Najas Indica Research Articles

Growth performance and enzymatic activities in monosex tilapia (Oreochromis niloticus) supplemented with Najas indica along with the compound identification of the extracts.

Recent research has looked at various macroalgae species as dietary components or feed additives for a variety of fish species due to their nutritional value. The objective of this study was to examine the impact of Najas indica, a macroalgae extract, on the growth performance, proximate composition, and metabolic activities of monosex tilapia (Oreochromis niloticus), while also isolating the compounds present. Three distinct solvents (n-hexane, ethyl acetate, and ethanol) were used to extract bioactive compounds from a coarse powder of macroalgae after drying and grinding, and gas chromatography-mass spectrometry (GC-MS) analysis was used to detect bioactive compounds. The extracts were combined with commercial feed (0.4%) and applied to the treatment with three replications and a control containing 50 fingerlings per tank for 5 weeks. The findings indicated a significant increase in the final weight, weight gain, specific growth rate (SGR), and survival rate among the treated fish, whereas the feed conversion ratio (FCR) was observed to decrease in comparison to the control group. Significantly higher levels of protein and lipids were found in treated fish, whereas moisture and ash levels were significantly lower compared to control fish. In treated fish, the digestive enzyme amylase was significantly higher, but the protease enzyme reduced significantly. The antioxidant enzyme superoxide dismutase activity (SOD) was significantly higher in the treatment group, whereas the catalase (CAT) enzyme did not differ significantly. A total of 47 bioactive compounds were identified in N. indica, among which the prominent compounds included n-hexadecanoic acid, neophytadiene, phytyl palmitate, d-mannitol, and heptanoic acid. The results obtained from this study indicate that the utilization of N. indica macroalgae extract has the potential to serve as an additional dietary component, therefore, enhancing the growth performance and metabolic functions of fish.

Effects of salinity on seedling gemination and growth of early seedlings of the \(\textit{Najas indica}\) (Willd.) Cham.

Najas indica (Willd.) Cham. is a freshwater submerged aquatic vegetation. N. indica is an annual plant. Therefore, seeds in the sediment and the survival and growth of seedlings play an important role in re-establishing new populations of the species. The purpose of this study was to determine the seed density in the sediment, examine the effect of salinity on seedling germination from seeds, and assess the impact of the salinity on the growth of early seedlings of N. indica under the experimental condition. The seed density of N. indica was highest from September to November and the lowest in May to July 2018. Seedlings of the species were observed in the range of salinity from 0–15‰. No seedling was recorded at 20‰ salinity during the experimental period. The number of seedlings, growth rate, shoot length, and the number of internodes of seedlings of N. indica, all had maximum values at a salinity of 5‰, while leaf length tended to decrease with increasing salinity. The study showed that the optimum salinity for seedling germination from seeds and growth of seedlings of N. indica species from the Cau Hai lagoon was at 5‰ salinity. The study results supply the necessary information for the protection and development of meadows of the N. indica species in the lagoon environment of Vietnam.

Response to salinity of the submerged aquatic vegetation species \(\textit{Najas indica}\) (Willd.) Cham.

Najas indica (Willd.) Cham is known as a freshwater species of submerged aquatic vegetation. However, this species is widely distributed in both freshwater and brackish environments. This study examined the survival, growth rate and morphological performance of N. indica collected from the Cau Hai lagoon (Thua Thien Hue) against different salinity treatments in a mesocosm experiment to determine the optimal salinity for the species. The results showed significant effects of different salinities on survival rates, growth, biomass, and the morphological characteristics of N. indica. The species could survive and continue growing at 0–15 ppt but died completely at 20 ppt and 25 ppt after the first week of the 8-week experiment. Leaf length tended to be shorter in higher salinity. Shoot length, the number of internodes and branches per shoot, biomass reached the highest values at 5 ppt and 10 ppt. These suggested that the optimal salinity of the N. indica was at a range of 5–10 ppt. Study results were informative to explain the distribution change of the freshwater originated hydrophyte N. indica in lagoon environments in Vietnam.

Spatial and temporal distribution of submerged aquatic vegetation in a tropical coastal lagoon habitat in Viet Nam

AbstractSubmerged aquatic vegetation (SAV) is considered as a keystone habitat, contributing significantly to structure and function of coastal lagoons. However, limited understanding of the factors driving SAV distribution and abundance across a wide range of salinity in tropical coastal lagoons has restricted the effectiveness of managing and preserving the ecosystem services in coastal lagoon habitats. This study examined the distribution and abundance of SAV species in the growing season in relation to water physico-chemical variables and grain sizes of sediment types in a tropical lagoon in Viet Nam. The results revealed thatNajas indicaandHalophila beccariiwere the dominant species in the community of 7 SAV species, accounting for 70% of the total cover and 55% of the total biomass sampled. Variation partitioning showed that both water and sediment variables were important in explaining spatial distribution and abundance of SAV species across the coastal lagoon. Salinity was the most significant predictor variable that accounted for the variation of SAV species data. The study implied that changes of salinity and silt (versus sand) particles can lead to different SAV assemblages in the lagoon.

Arsenic accumulation and tolerance in rootless macrophyte Najas indica are mediated through antioxidants, amino acids and phytochelatins

Arsenic (As) accumulation and tolerance response of a submerged rootless macrophyte Najas indica were evaluated during arsenate (AsV; 10–250μM) and arsenite (AsIII; 1–50μM) exposure. Higher As accumulation at AsIII exposure and more tolerance upon AsV exposure resulted in more toxicity during AsIII stress than AsV, which was evident through measurement of growth parameters and oxidative stress related parameters viz., lipid peroxidation (MDA content), electrical conductivity (EC) and hydrogen peroxide (H2O2) levels. Antioxidant enzymes and various amino acids were more prominent during moderate exposure of AsV, suggesting their possible role in As tolerance and detoxification. Various non-enzymatic antioxidant metabolites viz., ascorbic acid (ASC), glutathione (GSH), non-protein thiols (NPTs) and phytochelatins (PCs) biosynthesis involving phytochelatin synthase (PCS) activity increased more significantly during AsIII stress. However, PCs content seems inadequate in response to As accumulation leading to lower PC-SH:As molar ratio and higher As phytotoxicity during AsIII stress. N. indica may prove useful plant species for phytoremediation purpose in moderately As contaminated water bodies due to high As accumulation and tolerance potential.

Environmental Reservoirs for Enterotoxigenic Escherichia coli in South Asian Gangetic Riverine System

Forecasting diarrheagenic E. coli contamination of aquatic resources to prevent outbreaks largely depends on rapid and accurate diagnostic testing in a few hours. Real-time PCR is widely used for quick culture-free quantitative enumeration of pathogenic bacteria in environmental samples. In this study, real-time PCR in molecular beacon format was used for detection and culture-free quantitative enumeration of enterotoxigenic Escherichia coli (ETEC) harboring LT1 gene in a sewage-impacted south Asian Gangetic riverine system. The quantitative budget for ETEC in surface water was observed to vary significantly (DMRT, p < 0.05) among the sites. Aquatic flora (Eichhornia crassipes, Potamogeton crispus, Potamogeton pectinatus, Ranunculus sceleratus, Polygonum glabrum, Pontederia cordata, Najas indica and strands of Spirogyra spp.) collected between sites 1 and 9 exhibited significant high levels of ETEC in comparison to their representatives collected from pristine area. The level of ETEC harboring LT1 gene observed in leafy vegetables cultivated along the banks was in the following order: mint leaves > coriander > spinach > methi leaves. The study suggests that the aquatic flora and cultivated leafy vegetables in the south Asian Gangetic riverine system are environmental reservoirs for enterotoxigenic Escherichia coli.

Lead bioaccumulation potential of an aquatic macrophyte Najas indica are related to antioxidant system

Plants of Najas indica bioaccumulated significantly higher amounts of Pb (3554 μg g −1 dw) when, exposed to varying concentrations of Pb(NO 3) 2.This also led to increased malondialdehyde (MDA), electrical conductivity (EC) and H 2O 2 content. In response to this, the activities of antioxidant enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), catalase (CAT) and glutathione reductase (GR) were elevated along with the induction of various molecular antioxidants including GSH, cysteine, ascorbic acid and proline. Further, Pb exposed plants showed significantly increased cysteine synthase and glutathione- S-transferase activity. Visible symptoms of toxicity were evident at 50 μM after 4d showing chlorosis and fragmentation of leaves with mucilaginous discharge. It seems that bioaccumulated Pb is efficiently tolerated by Najas plants through activation of antioxidant system and thiolic pathways which was evident by the increased biomass up to 10 μM Pb. Therefore, it appears that due to metal tolerance characteristics with high concentration factor these plants can find use in phytoremediation of aquatic system highly contaminated by Pb.

Fertilization Capacity of Aquatic Plants Used as Soil Amendments in the Coastal Sandy Area of Central Vietnam

In Central Vietnam, and more especially in Thua Thien Hue Province, aquatic plants are used empirically by some farmers as an external source of organic matter to improve fertility of sandy soils. The fertilization capacities of aquatic plant species [Najas indica (Willid.) Cham., Najas minor All., Vallisneria spiralis L. (Michx.) Torr., Hydrilla verticillata (L.f.) Royle, Potamogetum malaianus Miq., Myriophyllum spicatum L., Enteromorpha flexuosa (Wulfen) J. Agardh, Rhizoclonium kerneri Stockmayer, and Eichhornia crassipes (Mart) Solms] were assessed from a pot trial including soils amended with aquatic plants (5 g dry matter kg−1 soil) and soils supplied with increasing rates of urea nitrogen (N) fertilizers. Rice (Oryza sativa L.) at a vegetative stage was used as a convenient bio‐extractor. The fertilization capacity of aquatic plant amendments was calculated from aboveground biomass and from N accumulated in shoots as compared to treatments receiving only inorganic N fertilizers. Najas indica (Willid.) Cham. and Hydrilla verticillata (L.f.) Royle showed the greatest fertilization capacity, equivalent to 170–180 mg urea‐N kg−1 soil as estimated from biomass yield, whereas a lesser fertilization capacity, equivalent to less than 100 mg urea‐N kg−1 soil, was observed for Myriophyllum spicatum L., Enteromorpha flexuosa (Wulfen) J. Agardh, Rhizoclonium kerneri Stockmayer, and Eichhornia crassipes (Mart) Solms. This study provides quantitative data on the fertilization capacity of aquatic plants found in the coastal area of central Vietnam, which can improve this empirical practice and alleviate local agro‐environmental constraints related to the lack of organic matter in farming systems.

Salinity induced changes in proline and betaine contents and synthesis in two aquatic macrophytes differing in salt tolerance

The present work investigated the effect of NaCl and seawater salinity (SWS) on accumulation of proline and glycinebetaine (betaine) and expression of two key enzymes of their biosynthetic pathway, betainealdehyde dehydrogenase (BADH) and &Delta;1-pyrroline-5-carboxylate synthetase (P5CS) in two aquatic macrophytes, salt-tolerant Najas gramenia and moderately-salt-tolerant Najas indica. N. gramenia did not show any accumulation of betaine or expression of BADH in response to NaCl or SWS treatments. The content of proline increased significantly in response to the salt treatments. High expression of P5CS was also observed, however, the transcript abundance did not correlate with the amount of proline. N. indica, exhibited significantly greater accumulation of proline in response to SWS, which contained Ca2+ in addition to NaCl, than in response to NaCl alone.

Interactive metal accumulation and its toxic effects under repeated exposure in submerged plant Najas indica Cham.

Interactive metal accumulation and its toxic effects under repeated exposure in submerged plant Najas indica Cham.

Comparative studies on accumulation of Cr from metal solution and tannery effluent under repeated metal exposure by aquatic plants: its toxic effects.

The present study demonstrates comparison of Cr accumulating potential by the plants of Najas indica Cham. (submerged), Vallisneria spiralis L. (rooted submerged) and Alternanthera sessilis R. Br. (rooted emergent) under repeated metal exposure and its effect on chlorophyll and protein concentrations. These plants were treated with different concentrations of Cr under repeated exposure in controlled laboratory conditions to assess the maximum metal accumulation potential. The plants of V. spiralis accumulated significantly high amount of Cr under laboratory conditions in comparison to N. indica and A. sessilis. The maximum accumulation of 1378, 458 and 201 microg (-1) dw Cr was found in the leaves of V. spiralis. N. indica and A. sessilis, respectively at 8 mg (-1) after 9 day of Cr exposure. These plants have shown a decrease in chlorophyll and protein concentrations with increase in Cr concentrations. In view of high accumulation of Cr in V. spiralis, the plants were treated with different concentrations of tannery effluent collected from Common Effluent Treatment Plant, Unnao (UP). The plants of V. spiralis treated with 100% tannery wastewater showed the maximum accumulation (57.5 microg g(-1) dw) of Cr in the roots after 10 days of exposure. The plants were found effective in removing Cr from solution and tannery effluent.

Salt Tolerance in Aquatic Macrophytes: Ionic Relation and Interaction

Effects of seawater salinity (SWS) and pure NaCl on the intracellular contents of Na+, K+, Mg2+, Ca2+, chlorophylls (Chl) and carotenoids (Car) were studied in three submerged aquatic macrophytes, Hydrilla verticillata, Najas indica and Najas gramenia, which differed in their tolerance to salinity. NaCl resulted in significant increase in Chl/Car ratio in the salt-sensitive H. verticillata and moderately salt-tolerant N. indica, but not in the salt-tolerant N. gramenia. SWS treatment did not result in any significant change in the ratio. The intracellular content of Na+ increased significantly in all the test plants upon exposure to both NaCl and SWS. The content of K+ decreased significantly in these plants upon salinity treatment, except in N. gramenia. The contents of Ca2+ and Mg2+ decreased significantly upon NaCl treatment and remained unchanged or increased upon SWS treatment. No relationship between salt tolerance and K+/Na+ ratio was observed. The maintenance of a minimal level of K+ was observed to be the most probable requirement of salt tolerance in aquatic macrophytes.

Salt tolerance in aquatic macrophytes: possible involvement of the antioxidative enzymes

Possible involvement of the antioxidative enzymes in salt tolerance was investigated in three submerged aquatic macrophytes, viz. Hydrilla verticillata, Najas indica and Najas gramenia, which differed in their tolerance to salinity. NaCl in light resulted in significant decrease in the chlorophyll a/ b ratio in H. verticillata, which was significantly neutralized by the presence of DABCO (diazabicyclo[2.2.2]octane), sodium benzoate or mannitol along with the NaCl in the exposure medium indicating induction of oxidative stress upon salt treatment. All the three test species showed enhanced activity of superoxide dismutase (SOD; EC 1.15.1.1) and peroxidases (EC 1.11.1.7) upon exposure to either NaCl or SWS (seawater salinity); the increases in their activity in response to NaCl were positively correlated with the salt tolerance of the plants. Only N. gramenia showed considerable increase in the activity of catalase (EC 1.11.1.6), while only H. verticillata exhibited significant increase in the activity of ascorbate peroxidase (EC 1.11.1.11) in response to the salt treatment. A higher constitutive level of the antioxidative enzymes in the salt-tolerant N. gramenia than in the salt-sensitive H. verticillata coupled with significant increase in the activity of these enzymes, particularly of catalase and SOD, in the former upon salinity treatment suggested their active involvement in salt tolerance. The oxidative stress induced upon the salt treatment also indicated a possible involvement of the antioxidative enzymes in the process. The ion interaction study revealed significant modifying effect of Ca 2+, and also of Mg 2+ and K +, on the changes induced by Na + in the activity of catalase and SOD suggesting that relative build-up of these ions inside cells could be of much importance in regulation of synthesis of antioxidative enzymes.

Salinity tolerance in aquatic macrophytes: probable role of proline, the enzymes involved in its synthesis and C 4 type of metabolism

Effects of NaCl and sea-water salinity (SWS) on proline accumulation and activities of Δ 1-pyrroline-5-carboxylate reductase (P5CR), Δ 1-pyrroline-5-carboxylate synthetase (P5CS) and phospho enolpyruvate carboxylase (PEPC) in three aquatic macrophytes Hydrilla verticillata, Najas indica and N. gramenia, which differed in salinity tolerance, were studied in order to understand their possible role in providing resistance to salinity. All the three species showed enhancement in the contents of proline in response to the salinity treatments. The accumulation was more in response to SWS than in response to NaCl alone, probably because of the presence of Ca 2+ in SWS. The activity of P5CR was found to be increased in response to both NaCl and SWS treatments, more in the salt-tolerant N. gramenia than in the salt-sensitive H. verticillata. The proline content, however, did not increase in proportion to the increase in the activity of the enzyme. Unlike P5CR, the activity of P5CS, studied as γ-glutamyl kinase ( γ-GK, a constituent of P5CS), did not increase either in response to NaCl or SWS, but the salt-tolerant N. gramenia had much greater background (control level) activity of the enzyme than the salt-sensitive H. verticillata. The activity of PEPC was also much greater in N. gramenia, as well as in the moderately salt-tolerant N. indica, when compared to that in H. verticillata. Only H. verticillata showed an increase in the activity of the enzyme in response to the salinity treatments. The study indicated that the accumulation of proline in aquatic plants is most likely a consequence of ionic adjustments in which Ca 2+ plays an important role, and also that the P5CS may not be a rate limiting factor of proline biosynthesis in these plants in contrast to the reports available for terrestrial plants. The study further indicated that greater the P5CS activity, more the aquatic plants are tolerant to salinity, and that C 4 type of carbon metabolism may have some contribution to the salinity tolerance in these plants.

Ecology of deepwater rice-fields in Bangladesh 3. Associated algae and macrophytes

(i) Aquatic macrophytes formed dense beds in fallow areas during the four and a half months of the flood season in all but one deepwater rice-growing location in Bangladesh; these included several types of life-form, but the fine-leaved species, Myriophyllum sp., Najas indica, Utricularia stellaris were often especially abundant. The same species grew inside deepwater rice fields, but at much lower densities. A similar contrast occurred for the algae, although deepwater rice often developed dense masses of epiphytes on aquatic roots, stems and leaf sheaths, when plants were growing in isolated, well-illuminated situations. (ii) Two widespread algae, Aulosira fertilissima and Scytonema mirabile, were equally successful on soil in the period prior to the arrival of floodwaters and floating on the surface of the water during the flood season. Other species common during the flood season differed from those common on soil. (iii) Most blue-green algae inside deepwater rice fields were heterocystous; the only species not so, but forming distinct colonies, was Aphanothece stagnina. However only non-heterocystous forms were found at one location in south Bangladesh (Phaltita) and a change from heterocystous to non-heterocystous forms was noted at the main research site (near Sonargaon) during late September in at least one year. The water column at the former was almost entirely anoxic, while the change at the latter occurred at a time when the water sometimes became anoxic during the night. It is suggested that differences in ability to tolerate anoxic periods may be a key factor in determining the success of the algal and vascular plant species in the different micro-habitats within these DWR-growing areas. (iv) Although diatoms were quantitatively only a minor component of the algal biomass, they became more frequent later in the season when the water became microaerobic or anoxic for part of the day. Navicula confervacea was overall the most abundant species at the two main research locations.

Ecology of deepwater rice-fields in Bangladesh 4. Nitrogen fixation by blue-green algal communities

(i) Aquatic macrophytes formed dense beds in fallow areas during the four and a half months of the flood season in all but one deepwater rice-growing location in Bangladesh; these included several types of life-form, but the fine-leaved species, Myriophyllum sp., Najas indica, Utricularia stellaris were often especially abundant. The same species grew inside deepwater rice fields, but at much lower densities. A similar contrast occurred for the algae, although deepwater rice often developed dense masses of epiphytes on aquatic roots, stems and leaf sheaths, when plants were growing in isolated, well-illuminated situations. (ii) Two widespread algae, Aulosira fertilissima and Scytonema mirabile, were equally successful on soil in the period prior to the arrival of floodwaters and floating on the surface of the water during the flood season. Other species common during the flood season differed from those common on soil. (iii) Most blue-green algae inside deepwater rice fields were heterocystous; the only species not so, but forming distinct colonies, was Aphanothece stagnina. However only non-heterocystous forms were found at one location in south Bangladesh (Phaltita) and a change from heterocystous to non-heterocystous forms was noted at the main research site (near Sonargaon) during late September in at least one year. The water column at the former was almost entirely anoxic, while the change at the latter occurred at a time when the water sometimes became anoxic during the night. It is suggested that differences in ability to tolerate anoxic periods may be a key factor in determining the success of the algal and vascular plant species in the different micro-habitats within these DWR-growing areas. (iv) Although diatoms were quantitatively only a minor component of the algal biomass, they became more frequent later in the season when the water became microaerobic or anoxic for part of the day. Navicula confervacea was overall the most abundant species at the two main research locations.