Plant and Molecular Biology
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Item Species identification and pollination biology of an economically important true halophyte, Salicornia brachiata Roxb.(Aquatic Botany, 2024) Siridewa, K.; De Silva, W.; Ratnayake, R.; Wijesundara, S.; Perera, D.; Attanayake, R. N.Members of the genus Salicornia have gained a global attraction due to their ability to thrive under high saline conditions and as potential candidates in saline agriculture. However, it has been a taxonomically challenging genus for decades since the members show plastic responses to extreme environmental conditions and due to incongruences between morphological and molecular identification methods. While only a handful of commercially grown Salicornia species are fully described, most of the species including S. brachiata, a native species in the Indian sub-continent, Myanmar, and Sri Lanka are poorly described. With the potentials in adapting S. brachiata in saline agriculture, the aim of this study was to establish a morphology and DNA barcodebased species delineation system and to study pollination biology for future crop improvement projects. Tentatively identified S. brachiata plant samples were collected from two populations in Sri Lanka and completely described. GenBank lacked authenticated barcode data for S. brachiata except for one chloroplast genome to which the matK sequence obtained in the present study matched with 100 % identity. For the first time, well defined sequences of three barcode regions, ITS, ETS and matK, of S. brachiata were made available for accurate species identification. Reproductive dynamics in different parts of the inflorescence was studied. A facultative xenogamous mating system was recorded for the first time in the genus and while the lower florets in the cladode showed a preference towards outcrossing, the upper florets displayed adaptations for selfing. Data could be effectively utilized in future Salicornia breeding programs.Item Spatial distribution and dynamics of selected mangrove forests on the east and west coasts of Sri Lanka(Sri Lanka Journal of Aquatic Sciences, 2022) De Silva, W.; Perera, K.A.R.S.; Amarasinghe, M. D.The climate and edaphic characteristics primarily determine the spatial distribution and dynamics of mangrove forests. The present study was initiated to determine how species composition and structural characteristics vary along with climate and substrate salinity of six mangrove forests located on the west coast, i.e., Negombo estuary, Chilaw lagoon, and Malwathu oya estuary, and east coast, i.e., Batticaloa lagoon, Uppar lagoon, and Urani lagoon. The structural parameters in terms of tree height, basal area, biomass, and density were obtained to determine the vegetation structure of mangrove forests. The current study found that although the structure of mangrove communities of the two coasts does not differ significantly (P<0.05), plant diversity in mangrove areas on the west coast is significantly higher than that of the east coast mangroves. In contrast, the biomass accumulation in west coast mangroves is relatively lower than that of east coast. Tree height was found to influence the productivity in terms of biomass increment of mangrove forests under investigation. As such, our study suggests that regional variations in salinity, temperature, and rainfall primarily serve as drivers of variation in mangrove species composition and vegetation structure of mangrove forests along the coasts of Sri Lanka.Item Phylogenetic Revision of Savoryellaceae and Evidence for Its Ranking as a Subclass(Front. Cell. Infect. Microbiology, 2019) Dayarathne, M.C.; Maharachchikumbura, S.S.N.; Jones, E.B.G.; Dong, W.; Devadatha, B.; Yang, J.; Ekanayaka, A.H.; De Silva, W.; Sarma, VV.; Al-Sadi, A.M.; Khongphinitbunjong, K; Hyde, K.D.; Zhao, R.L.Morphology, phylogeny, and molecular clock analyses were carried out on Savoryellaceae in order to understand the placements of taxa in this family. Ascotaiwania and Neoascotaiwania formed a well-supported separate clade in the phylogeny of concatenated partial SSU, LSU, TEF, and RPB2 gene data. These two genera share similar morphological features, especially in their asexual morphs, indicating that they are congeneric. Hence, we synonymize Neoascotaiwania under Ascotaiwania. Ascotaiwania hughesii (and its asexual morph, Helicoon farinosum) and Monotosporella setosa grouped in a clade sister to Pleurotheciales and are excluded from Ascotaiwania which becomes monophyletic. A novel genus Helicoascotaiwania is introduced to accommodate Ascotaiwania hughesii and its asexual morph, Helicoon farinosum. A novel species, Savoryella yunnanensis is introduced from a freshwater habitat in Yunnan Province, China. Comprehensive descriptions and illustrations are provided for selected taxa in this family. In addition, we provide evolutionary divergence estimates for Savoryellomycetidae taxa and major marine based taxa to support our phylogenetic and morphological investigations. The taxonomic placement of these marine-based taxa is briefly discussed. Our results indicate that the most basal group of marine-based taxa are represented within Lulworthiales, which diverged from ancestral Sordariomycetes around 149 Mya (91–209) and Savoryellomycetidae around 213 Mya (198–303).Item Root-foraging behavior ensures the integrated growth of Vallisneria natans in heterogeneous sediments(Environmental Science and Pollution Research, 2017) Chen, J.; Hu, X.; Cao, T.; Zhang, X.; Xi, Y.; Wen, X.; Su, H.; De Silva, W.; Zhu, T.; Ni, L.; Xie, P.Abstract The present study was carried out to determine the efficacy of root foraging and the physiological response of Vallisnaria natans grown in heterogeneous sediments. V. natans was cultivated in two homogeneous and two heterogeneous sediments. The results suggested that V. natans grown in heterogeneous sediments presented a significantly higher root proportion in its total biomass, exhibited root foraging, and grew well, as indicated by a total biomass, ramet number, and plant height very close to those of plants grown in nutrient-rich clay sediment. Moreover, the more sensitive physiological response of the roots than the stems or the leaves to sediment nutrients suggested that root foraging occurred, and the approached values between the two heterogeneous sediments and the homogeneous clay sediment indicated that V. natans could satisfy its nutrient requirements via root foraging. The results may be useful in the recovery of macrophytes that remodel part (rather than all) of the substrate and can potentially improve habitats that are unsuitable for plant growth.Item Potential spreading risk of an invasive snail species (Pomacea canaliculata) in freshwater habitats of Asia(Current Science, 2019) De Silva, W.; Cao, T.; Wen, Z.; Zhang, X.; Ni, L.The invasive success of the freshwater snail species (Pomacea canaliculata) continues to wreak havoc around the world. The present study was initiated to analyse spatial trend and associated environmental conditions related to the invasive success of P. canaliculata in Asia. Systematic searches were performed to identify relevant studies through different databases, and appropriate statistical methods like spatial autocorrelation, standard deviational ellipse method and PCA were used to generate new knowledge on this species. The potential invasive range of this species is between 40°N and 40°S lat. The present study reveals that the spatial distribution of P. canaliculata is most significantly correlated with human population density, followed by humidity, temperature and precipitation. Moreover, the grazing rates are dramatically affected by nutrient content of freshwater macrophytes. Spatial autocorrelation analysis result indicates clustered dispersion pattern of this snail, and standard deviational ellipse depicts the invasion trend of P. canaliculata moving from East Asia to potential areas in South and West Asia. We therefore conclude that P. canaliculata is likely to be the ‘next harmful visitor’ to South and West Asian countries.Item Response of mangrove plant species to a saline gradient: Implications for ecological restoration(Acta Botanica Brasilica, 2021) De Silva, W.; Amarasinghe, M.Mangroves are salt tolerant plants that occur in tropical and sub-tropical sheltered coasts. Saltwater intrusions into terrestrial landscapes often occur due to either anthropogenic reasons or natural calamities such as tsunamis. We investigated the potential of using mangrove species for rehabilitation of high saline environments by revealing the capacities of species to remove salt from sediment. We established the salt retention capacity of common mangrove species in Sri Lanka i.e., Rhizophora apiculata, Rhizophora mucronata, Ceriops tagal, and Avicennia marina through exsitu and in-situ measurements of NaCl content in plant tissue and soil samples, by titrating with 0.01 N AgNO3. The results revealed A. marina to be the most efficient in retaining salt within plant tissues while C. tagal is superior to R. mucronata but inferior to A. marina in performing this function. These findings were further confirmed by measuring salt uptake rates of hydroponically grown seedlings of the same species. Although R. mucronata is the most popular species used for restoration, A. marina appears the most suitable mangrove species not only for coastal mangrove restoration but also for rehabilitating salinity affected landscapes.Item Potential Use of Mangroves for Coastal Protection: A Case Study from Sri Lanka(Journal of the Indian Society of Coastal Agricultural Research, 2021) Amarasingha, M.D.; De Silva, W.Mainstreaming coastal biodiversity certainly brings nature-based solutions for the conservation of offshore and onshore resources. Being an island, the long-term shoreline change of Sri Lanka is particularly important for management of the island’s coastal resources. This study was carried out at the southwestern and southern coasts of Sri Lanka to investigate the protective capacity of mangroves against coastal erosion, and coastal inundation hazards due to the climate associated sea-level rise. Structural diversity of mangrove stands was assessed in terms of alpha-diversity, plant species richness, basal area, tree height, density, and structural complexity index. Analysis of aerial photographs and the ASTER Global Digital Elevation Model was used to identify shoreline changes along the southwestern and the southern coasts of Sri Lanka. Results revealed that by and large, the southwestern coast is highly vulnerable to coastal erosion and inundation hazards whereas the southern coast manifests a tendency to retreat. The average annual rate of shoreline change however varies within the two coastal areas, as there were accreting as well as eroding segments on both southern and southwestern coasts, nevertheless, all retreating beach segments were the sites of improper maritime developments. Segments with lower rates of shoreline erosion and coastal inundation hazards were found to be located close to the mangrove and other coastal vegetation with varying structural complexity and diversity. Reforestation and restoration of vegetation in coastal lagoons and estuarine habitats are evidently effective strategies not only to protect the low-lying coastal hinterlands but also to preserve coastal biodiversity.