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Altica cyanea (Weber, 1801) (Coleoptera: Chrysomelidae) is a biocontrol agent of Onagraceae rice-field weeds, Ludwigia adscendens (L.) Hara, L. parviflora Roxb. and L. octovalvis (Jacq.) Raven in India. Hence, it is relevant to study the life history traits and population growth of A. cyanea on three Ludwigia species using age-stage, two-sex life table. The nutritional and antinutritional contents from leaves of the Ludwigia species were measured to comment on the role of nutrients and antinutrients on growth, development and fecundity of A. cyanea. Total larval developmental time was the shortest on L. adscendens (17.78 ± 0.22 days), intermediate on L. parviflora (20.35 ± 0.24 days) and the longest on L. octovalvis (21.98 ± 0.24 days). Total fecundity was the highest on L. adscendens (147.22 ± 4.74 eggs/female) followed by L. parviflora (119.28 ± 4.70 eggs/female) and the lowest on L. octovalvis (89.62 ± 3.45 eggs/female). The intrinsic rate of increase (r) ranged from 0.0639 to 0.0875 d− 1, which was the lowest on L. octovalvis and the highest on L. adscendens. Population projection indicates that the population growth would be the fastest on L. adscendens and the slowest on L. octovalvis. The nutrients (lipids, amino acids and nitrogen) and antinutrients (tannins) were higher and lower, respectively, in L. adscendens than the other two Ludwigia species, which influenced faster larval development, higher adult longevity and greater fecundity of A. cyanea on L. adscendens. This study suggested that mass release of A. cyanea could be applied in biocontol program of these three Ludwigia weeds.

Objectives Altica cyanea (Weber) (Coleoptera: Chrysomelidae) is a potential biocontrol agent of rice-field weeds, Ludwigia adscendens (L.) Hara, L. parviflora Roxb., and L. octovalvis (Jacq.) Raven (Onagraceae) in India. Damage on leaf tissue causes stress on plants. Hence, this study aims to observe how the three Ludwigia species are trying to cope with the stress caused by feeding of A. cyanea adults at different time intervals. Materials Uninfested L. adscendens, L. parviflora, and L. octovalvis, and each Ludwigia species on which 5 adult A. cyanea females had fed on continuously for 6 h or 48 h were used for collection of leaf tissues. The amounts of total ROS, H2O2, activity of enzymatic antioxidants [superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), activity of peroxidases towards phenolic substances {guaiacol peroxidase (GPX) and pyrogallol peroxidase (PPX)}, and ascorbate peroxidase (APOX)] and non-enzymatic antioxidants (phenolics and thiols) were estimated from leaf tissues of undamaged and insect damaged Ludwigia species using standard protocols. Results The amounts of total ROS and H2O2 were higher in each Ludwigia species after 48 h feeding by A. cyanea followed by plants after 6 h feeding by A. cyanea and undamaged plants. The activities of antioxidant enzymes such as CAT, SOD, GST, APOX, PPX, and GPX were higher in each Ludwigia species after 48 h feeding by A. cyanea compared to undamaged plants. Total proteins and thiols were higher in each undamaged Ludwigia species compared to insect damaged plants; whereas total phenols were higher in each insect damaged Ludwigia species compared to undamaged plants. Conclusions Higher amounts of total ROS and H2O2 in each insect damaged Ludwigia species compared to undamaged plants suggested that A. cyanea feeding resulted stress in the insect damaged plants. Higher amounts of CAT, SOD, GST, and APOX in insect damaged Ludwigia species compared to undamaged plants suggested that these four enzymes were acting as antioxidants to reduce the stress created in plants due to insect herbivory.

Interactions between macrophytes and phytoplankton have been studied extensively in temperate water bodies, but far less attention has been paid to those for emergent macrophytes in the tropics. We investigated the effects of six emergent macrophyte species (Brachiaria mutica, Ipomoea aquatica, Sphagneticola trilobata, Ludwigia adscendens, Pandanus amaryllifolius and Persicaria barbata) on the phytoplankton community of a tropical reservoir using ex situ experiments with multiple planting densities (Treatment 1: 0.108, Treatment 2: 0.24, Treatment 3: 0.40, Treatment 4: 0.58 g dry weight L−1) in 100-L mesocosms. Chlorophyll a (as a proxy of total phytoplankton biomass) and phytoplankton community structure were examined. The initial phytoplankton community (average chlorophyll a: 20.36 ± 0.69 µg L−1) was dominated by cyanobacteria: Planktolyngybya, Pseudanabaena and Cylindrospermopsis (average relative biovolume 0.68 ± 0.03). Over four weeks, L. adscendens (Treatments 3 and 4) and P. barbata (Treatments 2 to 4) significantly reduced chlorophyll a concentrations by 3.29–6.69 µg L−1 compared to the controls. Comparing species effects over four weeks for Treatment 4, P. barbata significantly lowered chlorophyll a concentrations compared to I. aquatica while there were no significant differences between all other species. All treatments of L. adscendens and P. barbata significantly reduced the relative biovolume of cyanobacteria in the phytoplankton communities by 0.19–0.39 compared to the controls. The highest-density treatments of all six macrophyte species led to significant shifts in the phytoplankton community structure by reducing the relative abundance of filamentous cyanobacteria (Planktolyngbya, Pseudanabaena) and/or increasing the relative abundance of cryptomonads (Chroomonas, Rhodomonas). This study shows the potential of emergent macrophyte species, especially L. adscendens and P. barbata, to reduce total phytoplankton biomass and cyanobacterial dominance in tropical water bodies, and a range of plant densities which were effective.

Water pollution caused by excessive nutrient and biological invasion is increasingly widespread in China, which can lead to problems with drinking water as well as serious damage to the ecosystem if not be properly treated. Aquatic plant restoration (phytoremediation) has become a promising and increasingly popular solution. In this study, eight native species of low-temperature-tolerant aquatic macrophytes were chosen to construct three combinations of aquatic macrophytes to study their purification efficiency on eutrophic water in large open tanks during autumn in Guangzhou City. The total nitrogen (TN) removal rates of group A (Vallisneria natans + Ludwigia adscendens + Monochoria vaginalis + Saururus chinensis), group B (V. natans + Ipomoea aquatica + Acorus calamus + Typha orientalis), and group C (V. natans + L. adscendens + Schoenoplectus juncoides + T. orientalis) were 79.10%, 46.39%, and 67.46%, respectively. The total phosphorus (TP) removal rates were 89.39%, 88.37%, and 91.96% in groups A, B, and C, respectively, while the chemical oxygen demand (COD) removal rates were 93.91%, 96.48%, and 92.78%, respectively. In the control group (CK), the removal rates of TN, TP, and COD were 70.42%, 86.59%, and 87.94%, respectively. The overall removal rates of TN, TP, and COD in the plant groups were only slightly higher than that in CK group, which did not show a significant advantage. This may be related to the leaf decay of some aquatic plants during the experiment, whereby the decay of V. natans was the most obvious. The results suggest that a proper amount of plant residue will not lead to a significant deterioration of water quality.

A hydroponic experiment has been conducted for desalination of saline water by culturing Ipomoea aquatica, Alternanthera philoxeroides and Ludwigia adscendens at 0–7 dS m−1 salinity level. Water samples were collected at 15-day interval, and the plants were harvested after 45 days. They were separated into root, stem and leaf. EC value decreased in water with increasing time for all halophytes. Root and leaf contain higher amounts of sodium as compared with those of stem. The highest accumulation of sodium was found in the root of A. philoxeroides (145.63 g kg−1); however, I. aquatic has high phytodesalination capacity (130 kg Na+ ha−1) due to high productivity than A. philoxeroides (105 kg Na+ ha−1) and L. adscendens (80 kg Na+ ha−1). Bio-concentration factors (56.10–80.29) and translocation factor values (˃ 1) indicated that these halophytes were good sodium accumulator. Sodium adsorption ration values lied between 16.8–18 at 3 dS m−1 and 20–25.5 at 5 and 7 dS m−1 showed that these halophytes improved the water quality for irrigation. Anatomical variation from microscopic cellular images illustrated that spongy mesophyll cells along with sub-stomatal cells in leaf and xylem vessels along with vacuolar sequestration might be responsible for Na accumulation in the stem of these halophytes.

The purpose of this research was to monitor the distribution of Cd, Cr, Cu, Ni, Pb and Zn in plants of Lagos lagoon wetlands in Nigeria. Water, soil and dominant plants were collected from 46 sampling points for a period of 1 year and analysed using ICP-AES. The order of heavy metals presence in soil samples was as follow: Zn>Cr>Cu>Pb>Cd>Ni. The Zn concentration was the highest whereas the lowest concentration was Ni. All water samples showed varying degrees of contamination across all the sampling points in these wetlands. A greater percentage of all metals concentration for Pb, Cd, Cr and Ni were higher than the permissible limit set by World Health Organisation. Pb ranged from 0.01±0.00 to 0.91±0.04 mg/L, Cd from 0.01±0.00 to 0.31±0.02 mg/L, Cr from 0.05±0.00 to 1.15±0.01 mg/L, Ni from 0.01±0.00 to 0.52±0.03, Cu from 0.21±0.01 to 1.11±0.01 mg/L and Zn ranged from 0.15±0.00 to 10.28±0.02 mg/L. The median values of each metal that the shoots and roots of individual plants accumulated metals in the order: Zn>Cu>Pb>Cr>Ni>Cd. Ipomea aquatica had the highest concentration of Pb in its shoot (1.12 mg/kg) while Ludwigia adscendens had the least (1.12 mg/kg) in its shoot. Pb level in the roots was highest in Eichonia crassipes (5.69 mg/kg). The highest level of Cr in shoot (2.23 mg/kg) and root (5.41 mg/kg) was observed in Commelina benghalensis while Cr concentration is lowest in the shoot (0.04 mg/kg) and root (0.18 mg/kg) of Althernathera philoxerrides. Ludwigia adscendens had the lowest concentration of Ni in its root (0.01 mg/kg). The highest shoot concentration of Cu (4.21 mg/kg) was observed in Eichonia crassipes while Ipomea aquatica had the lowest concentration in its shoot (0.23 mg/kg). Paspalum vaginatum’s root had the highest Cu concentration (12.32 mg/kg) while lowest concentration of Cu was observed in the root of Sagittaria sagittifolia (0.69 mg/kg). Transfer factors for most of the plants species were less than 1, indicating that metals accumulated by these plants were largely retained in the roots. A. philoxerrides had translocation factor greater than one for Ni (10.30), while for Cr was 1.25 and 1.40. This present findings indicate that, despite ecological similarities, the different plant species tend to respond differently to exposure to heavy metals and also in their ability to accumulate the various metals. Thus, heavy metals sequestration from the soil to these plants characterized them as metals pollution indicators.Keywords: wetland plants, heavy metals, biomonitoring, bioaccumulation capacity, translocation factor

Aims In wetlands, water levels can fluctuate, which often disturbs local organisms, such as aquatic plants. The responses of Alternanthera philoxeroides, Myriophyllum aquaticum, and Ludwigia adscendens to water level fluctuations of different frequencies were examined here. Methods Water level fluctuations were simulated at four frequencies: static (0 frequency), one cycle (1 fre- quency), two cycles (2 frequency), and four cycles (4 frequency), and with fluctuation amplitudes (± 25 cm) dur- ing a 60 day experiment. Morphological and physiological traits of plants, including branching number, shoot length, total biomass, shoot root ratio, chlorophyll content, and maximum PSII quantum efficiency (Fv/Fm) were assessed. Important findings Water level fluctuation was found to have no significant impact on branching number, root shoot ratio, or Fv/Fm of A. philoxeroides, but all scenarios except 1 frequency were significantly associated with longer shoots and lower total biomass and chlorophyll content. The traits of M. aquaticum showed different re- sponses to water level fluctuation: branching number and Fv/Fm showed no changes, but shoot length (2 fre- quency) and root shoot ratio (1 and 4 frequency) increased significantly, and total biomass and chlorophyll content (expect 4 frequency) decreased. In L. adscendens, water level fluctuation was associated with lower branching number in all scenarios except 2 frequency, shoot length in all scenarios except 1 and 2 frequency, total biomass in all scenarios except 2 frequency, and chlorophyll content but had no significant effects on root shoot ratio or