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1.
Howe  Henry F. 《Plant Ecology》1993,107(1):3-13
I explore the specialization versus generalization paradigm in frugivory and seed dispersal. This view predicts that some tropical trees produce nutritious fruits adapted for use by a small coterie of specialized frugivores that provide reliable seed dissemination. Other tree species are expected to offer superabundant fruits of lower nutritional reward, relying instead on common opportunistic frugivores that are individually less reliable, but collectively disperse seeds effectively. Though widely referenced, many aspects of the paradigm are untested with tropical trees and avian frugivores, primarily because plant ecologists rarely determine whether specialist or generalist foragers are responsible for different patterns of seed distribution, while students of foraging behavior rarely determine the effects seed dispersal by different animals for survival of seeds or seedlings of specialist or generalist trees.Ecological paradigms provide alternative hypotheses, without evolutionary arguments. Keystone species have ecological effects disproportionate to their abundance; it is important for management considerations to know whether fruiting trees or frugivores serve as keystone mutualists in tropical forests. Alternatively, the extent to which vertebrate seed dispersers influence density-dependent seed, seedling, sapling, or adult mortality may have important consequences for spatial dispersion and population dynamics of tree species in tropical forests.  相似文献   

2.
Stable isotopes (13C, D) and radiocarbon weremeasured in methane bubbles emitted from rice paddies and swamps in southernThailand. Methane emitted from the Thai rice paddies was enriched in13C (mean 13C; –51.5 ±7.1 and–56.5 ± 4.6 for mineral soil and peat soil paddies,respectively)relative to the reported mean value of methane from temperate rice paddies(– 63 ± 5). Large seasonal variation was observed in13C(32) in the rice paddies, whereas variationinD was much more smaller (20), indicating that variation in13C is due mainly to changes in methane production pathways.Values of 13C were lower in swamps (–66.1 ±5.1)than in rice paddies. The calculated contribution of acetate fermentation from13C value was greater in rice paddies (mineral soils:62–81%, peat soils: 57–73%) than in swamps (27–42%). Din methane from Thai rice paddies (–324± 7 (n=46)) isrelativelyhigher than those from 14 stations in Japanese rice paddies ranging from–362 ± 5 (Mito: n=2) to –322 ± 8(Okinawa: n=3), due tohigher D in floodwaters. 14C content in methane produced fromThai rice paddies (127±1 pMC) show higher 14Cactivity compared with previous work in paddy fields and those from Thai swamps(110±2 pMC).  相似文献   

3.
Various constructions of human haptoglobin (Hp) cDNA coding either for the complete 2FS precursor protein or only for the subunit have been placed under the control of the PR promoter in the bacterial expression vector pCQV2 (Queen, 1983). In addition to the expected 45,000 dalton polypeptide synthesized after induction of the PR promoter, the complete 2FS constructions constitutively express a smaller polypeptide of 30,000 dalton corresponding to a truncated Hp protein. Computer analysis of the HpcDNA revealed the presence of two strong potential bacterial promoters (2PF and 2PS) located in the duplicated 2FS sequence. Both Hp promoter signals are followed by potential mRNA start sites and ribosome binding sites at a compatible distance from initiation codons. In addition, the Hp2 cDNA sequence, when fused upstream to the cDNA coding for 1-antitrypsin, constitutively promotesin vivo the efficient expression of an hybrid protein specifically recognized by antibodies raised against 1-antitrypsin or haptoglobin.  相似文献   

4.
Isolated-bout method to estimate the retention times and dispersal distances was applied to the seed dispersal by red howler monkeys (Alouatta seniculus) and Humboldts woolly monkeys (Lagothrix lagotricha) in a lowland tropical forest at La Macarena, on the border of the Macarena and Tinigua National Parks, the Department of Meta, Colombia. Continuous observations were made on the feeding and ranging behavior of well-habituated troops of howler monkeys and woolly monkeys as well as continuous collection of monkeys feces. We selected out the isolated-bout as a feeding bout on the specific species that was only once recorded within 48 h before the seeds of that species appeared in the feces of monkeys. In that case, the seeds were strongly suggested to come from that isolated bout. Then retention times, route seed dispersal distances and direct seed dispersal distances were estimated. Howler monkeys, which are regarded as generalist herbivores, showed longer retention times and dispersal distances along monkeys route than did woolly monkeys, which are specialist frugivores. However, the direct distances that seeds were carried from the mother tree were not significantly greater for howler monkeys than for woolly monkeys. This shows that both retention time and movement patterns by the monkeys, especially the total ranging area, influence the direct distance that seeds are carried from the mother tree.  相似文献   

5.
The taxonomic significance of the trunk limbs of the chydoridae (Cladocera)   总被引:1,自引:1,他引:0  
N. N. Smirnov 《Hydrobiologia》1966,27(3-4):337-343
Summary The differences in the structure of the trunk limbs allow to outline three sections of Chydoridae (see table I and fig. 1), coinciding with the sections distinguished according to the structure of the head pores.
Chydoridae (Cladocera)
Chydoridae (. ), , .
  相似文献   

6.
Summary The inheritance of resistance to brown planthopper, Nilaparvata lugens (Stol.), of 20 rice cultivars was studied. Single dominant genes that are allelic to Bph 3 condition the resistance in cultivars Ptb 19, Gangala (Acc. 7733), Gangala (Acc. 15207), Horana Mawee, Kuruhondarwala, Mudu Kiriyal and Muthumanikam. Single recessive genes that are allelic to bph 4 govern the resistance in cultivars Gambada Samba, Heenhoranamawee, Hotel Samba, Kahata Samba, Kalukuruwee, Lekam Samba, Senawee, Sulai, Thirissa and Vellai Illankali. The resistance in Ptb 33, Sudu Hondarwala, and Sinna Sivappu is governed by one dominant and one recessive gene which segregate independently of each other. The dominant resistance genes in these cultivars appear allelic to either Bph 1 or Bph 3. Similarly, the recessive genes in these cultivars seem allelic to either bph 2 or bph 4. Further investigations are needed to conclusively determine the allelic relationships of resistance genes in Ptb 33, Sudu Hondarwala and Sinna Sivappu.  相似文献   

7.
Summary Progenies of a tetraploid 1BL/1RS wheat-rye translocation line, CV 256, selected from the cross Cando x Veery, were analyzed by means of Giemsa C-banding. CV 256 is cytologically stable for the presence of the 1BL/1RS translocation but still segregating for A- and B-genome chromosomes of Cando and Veery. In CV 256, nucleolar activity of the 1RS NOR locus is suppressed, as judged by the absence of a secondary constriction in that rye segment and the capability of organizing nucleoli. PAGE analysis of prolamins confirmed the presence of two 1RS secalins in all single seeds analyzed. SDS-PAGE analysis of reduced glutenins of single seeds indicated that some seeds contained the Cando Glu-B1 locus (subunits 6+8), some contained the Veery Glu-B1 locus (subunits 7+9) while others contained all four subunits, indicating that the material was heterozygous. Pm8 resistance is expressed in the tetraploid 1BL/1RS translocation line based on the reactions of six well-defined powdery mildew isolates. However, Pm8 resistance is not expressed in the hexaploid wheat cultivars Olymp, Heinrich and Florida, which also contain the 1BL/1RS translocation. Obviously, the existence of the 1BL/1RS translocation is not a proof for the expression of the associated genes. PAGE results did not show a clear linkage between powdery mildew resistance and the presence of 1RS secalins.  相似文献   

8.
Summary Thirteen spontaneously occurring chlorophyll deficient phenotypes have been described and their genetic basis was established. Ten of these — white, white tipped green, patchy white, white virescent, white striping 1, white striping 2, white striping 4, fine striping, chlorina and yellow virescent showed monogenic recessive inheritance and the remaining three — yellow striping, yellow green and light green seedling phenotypes showed digenic recessive inheritance. The genes for (i) white tipped green (wr) and yellow virescent (yv) and (ii) patchy white (pw) and white striping 1 (wst 1) showed independent assortment. Further, the genes for white (w), white tipped green (wr) and yellow virescent (yv) were inherited independently of the gene for hairy leaf margin (Hm).In the mutants — white tipped green, patchy white, white striping 1, white striping 2, fine striping, chlorina, yellow virescent, yellow striping, yellow green and light green phenotypes total quantity of chlorophyll was significantly less than that in the corresponding controls, while in white virescent there was no reduction in the mature stage. For nine of the mutants the quantity of chlorophyll was also estimated in F1's (mutant x control green). In F1's of six of the mutants — white tip, patchy white, chlorina, yellow virescent, fine striping and yellow striping the quantity of chlorophyll was almost equal to the wild type. In the F1's of three of the mutants — white striping 1, white striping 2 and light green an intermediate value between the mutant and wild types was observed. In yellow virescent retarded synthesis of chlorophyll, particularly chlorophyll a was observed in the juvenile stage. Reduced quantity of chlorophyll was associated with defective chloroplasts. In the mutants — white tipped green, white virescent, fine striping, chlorina, yellow striping, yellow green and light green defective plastids were also observed. In patchy white secondary destruction of chlorophylls and the presence of defective plastids were found to be associated with reduced chlorophyll quantity at maturity.Paper chromatographic studies of leaf flavonoids revealed some variation between the inbreds, but there were three common spots, 7, 8 and 9, except for PDP in which the spot 8 was absent. Chlorophyll deficient mutants differed from their respective controls in the absence of one or more of the spots present in the controls and in the presence of new spots in some of the mutants.Most of the chlorophyll mutants showed higher survival rate in the Kharif season than in Rabi season which was attributed to the higher mean day temperature and longer day light period in the Kharif season than in Rabi season.  相似文献   

9.
A study was undertaken to investigate the variability among lowland rice cultivars and the mode of gene action of aluminum (Al) toxicity tolerance in rice. Pregerminated seeds were grown in a nutrient solution containing 30 ppm Al and in normal nutrient solution, and relative root length (RRL) was determined at the 14-day-old stage to characterize genotypes for tolerance. Sixty-two traditional rice cultivars grown on lowland acid sulfate soil areas of Asia and West Africa were tested. Tolerant varieties Azucena, IRAT104, and Moroberekan, moderately sensitive IR29 and IR43, and sensitive IR45 and IR1552 were used to investigate the genetics of tolerance by diallel analysis. Of the 62 cultivars tested, only 3 were found to be sensitive to A l toxicity. Among the tolerant cultivars identified, 11 (Siyam Kuning, Gudabang Putih, Siyam, Lemo, Khao Daeng, Siyamhalus, Bjm-12, Ketan, Seribu Gantang, Bayer Raden Rati, and Padi Kanji) were found to possess higher levels of tolerance than the improved tolerant upland cultivar IRAT104. Diallel analysis revealed that high RRL is governed by both additive and dominance effects with a preponderance of additive effects. The trait exhibited partial dominance, and one group of genes was detected. Heritability was high, and environmenal effects were low. Findings suggest that when breeding for A1 toxicity tolerance, selection can be made in early generations. The pedigree method of breeding would be suitable. Combining ability analysis revealed the importance of both general combining ability (GCA) and specific combining ability (SCA) in the genetics of A1 toxicity tolerance in rice. GCA was more prevalent than SCA. Tolerant parens Azucena, IRAT104, and Moroberekan were the best general combiners. The presence of reciprocal effects among crosses suggested the proper choice of parents in hybridization programs. Results indicated that Azucena, IRAT 104, and Moroberekan should be used as the female in crosses for A1 toxicity tolerance.  相似文献   

10.
Mild cerebral anoxic/ischemic/stress insults promote tolerance and thereby protect the brain from subsequent lethal anoxic/ischemic insults. We examined whether specific activation of PKC , , , or isoforms is associated with ischemic preconditioning (IPC) in rat brain. IPC was produced by a 2-minute global cerebral ischemia. Membrane and cytosolic fractions of the hippocampi were immunoblotted using specific antibodies for PKC, , , and . PKC showed a significant translocation to the membrane fraction from 30 min to 4 h and PKC at 4 h following IPC. In contrast, the membrane/cytosol ratio of PKC showed a tendency to decrease at 30 min and 8 h, and the membrane/cytosol ratio of PKC was significantly decreased from 30 min to 24 h following IPC. These findings indicate PKC isoform-specific membrane translocations in the hippocampus after brief global brain ischemia and suggest that activation of PKC and PKC may be associated with IPC-induced tolerance in the rat hippocampus.  相似文献   

11.
Two forms of -glucosidase (EC 3.2.1.20), designated as I and II, have been isolated from sugarbeet (Beta vulgaris L.) seeds by a procedure including fractionation with ammonium sulfate and ethanol, carboxymethyl-cellulose column chromatography, and preparative disc gel electrophoresis. The two enzymes were homogeneous by polyacrylamide disc gel electrophoresis. Their molecular weights were 98,000 (I) and 60,000 (II). -Glucosidase I readily hydrolyzed maltose, isomaltose, kojibiose, maltotriose, panose, amylose, soluble starch, amylopectin and glycogen. -Glucosidase II also hydrolyzed maltose, kojibiose and maltotriose but hydrolyzed the other substrates only very weakly or not at all. -Glucosidase I hydrolyzed soluble starch at a faster rate than maltose. It produced isomaltose and panose as the main -glucosyltransfer products from maltose, whereas maltotriose was the main product of -glucosidase II. -Glucosidase I hydrolyzed amylose liberating -glucose. The neutral-sugar content was calculated to be 2.7% for -glucosidase I and 8.8% for -glucosidase II. The main neutral sugar was mannose in -glucosidase I, and glucose in -glucosidase II.  相似文献   

12.
Dispersal mode,seed shadows,and colonization patterns   总被引:12,自引:0,他引:12  
Willson  M. F. 《Plant Ecology》1993,(1):261-280
This review assesses the state of our knowledge about comparative seed shadows. Using data presently available in the literature, I compare the slopes (on a log-linear scale) of seed shadows for plants with different morphologically characterized modes of dispersal. The seeds of many species have no evident morphological adaptation for dispersal and seem to achieve only short-distance dispersal. Seed shadows for herbaceous species with devices for wind have flatter slopes and more distant modes and maxima than those of ballists, which in turn exceed those with no special devices. Seed shadows for wind-dispersed trees and shrubs had similar or steeper slopes than those for vertebrate-dispersed species in this sample. Species with poor mechanisms for dispersal in space only sometimes had the capacity for better dispersal in time (dormancy). Although some species exhibited seed shadows sufficiently steep to be predicted to colonize new-habitat in a front or phalanx pattern, actual colonization patterns must reflect many other factors.  相似文献   

13.
Purified myelin from fresh calf brain white matter was subfractionated in a discontinuous sucrose gradient; significant recovery of protein and 2,3-cyclic nucleotide 3-phosphohydrolase (CNP) and 5-nucleotidase (5N) activities occurred in all three obtained subfractions, the highest recovery being in the light subfraction; highest 5N and CNP specific activities were in medium myelin. Purified myelin was also subfractionated in a continuous sucrose gradient, with a similar localization of protein; CNP activity and 5N activity maxima suggest that myelin may be a predominant locus of 5N in bovine brain white matter. Freezing of brain white matter caused an increase in protein and in CNP and 5N total activity recoveries in denser myelin subfractions. Cytochemistry showed the reaction product of 5N in the whole myelin fraction to be associated with the innermost, outermost and medial compact myelin layers. Effects of non-ionic detergent (Lubrol WX) on 5N activity were studied, and the results also suggest the intrinsic nature of 5N as an ectoenzyme in myelin membranes. Lubrol WX was viewed as an advisable detergent for the stimulation of myelin 5N activity, but not for the solubilization of this enzyme.  相似文献   

14.
Novel O-serotypes were revealed among Pseudomonas syringae pv. garcae strains by using a set of mouse monoclonal antibodies specific to the lipopolysaccharide O-polysaccharide. Structural studies showed that the O-polysaccharide of P. syringae pv. garcae NCPPB 2708 is a hitherto unknown linear L-rhamnan lacking strict regularity and having two oligosaccharide repeating units I and II, which differ in the position of substitution in one of the rhamnose residues and have the following structures: I:3)--L Rha (12)-- L Rha (12)--L-Rha-(13)--L Rha (1;II: 2)--L-Rha-(13) -L-Rha-(12)--L-Rha-(13)--L Rha (1.The branched O-polysaccharides of P. syringae pv. garcae ICMP 8047 and NCPPB 588T have the same L-rhamnan backbone with repeating units I and II and a lateral chain of 14)- or 13)-linked residues of 3-acetamido-3,6-dideoxy-D-galactose (D-Fuc3NAc). Several monoclonal antibody epitopes associated with the L-rhamnan backbone or the lateral -D-Fuc3NAc residues were characterized.Translated from Mikrobiologiya, Vol. 73, No. 6, 2004, pp. 777–789.Original Russian Text Copyright © 2004 by Ovod, Zdorovenko, Shashkov, Kocharova, Knirel.  相似文献   

15.
Doubled haploid (DH) progeny from a cross between the scald susceptible barley (Hordeum vulgare L.) cultivar Ingrid and the resistant accession CI 11549 (Nigrinudum) was evaluated for resistance in the pathogen Rhynchosporium secalis (Oudem) J.J. Davis. Two linked and incompletely dominant loci confer resistance CI 11549 against isolate 4004. One is an allele at the complex Rrs1 locus on chromosome 3H close to the centromere; the other is located 22 cM distally on the long arm. The latter locus is designated Rrs4. In BC3-lines into Ingrid from CI 2222 (another Nigrinudum) resistance seems governed by one locus close to the telomeric region of chromosome 7H, probably allelic to Rrs2. In neither case did we find any trace of the recessive gene rh8 reported to be present in Nigrinudum. Various resistance donors of Ethiopian origin designated as Nigrinudum, Jet or Abyssinian were identical to a great extent with respect to markers, but differed in resistance to different isolates of scald or in barley yellow dwarf virus (BYDV) resistance. The implications for their use as differentials in scald tests and screening of germplasm collections are discussed.  相似文献   

16.
The structures of the N-linked sugar chains in the PAS-6 glycoprotein (PAS-6) from the bovine milk fat globule membrane were determined. The sugar chains were liberated from PAS-6 by hydrazinolysis, and the pyridylaminated sugar chains were separated into a neutral (6N) and two acidic chains (6M and 6D), the acidic sugar chains then being converted to neutral sugar chains (6MN and 6DN). 6N was separated into two neutral fractions (6N13 and 6N5.5), while 6MN and 6DN each gave a single fraction (6MN13 and 6DN13). The structure of 6N5.5, which was the major sugar chain in PAS-6, is proposed to be Man16 (Man13) Man14GlcNAc14GlcNAc-PA; 6N13, 6MN13 and 6DN13 are proposed to be Gal13Gal14GlcNAc12Man16 (Gal13Gal14GlcNAc12Man13) Man14GlcNAc14 (Fuc16)GlcNAc-PA;6M and 6D had 1 or 2 additional NeuAc residues at the non-reducing ends of 6MN13 and 6DN13, respectively. © 1998 Rapid Science Ltd  相似文献   

17.
Summary The question, Is Hb G Philadelphia linked to -thalassaemia? was first posed because the abnormal haemoglobin is found in heterozygotes at a concentration greater than 25%, the proportion predicted from a 4 -chain gene model. Globin chain biosynthesis was studied in a West Indian family in which one parent had + thalassaemia and the other was heterozygous for the G Philadelphia chain gene. The former had a globin chain production ratio / well above 1, while the latter had a ratio significantly less than 1. One child of the marriage had inherited the + thallassaemia from one parent and the G Philadelphia chain gene from the other and showed the typical picture of /-thalassaemia (/ ratio slightly above normal). It is explained in the discussion that the evidence favours a close linkage of 2 -chain genes.  相似文献   

18.
The dynamics of coupled biological oscillators can be modeled by averaging the effects of coupling over each oscillatory cycle so that the coupling depends on the phase difference between the two oscillators and not on their specific states. Average phase difference theory claims that mode locking phenomena can be predicted by the average effects of the coupling influences. As a starting point for both empirical and theoretical investigations, Rand et al. (1988) have proposed d/dt= — K sin ), with phase-locked solutions =arcsin( /K), where is the difference between the uncoupled frequencies and K is the coupling strength. Phase-locking was evaluated in three experiments using an interlimb coordination paradigm in which a person oscillates hand-held pendulums. was controlled through length differences in the left and right pendulums. The coupled frequency c was varied by a metronome, and scaled to the eigenfrequency v of the coupled system K was assumed to vary inversely with c. The results indicate that: (1) and K contribute multiplicatively to (2) =0 or = regardless of K when =0; (3) 0 or regardless of when K is large (relative to ); (4) results (1) to (3) hold identically for both in phase and antiphase coordination. The results also indicate that the relevant frequency is c/v rather than c. Discussion high-lighted the significance of confirming =arcsin(/K) for more general treatments of phase-locking, such as circle map dynamics, and for the 11 phase-entrainment which characterizes biological movement systems.  相似文献   

19.
A detailed investigation of hydrodynamic and conformational behavior has been made of the HM-crystallin and -crystallins of bovine lens. Results from this study indicated that HM (high-molecular-weight -crystallin) and (low-molecular-weight -crystallin) possess considerable size and charge heterogeneities in their native structures and subunit polypeptides, respectively. Sedimentation velocity showed a heterogeneous polydisperse system of HM with an average sedimentation coefficient of about 50 S and a more homogeneous system of -crystallin of 20 S. Viscosity and circular dichroism studies pointed to a compact and globular shape of dominant -sheet conformation for -crystallin, yet a highly asymmetrical and aggregated form for HM. The conformational stability of -crystallin was investigated in the presence of various denaturants. The evidence presented shows that hydrogen bonding is the main force in maintaining the quaternary structure of compact native -crystallin. Conformational flexibility of -crystallin demonstrated in the equilibrium unfolding study indicated a multistep transition that made the extraction of thermodynamic data from the heat denaturation study difficult. Temperature perturbation on -crystallin suggested the possible involvement of hydrophobic interaction in the aggregation process, leading to the formation of HM from -crystallin. The comparison of conformational properties between HM and -crystallin strongly indicated that HM is a denatured form of -crystallin.  相似文献   

20.
Summary Short oligocytidylates can act as templates for the self-condensation of guanosine 5-phosphorimidazolide. In the absence of a catalytic metal ion or in the presence of Pb2+ a noticeable template effect is already observed with the dimer and the yield of long oligomers reaches a plateau with a hexamer template. Short templates give oligomers longers than the template length. The products are predominantly 2-5 linked for the Pb2+-catalyzed reaction while mixed linkages are observed in the uncatalyzed reaction.In the presence of Zn2+, a template effect is first observed with the pentamer and is maximal by the heptamer. The products are predominantly 3-5 linked. Oligomers shorter than or as long as the template are obtained in substantial yield, and longer products in much lower yields.Abbreviations G Guanosine - Gp guanosine 2(3)-phosphate - pG guanosine 5-phosphate - Gp! guanosine cyclic 2,3-phosphate - ImpG guanosine 5-phosphorimidazolide - ImpG* [8-14C]-guanosine 5-phosphorimidazolide - pGp 5-phosphoguanosine 2(3)-phosphate - G2pG guanylyl-[2-5]-guanosine - G3pG guanylyl-[3-5]-guanosine - ImpGpG 5-phosphorimidazolide of GpG - (pG)n (n = 2,3) oligomers of pG - GppG P1, P2-diguanosine 5-diphosphate - GppGpG 5-[guanosine 5-pyrophosphate] of GpG - NH2pG guanosine 5-phosphoramidate - (pG)4+ tetramer and higher oligoguanylates with 5 terminal phosphate - oligo(G) oligoguanylate - Cp cytidine 2(3)-phosphate - Cp! cytidine cyclic 2,3-phosphate - (Cp)n–1 Cp! (n= 2,3,4) oligocytidylates terminated by 5-OH groups and 2,3-cyclic phosphates - oligo(C) oligocytidylate - poly(C) polycytidylic acid - poly(U) polyuridylic acid - poly(C,G) random copolymer of C and G - BAP bacterial alkaline phosphatase (E. coli) - EDTA ethylenediaminetetraacetic acid - Rf chromatographic mobility  相似文献   

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