Seed size variation: magnitude,distribution, and ecological correlates

Summary We examined seed-mass variation in 39 species (46 populations) of plants in eastern-central Illinois, USA. The coefficient of variation of seed mass commonly exceeded 20%. Significant variation in mean seed mass occurred among conspecific plants in most species sampled (by hierarchical ANOVA), averaging 38% of total variance. For most species, within-plant variation was the larger component of total variance, averaging 62% of total variance. Variation in seed mass among fruits within crops was significant in most species tested.We conclude that variation in seed mass among and within plants is widespread and common. There was little evidence of trade-offs between number of seeds and mean or variance of seed mass, and little correlational evidence of local competition for maternal resources. No consistent ecological (dispersal mode and growth form) correlates of variance of seed mass were evident.     

Hepatocystis in populations of baboons (Papio hamadryas s.l.) of Tanzania and Ethiopia

Bloodsmears from 119 yellow baboons (Papio hamadryas cynocephalus) in six groups in Mikumi National Park, Tanzania, and from 189 olive (P.h. anubis) hamadryas (P.h. hamadryas) and hybrid baboons in three groups in Awash National park, Ethiopia showed differing levels of infection with Hepatocystis simiae. 0% to 42% in the Tanzanian groups were carriers of the parasite but none of the Ethiopian baboons was positive. The remarkable absence of H. simiae in the Ethiopian baboons is believed to be related to environmental factors that exclude transmission in the absence of the Culicoides vector.     

Limited Tryptic Proteolysis of the Benzodiazepine Binding Proteins in Different Species Reveals Structural Homologies

Peptide mapping can be used to elucidate further the structural similarities of the benzodiazepine binding proteins in different vertebrate species. Crude synaptic membrane preparations were photoaffinity-labeled with [3H]flunitrazepam and subsequently degraded with various concentrations of trypsin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by fluorography allowed a comparison of the molecular weights of photolabeled peptides in different species. Tryptic degradation led to a common peptide of 40K in all species investigated, a finding indicating that the benzodiazepine binding proteins are structurally homologous in higher bony fishes and tetrapods.     

Repeated larval diapause and diapause-free development in geographic strains of the burnet moth Zygaena trifolii Esp. (Insecta,Lepidoptera)

Summary Zygaena trifolii is a long-day insect with temperature-dependent photoperiodic responses. All larval instars are sensitive to photoperiod; however, diapause may occur at the third larval stage or any subsequent larval instars. There were quantitative differences within populations in the threshold photoperiod for diapause induction. The diapause response was polymorphic, so that larvae might enter diapause at different instars under the same culture conditions. Furthermore, decreasing photoperiods below a critical daylength shifted the diapausing instar towards earlier stages. Geographic strains of Z. trifolii showed discontinuous clinal variation. Near the northern edge of the distribution [Cologne (Köln), FRG], there is first an obligatory diapause, mainly during early instars, and additional facultative (repeat) diapauses during later larval instars in subsequent years. In the southern part of its distribution, this burnet moth is partially bivoltine in the field with a facultative first developmental arrest and a decreased capacity for repeated diapause (Valencia, Spain; Marseille, France). Further experiments indicated that the photoperiodically controlled diapause reaction is also influenced by the number of photoperiodic cycles experienced during the period spent in each larval instar, which depends on temperature. The adaptive significance of obligatory and facultative repeated diapause, varying even among the offspring of a single female, may be to buffer the populations against the more extreme and, from year to year, unpredictable fluctuations in climatic conditions at the northern edge of the distribution.Abbreviations L₃ feeding 3rd larval instar - L₄D diapausing 4th larval instar - L₅D2 repeat-diapausing larval instar with second diapause at the 5th larval stage - LD light-dark cycle - KT shortday conditions (e.g. LD 8:16) - LT long-day conditions (e.g. LD 16:8)     

Adaptive variation of pelage color within and between species of the subterranean mole rat (Spalax ehrenbergi) in Israel

Summary Color notations of dorsal pelage were analyzed in 451 adult subterranean mole rats, comprising 19 populations and 4 chromosomal species (2n=52, 54, 58 and 60) of the Spalax ehrenbergi superspecies in Israel. In addition, the color notations of soil samples from the collection sites were measured. In an attempt to evaluate the degree of correlation between pelage color of mole rats and the local soil color, each color was compared both macro- and microgeographically. The macrogeographic comparisons were among populations of the 4 chromosomal species, and the microgeographic comparisons were among pairs of geographically neighboring subpopulations which occur under similar climatic conditions but differ in soil type and color. The results indicate that 1. no differences in pelage color notation exist between the sexes; 2. pelage of mole rats is generally characterized by an over-all grayish color, but its shades vary regionally and locally in accordance with varying soil color; 3. a positive correlation was found between pelage and local soil colors in the macrogeographic analysis and this correlation was verified in a microgeographic comparison; 4. specimens from populations of the northern chromosomal species (2n=52, 54) mainly inhabit terra rossa and basalt soils, respectively, with reddish brown tones, and they tend to have a more reddish shade, whereas animals from the central species (2n=58), which inhabits mainly dark soils including alluvial clays, terra rossa and brown rendzina and the souther species 2n=60, which occurs mainly in light soil types such as pale rendzina, sandy loams and loess, tend to have a more yellowish shade. The general appearance of specimens from 2n=58 was dark gray while that of 2n=60 specimens was light gray; 5. mole rats living in xeric environments (particularly 2n=60, but also 2n=54) are lighter than those which live in mesic environments (2n=52, 58). The results support the conclusion that pelage color of strictly subterranean mole rats is subject to selection pressures of overground predation of disharmonious types with their background soil color. The possibility that the pelage color variation and patterns also contributes to better thermoregulation while mole rats are above ground is discussed.     

Resistance to boron toxicity amongst several barley and wheat cultivars: A preliminary examination of the resistance mechanism

The mechanism of resistance toB toxicity in barley and wheat was studied in a solution culture experiment using several cultivars displaying a large range of sensitivity to excessB supply. Plants were cultured for 35 d atB concentrations ranging from normal to excessive (15 to 5000 M, respectively) then examined for dry matter production and theB distribution between roots and shoots.In both species, increasedB supply was accompanied by increased tissueB concentrations, development ofB toxicity symptoms and depressed growth. At each level ofB supply, however, resistant cultivars accumulated considerably lessB than did sensitive cultivars, in both roots and shoots. Even at the lowestB supply, at which noB toxicity symptoms developed and growth was not affected, resistant cultivars maintained relatively low tissueB concentrations. No cultivar displayed an ability to tolerate high tissueB concentrations.These results indicate that sensitivity toB toxicity in barley and wheat is governed by the ability of cultivars to excludeB. If theB concentrations of tissues is used to indicate resistance toB toxicity, then cultivars have the same ranking whether cultured at a normal or excessB supply.     

Patterns of variation in tail ornament size in birds

In recent years several different kinds of sexual selection models have been developed, and tail ornaments in birds have frequently been used as an example of a sexually selected character where the models might apply. However, very little is known about intra- and interpopulation variation in ornament size. We have studied the elongated tail ornaments in four species of whydahs Vidua , the forktailed flycatcher Tyrannus savana and the Asian paradise flycatcher Terpsiphone paradisi. Ornaments were relatively longer in males with the longest tarsi ('heterogony' with positive allometry). Also, tail lengths were remarkably variable within each geographical area, the coefficient of variation (average = 11%) being three times as high as for body size characters. Models, with female preference of ornaments bearing no relation to male viability, usually generate lines of neutral equilibria. Thus, they predict extraordinary variation in ornaments between populations. However, elongated tail ornaments did not show higher geographical variation than the body size characters, suggesting that there is no line of equilibria for these ornaments.     

The histogenesis of somaclones from tomato (Lycopersicon esculentum Mill.) cotyledons

Summary A histological study ofin vitro cultured cotyledonary expiants of tomato (Lycopersicon esculentum) was performed in order to determine the site (differentiated tissue or developing callus) and the mode of plant regeneration.Results have shown that callus develops at the excision sites of cotyledonary expiants and that shoots are formed exclusively within the unorganized callus: excision areas are the only morphogenetic sites and the proximal excision is the preferred site for plant regeneration.Shoots differentiate by organogenesis within the superficial region of the callus. Few neocambial cells cooperate in the neoformation. Origin from a single cell is highly unlikely since rarely observed single activated cells never developed into shoots.Regenerated plants may be chimeras if invitro culture induces genetic diversity in the initial cells.Abbreviations IAA Indole-3-acetic acid - c callus - d vegetative dome - s shoot - ad adaxial - ab abaxial - t tracheid - p parenchyma - S sieve tube     

Ribosomal DNA as a convenient probe to follow segregation and possible divergency from expected homozygosity after haploidization of an androgenetic process

Summary Restriction fragment length polymorphism of the wheat nuclear ribosomal DNA has been studied in several steps of a breeding scheme, including parental genotypes, F1 hybrid, F9 generation, and anther-derived doubled haploid lines obtained from F9. Ribosomal DNA represents a suitable molecular marker in following segregation and possible divergency from expected homozygosity after haploidization of an androgenetic process. It has been shown to undergo variations among the first cycle-doubled haploid lines in the relative amount of two different sizes of ribosomal DNA repeat units. The specificity and peculiar properties of the plant system used allowed us to assign an intrachromosomal location (short arm of the chromosomes 1B, 1R or 6B) to several ribosomal DNA repeat units that differ by the length of their nontranscribed spacer region.     

兰竹荔枝叶片营养元素适宜含量的研究

本研究旨在探讨福建荔枝最重要品种兰竹的叶片营养元素适宜含量。统计分析表明,不同地点、年份对同一品种叶片元素含量存在明显的差异;荔枝叶片含氮量变异系数最小,并按磷、镁、钙、钾依次增大。本研究初步提出的丰产兰竹荔枝秋梢叶片营养元素适宜含量为:氮1.5—2.2％,磷0.12—0.18％,钾0.7—1.4％,钙0.3—0.8％,及镁0.18一0.88％;其叶片氮、磷、钾、钙、镁的适宜比例是1:0.08:0.57:0.30:0.12。上列指标可供荔枝营养诊断指导施肥之参考。