Search

The genus Monochoria is represented in Sri Lanka by only two species, M. hastata and M. vaginalis . Of the two species M. vaginalis exhibits a high morphological diversity. A morphometric analysis was performed on the Sri Lankan members of the genus Monochoria to evaluate the morphological diversity exhibited by comparing 34 vegetative, anatomical and reproductive characters. Both cluster and principal coordinate analyses resulted in four clusters of which one corresponded to M. hastata , while M. vaginalis was divided into three phenetic groups indicating that the Sri Lankan M. vaginalis is a species complex involving more than one taxon. The length ratio of the lower spathe petiole to inflorescence stalk was identified as an informative character in delimiting the phenetic groups, a character that has not been considered before. Further, the occurrence of sub-palisade cavities that are filled with a red colored liquid in the leaves of two phenetic groups was a novel character for the genus as well as the family Pontederiaceae. Keywords: Monochoria vaginalis ; Morphological data; Sub-palisade cavities; Principal coordinate anaysis. Bangladesh J. Plant Taxon. 24 (1): 13–22, 2017 (June)

Invasive species benefit from advantageous trait values and/or trait plasticity in their invasion process when facing changing environments. However, few studies explored this mechanism on invasive macrophytes. The effects of soil on the invasion of macrophytes were studied little by previous researches. In the measurement of several traits related to resource utilization, we studied the plant responses to three representative types of riparian soil in Liangzi Lake, China. Using multi-species comparison, we explored the differences of trait values and trait plasticity among Eichhornia crassipes (Mart.) Solms and its non-invasive confamilial counterparts all in emergent life-form—exotic Pontederia cordata L. and native Monochoria vaginalis (Burm. f.) Presl ex Kunth. We measured leaf-level and root-level traits after harvest. We found that E. crassipes mainly showed trait value advantages in root-level traits in infertile soils, while some advantages of leaf-level traits were present but not obvious compared to the two confamilials. Besides, E. crassipes showed higher plasticity in several traits especially in some root-level traits than the two confamilials. We concluded that both trait values and trait plasticity especially in belowground traits play a crucial role in the invasion success of emergent E. crassipes.

Bioaccumulation potential of six ecotypes, collected from six different industrial zones of lower Indo-Gangetic basin of West Bengal, India,of Monochoria vaginalis, commonly known as oval-leafed pondweed has been investigated based on chromium (Cr), cadmium (Cd) andCopper (Cu) accumulation pattern in different plant organs. Bioaccumulation potential was assessed by bioaccumulation factors (BFs-leavesmetal concentration/soil metal concentration), bioconcentration factors (BCFs- roots metal/soil metal), transfer factors (TFs-leaves +rhizomes/roots) and enrichment factors (EFs-metals in edible parts/soil metal). Accumulation pattern significantly differed among ecotypes,and accumulation in plant organs was highly metal-specific. BFs for Cr and Cd were >>1 in most of the ecotypes while high TFs (>>1) werenoticed in six ecotypes for Cr and Cu. BCFs was >>1 in all the ecotypes for Cd accumulation only. EFs values for the three metals hoveredaround 1 but it was > 1.0 for Cu in all the six ecotypes. The results suggested that Cr and Cu predominantly accumulated in leaves and rhizomeswhile Cd was predominantly sequestered in roots of M. vaginalis ecotypes. Cu, a redox active metal, showed higher capability than Cd and Crto accumulate in edible parts. In the present study, potential plant parts in M. vaginalis have been identified as bioaccumulation organs withoutany apparent symptoms of toxicity which can be used as phytoremediation of heavy metal contamination in aquatic ecosystems of lower Indo-Gangetic basin of India.DOI: http://dx.doi.org/10.3126/ijasbt.v3i1.12193 Int J Appl Sci Biotechnol, Vol. 3(1): 9-15

The survey of weed occurrence was conducted to identify dominant weed species in the paddy field. Total 346 sites of the 12 regions in Chungbuk Province in Korea were investigated in July, 2013. Weed flora was composed of 43 species belonged to 15 families. The compositions of major plant families, Cyperaces, Poaceae, Pontederiaceae and Asteraceae, were 21.5, 17.4, 15.5 and 12.7%, respectively. Based on life cycle, weed species was grouped into annuals of 71.3 and perennials of 28.1%. The most dominant weed species in paddy fields of Chungbuk Province were Monochoria vaginalis (14.5%), followed by Scirpus juncoides (10.5%), Echinochloa oryzoides (9.3%), Eleocharis kuroguwai (7.0%), Aeschynomene indica (6.2%) et al. The similarity of paddy weeds in 12 regions observed through TWINSPAN analysis was distinguished by Persicaria longiseta, Aneilema keisak, Persicaria thunbergii, Fimbristylis millacea, Blyxa japonica, Digitaria ciliaris, Potamogeton distinctus, Cyperus nipponicus. This information could be useful for estimation of future weed occurrence and establishment of weed control methods in chungbuk province in Korea.

The seeds of Monochoria vaginalis require light to germinate. However, they are able to germinate in darkness in the presence of rice hulls. The mechanism of this phenomenon was investigated in this study, in which only the unsterilized seeds of Monochoria were induced to germinate by the presence of a rice hull extract. The rice hull extract was able to be replaced by either a mixture of amino acids and phosphate or a yeast extract. The culture media in which germination was observed always showed turbidity, indicating the propagation of bacteria, which were identified as Bacillus sp., Pedobacter sp., Pantoea sp. and Sphingomonas sp. Treatment with the individual bacterial species or combinations of these bacteria induced Monochoria seed germination when added to the media containing the rice hull extract. It was concluded that the rice hull extract accelerates the propagation of bacteria, which in turn digest the seed coat of Monochoria, facilitating its germination.

Monochoria vaginalis (Burm. f.) C. Presl. is a common weed in Oryza sativa L. fields that has use as a vegetable. The objective of the study was to evaluate the nutritional composition of leaves and flowers of M. vaginalis. Almost all essential and nonessential amino acids were present in leaves and flowers. The amount of nonessential amino acids, especially aspartic acid and glutamic acid, was higher in flowers than leaves. There was more nitrogen in leaves (9.7 mg/100 g) than flowers (6.3 mg/100 g). Phosphorus, potassium, magnesium copper, manganese, and calcium were found in samples in levels that would allow this plant to provide adequate nutrition. Proteins (10.8 g/100 g) and carbohydrates (4.6 g/100 g) in flowers were higher than in leaves. Antinutritional compounds total free phenolics and tannins were also estimated. The amount of nutrition in M. vaginalis indicates that it can be used as a nutritional food supplement.

This study was analyzed and investigated to evaluate ecological distribution of medicinal plants in Miho Stream of Korea. Totality 463 taxa of vascular plants were appeared in lower part of Miho Stream. Medicinal plants were distributed 253 taxa, which were 54.6% of the total vascular plants appeared. Medicinal plants of official drug compendium(Korean pharmacopoeia) were 85 taxa. Medicinal plants were distributed most of the forest area, and followed field surrounding, stream surrounding and paddy surrounding respectively. The distribution of life form hemicryptophyte was the most frequent. Plant community of appearing area of medicinal plants was classified into Salix koreensis, Phragmites japonica, Echinochloa crusgalli, Artemisia selengensis, Miscanthus sacchariflorus, Setaria faberii, Panicum dichotomiflorum, Bidens frondosa, Humulus japonicus, Monochoria vaginalis var. plantaginea, Eleocharis kuroguwai, Erigeron acris, Pinus densiflora, Pinus rigida, Quercus acutissima, Quercus serrata, Robinia pseudoacacia and Castanea crenata community. Medicinal plants in plant communities that occur frequently were Humulus japonicus, Corylus heterophylla and Liriope spicata.

Monochoria vaginalis var. plantaginea (Pontederiaceae) is one of the most problematic weed in the rice field in Korea. Tanysphyrus (Tanysphyroides) major was selected as a potential biological control agent for M. vaginalis. Continuous rearing of T. (T.) major was carried out from 2006 to 2007, and its morphological characteristics and ecological characteristics were investigated. This species has a single generation per year, over-wintering as an adult stage. The emergence of adults starts in later June and last until September. These observations indicate that T. (T.) major takes 22±0.7 days to develop from egg to adulthood. Host specificity test showed that finally selected this species was suitable candidates for the biological control of M. vaginalis var. plantaginea since it showed negative host specificity against major 60 test crops.

Monochoria vaginalis var. angustifolia (Pontederiaceae) was newly found in a furrow in Imha-ri, Boeun-gun, Chungcheongbuk-do for the first time in Korea. This taxon is distinguished from the other species of the genus Monochoria in Korea by having the smallest plant height, very narrow lanceolate leaves, a cuneate leaf base, and raceme with 1 to 2 flowers. A local name was newly given, 'Ga-neun-moul-dal-ge-bi' for the species. The morphological characteristics and illustrations of the taxon as well as photographs at the habitat are aprovided with a taxonomic key to the species of Monochoria in Korea.

All living organisms spontaneously generate ultraweak photon emissions, which originate from biochemical reactions in cells. Current research uses the ultraweak photon emission from organisms as a novel indicator in nondestructive analyses of an organisms living state. This study indicates that ultraweak photon emissions from Monochoria vaginalis are different between resistant biotypes (R) to sulfonylurea (SU) and susceptible biotypes (S). In SU-R biotypes, distinct increases in photon emissions were observed, but there was little increase in SU-S biotypes. In addition, photon emissions from the resistant biotypes of M. vaginalis were suppressed by treatment with P450 inhibitors. This suggests that cytochrome P450 monooxygenase, which plays a crucial role in the metabolic detoxification of SUs, could be associated with the generation of ultraweak photon emissions. Ultraweak photon emissions have a potential use in a novel diagnosis system as an indicator in a nondestructive testing of weeds resistant to SUs.

Soil and water contaminated with arsenic (As) pose a major environmental and human health problem in Bangladesh. Phytoremediation, a plant-based technology, may provide an economically viable solution for remediating the As-polluted sites. The use of indigenous plants with a high tolerance and accumulation capacity for As may be a very convenient approach for phytoremediation. To assess the potential of native plant species for phytoremediation, plant and soil samples were collected from four As-contaminated (groundwater) districts in Bangladesh. The main criteria used for selecting plants for phytoremediation were high bioconcentration factors (BCFs) and translocation factors (TFs) of As. From the results of a screening of 49 plant species belonging to 29 families, only one species of fern (Dryopteris filix-mas), three herbs (Blumea lacera, Mikania cordata, and Ageratum conyzoides), and two shrubs (Clerodendrum trichotomum and Ricinus communis) were found to be suitable for phytoremediation. Arsenic bioconcentration and translocation factors > 1 suggest that these plants are As-tolerant accumulators with potential use in phytoextraction. Three floating plants (Eichhornia crassipes, Spirodela polyrhiza, and Azolla pinnata) and a common wetland weed (Monochoria vaginalis) also showed high BCF and TF values; therefore, these plants may be promising candidates for cleaningup As-contaminated surface water and wetland areas. The BCF of Oryza sativa, obtained from As-contaminated districts was > 1, which highlights possible food-chain transfer issues for As-contaminated areas in Bangladesh.

Although theoretical models predict low allocation to attractive structures with increased selfing in animal-pollinated plants, empirical measurement of the reproductive costs and benefits is complicated. Here, floral sex allocation was compared in two nectarless heterandrous species with different mating systems: Monochoria korsakowii (Pontederiaceae), which has moderate outcrossing rates, and Monochoria vaginalis, a predominant selfer. In both species, mirror-image flowers have one large dark-purple anther and five small yellow anthers. Experimental evidence is provided for functional differences between the two sets of anthers using data on pollinator visitation, pollen removal and deposition, and seed set after hand pollinations. Flower manipulations in bee-pollinated M. korsakowii demonstrated different functions of the two sets of anthers: the yellow (feeding) anthers function to attract pollinators, but have similar pollen performance to the purple (pollinating) anthers. Furthermore, a disproportional reduction in pollen production of the feeding anthers in the selfing species was found. This differential allocation between feeding and pollinating anthers in heterandrous species has not been recognized before. The finding of reduced allocation to attractive structures with an increase in the rate of self-fertilization supports the theory of sex allocation.

コナギのスルホニルウレア系除草剤（SU剤）抵抗性生物型がこれまで顕在化していない静岡県において，この抵抗性生物型の発生の有無を調査した。その結果，静岡県東部から西部地域にかけて抵抗性生物型が広く発生していることが明らかとなった。認められた抵抗性生物型は，すべてALS1あるいはALS3のPro197部位に変異が認められたが，そのうち2地域からのSU剤抵抗性生物型は，コナギではこれまで報告のないプロリンからトレオニンへのアミノ酸置換であった。抵抗性生物型が採集された伊豆地域では，1km以内の距離にある異なる水田で異なるアミノ酸置換が認められたことから，抵抗性生物型は，それぞれの地域で独立して起源したと考えられた。この結果から，コナギの残草が顕在化していない水田においても抵抗性生物型が発生していることが明らかとなった。

Summary Passion fruit (Passiflora edulis) is grown in the tropics for its edible fruits and for its many ethno-pharmacologic and pharmacological properties. Our study revealed that the plant contains a strong allelopathic potential. In a bioassay, aqueous extracts of P. edulis strongly suppressed germination and growth of lettuce, radish and two major paddy rice weeds, Echinochloa crusgalli and Monochoria vaginalis. In glasshouse and field experiments, P. edulis also strongly inhibited the growth of paddy rice weeds. Application of 2 t ha−1 dry plant material of P. edulis reduced weed biomass by 70% and increased rice yield by 35% compared with the unweeded control. Ten newly identified substances in P. edulis extracts, including coumarin, long-chain fatty acids and lactones, may be responsible for the inhibitory activity of P. edulis. Coumarin and the lactones showed greater inhibition of germination and growth of E. crusgalli than the fatty acids. The authors suggest that P. edulis may be used as a natural herbicide to reduce the dependency on synthetic herbicides.

Mirror-image flowers (enantiostyly) have long been considered a mechanism to promote cross-pollination between flowers of alternate stylar orientation. However, in monomorphic enantiostyly, the occurrence of both left- and right-styled flowers on the same individual plant might appear to promote geitonogamy rather than outcrossing relative to the condition of dimorphic enantiostyly. We investigated daily floral display during the flowering season in two experimental populations of monomorphic enantiostylous species, Monochoria korsakowii and Monochoria vaginalis (Pontederiaceae) to assess the potential effects of floral display on geitonogamous pollination. The left- and right-styled flowers exhibited a 1:1 ratio both within individuals and populations. In M. korsakowii and M. vaginalis, 86.0% and 71.3% daily floral displays involved fewer than three flowers thus reducing the likelihood of geitonogamy. Moreover, daily displays often involved one floral form and mixed-formed with unequal ratios of left- and right-styled flowers also reducing opportunities for geitonogamy. Therefore variation in daily floral display in these two Monochoria species suggests that the impact of monomorphic enantiostyly in promoting geitonogamy will be reduced by small display sizes, or through simulating dimorphic enantiostyly.

Ageratum conyzoides L. (billy goat weed), showed strong inhibition on Raphanus sativus L. (radish) germination and growth in a bioassay. The leaves exhibited a greater suppression than the stem and root. The leaves of A. conyzoides applied at 2 t ha � 1 reduced about 70% of the growth of Echinochloa crus-galli var. formosensis Ohwi. and completely inhibited emergence of Monochoria vaginalis (Burm.f. Persilvar. plantaginea Solms.) and Aeschynomene indica L. in calcareous soil condition. Application of A. conyzoides leaves at 2 t ha � 1 in a paddy field 2 d after transplanting caused about 75% paddy weed reduction and increased yield by 14% compared with a herbicide treatment. Three phenolic compounds were identified in the leaves, stem and root including gallic acid, coumalic acid, and protocatechuic acid, and catechin was found only in the stem. p-hydroxybenzoic acid was detected in both A. conyzoides leaves and stem. Three additional putative allelochemicals were found in the leaves consisting of p-coumaric acid, sinapic acid, and benzoic acid. The greater number of growth inhibitors found in the leaves might result in the stronger inhibitory activity than the stem and root. A. conyzoides might be a naturalherbicide for weed controlin paddy fields to reduce the dependence on synthetic herbicides. r 2004 Elsevier Ltd. All rights reserved.

Two new compounds have been isolated from the whole plant of Monochoria vaginalis and characterized as: (10Z)-1-(2,6-dihydroxyphenyl)octadec-10-en-1-one (1) (20R, 24R)-campest-5-ene-3β, 4β-diol (2) together with nine known ones. The structures of these compounds were elucidated on the basis of spectral data and chemical evidence.

The development of juvenile seedlings of Monochoria vaginalis (Burm.f.) Kunth var. vaginalis concerning its hypocotyl hairs was investigated morphologically at establishing on 1 mm flooded paddy soil surface and in distilled water. Prime germination of M. vaginalis seeds sown after breaking dormancy was found on a flooded paddy soil surface and in distilled water at 6 h after seeding (HAS). Elongation of cotyledons and hypocotyl hairs of juvenile seedlings appeared at 12 HAS on a paddy soil surface, while lengths of hypocotyl hairs were almost the same as longitudinal length of seeds and cotyledons formed arch on the soil surface at 18 HAS. Seminal roots began to emerge and seedlings adhered completely to the soil surface by hypocotyl hairs, which were longer in length than seminal roots at 24 HAS. At 36 HAS, seed chaffs completely separated from the soil surface, as cotyledons had elongated from standing up, and lengths of seminal roots became longer than those of hypocotyl hairs. Emergence of first leaves and crown roots was simultaneously observed at 48 HAS. Elongations of cotyledons, seminal roots and hypocotyl hairs were completely terminated at 96, 120 HAS and 120 HAS respectively, and the elongation of 2 to 4 crown roots was observed at 120 HAS. Almost half the number of hypocotyl hairs putrefied at 240 HAS. In distilled water, hypocotyl hairs elongated to their longest at 36 HAS earlier than those on a paddy soil surface. It was concluded that hypocotyl hairs supported a strongly physical mechanism in establishing M. vaginalis seedlings on a paddy soil surface.

イネ籾100gあるいは籾殻20gを1000mlの蒸留水に浸漬し, 5℃暗条件下で約48時間おいてろ過した水抽出液に等量の蒸留水を加え, この希釈液を用いて, 0.5%の寒天培地を作成した。次いで寒天培地表面から約1mmの深さにコナギ種子を置床し, 培養した。コナギ種子の発芽率は, 20～25℃で最も高く93.3%となり, 種子根長は30℃で最も長くなった。コナギ種子の発芽および幼植物の成長に対する促進効果は, 籾だけでなく籾殻の水抽出液でもみられ, 籾殻の水抽出液を用いた寒天培地でもコナギの培養が可能であった。次に本方法を適用して, 日本型およびインド型イネの計43品種の籾の水抽出液を用いた寒天培地を作成し, コナギの置床後7日目の成長を比較調査した。イネ籾の水抽出液無添加の寒天培地ではコナギの発芽率は13.3%であったが, イネ籾の水抽出液を添加した寒天培地ではコナギの発芽率は78.3%～96.7%であった。コナギの種子根と子葉の伸長は, 一部のイネ品種を除き籾の水抽出液を添加した寒天培地では促進された。これらの促進効果は, イネ品種間で差異が認められた。これらの結果から, 本培養法がコナギを用いた生物検定法として有効であることが分かった。

除草剤の処理がコナギ幼植物の生育, 特に胚軸毛の形成およびその水田土壌面への固着力に及ぼす影響を知るために, ベンスルフロンメチル〔methyl α-[[3-(4,6-dimethoxypyrimidin-2-yl) ureido] sulfonyl]-o-toluate〕およびベンチオカーブ [S-(4-chlorobenzyl) diethylthiocarbamate] を処理し, 播種後1, 3および5日目におけるコナギ幼植物の形態, 固着力および胚軸毛の形成様相について調査した。ベンスルフロンメチルは, 1ppm処理区では幼植物の成長停止と土面への定着不良を生じたが, 0.01ppmより低濃度の処理区では成長抑制は認められず, 0.0001ppm処理区では種子根長や全冠根長が無処理区より長くなった。胚軸毛については, どの処理区も個体当たりの本数はおおよそ100本で, 最長毛長は無処理区とほぼ同程度の長さであった。ベンチオカーブは, 1ppm処理区ではコナギ幼植物の成長停止および土面への定着不良を生じたが, 低濃度になるにつれて, 幼植物に対する成長抑制は小さくなり, 0.0001ppm処理区では無処理区の幼植物の成長とほぼ同程度であった。また個体当たりの胚軸毛の本数については, どの処理区においても無処理区とほぼ同様であったが, 高濃度になるにつれて最長毛長は短くなった。コナギ幼植物の土面への固着力は, ベンスルフロンメチルの0.001ppmあるいは0.0001ppm処理区では, 播種後3日目は無処理区と同程度であったが, 播種後5日目には無処理区の2倍近くに増大した。一方, ベンチオカーブでは, 播種後5日目までどの処理区においても無処理区より固着力が小さかった。

Studies on allelopathic rice, which inhibits the germination and development of weeds such as barnyardgrass (Echinochloa spp.) and ducksalad [Heteranthera limosa (Sw.) Wild.], have been strongly conducted in the USA, the Philippines, Japan, Korea, and other countries since the 1980s. Weed-suppressing rice plants can compete with weeds for light and mineral nutrients by their rapid and thick growth characteristics, and probably also by their allelopathic effects. It was suggested that allelopathic properties were inherited from parents. Different screening methods for finding allelopathic rice simply and rapidly have been proposed. In contrast, stimulative allelopathy in rice, which promotes germination of the dormant and dormancy-awakened seeds of Monochoria vaginalis (Burm. f.) Kunth var. vaginalis, has been investigated by the authors since the 1990s. Rice seeds promoted the germination in the dark and in light under submerged conditions. Our experiments suggested that rice seeds, hulls, plants and straw contain stimulative substance(s) that promote seed germination of M. vaginalis.

Summary This study investigates the seasonal variation of germination ability of buried seeds of Monochoria vaginalis (Burm.f.) Presl var. plantaginea Solms. The field-collected seeds were buried in a flooded or an upland field and then exhumed monthly. The exhumed seeds were germinated under four temperature regimes. The seeds exhumed from the flooded soil were dormant at the beginning of burial and proceeded into a conditional dormancy/non-dormancy/conditional dormancy cycle throughout the remaining period of the experiment. The seeds exhumed monthly from the non-flooded soil exhibited an annual dormant cycle, which is dormancy/conditional dormancy/non-dormancy/conditional dormancy/dormancy. At day and night temperatures of 25/20 ∞C, the exhumed seeds from both the flooded and the upland soil resembled each other in terms of seasonal variation of the germination percentage. In September and October, more seeds exhumed from upland soil failed to germinate under higher temperature than from flooded soil. Strictly avoiding exposure to light during seed exhuming and seed testing prevented the seeds from germinating. A short exposure of the exhumed seeds to light during preparation promoted dark germination when the seeds were at the non-dormant stage. The potential implications of our results for weed management strategies in rice production are discussed.

The host range of Eccritotarsus catarinensis was determined using 33 plant species to assess the risk of using this insect, a native of South America, for the classical biological control of waterhyacinth ( Eichhornia crassipes ) in Australia and Papua New Guinea. The results, in conjunction with the results of Hill et al. (1999) who tested 67 species (mostly South African), strongly suggest that E. catarinensis is restricted to the Pontederiaceae, a family of aquatic plants. All five species of Pontederiaceae in the Australian testing, E. crassipes, Pontederia cordata, Monochoria vaginalis, M. cyanea, and M. australasica, were suitable for insect development. Colonies persisted for at least four generations on E. crassipes, P. cordata, and M. vaginalis. Two-way choice and multiple-choice preference trials were conducted and discussed. E. catarinensis did not exhibit a clear preference for waterhyacinth over other Pontederiaceae in these trials. Most oviposition occurred into the upper surface of the lamina during laboratory testing despite observations that the underside was preferred in the field. Although not considered suitable for release in Australia, this insect may be useful in other countries where more serious waterhyacinth problems occur and where M. vaginalis is a serious weed, such as in Southeast Asia.

Laboratory experiments were conducted to examine the allelopathic potentials of rice plants (Oryza sativa L.) on seed germination and radicle elongation of Monochoria vaginalis (Burm. f.) Presl var. plantaginea (Roxb.) Solms-Laubat. To compare the relative allelopathic potentials of rice plants at different growth stages, aqueous extracts of dried tissues were obtained from the seeds, husks, and seedlings harvested 10, 20, 40 and 120 days after seeding. When M. vaginalis seeds were incubated in solutions containing aqueous extracts, significant increases in the germination rate were observed for all the aqueous extracts except for the extract of 10 d-old shoots at higher dosages. When partitioned with ethyl acetate, the germination-promoter(s) in the aqueous extracts remained in the aqueous phase while some inhibitors were extracted with ethyl acetate. In contrast, aqueous shoot extracts added to the incubation media at the same dosage for promotion of seed germination inhibited radicle elongation of M. vaginalis, indicating that the sensitivity of the weed varies between these two growth stages.

Laboratory experiments were performed to evaluate the effect of germinating rice seeds (Oryza sativa L.) on seed germination of Monochoria vaginalis (Burm. f.) Presl var. plantaginea (Roxb.) Solms-Laub (here-after Monochoria). Rice seeds (cv. Tsukinohikari) promoted the seed germination of Monochoria at all incubating temperatures except 31°C, an optimal temperature for germination of Monochoria in the light. In darkness, although under non-inductive conditions for germination of Monochoria, rice seeds dramatically induced the seed germination at all incubating temperatures. Such stimulative effects of rice seeds were observed with both nondormant and dormant seeds of Monochoria harvested in different years. Furthermore, seeds of all 12 rice cultivars tested in the experiments exhibited a stimulative effect on the seed germination of Monochoria. Ethylene and carbon dioxide released from rice seeds and seedlings seemed to be involved in the promotion of this germination. Stimulative allelochemical (s) in rice seeds or seedlings may also promote the seed germination of Monochoria.

The research were carried out to study the potency of Salvinia molesta D.S. Mitchell (Kiambang), Limnocharis flava (L.) Buchenau (Genjer) and Monochoria vaginalis (Burm.f.) Presl (Eceng) for Hg phytoextraction on paddy field contaminated with Hg from illegal mining. The plants were grown on contaminated media from paddy field in Pongkor (68.269 ppm Hg) added by NPK fertilizer (0, 3 and 6 g/pot) and ammonium thiosulphate chelating agent (0, 20 ppm). The result showed that the growth of kiambang,eceng, genjer and padi are significantly different. Chelating agent did not significantly affect the plant growth, meanwhile fertilizer significantly affected the plant growth. Thetreatments resulted in different Hg concentration in the plants. Fertilizer increased plant biomass and so plant Hg content since Hg contents is a function of total biomass and Hg concentration. It can be concluded that based on the criteria of accumulator plant,kiambang is the most potentially Hg accumulator followed by genjer and eceng.Key words: Phytoextraction, Hg, Salvinia molesta, Limnocharis flava, Monochoriavaginalis

Monochoria vaginalis s.l. is an annual aquatic herb belonging to the family Pontederiaceae and having an extensive distribution in tropical and subtropical Asia, Africa, and Australia. The taxon is extremely variable and morphologically complicated. In Thailand, it is recognized as a monotypic species but displays great variations not only in vegetative but also in reproductive structures. Because of these variations, its taxonomic status and species boundary remain uncertain. Morphological investigation was conducted on 244 living specimens of M. vaginalis s.l. covering the current distribution in Thailand together with a detailed observation of 80 herbarium specimens. The holotype of M. vaginalis var. angustifolia and its related specimens were also re-examined. The present study points out that M. vaginalis can be separated into 2 morphological forms: based on leaf shapes, leaf base, number of flowers/raceme, flower arrangements, seed shapes and its longitudinal ridges. Furthermore, the living specimens were used for two cluster and one canonical discriminant analyses in a phenetic study to collect additional data for new taxonomic insights. A total of 22 quantitative and 12 qualitative characters were employed. The first cluster analysis using only quantitative characters and the second cluster analysis using both quantitative and qualitative characters displayed the same trends. The specimens separated into two distinct groups. Likewise, canonical discriminant analysis also indicated that there were two groups. The two groups can be distinguished by the petiole length of floral-leaf and peduncle length. In conclusion, the results from morphological and phenetic studies support the segregation of M. vaginalis s.l. in Thailand into two taxa.

Jengkerik Anaxipha longipennis Serville (Orthoptera: Gryllidae) adalah salah satu predator generalis di habitat sawah yang menyukai telur pelipat daun padi dan serangga-serangga kecil lain seperti wereng-wereng padi. Jengkerik betina menyisipkan telurnya pada batang atau pelepah daun padi dan gulma-gulma di habitat sawah. Tempat bertelur yang disukai akan menjamin keberlanjutan keberadaan jengkerik di habitat sawah. Pada penelitian ini telah dicoba untuk mengetahui jenis gulma yang dipilih sebagai tempat bertelur selain pada tanaman padi. Tujuh belas species gulma dan padi telah dipaparkan pada 5 pasang jengkerik sebagai tempat bertelur pada suatu percobaan memilih secara bebas. Sembilan spesies gulma telah dipilih sebagai tempat bertelur oleh A. longipennis selain padi. Telur diletakkan paling banyak pada padi dan berturut-turut diikuti pada Monochoria vaginalis, Cyperus rotundus, C. iria, Echinochloa colonum, E. crusgalli, Eleusine indica, Fimbristylis miliacea, Imperata cylindrica, dan Limnocharis flava. Sedangkan Alternanthera sessilis, Ludwigia adscen-dens, Commelina diffusa, Leersia hexandra, Leptochloa chinensis, P. repens, Ageratum conyzoides dan Sonchus arvensis tidak dipilih oleh A. longipennis sebagai tempat bertelur.

Summary: Resume: Zusammenfassung Chemical and non-chemical or cultural approaches for the control of Scirpus maritimus L. (bulrush) and of annual weeds in lowland rice were examined in the field. Herbicides such as bentazon [3-isopropyl-1H-H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] and 2,4-D [2,4-dichlorophenoxy)acetic acid] effectively controlled S. maritimus but not the annual grasses [Echinochloa glabrescens Munro ex Hook. f. and Echinochloa crus-galli ssp. hispidula [(Retz.) Honda] when applied at the six- to eight-leaf stage 20–28 days after transplanting or seeding rice). S. maritimus was not adequately controlled when the herbicides were applied pre- or early post-emergence. A granular formulation of bensulfuron-methyl [(methy1–2-[[(4,6-dimethoxypirimidin-2-yl)aminosulfonylmethyl]benzoate)] applied 6 or 8 days after transplanting or seeding (two- to four-leaf stage of the weed) effectively controlled S. maritimus and the annuals E. glabrescens, E. crus-galli ssp. hispidula, and Monochoria vaginalis, Presl. (Burm. f.) S. maritimus stand was drastically reduced by shifting land preparation back and forth from wet to dry. Neither tillage intensity nor use of intermediate-statured modern rice cultivars affected the weed stand. La lutte chimique et culturelle contre le scirpe (Scirpus maritimus L.) et les mauvaises herbes annuelles en culture de riz (Oryza sativa L.) Des possibilities chimiques et culturelles dans la lutte contre Scirpus maritimus L. (le scirpe) et les mauvaises herbes annuelles en culture de riz ont fait l'objet d'une etude sur le terrain. Appliques au stade 6- a 8-feuilles des graminees annuelles, Echinochloa glabrescens Munro ex Hook. f. et Echinochloa crus-galli ssp. hispidula [(Retz) Honda] (20 a 28 jours apres le repiquage ou le semis du riz), les herbicides, tel le bentazone [isopropyl-3 1H 3H-benzothiadazine-2,1,3 one-4 dioxyde-2,2] et le 2,4-D [acide 2,4-dichlorophenoxyacetique] ont permis une lutte efficace contre S. maritimus mais pas contre les graminees. La maitrise de S. maritimusetait insuffisante quand les traitements herbicides ont ete appliques en prelevee ou en postlevee precoce. Une forme granulee de bensulfuron-methyl, appliquee 6 ou 8 jours apres le repiquage ou le semis (stade deux- a quatre-feuilles de l'adventice) a permis une lutte efficace contre S. maritimus ainsi que les adventices annuelles E. glabrescens, E. crus-galli ssp. hispidula et Monochoria vaginalis (Burm. f.) Presl. Une reduction dramatique dans le peuplement de S. maritimus a suivi l'emploi alterne de techniques humides el seches dans la preparation du sol. Ni l'intensite du labourage ni l'emploi de varietes de riz modernes de hauteur moyenne n'ont eu d'influence sur l'enherbement. Bekampfung der Strand-Simse (Scirpus maritimus L.) und einjahriger Unkrauter in Nass-Reis (Oryza saliva L.) mit chemischen und Kulturmethoden Mit Herbiziden wie Bentazon und 2,4-D konnte Scirpus maritimus, nicht aber die einjahrigen Graser Echinochloa glabrescens Munro ex Hook, und Echinochloa crus-galli ssp. hispidula (Retz.) Honda bekampft werden, wenn sie im 6- bis 8-Blatl-Stadium (20 bis 28 Tage nach dem Pflanzen oder der Saat des Reises) behandelt wurde. Die Bekampfung war aber unzureichend, wenn die Herbizide vor oder kurz nach der Keimung ausgebracht wurden. Mit bensulfuron-methyl Granutat 6 oder 8 Tage nach dem Pflanzen oder der Saat (2- bis 4-Blatt-Stadium der Unkrauter) konnten Scirpus maritimus und Echinochloa glabrescens sowie E. crus-galli ssp. hispidula und Monochoria raginalis (Burm. f.) Presl. Bekampft werden. Die Verschiebung der Bodenbearbeitung von nass nach troeken verringerte die Verunkrautung mit Scirpus maritimus erheblieh. Der Unkrautbestand wurde weder durch verschiedene Intensitat der Bodenbearbeitung noch durch die neuen mittellangen Reissorten herabgesetzt.

The cytology of two taxa of Pontederiaceae is reported, viz. M. vaginalis (n=26, 2n=52) and M. vaginalis var. plantaginea (n=12, 2n=24). The chromosome number of the latter taxon is a new count. The karyotype of M. vaginalis consisted of three pairs of M type, 7m type, 12sm type and 4 st type with 2B type of asymmetry. In M. vaginalis var. plantaginea, the karyotype consisted of 2 pairs of M type, 5m type, 4sm type and one st type with 2B type of asymmetry. These two taxa show the basic numbers 13 and 6 respectively. They are morphologically almost distinct with conspicuous differences in leaf-shape and plant size. The similarity in chromosome morphology shows their colse relationship. It is suggested that M. vaginalis is an allotetraploid of M. vaginalis var. plantaginea and M. hastaefolia.

1. The intensity of growth inhibition caused by 2, 4-D application, such as decrease in number of living leaves, degree of leaf greenness, and morphological injury were in the following order: Monochoria vaginalis>Rotala indica, Ammannia multiflora>Cyperus difformis>Echinochloa crus-galli.2. Evolution of ethylene caused by 2, 4-D was greater in broad-leaf weeds, M. vaginalis, R. indica and A. multiflora than C. difformis, E. crus-galli and rice plants.3. The growth inhibition and morphological injury caused by ethylene were less than caused by 2, 4-D. However, both inhibition and injury caused by 2, 4-D were increased by the addition, regardless of the kind of weed.4. A part of the growth inhibition and morphological injury caused by 2, 4-D in broad-leaf weeds is assumed to be caused by ethylene evolution by the chemical stress.

Summary Experiments were carried out in Indonesia to see whether weeds of lowland rice fields could be managed by manipulation of the water table and what factors affected germination of their seeds. It was found that seeds of two Scirpus spp. germinated when buried in anaerobic soil but not when on the surface, whereas seeds of two Echinochloa spp. germinated when on the surface of both aerobic and anaerobic soils but when buried germinated only in aerobic soil. The germination of weed seeds was affected to differing extents by submergence in water at depths down to 20 cm. Germination of Fimbristylis littoralis seeds was greatly reduced and of Ludwigia hyssopifolia was completely inhibited by submergence. Conversely, germination of Monochoria vaginalis seeds was virtually unaffected. It is suggested that the effect of submergence on germination of some species may be due to their reaction to the amplitude of temperature fluctuation. The germination and emergence of seedlings under water were greatly reduced by a cover of Salvinia molesta. The practical importance of these findings is discussed. Resume Facteurs affectant la germination et la croissance de plantules de mauvaises herbes dans les riz de bus fonds en Indonesie Des experimentations ont ete conduites en Indonesie pour etudier la possibilite d'utiliser le niveau d'eau pour lutter contre les mauvaises herbes dans les rizieres de bas fonds et pour voir quels etaient les facteurs influenânt la germination de leurs semences. II a ete mis en evidence la possibilite de germination de graines de deux especes de Scirpus spp. en conditions d'enfouissement anaerobies. En revanche, la germination n'a pas lieu lorsqu'elles sont a la surface du sol; au contraire, les semences de deux especes d'Echinochloa spp. peuvent germer a la surface du sol en conditions aerobies ou anaerobies, mais si elles sont enfouies elles ne germent qu'en conditions aerobies. La germination de graines de mauvaises herbes est influencee par la submersion dans plus de 20 cm d'eau. La germination de Fimbristylis littoralis est grandement diminuee et celle de Ludwigia hyssopifolia est completement inhibee par la submersion. En revanche, la germination de Monochoria vaginalis n'est pas modifiee. L'hypothese qui est avancee est que l'effet de la submersion sur la germination de quelques especes peut etre due aux modifications de la temperature. La germination et la levee de plantules dans l'eau est notablement reduite par une couverture de Salvinia molesta. L'importance pratique de ces observations est discutee. Zusammenfassung Faktoren, die die Keimung von Unkrautsamen und das Wuchstum junger Unkrauter im Wosserreis in Indonesien beeinflussen In Indonesien wurden Versuche im Nassreisbau angestellt um zu erfahren, inwieweit durch Veranderung des Wasserniveaus die Verunkrautung reguliert werden kann und welche Faktoren die Keimung der Unkrautsamen beeinflussen. Es wurde festgestellt, dass Samen von zwei Scirpus spp. in anaerobem Boden keimten; sie keimten aber nicht, wenn sie auf der Bodenoberflache waren. Echinochloa spp. hingegen keimten auf der Oberflache von aeroben und anaeroben Boden; befanden sich aber die Samen im Boden, keimten sie nur im aeroben Boden. Die Keimung wurde durch Uberstauen mit Wasser (bis zu 20 cm) unterschiedlich stark beeinflusst. Durch Uberstau wurde die Keimung von Fimbristylis littoralis stark vermindert und bei Ludwigia hyssopifolia war die Keimung votlig gehemmt. Im Gegensatz hierzu, blieb die Kei-mung von Monochoria vaginatis praktisch un-beeinflusst. Es wird angenommen, dass die Wir-kung des Uberstaus auf die Reaktion der Samen auf den veranderten Temperaturverlauf zuriick-zuflihren ist. Die Keimung und das Auflaufen unter Wasser war stark reduziert, wenn die Wasseroberflache mit Salvinia molesta bedeckt war. Die praktische Bedeutung der Ergebnisse wird diskutiert.

Two distinct morphological types (types I and II) each of M. hastata and M. vaginalis having a different and stable chromosome number in each type were recorded. The chromosome numbers in these plant types were 2n=28 in M. hastata-type I and 2n=80 in type II and 2n=24 in M. vaginalis-type I and 2n=52 in type II in both RTCs and PMCs. Based on the morphological and cytological observations, a hypothesis has been proposed in which 52 chromosome plants (M. vaginalis-type II) are suggested to be an allotetraploid between 2n=28 and 2n=24 chromosome plants and 2n=80 chromosome plants as an autoallohexaploid between 2n=52 and 2n=28 chromosome plants and that they may be considered as new species.

Summary Nitrogen-fixing bacteria have been isolated from Amorphophallus campanulatus, Colocasia esculenta, Ipomea batata, and Monochoria vaginalis. The characteristics of these organisms were studied. It was found that many bacteria are facultative aerobes. The nitrogen-fixing capacity varied from 0.89 to 17.17 mg per g of sugar within a fortnight in Jensen's medium under aerobic conditions and from 0.21 to 14.7 mg under anaerobic conditions.

Although cultivated rice ( Oryza sativa L.) has been grown in the United States since the seventeenth century, it was not until 1912 that commercial rice production was practised in California. At present, approximately one quarter of the total annual U.S. rice crop is produced in the Central Valley of California. Due to the continually flooded conditions that prevail in Californian rice fields, the weed flora is highly specialised and is composed of some 62 species of aquatic vascular plants. The flora is unusual among crop weed floras of California in that it contains a substantial proportion (ca. two thirds) of native species. This is probably a result of the similarity in ecological conditions between rice fields and the original wetland habitats of the Central Valley that they replaced. Seventeen of the 20 alien species in the weed flora are of Old World origin and several ( Cyperus difformis L., Dopatrium junceum (Roxb.) Ham., Echinochloa crusgalli (L.) Beauv., Scirpus mucronatus L., Monochoria vaginalis (Burm. f.) Presl, Oryza rufipogon Griff., Ottelia alismoides (L.) Pers. and Rotala indica (Willd.) Koehne are widely distributed and well-documented weeds associated with rice. It is proposed that the most likely methody by which these aliens have been introduced to California is as seed contaminants of imported rice stocks. The small seed size, annual life form and autogamous breeding systems of the majority of these species probably aid in their dispersal, establishment and colonization of rice fields. A survey of 70 rice fields distributed throughout the rice-growing areas of the state indicated that the annuals Sagittaria montevidensis Cham. and Schlecht. ssp. calycina (Engelm.) Bogin., Ammannia coccinea Rottb., Bacopa rotundifolia (Michx.) Wettst. and taxa in the Echinochloa crus-galli complex are the most abundant and widely distributed rice weeds in California.

In the present paper vascular anatomy of the flower of all the three Indian species of Pontederiaceae,viz., Monochoria hastaefolia Presl,Monochoria vaginalis Presl andEichhornia crassipes Solms is described.

1. During the spring and summer of 1948, the synecological investigation was made by quadrate method on virgin soil, reclaimed land, rich farmland, and paddy-field at Kashii District (Fukuoka Prefecture). These places were composed of a strong acid soil originated from Tertiary. 2. Among these the following species grouped in (a) were abundant in strong acid soil and so might be called acid plants. While the species in (b) might be supposed as plants that were disagreeable with strong acidity of soil ; they were not as common on that soil though they were usually seen numerous in fertilized farm land as its indecator-plants: (a) Lespedeza striata H. A. Miscanthus sinensis Anderss. Melampyrum roseum Mxim. var. Japonicum Fr. etsav. Panicum sanginale L. Polygonum Blumei Meissn. Gnaphalium multiceps Wall. Alopecurus fubus Sm. Polygonum aviculare L. Monochoria vaginalis Presl. var. Plantaginea Solms. Lindernia angustifolia Wettst. Rotala indica var. Uliginosa. Eliocharis acicularis R. Br. (b) Eu phorbia pekinensis Rupr. Galium aparime L. Veronica polita Fr. Veronica peregrina L. Spirodela polyrhiza Schleid. Lemna paucicosta Hegelm 3. In order to quiken promote the maturing of the reclaimed land into rich farmland, cultivate of the following species as green manure or forage crop was advisable: Lespedeza striata H. et A. Panicum sanginale L. Arundinella anomala Steud. Pueraria Thumbergiana Benth. Cassia minoides L.