VARIATION IN SEX ALLOCATION AND FLORAL MORPHOLOGY IN IPOMOPSIS AGGREGATA (POLEMONIACEAE)

Intrapopulational variation in biomass allocation to male vs. female function was quantified for the hermaphroditic plant Ipomopsis aggregata in terms applicable to sex allocation models. The proportions of flower biomass put into the corolla and calyx averaged 0.59 and 0.20 and were relatively constant across plants. The proportions in the stamens and pistil averaged 0.13 and 0.08, with considerable variation among plants. Phenotypic gender at the time of flowering ranged from 0.34 to 0.77 female. Pistil dry weight was correlated with stigma exsertion. Stamen weight was correlated with corolla width, which influences male pollination success, and was also correlated with anther position and pollen production. Female reproductive success as estimated by seeds per flower showed no detectable relationship with initial allocation of biomass at the time of flowering, but decreased in accelerating fashion with the proportion of final biomass including seeds that was allocated to male function.     

GENETIC AND ENVIRONMENTAL VARIATION IN FLORAL TRAITS AFFECTING OUTCROSSING RATE IN CLARKIA TEMBLORIENSIS (ONAGRACEAE)

Clarkia tembloriensis exhibits a wide range of variation among its natural populations in outcrossing rate and in separation of male and female function in space (anther-stigma separation or herkogamy) and in time (protandry). Here we show that outcrossing rate is highly correlated with protandry and anther-stigma separation. Both genetic and environmental variation contribute to inter- and intrapopulation variation in protandry and anther-stigma separation. Interpopulation differentiation for protandry and anther-stigma separation was found to be polygenic. Genetic variation for protandry and anther-stigma separation within populations was demonstrated by a significant among-family variance in two populations with contrasting breeding systems. Environmental effects on the expression of mating system traits were manifested in two ways. First, significant variation among lathhouse benches suggests that small-scale environmental heterogeneity may affect the development of floral traits. Second, protandry was shortened under hot summer conditions. Hence, hotter and drier habitats, typical of the more self-pollinating populations of C. tembloriensis, can promote self-pollination purely through environmental effects.     

VARIATION IN MALE AND FEMALE REPRODUCTIVE SUCCESS AMONG FLORAL MORPHS IN THE TRISTYLOUS PLANT LYTHRUM SALICARIA (LYTHRACEAE)

The purpose of this study was to assess variation in male and female reproductive success among the three morphs of the tristylous plant, Lythrum salicaria. Fluorescent dyes were used as pollen analogs to determine whether morphs differ in their abilities to donate and receive pollen, and actual and potential seed set was measured with a hand pollination experiment. Dye transfer among morphs was highly asymmetric, with more frequent transfer from the short-styled morph to the long- and mid-styled morphs. This suggests that shorts are performing better at pollen donation and longs and mids are performing better at pollen receipt. All flowers on 95 plants were hand pollinated to test whether female reproductive success is more pollen-limited in the short-styled morph than in other morphs. Hand-pollinated short-styled plants had significantly higher total seed mass and more seeds per capsule than short controls, whereas hand pollination failed to increase seed set in long and mid morphs. As predicted, short-styled morphs showed significant pollen limitation, whereas seed set in long- and midstyled morphs was not pollen-limited. Thus, in Lythrum salicaria asymmetrical pollen flow generates morph-specific differences in male and female fitness.     

FLORAL CORRELATES AND FITNESS CONSEQUENCES OF MATING-SYSTEM VARIATION IN TURNERA ULMIFOLIA

Outcrossing rates varied from 0% to 69% among Jamaican populations of Turnera ulmifolia. A correlation between increasing herkogamy and outcrossing rate occurred among populations. Predictions from sex-allocation theory were tested by estimating allocation to reproductive functions. Significant differences in allocation patterns occurred among populations, but they were not correlated with outcrossing rates. The fitness consequences of inbreeding were assessed in high- and low-density greenhouse experiments for nine populations with variable outcrossing rates. No evidence for inbreeding depression occurred in early portions of the life history, but multiplicative fitness functions provide evidence for inbreeding depression. We tested the prediction that selfing populations have lower levels of inbreeding depression than outcrossing populations but found no significant correlation.     

POLLEN MORPHOLOGY AND EVOLUTION IN HEDYOTIS SUBGENUS EDRISIA (RUBIACEAE)

Primarily on the basis of aperture structure, 31 species of Hedyotis subg. Edrisia (Houstonia) are separable into 5 palynological groups. Group 1 is characterized by a simple os circumscribed by varying nexinous thickenings, groups 2–4 combine this os with a crassimarginate one to form a compound os, while group 5 is known only with the crassimarginate os. The first type is considered primitive, the compound os specialized and more advanced, and the third type reduced and highly advanced. Other characteristics of the pollen, including size and shape, aperture number, thickness of sexine and nexine, and reticulum, are discussed in relation to the apertures, and their probable primitive and advanced expressions are outlined. The data agree with the phyletic trends found in the sporophyte on the basis of results from morphology, chromosome number and size, and distribution, and they support and add to an earlier phylogenetic scheme proposed for the subgenus. The evidence from palynology also supports the treatment of Hedyotis and Houstonia as congeneric.     

FLORAL STRUCTURE AND EVOLUTION IN LOPEZIEAE (ONAGRACEAE)

The Lopezieae present an interesting mixture of ancestral and derived characters: some members of the tribe retain the basic onagraceous chromosome number (n = 11), but the flowers are advanced in that they are mostly zygomorphic and always have a two-merous androecium. Species differ in the position of the nectaries, also in the way in which floral parts are united above the inferior ovary. These differences, when analyzed with information from a new monograph of the Lopezieae, provide the basis for a phylogenetic tree. It is inferred that ancestral Lopezieae were bird-pollinated woody perennials with regular flowers, two fertile stamens, and no floral tube distal to the ovary. Evolutionary events accompanying the emergence of modern taxa included abortion of the abaxial stamen (all surviving Lopezieae except Lopezia lopezioides), development of an epigynous floral tube (L. riesenbachia, L. semeiandra), decrease in floral symmetry without conversion to insect pollination (in two independent lines), and decrease in floral symmetry with conversion to insect pollination (in at least two independent lines). The prominent tubercles on upper petals of certain insect-pollinated species apparently evolved from the less prominent swollen areas still present in some of the bird-pollinated species. The tubercles and an associated snapping mechanism arose in response to increasing selection for fly pollination. Densely staining areas in some specimens may be osmophores; if so, scent plays a supplementary role in the orienting of insects to the upper petals. Interstaminal nectaries and the absence of a floral tube link the Lopezieae to Ludwigia; the relationship of these two taxa to Epilobium is presently unclear. Fossil records indicate that the Onagraceae had evolved by the beginning of the Tertiary Period and that the Ludwigia line is very old. The family's ancestral features are retained to a greater degree in Fuchsia, however, than in Ludwigia.     

鹅掌楸的花部数量变异与结实率

濒危植物鹅掌楸（Ｌｉｒｉｏｄｅｎｄｒｏｎｃｈｉｎｅｎｓｅ（Ｈｅｍｓｌ．）Ｓａｒｇ．）的花被片一般为９枚,对贵州松桃（Ｇ）、湖南龙山（Ｈ）和浙江龙王山（Ｚ）三地自然居群３年的观察发现,少数单株出现花被片数目变异,有１０、１１、１２枚花被片情况。与居群Ｇ和Ｈ相比较,居群Ｚ在单花花粉量,花粉大小和雌蕊数目等方面的变异较小,且无花被片数目变异。结实率与花部数目变异明显相关,变异较大的居群其结实率也高。居群间花粉平均大小与结实率有较好的正相关（ｒ＝０７６）,并在居群间比较了结实率与花粉胚珠比（Ｐ／Ｏ）的关系（ｒ＝－０７４）,发现Ｐ／Ｏ低的居群趋向于有较高的结实率,暗示资源配量限制了鹅掌楸的结实率。花部数量变异与结实率的关系表明潜在的遗传多样性对种子产量有明显影响。     

NORMAL FLORAL ONTOGENY AND COOL TEMPERATURE-INDUCED ABERRANT FLORAL DEVELOPMENT IN GLYCINE MAX (FABACEAE)

Floral onset in soybean (Glycine max cv. Ransom) is characterized by precocious initiation of axillary meristems in the axils of the most recently initiated leaf primordium. During floral transition, leaf morphology changes from trifoliolate leaf with stipules, to a three-lobed bract, to an unlobed bract. Soybean flowers initiated at 26/22 C day/night temperatures are normal, papilionaceous, and pentamerous. Sepal, petal, and stamen whorls are initiated unidirectionally from the abaxial to adaxial side of the floral apex. The median sepal is located abaxially and the median petal adaxially on the meristem. The organogeny of ‘Ransom’ flowers was found to be: sepals, petals, outer stamens plus carpel, inner stamens; or, sepals, petals, carpel, outer stamens, inner stamens. The outer stamen whorl and the carpel show possible overlap in time of initiation. Equalization of organ size occurs only within the stamen whorls. The sepals retain distinction in size, and the petals exhibit an inverse size to age relationship. The keel petals postgenitally fuse along part of their abaxial margins; their bases, however, remain free. Soybean flowers initiated at cool day/night temperatures of 18/14 C exhibited abnormalities and intermediate organs in all whorls. The gynoecium consisted of one to ten carpels (usually three or four), and carpel connation varied. Fusion of keel petals was often lacking, and stamen filaments fused erratically. Multiple carpellate flowers developed into multiple pods that were separate or variously connate. Intermediate type organs had characteristics only of organs in adjacent whorls. These aberrant flowers demonstrate that the floral meristem of soybean is not fixed or limited in its developmental capabilities and that it has the potential to produce alternate morphological patterns.     

FLORAL MORPHOLOGY AND CROSS-POLLINATION IN ERYTHRONIUM GRANDIFLORUM (LILIACEAE)

In bumblebee visits to flowers of Erythronium grandiflorum (Liliaceae), the ratio of self- to nonself- (“outcross”) pollen grains deposited on the stigma is positively correlated with the degree of stylar exsertion beyond the anthers. Natural populations show substantial, continuous variation in stylar exsertion.     

FLORAL FLAVONOIDS AND ULTRAVIOLET PATTERNS IN VIGUIERA (COMPOSITAE)

Variation occurs among species of Viguiera series Viguiera for ultraviolet (uv) absorption/reflection patterns of ligules. Floral flavonoids that cause uv absorption occur in epidermal papillae. Flavonoids are further localized to the proximal portion of the ligule in the seven taxa that have only proximal uv absorption. Floral flavonoids involved in uv absorption consist of flavone, flavonol, and anthochlor (chalcone/aurone) glycosides. Quercetin 3-methyl ether glycosides characterize the ligules of 10 taxa occurring in Baja California, Mexico, and nearby areas, and these taxa appear to form one taxonomic group. The anthochlor pair, marein/maritimein, characterizes V. dentata, and the lack of ligule flavonoids distinguishes V. potosina from the remaining taxa. The presence of the anthochlor pair, marein/maritimein, only in V. dentata and the lack of ligule flavonoids in V. potosina concur with other data to indicate that these species are not correctly placed with each other or with the other species currently included in series Viguiera.     

INFLORESCENCE AND FLORAL DEVELOPMENT IN HOUTTUYNIA CORDATA (SAURURACEAE)

The inflorescence of Houttuynia cordata produces 45–70 sessile bracteate flowers in acropetal succession. The inflorescence apical meristem has a mantle-core configuration and produces “common” or uncommitted primordia, each of which bifurcates to form a floral apex above, a bract primordium below. This pattern of organogenesis is similar to that in another saururaceous plant, Saururus cernuus. Exceptions to this unusual development, however, occur in H. cordata at the beginning of inflorescence activity when four to eight petaloid bract primordia are initiated before the initiation of floral apices in their axils. “Common” primordia also are lacking toward the cessation of inflorescence apical activity in H. cordata when primordia become bracts which may precede the initiation of an axillary floral apex. Many of these last-formed bracts are sterile. The inflorescence terminates with maturation of the meristem as an apical residuum. No terminal flowers or terminal gynoecia were found, although subterminal gynoecia or flowers in subterminal position may overtop the actual apex and obscure it. Individual flowers have a tricarpellate syncarpous gynoecium and three stamens adnate to the carpels; petals and sepals are lacking. The order of succession of organs is: two lateral stamens, median stamen, two lateral carpels, median carpel. The three carpel primordia almost immediately are elevated as part of a gynoecial ring by zonal growth of the receptacle below the attachment of the carpels. The same growth elevates the stamen bases so that they appear adnate to the carpels. The trimerous condition in Houttuynia is the result of paired or solitary initiations rather than trimerous whorls. Symmetry is bilateral and zygomorphic rather than radial. No evidence of spiral arrangement in the flower was found.     

FLORAL DEVELOPMENT AND VASCULATURE IN HYDROCLEIS NYMPHOIDES (BUTOMACEAE)

The flower of Hydrocleis nymphoides consists of three sepals which arise in spiral succession, three simultaneously arising petals, numerous stamens and staminodia which arise in centrifugal order, and six carpels. A residual apex remains at maturity. The first-formed members of the androecium are stamens and the later-formed members are staminodia which develop below the stamens and which become outwardly displaced during expansion of the receptacle. The androecium is supplied by branching vascular trunk bundles. The carpels are completely open but the ventral margins are slightly conduplicately appressed basally. A single dorsal bundle provides the stigmatic area with vascular tissue, and a network of small placental bundles supplies the numerous laminar ovules. There are no clearly defined ventral bundles. It is suggested that Hydrocleis nymphoides is neither the most primitive nor the most advanced member of the family. A pattern of phylogenetic reduction in the androecium and receptacle is suggested for the entire family.     

FLORAL STRUCTURE AND ORGANOGENESIS IN PODOPHYLLUM PELTATUM (BERBERIDACEAE)

The life cycle of Podophyllum can be divided into two phases, a subterranean phase during which a conspicuous winter mixed terminal bud forms at the end of a rhizome, and an aerial phase, during which the primordia of the structures within the winter bud give rise the next spring to an aerial shoot composed of a stem, 2 leaves, and a single flower. The transition from a vegetative to a floral apex occurs at the end of July, when the apical meristem becomes a globoid structure. During the first and second weeks of August, the floral organs are laid down along the sides of an elongated floral apex. The order of initiation of the floral organs is sepals, petals, stamens, gynoecium, and stamens. Petal primordia are initiated in early August, but growth ceases after they attain a height of about 2 mm. This inhibition persists until the middle of May in the next growing season, when the petals grow to 12 mm within 2 weeks. At anthesis the petals have enlarged to a length of 2 cm or more. The gynoecium is usually composed of a single terminal carpel. The ovules are chiefly supplied by branches from a ventral bundle complex, but that is supplemented by medullary bundles that are formed in the base of the gynoecium, below the loculus. It could be argued that these medullary bundles are surviving remnants of the vascular supply to a second carpel, no longer extant. A transmitting tract extends from the stigma about half the distance to the loculus. The tract is lined with unicellular glandular cells and is open from the stigma to the loculus.     

AGAMOSPERMY AND THE LOSS OF DISTYLY IN ERYTHROXYLUM UNDULATUM (ERYTHROXYLACEAE) FROM NORTHERN VENEZUELA

Erythroxylum undulatum is a gametophytic apomict that produces about 15% seed set independently of pollination. Embryo sac formation is aposporous, and the plants are largely pollen-sterile, which may be a result of polyploidy and hybrid origin. It appears to be derived from a distylous ancestor, as all other known species of Erythroxylum are distylous or secondarily dioecious, and all examined individuals of E. undulatum correspond to the normal long–styled morph. This is the first clearly documented case of agamospermy derived from distyly.     

ANTHESIS AND FLORAL SENESCENCE IN CHLOROGALUM POMERIDIANUM (LILIACEAE)

Flowers of the soap-plant, Chlorogalum pomeridianum (DC.) Kunth., open for a few hours on only one day. The flowers open rapidly in the late afternoon, produce nectar, and close some 6-8 hr later. As the time of anthesis nears, the tepals become contorted, and progressively larger cavities appear in the tepal mesophyll. Multicellular trichomes at the tips of the tepals increase in length, untangle, and allow the flowers to spring open. Senescence is accompanied by the breakdown of mesophyll cells and by increased ethylene production as the perianth segments twist together and become deliquescent. Anthesis has a weak but discernible rhythmic component and is strongly influenced by alternating light and dark periods. Experiments showed that the length of the uninterrupted light period is of primary importance in the control of anthesis.