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41.
    
Intensive vegetable production in greenhouses has rapidly expanded in China since the 1990s and increased to 1.3 million ha of farmland by 2016, which is the highest in the world. We conducted an 11‐year greenhouse vegetable production experiment from 2002 to 2013 to observe soil organic carbon (SOC) dynamics under three management systems, i.e., conventional (CON), integrated (ING), and intensive organic (ORG) farming. Soil samples (0–20 and 20–40 cm depth) were collected in 2002 and 2013 and separated into four particle‐size fractions, i.e., coarse sand (> 250 µm), fine sand (250–53 µm), silt (53–2 µm), and clay (< 2 µm). The SOC contents and δ13C values of the whole soil and the four particle‐size fractions were analyzed. After 11 years of vegetable farming, ORG and ING significantly increased SOC stocks (0–20 cm) by 4008 ± 36.6 and 2880 ± 365 kg C ha?1 y?1, respectively, 8.1‐ and 5.8‐times that of CON (494 ± 42.6 kg C ha?1 y?1). The SOC stock increase in ORG at 20–40 cm depth was 245 ± 66.4 kg C ha?1 y?1, significantly higher than in ING (66 ± 13.4 kg C ha?1 y?1) and CON (109 ± 44.8 kg C ha?1 y?1). Analyses of 13C revealed a significant increase in newly produced SOC in both soil layers in ORG. However, the carbon conversion efficiency (CE: increased organic carbon in soil divided by organic carbon input) was lower in ORG (14.4%–21.7%) than in ING (18.2%–27.4%). Among the four particle‐sizes in the 0–20 cm layer, the silt fraction exhibited the largest proportion of increase in SOC content (57.8% and 55.4% of the SOC increase in ORG and ING, respectively). A similar trend was detected in the 20–40 cm soil layer. Over all, intensive organic (ORG) vegetable production increases soil organic carbon but with a lower carbon conversion efficiency than integrated (ING) management.  相似文献   
42.
    
Hail affects yield and quality of maize crops, and consequences also depend on the growth stage at which the injury occurred. Whole‐plant maize (WPM) silage is often used within the same farm for cattle feeding and biogas production. The present study aimed to verify the effects of hail damage, simulated by artificial defoliation, on yield and chemical and nutritional features, as well as on biochemical methane potential (BMP) of maize forage. In a randomized block design with three replicates, four defoliation levels (0%, 33%, 66% and 100% of leaf area removal respectively) have been applied at either the V12 (12th leaf), R1 (silking) or R3 (milk) stages for two consecutive years. WPM yield, chemical and nutritional features, and BMP were measured. Dry‐matter (DM) yield per hectare was progressively reduced (p < 0.001) with increasing levels of defoliation and with application at V12 in comparison with R1 or R3 (1.26 vs. 1.39 and 1.46 kg ha?1 for V12 vs. R1 and R3; p < 0.003). Nutritive value and BMP per unit of product were less altered than dry‐matter yield per hectare by defoliation. Anticipating defoliation reduced net energy for lactation (5.26 vs. 5.46 MJ kg?1 DM for V12 and R3 respectively; p = 0.02). Total defoliation resulted in an accumulation of nitrates (NO3) compared to the other treatments (3.98 vs. 1.53 g NO3 kg?1 DM; p < 0.001). BMP was mainly reduced by early and complete defoliation. Equations were developed to estimate the effects of defoliation on yield, composition, and nutritive and energetic values of WPM.  相似文献   
43.
    
Gorgostane steroids are isolated from marine organisms and consist of 30 carbon atoms with a characteristic cyclopropane moiety. From the pioneering results to the end of 2021, isolation, biosynthesis, and structural elucidation using 13C-NMR will be used. Overall, 75 compounds are categorized into five major groups: gorgost-5-ene, 5,6-epoxygorgostane, 5,6-dihydroxygorgostane, 9,11-secogorgostane, and 23-demethylgorgostane, in addition to miscellaneous gorgostane. The structural diversity, selectivity for marine organisms, and biological effects of gorgostane steroids have generated considerable interest in the field of drug discovery research.  相似文献   
44.
Assessing the health of the testes in domestic animals is an important aspect of the breeding soundness examination and selection. The aim of the present study was to develop a simple method for scanning and to establish ultrasonographically the gross anatomic structures of the goat testes. Six adult male goats were examined to study the sonographic appearance of normal testes and epididymides using a water bath based ultrasound scanning technique. The ultrasonographic examinations were done using a 5–9 MHz/60 mm (7.5 MHz) linear-array transducer and a B-mode scanner. The ultrasonographic examination was performed in goats after standardizing the procedure on six testes collected from slaughter house. Results showed that in live goats when the probe was placed directly over the scrotum it gave distorted and unclear image. In water bath method the entire scrotum was dipped into a container filled with water and linear probe was used to observe the sonographic features of the testis. Each testis was viewed vertically, resulting in longitudinal image which was frozen, measured and printed through a thermal printer. The results of the ultrasonogram revealed that the testicular parenchyma was homogenous and moderately echogenic throughout. The diameter (mean±se) of the right and left testes was 4.47±0.14 and 4.42±0.07 cm respectively and no significant difference was observed between the testes. The mediastinum testis was a 1.50±0.22 cm wide linear structure of greater echogenicity than the testicular parenchyma when viewed in the transverse plane and nearly circular echogenic “spot” in the midline of the testis when viewed horizontally. The head and tail of the epididymides were easily identified on all the testes, but the epididymal body and ductus deferens were difficult to identify consistently. The tail of the epididymis was easily identified on the distal end of the testis with sonolucent tubules and appeared sonographically as a ‘peaked cap’ upon the testicular parenchyma. The diameter (mean±se) of the tail of right and left epididymis was 2.11±0.18 and 1.92±0.06 cm and no significant difference was observed between epididymides. The vascular pampiniform plexus (1.42±0.18 cm) was easily identified on the proximal end of the testes. The tunics of the testes appeared as a bright echogenic line. Inter-testicular septum appeared between testes as a hyperechoic line. It is concluded that ultrasonography permits a noninvasive evaluation of the internal structure of the scrotum and testes and water bath based sonographic examination may prove to be a valuable simple diagnostic methodology for evaluating physiopathologic conditions of goat testes and can be employed as a routine investigative method during breeding soundness and clinical examination.  相似文献   
45.
Flooding is one of the major hazards of rice production for the rainfed lowland rice ecosystem, and tolerant cultivars are urgently needed to help protect farmers from submergence damage. A quick and efficient strategy was implemented to introgress SUB1, a major QTL for submergence tolerance, into a rainfed lowland mega variety BR11 of Bangladesh by only two backcrosses and one selfing generation. In marker-assisted backcrossing (MABC), one tightly-linked simple sequence repeat (SSR) and two gene-based markers, four flanking SSR and 116 background SSR markers were used for foreground, recombinant and background selection, respectively, in backcrosses between a SUB1 donor IR40931-33-1-3-2 and BR11. BR11-Sub1, identified in a BC2F2 plant, possessed BR11 type SSR alleles on all fragments analyzed except the SUB1 QTL. The introgression size in BR11-Sub1 was 800 Kb indicating approximately 99.8% identity to BR11. BR11-Sub1 along with other introgression lines showed submergence tolerance similar to the tolerant parent. Yield, yield-component parameters and grain physico-chemical properties showed successful recovery of the BR11 traits in BR11-Sub1, with yield potential ranging from 5.2 to 5.6 t/ha, not significantly different from the recurrent parent mega variety BR11. Producing a large number (~1000) of backcross F1 plants was considered essential to achieve recombination on both sides of the gene, limiting linkage drag with only two backcrosses. A large number of background markers ensured proper recovery of the recurrent parent genome in the BC2F2 generation. The study demonstrates a rapid and highly precise strategy to introgress a major QTL by BC2F2 generation into a modern rice variety using an unadapted donor. The variety can replace BR11 on more than 2 million of ha in Bangladesh and provide major increases in rice production.  相似文献   
46.
Laboratory and field trials with two synthetic Juvenil Hormone Analogues on four Aphid species Two juvenile hormone analogues (JHA) were applied in laboratory in three different concentrations to four aphid species. Mortality-concentrations and mortality-time for the lowest concentration were plotted on logprobit paper and the slope calculated from the eye fitted lines. The results indicated the feasibility of probit analysis for concentration-mortality or time mortality responses. However in one of the aphid species i. e.Aphis gossypii, there was a lack of linearity in the relationship, this species proved to be tolerant to JHA in field trials. Both JHA supressed progeny production, the supression was found to be selective to different species. In field trials both JHA brought about appreciable reductions in the populations with the exception ofAphis gossypii. The colour ofH. arundinis was found to differ in adults insuing from treated nymphs, otherwise no remarkable morphonogenic changes were observed.  相似文献   
47.
Indigenous communities in the Chittagong Hill Tracts (CHT) of Bangladesh had been conserving small patch of forests, commonly called village common forests (VCFs), especially for drinking water and non-timber forest produce. The size of VCFs has been decreasing, due to increasing population and conversion of forests for shifting cultivation. To restore the degraded forest resources and conserve the forest ecosystems in the VCF of the CHT, an intervention was undertaken in Bandarban, Bangladesh by Arannayk Foundation, an organization established jointly by the Government of Bangladesh and the United States of America. A training program on leadership, organizational development and alternative income generating activities was implemented to build the capacity of the members of the VCF management committee. The impact of the interventions was measured at the end of third year. Incomes of VCF-dependent communities were found to increase with resultant reduction of their dependence on VCFs. The intervention encouraged women’s participation in forest management and facilitated a written format of the constitution of the VCF management. The study identified that more training and awareness-raising activities are needed to ensure sustainability of the interventions. Mobilizing funds for the communities for sustainable alternative livelihoods was found effective. Appropriate compensation for conservation was found to make the restoration and conservation activities sustainable.  相似文献   
48.
The cytological status of plantlets regenerated from shoot apical meristems of Pisum sativum was investigated. Chromosome counts in root apices of in vitro regenerated plants showed a preponderance of diploid cells. Moreover, the karyotypes of root-tips from plants derived from culture and from normal plants were basically the same. Topics such as the treatment of chromosomal armlength data, simple statistical comparison of samples derived from normal and regenerated plants are discussed.  相似文献   
49.
比较了不同浓度无机肥料(尿素和重过磷酸钙)对四种农林作物(楹树、雨豆树、相思树和印度田菁)生物固氮和种苗生长的影响。种子萌发一个月后利用不同浓度肥料(尿素:40kg·hm-2,80kg·hm-2;重过磷酸钙:40kg·hm-2,80kg·hm-2;(尿素 重过磷酸钙)40kg·hm-2和(尿素 重过磷酸钙)80kg·hm-2)处理种苗。结果表明:中等浓度无机肥料促进了种苗的生长,但较高浓度无机肥料也不利于种苗的生长。当施加尿素时根瘤菌的数量大小明显受抑制,但随着增加磷肥(重过磷酸钙)根瘤菌的数量大小增加。本研究有助于农业人员利用无机肥料改善土壤提高农林作物的生物固氮和种苗生长。图2表6参33。  相似文献   
50.
A new chloro-pseudoguaianolide-type sesquiterpene lactone, 11β-hydroxy-13-chloro-11,13-dihydrohymenin (1), was isolated from the Egyptian medicinal plant Ambrosia maritima. The structure was determined by spectroscopic methods, particularly high-resolution 1H, 13C-NMR and 2D 1H–1H and 1H–13C COSY NMR analysis.  相似文献   
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