacterium, fungus (Aspergilllus sp.) and both microbes to determine the effects of inoculation on nickel, manganese, chromium and cobalt concentrations in plant tissue and soil. Soil nutrients and soil enzyme activities were measured to determine the effect of inoculations on soil quality. Inoculation of microorganisms increased shoot and root biomass, and the maximum biomass was in the bacterial–fungal inoculation. This could be due to the solubilisation of phosphate and production of indole acetic acid. Although the combination treatment contributed to an increase in heavy metal uptake in Z. mays plants, the lowest translocation was observed in the combination treatment. Moreover, the soil available nitrogen, available phosphorous and total organic carbon content were increased with the microbial inoculation. Similarly, the soil dehydrogenase activity was higher as a result of microbial inoculation, whereas the highest dehydrogenase activity was reported in the combination inoculation. This study confirms the synergistic effect of bacterial–fungal inoculation as a soil-quality enhancer and as a plant-growth promoter in the presence of heavy metals

Impacts of river regulation and other anthropogenic activities on floodplain vegetation: A case study from Sri Lanka

Since the initiation of large-scale development in late 1970s, the Mahaweli River basin in Sri Lanka has experienced significant changes. However, no comprehensive study has been undertaken so far to evaluate the impacts of river regulation on associated ecosystems including floodplains in the downstream. The present study was aimed at identifying the impacts due to both river regulation and other anthropogenic activities on inland floodplain habitats (locally known as villus) located along the final stretch of the River Mahaweli before reaching the Indian Ocean. Four villus, Handapana (HAN), Bendiya (BEN), Karapola (KAR) and Gengala (GEN), were selected for the study. HAN and BEN can be considered as highly influenced (HI) by river regulation while KAR and GEN as less influenced (LI) due to their respective locations. Due to the absence of pre- regulation vegetation data, HI villus were compared with LI villus in order to explore any potential impacts of river regulation. Vegetation was enumerated using belt transect method. To find out other on-going anthropogenic impacts on these villu ecosystems, a survey was conducted using 100 individuals living in two villages located nearby. The results revealed some significant modification in the composition and the diversity of the vegetation, most possibly due to river regulation and other on-going anthropogenic activities. However, the most notable changes were recorded in the herbaceous layer. Some native aquatic herbaceous species have been completely absent over the period of two decades since the developmental activities begun, while some exotic invasive aquatic species (Eichhornia crassipes) dominated the herbaceous layer in HI villus threatening the survival of the remaining native species. Density and richness of lianas too diminished significantly in HI villus perhaps due to changes of micro-habitat conditions as a result of river regulation and also due to over-harvesting for commercial purposes. The results suggest that these ecosystems have been altered over the years due to culmination of factors including altered flow regimes following river regulation and some on-going human influences. The present study highlights the importance of regulating such human influences on villus including fishing and extracting cane and reed in order to protect these vulnerable ecosystems for future generations. The potential of these ecosystems to develop ecotourism has also been emphasized

Wireless Power Hotspot that Charges All of Your Devices

Each year, consumers carry an increasing number of gadgets on their person: mobile phones, tablets, smartwatches, etc. As a result, users must remember to recharge each device, every day. Wireless charging promises to free users from this burden, allowing devices to remain permanently unplugged. Today's wireless charging, however, is either limited to a single device, or is highly cumbersome, requiring the user to remove all of her wearable and handheld gadgets and place them on a charging pad. This paper introduces MultiSpot, a new wireless charging technology that can charge multiple devices, even as the user is wearing them or carrying them in her pocket. A MultiSpot charger acts as an access point for wireless power. When a user enters the vicinity of the MultiSpot charger, all of her gadgets start to charge automatically. We have prototyped MultiSpot and evaluated it using off-the-shelf mobile phones, smartwatches, and tablets. Our results show that MultiSpot can charge 6 devices at distances of up to 50cm.National Science Foundation (U.S.

Soil-Plant Microbiome: a promising frontier for research

No abstract availabl

Does over-dominance of <i>Bambusa</i> <i>bambos</i> (L.) Voss. alter abundance and richness of Arbuscular Mycorrhizal fungal community in forests?

Some areas under the Tropical Moist Evergreen Forests (TMEF), the major forest type in the Intermediate Zone of Sri Lanka, are heavily dominated by a native bamboo species, Bambusa bambos (L.) Voss. altering the hierarchical status and structure. The study evaluated whether the over-abundance of B. bambos has modified the arbuscular mycorrhizal fungal (AMF) communities in soil. Soil samples collected from bamboo-dominated (BM) and non-bamboo (NB) forest patches in three different locations viz., Moragolla, Maragomuwa and Galboda, were enumerated for AMF spores using wet sieving and decanting method. A total of 1,577 and 898 AMF spores were documented from BM and NB forest patches, respectively. A total of 14 different morphotypes belonged to the genera, Glomus, Scutellospora, Gigaspora and Acaulospora, were identified. Glomus was the dominant genus in all study sites, while Acaulospora the least. The mean abundance and richness of AMF spores were higher in BM than in NB, with the most notable difference observed at Maragomuwa. These site-specific variations may perhaps due to the differences in vegetation characteristics, edaphic properties and disturbance regimes. However, the community structure of AMF showed no conspicuous modifications due to the over-abundance of B. bambos. The findings reiterated the general understanding that any changes to the above-ground vegetation may incur impacts on the AMF. However, AMF community structure shows resilience to influences imposed by the dominance of a single species

Does over-abundance of <i>Bambusa</i> <i>bambos</i> (L.) Voss. alter edaphic properties?

A preliminary study was conducted to determine any modifications to basic soil properties following over-abundance of Bambusa bambos, a native bamboo species, that rapidly expanding its population in Intermediate and Dry Zone forests in Sri Lanka. Soil samples taken from representative sites of bamboo-dominated (BAM) and non-bamboo (NBM) forest patches were analyzed for pH, total nitrogen (N), phosphorus (P), soil moisture and microbial biomass carbon (MBC). A growth assay was carried out with Ricinus communis seedlings in BAM and NBM soils (sterilized/unsterilized) in a glasshouse. The soil analysis revealed significantly higher N, P and moisture in BAM soils than in NBM. BAM soils were clayey in nature compared to silty soils in NBM. Ricinus communis grown in BAM soils performed better throughout the experimental period, perhaps due to higher soil nutrients. Ricinus communis grow better in unsterilized soils irrespective of bamboo, indicating a facilitative role of soil microbes on the growth of plants. The preliminary results suggest that either B. bambos spread has the potential to increase the soil fertility status or else B. bambos expands its population preferably on nutrient-rich clayey soils. Therefore, further studies are needed in order to confirm the impacts of B. bambos on edaphic properties which may eventually influence the growth of co-occurring native species

Mapping the distribution of invasive shrub <em>Austroeupatorium inulifolium</em> (Kunth) R. M. King & H. Rob: a case study from Sri Lanka

A light loving invasive shrub, Austroeupatorium inuli­folium has been spreading many land use types in the Knuckles Forest Reserve (KFR) in Sri Lanka, including man-made grass­lands. In developing countries, there are limitations of using novel technologies to quantify and track the distribution of invasive spe­cies due to high costs and lack of facilities. This is a setback for their early detection and to introduce effective control measures. This pilot study attempted to map the distribution of A. inulifolium in man-made grasslands in KFR using high spatial multispectral images. Unsupervised, supervised and knowledge-based classifi­cations were performed to quantify the spatial distribution of A. inulifolium in ERDAS Imagine. The results generated compara­ble results of the extent of area under A. inulifolium by using the unsupervised (108 ha), supervised (94 ha) and knowledge-based classifications (93 ha). They were 18, 15 and 15% from the to­tal area selected for the study (622 - 646 ha), respectively. The results indicated the suitability of high spatial multispectral imag­eries in quantifying the spatial distribution of A. inulifolium. Fur­ther studies are recommended to investigate long-term changes in invasive plant population using multi temporal satellite data

Functional heterogeneity of metabolites excreted by fungal and bacterial biofilms and their effects on seedling growth

Environmental conditions and physical interactions between microbial cells may alter the metabolites released by them. The present study examined the functional differences of metabolites excreted by three biofilms viz., a fungal biofilm of Aspergillus sp. (FB), a bacterial biofilm of Enterobactor sp. (BB), and their mixed-culture biofilm (FBB). All three biofilms were formed under in vitro conditions and their cell-free exudates were analyzed for functional properties using Fourier Transform Infrared (FTIR) spectroscopy. Further, a germination assay was carried out using lettuce seeds. Functional molecules produced by the FBB have clustered separately from the rest showing the distinctiveness of molecules produced by FBB. All three biofilms showed a higher accumulation of functional molecules during their mature stages than that in the early stages of their development. The lettuce seeds treated with FBB exudates showed a noteworthy growth increment in comparison to FB and BB treated seedlings. The highest seedling vigor was shown by lettuce seeds treated with 0.5 day old FBB exudates, while the least was demonstrated in seeds treated with 6 day old BB, FB and FBB exudates. The results suggest that the accumulation of functional molecules seems to incur phytotoxic effects on lettuce seedlings. In conclusion, 0.5 day old FBB exudates can be used to promote the growth of lettuce seedlings. The study emphasizes the importance of selecting specific biofilms over microbes at species level in developing biofertilizers