Weeds In Rice Fields Research Articles

Flora y vegetación de los arrozales de las provincias de Valencia y Tarragona

De los 49 táxones registrados (29 emergentes y 20 flotantes o sumergidos) 11 son exóticos introducidos, de los cuales los más importantes son Echinochloa oryzoides y E. oryzicolaen ambas zonas, además de Cyperus difformis y Echinochloa hispidula en Valencia, y el resto propios de la flora autóctona, predominando Scirpus maritimus, Alisma plantago-aquatica. Echinochloa crus-galli y Paspalum distichum como emergentes, Lemna minor y L. gibba como flotantes, Potamogeton nodosus, Zannichellia palustris y Najas minor como sumergidos y Chara vulgaris, Cladophora glomerata, Oedogonium capilliforme. Spirogyra spp., Pirhophora oedogonia e Hydrodictyon reticulatum como algas macroscópicas. Se analiza la evolución experimentada por la flora en los últimos años, además de estudiar las comunidades vegetales presentes y de indicar la importancia de las distintas clases fitosociológicas en su contribución a la flora arvense del cultivo.

Lowland Rice Field Weeds in Nueva Ecija, Philippines

Lowland Rice Field Weeds in Nueva Ecija, Philippines

Significance of temperature fluctuation and oxygen concentration for germination of the rice field weeds Fimbristylis littoralis and Scirpus juncoides.

A diurnally fluctuating temperature was found to be almost an absolute requirement for the germination of Fimbristylis littoralis and Scirpus juncoides. It is demonstrated that in f. littoralis sensitivity to the amplitude of temperature fluctuation can functuation as a depth sensing mechanism under water. This species did not germinate at all in the absence of oxygen. S. juncoides germinated best in anaerobic conditions and at low oxygen concentrations, but normal atmospheric concentrations inhibited germination. It is shown that this requirement for little or no oxygen together with the requirement for a fluctuating temperature cause the germination of S. juncoides to be restricted to the upper layers of waterlogged soil.

Rice Field Weeds of Mwea Irrigation Scheme, Kenya

Rice Field Weeds of Mwea Irrigation Scheme, Kenya

Germination of Echinochloa crus-galli (Barnyard Grass) Seeds under Anaerobic Conditions

Echinochloa crus-galli L. Beauv., a rice-field weed, can germinate and grow for extended periods of time in an anaerobic environment. Compared to pea, which does not germinate under anaerobiosis, the evolution of CO(2) in Echinochloa and rice is lower and the peak rate of CO(2) evolution is delayed when germinated without oxygen. The plants studied also differ with respect to their respiration ratio ([CO(2)] N(2)/[CO(2)] air) and metabolism used during the early stages of germination. Echinochloa does not increase its glycolytic rate under anaerobiosis, whereas pentose phosphate pathway activity appears to increase during the first 40 to 50 hours of germination.Based on its response to metabolic inhibitors (NaF, dinitrophenol, and malonate), anaerobic metabolism in Echinochloa proceeds primarily through glycolysis, with partial operation of the tricarboxylic acid cycle and little or no oxidative phosphorylation. Also, Echinochloa is sensitive to CN during aerobic germination, whereas rice appears to be able to shift to CN-insensitive electron transport. Finally, the effectiveness of cyanide and azide on inhibiting germination of Echinochloa in N(2), but not CO, suggests that cytochrome oxidase is not used to reoxidize pyridine nucleotides in the absence of oxygen. The possible existence of an alternate electron acceptor is discussed.

Factors affecting weed seed germination and seedling growth in lowland rice in Indonesia

SummaryExperiments 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 complétély 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.

Anaerobic Metabolism in Germinating Seeds of Echinochloa crus-galli (Barnyard Grass)

Echinochloa crus-galli, a problem weed in rice fields, has the rare ability to germinate and to grow in a totally oxygen-free environment. After 7 days growth in the light or dark under N(2), E. crus-galli var. oryzicola produces a 2- to 3-centimeter nonpigmented shoot.Ethanol, malate, and lactate were measured in seeds germinated under N(2) and air, and compared with changes in the activities of alcohol dehydrogenase, malate dehydrogenase, NADP-malic enzyme, and phosphoenolpyruvate carboxylase. During a 7-day time course, ethanol levels increased 661 micromoles per gram dry weight under N(2), with no increase under air. Alcohol dehydrogenase activity increased 5.5 micromoles per gram dry weight per minute in N(2) compared to 1.0 in air. Corresponding increases for lactate were 7.9 micromoles per gram dry weight under N(2) and 2.7 under air, and for malate, 5.3 micromoles per gram dry weight under N(2) and 0.4 under air.Although 85% of the ethanol produced by the seedlings was found in the external solution under N(2), the seeds still contained 90 times more ethanol under anaerobic conditions than under air. No phosphoenolpyruvate carboxykinase activity was detected and phosphoenolpyruvate carboxylase activity was 10 times less under N(2) than air. Malic enzyme activity increased 5-fold under anaerobic conditions, comparable to the change under aerobic conditions. Proposed adaptive mechanisms of flood-tolerant species to anaerobiosis are discussed.

Biological Control of Weeds in Rice Fields

Biological Control of Weeds in Rice Fields

Rice‐field rats of Lower sind: abundance, reproduction and diet

Data on the abundance, reproduction and diet of rice field rats were collected during three rice seasons. At rice harvest, Bandicota bengalensis nearly doubled its litter size and tripled its pregancy rate and greatly increased in abundance. Millardia meltada remained abundant and maintained a relatively high pregnacy rate over all stages of crop development. These differences corresponded to differences in diet. Before the onset of grain ripening, the diet of Millardia contained more high‐energy food (weed seeds, insects and scattered grain) while the diet of Millardia contained more high‐energy food (weed seeds, insects and scattered grain) while the diet of Bandicota contained primarily low‐energy food (rice stems and unidentified plant fibres); although both species ate principally rice at harvest. During most months, Nesokia indica was seldom caught above ground and ate mostly unidentified plant fibres. However, when grain ripened, Nesokia was caught on the surface and stomachs contained principally rice grain. Nesokia showed a lower pregnancy rate and smaller litter size, but apparently greater adult survival. They bred more often in the cooler months, during and after harvest.Some information on other topics is also presented, such as: sexual activity in males; substrate preference; relative adult longevity; the effect of excessive flooding of rice paddies; and the importance of underground rice caches, rice field weeds and swamp land to overwintering Bandicota. Estimates of the relative damage to the crop caused by each species at different stages of crop development were made by using data on rodent diet and abundanc

Rice-field weed communities in Ferrara Province (northern Italy)

Weed vegetation in rice-fields and the associated irrigation system in Ferrara Province (northern Italy) is described. The main weed communities are: Oryzeto-Cyperetum difformis, Spirodelo-Lemnetum minoris, Najadetum minoris, Potamogetono-Najadetum marinae and Ceratophylletum demersi. Fragmentary halophyte communities also occur on the canal sides. Data on climate and the environment are also reported.

Reaction of Some Common Weeds in Sri Lankan Rice Fields to Corticium sasakii

Reaction of Some Common Weeds in Sri Lankan Rice Fields to Corticium sasakii

Useful weeds of West Bengal rice fields

Out of 158 weed species collected from rice fields of Hooghly and Midnapore districts of West Bengal, 124 possess economic importance in one way or other. The various uses of these weeds may aid dealers in crude drugs, manufacturers of plant products, or persons interested in the beneficial aspects of plants.

Taxonomy and Natural History of Bacopa (Scrophulariaceae) in California

Three of California's four species of Bacopa are aliens. Bacopa rotundi- folia, a tetraploid, native to central United States, was first recorded for California in 1923 and has since become one of the commonest weeds in rice fields of the state. Californian populations of this species were named B. nobsiana in 1952. Bacopa repens, a neotropical diploid, has been known from a single California station since 1949; its range within the state has not increased in some 30 years. The third alien, the pantropical B. monnieri, has been found in California only recently. The native, B. eisenii, is tetraploid and has apparently invaded rice fields to a significant degree only recently. Taxonomic interpretation of these species has depended on a synthesis of field, experimental, and herbarium studies. The phytogeography and migratory histories of alien or immigrant

The Weight and Number of Seeds Produced by Rice-field Weeds

This paper presents data upon the seed production of rice-field weeds with special reference to the selection of specimens and cleaning of seed material to a definite plan. Notes on individual spec...

水田雑草の発生生態

水田雑草の発生生態

水田雑草の発生生態

水田雑草の発生生態

Selective Control of Weeds in Rice Fields

Selective Control of Weeds in Rice Fields

Responses of the rice plant to different formulations and methods of application of 2,4-D, MCP, and 2,4,5-T

The research described in this paper is a continuation of studies carried on during the past four years on the effects of the phenoxyacetic acid herbicides on rice and on weeds of rice fields. Injury to rice from 2,4-D sprays is fairly common; injury to surrounding sensitive crops from spray drift has also been experienced. The study described here compared the effects on rice and on weeds of 2,4-D, MCP, and 2,4,5-T applied to the water on rice cultures and applied as pellets to rice cultures. Applied to the water in aqueous solution, the most deleterious effects on the rice plants occurred when the rice seed was sown on top of the soil, as contrasted with being drilled into the soil; when the rice was treated at early stages of growth; when dosage was high; and when 2,4-D was used. Treatments with pellets caused intense aberrations in rice and aquatic weeds when plants were young, when dosage was high, and when 2,4-D was used. MCP was less injurious to rice, yet it killed aquatic weeds. The 2,4,5-T treatments were ineffective against weeds. At equivalent dosage, pellets were more selective than were aqueous solutions. Pellets effectively controlled aquatic weeds in rice without injury to the latter under greenhouse conditions.

水田雑草としての野生ビエに関する研究 : 第6報 発芽生理に関する研究

This paper gives the results of the physiological investigations on germination of the Japanese barnyard millet as a weed in rice field. The germination of this weed is irregular, slow and extend over long period. Some seed of the plant have germinated on 8th day after flowering. Afterripening of it will be completed in about 45-days. In normal storage of it, that is, natural drying and storage in desicator, ability of the germination was manitained for 2-3years. But hulled seed will quickly lose this ability in 2-3months. The greater specific gravity of the seeds increased the percentage of germination. Solutions of salts which were used in this experiments did not control the germination, expect K2CrO4 and K2Cr2O7. This seeds have not distinctively both light-germination or dark gemination habit. The optimum temperature of germination is from 30°C to 40°C and 10°C is too low for germination of the plant. Inconstant temperature was dffective as well as the seeds of other weeds. Germination of unhulled seeds was accelerated by sulphauric acid, physical and hulling treatments. Soil-coverings of 0.5 and 1cm have no dffect on the germination of the seeds, 3 and 5cm distinctly but those of over 7cm completely prohibited the germination of the seeds.

Eradication of Weeds in Rice Fields by Maans of Manuring-III. Effects of Line

Eradication of Weeds in Rice Fields by Maans of Manuring-III. Effects of Line