摘要:

Spores of the fernsAnemiaandMohria(Schizaeaceae) andCeratopteris(Pteridaceae) are surveyed with light microscopy and scanning and transmission electron microscopy. In each genus the spores are trilete with radially symmetrical exine sculpture comprising three sets of parallel or near‐parallel muri.Anemiahas six spore types. One is reticulate(A. wrightii‐type), and the other five types have either cicatricose or canaliculate sculpture that reflect a basic form, i.e., three mural sets that have mutual anastomoses in each radial region. The cicatricoseA. mexicana‐and the canaliculateA. dregeana‐types represent the simplest expressions of this pattern. Specializations include cicatricose, auriculate(A. raddiana‐type) and canaliculate, ornate(A. oblongifolia‐, A. phyllitidis‐types). Exine structure is homogeneous or differentially microporate; the enveloping two‐layered perine has granulate structure and a granulate to spiculate and/or pitted surface.Mohriaspores have a stratified, granulate to rugulose perine and cicatricose exine sculpturing consistent with theA. mexicana‐type pattern, but the muri are hollow. The canaliculate spores ofCeratopterisdiffer from thoseof AnemiaandMohriain that the three mural sets are discrete and separated from each other by a stria in each radial region; exine structure is homogeneous and the thin perine is granulate. WithinAnemiatheA. raddiana‐type is exclusive to subgen.Coptophyllumand theA. oblongifolia‐andA. phyllitidis‐types to subgen.Anemia.Three spore types are shared by two subgenera; i.e.,A. wrightii‐andA. mexicana‐types inCoptophyllumandAnemirhiza, and theA. dregeana‐type inAnemirhizaandAnemia.Spore polymorphism is indicated in several species of subgen.Anemia, and smooth immature spores are recorded from all three subgenera.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb15194.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

Maternal and paternal effects on seed size and reproductive success (RS) were studied in a subarctic population ofBartsia alpinaL. (Scrophulariaceae), a hemiparasitic perennial herb forming dense clones in open habitats. The impact of environmental factors was assessed in fertilization and defoliation experiments, and gender specialization of individual genets was investigated in a series of diallel experiments (reciprocal crossings) in the field. Maternal effects on seed weight were much larger than paternal effects, and seed weight was also strongly influenced by resource availability (especially nitrogen). The highest seed weights were usually found when genets were associated withAstragalus frigidus, which seems to be the optimal host species in the population, but similar results were achieved with NPK (nitrogen‐phosphorus‐potassium) fertilization. Defoliation experiments revealed an innate minimum seed weight, below which seed number was affected by resource deprivation. The reciprocal crossing program indicated a high level of gender specialization in individual genets (clones), ranging continuously from almost pure males to almost pure females. Early‐flowering genets showed the highest average male RS, whereas female RS increased in late‐flowering genets. Phenological separation of the genets into ‘early’ and ‘late’ revealed an inverse correlation between male and female performance. Numerous characters contributing to phenotypic gender were measured in the genets, but these characters and functional gender calculations from the diallel experiment were only weakly correlated. It is concluded that simultaneous measures of both male and female RS are needed for a reliable assessment of gender variation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb15195.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

The genusTriticumincludes several polyploid species that arose due to hybridization between two or more diploid species. SectionSitopsisis comprised of five diploid species given the genome designation S. Four polyploid species are recognized that contain an S or S‐derived genome. We have used two repetitive DNA sequences found primarily in the S genomes ofTriticumto determine the likely diploid progenitors of the polyploid species. Comparison of restriction fragments that hybridize to probes for these sequences suggests thatT. speltoidesis distinct from other members of sectionSitopsis(i.e.,T. longissimum, T. bicorne, T. searsii, andT. sharonense).The S‐derived genome ofT. aestivumis more closely related toT. speltoidesthan to the otherSitopsisdiploids. The restriction fragment pattern ofT. timopheeviiis 98% identical to that ofT. speltoides, while those ofT. kotschyiandT. syriacumare identical to the group of diploids represented byT. longissimum, T. bicorne, T. searsii, andT. sharonense.Our results are compatible with previous molecular and biochemical data regarding relationships amongTriticumspecies containing an S or S‐derived genome.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb15196.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

InCleistes divaricata, a hinged anther dispenses a sequence of loosely aggregated pollen tetrad masses onto the dorsal thorax ofBombusandMegachileworkers. This mechanism allows more than one bee to receive pollen from a single flower. To determine the effectiveness of this strategy, plants in bud were caged and hand pollinated using pollen from sequential releases. Capsules produced from a flower's first three pollen dumps were significantly larger and heavier and contained more seeds than those produced by later pollen deposits with fewer tetrads. Decreasing pollen dosage did not affect fruit set, capsule development, individual seed weight, or percentage of healthy looking embryos per fruit. Fruit set for artificial pollinations was 93% for pollen dumps 1–3 and 97% for dumps 4–18. As set of naturally pollinated marked plants was only 38%, low frequency of pollinator visits apparently limited seed production. Efficacy of infrequent visits is maximized, however, because a flower's first pollen releases contain the most pollen, but later low‐dosage dumps can produce some seeds. An unexpected cost was a higher investment of pericarp per seed in low‐dosage capsules (130 ng pericarp seed‐1fresh weight) than in high‐dosage pollinations (only 27 ng pericarp seed–1). Flower fading in plants receiving low pollen dosage was as slow as that in caged, unpollinated controls, thus increasing opportunity for additional pollination.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb15197.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

Data are presented on the mechanical consequences of dehydration for the petioles of two monocots and two dicots differing in leaf morphology (pinnate leaves ofChamaedorea erumpensand simple leaves ofSpathiphyllum‘clevelandii‘; pinnate leaves ofAcer negundoand simple leaves ofA. saccharum).The flexural stiffness EI of petioles decreased over a broad range of tissue water potential (– 10<ψw<– 50 bars). Within the same range of ψ, the second moment of area I and the elastic modulus E were observed to decrease and increase, respectively. However, the mechanical alterations ofChamaedoreaandA. negundopetioles were significantly less than those observed forSpathiphyllumandA. saccharumpetioles. The increase in Eof SpathiphyllumandA. saccharumpetioles attending dehydration was linearly correlated with an increase in the relative volume fraction of tissues with lignified, thick cell walls (“support tissues”). The decrease in Iof SpathiphyllumandA. saccharumpetioles was linearly correlated with a decrease in the relative volume fraction of tissues with nonlignified, thin cell walls (“ground tissues”). Similar trends were observed for the petioles ofC. erumpensandA. negundobut were found not to be statistically significant. Anatomical differences in the relative volume fraction and spatial locations of support tissues in the petioles of these four taxa appear to account for the differences observed in the mechanical consequences of petiole dehydration.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb15198.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

The root apical meristem ofAsplenium bulbiferumForst. f. has a prominent four‐sided pyramidal cell with its base in contact with the rootcap. Derivatives (merophytes) that contribute to the main body of the root are produced from the three proximal faces of the apical cell. The rootcap has its origin from the fourth (distal) face of the apical cell. The first division in a proximal merophyte is periclinal to the root surface, separating an outer cell and an inner cell. The outer cell is the origin of the outer part of the cortex and the epidermis; the larger inner cell is the origin of the inner cortex, endodermis, pericycle, and vascular tissue. After the establishment of the basic number of cells in a unilayered merophyte, the cells undergo transverse divisions forming longitudinal files of cells. The mitotic index of the apical cell indicates that it is not a quiescent cell. Also, the first plane of division in a newly formed merophyte dictates that the apical cell is the originator of merophytes.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb15199.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

Sex expression (the proportions of hermaphrodite and staminate flowers produced) of the andromonoecious speciesSolatium hirtumis labile, and this lability of whole plant sex expression is due to labile sex expression of individual floral buds. In this paper I examine the developmental processes that underlie the differences in floral sex expression of hermaphrodite and staminate flowers ofSolarium hirtum, focusing particularly on the processes responsible for the observed lability of floral sex expression. Differences in bud growth rate and relative growth of floral organs in these buds are evident at about the time of megasporocyte meiosis (11–12 days before anthesis). However, gynoecial sterility in staminate buds does not occur until just 6–7 days before anthesis. At this time, abnormalities in ovule development occur in staminate buds: the ovules begin to appear necrotic, the integumentary tapetum collapses, and the megagametophytes of many ovules cease normal development. These observations are consistent with the predictions of labile floral development.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb15200.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

Plants may respond to developmentally or environmentally induced changes in the relationship between source (assimilate exporting) and sink (assimilate importing) organs through a number of regulatory mechanisms. The purpose of this work was to describe responses in leaf physiology, organ biomass partitioning, and reproduction ofBrassica campestrisL. to altered sink‐source relations. Partial defoliation early in ontogeny increased sink‐source ratio after 1 day and was accompanied by a significant increase in area‐based photosynthetic capacity. Assimilate was preferentially partitioned to new leaf tissue at the expense of stem and reproductive tissue so that sink‐source ratio and photosynthesis returned to control levels within a week. Bud excision at flower initiation decreased sink‐source ratio; plants in this treatment responded through altered biomass partitioning, but there were no detected changes in leaf physiology. Plants that were hand‐pollinated had decreased specific leaf weight, and within a week, sink‐source ratio increased. Plants that were pollinated and then completely defoliated produced 40% as many seeds as plants that were not defoliated, presumably through stem and/ or fruit photosynthesis, and at the expense of flower production. Together these results illustrate that regulation of sink‐source relations can occur through complex responses at several levels of organization over a wide range of time scales.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb15201.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

Early events in the evocation of the flower inPharbitis nilChois seedlings were investigated by following the incorporation of tritiated uridine into the shoot apex. The uridine was applied to the expanded cotyledons of seedlings at 8 hr into the inductive dark period. The shoot tips were fixed at 20 hr (a 12‐hr labeling period). After the 12‐hr labeling period there was considerable label throughout the shoot tips of both control plants (dark period interrupted with 5 min of red light at 8 hr) and plants induced to flower. Both RNase and acid hydrolysis removed the nonexchangeable label and the Azure B staining, thus leading to the conclusion that the uridine was incorporated into RNA. Induction in the cotyledons was followed quickly by an increased synthesis of RNA in the rib meristem region of the receptor bud at the time when the floral stimulus is assumed to be arriving. The increase in RNA synthesis is revealed by an increase in the rib meristem/central zone ratio of counts due to the incorporation of tritiated uridine. A comparison of counts in each of the two regions revealed that the change in ratio was due to an increase in the rib meristem and not due to a decrease in the central zone in induced shoot apices. The initial activation of the rib meristem probably occurred by 16 hr from the beginning of the dark period. Tendencies in the literature to disregard the role of the rib meristem in giving rise to part of the flower are discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb15202.x

出版商:Wiley    

年代:1991

数据来源: WILEY

摘要:

Marshallia mohriiis a tetraploid species, 2n =4x =36, with approximately 17% of its pollen mother cells exhibiting a single quadrivalent at diakinesis of Meiosis I. The species is morphologically most similar toM. grandiflora, a member of the Grandiflora complex along withM. mohriiandM. trinervia.These data led to the preliminary hypothesis thatM. mohriioriginated by autopolyploidy. However, we rejected the autopolyploid hypothesis because the number of quadrivalents observed in 93 cells is significantly less than predicted by the Jackson‐Casey‐Hauber model for autotetraploids that have zero to two chiasma per pachytene bivalent. Enzyme electrophoresis was used to test the alternative hypothesis of allotetraploidy and to determine possible diploid progenitor(s). Eleven enzymes encoded by 25 loci were resolved for the three species in this complex.Marshallia mohriiexhibits fixed heterozygosity for the polymorphic loci. The diploid species possess three duplicated loci, one for isocitrate dehydrogenase and two for phosphoglucose isomerase. Of sixteen alleles among the polymorphic loci inM. mohrii, one allele (for Tpi‐1) is also found inM. trinervia, and three alleles (one each for Tpi‐1, Tpi‐2, and Lap) are found inM. grandiflora. Marshallia mohriialso possesses one allele each at Idh‐1, Idh‐2, Pgi‐4, and two each at Me and Mnr that are not shared with either of the two diploid species analyzed in this study. The cytogenetic and electrophoretic evidence suggest an allotetraploid origin ofM. mohrii, possibly involvingM. grandiflora, M. trinervia, and a third species. Inferences about ancestry are difficult because of the paucity of qualitative allozyme divergence among the diploids and because of the number of high frequency alleles inM. mohrii, not found in eitherM. grandifloraorM. trinervia.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1991.tb15203.x

出版商:Wiley    

年代:1991

数据来源: WILEY