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排序方式: 共有181条查询结果,搜索用时 218 毫秒
91.
Bharathan G Goliber TE Moore C Kessler S Pham T Sinha NR 《Science (New York, N.Y.)》2002,296(5574):1858-1860
KNOTTEDI-like homeobox (KNOXI) genes regulate development of the leaf from the shoot apical meristem (SAM) and may regulate leaf form. We examined KNOXI expression in SAMs of various vascular plants and found that KNOXI expression correlated with complex leaf primordia. However, complex primordia may mature into simple leaves. Therefore, not all simple leaves develop similarly, and final leaf morphology may not be an adequate predictor of homology. 相似文献
92.
Binh Thanh Nguyen Vinh Ngoc Nguyen Tong Xuan Nguyen My Hoang Nguyen Hao Phu Dong Gai Dai Dinh Nghia Van Nguyen Tan-Viet Pham 《Soil Use and Management》2023,39(1):415-428
Although most studies have indicated that biochar can boost rice (Oryza sativa) growth, the material may also suppress it, depending on ratios of carbon (C) to nitrogen (N) and available N to available phosphorous (P). The current study sought to examine the impacts of biochar on rice growth and to identify underlying mechanisms. A pot experiment was conducted using two soils of high (3.05%) and low (0.54%) organic carbon (OC) content, mixed with 0, 1.5, 3, 6, and 12% biochar and planted with rice. Rice growth components, five rice tissue nutrients, and nine soil properties were measured. The results showed that the response of rice growth to biochar rates could be described using an exponential-growth function in high-OC soil but an inverted U-shaped curve in low-OC soil. In high-OC soil, the 12% biochar rate led to the greatest total biomass, increased by 47%, whereas in low-OC soil, the 3 and 6% rates exhibited the highest total biomass, increased by 44%, compared to the no-biochar added soils. Biochar elevated the C:N ratio from 11.5 to 39.1, with an optimal range of 20–30 corresponding to the highest rice growth. Biochar declined the ratio of NH4-N to Mehlich-1 P, causing N deficiency. In brief, high biochar rates may suppress rice growth when the soil C:N ratio exceeds 30. The applied biochar rate should be considered based on soil properties typically OC and N content to obtain the C:N ratio between 20 and 30 for optimal rice growth. 相似文献
93.
This study was conducted to investigate the effect of dietary supplementation of cottonseed and soybean meal (CS) on growth
performance, feed utilization, and gossypol accumulation in juvenile (mean body weight 11 g) Japanese flounder Paralichthys olivaceus. Five isonitrogenous and isocaloric experimental diets (designated CS0, CS10, CS20, CS30, and CS40) containing 0, 10, 20,
30, and 40% CS mixture (1∶1 w/w) were formulated. After 9 weeks of feeding trial, fish fed all diets did not show significant
differences in growth performances, feed utilization, and whole body compositions. Hemoglobin content gradually decreased
(P<0.05) with increments of CS inclusion levels. There was a positive linear relationship between dietary gossypol and total
liver gossypol contents. Free radical scavenging activity in the experimental diets gradually increased with increment of
dietary CS inclusion. This finding indicates that the mixture of cottonseed and soybean meal with methionine and lysine supplementation
could replace up to 40% of fishmeal protein in diets. However, 20% fishmeal protein replacement by dietary inclusion of cottonseed
(9.4%) and soybean (8.7%) meal might be the optimum and safe level for the commercial use of CS in juvenile Japanese flounder. 相似文献
94.
Ky Xuan Pham Masafumi Amano Noriko Amiya Yutaka Kurita Akio Shimizu Kunio Yamamori 《Fisheries Science》2007,73(5):1113-1122
ABSTRACT: To clarify the possible roles of gonadotropin-releasing hormone (GnRH) in the reproduction of Japanese flounder Paralichthys olivaceus , localization of salmon GnRH (sGnRH), chicken GnRH-II (cGnRH-II), and sea bream GnRH (sbGnRH) immunoreactive (ir) cell bodies and fibers in the brain and pituitary were examined together with follicle stimulating hormone (FSH) and luteinizing hormone (LH)-ir cells in the pituitary by immunohistochemistry. sGnRH-ir cell bodies were localized in the ventromedial part of the rostral olfactory bulb and cGnRH-II-ir cell bodies were restricted to the midbrain tegmentum, while sbGnRH-ir cell bodies were evident in the preoptic area. sGnRH-ir fibers were distributed throughout the brain, especially abundant in the forebrain. cGnRH-II-ir fibers were also scattered in many areas of the brain with abundance in the midbrain, but sbGnRH-ir fibers were observed in the preoptic–hypothalamic area and innervated the pituitary. In the pituitary, neither sGnRH-ir fibers nor cGnRH-II-ir fibers were found, but sbGnRH-ir fibers were profuse in the neurohypophysis and invaded the proximal pars distalis, targeting FSH and LH cells. These results suggest that three GnRH systems can play different physiological roles in the brain of Japanese flounder. Among them, sbGnRH is considered to be involved in reproduction by stimulating gonadotropin secretion, while sGnRH and cGnRH-II can function as a neurotransmitter and/or neuromodulator within the brain in this species. 相似文献
95.
Antagonism of local isolates of Trichoderna spp. on citrus root rot disease by Fusarium solani in the mekong delta of vietnam 下载免费PDF全文
Duong Minh Jozef Coosemans Le Lam Cuong Ester Vandersmissen Pham Van Kim 《浙江大学学报(农业与生命科学版)》2004,30(4):392-392
The local isolates of Trichoderrma spp. and Fusariun solani were colected from citrus orchards in the Mekong delta of Vietnam and isolated on PDA, PDB and TSM medium for antagonism and Koch's postulate testing. The results showed that the high chitinolytic enzymes content of Trichoderma isolates can antagonise with Fusarium solani isolates by preventing the germination of Fusarium macroconidia in in-vitro condition. There are five promising isolates of Trichoderna spp. having high antagonism with Fusarium solani. These Trichoderma isolates also grew well in rice straws, maize stems, weeds and water hyacinth biowaste materials. These results supply the promising trend for biological control of root rot disease on citrus orchards of the Mekong delta. 相似文献
96.
Hung Quoc Pham Anh Tuong Nguyen Elin Kjørsvik Mao Dinh Nguyen Augustine Arukwe 《Aquaculture Research》2012,43(6):815-830
Predictive and reliable parameters of reproductive status are integral aspects of sustainable fisheries and aquaculture management. These parameters are also important for an accurate evaluation of the effects of different treatments on sexual maturation in fish farming. In the present study, we have characterized the seasonal reproduction profile and described changes in sex steroids in relation to gonadal maturation and development in female and male Waigieu seaperch (Psammoperca waigiensis). The experimental period covered a full calendar year (January–December). In males and females, we observed that plasma sex steroid hormones [oestradiol‐17β (E2), testosterone (T), 11‐ketotestosterone (11‐KT) and progesterone (P)] levels showed monthly fluctuations during the spawning period. Particularly, plasma steroid hormone levels were positively associated with gonadosomatic index values. In addition, high levels of plasma steroid coincided with recruitment of oocytes into yolk accumulation in females. The main spawning period occurred between April and October in females, and between March and November in males. The non‐aromatizable androgen, 11‐KT is generally believed to be the active male‐specific androgen in teleosts, and is associated with the process of spermiation, development of secondary sexual characteristics and regulation of male reproductive behaviour in most teleost species. In this study, we found relatively high amounts of 11‐KT in females between May and December, suggesting an integral role in the maturation process, also for the females. A rapid peak in plasma P level was observed in November and suggests significant roles during post‐spawning and/or resting periods in both female and male fish. Furthermore, all oocyte developmental stages were present within the same sampling month and also within the spawning period, demonstrating the gamete group asynchronous developmental strategy. Overall, Waigieu seaperch showed strong seasonality in reproductive development with corresponding sex steroid patterns. The data presented in this study may contribute to the understanding of the reproductive endocrinology of a tropical marine finfish with increasing industrial prospects and sustainable aquaculture of this species in a developing country, such as Vietnam. 相似文献
97.
98.
Tuntufye HN Ons E Pham AD Luyten T Van Gerven N Bleyen N Goddeeris BM 《Veterinary microbiology》2012,159(3-4):470-478
The aim of this study was to investigate if immunization with the ferri-siderophore receptors FepA, FhuE, IroN and IutA could protect chickens against avian pathogenic Escherichia coli (APEC) infection. The antigens were administered as recombinant proteins in the outer membrane (OM) of E. coli strain BL21 Star DE3. In a first immunization experiment, live E. coli expressing all 4 recombinant ferri-siderophore receptors (BL21(L)) were given intranasally. In a second immunization experiment, a mixture of E. coli ghosts containing recombinant FepA and IutA and ghosts containing recombinant FhuE and IroN was evaluated. For both experiments non-recombinant counterparts of the tentative vaccines were administered as placebo. At the time of challenge, the IgG antibody response for BL21(L) and a mixture of E. coli ghosts containing recombinant FepA and IutA and ghosts containing recombinant FhuE and IroN was significantly higher in all immunized groups as compared to the negative control groups (LB or PBS) confirming successful immunization. Although neither of the tentative vaccines could prevent lesions and mortality upon APEC infection, immunization with bacterial ghosts resulted in a decrease in mortality from 50% (PBS) to 31% (non-recombinant ghosts) or 20% (recombinant ghosts) and these differences were not found to be significant. 相似文献
99.
Gilles Bezançon Jean-Louis Pham Monique Deu Yves Vigouroux Fabrice Sagnard Cédric Mariac Issoufou Kapran Aïssata Mamadou Bruno Gérard Jupiter Ndjeunga Jacques Chantereau 《Genetic Resources and Crop Evolution》2009,56(2):223-236
Changes in the diversity of landraces in centres of diversity of cultivated plants need to be assessed in order to monitor
and conserve agrobioversity—a key-element of sustainable agriculture. This notably applies in tropical areas where factors
such as increased populations, climate change and shifts in cropping systems are hypothesized to cause varietal erosion. To
assess varietal erosion of staple crops in a country subjected to various anthropogenic and natural environmental changes,
we carried out a study based on a comparison of the diversity of pearl millet and sorghum varieties collected in 79 villages
spanning the entire cereal-growing zone of Niger over a 26 year period (1976–2003). For these two crops, the number, name
and type of varieties according to important traits for farmers were considered at different spatial scales (country, region,
village) at the two collection dates. The results confirmed the high diversity of millet and sorghum varieties in Niger. No
erosion of varietal diversity was noted on a national scale during the period covered. Some changes were observed but were
limited to the geographical distribution of certain varieties. This highlights that farmers’ management can preserve the diversity
of millet and sorghum varieties in Niger despite recurrent and severe drought periods and major social changes. It also indicates
that rainfed cereal cropping systems in Niger should remain to be based on millet and sorghum, while reinforcing farmers’
seed systems. 相似文献
100.
After years of unsustainable logging, dry deciduous dipterocarp forest (DDDF) has become poor in timber stocks and has been converted to industrial crops such as rubber. The objectives of this study were to assess teak (Tectona grandis L.f.) tree establishment under degraded DDDF conditions and to determine factors that influence the suitability of teak as a forest enrichment tree species. A set of 64 experimental plots of 4 900 m2 each was set up and observed for 4–5 years for testing enrichment planting with teak under various combinations of two groups of factors: ecological conditions and forest status. Weighted, non-linear, multivariate regression models were used to detect key factors that influenced the suitability of teak. The results showed that at the age of 4 years the average dominant tree height (defined as 20% of the tallest trees in the experimental plot) reached 11.2, 7.8, 5.3 and 3.8 m for very good, good, average and poor suitability levels, respectively. Survival rates of planted teak from average to very good suitability levels were over 90%. Six key factors that affected the suitability of teak were waterlogging during the rainy season, altitude, stand volume of the degraded DDDF, soil type, percentage of sand and concentration of P2O5 in the soil. Under the extreme ecological and environmental conditions of the DDDF, enrichment planting with teak gave promising results. 相似文献