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T. D. Khanh M. I. Chung T. D. Xuan S. Tawata 《Journal of Agronomy and Crop Science》2005,191(3):172-184
Crop allelopathy may be useful to minimize serious problems in the present agricultural production such as environmental pollution, unsafe products, human health concerns, depletion of crop diversity, soil sickness and reduction of crop productivity. Several crops including alfalfa, buckwheat, maize, rice, rye, sorghum, sunflower, wheat, etc. are affected either by their own toxicity or phytotoxin exudates when their residues decompose in the soil, that show strong suppression on weed emergences. Allelopathic crops when used as cover crop, mulch, smother crops, green manures, or grown in rotational sequences are helpful in reducing noxious weeds and plant pathogen, improve soil quality and crop yield. Those crop plants, particularly the legumes, incorporated at 1–2 tons ha−1 (alfalfa, buckwheat, rice by-products), which can give weed reduction and increase of rice yield by 70 and 20 %, respectively, are suggested for use as natural herbicides. Allelochemicals from allelopathic crops may aid in the development of biological herbicides and pesticides. Cultivating a system with allelopathic crops plays an important role in the establishment of sustainable agriculture. The introduction of allelopathic traits from accessions with strong allelopathic potential to the target crops will enhance the efficacy of crop allelopathy in future agricultural production. 相似文献
2.
Upadhyay A Chompoo J Kishimoto W Makise T Tawata S 《Journal of agricultural and food chemistry》2011,59(7):2857-2862
AIDS and influenza are viral pandemics and remain one of the leading causes of human deaths worldwide. The increasing resistance of these diseases to synthetic drugs demands the search for novel compounds from plant-based sources. In this regard, the leaves and rhizomes of Alpinia zerumbet, a traditionally important economic plant in Okinawa, were investigated for activity against HIV-1 integrase (IN) and neuraminidase (NA). The aqueous extracts of leaves and rhizomes had IN inhibitory activity with IC(50) values of 30 and 188 μg/mL, whereas against NA they showed 50% inhibition at concentrations of 43 and 57 μg/mL, respectively. 5,6-Dehydrokawain (DK), dihydro-5,6-dehydrokawain (DDK), and 8(17),12-labdadiene-15,16-dial (labdadiene) were isolated from the rhizomes and were tested for enzyme inhibitions. DK and DDK strongly inhibited IN with IC(50) of 4.4 and 3.6 μg/mL, respectively. Against NA, DK, DDK, and labdadiene exhibited mixed type of inhibition with respective IC(50) values of 25.5, 24.6, and 36.6 μM and K(i) values ranging from 0.3 to 2.8 μM. It was found that DDK is a slow and time-dependent reversible inhibitor of NA, probably with a methoxy group as its functionally active site. These results suggest that alpinia could be used as a source of bioactive compounds against IN and NA and that DK and DDK may have possibilities in the design of drugs against these viral diseases. 相似文献
3.
Decomposition of Allelopathic Plants in Soil 总被引：1，自引：0，他引：1
T. D. Xuan S. Tawata T. D. Khanh I. M. Chung 《Journal of Agronomy and Crop Science》2005,191(3):162-171
Higher plants with strong allelopathic properties are commonly incorporated into soil for weed-control purposes. To understand the phytotoxic variation in the soil, which can be utilized for weed control through the use of allelopathic plants, the decomposition of alfalfa (Medicago sativa L. cv. Rasen) and kava (Piper methysticum L.) after soil amendment were evaluated. Both alfalfa and kava strongly inhibited barnyardgrass and monochoria growth for up to 10 days (80–100 % weed control). After 20–25 days, the magnitude of inhibition was drastically reduced, but was still effective (50 % weed control). A number of phenolic acids were detected in the soil even 50 days after incorporation in low concentration, but their concentrations reached a maximum after 10–15 days and were efficacious until 20–25 days. Phenolic acids varied between alfalfa and kava. The variations in electrical conductivity (EC) and osmotic pressure (OP) were strongly related to chemicals and toxic compounds exuded into the soil during decomposition and were proportional to the magnitude of inhibition observed, whereas pH did not appear to be correlated with inhibition. The decomposition of several unknown inhibitors present in kava was also analysed and assessed. Our findings indicate that these growth inhibitors were almost disintegrated in soil after 10 days, but strong inhibition was detected until 25 days after amendment. Results from this study demonstrate that chemicals released from allelopathic plants incorporated into soil are toxic and cause inhibition of certain species and could be exploited as a biological tool for weed management. 相似文献
4.
Xuan TD Elzaawely AA Fukuta M Tawata S 《Journal of agricultural and food chemistry》2006,54(3):720-725
This is the first report showing that kava lactones are plant and plant fungus growth inhibitors. Aqueous extract of kava roots showed high allelopathic potential and strongly suppressed germination and growth of lettuce, radish, barnyardgrass, and monochoria. Nine kava lactones were detected using GC-MS including desmethoxyyagonin, kavain, 7,8-dihydrokavain, hydroxykavain, yagonin, 5,6,7,8-tetrahydroxyyagonin, methysticin, dihydromethysticin, and 11-hydroxy-12-methoxydihydrokavain. Quantities of desmethoxyyagonin, kavain, 7,8-dihydrokavain, yagonin, methysticin, and dihydromethysticin detected were 4.3, 6.9, 18.6, 5.7, 1.4, and 5.4 mg/g of dry weight, respectively. These six major lactones in kava roots showed great herbicidal and antifungal activities. Growth of lettuce and barnyardgrass were significantly inhibited at 1-10 ppm, and four plant fungi including Colletotrichum gloeosporides, Fusarium solani, Fusarium oxysporum, and Trichoderma viride were significantly inhibited at 10-50 ppm. The biological activities of kava lactones were characterized by different double-bond linkage patterns in positions 5,6 and 7,8. The findings of this study suggest that kava lactones may be useful for the development of bioactive herbicides and fungicides. 相似文献
5.
Shinkichi Goto Tsuneo Kuwagata Pisarn Konghakote Anan Polthanee Yasushi Ishigooka Hitoshi Toritani Toshihiro Hasegawa 《Paddy and Water Environment》2008,6(1):153-157
Rice productivity in rainfed paddy fields varies with seasonal changes of water availability in which the conditions of flooding
are affected by the water balance. Hydrometeorological measurements were performed in a rainfed paddy field in Northeast Thailand
from July 2004 to December 2006 to analyze the water balance. As a result of our measurements, climatologically conditions
were classified as semi-humid with an annual precipitation of 1,100 mm/year and annual potential evaporation of 1,660 mm/year
in both the year. The surface layer of the paddy soil was clayey and the hydraulic conductivity was very low, so groundwater
levels remained below the soil surface even under flooded conditions during the rainy season. Seasonal changes in the amount
of soil water were very small, comprising only less than 16% of the total precipitation during the rainy season. Consequently,
an effective precipitation of less than 180 mm was enough to establish standing water in the rainfed paddy field.
Shinkichi Goto, Tsuneo Kuwagata and Pisarn Konghakote contributed equally to the paper. 相似文献
6.
Abdelnaser Abdelghany Elzaawely Shinkichi Tawata 《Journal of Crop Science and Biotechnology》2012,15(1):59-64
Rumex dentatus L. (Family: Polygonaceae) is a weedy plant widely distributed in many countries including Egypt. It has been used in the
Mediterranean diet as a leafy vegetable and its leaves and roots exhibited various biological activities. In our study, total
phenolics, antioxidant capacities assayed by 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging and β-carotene bleaching methods and reducing power were evaluated in different extracts/fractions of leaves and roots of R. dentatus grown in Egypt. In addition, their phenolic compositions were determined by GC-MS and HPLC. The results showed that total
phenolic content in the ethyl acetate fractions of leaves and roots were high and measured at 169.5 and 257.4 mg gallic acid
equivalent per g extract, respectively. The ethyl acetate fractions of leaves and roots exhibited strong DPPH activity and
the DPPH IC50 values were 0.021 and 0.012 mg mL−1 of leaves and roots, respectively. Furthermore, the ethyl acetate fractions of leaves and roots showed high reducing power
and antioxidant activity assayed by β-carotene bleaching method. GC-MS and HPLC analyses indicated that these fractions contained a variety of phenolic compounds
including p-hydroxybenzoic acid, syringic acid, vanillin, benzoic acid, ferulic acid, and cinnamic acid. Our study verified that the
ethyl acetate fractions of leaves and roots of R. dentatus have strong antioxidant activities which are correlated with its high levels of phenolic compounds and therefore, they could
be utilized as a natural source of antioxidant in food industry. 相似文献
7.
Upadhyay A Chompoo J Taira N Fukuta M Gima S Tawata S 《Journal of agricultural and food chemistry》2011,59(24):12858-12863
Neuraminidase is a rational target for influenza inhibition, and the search for neuraminidase inhibitors has been intensified. Mimosine, a nonprotein amino acid, was for the first time identified as a neuraminidase inhibitor with an IC(50) of 9.8 ± 0.2 μM. It was found that mimosine had slow, time-dependent competitive inhibition against the neuraminidase. Furthermore, a small library of mimosine tetrapeptides (M-A(1)-A(2)-A(3)) was synthesized by solid-phase synthesis and was assayed to evaluate their neuraminidase and tyrosinase inhibitory properties. Most of the tetrapeptides showed better activities than mimosine. Mimosine-FFY was the best compound, and it exhibited 50% neuraminidase inhibition at a low micromolar range of 1.8 ± 0.2 μM, whereas for tyrosinase inhibition, it had an IC(50) of 18.3 ± 0.5 μM. The kinetic studies showed that all of the synthesized peptides inhibited neuraminidase noncompetitively with K(i) values ranging from 1.9 -to 7.2 μM. These results suggest that mimosine could be used as a source of bioactive compounds and may have possibilities in the design of drugs as neuraminidase and tyrosinase inhibitors. 相似文献
8.
Yasushi Ishigooka Tsuneo Kuwagata Shinkichi Goto Hitoshi Toritani Hiroyuki Ohno Shin-ichi Urano 《Paddy and Water Environment》2008,6(1):55-71
The relationship between agricultural water demand and supply has been of interest to government decision makers and scientists
because of its importance in water resources management. We developed a water cycle model for eastern Eurasia that can estimate
water requirements for crop growth and evaluate the demand–supply relationships of agricultural water use on a continental
scale. To produce an appropriate water cycle, the model was constructed based on small drainage basins. To validate the model
performance with respect to simulated runoff, which is here considered as the available water resource, we compared our outputs
with those of other models and with observed river discharges. The results show that this model is comparable to other models
and that it is applicable for the evaluation of water cycles at continental scale. We defined two types of crop water deficits
(CWDs) as indicators of agricultural water demand. These were formulated by considering the physical processes of crop water
use; we did not include water consumption that is dependent on cultivation management practices, such as water losses in irrigation
systems. We assessed the reliability of our indicators by comparison with indicators from other studies and with published
statistics related to agricultural water use. These comparisons suggest that our indicators are consistent with independent
data and can provide a reasonable representation of water requirements for crop growth. 相似文献
9.
Toshihiro Hasegawa Shinji Sawano Shinkichi Goto Pisarn Konghakote Anan Polthanee Yasushi Ishigooka Tsuneo Kuwagata Hitoshi Toritani Jun Furuya 《Paddy and Water Environment》2008,6(1):73-82
Climate change will have significant impacts on the rain-fed rice production ecosystem, and particularly on the ecosystem’s
hydrology and water resources. Under rain-fed lowland conditions, substantial variations among fields in grain yield are commonly
observed, but a method that can account for field-scale yield variability to produce regional-scale yield estimates is lacking,
thereby limiting our ability to predict future rice production under changing climate and variable water resources. In this
study, we developed a model for estimating regional yields of rain-fed lowland rice in Northeast Thailand, by combining a
simple crop model with a crop calendar model. The crop model incorporates the effects of two important resources (water and
nitrogen) on crop growth. The biomass accumulation is driven by water use, whereas the nitrogen supply determines canopy development
and thereby constrains crop water use. Accounting for the wide range of planting dates and the strong photoperiod-sensitive
characteristics of rice varieties through the calendar model is an essential component in determining regional yield estimates.
The present model does not account for the effects of mid-season drought or flooding, but was nonetheless able to explain
the spatial and temporal yield variations at the province level for the past 25 years. Thus, it can be used as a prototype
for simulating regional yields of rain-fed lowland rice. 相似文献
10.
Shinji Sawano Toshihiro Hasegawa Shinkichi Goto Pisarn Konghakote Anan Polthanee Yasushi Ishigooka Tsuneo Kuwagata Hitoshi Toritani 《Paddy and Water Environment》2008,6(1):83-90
Rain-fed lowlands are major agricultural ecosystems used for rice production in Northeast Thailand. Developing a tool to assess
the effects of variable water conditions on the regional scale yield is also important to predict the effects of climate change
on food supply. To estimate regional yields, we need a simple but accurate measure of the crop calendar (i.e., the distribution
of planting dates), which has a strong influence on grain yield. In this article, we modeled the dependence of the crop calendar
on rainfall patterns based on a survey of the region’s farmers as a part of an effort to provide a stronger basis for regional
yield estimates. Our survey, conducted in 11 provinces for 2 years, confirmed the existence of large windows for sowing and
transplanting versus narrow windows for heading and harvesting for rain-fed lowland rice culture in all the provinces. Variable
water, soil, and toposequential conditions in the paddy fields were responsible for the large sowing and transplanting windows,
whereas the use of photoperiod-sensitive varieties explained the narrow windows for heading and harvesting. The crop calendar
was well expressed as a function of cumulative precipitation from June onward. When the crop calendar model was combined with
a simple phenology-based model that uses growing degree-days adjusted by a day-length factor, we could estimate the rice crop
calendar under rain-fed lowland conditions with acceptable accuracy. The model described in this article will be combined
with a crop growth model to improve regional yield estimates for rain-fed lowland rice. 相似文献
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