Nuclear DNA variability withinPisum sativum (Leguminosae): Cytophotometric analyses

The cultivars or experimental lines ofPisum sativum were analyzed cytophotometrically for nuclear DNA content of early prophases after ethanol-acetic acid fixation. Wide variability was found (from 3.93 to 5.07pg per haploid nucleus). This result was confirmed by the cytophotometric analysis of interphase nuclei isolated from leaf tissues fixed in formalin. Analysis of interphase nuclei at different thresholds of optical density showed that certain chromatin fractions are involved in the variations.     

Taxonomic and functional implications of stigma morphology in species ofCassia,Chamaecrista, andSenna (Leguminosae:Caesalpinioideae)

Two stigma forms occur inChamaecrista andSenna, but only one inCassia. In the common chambered form, a stigma pore is positioned on the reflexed style tip and is the entrance to a tapering chamber. The pore rim is fringed by hairs which vary in number, size, distribution and shape. In the alternative form the stigma is situated at the apex of the curved style and is crateriform. The crater rim is fringed by hairs of variable number and shape. The stigmatic hairs are predominantly unicellular and cutinized. Stigma and hair differences aid in the taxonomy of the genera. Their functions in pollination biology are discussed.     

Survey of leaf anatomy,especially secretory structures,of tribeCaesalpinieae (Leguminosae,Caesalpinioideae)

We studied leaflet anatomy, emphasizing secretory structures, from herbarium specimens of 128 species of 44 genera of tribeCaesalpinieae, using clearings, resin sections, and scanning electron microscopy. These observations, combined with those from our three earlier papers, provide a survey of 210 species representing all genera. Seventy-three species had secretory structures: 21 had glands or gland-like trichomes, 40 had living mesophyll idioblasts, and nine had cavities (three species each had two different types). Five additional species, all inCercidium (Caesalpinia group), had paired or clustered large spheroidal, thick-walled, empty cells (veinlet idioblasts) interconnected by perforation plate-like gaps. Secretory structures have systematic significance at various taxonomic levels.     

Leaf anatomy inCaesalpinia andHoffmannseggia (Leguminosae,Caesalpinioideae) with emphasis on secretory structures

Leaflets of 65 species ofCaesalpinia s.l. and seven species ofHoffmannseggia were studied in clearings supplemented by resin sections and scanning electron microscopy. Three types of secretory structure occurred among 46 species; in 43 species they were distributed mutually exclusively (external glands: 8 species; internal cavities: 5 species; idioblastic cells: 30 species); three other species each had two types. Species with secretory structures conform mostly to proposed subgenera and informal groups. Other unusual features were external glands with internal spaces, thickened walls or conspicuous localized wall thickenings in epidermal cells or mesophyll cells of certain species, and differentially stained epidermal cells surrounding stomata. Prismatic crystals predominate but druse crystals also occur.     

Investigation and documentation of hybridization betweenParkinsonia aculeata andCercidium praecox (Leguminosae:Caesalpinioideae)

Morphometric, cytogenetic, geographical and ecological evidence for hybridization betweenParkinsonia aculeata andCercidium praecox is presented. Morphometric investigation using the character count procedure and cytogenetic observations confirm hybrid status. All diagnostic morphometric characters were intermediate in the hybrid. Both parents (2n = 28) show regular tetrad formation and pollen fertility greater than 94%. Hybrids have a chromosome number of 2n = 28 or 2n = 30, and display meiotic abnormalities including lagging chromosomes and micronucleus formation; less than 21% of hybrid pollen was fertile. Ecological and geographical information suggests that hybridization is occurring at increasing frequency due to the expanding range ofP. aculeata associated with cultivation as an ornamental, coupled with ecological disturbance and weediness, and the cultivation ofC. praecox and hybrids as fodder, ornamental and shade trees. Hybrid fertility and phenological observations, in conjunction with F-weighted principal component analysis, suggest that the progeny of F₁ hybrids are established. The hybrid is formally described asP. ×carterae.     

Patterns of fruit and seed production inBauhinia ungulata (Leguminosae)

Patterns of seed and fruit production ofBauhinia ungulata, a small tree legume indigenous in tropical America, were studied in Costa Rica. Only about 8% of flowers produced fruits. The average pod had 19 ovules and about two thirds of these began seed development, with mature pods containing an average of 9.7 mature undamaged seeds. About half of the mature pods were damaged by herbivores and within these, 27% of ovules or seeds had been eaten. Among trees there was no significant variation in pod production, but the number of ovules per pod and seed production per pod varied significantly. Within infructescences most pods were retained at middle positions. Within pods, the probability of an ovule developing into a seed increased toward the distal end. The pattern of seed and fruit production in this species agrees well in general with that reported for other neotropical legumes. The abortion of seeds and fruits can be regarded as a way of controlling maternal investment, and as a response to herbivory.     

Karyotypic and chloroplast genomic diversity inMedicago sect.Lupularia (Leguminosae)

Studies were made on the chromosome complements and chloroplast genomes ofMedicago lupulina andM. secundiflora, which comprise sectionLupularia ofMedicago. Both types of analyses indicated more substantial differences between these species than suggested by external morphology.Medicago lupulina has a relatively asymmetrical karyotype in terms of centromeric position and relative length. The karyotype ofM. secundiflora is comparatively more asymmetrical in centromeric position and reduced in absolute size but exhibits greater symmetry in relative length. The restriction endonuclease fragmentation patterns of the chloropiast DNA of these two species (with Bam HI, Eco RI, Bgl II, and Xho I) show little similarity, with only 17% of the fragments matching in size. The lack of interspecific congruence among data of morphology, karyology and cpDNA inLupularia is contrary to consistency exhibited among these data inMedicago subsect.Intertextae.     

A phylogenetic analysis ofLeucaena (Leguminosae: Mimosoideae)

Chloroplast DNA restriction fragment length polymorphisms have been used to reconstruct the maternal phylogeny of all the known taxa in the small neotropical legume genusLeucaena. Three major plastome clades were recognized, but these did not conform with relationships between the taxa proposed on other characters from morphology, cytology or hybridization. The maternal parentage of tetraploids within the genus has been proposed. Evidence for introgression was found between diploidL. diversifolia and tetraploidL. diversifolia. The implications of these results for the origin of the cultivated taxa are discussed.     

Phylogenetic relationships in the genusStylosanthes (Leguminosae) based upon chloroplast DNA variation

A detailed analysis of chloroplast DNA restriction fragment length variation was undertaken to reconstruct the maternal phylogeny of 18 taxa from both sections of the papilionoid tropical forage legume genusStylosanthes. Data were analysed by means of the computer program PAUP, using an heuristic search with Wagner parsimony. The resulting cladogram dividedStylosanthes into four separate clades, which comprised: (i) theS. guianensis complex and related species (i.e.S. gracilis, S. grandifolia andS. montevidensis); (ii)S. hispida, tetraploidS. hamata s. l.,S. sympodialis, S. humilis, S. leiocarpa, S. angustifolia and certain accesions ofS. scabra; (iii)S. calcicola, S. viscosa, diploidS. hamata s. str., andS. fruticosa, plus accessions ofS. scabra, S. capitata and one accession ofS. grandifolia; and (iv)S. macrocephala and other accessions ofS. capitata not included within clade 3. Results are generally congruent with previously established interspecific relationships and, moreover, enabled identification of putative maternal progenitors for four tetraploid taxa:S. humilis was identified as a likely maternal parent of bothS. sympodialis andS. hamata s. l.,S. viscosa as a maternal parent ofS. scabra, andS. macrocephala as a maternal parent ofS. capitata.     

Cytotaxonomic studies of Eastern MediterraneanVicia species (Leguminosae)

Collected material of rare and newVicia spp. was investigated from a cytotaxonomic point of view. Nineteen species were examined in total. The study includes 14 novel chromosome counts and measurements of DNA amount, as well as a comparison of chromosome morphology between species. The results of the cytological study support to an extent a recent taxonomical revision of subgenusVicia. To whom reprint requests should be addressed.     

Allozyme variation and phylogeny in annual species ofCicer (Leguminosae)

Allozymic variation at 30 isozyme loci was examined electrophoretically in nine annual and one perennial species ofCicer. While most of the accessions examined were monomorphic, species can be differentiated on the basis of their enzyme phenotypes. Several groups of species were identified based upon genetic distance values. For example,C. arietinum, C. reticulatum, andC. echinospermum shared the same alleles for most of the loci exmained. PerennialC. anatolicum is also closely related to this group. Similarly,C. judaicum, C. bijugum, andC. pinnatifidum formed another group. Two annual species,C. chorassanicum andC. yamashitae clustered together, whereasC. cuneatum was the most distantly related species. Correlations were found between genetic distances and geographic distribution. Results from enzyme electrophoresis tend to support the previously reported taxonomic treatments based upon crossability and morphological similarity. However,C. yamashitae, which has been classified in the second crossability group, is quite distinct genetically and morphologically from the remaining species of the group. An isozyme gene duplication observed in the genus suggested the monophyletic origin of the species examined in the present study.     

Breeding systems and pollination inVigna minima (Leguminosae,Papilionoideae)

Four types of floral breeding systems—(i) chasmogamy, (ii) aerial pseudocleistogamy, (iii) subterranean pseudocleistogamy and (iv) obligate subterranean true cleistogamy—are observed in the populations ofVigna minima inhabiting the Western Ghats (India). Five categories of phenotypes are recognized based on the number and kinds of floral breeding systems found in a given individual. The frequencies of different categories of phenotypes not only show intra- and interpopulation variation, but also fluctuate from generation to generation suggesting differences in the genetic structure of populations. This polymorphism in the breeding system of a single species is unique and may be adaptive. Obligate subterranean true cleistogamy and amphicarpy appear to be adaptations to jungle fires and soil erosion.—The flowers are of the flag-blossom type and insect visitors act as tripping agents. The tripping mechanism together with the polymorphic floral breeding system result in a balanced mixture of selfing and outcrossing. Such a recombination system may enhance the fitness ofV. minima which is essentially a colonizing species.     

Systematics and randomly amplified polymorphic DNA in the genusLeucaena (Leguminosae,Mimosoideae)

Randomly amplified polymorphic DNA (RAPD) was used to examine genomic diversity in taxa of the neotropical legume genusLeucaena. Data were analysed using both similarity- and parsimony-based approaches and the data compared to a parsimonybased analysis of chloroplast DNA restriction fragment length polymorphisms (RFLP). Distance-based methods of RAPD analysis produced groups inconsistent with those identified by RFLP analysis. Parsimony-based analysis of the data produced groupings largely consistent with those identified using RFLPs. The major differences were grouping of the two subspecies ofLeucaena diversifolia (subsp.diversifolia and subsp.stenocarpa) in the RAPD tree, but their separation in the RFLP tree. The value of RAPD data in systematics as a result of these data and our understanding of the molecular basis of RAPDs are discussed.     

Pollen-ovule patterns in tribeTrifolieae (Leguminosae)

Relative pollen and ovule production in the genera of the legume tribeTrifolieae is explored particularly as to howMedicago with its explosive pollination mechanism compares with its allies.Medicago produces much larger, although much fewer pollen per ovule than the other five genera in the tribe; this is interpreted as a consequence of its highly specialized, irreversible pollination mechanism, which allows only one effective exchange of pollen with pollinators.Melilotus andTrifolium produce a comparatively large quantity of pollen; this can be related to their floral characteristics requiring abundant pollen to achieve fertilization. InMedicago andTrigonella, annuals convert a higher proportion of pollen grains and ovules into seeds than perennials.     

Adventitious roots inGlycine subg.Glycine (Leguminosae): Morphological and taxonomic indicators of the B genome

Adventitious roots were observed on 3 wild perennialGlycine species, in short-poddedG. clandestina, G. latifolia and mostG. tabacina (2x, 4x, 6x), while other species lacked adventitious roots. This suggests that the adventitious roots trait is associated with B genome species. Intra- and interspecific F₁ hybrids reveal that adventitious roots apparently are inherited recessively. The presence of adventitious roots or short-poddedG. clandestina, coupled with infertility with longer-poddedG. clandestina, and enzymatic and leaflet morphology differences between the twoG. clandestina subgroups, supports segregation of the short-podded form as a separate taxon.     

Pollination-related characteristics in the mimosoid legumeAcacia terminalis (Leguminosae)

Intraspecific variation has been found for several pollination-related characteristics in two isolated populations of the self-incompatible treeAcacia terminalis: floral characteristics including colour and flowering time; style length; size and colour of extrafloral nectaries on the leaf petioles; chemical components of the extrafloral nectar; different taxa of bee pollinators; and frequency differences in bird pollinators. These differences possibly reflect the evolution of two different pollination syndromes within this species.     

Patterns of endopolyploidy and 2C nuclear DNA content (Feulgen) inScilla (Liliaceae)

The Feulgen-DNA content of 3558 nuclei from 21 different tissues and organs ofScilla decidua (Liliaceae) was measured by a scanning cytophotometer interfaced to a computer. The basic nuclear DNA content (2 C value) was 13.62 pg, and 71 per cent of the nuclei were polyploid. The highest DNA values were found in the antipodal cells of the ovule, and the elaiosomes of the seeds (512 C). In addition to polyploidy, the 2 C values exhibited tissue-specific variation which was statistically significant (0.05% level of probability), It is suggested that differential DNA replication and endopolyploidization may be basic factors in the complex mechanism of cell and tissue differentiation.Dedicated to Professor Dr.Lothar Geitler in honour of his 80th birthday.     

The characterisation and identification of a naturally occurring hybrid in the genusLeucaena (Leguminosae: Mimosoideae)

Phytogeographical, morphological, and molecular evidence for the widespread but sporadic occurrence of sterile hybrids betweenLeucaena leucocephala subsp.glabrata andL. esculenta subsp.esculenta in South-Central Mexico is presented. Most morphological and DNA characters studied in the putative hybrids showed states intermediate between the proposed parental taxa. The occurrence of non-additive nuclear ribosomal DNA phenotypes is discussed and the need to use a suite of nuclear taxon-specific markers to determine hybridity is emphasized. The origin of the hybrid is discussed in relation to the disruption of the distributions of both parental taxa through use by man as minor food plants, providing another example of the important influence of human interference on the evolution ofLeucaena. The successful use of dried leaf material as a source of DNA is highlighted as an efficient way to identify sterile hybrids at the molecular level.     

Reproductive biology ofCaesalpinia calycina andC. pluviosa (Leguminosae) of the caatinga of north-eastern Brazil

The pollination biology, breeding system and fruiting success ofCaesalpinia calycina andC. pluviosa var.sanfranciscana were studied in caatinga vegetation in Bahia, NE Brazil. The principal pollinators for both species were carpenter bees.Caesalpinia calycina is andromonoecious but inC. pluviosa all flowers are hermaphrodite. InC. calycina all selfed flowers were abscised within 72 h despite rapid self-pollen tube growth to the ovary and ovule penetration. Prevention of selfing therefore seems to be controlled by a post-zygotic mechanism. Both species had very low fruit-set and it is suggested that this is at least in part due to geitonogamous pollinations with ovule penetration by self pollen tubes.     

Isozyme variation inFaidherbia albida (Leguminosae, Mimosoideae)

Genetic variation has been assessed in 30 populations (931 families) ofFaidherbia albida (Leguminosae, Mimosoideae) from across its entire African range, using six isozyme loci identified by five enzyme systems. Among the populations studied a null allele was proposed to explain the absence ofLap-1 activity in populations from southern and eastern Africa. The mean percentage of polymorphic loci per population, the mean number of alleles per locus and the mean genetic diversity within populations were 31.7%, 1.6 and 0.127 respectively. Genetic diversity was greatest in populations from West Africa and lowest in populations from eastern/southern Africa, with Ethiopian/Sudanese populations intermediate. The overall degree of genetic differentiation between populations (G_ST) indicated that approximately 56% of the enzyme variation resided within populations. Clustering of Nei's unbaised genetic distances calculated between all populations produced a dendrogram that generally followed the geographic distribution of the populations. Two major groups were identified that may be considered the eastern/southern African and the Ethiopian/West African clusters. Within the Ethiopian/West African cluster two subclusters could be recognised, one broadly corresponding to those populations from Ethiopia/Sudan and the other to those populations from West Africa. The implications of these results for theories regarding the origin ofF. albida in Africa are discussed.