The linear 20 kb mitochondrial genome of Pandorina morum (Volvocaceae,Chlorophyta)

A physical restriction map of the mitochondrial genome from one clone (TCC 854) of the sexually isolated populations (syngens) of the morphologically uniform species Pandorina morum Bory has been constructed using restriction endonucleases Ava I, Bam HI, Bgl II, Eco RI, Kpn I, and Pst I. The 20 kb linear genome can easily be separated from plastid DNA, nuclear satellite rDNA, and main band (nuclear) DNA on a Hoechst/CsCl buoyant density gradient. The Pandorina mitochondrial DNA shows sufficient similarity to the 16 kb mitochondrial genome of Chlamydomonas reinhardtii to cross-hybridize, and also hybridizes with a probe containing maize mitochondrial 18S rRNA genes. Double digests, self-probing, and Bal31 exonuclease experiments suggest that 1.8 to 3.3 kb of sequence is repeated at each end of the genome as an inverted repeat. Mitochondrial genome sizes of other P. morum syngens were found to range from ca. 20 to ca. 38 kb. The mitochondrial genome should be valuable for taxonomic studies; it can be used for comparative organellar studies; and it should be of interest to compare with that of other plant and animal mitochondrial genomes.     

Factors controlling the seasonal incidence of Pandorina morum (Mull.) Bory (Chlorophyta,Volvocales) in a small pond

Pandorina morum normally forms large summer populations in Abbot's Pond, a shallow (3.5 m maximum) but sheltered and thermally stratified pond. Restriction of growth until summer is shown not to be due to secretion of inhibitory substances by other organisms in winter and spring, nor to the prior production of stimulatory substances. Growth in February is prevented by low temperature, and between February and May 1972 was restricted by phosphate limitation. Development of summer populations was associated with direct thermal stratification and the decline of non-motile algal competitors for nutrients, and with the availability of phosphate from the anaerobic hypolimnion through diurnal migration of the coenobia.     

Acetate Metabolism by an Obligate Phototrophic Strain of Pandorina morum1

SYNOPSIS. Acetate metabolism was studied in 2 strains of the green alga Pandorina morum. Both strains were capable of mixotrophic growth in the light, but only one strain was capable of heterotrophic growth in the dark. ¹⁴C-2-acetate uptake by both strains was studied in the light and dark, in the presence and absence of CO₂ and 3(3,4-dichlorophenyl)-1,1-dimethylurea (10^?5M). The distribution of radioactivity incorporated into the insoluble, aqueous and chloroform soluble fractions of the cells was determined. The strain incapable of heterotrophic growth in the dark was found to incorporate very little acetate in the dark, and its ability to incorporate acetate into the insoluble fraction was severely limited under all conditions. Incorporation into the aqueous and chloroform-soluble fractions in the light was similar in both strains. The reduced incorporation into the insoluble fraction was almost totally the result of limited incorporation of acetate into polysaccharides by the obligate phototrophic strain.     

Colonial development in Pandorina morum. II. Colony morphogenesis and formation of the extracellular matrix

The colonial green alga, Pandorina morum, resembles its unicellular relative Chlamydomonas in both intracellular architecture and the composition of the extracellular matrix. Despite these similarities, cell division in Pandorina leads to the formation of a colony instead of the 8 or 16 single cells produced by cell division in Chlamydomonas. To study colony formation, partially synchronized cultures of P. morum were sampled periodically and stained with ruthenium red for electron microscopy. The cells of the colony were found to be held together during development by medial and basal connections between cells; the basal connections include strands of chloroplast. Studies of cells removed from the parental matrix before division confirmed that the cytoplasmic connections are strong enough to maintain the colonial configuration. After the medial connections break, the cells of the plate of the developing colony swing outward and attain the nearly spherical colonial configuration; the basal connections are still present. After this inversion, the formation of the extracellular matrix begins, with the colonial boundary appearing first. Capsule and sheath then form on the outer and inner faces of the colonial boundary until the extracellular matrix is complete. The process is compared to previous observations of Volvox, and possible evolutionary implications are discussed.     

Colonial development in Pandorina morum. I. Structure and composition of the extracellular matrix

Every cell in a colony of the freshwater alga Pandorina morum produces a daughter colony in each round of vegetative reproduction. The cells of P. morum structurally resemble those of Chlamydomonas and do not obviously differ from their presumptive unicellular ancestor in ways that would account for their colonial state. It is therefore possible that their colonial association may be the result of altered extracellular matrix, intercellular connections, or modified processes of cell division and matrix formation. The ultrastructural studies and chemical analysis reported here show that the matrix of P. morum is a multilayered structure containing hydroxyproline-rich glycoproteins and sulfated polysaccharide. Significantly, this matrix displays no major differences from the “wall” of Chlamydomonas species. No intercellular connections have been found in mature colonies. The extracellular matrix therefore maintains, but does not initiate, the colonial arrangement of the cells.     

Sulfur requirement of Gonium (Volvocaceae)

The sulfur requirement of six strains of three species of Goniumhas been investigated. These strains can grow well with sulfide,sulfite, bisulfite, thiosulfate or sulfate in light and darkness.They are the first algae shown to utilize sulfide as a sulfursource. However, organic sulfur sources (methionine, cystine,cysteine, homocysteine, homocystine and taurine) were ineffectivefor growth of Gonium. (Received December 6, 1975; )     

中国李种质资源形态性状和农艺性状的遗传多样性分析

以国家果树种质熊岳李杏圃中保存的405份中国李和杂种李为材料,依据32个主要形态性状和农艺性状的评价数据,对这些主要性状进行了遗传多样性、相关性和主成分分析.结果表明,中国李表现出丰富的遗传多样性;从字符型形态和农艺性状数据看,叶形、果形、果皮彩色和果肉色泽等性状均表现出较为丰富的多样性;从数值型形态和农艺性状数据看....     

牛角藓(Cratoneuron filicinum(Hedw.)Spruce)叶片形态特征的生态变异及其分类学意义

对200份牛角藓(Cratoneuron filicinum)标本的叶片长度、叶片宽度、中肋基部宽度、叶片中部细胞的宽度和长度、角部细胞的宽度和长度及叶片弯曲程度等特征进行线性回归分析.结果表明,在较低样本量时,来源于不同生境的牛角藓叶片各性状特征间的线性相关性不显著,来源于水生群落的牛角藓叶片各性状特征问的线性相关性显著.在样本量较大时,牛角藓叶片各性状特征间的线性关系相关性显著.说明牛角藓叶片的某些特征在自然选择压力下发生了变化,表现出较高的遗传多样性;这些特征虽然受环境影响而在形态上表现出变异,但总的趋势是相似的.     

Growth inhibitors produced by the green algae (Volvocaceae)

Summary A complex system of growth inhibition is present in the green algae (Volvocaceae). Inhibitors are found in the culture filtrates of some genera which limit their own growth (autoinhibition) while others in the family produce inhibitors which check the growth of other genera (heteroinhibition). These inhibitors are destroyed by autoclaving.     

Morphology and evolution of sexual reproduction in the Volvocaceae (Chlorophyta)

Morphological features of sexual reproduction in the Volvocaceae are reviewed, focusing particularly on gametic union and zygote gemination. Both of the two conjugating gametes of the isogamous generaPandorina, Volvulina andYamagishiella bear a tubular mating structure (mating papilla), and plasmogamy is initiated by union of the papillae tips. On zygote germination, a single biflagellate gone cell is released from the zygote wall. Although all the anisogamous and oogamous genera of the Volvocaceae produce “sperm packets” during gametogenesis and a single gone cell at zygote germination, some difference can be recognized in the male gametes. The male gametes ofEudorina bear a tubular cytoplasmic protuberance (putative mating papllla) near the base of the flagella, whereas such a structure recognized at the light microscopic level is not evident inPleodorina andVolvox. Evolution of the sexual reproduction characteristics of volvocacean algae is discussed on the basis of recent cladistic analysis of morphological data as well as of the ribosomal (r) RNA phylogeny and large subunit of the ribulose-1, 5-biphosphate carboxylase/oxygenase(rbcL) gene trees. Dedicated to Emeritus Prof. Hideo Kasaki (Tokyo Metropolitan University) on the occasion of his 77th birthday. Recipient of the Botanical Society Award for Young Scientists, 1994.     

Morphological specialization of heterantherous Rhynchanthera grandiflora (Melastomataceae) accommodates pollinator diversity

• The tropical Melastomataceae are characterized by poricidal anthers which constitute a floral filter selecting for buzz‐pollinating bees. Stamens are often dimorphic, sometimes with discernible feeding and pollinating functions. Rhynchanthera grandiflora produces nectarless flowers with four short stamens and one long stamen; all anthers feature a narrow elongation with an upwards facing pore.
• We tested pollen transfer by diverse foraging bees and viability of pollen from both stamen types. The impact of anther morphology on pollen release direction and scattering angle was studied to determine the plant's reproductive strategy.
• Medium‐sized to large bees sonicated flowers in a specific position, and the probability of pollen transfer correlated with bee size even among these legitimate visitors. Small bees acted as pollen thieves or robbers. Anther rostrum and pore morphology serve to direct and focus the pollen jet released by floral sonication towards the pollinator's body. Resulting from the ventral and dorsal positioning of the short and long stamens, respectively, the pollinator's body was widely covered with pollen. This improves the plant's chances of outcrossing, irrespective of which bee body part contacts the stigma. Consequently, R. grandiflora is also able to employ bee species of various sizes as pollen vectors.
• The strategy of spreading pollen all over the pollinator's body is rather cost‐intensive but counterbalanced by ensuring that most of the released pollen is in fact transferred to the bee. Thus, flowers of R. grandiflora illustrate how specialized morphology may serve to improve pollination by a functional group of pollinators.

     

Morphological architecture of Actinocephalus (Koern.) Sano (Eriocaulaceae-Poales)

Actinocephalus exhibits perhaps more diversity in habit than any other genus of Eriocaulaceae. This variation is largely a result of differences in the arrangement of the paraclades. Based on the analysis of stem architecture of all 25 species of Actinocephalus, the following patterns were established: (1) leaf rosette, with no elongated axis, instead the axillary paraclades originating directly from the short aerial stem, (2) rosette axis continuing into an elongated axis with spirally arranged paraclades, (3) an elongated axis originating from a rhizome, with ramified paraclades, and (4) an elongated axis originating from a short aerial stem, with paraclades arranged in a subwhorl. The elongated axis exhibits indeterminate growth only in pattern 4. Patterns 3 and 4 are found exclusively in Actinocephalus; pattern 1 occurs in many other genera of Eriocaulaceae, while pattern 2 is also found in Syngonanthus and Paepalanthus. Anatomically, each stem structure (i.e., paraclade, elongated axis, short aerial stem, rhizome) is thickened in a distinctive way and this can be used to distinguish them. Specifically, elongated axes and paraclades lack thickening, thickening of short aerial stems results from the primary thickening meristem and/or the secondary thickening meristem. Thickening of rhizomes results from the activity of the primary thickening meristem.     

Male fitness of honeybee colonies (Apis mellifera L.)

Honeybees (Apis mellifera L.) have an extreme polyandrous mating system. Worker offspring of 19 naturally mated queens was genotyped with DNA microsatellites, to estimate male reproductive success of 16 drone producing colonies. This allowed for estimating the male mating success on both the colony level and the level of individual drones. The experiment was conducted in a closed population on an isolated island to exclude interferences of drones from unknown colonies. Although all colonies had produced similar numbers of drones, differences among the colonies in male mating success exceeded one order of magnitude. These differences were enhanced by the siring success of individual drones within the offspring of mated queens. The siring success of individual drones was correlated with the mating frequency at the colony level. Thus more successful colonies not only produced drones with a higher chance of mating, but also with a significantly higher proportion of offspring sired than drones from less successful colonies. Although the life cycle of honeybee colonies is very female centred, the male reproductive success appears to be a major driver of natural selection in honeybees.     

Morphological diversity of Ethiopian barley (Hordeum vulgare L.) in relation to geographic regions and altitudes

A total of 199 germplasm accessions collected from 10 administrative regions of Ethiopia and four released cultivars, which were used for estimating of error variance, of barley in Ethiopia were field evaluated for nine agronomic traits at Holetta and Bekoji Agricultural Research Centers of Ethiopia during the 2006 main cropping season using non-replicated augmented design plots consisting of four incomplete blocks. The objectives were to assess the extent and pattern of morphological variation in the barley accessions with respect to regions and altitude of collection, to classify the genotypes tested into relatively homogenous groups and to identify the major traits contributing to the overall observed diversity in the germplasm. Genotype variance estimate of regions and altitudes indicated wide variation among accessions depending on the traits involved. The presence of high morphological variation within regions and altitudes particularly above 2000 m a.s.l. indicated the potential of each region and high altitude zones for barley improvement and conservation in the country. The clustering of accessions did not show grouping on the basis of regions of origin. Traits like thousand kernel weight, plant height, days to head and days to maturity accounted for most of the gross variance among the barley accessions and played role in differentiating accessions collected from different regions and altitude classes into principal components. In general because of environmental factors on the observed morphological variation future germplasm collection should consider to explore wide geographical and climatic differences within the country.     

Successful and unsuccessful development of colonies of Vespula vulgaris (Linn.) (Hymenoptera: Vespidae)

Abstract.

• 1 Six categories of immature and five categories of mature colonies are described and their developmental relationships suggested.
• 2 Mature brood destroyed by the workers became numerous in 46.4% of the immature colonies. Most of these formed unsuccessful colonies (36.9%) producing few or no queens. The remaining 9.5% recovered to form successful colonies.
• 3 Successful colonies either reared queens only (mean 356 queens), or queens (mean 1461) and males (mean 254) in their large cells.
• 4 The number of small cells in mature colonies correlated with the number of cells built by the founder queen.
• 5 The greater the number of large cells in a mature colony the greater were the chances that a larger proportion of these cells would be used to rear adults.
• 6 The number of small and large cells are correlated in mature successful colonies.
• 7 Queen activity and quality are important factors in the control of colony size and success.
• 8 Selective destruction of male sealed brood in the large cells is linked to worker, rather than queen, control.

     

Modelling the role of intracolonial genetic diversity on regulation of brood temperature in honey bee (Apis mellifera L.) colonies

In polyandrous social insects such as honey bees, a worker’s affinity for a particular task may be genetically infl uenced and so some patrilines may have lower stimulus thresholds for commencing a task than others. We used simulation models to investigate the effects of intracolonial diversity in the task thresholds that stimulate workers to engage in heating and cooling during nest thermoregulation. First, we simulated colonies comprised of one or 15 patrilines that were engaged in heating the brood nest, and observed that single patriline colonies maintained, on average, less stable brood nest temperatures than multiple patriline colonies. Second we simulated colonies with five patrilines that were engaged in cooling their nest, recording the proportions of bees of different patrilines that engaged in nest cooling in response to changing temperatures. Both of our simulations show remarkably similar qualitative patterns to those that we have previously observed empirically. This provides further support for the hypothesis that geneticallybased variability in task thresholds among patrilines within honey bee colonies is an important contributor to the ability of colonies to precisely thermoregulate their nests, and we suggest that diversity is important for optimal expression of a range of other colony-level phenotypes. Received 17 June 2005; revised 27 October 2005; accepted 23 December 2005.     

Morphological diversity and function of the stigma in Ficus species (Moraceae)

The stigma plays several roles such as pollen hydration and selection, and pollen tube nutrition. In the Ficus-fig wasp mutualism, stigmata have an additional, almost unknown, function by representing a physical interface for both plant and wasp reproduction. We used light and electron microscopy to compare the detailed morphology of the stigmata of nine Ficus species of different sections and with different pollination modes and sexual expressions. Figs were collected at the stage when the stigmata were receptive for pollination. Stigmata in actively pollinated monoecious species have well developed papillae concentrated on the adaxial surface exposed towards the fig cavity. Conversely, the passively pollinated monoecious species have the whole surface of the stigmata covered by somewhat smaller papillae. In both actively and passively pollinated monoecious species these features are consistent, irrespective of style length. In all actively pollinated gynodioecious species, the stigmata of pistillate flowers were tubular or infundibuliform whereas in almost all actively pollinated monoecious species (except F. racemosa) the stigmata were filiform, with one branch or two asymmetric branches. In gynodioecious species the short-styled flowers in “male” figs show a limited receptive surface with small papillae, while the stigmata of long-styled flowers in “female” figs are covered by papillae that extend down the sides of the style, increasing the stigmatic surface. In actively pollinated species, stigmata are cohesive, forming a common surface for pollen tube germination (= synstigma). The synstigma arrangement was quite variable: lax, cohesive or very cohesive, with entanglement by stigmatic papillae and stylar trichomes. Entanglement by stylar trichomes is common in gynodioecious species. The synstigma arrangement did not correlate with phylogeny or breeding system. This study is the first to report a very loose synstigma in actively pollinated monoecious Ficus species. Our analyses revealed that, in Ficus, the synstigma is functionally analogous to an extra-gynoecial compitum. Comparative studies will be required to test further hypotheses about the evolutionary determinants of such variation.     

Morphological diversity of wing structure in Rhinolophoid bats (Chiroptera,Rhinolophoidea)

The results of studies on the morphological diversity of wing structure in horseshoe bats (Rhinolophoidea) are considered in relation to ecological differentiation within the superfamily. Various skeletal elements of the wing are shown to form several groups of mutually correlated characters. The main groups comprise the characters that account for the size of the wing and play a role in the formation of its outer contours. The distribution of characters shows that they describe different aspects of variation and can provide a fairly complete picture of the morphological and ecological structure of the superfamily. The results obtained by means of multidimensional scaling and clustering methods primarily reflect ecological types of bats and only then characterize their taxonomic relationships. Analysis of variation in structural features of the wing within the superfamily Rhinolophoidea shows that the same wing form in different families may be accounted for by different ratios of digit elements, primarily the lengths of distal and proximal phalanges of digits III and IV.