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排序方式: 共有136条查询结果,搜索用时 31 毫秒
1.
Phenotypic plasticity in the morphology of small benthic Icelandic Arctic charr (Salvelinus alpinus) 下载免费PDF全文
Bjarni K. Kristjánsson Camille A.‐L. Leblanc Skúli Skúlason Sigurður S. Snorrason David L.G. Noakes 《Ecology of Freshwater Fish》2018,27(3):636-645
Intraspecific phenotypic diversity is the raw material for evolution, so understanding its origin and maintenance is critically important for conservation of biodiversity. Intraspecific diversity in a trait or a suite of traits can result from genetic diversity and/or phenotypic plasticity. The two are, however, not independent as plasticity has been shown to evolve. In this study, we evaluated the importance of phenotypic plasticity in generating morphological diversity in populations of small benthic Arctic charr in Iceland, using a rearing experiment with contrasting modes of feeding. We also examined the association between phenotypic plasticity in offspring groups generated by the contrasting feeding modes and important ecological variables characterising the natural habitats of the respective populations. Although the level of plasticity could not be related to any of the ecological measurements, clear differences in morphological reaction norms among populations suggest that plasticity is an important aspect of morphological diversity of the charr. It is not clear whether that plasticity is adaptive, but it is notable that reaction norms in all populations have similar reaction to the treatments. 相似文献
2.
Crops limit light for photosynthesis and growth of weeds. We studied the effect of reduced light on performance of six weed species [one invasive species (Amsinckia micrantha), three common species (Veronica persica, Capsella bursa‐pastoris, Viola arvensis) and two less common weeds (Anagallis arvensis and Scleranthus annuus)]. In two glasshouse experiments, six light levels were achieved aiming at 0%, 20%, 50%, 80%, 90% and 95% reduction of light and corresponding with daily light integrals (DLI) of 12.4, 9.63, 7.13, 2.74, 0.95 and 0.69 mol m?2 day?1 in experiment 1 and 21.2, 18.0, 10.7, 3.71, 1.64 and 1.20 mol m?2 day?1 in experiment 2. The number of leaves was strictly controlled by DLI. Chlorophyll content index, maximum photochemical efficiency of photosystem II (Fv/Fm), stomatal conductance, flowering and dry matter were strongly reduced when DLI was reduced to 0.69–3.71 mol m?2 day?1 for all species. Threshold DLI for flowering was ca. 3.71 mol m?2 day?1 for S. annuus, V. arvensis, A. arvensis and V. persica, while C. bursa‐pastoris deviated by flowering at DLI of 0.95 mol m?2 day?1. This may explain why C. bursa‐pastoris is common in the seedbank of Danish arable soils in spite of intensive farming with well‐fertilised and dense crops. 相似文献
3.
Md Abdul Wahab Sk Ahmad‐Al‐Nahid Nesar Ahmed Mohammad M Haque Mahmudul Karim 《Aquaculture Research》2012,43(7):970-983
Giant river prawn (Macrobrachium rosenbergii) farming plays an important role in the economy of Bangladesh. Presently, it is cultured in around 50 000 ha area with total annual production of 23 240 t. Traditional extensive prawn farming has been expanding over the last three decades through the introduction and adoption of improved culture systems, such as culture of prawn‐carps, prawn‐shrimp‐fish and prawn‐fish‐rice as concurrent and rotational systems. Efforts for the development of improved techniques on broodstock management, seed production and rearing and grow‐out of prawn have been made over the last decade. The outcomes are low‐cost feed for broodstock, production of post‐larvae in net cages (hapa), all‐male prawn culture, periphyton based prawn‐tilapia culture, C/N based prawn culture, organic prawn farming, prawn‐mola culture and prawn‐carp‐mola polyculture. Despite the development of culture technologies, a number of challenges for sustainable development of prawn farming need to be overcome to realize the potentials of this promising sector. Good aquaculture practises at all levels and application of measures for quality control and food safety would ensure sustainable development of prawn farming in Bangladesh. 相似文献
4.
Nicholas Clarke Silje Skår O. Janne Kjønaas Kjersti Holt Hanssen Tonje Økland Jørn-Frode Nordbakken 《Scandinavian Journal of Forest Research》2018,33(3):299-307
Short-term (three to four years) effects of forest harvesting on soil solution chemistry were investigated at two Norway spruce sites in southern Norway, differing in precipitation amount and topography. Experimental plots were either harvested conventionally (stem-only harvesting, SOH) or whole trees, including crowns, twigs and branches were removed (whole-tree harvesting, WTH), leaving residue piles on the ground for some months before removal. The WTH treatment had two sub-treatments: WTH-pile where there had been piles and WTH-removal, from where residues had been removed to make piles. Increased soil solution concentrations of NO3–N, total N, Ca, Mg and K at 30?cm depth, shown by peaks in concentrations in the years after harvesting, were found at the drier, less steep site in eastern Norway after SOH and WTH-pile, but less so after WTH-removal. At the wetter, steeper site in western Norway, peaks were often observed also at WTH-removal plots, which might reflect within-site differences in water pathways due largely to site topography. 相似文献
5.
Jarosław Skłodowski Paula Bajor Michał Trynkos 《European Journal of Forest Research》2018,137(5):745-757
The released excess anthropogenic nitrogen and carbon produces habitat enrichment, as exemplified by the modification of one-storied pine stands by introducing deciduous species into the understory or second story. In this study, we discuss the validity of pine stand modification by pitfall-trapping epigeic carabid beetles. Two hypotheses were formulated: (1) proportion of late-successional species is higher in assemblages inhabiting pine stands with understory or a second story than in one-storied pine stands; (2) plant litter composition affects carabid beetle assemblages more than other environmental variables. Additionally, characteristic carabid species of the respective pine stand types were identified. GLMM analysis revealed a higher proportion of late-successional species in pine stands with understory or a second story than in one-storied ones. NMDS separated those pine stand types. RDA analysis indicated that pine litter and humus had the strongest effect on carabid beetle assemblage structure in one-storied stands, being drier and thicker in this stand type than in the others. Indicator value analysis identified two characteristic non-forest species in one-storied stands The study revealed that the introduction of understory and particularly a second story into pine stands increased carabid beetle diversity and the proportion of late-successional species, confirming the validity of pine stand modification. 相似文献
6.
Nithikulworawong N Yakupitiyage A Rakshit S Srisapoome P 《Journal of fish diseases》2012,35(5):343-358
The complete cDNA sequence of the Nile tilapia T-cell receptor (TCR) β chain was cloned using 5' RACE. The full-length, 1263-bp cDNA contained a 942-bp open reading frame (ORF) encoding a 314-amino-acid protein. Sequence analyses revealed that the Nile tilapia TCR β chain contains four conserved cysteine residues involved in the formation of disulphide bridges and a conserved amino acid motif believed to be important for assembly and signalling of the TCR αβ/CD3 complex, both of which are normally found in the TCR β chain of other vertebrates. As detected using semi-quantitative and quantitative RT-PCR, the highest expression level of TCR β was detected in the thymus. Interestingly, Streptococcus agalactiae significantly induced the up-regulation of the TCR β chain, and the strongest up-regulation was detected in the brain and peripheral blood leucocytes (PBLs). In in vitro experiments, concanavalin A and Aeromonas hydrophila were found to significantly increase the expression of the TCR β chain in PBLs after 48 h (P < 0.01) and 72 h (P < 0.05), respectively. Furthermore, real-time PCR analysis showed that intraperitoneal injection (IP) of 10(7) cfu mL(-1) of S. agalactiae could induce TCR β expression that was greater than the expression observed following administration of 10(9) cfu mL(-1). The presence of the TCR β chain in fish detected in this study suggests the presence of T-cell populations that have been found in higher vertebrates, which may play a crucial functional role in the response to fish pathogens. 相似文献
7.
8.
Ali Asghar Karimi Marjan Ajami Yasin Asadi Nahid Aboutaleb Fazel Gorjipour Roya Malekloo Hamidreza Pazoki-Toroudi 《Iranian Biomedical Journal》2015,19(2):111-116
Background:
Skin flap grafting is a popular approach for reconstruction of critical skin and underlying soft tissue injuries. In a previous study, we demonstrated the beneficial effects of two 5α-reductase inhibitors, azelaic acid and finasteride, on tissue survival in a rat model of skin flap grafting. In the current study, we investigated the involvement of nitric oxide and inducible nitric oxide synthase (iNOS) in graft survival mediated by these agents.Methods:
A number of 42 male rats were randomly allocated into six groups: 1, normal saline topical application; 2, azelaic acid (100 mg/flap); 3, finasteride (1 mg/flap); 4, injection of L-NG-nitroarginine methyl ester (L-NAME) (i.p., 20 mg/kg); 5, L-NAME (20 mg/kg, i.p.) + azelaic acid (100 mg/flap, topical); 6, L-NAME (20 mg/kg, i.p.) + finasteride (1 mg/flap, topical). Tissue survival, level of nitric oxide, and iNOS expression in groups were measured.Results:
Our data revealed that azelaic acid and finasteride significantly increased the expression of iNOS protein and nitric oxide (NO) levels in graft tissue (P < 0.05). These increases in iNOS expression and NO level were associated with higher survival of the graft tissue.Conclusion:
It appears that alterations of the NO metabolism are implicated in the azelaic acid- and finasteride-mediated survival of the skin flaps.Key Words: Finasteride, Azelaic acid, Surgical flaps, Nitric oxide, Nitric oxide synthase Type II 相似文献9.
Ravindra DONDE Jitendra KUMAR Gayatri GOUDA Manoj Kumar GUPTA Mitadru MUKHERJEE Sk Yasin BAKSH Pradosh MAHADANI Khirod Kumar SAHOO Lambodar BEHERA Sushanta Kumar DASH 《水稻科学》2019,26(4):239-247
The introgression of wild chromosomal segments into popular rice varieties is one of the potential approaches for developing varieties for drought stress condition. Sixteen genotypes, including nine indica, two tropical japonica and five chromosome segments substitution lines(CSSLs) with different levels of tolerance/susceptibility to drought stress, were selected for diversity study. Sixty-three microsatellite markers were utilized for assessing genetic diversity. A total of 95 alleles were amplified, and out of them, 60 were polymorphic. Six unique alleles, amplified by the microsatellite loci RM276, RM472,RM488, RM537, RM541 and RM28089, were identified in six genotypes, namely FR13A, Brahamanakhi,RUF44, Swarna-sub1, Brahamanakhi and Satyabhama. The highest genetic similarity was found among CSSLs. Polymorphism information content(PIC) value varied from 0 to 1.00 with an average of 0.66 per locus. Twenty-eight microsatellites were found to be polymorphic, which could be used in marker-assisted selection programme. All the sixteen genotypes were grouped into two major clusters at genetic similarity of 0.64. In the cluster I, five CSSLs identified as diverse genotypes had wild ancestor segments responsible for drought tolerance, and hence they could be utilized as potential donors. The popular Indian varieties, Swarna-sub1 and IR64-sub1, could be used as recurrent parents in the future breeding program for developing varieties for abiotic stresses such as submergence and drought. 相似文献
10.
V. Sandhya M. Shrivastava Sk. Z. Ali V. Sai Shiva Krishna Prasad 《Russian Agricultural Sciences》2017,43(1):22-34
In the present study, 39 endophytic bacteria were isolated from different crops with main focus on maize roots and seeds. Endophytes were screened for drought stress tolerance, plant growth promoting (PGP) traits and antifungal activity. Out of 39 isolates, 32 could show drought tolerance up to–1.02 matric potential (MPa) and exhibited most of the plant growth promoting traits. But, only five isolates could show antagonistic activity against plant fungal pathogens. Based on the results, 10 promising isolates namely FTR, NFTR, FMZR9, FMZR2, MZ30V92, MRC12, MRC31, MRC33, MRC41 and MRR2 were selected and identified using biochemical and 16S rDNA gene sequencing as Pseudomonas aeruginosa (strains FTR and NFTR), Pseudomonas monteilii (strain FMZR2), Pseudomonas putida (strain FMZR9), Acitenobacter brumalii (strain MZ30V92), Enterobacter asburiae (strain MRC12), Sinorhizobium meliloti (strain MRC31), Pseudomonas thivervalensis (strain MRC33), Pseudomonas fulva (strain MRC41), and Pseudomonas lini (strain MRR2). Further, at–1.02 MPa all the 10 isolates showed PGP traits, and 3 isolates (FTR, NFTR and MRC12) showed antifungal activity. Thus, indicating that drought tolerant plant growth promoting antagonistic endophytic bacteria (PGPAE) helps in plant growth and disease management under drought stress. 相似文献