REPRODUCTIVE MORPHOLOGY OF QUERCUS (FAGACEAE)

Details of inflorescence, floral, and fruit morphology have been studied in more than 120 species of Asiatic and American Quercus. Of the two subgenera, subgenus Cyclobalanopsis has fewer species but greater diversity of reproductive morphology than subgenus Quercus. Some character states of subgenus Cyclobalanopsis, such as more numerous stamens, male flowers sometimes grouped in dichasia, abortive ovules well developed, prominent intrusive septae in the nut, and lamellate cupules, are shared with Lithocarpus. The diversity of cupular sizes, coverage, and ornamentation raises questions about the adaptive nature, ecological function, and phylogeny of the cupule, which clearly has by now evolved as a structure with its own qualities.     

ELEVATIONAL VARIATION IN FOLIAR FLAVONOIDS OF QUERCUS RUBRA L. (FAGACEAE)

Foliar extracts of high elevation Quercus rubra contain 20 major flavonol-3-0-glycosides based primarily on the aglycones myricetin, quercetin, and kaempferol. These compounds display an altitudinal cline in the Appalachian mountains, with quercetin-rich low elevation chemotypes intergrading into myricetin-rich high elevation forms. These chemotypes appear to be correlated with previously documented variation in foliar morphology. The degree of interpopulation variation also differs with elevation. At higher elevations flavonoids differ only quantitatively between sites, while below 3,000 ft there is site-to-site variability in the hydroxylation level of the aglycones.     

POSITIONAL AND SEASONAL VARIATION IN OAK (QUERCUS; FAGACEAE) LEAF MORPHOLOGY

Within-tree and seasonal variation in quantitative characters of oak leaves were evaluated by factorial analysis of variance. All linear and areal measurements illustrate marked within-tree and seasonal variation. Numbers of lobes and bristle tips and primary vein angle appear relatively stable within trees and among seasons. In many instances, size-correction reduces both within-tree and seasonal variance to nonsignificant levels. However, all characters do not illustrate the same trends either within trees or across the seasons. The results have important implications for those attempting to evaluate among-tree and among-population variation.     

LATE OVULE AND EARLY EMBRYO DEVELOPMENT IN QUERCUS GAMBELII

The ovary of Quercus gambelii is tricarpellary and trilocular; each locule contains two anatropous, bitegmic ovules. The formation of a caecum from a chalazal extension of the embryo sac was observed. A central resistant column of cells, which exhibit some continuity with the vascular trace supplying the ovule, remains protruding into the embryo sac from the chalaza until the later stages of embryo development. Early embryogeny is characterized by a nearly vertical first division with both of the derivative cells contributing to the building of the embryo proper. Such observations suggest that the embryogeny of Quercus should be placed in the Piperad or Asterad type rather than the Onagrad type as has been the practice.     

LIGNOTUBER ONTOGENY IN THE CORK-OAK (QUERCUS SUBER; FAGACEAE) I. LATE EMBRYO

Changes at the cotyledonary node of the cork-oak (Quercus suber L.) were examined during the embryo maturation phase using light microscopy and scanning electron microscopy techniques. During the maturation phase the embryo axis elongates by diffuse growth, the apical meristem forms the first leaf primordia, and the radicle meristem remains inactive. The primary axis of the embryo bears, axillary to the cotyledons, in the range of five to seven pairs of lateral buds at differing stages of development. Two or three pairs of these buds are visible, occurring on the upper unfused portion of the embryonic axis, while the remaining buds are hidden by the fused cotyledonary tissues. Lateral buds develop from clusters of cells in the peripheral meristem forming a shell zone delimiting the bud meristem. Lateral buds do not undergo much development until germination begins. The results are discussed with reference to the possible role of the cotyledonary node as the source of the lignotuber in the cork-oak.     

POLLINATION,FERTILIZATION AND OVULE ABORTION IN OXALIS MAGNIFICA

Pollination, fertilization and ovule abortion were studied in Oxalis magnifica (Rose) Knuth, a strongly self-incompatible herb that regularly matures only a fraction of its ovules. Examination of cleared ovules indicated that among 9 individuals the average number of ovules fertilized ranged from 48–92%. The remaining ovules either failed to produce female gametophytes, or more commonly contained unfertilized female gametophytes, despite large numbers of compatible pollen grains that were placed on stigmas. Abortion of fertlized ovules could be detected first by the flattened and enlarged appearance of the endosperm nuclei, followed by visible deterioration of the embryo. Among individuals the rate of embryo abortion varied from 3.4–47.9%. At lower levels of pollination an almost one-to-one relationship existed between the number of pollen grains placed on stigmas and the number of seeds matured in the capsule. No threshold number of pollen grains necessary for successful pollen tube growth and fertilization could be demonstrated. Reduction in seed number through embryo abortion provides an opportunity for selection among developing seeds. The potential for this form of selection varies widely among individuals of Oxalis magnifica, which showed a 14-fold variation in the average percentage of aborted ovules.     

LEAF GAS EXCHANGE IN QUERCUS MACROCARPA (FAGACEAE): RAPID STOMATAL RESPONSES TO VARIABILITY IN SUNLIGHT IN A TREE GROWTH FORM

Responses in net photosynthesis (A), stomatal conductance to water vapor (g), and leaf xylem pressure potential (ψ) were measured in the deciduous tree Quercus macrocarpa during alternating periods of sun (photosynthetic photon flux, PPF > 1,500 μmol m^-2 sec^-1) and shade (ca. 350 μmol m^-2 sec^-1 simulating cloud cover). Measurements were made on trees growing at the gallery forest-prairie edge on the Konza Prairie Research Natural Area in northeast Kansas. The region is near the westernmost extension of the range of Q. macrocarpa where this species experiences significant seasonal water stress (minimum ψ < -2.9 MPa). Quercus macrocarpa was chosen for study because it has relatively high A (15 μmol m^-2 sec^-1) and g (300 mmol m^-2 sec^-1) in contrast to the deciduous and evergreen subalpine trees previously studied. Both trees and large saplings of Q. macrocarpa responded to alternating several minute periods of sun and shade with relatively rapid changes in A and g. Reductions in g (110 mmol m^-2 sec^-1) during shade periods lowered transpirational water losses (E) by 13% (and reduced A by 5%) relative to estimates of A and E made assuming g remained constant. Partial stomatal closure during shade was correlated with moderate enhancement in ψ (0.31 MPa) in Q. macrocarpa. However, greater increases in ψ were measured in adjacent prairie grasses exposed to similar periods of shade (0.72 MPa in Andropogon gerardii, 0.61 MPa in Sorghastrum nutans). Reduced variability in ψ in tree growth forms may reflect greater buffering of water relations associated with the large size of trees, the amount of tissue devoted to water storage, and differences in hydraulic resistance relative to herbs. Nonetheless, the gas exchange and water relations responses in Q. macrocarpa were much more similar to those previously measured in herbaceous subalpine and grassland species than to those documented for subalpine trees. Thus, rapid gas exchange responses to variable PPF may also occur in tree growth forms.     

CONE AND OVULE DEVELOPMENT IN SCIADOPITYS (TAXODIACEAE-CONIFERALES)

Ontogeny of seed cones of Sciadopitys, with special reference to the ovule-supporting structure, is studied in material collected in Japan and Massachusetts. Cones are initiated as lateral or terminal structures in summer and complete the formation of most organs before winter. Bract development is well advanced before ovule-supporting structures are initiated. Continued cone development involves the formation of a narrow ridge of tissue in the axil of each fertile bract. This ridge develops a series of nine (but up to 12) apical lobes in centrifugal order, each of which is the primordium of a future tooth on the ovuliferous scale. Ovules are initiated as outgrowths of the adaxial surface of each lobe so that there is a one-to-one ratio between lobes and ovules. Intercalary extension of the ovuliferous scale itself (distally) and the common base of the bract and ovuliferous scale (proximally) greatly extends the complex. The ovuliferous scale eventually exceeds the subtending bract and its apex becomes recurved. Bracts each have a single trace, but each ovuliferous scale has a pair of traces that proliferate distally to irrigate ovule and scale lobe. Intercalary growth results in recurvature of the ovule trace. The organization of the cone is directly comparable with certain Permian fossils. Sciadopitys also seems unique within the Taxodiaceae in its centrifugal development of the ovule-supporting complex.     

OVULE AND EMBRYO DEVELOPMENT IN DORITIS PULCHERRIMA (ORCHIDACEAE)

The placental ridge began to proliferate 10 days after pollination. Megaspore mother cell underwent meiosis to form two dyads at first division. At 50 days two megaspores and generating dyad were formed by second division. The functional megaspore divided successively three times to form an eight-nucleate embryo sac at 60 days. Double fertilization occurred forming the zygote and endosperm initial cell. However, the endosperm initial cell degenerate soon thereafter. The zygote divided to form a terminal cell, the middle cell and suspensor initial cell at 70 days. The terminal and middle cells successively divided to form a multi-celled embryo up to 120 days after pollination. Histochemical study showed that the stainability of DNA, RNA and total proteins were almost constant during ovule and embryo development. Stainability of total carbohydrates decreased.     

ASPECTS OF CONE AND OVULE ONTOGENY IN CRYPTOMERIA (TAXODIACEAE)

The axillary complex of female cones of Cryptomeria is initiated as a tangentially extended triangular structure with a rounded apex. It is bilaterally symmetrical. Structures interpreted as prophylls are differentiated first, but they become insignificant in later development. They are succeeded by two successive pairs of lobes, each lobe being the common primordium for an adaxial ovule and a tooth. The ovule initially much exceeds the tooth. The apex of the complex has a diversity of fates and may differentiate as an ovule-tooth pair. A one-to-one relation between teeth and ovules may be lost by abortion of ovules. The initial relation between teeth and ovules is obscured in later development due to extension of tissues at the base of the complex associated with considerable enlargement of the teeth. Histogenesis of the various parts is described, together with the vascular system. There is a vascular supply to the tooth but not the ovule. The results support a direct comparison with the extinct transition conifers Pseudovoltzia and Aethophyllum but do not fully support Florin's generalized model for the arrangement of parts in the axillary complex of conifers.     

A NEW SPECIES OF BLACK OAK (QUERCUS,SUBG. ERYTHROBALANUS,FAGACEAE) FROM THE SIERRA MADRE OCCIDENTAL,MEXICO

Quercus mcvaughii is described as a new species of black oak (subgenus Erythrobalanus) from the Sierra Madre Occidental, in northern Durango and western Chihuahua, Mexico. It is most closely related to the more southern Q. crassifolia. Sessile or subsessile hairs, usually of different sizes, on the abaxial leaf surface distinguish Q. mcvaughii from Q. crassifolia, where hairs are similar in size and conspicuously stipitate. A key is provided for distinguishing similar species in the region. Intergradation of Q. mcvaughii with Q. crassifolia, Q. hypoleucoides, and Q. sideroxyla is reported.     

SPATIAL DISTRIBUTION AND DEVELOPMENT OF ROOT SPROUTS IN FAGUS GRANDIFOLIA (FAGACEAE)

Root sprouts around 31 Fagus grandifolia parent trees, some declining due to beech bark disease, were studied to describe the pattern of sprout distribution, the ecological importance of this pattern, and the relationship between sprout patterns and parent vigor. Microtome sections of roots were studied to determine the histological origin of sprouts. Sprout distribution was circular and usually centered on the parent tree. Most sprouts were within 8 m of the parent and remained attached to the parent root system even after the sprouts reached 10 yrs of age. Root sprouting in F. grandifolia may be effective in replacing dead parent trees, but the potential for clones to spread is limited. Spatial distribution of sprouts was mostly unaffected by tree vigor. Root sprouts originated from callus tissues associated with wounds on superficial woody roots.     

SYNCOTYLY IN QUERCUS ARIZONICA

An investigation was made concerning the gross morphology and the internal anatomy of Quercus arizonica embryos. It was found that the percentage of fused- and separate-cotyledoned embryos varies from tree to tree. Fusion of the cotyledons is congenital. Intermediate stages of fusion occur. The vascular pattern is the same in both fused- and separate-cotyledoned embryos. The number of cotyledonary traces varies in both types of embryos. The relationship of the single-cotyledoned embryo of Quercus to the origin of monocotyly is discussed.     

UNDERGROUND SYSTEMS OF GAMBEL OAK (QUERCUS GAMBELII) IN CENTRAL UTAH

Excavation to a depth of 1 m of a 3 × 4 m portion of a clone of Quercos gambelii revealed the presence of a massive underground system of lignotubers, interconnecting rhizomes and roots. Lignotubers comprised the greatest proportion (72%) of the total below ground biomass (81 t/ha). Lignotubers are distinctive in appearance: they are an enlarged stemlike structure with numerous clusters of adventitious buds on the surface. Anatomically, they are comparable to the above ground stems with growth rings. Lignotubers are lobed and distorted, giving the appearance of a burl. Rhizomes are round to I-beam in shape with a star-shaped pith, distinct annual rings, bud traces, and branch gaps. There were also clusters of adventitious buds on rhizomes, although not as dense as those on the lignotubers. Roots are oval in cross section with discernible growth rings, no pith, and no bud traces.     

西藏壳斗科的地理分布

在野外考察、分类清理和修订的基础上讨论了西藏壳斗科的地理分布。自然分布的西藏壳斗科植物,共３属３３种,集中分布于藏东南的河谷地带和喜马拉雅山脉的聂拉木县,印度栲、刺栲、喜马拉雅石栎和西藏石栎是这些地区海拔２００米以下群落建群种;通麦栎、俅江栎和薄片青冈是西藏海拔１８００－２５００米地段森林植物被的建群种;硬叶高山栎类则是海拔２５００米以上硬叶常绿阔叶林及高山灌丛植被的建群种。种的区系成分分析表明：     

OVULE INVERSION IN THE EARLIEST CONIFERS

Recent investigations of ovulate conifer cones from southern Europe and midcontinent North America have independently documented that certain Paleozoic walchians have inverted ovules, rather than the erect ovules previously thought to characterize the most primitive conifers. Reinvestigation and consideration of other walchian conifers, including Moyliostrobus and Lebachia piniformis (sensu Florin), reveals that they also had inverted ovules. These different patterns of ovule orientation demonstrate that the nature and the polarity of the character states are dramatically different than popularly believed, and the shift from megasporophyll to ovuliferous cone-scale occurred within the Paleozoic walchians.     

STUDIES IN THE QUERCUS UNDULATA COMPLEX. IV. THE CONTRIBUTION OF QUERCUS HAVARDII

Scrub oak populations in the semidesert area of northeastern Arizona and southeastern Utah are ordinarily identified in regional manuals as Quercus undulata. They are very similar, both morphologically and ecologically, to Q. havardii of the Staked Plain of the Texas Panhandle and southeastern New Mexico. They differ, however, in a number of inconspicuous characters. Population sample analyses indicate that most of these differences are suggestive of Q. gambelii, and the deviant populations are thus interpreted as having been derived from ancestral Q. havardii through introgression by Q. gambelii. Two differences are not in accord with this interpretation; these are regarded as possible cases of transgressive segregation. Considering the evolution of these hybridized populations, it is speculated that the ancestral Q. havardii occurred to the south and west of the present range of this species during the Kansan period of the Pleistocene. During subsequent northward dispersal, it became split in two. The eastern portion ultimately came to occupy the present range of the species in the Staked Plain; the western portion—lying to the west of a north-south mountain barrier in central New Mexico—became introgressed by Q. gambelii (and locally by Q. turbinella), resulting in the present populations of Arizona and Utah.     

FIBER INITIATION ON THE COTTON OVULE (GOSSYPIUM HIRSUTUM)

Cotton ovules at the stage of fiber initiation were studied with a scanning electron microscope. On the day before anthesis the anatropous ovule had many anomocytic stomata, especially on the chalazal end. At anthesis, fibers first appeared at the crest of the funiculus and then around the lateral circumference of the ovule. Fiber initials were delayed for a few hours at the chalazal cap and for 3 or 4 days at the extreme end of the micropylar region. The morphological differentiation of a fiber began when an epidermal cell rounded up and protruded. After a brief period of diametric expansion, the initial began elongation toward the micropylar end. Between 2 and 3 days of age the fibers segregated into small groups, developed tapered tips, and began spiral growth. Fiber density was about 3,300 fibers per mm², and the ratio of fiber initials to total epidermal cells was 1:3.7 at anthesis.     

TRIGONOBALANUS (FAGACEAE): TAXONOMIC STATUS AND PHYLOGENETIC RELATIONSHIPS

The fagaceous genus Trigonobalanus as recently treated includes 3 species, two in Malaysia and Southeast Asia and a single species in Colombia, South America. Character analysis suggests that the genus as currently circumscribed is paraphyletic, without synapomorphies to unite the three species. Each of the three species is a morphologically distinct relict of a group that probably was ancestral to the modern genera Quercus and Fagus. Each of the three species also has at least one autapomorphy which is unique within Fagaceae. Analysis of cupule morphology in Fagaceae provides an interpretation of evolution in cupules which differs substantially from Forman's interpretation. We interpret trigonobalanoid cupules as indicative of an ancestral type of inflorescence within Fagaceae. This inflorescence type is a dichasial structure in which the outermost axes are cupular valves, but the degree of branching and subsequent number of fruits are variable. Following this model, a strict relationship exists between valve number and fruit number as seen in cupules of Trigonobalanus (valves = fruits + 1). Fossil evidence is consistent with our interpretation of the phylogenetic position of the trigonobalanoids. We propose to segregate the three species of Trigonobalanus as three monotypic genera; two of these require names which we provide here: Formanodendron and Colombobalanus.