Growth responses of eight wetland species to water level fluctuation with different ranges and frequencies.

Fluctuation range and frequency are two important components of water level fluctuation, but their effects on wetland plants have not been evaluated separately. We subjected eight wetland species to a control treatment with static water level and fluctuation treatments with different ranges or frequencies to examine their effects on plant growth. Acorus calamus, Butomus umbellatus and Iris wilsonii showed high survival rates in all treatments with various fluctuation ranges and frequencies. Their survival rates were higher at the medium fluctuation frequency than at the low and high frequencies, suggesting beneficial effects of the medium frequency. In the experiment comparing the fluctuation ranges, A. calamus and I. wilsonii could maintain the capacity for asexual propagation and accumulate higher biomass compared with the control plants, while biomass of the other six species dramatically decreased. In the experiment comparing fluctuation frequency, species with relatively high survival rates (≥ 50%) maintained or increased the capacity of asexual propagation, and A. calamus and I. wilsonii allocated relatively more biomass to roots, which may enhance plant growth and survival. In contrast, these species did not show increased biomass allocation to shoots in response to both fluctuation range and frequency, presumably because shoots are prone to mechanical damage caused by streaming floodwater. Taken together, biomass accumulation in roots rather than in shoots and the ability to asexually propagate are important for the survival of these species during water fluctuation.

Nitrogen Metabolism in Acorus calamus L. Leaves Induced Changes in Response to Microcystin-LR at Environmentally Relevant Concentrations.

Acorus calamus L., a semiaquatic plant with a high capacity to remove nitrogen and phosphorus from polluted water, is a potential candidate plant for use in the restoration of eutrophic aquatic ecosystems. However, it is not clear how microcystins (MCs), commonly found in eutrophic water, influence plant growth since the effects of MCs are likely to be dose and species dependent. The present study aimed to investigate the regulation of nitrogen metabolism, a key metabolic process related to plant growth, in the leaves of A. calamus L. exposed to microcystin-leucine-arginine (MC-LR) (1.0-29.8 µg/L). Nitrate (NO3-) uptake, assimilation and transformation was stimulated in the leaves of A. calamus L. when exposed to 1.0 µg/L MC-LR through the elevation of nitrate reductase (NR), glutamine synthetase (GS), glutamate synthase (GOGAT), glutamic-pyruvic transaminase (GPT), and glutamic-oxaloacetic transaminase (GOT) activity. Conversely, MC-LR inhibited nitrogen metabolism by decreasing NO3- uptake and the activities of enzymes related to nitrogen metabolism following exposure to MC-LR (9.9-29.8 µg/L) for 30 days, while, ammonium nitrogen (NH4+) content and glutamate dehydrogenase (GDH) activity increased significantly (p < 0.05, LSD test), when compared with the control group. Chronic exposure to MC-LR (9.9-29.8 µg/L) negatively influenced nitrogen metabolism in A. calamus L. leaves, which suggested that it may not be a suitable candidate species for use in the restoration of eutrophic aquatic ecosystems containing MC-LR at concentrations ≥ 9.9 µg/L.

Effects of antibiotics on nitrogen uptake of four wetland plant species grown under hydroponic culture.

To investigate the effects of antibiotics on nitrogen removal and uptake by wetland plants, four typical macrophyte species, Cyperus alternifolius L., Typha angustifolia L., Lythrum salicaria L., and Acorus calamus L., were grown in hydroponic cultivation systems and fed wastewater polluted with 10 µg L-1 Ofloxacin (OFL) and Tetracycline (TET). Biomass production, nitrogen mass concentration, chlorophyll content, root exudates, and nitrogen removal efficiency of hydroponic cultivation were investigated. The results indicated that in all hydroponic systems, NH4+-N was entirely removed from the hydroponic substrate within 1 day and plant nitrogen accumulation was the main role of the removed NO3-. OFL and TET stimulated the accumulation of biomass and nitrogen of A. calamus but significantly inhibited the NO3--N removal ability of L. salicaria (98.6 to 76.2%) and T. augustifolia (84.3 to 40.2%). This indicates that A. calamus may be a good choice for nitrogen uptake in wetlands contaminated with antibiotics. OFL and TET improved the concentrations of total organic carbon (TOC), total nitrogen (TN), organic acid, and soluble sugars in root exudates, especially for oxalic acid. Considering the significant correlation between TOC of root exudates and nitrogen removal efficiency, the TOC of root exudates may be an important index for choosing macrophytes to maintain nitrogen removal ability in wetlands contaminated with antibiotics.

The effect of substrates on the removal of low-level vanadium, chromium and cadmium from polluted river water by ecological floating beds.

Ecological floating beds (EFBs) is one of the effective methods lately used to remove heavy metals pollutions in water. However, the role of substrate in EFBs was mainly focused on the study of microorganisms, and the effect of substrates on plants enrichment of heavy metals was rarely investigated. This study aimed to investigate the promotion of different substrates (green zeolite, sepiolite, absorbent paper, and ceramsite) on the removal of multi-heavy metals (V, Cr, and Cd) by Acorus calamus L. It also investigated the plant growth status. Results showed that the relative increase rate of Acorus calamus L. fresh weight increased the most in EFBs with green zeolite group (EFB-GZ), which was 60.50%, higher than 38.17% in EFBs with Acorus calamus L. (EFB-A). The enrichment ability of multi-metals in Acorus calamus L. was stronger in EFBs with substrates than in EFB-A, and green zeolite was the best. After 34 days, the total removal efficiency of V, Cr and Cd in EFB-GZ were 79.91%, 95.24% and 91.80%, respectively. Heavy metals translocation from root to shoot influenced by the kinds of substrates. In EFB-GZ, the translocation factor (TF) of V, Cr and Cd were 0.081, 0.263 and 0.180, respectively (0.024, 0.608 and 0.032 in EFB-A). The ability of Acorus calamus L. to resist multi-metals stress was significantly higher in EFBs with substrates than that in EFB-A and the activity of SOD, POD and CAT were increased by heavy metals stress. Our results acquired that green zeolite was the best substrate to promote multi-metals uptake by Acorus calamus L., which could effectively maintain the pH of water, provide a stable environment and nutriment for Acorus calamus L. Green zeolite can promote the translocation of V and Cd from root to shoot in Acorus calamus L., but is not conducive to Cr.

[Effect of Biochar on Root Morphological Characteristics of Wetland Plants and Purification Capacity of Constructed Wetland].

A constructed wetland with Acorus calamus L. was built. Straw biochar, reed biochar, and sawdust biochar was added into the constructed wetland individually to study the effect of different biochars on the root morphology, dissolved oxygen, and purification ability of the constructed wetland. The results show that the total root length, total projection area, total volume, total surface area, root number, branch number, and root dry weight of Acorus calamus L. significantly increased when all three kinds of biochar were added into the constructed wetland (P<0.05). Similarly, adding the biochars into the constructed wetland also significantly increased dissolved oxygen content in the wetland (P<0.05). Addition of sawdust biochar into the constructed wetland increased the root length, projection area, surface area, total volume, number of root tips, number of branches, and root dry weight of Acorus calamus L. by 96.1%, 106.2%, 185.6%, 172.5%, 75.3%, 121.6%, and 84.9%, respectively. After adding biochars into the constructed wetland, the root morphology of Acorus calamus L. and dissolved oxygen content was significantly correlated with removal rate of TN, TP, and COD, respectively. Addition of sawdust biochar into the constructed wetland significantly increased the removal rates of total nitrogen, total phosphorus, and COD when the hydraulic load was 0.022 m3·(m2·d)-1 (P<0.05). These results suggested that the addition of sawdust biochar to the constructed wetland increased the root growth of Acorus calamus L. and enhanced dissolved oxygen content, resulting in purification capacity of the constructed wetland.

[Influence of Biochar Application on Growth and Antioxidative Responses of Macrophytes in Subsurface Flow Constructed Wetlands].

Constructed wetlands (CWs) have high potential for wastewater treatment in developing countries because of their operational convenience and low maintenance costs. However, rapid accumulation of macrophytes in these wetlands, as a result of plant litter recycling, can lead to lower removal efficiencies. Periodic harvesting is consider to be the effective measure to maintain the wastewater treatment performance, and so a lot of harvested plant waste needs to be properly disposed of. However, in China, plant waste is usually used for agricultural burning and the greenhouse gas emissions bring adverse effects on the atmospheric environment. In the traditional subsurface flow CW, the dissolved oxygen (DO) concentration is low, resulting in long-term anoxic or anaerobic conditions, which will bring damages to plant body, such as membrane lipid peroxidation and protein and DNA damage. Generally, the addition of biochar to CWs is beneficial for aeration, and improves the internal environment of wetlands. Hence, the effects of plant biochar on the pollutant purification efficiencies in CWs were studied, and the role of biochar in macrophyte growth and antioxidative response was investigated. Based on the results of biochar application in agricultural fields, the harvested wetland plant straw was pyrolyzed to biochar at 500 ℃ under a dynamic high-purity nitrogen atmosphere. The wetland plant Acorus calamus L. (AC) was chosen for this study. The impact characteristics of biochar on AC were studied in five independent CWs built in a greenhouse, by combining the analyses of growth and antioxidative responses of plants. Results showed that the removals of ammonium (NH4+-N) and total nitrogen (TN) were significantly enhanced when biochar was added to CWs and that higher long-term nitrogen removal rates were achieved when the biochar application rate was increased. The photosynthetic pigment content in AC increased significantly with increasing biochar application rate. This stimulated photosynthesis and increased the soluble protein (SP) and plant biomass amounts. Further, glutamine synthetase (GS) activity was strengthened with the addition of biochar. This helped enhance the NH4+-N metabolism and increased the relative uptake rate of AC. This study confirmed that long-term anoxic or anaerobic conditions in CWs cause membrane lipid oxidation in plants. However, the activity of the antioxidative response system was promoted with the addition of biochar, significantly decreasing the malonic dialdehyde (MDA) content in the plants.

Effects of lead stress on the growth, physiology, and cellular structure of privet seedlings.

In this study, we investigated the effects of different lead (Pb) concentrations (0, 200, 600, 1000, 1400 mg kg-1 soil) on the growth, ion enrichment in the tissues, photosynthetic and physiological characteristics, and cellular structures of privet seedlings. We observed that with the increase in the concentrations of Pb, the growth of privet seedlings was restricted, and the level of Pb ion increased in the roots, stem, and leaves of the seedlings; however, most of the ions were concentrated in the roots. Moreover, a decreasing trend was observed for chlorophyll a, chlorophyll b, total chlorophyll, net photosynthesis (Pn), transpiration rate (Tr), stomatal conductance (Gs), sub-stomatal CO2 concentration (Ci), maximal photochemical efficiency (Fv/Fm), photochemical quenching (qP), and quantum efficiency of photosystem II (ΦPSII). In contrast, the carotene levels, minimum fluorescence (F0), and non-photochemical quenching (qN) showed an increasing trend. Under Pb stress, the chloroplasts were swollen and deformed, and the thylakoid lamellae were gradually expanded, resulting in separation from the cell wall and eventual shrinkage of the nucleus. Using multiple linear regression analysis, we found that the content of Pb in the leaves exerted the maximum effect on the seedling growth. We observed that the decrease in photosynthetic activation energy, increase in pressure because of the excess activation energy, and decrease in the transpiration rate could result in maximum effect on the photosynthetic abilities of the seedlings under Pb stress. Our results should help in better understanding of the effects of heavy metals on plants and in assessing their potential for use in bioremediation.

Complex Interactions Between the Macrophyte Acorus Calamus and Microbial Fuel Cells During Pyrene and Benzo[a]Pyrene Degradation in Sediments.

This study investigated the interaction of the macrophyte Acorus calamus and sediment microbial fuel cells (SMFC) during the degradation of high molecular weight-polycyclic aromatic hydrocarbons (HMW-PAHs) in sediments. Over 367-days, the combination of macrophyte and SMFC led to an increase in pyrene and benzo[a]pyrene degradation rates by at least 70% compared to SMFC or macrophyte alone. While either the macrophyte or SMFC increased redox potential in sediments, redox potentials near the anode (approximately 6 cm depth) in the macrophyte-SMFC combination were markedly lower than that in the only macrophyte treatment. Moreover, rhizospheric bacterial communities in macrophyte-SMFC and macrophyte treatments were distinctly different. Aerobic genera (Vogesella, Pseudomonas, Flavobacterium and Rhizobium) and anaerobic genera (Longilinea, Bellilinea, Desulfobacca and Anaeromyxobacter) became dominant in the rhizosphere in macrophyte and macrophyte-SMFC treatments, respectively. In addition, the macrophyte-SMFC combination improved the numbers of not only aerobic but anaerobic PAHs degraders in sediments. So, the SMFC employment facilitated the formation of anoxic zones in sediments with oxygen loss and exudates from the roots. As a result, cooperation of anaerobic/aerobic microbial metabolism for accelerating HMW-PAHs removal occurred within sediments after combining macrophytes with SMFC.

Phytotoxicity assessment of atrazine on growth and physiology of three emergent plants.

The emergent plants Acorus calamus, Lythrum salicaria, and Scirpus tabernaemontani were exposed to atrazine for 15, 30, 45, and 60 days in a hydroponic system. Effects were evaluated investigating plant growth, chlorophyll (Chl) content, peroxidase (POD) activity, and malondialdehyde (MDA) content. Results showed that selected plants survived in culture solution with atrazine ≤8 mg L(-1), but relative growth rates decreased significantly in the first 15-day exposure. Chla content decreased, but MDA increased with increasing atrazine concentration. S. tabernaemontani was the most insensitive species, followed by A. calamus and L.salicaria. The growth indicators exhibited significant changes in the early stage of atrazine exposure; subsequently, the negative impacts weakened and disappeared. Plant growth may be more representative of emergent plant fitness than physiological endpoints in toxicity assessment of herbicides to emergent plants.

Effects of perchlorate on growth of four wetland plants and its accumulation in plant tissues.

Perchlorate contamination in water is of concern because of uncertainties about toxicity and health effects, impact on ecosystems, and possible indirect exposure pathways to humans. Therefore, it is very important to investigate the ecotoxicology of perchlorate and to screen plant species for phytoremediation. Effects of perchlorate (20, 200, and 500 mg/L) on the growth of four wetland plants (Eichhornia crassipes, Acorus calamus L., Thalia dealbata, and Canna indica) as well as its accumulation in different plant tissues were investigated through water culture experiments. Twenty milligrams per liter of perchlorate had no significant effects on height, root length, aboveground part weight, root weight, and oxidizing power of roots of four plants, except A. calamus, and increasing concentrations of perchlorate showed that out of the four wetland plants, only A. calamus had a significant (p<0.05) dose-dependent decrease in these parameters. When treated with 500 mg/L perchlorate, these parameters and chlorophyll content in the leaf of plants showed significant decline contrasted to control groups, except the root length of E. crassipes and C. indica. The order of inhibition rates of perchlorate on root length, aboveground part weight and root weight, and oxidizing power of roots was: A. calamus > C. indica > T. dealbata > E. crassipes and on chlorophyll content in the leaf it was: A. calamus > T. dealbata > C. indica > E. crassipes. The higher the concentration of perchlorate used, the higher the amount of perchlorate accumulation in plants. Perchlorate accumulation in aboveground tissues was much higher than that in underground tissues and leaf was the main tissue for perchlorate accumulation. The order of perchlorate accumulation content and the bioconcentration factor in leaf of four plants was: E. crassipes > C. indica > T. dealbata > A. calamus. Therefore, E. crassipes might be an ideal plant with high tolerance ability and accumulation ability for constructing wetland to remediate high levels of perchlorate polluted water.

[Influence of perennial flooding and drought on growth restoration of Acorus calamus in water-level-fluctuation zone of the Three Gorges Reservoir].

Acorus calamus L. is a common kind of wetland plant species in the Three Gorges Reservoir. In this study, we investigated the influence of perennial flooding on growth restoration of A. calamus in the lightless conditions and the drought stress on this plant species' growth after flooding. Our research provided the scientific basis for the selection of candidate species for vegetations restoration in water-level-fluctuation zone of the Three Gorges Reservoir. A. calamus plants were exposed to waters in the lightless conditions in September 2009 and September 2010 respectively and taken away from the waters and grew in natural conditions in the following March, April and May (named as S1, S2, S3). All plants in the control, S1 and S2 groups were challenged with drought stress in May for 20 days. During the experiment, the plant number and leaf number were recorded regularly, as well as leaf length and leaf width. The results showed that flooding restrained the germination of the plants with much less plant in flooding groups than the control, and the plant germination rate had inverse relation to the flooding time. Flooding promoted formation and elongation of the leaves in S1 and S2 groups, which showed higher leaf growth parameters, such as leaf length, leaf number, total leaf length of one plant and total leaf length of all plants than the control. However, all of these growth parameters in S3 group had significantly lower values compared to the control. The survival rate of the plants after flooding decreased significantly with longer flooding time. Besides, the leaf length and leaf width in S1 and S2 groups increased significantly but with decreased leaf number. Additionally, all growth parameters (leaf length, leaf width, leaf number, total leaf number, total leaf length of one plant, total leaf length of all plants) in S3 group decreased remarkably. Furthermore, drought decreased the values of all growth parameters and the plant number in the control, S1 and S2 groups notably. When drought stress was removed for 25 days, the leaf number in the control, S1 and S2 groups increased by 67.0% (P < 0.05), 66.7% (P < 0.05) and 36.2% (P < 0.05), respectively, and the total leaf length of one plant, total leaf length of all plants and total leaf number in S1 and S2 groups increased by 48.2%, 18.1%, 66.7%, 35.0%, 75.0% and 64.3%, respectively (P < 0.05). Therefore, A. calamus exhibited not only strong adaption and tolerance to flooding,but also robust growth restoration ability after flooding, as well as good restoration ability to the drought stress. In summary, A. calamus could be used as one kind of restoration or reconstruction species in water-level-fluctuation zone (especially not exposed to flooding in March or April) of the Three Gorges Reservoir.

[Effects of saltwater incursion on the microbiological characteristics and denitrification in a riparian rhizosphere soil in Chongming Island of Shanghai, East China].

A simulation test was conducted to study the effects of saltwater incursion on the microbiological characteristics and denitrification in the riparian rhizosphere soils vegetated with different plants in Chongming Island of Shanghai. Saltwater incursion changed the microflora in the rhizospheric soils. Except for actinomycete whose quantity had slight increase, the quantities of bacteria, fungi, nitrifiers, and denitrifiers all decreased to some extent by saltwater incursion, with the denitrifiers decreased by 51.8%, suggesting that the riparian soil microflora responded differentially to saltwater incursion. The activities of soil nitrogen-transforming enzymes were significantly inhibited by saltwater incursion, and the inhibitory effects differed with the enzymes. Nitrite reductase activity was most sensitive to saltwater incursion, with an inhibition rate of 43.5%, followed by urease activity, with 37.4% inhibition, and by dehydrogenase (29.5% inhibition). Saltwater incursion inhibited the denitrification, with the average denitrification rate decreased by 34.9%. There existed significant differences in the eco-physiological responses of the microbes in the rhizosphere soils vegetated with different plants to the saltwater incursion. The microbial quantities and enzyme activities showed the highest inhibition percentages in the rhizosphere soil of Zizania aquatica, followed by in the rhizosphere soils of Acorus calamus and Phragmites australis. Under saltwater incursion, the inhibition percentages of microbial quantities, enzyme activities, and denitrification rate in the rhizosphere soil of A. calamus-P. australis were significantly lower, as compared with those in the rhizosphere soils vegetated with Z. aquatica, A. calamus, and P. australis, respectively, suggesting that mixed vegetation showed a better buffer effect on the responses of riparian rhizosphere soil microbiological processes and denitrification to saltwater incursion.

Supplemental ultraviolet-B induced changes in essential oil composition and total phenolics of Acorus calamus L. (sweet flag).

The effect of supplemental UV-B radiation (sUV-B) was evaluated on the essential oil contents of sweet flag (Acorus calamus L.), a medicinal plant grown under natural field conditions. After the emergence of two leaves, plants were exposed to sUV-B radiation of 1.8 kJ m(-2) above the ambient level of UV-B. The level of essential oil and phenol contents increased with exposure to sUV-B. Exposure of sUV-B resulted in significant increase in p-cymene and carvacrol contents of essential oil. Decrease in the level of major component beta-asarone due to sUV-B treatment is of prime importance, because of its toxicological concern to human health.

Volatiles from leaves and rhizomes of Fragrant Acorus spp. (Acoraceae).

Three horticultural selections of Acorus gramineus Soland were investigated to determine the chemical composition of their leaves and rhizomes. The variety 'liquorice' was found to contain methylchavicol (49%) which accounts for the unusual anisic odor of this variety, while beta-asarone was the main component of A. christophii (43%) and 'yodo-no-yuki' (20%). The results are compared with calamus oils, and the possible biosynthetic precursors of the main components methylchavicol and beta-asarone are considered.

Developmental anatomy of the root cortex of the basal monocotyledon, Acorus calamus (Acorales, Acoraceae).

BACKGROUND AND AIMS: The anatomical structure and development of adventitious roots were analysed in the basal monocotyledon, Acorus calamus, to determine to what extent those features are related to phylogenetic position. METHODS: Root specimens were harvested and sectioned, either with a hand microtome or freehand, at varying distances from the root tip and examined under the microscope using a variety of staining techniques. KEY RESULTS: Roots of Acorus calamus possess a unique set of developmental characteristics that produce some traits similar to those of another basal angiosperm group, Nymphaeales. The root apical meristem organization seems to be intermediate between that of a closed and an open monocotyledonous root apical meristem organization. The open-type root apical meristem consists of a curved zone of cortical initials and epidermal initials overlying the vascular cylinder initials; the epidermal part of the meristem varies in its association with the cortical initials and columellar initials of the promeristem. The cortex develops an endodermis with only Casparian bands, a dimorphic exodermis with Casparian bands and suberin lamellae, and a polygonal aerenchyma by differential expansion, as also observed in the Nymphaeales and some dicotyledonous species. The stele has characteristics like those of members of the Nymphaeaceae. CONCLUSIONS: Specific anatomical and developmental attributes of Acorus roots seem to be related to the phylogenetic position of this genus.

Towards a comprehensive integration of morphological and genetic studies of floral development.

Floral developmental genetics has exploded as a discipline. In addition to the rich genetic database for well-established models (Arabidopsis, Antirrhinum, Zea), numerous species have become the focus of floral genomic and genetic initiatives. Extensive documentation of the developmental morphology of Arabidopsis flowers has facilitated the linkage of genes and morphology. Complete developmental series also need to be assembled for emerging systems of molecular studies of floral genes. We address issues of homology assessment in floral structures, emphasize the need for assembling a complete floral developmental series for each species studied molecularly and genetically, stress the importance of a common set of terminology, and suggest a set of 'landmarks' to designate major events in floral development. We compare the floral developmental series of three species with different floral morphologies and propose a consensus of developmental stages to facilitate comparison of gene expression patterns. Taxa occupying key phylogenetic positions offer great potential for generating hypotheses about the regulation of floral development.