Halophytophthora fluviatilis Pathogenicity and Distribution along a Mediterranean-Subalpine Gradient

Halophytophthora species have been traditionally regarded as brackish water oomycetes; however, recent reports in inland freshwater call for a better understanding of their ecology and possible pathogenicity. We studied the distribution of Halophytophthora fluviatilis in 117 forest streams by metabarcoding river filtrates taken in spring and autumn and by direct isolation from floating leaves. Pathogenicity on six Fagaceae species and Alnus glutinosa was assessed by stem inoculations. The distribution of H. fluviatilis was correlated with high mean annual temperatures (>93.5% of reports in Ta > 12.2 °C) and low precipitation records. H. fluviatilis was therefore widely distributed in forest streams in a warm–dry climate, but it was mostly absent in subalpine streams. H. fluviatilis was primarily detected in autumn with few findings in spring (28.4% vs. 2.7% of streams). H. fluviatilis was able to cause small lesions on some tree species such as Quercus pubescens, Q. suber and A. glutinosa. Our findings suggest that H. fluviatilis may be adapted to warm and dry conditions, and that it does not pose a significant threat to the most common Mediterranean broadleaved trees.

Variations in the Phytoremediation Efficiency of Metal-polluted Water with Salvinia biloba: Prospects and Toxicological Impacts

The occurrence of heavy metals in industrial wastewater is unanimously considered a major concern since these pollutants cannot be chemically or biologically degraded and therefore have long residence times. Phytoremediation is one of the most widespread biotechnological applications worldwide, which consists in the use of plants to adsorb or accumulate a broad range of inorganic and organic contaminants from water, air, and soil. To improve the cost-effectiveness and sustainability of phytoremediation-based wastewater treatment systems, it is essential to use plants that are not only efficient in pollutants removal, but also abundant and easily accessible at the target site, requiring no-special culture conditions. In this study, we have evaluated the capacity of naturally-occurring aquatic macrophytes of the genus Salvinia (classified as Salvinia biloba) to phytoremediate water artificially contaminated with cadmium (Cd), copper (Cu), lead (Pb), or zinc (Zn) at equal molar concentrations (50 ± 2 and 100 ± 1 µM), during 48 h. Additionally, photosynthetic and antioxidant pigments (carotenoids, chlorophylls, anthocyanins, and flavonoids), and soluble carbohydrate content was also measured in floating leaves of Salvinia specimens to appraise heavy metals phytotoxicity. Elemental analyses to plant tissue indicate that S. biloba was able to bioconcentrate all four metals analyzed, albeit with different degrees of affinity. In addition, the mechanisms of uptake and detoxification were dissimilar for each ion, resulting in greater removal of Cu and Pb (≥96%, at both concentrations), in comparison to Cd (79 ± 4% and 56 ± 2% for 50 ± 2 and 100 ± 1 µM, respectively) and Zn (77 ± 5% and 70 ± 4% for 50 ± 2 and 100 ± 1 µM, respectively). Accordingly, the assessment of the selected physiological parameters in floating leaves suggests that different response mechanisms are triggered by each metal in S. biloba to counteract the corresponding toxicological stress.

Comparative morphology and phenetics of Nymphoides species in Kerala

Aquatic plants play an important role in maintaining the ecosystem balance. Nymphoides Seguier (Menyanthaceae) is an emergent, rhizomatous or stoloniferous genus, commonly known as “floating hearts”, identified by its rounded or cordate, floating leaves, petiole like branches and unique floral characters. The present study deals with the comparative morphology and the phenetics of Nymphoides spp. in Kerala. These species are classified into two groups with the help of the dendrogram, which showed 66% dissimilarities among the two groups. N. parvifolia and N. balakrishnanii are closely related species in one group and N. krishnakesara and N. macrosperma are closely related species in other group.

Spatial variations of trace elements contents in macrophytes within Belarusian lakes

The spatial variation of trace elements contents of heavy metals (Ti, V, Cr, Mn, Ni, Cu, Pb) in higher aquatic plants of Belarusian lakes has been analyzed according to monitoring data. Natural variability limits of metals contents in aquatic plants of lakes within principal rivers basins of Belarus have been determined. The data on trace elements contents in macrophytes of Belarus are comparable with the data obtained in Poland and other neighbouring countries. Aquatic plants in lakes are characterized by selective metals accumulation, which is different for ecological groups of submersed, emergent and macrophytes with floating leaves. Statistically significant differences between river basins in the contents of Mn, Cu and Pb have been established in the submersed macrophytes. For all ecological groups, the highest concentrations of Mn in lakes macrophytes tissues are observed in the basins of the Dniapro, Prypiać, Zachodni Buh, and the lowest – the Biarezina. The lakes of the Zachodni Buh and Dniapro basins are distinguished by lower Pb concentrations in aquatic plants. Significant differences in the content of Mn and Cu in the plant tissues within different trophicity lakes have been established. The lowest concentrations of Mn are observed in mesotrophic lakes with signs of oligotrophy. Group analysis of lakes based on the content of Mn, Cu, Pb in macrophyte tissues and spatial constraints has been performed. Among the allocated groups are the lakes of the Braslav district characterized by elevated content of Mn and Cu; lakes of the Vilija basin, distinguished by the lowest average levels of Cu and Pb; lakes of the northern part of Belarus, notable for increased contents of Cu and Pb.

Initial decomposition of floating leaf blades of waterlilies: causes, damage types and impacts

The initial decomposition of large floating-leaved macrophytes, such as waterlilies, can be studied by following changes in leaf damage and area loss of leaf blades tagged in their natural environment. This approach was taken in the present study to examine the initial decomposition patterns of floating leaf blades of Nuphar lutea (L.) Sm., Nymphaea alba L. and Nymphaea candida C. Presl at three freshwater sites differing in nutrient status, alkalinity and pH. Floating leaf blades of the three plant species were tagged and numbered within established replicate plots and the leaf length, percentages and types of damage and decay of all tagged leaves were recorded weekly during the growing season. Microbial decay, infection by phytopathogenic fungi (Colletotrichum nymphaeae) and oomycetes (Pythium sp.), consumption by pond snails, and mechanical factors were the most important causes of leaf damage. Several types of succession comprising different causes of damage were distinguished during the season. For example, young floating leaves are affected by more or less specialized invertebrate species consuming leaf tissue, followed by non-specialized invertebrate species feeding on the damaged floating leaves. In the two investigated hardwater lakes the seasonal patterns of initial decomposition differed between Nymphaea and Nuphar.

A new species of Potamogeton (Potamogetonaceae) from the unique habitat: Montezuma Well, Arizona, U.S.A.

Montezuma Well is a geothermal limnocrene spring within Montezuma Castle National Monument, Yavapai County, Arizona, U.S.A. The Well’s unusual geological qualities, water chemistry, and a history of aquatic plant collecting are discussed. Evidence to support the fact that a unique species of Potamogeton has likely grown in this location for thousands of years and is now recognized as the seventh apparent autochthonous endemic species from this small area is presented. Although this new species shares a few superficial characters with P. illinoensis Morong, it is easily distinguished by its massive height (7–8 m tall), lack of floating leaves, long acuminate leaf apices of its submerged leaves, and bright translucent green leaf color. A complete description with drawing and photographs is provided.

Morphometrics and taxonomic update to the Sri Lankan Aponogetonaceae

The recent studies on Sri Lankan Aponogeton underline the necessity of a taxonomic revision for the genus; especially with the recent discovery of two new endemic taxa and their described morphological affinities, revealing some misconceptions in the key morphological features used in identification and the overlapping morphology of the species within the genus. Accordingly, a morphometric analysis was carried out with 78 field collected specimens representing all six Sri Lankan Aponogeton species. The results indicate that A. kannangarae, a recently described endemic species which has been stated as closely resembling A. rigidifolius, is more similar to A. jacobsenii, with shared morphological characters, raising doubts if it is a distinct species. Further, the endemic A. jacobsenii, previously described and illustrated as a species with rarely occurring floating leaves, has been now described as with no floating leaves. Based on the results, a taxonomic update is presented with a key, full synonymy, descriptions and photographs.

Breeding behaviour of the Coromandel Marsh Dart Damselfly (Zygoptera: Coenagrionidae: Ceriagrion coromandelianum (Fabricius)) in central India

Ceriagrion coromandelianum (Fabricius) is one of the most common damselflies in the Indian subcontinent. It flies among bushes and breeds in stagnant pools, small garden tanks, tubs and ornamental cement ponds containing submerged and/or floating vegetation. The oviposition behaviour of C. coromandelianum was observed at the botanical garden of Hislop College, Nagpur, India, where small underground cement tubs are utilized to grow macrophytes. C. coromandelianum displays a refined hierarchy of preferences for oviposition and chooses floating leaves of Nymphaea nouchali (69%) over Lemna paucicostata (23%) and submerged Hydrilla verticillata (8%). In an uninterrupted oviposition bout, the female deposits 283 eggs in 16 rows (N=5) on the under surface of the N. nouchali leaf. The tiny leaves of L. paucicostata holds 7.8 eggs in 4.8 rows (N=10). In H. verticillata, the internode region of the stem can house 25.4 eggs (N=10). One or two eggs are also found neatly inserted in the thin leaf base of H. verticillata. Decaying plant material is never used for oviposition. The present investigation also clearly demonstrates that the choice of oviposition substrate not only depends upon the presence of aquatic species in the water body but also on the spatial location of the oviposition site.