Reproductive success and genetic structure of populations of the heterostylous aquatic plant Nymphoides indica (L.) Kuntze (Menyanthaceae)

Differences in the reproductive mode (sexual and vegetative reproduction) between populations of a species may produce diverse patterns of genetic structure within and among populations. We analyzed the clonal diversity of populations of a heterostylous plant (Nymphoides indica (L.) Kuntze) having different floral morph ratios in the Higashi-harima area of Japan. The number of MLGs (multilocus genotypes) in populations with equal floral morph ratios was significantly higher than that among populations with biased floral morph ratios and among monomorphic populations. Populations with equal floral morph ratios followed the Hardy–Weinberg equilibrium. A dispersal distance of 0–4.2 km was significantly correlated with Nei's genetic distance, supporting a stepping-stone model of dispersal. Four rare MLGs were included in populations with equal floral morph ratios, distributed among neighboring populations. We concluded that clonal diversity of N. indica in the Higashi-harima area is maintained by the success of seed production and establishment of seedlings, and by the proximate occurrence of habitats around the populations where successful sexual reproduction occurs.     

Hg^2＋对金银莲花根和叶片的伤害

研究了汞离子胁迫下金银莲花〔Ｎｙｍｐｈｏｉｄｅｓｉｎｄｉｃａ（Ｌ．）Ｋｕｎｔｚｅ〕根受害情况、根部过氧化物酶活性和新叶叶绿素含量的变化。根部受害程度随汞离子浓度升高和处理时间的延长而加重。低浓度Ｈｇ２＋短时间处理后根过氧化物酶活性升高,而高浓度Ｈｇ２＋长时间处理后根过氧化物酶活性下降,且随着Ｈｇ２＋浓度的升高或处理时间的延长过氧化物酶活性均呈下降趋势。新叶叶绿素含量对Ｈｇ２＋胁迫的反应与根过氧化物酶活性的变化相似。     

Calcium-Dependent Lamina Production of Nymphoides peltata (Gmel.) O. Kuntze (Menyanthaceae): Implications for Distribution

Nymphoides peltata (Gmel.) O. Kuntze, a nymphaeid macrophyte,occurs commonly in polder and fluviatile areas in large partsof Europe and Asia. In contrast to the nymphaeid macrophytesNymphaea alba L. and Nuphar lutea (L.) Sm., Nymphoides peltatais almost completely absent from poorly-buffered waters andis never found in acid water bodies. Transplantation experimentsin water bodies of varying alkalinity demonstrated that, irrespectiveof the sediment type, leaf production of Nymphoides did occurin poorly-buffered waters, but not in acid waters. Cultivation experiments showed that floating leaf developmentof Nymphoides peltata could only take place if sufficient calciumwas available in the water layer or in twice-demineralized water.Addition of calcium to an acid cultivation medium or to watercollected from an acid moorland pool resulted in leaf production.Growth of Nymphoides in acid waters is impossible due to insufficientcalcium concentrations in the water layer of such waters. Itis suggested that the absence of Nymphoides peltata in somepoorly-buffered water bodies is partly due to the spatial isolationfrom rivers and canals and the high frequence of desiccation.The restricted occurrence of Nymphoides peltata to well-bufferedalkaline waters is functionally more related to the calciumavailability than to the bicarbonate content. Key words: Aquatic macrophytes, distribution, Nymphoides peltata, leaf production, calcium, acid, poorly-buffered and alkaline water     

Conservation of the Lake Kasumigaura population of Nymphoides indica (L.) Kuntze based on genetic evaluation using microsatellite markers

We compared the genetic diversity of the Lake Kasumigaura population of Nymphoides indica with that of pond populations in Hyogo and Kagawa Prefectures, which are thought to maintain high genetic diversity, to elucidate the current genetic diversity and occurrence of distinctive alleles in the Lake Kasumigaura population. The genetic diversity, as measured by the mean number of alleles per polymorphic locus, effective number of alleles per locus, mean observed heterozygosity, mean expected heterozygosities, total gene diversity, and number of multilocus genotypes was lower in the Lake Kasumigaura population than in the Hyogo and Kagawa populations. In addition, the inbreeding coefficient suggests that random mating does not occur in the Lake Kasumigaura population. The degree of genetic differentiation between the Lake Kasumigaura population and the Hyogo and Kagawa populations suggests that the Lake Kasumigaura population is largely genetically distinct. We found five genotypes in the Lake Kasumigaura population that were absent from the Hyogo and Kagawa populations. These results demonstrate that the Lake Kasumigaura population is an important component of the overall genetic diversity of N. indica in Japan.     

Isolation and characterization of highly polymorphic microsatellites in the aquatic plant,Nymphoides peltata (Menyanthaceae)

Ten microsatellite loci were described for conservation design of a threatened clonal aquatic plant, Nymphoides peltata. The microsatellite loci obtained through the construction of an enriched library were polymorphic (2–6 alleles per locus) and exhibited high levels of observed (0.333–0.889) and expected (0.284–0.765) heterozygosities. All microsatellite loci were expected to be useful for identification of genets and evaluation of genetic diversity of this species.     

Life-history differentiation in Nymphoides coreana (Menyanthaceae) populations in aquatic habitats with different disturbance regimes in Japan

Different disturbance regimes in aquatic habitats may bring about life-history differentiation in aquatic plants. However, there is little information on this association. Adult longevity, seed size and mass, and seed-germination characteristics were surveyed for Nymphoides coreana populations, which grow in different types of aquatic habitats, to demonstrate life-history differentiation. Seed size and seed mass were significantly greater in paddy-field populations (disturbed habitats) than in irrigation-pond populations (stable habitats). Paddy-field populations were composed of annuals, whereas irrigation-pond populations contained perennials. Seed-germination characteristics were significantly different between paddy-field and irrigation-pond populations. The moist-chilling pretreatment period needed to release innate seeds from dormancy was significantly shorter in paddy-field populations than in irrigation-pond populations. The percentage of seeds that germinated was significantly higher under anaerobic conditions, irrespective of light, and under light aerobic conditions compared to dark aerobic conditions in paddy-field populations. Conversely, in irrigation-pond populations, the percentage of seeds that germinated was highest under light anaerobic conditions. These results show that the reaction norm of seed-germination characteristics was significantly broader in annual populations than in perennial populations. The occurrence of aquatic habitats with different disturbance regimes thus contributes to the maintenance of phenotypic diversity in N. coreana populations.     

Growth and reproductive characteristics of an aquatic macrophyte Ottelia alismoides (L.) Pers. (Hydrocharitaceae)

Life history and reproductive traits of a submerged aquatic weed, Ottelia alismoides (L.) Pers., were studied in irrigation ponds in southwestern Japan. In addition, growth and seed production were investigated in relation to nutrient condition and water depth. The size of plants was very variable but reproductive allocation was nearly constant irrespective of the plant size at reproductive stage, amounting to more than 30% at maximum. Bagging experiments confirmed autogamy of the species. Ottelia alismoides grew best in nutrient-rich water with mud substratum. The optimal water depth for the growth of the species was approximately 50 cm compared with 20 and 90 cm. However, the reproductive allocation and seed set rate did not change much in different nutrient and water depth conditions. The seeds were produced by cleistogamous flowers in a depth of 90 cm. Morphological and ecological plasticity revealed in the present study was considered to be adapted to unstable environments such as rice fields and irrigation ponds liable to water-level fluctuation. The conditions required for the restoration of the populations of O. alismoides are discussed based on the present results.     

Structure and annual biomass production of Nymphoides peltata (Gmel.) O. Kuntze (Menyanthaceae)

In 1980, the monthly changes in biomass and plant surface area, together with aspects of production of Nymphoides peltata (Gmel.) O. Kuntze were studied in a backwater of the river Waal (The Netherlands). Furthermore, the seasonal changes in the vertical stratification of the biomass were studied in concrete tanks. These seasonal changes were studied with the harvest method, while the estimation of the net primary production was based upon biomass data and turnover rates of various plant parts. The data thus obtained are compared with those of other water plants, especially other floating-leaved macrophytes. In 1980, N. peltata reached its peak biomass in August being 372 g AFDW m⁻² (ash-free dry weight). The annual net productivity of Nymphoides was estimated to be 1036 g AFDW m⁻². The leaf blades and their petioles contributed most to the production.     

Competitive Performance of Nymphoides Peltata (Gmel.) O. Kuntze Growing in Microcosm

Two experiments were conducted to investigate the effects of competition on growth and performance of Nymphoides peltata (Gmel.) O. Kuntze in microcosm. Part of the research on growth and biomass allocation of N. peltata in response to competition had been reported early (Wu, Z. & D. Yu, 2004, Hydrobiologia 527: 241–250). This paper focuses on the morphological variations of N. peltata under competitive pressure. First, competition between N. peltata and Zizania latifolia (Griseb.) Turcz. ex Stapf. was assigned with the densities of N. peltata to Z. latifolia ratios of 4:0, 4:2, 4:4 and 4:8. Water surface coverage, surface area per leaf blade and number of leaves per plant of N. peltata all declined significantly with increasing density of competitor. Similar results were also found for petiole length and density of branching. However, the variations of planting density did not significantly affect the number of ramets per plant and the stolon length of N. peltata. Second, competitions between N. peltata and emerged Z. latifolia, floating-leaved Trapa bispinosa Roxb. and submerged Myriophyllum spicatum L. were also studied simultaneously. The results showed that significant difference was only found for the water surface coverage of N. peltata. No other significant differences were found for the number of ramets per plant, number of leaves per plant, density of branching, surface area per leaf blade, petiole length, and stolon length of N. peltata. Our studies indicate that N. peltata presents morphological variations when it is growing with Z. latifolia, such that the growth of above-ground parts decrease (i.e., leaf number, petiole length, branching density) and the growth of below-ground parts remains stable (i.e., stolons length). However, N. peltata does not show apparent differences in morphology when it is growing with T. bispinosa or M. spicatum. Accordingly, we conclude that the growth of N. peltata may be apparently inhibited by the presence of Z. latifolia, while T. bispinosa and M. spicatum may have little impact on the growth and performance of N. peltata.     

Nymphoides peltata (Gmel.) Kuntze, Myriophyllum spicatum L. and Ceratophyllum demersum L. biomass dynamics in Lake Provala (the Vojvodina Province, Serbia)

Sixty-five plant species have been found in Lake Provala (the Vojvodina Province, Serbia) and its riparian zone. Among them, three hydrophytes were dominant: Nymphoides peltata, Myriophyllum spicatum and Ceratophyllum demersum. As interactions between different ecological factors, especially light, temperature and nutrient level, are of prime importance for productivity of macrophytes, we analyzed the main physical and chemical indicators of water quality in the studied location. In the vegetation period of the year 2000, the dominant hydrophytes were analyzed for biomass production dynamics in the studied aquatic ecosystem, including fresh weight (FW), dry weight (DW) and ash free dry weight (AFDW). The studied plant species achieved maximum biomass production in June, with statistical differences among the species at the significance level of α = 0.05.     

The Effects of Competition on Growth and Biomass Allocation in Nymphoides peltata (Gmel.) O. Kuntze Growing in Microcosm

Two experiments were designed to investigate the effects of competition on growth and biomass allocation in Nymphoides peltata. First, competition between N. peltata and Zizania latifolia was assigned with the densities of N. peltata to Z. latifolia ratios of 4:0, 4:2, 4:4 and 4:8. The increase of density of Z. latifolia resulted in apparent decrease of total biomass, relative growth rate (RGR), leaf area ratio (LAR) and mean leaf area per plant of N. peltata. N. peltata allocated above-ground biomass to shoots and roots and decreased the ratios of above-ground to below-ground biomass (A _b/B _b) with increasing density of Z. latifolia. Second, competitions between N. peltata and emerged Z. latifolia, floating-leavedTrapa bispinosa and submerged Myriophyllum spicatum were studied in the mean time. Total biomass, A _b/B _b and mean leaf area per plant of N. peltata were higher when competing with floating-leaved T. bispinosa than in N. peltata growing in the community with submerged M. spicatum and emerged Z. latifolia. There were no significant differences in RGR, net assimilation rate (NAR) and LAR of N. peltata when growing with each of the competitor species. Our studies indicate that the growth of N. peltata is strongly inhibited by the presence of Z. latifolia, and N. peltata can show certain competitive advantages over T. bispinosa and M. spicatum.     

Digestion of an aquatic macrophyte by Tilapia zillii (Gervais)

The digestive efficiency of Tilapia zillii fed Najas guadalupensis was studied in the laboratory. Digestion was dependent on the ability of the fish to triturate the plant tissues. Based on a dietary reference, cellulose, the total digestibility of Najas was 29.3%. Digestive efficiency of the fish for non-cellulose organic matter, protein and fat was 55.7%, 75.1% and 75.9%, respectively. Of the total caloric content of the plant, 45.4% was assimilated. An estimate was made of the amount of Najas necessary to satisfy the caloric expenditure of the fish.     

基于转录组测序信息的水生植物莕菜SSR标记开发

利用软件MISA对水生植物莕菜转录组测序所获得的79536条EST序列进行分析,共检测出12319个EST-SSR位点。在莕菜的EST-SSR中,二核苷酸和三核苷酸重复单元是主导类型,分别占总SSR的57.31%和30.87%,其中AG/CT、AAG/CTT分别是二、三重复单元类型的优势重复基元,分别占总SSR的29.76%和8.66%。随机挑选了130对EST-SSR引物对莕菜两个居群进行遗传多样性检测,结果发现：78对引物能扩增出清晰可分辨的条带,其中37对能成功检测出多态性,引物多态率为 47.44%。这些多态性引物共检测出114个等位基因,每个位点2~6个,平均3.08个。观测杂合度（H_o）及预期杂合度（H_e）分别在0.229~1.000和0.351~0.756之间,多态信息含量PIC值在0.286~0.698之间,平均达0.495。以上研究结果表明,通过莕菜转录组测序产生的EST数据来开发SSR标记是一种简单而高效的途径,这些新的SSR分子标记为研究莕菜的居群遗传多样性及其遗传结构提供了工具。     

外来物种黄顶菊花器官分化的初步研究

利用扫描电镜(SEM)观察了黄顶菊(Flaveria bidentis(L.)Kuntz)花序发育过程中蝎尾状聚伞花序、头状花序和小花的形成.黄顶菊的花序由主轴及一至三级分枝组成,各级分枝交互对生,形成方式相同.植株主轴和侧枝顶端的每个花序由3～6个蝎尾状聚伞花序密集而成;每一蝎尾状聚伞花序由5～15个头状花序组成;每一头状花序中有4～11枚小花.小花分化顺序为5个花冠原基、5个雄蕊原基和2个心皮原基.2007年,天津地区黄顶菊的花期是7月下旬到9月下旬.7月中旬,花序和花器官原基不断形成并分化,至花器官成熟经历的时间约15 d.     

Germination requirements and seed banks of some nymphaeid macrophytes: Nymphaea alba L., Nuphar lutea (L.) Sm. and Nymphoides peltata (Gmel.) O. Kuntze

SUMMARY.

• 1 Germination experiments demonstrated that the innate dormancy of the seeds of Nymphaea alba L., Nuphar lutea (L.) Sm. and Nymphoides peltata (Gmel.) O. Kuntze could be overcome by a cold treatment. Light stimulated the germination of the three species. Hypoxic conditions stimulated the germination of Nymphaea alba and Nuphar lutea seeds but the seeds of Nymphoides peltata did not germinate under these conditions.
• 2 Experimental seed banks of Nymphaea alba, Nuphar lutea and Nymphoides peltata were laid out in three water bodies, varying in pH and alkalinity. Germination patterns indicated that Nymphaea alba and Nuphar lutea produce transient seed banks, but that Nymphoides peliata produces a persistent seed bank. Sampling of natural seed banks and subsequent germination tests were in concordance with the results of the seed bank experiment.
• 3 The experimental above-ground seed banks of Nymphaea alba, Nuphar lutea and Nymphoides peltata showed similar germination patterns in the three selected water bodies, despite the differences in pH and alkalinity between them. However, the distribution of Nymphoides peliata is restricted to well-buffered waters, so that its absence from soft and acid water bodies must be due to post-germination mechanisms and/or processes.
• 4 In aquatic systems where Nymphoides peltata co-exists with the other nymphaeid species studied, it is largely restricted to a bell between the helophytes and the vegetation at deeper sites. The deeper sites were dominated by Nuphar lutea and Nymphaea alba. Germination requirements and seedling emergence from buried seeds of Nymphaea alba, Nuphar lutea and Nymphoides peliata play an important role in the establishment of the zonation pattern of these nymphaeid macrophytes.

     

The impact of aquatic macrophyte (Salix sp. and Cladium mariscus (L.) Pohl.) removal on habitat conditions and macroinvertebrates of tufa barriers (Plitvice Lakes, Croatia)

The effects of aquatic macrophyte (willows and sawgrass) removal on flow velocity, tufa deposition, POM dynamics, and macroinvertebrate community structure were studied in the tufa barrier habitats of the barrage system of Plitvice Lakes, Croatia. Samples were collected from two hydraulic habitats (fast > 100 cm s⁻¹ and slow < 100 cm s⁻¹) at both a control (no macrophytes removed) and impact (macrophytes removed) site. Samples were collected with a core sampler (four layers in vertical profile of barrier bed) monthly on 6 dates before and 7 dates after the removal of macrophytes. Macrophytes were removed in May 2002 at the impact site. After the macrophyte removal flow velocity decreased significantly at both hydraulic habitats. Retarded flow resulted in: (a) a decrease in macroinvertebrate density and diversity since most of the taxa were rheophilic (preferring habitats with higher flow velocity) and (b) an increase in POM concentrations (FPOM and UPOM) since decreases in flow velocity facilitate particle deposition in lotic habitats. The effects of macrophyte removal were present, and diminish along the vertical sediment profile of the barrier bed. Tufa deposition was not influenced by the macrophyte removal. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

Boron re-translocation in tea (Camellia sinensis (L.) O. Kuntze) plants

Boron (B) re-translocation is an important factor determining tolerance to B deficiency in plants. In this work growth, B content of leaves with different ages, B partitioning between soluble and cell wall (CW) fractions, and B re-translocation were investigated in tea (Camellia sinensis (L.) O. Kuntze) plants grown hydroponically without (<2.5 μM) and with adequate (46 μM) B supply. Under B deficiency, the proportion of CW bound B increased in the old leaves but decreased in roots. Contrastingly, the proportion of CW bound B was not influenced by B supply in the young leaves. A continuous reduction of B content was observed in all fully expanded leaves as well as in roots of low B plants. Taken together, these results revealed considerable re-translocation of B from mature to growing leaves. Leaf extract and phloem exudate samples were analyzed and sucrose, glucose, and fructose were detected while xylitol, sorbitol, mannitol, maltose, galactose, cellobiose or rafinose were not found in these samples. In the leaf extracts, concentration of sucrose increased under B deficiency conditions, concentration of glucose decreased, while that of fructose remained unchanged. Our results provide circumstantial evidence for a considerable re-translocation of B in tea plants despite lacking polyol compounds.     

Micropropagation of tea (Camellia sinensis (L.) O. Kuntze) using Thidiazuron

The effect of thidiazuron (TDZ) on the micropropagation of Camellia sinensis (China hybrid) was compared with that of benzylaminopurine (BAP) using nodal segments from in vitro raised seedlings. Extremely low concentrations of TDZ (1pM–100nM) alone were effective in inducing shoot bud proliferation and maintaining high rates of shoot multiplication on hormone-free media. On the other hand, higher concentrations of BAP (1–10M) and its continued presence were required to initiate and sustain shoot proliferation. While wider ranges of BAP combined favourably with auxins like NAA or IBA, only specific combinations of TDZ and NAA were effective for shoot proliferation. TDZ treated explants yielded healthy shoots, with sturdy leaves, even during the initial stages of growth, whereas, the effect of BAP was cumulative over subcultures in attaining a high proliferative rate.     

Acid phosphatase activity in intercellular spaces in roots of Nymphoides peltata (S. G. Gmel.) O. Kuntze

Abstract. Acid phosphatase was found cytochemically in intercellular spaces in the root of Nymphoides peltata. Different methods, using lead salts and azo-dyes, gave similar results. Reaction product appeared on material, possibly cytoplasmic, within the intercellular spaces and also against the outer walls of cells which formed the intercellular spaces. Possible functions of acid phosphatase in intercellular spaces are discussed.