FECUNDITY AND SIZE RELATIONSHIPS IN JACK-IN-THE-PULPIT,ARISAEMA TRIPHYLLUM (ARACEAE)

Arisaema triphyllum is a gender-labile woodland herb in which sex expression is correlated with the abundance of stored resources. Larger plants are female or monoecious, smaller ones are male. Among females larger plants produce more flowers, fruits and seeds, and the rate of successful fruit and seed formation is greater for plants of greater ht and corm diam. Average seed wt is greater in larger plants. Seed number per fruit and average seed wt per fruit taper towards the top of the infructescence. Pollinator limitation and resource supply may both contribute to the regulation of yield; their effects can be interpreted sequentially.     

CYCLIC HETEROPHYLLY IN SYNGONIUM (ARACEAE)

Species in the genus Syngonium germinate on the ground and mature on the trunks of the trees. These vines consist of relatively unbranched shoots which grow through the forest for considerable distances both horizontally and vertically. In the three species of this study, the shape of the segment, measured as internode diam/length, falls into two distinct classes, leafy and elongate, and varies cyclicly along single shoots. Two cycles are recognized. One cycle occurs in small diam terrestrial shoots in which cycling seems to be controlled by endogenous factors, and occurs with a period of a few tens of segments. The other cycle occurs in shoots of larger diam which climb and descend from trees. In this cycle, alternation between the two forms is controlled by gain or loss of contact with trees, and shoots may remain within a phase of the cycle for hundreds of segments, as long as the substrate does not change.     

CHROMOSOME NUMBERS IN THE GENUS ANTHURIUM (ARACEAE) II

Chromosome numbers were determined for 86 Anthurium species. Fifty-one of these were newly determined with counts ranging from 2n = 24 to 66 and 30 being the most common. All known Anthurium chromosome numbers were summarized, and 43 taxonomic changes were made in the previous reports to reflect current taxonomy. In terms of somatic chromosome numbers, the numbers form four polyploid series of 20–40–60, 24–30–48–84, 28–56 and 30–60–90–ca. 124. Paleoaneuploidy, polyploidy and B-chromosomes are basic features of the genus, but subsequent recent aneuploidy is not. The exact nature of chromosome evolution in Anthurium remains to be elucidated.     

DIVERSITY OF SHOOT MORPHOLOGY IN TYPHONIUM (ARACEAE)

The details of shoot organization, including number of leaves per shoot, position of foliage leaves and cataphylls, position of the lateral continuation shoot, nature of axillary buds and phyllotaxis, and the pattern of shoot extension were observed and compared in five species of Typhonium, Dracunculus vulgaris, Sauromatum venosum, Arum italicum, and Helicodiceros muscivorus, resulting in the recognition of four types of stems. Three of the four types were found in the genus Typhonium. One type was found in Typhonium giganteum and Sauromatum venosum and is presumably the same in Biarum. Another type, found in T. trilobatum, T. blumei, and T. flagelliforme, is distinct in the position of the lateral continuation shoot, which arises from the axil of the n-1 leaf and is adnate to the axis to above the n leaf. Based on the results, two groups, one of which is further subdivided into two subgroups, are recognized in subtribe Arinae (subfam. Aroideae tribe Areae).     

BEETLE POLLINATION OF DIEFFENBACHIA LONGISPATHA (ARACEAE)

Dieffenbachia is an monoecious understory herb of tropical rain forests that exhibits a complex and specialized relationship with its beetle pollinators. The erect protogynous inflorescence has the spadix divided, with the female flowers in the basal half and male flowers in the upper half. Dieffenbachia longispatha Engler & Krause is pollinated by scarab beetles in the genera Cyclocephala and Erioscelis. The enveloping spathe of the inflorescence opens in the evening, but no flowers are sexually functional until the stigmas become receptive about 24 hr later. Beetles fly to the inflorescence in darkness, suggesting that floral odors play a role as an attractant. Beetles remain in the inflorescence for 24 hr, eating protein-rich staminodia that surround the stigmas. On the evening of the third day the anthers dehisce and beetles become covered with pollen as they crawl up the spadix in the process of leaving. Beetles fly an average of 80 m between inflorescences, usually to the nearest female inflorescence, although distances of 400–1,000 m have been observed. Minimal estimate of genetic neighborhood sizes are large for D. longispatha (750 to 8,900 plants) and neighborhood areas encompass 41,000 to 67,000 m². Experiments demonstrate that the species is self-compatible and that fruit production is pollinator limited.     

RELATIVE POLLINATOR EFFECTIVENESS AND EVOLUTION OF FLORAL TRAITS IN SPATHIPHYLLUM FRIEDRICHSTHALII (ARACEAE)

We studied the relative effectiveness of different pollinators of Spathiphyllum friedrichsthalii Schott for 15 months on Barro Colorado Island, Panama. Pollen-foraging stingless bees (Apidae: Trigona) made 87% of floral visits. Experiments showed that these bees pollinate flowers, and correlations of fruit- and seed-set with visitation frequencies and floral contact times suggested that they were responsible for the majority of seeds produced. Fifteen species of fragrance-foraging, male euglossine bees (Apidae: Euglossini) collectively accounted for a small portion of seed-set in fewer than 27% of the inflorescences. Neocorynura (Halictidae) were pollen thieves and were unimportant as pollinators. We propose that euglossine and stingless bees differentially influence outcrossing rates and the evolution of floral traits of S. friedrichsthalii. Foraging behavior of male euglossines should allow for more long-distance pollen flow whereas stingless bees are likely to promote near-neighbor and geitonogamous pollinations. We discuss why the prolonged male phase of anthesis in this protogynous species may be maintained through pollination by stingless bees rather than male euglossines. Furthermore, although the floral fragrance is attractive to many species of male euglossines, it attracts few individuals. This condition may represent an intermediate step in the evolution of predominant pollination by male euglossines.     

ANDROMONOECY AND VARIATION IN PHENOTYPIC GENDER OF PASSIFLORA INCARNATA (PASSIFLORACEAE)

We studied the perennial vine Passiflora incarnata Linnaeus (Passifloraceae) in Alachua County, Florida, from May to August 1983 to determine the breeding system and investigate seasonal changes in phenotypic gender of individual plants. Passiflora incarnata is an obligate outcrosser, incapable of self-fertilization. The major pollinators were carpenter bees (Xylocopa sp.). The proportion of flowers setting fruit was not limited by pollinator service, but the weight of individual fruits and number of seeds/fruit was increased over naturally pollinated flowers by manually performing cross-pollination. Morphological differences in style position among flowers caused some flowers to function primarily as males and others to function as hermaphrodites. Although some of the flowers that functioned as males set fruit when manually cross-pollinated, the proportion of these male flowers capable of setting fruit was lower than the proportion of hermaphroditic flowers setting fruit when manually cross-pollinated. Further, some male flowers had atrophied ovary and styles and were completely incapable of setting fruit. Passiflora incarnata is thus functionally andromonoecious. The relative production of male versus hermaphroditic flowers varied among individuals and over the course of the flowering season. Unmanipulated plants in the population became increasingly male-biased in floral sex ratios as the reproductive season progressed. We attempted to modify phenotypic gender in experimental plants by limiting the ability of plants in some treatment groups to set fruit. Treatment groups significantly affected production of hermaphroditic flowers, but production of male flowers was not affected by treatment. Treatment did not significantly affect fruit weight, number of seeds per fruit or the percentage of hermaphroditic flowers that successfully matured fruit. These results suggest that andromonoecy in P. incarnata is a mechanism for adjusting allocation of reproductive effort to male and female function, and that maternal investment in this species is regulated primarily by varying production of hermaphroditic flowers.     

THE GENETICS OF GENDER AND THE EFFECTS OF GENDER ON FLORAL CHARACTERS IN GYNODIOECIOUS PHACELIA LINEARIS (HYDROPHYLLACEAE)

The evolution of gynodioecy depends in part on the location (nucleus or cytoplasm) of gender-determining genes. Characters genetically correlated with gender also can be important in the evolution of this sexual system. For example, gender differences in the costs of flowers affect the potential for resource compensation by females for the loss of male function. This paper reports the genetics of gender and the nature of secondary sex characters of flowers in Phacelia linearis (Hydrophyllaceae), a gynodioecious annual in which females exhibit substantial compensation. A single nuclear gene has a major effect on gender, recessive homozygotes being male-sterile, but not all the data can be explained by this or other simple inheritance models. In nature, hermaphrodites have wider corollas than females and begin to flower slightly later than females. In a common environment, gender effects on corolla size are modified by genetic background and/or maternal effects. Hermaphrodite flowers have 15% greater dry biomass than female flowers, but similar ovule number and nectar sugar production. Hermaphrodite and female flowers differ in the linear dimensions and biomass allocation of several floral organs. In particular, the androecia and corollas of female flowers are smaller than those of hermaphrodite flowers, both in absolute terms and relative to the size of the rest of the flower. Corolla size reduction could be an important source of resources for compensation by females.     

PHENOTYPIC GENDER IN SEX CHANGING DWARF GINSENG,PANAX TRIFOLIUM (ARALIACEAE)

Dwarf ginseng (Panax trifolium L., Araliaceae) is a diphasic (“sex changing”) species in which one phase has staminate flowers and the other has hermaphroditic flowers. In order to determine the relative allocations of the hermaphroditic gender phase to male and female functions,variation in population gender phase ratios, pollen production and viability, and ovule and seed production were documented. Gender phase ratios are highly male-biased. Dwarf ginseng is self-compatible, and both gender phases have viable pollen capable of effecting fertilization. Males produce more flowers and more viable pollen per anther than hermaphrodites. The phenotypic gender of hermaphrodites is extremely female-biased; it is likely that hermaphrodites function essentially as females. Sexual selection may have a role in the evolution and maintenance of differences between the gender phases in allocation to male function.     

天南星科岩芋属的细胞地理学研究

本文报道了岩芋属三个种的染色体数目和核型:岩芋Remusatia vivipara是三倍体,核型公式为K(2n)=3X=42=42m;早花岩芋R. hookeriana为二倍体,核型公式为K(2n)=2X=28=22m(6SAT) 6m(2SAT);秀丽岩芋R. ornala,也是三倍体,核型公式为K(2n)=3X=42=36m(3SAT) 3sm 3st。在岩芋属中,岩芋是一个比较原始的种,秀丽岩芋较进化。岩芋属是热带非洲和热带亚洲间断分布的小属,它的原始类群岩芋(R. vivipara)的原始居群(二倍体居群)分布在印度南部,因而作者没想,古南大陆是岩芋属的起源地,本属向热带亚洲的扩散是与第三纪时喜马拉雅造山运动相联系的。     

THE POLLINATION BIOLOGY OF TUCKAHOE,PELTANDRA VIRGINICA (ARACEAE)

This study describes the specialized brood-site-based pollination system of Peltandra virginica Kunth (Araceae) with the chloropid fly Elachiptera formosa Loew and provides experimental evidence that gender-related changes in floral odor composition synchronize pollinator behavior with the blooming sequence. P. virginica is protogynous and does not self-pollinate because of a strong temporal separation in sexual function, and it is dependent upon insects for pollination because the spathe completely surrounds the spadix during the pistillate stage. Field observations conducted in central New Jersey and southeastern Pennsylvania showed that E. formosa is closely associated with P. virginica inflorescences. Within the floral chamber, E. formosa adults feed on pollen, mate, and find oviposition sites while the larvae complete their development. Although drosophilid and syrphid flies were collected and reared from inflorescences of both sexual stages, only E. formosa emerged from pistillate-stage inflorescences and adult E. formosa rapidly transferred fluorescent dye particles between inflorescences of both sexual stages in laboratory enclosures. These findings indicate that this fly species is the primary pollinator at our study locations. Field censuses demonstrated that although E. formosa visited P. virginica inflorescences of both sexual stages with equal frequency, the female flies preferentially oviposited within pistillate-stage inflorescences. Analysis of floral volatiles with gas chromatography-mass spectrometry showed that only the spathes emit the floral fragrance and that the composition of the floral volatiles changed during the transition from pistillate to staminate stage. A particularly noticeable change occurred in the emission ratio of the two primary floral odor components, 4,5,7-trimethyl-6,8-dioxabicyclo[3.2.1.]octane and an unidentified chemical analog with molecular weight of 142. The relationship between floral volatile composition and fly oviposition behavior was evaluated using sham inflorescences placed in the P. virginica study population. The sham inflorescences were constructed by covering spadices dissected from mature inflorescence buds with spathes excised from different-age inflorescences. After a 2-hr-long exposure period, sham inflorescences fitted with pistillate-stage spathes contained more E. formosa eggs than the sham inflorescences with staminate-stage spathes. However, the highest number of ovipositions occurred in sham inflorescences fitted with spathes excised from mature inflorescence buds. The fragrance emitted by these spathes was composed almost entirely of the two principal odor components. The decline in ovipositions observed in both real and sham inflorescences corresponded to an increase in the emission ratio of 4,5,7-trimethyl-6,8-dioxabicyclo[3.2.1.]octane to the molecular weight 142 analog. This suggests that gravid flies searching for oviposition sites used the ratio of the two primary floral volatile components as an inflorescence gender or age recognition cue.     

MOLECULAR DELINEATION OF SPECIES AND SYNGENS IN VOLVOCACEAN GREEN ALGAE (CHLOROPHYTA)1

Two species of the colonial green flagellate family Volvocaceae are worldwide in distribution yet exhibit contrasting species structure. Geographically disparate isolates of Gonium pectorale Mueller can interbreed while isolates of Pandorina morum Bory behave quite differently. More than 20 sexually isolated subpopulations occur within this species; these have been termed “syngens” (sensu Sonneborn). Because prezygotic barriers to mating cause intersyngen pairings to fail, breeding analyses cannot be used to estimate genetic relatedness among the syngens of P. morum. DNA comparisons provide an alternative method of assessing genetic relatedness. We compared the nucleotide sequence of the internal transcribed spacer (ITS) region of the nuclear ribosomal repeat among clones of P. morum and of G. pectorale. Members of syngens of P. morum with distribution restricted to one small geographical area show great similarity. Likewise, members of any syngen of worldwide distribution show near uniformity, even those from different continents. However, the ITS sequence of each syngen differs from that of other syngens. In contrast, G. pectorale, which has an ITS region that is remarkably uniform throughout the world, appears to consist of a single syngen within North America and Europe by mating tests. The molecular data are in complete conformity with previous syngen assignment. Because the latter is based on mating affinity, with two complementary mating types per syngen, the evolution of new mating type pairs appears to be the basis of microevolution in these algae. We infer that either P. morum is a more ancient species than G. pectorale or that P. morum has a less stable genome. In either case, the biogeographic distribution of certain syngens may reflect climatological changes of the past.     

HEAT-PRODUCTION AND CROSS-POLLINATION OF THE ASIAN SKUNK CABBAGE SYMPLOCARPUS RENIFOLIUS (ARACEAE)

The Asian skunk cabbage Symplocarpus renifolius has an exothermic spadix on which about 100 flowers bloom in very early spring when effective pollinators such as bees and drone flies are inactive. This species is protogynous; female phase and male phase took 6.8 ± SD 5.8 days and 16.7 ± 5.7 days, respectively, with a short transitional phase of bisexuality (2.1 ± 0.9 days). The spadices produced heat 24 hours/day throughout female and bisexual phases, but temperature dropped quickly after the beginning of male phase. Although self-compatibility was expected from the flower structure, the basipetal flowering, and the absence of effective pollinators, bagging tests demonstrated that they rarely produce seeds without crossing. The spadices were visited by small numbers of invertebrates throughout the flowering season. Of these invertebrates, house flies, rove beetles, and mosquitos were the likeliest pollinators, since they are probably attracted both to the pollen produced in male phase and to the stench or carbon dioxide in female phase. On two female spadices with immature male flowers, we fortuitously collected a rove beetle and a mosquito that carried some pollen grains; these had to have been transported from other S. renifolius spadices. This infrequent and ineffective pollination appears to explain why as low as 13% of spadices set seeds in a natural population. We examine alternative hypotheses to explain production of heat in spadices of skunk cabbage.     

STRUCTURE AND FUNCTION OF THE GREEN STEM TISSUE IN OCOTILLO (FOUQUIERIA SPLENDENS)

Fouquieria splendens, a desert plant native to the southwestern United States, was studied to determine the capacity for photosynthesis of green stem tissue. The plant is leafless most of the year because of drought, so the capacity for gas exchange by the stems is essential for their photosynthetic function. With secondary growth, sclerified leaf bases which cover the stem become separated, and a transparent cork forms in the furrows between them. A well-developed chlorenchyma occurs beneath this cork as well as beneath the leaf bases. Chloroplasts of the stem have an unusually high degree of granal stacking, but are mostly typical. Light is transmitted through the leaf base on the young primary shoot and the furrow cork, but not through the older leaf base. Chlorophyll fluorescence studies indicated that the chloroplasts were fully competent and indeed stem tissue is capable of fixing ¹⁴CO₂ if supplied to cut sections. Despite competent chloroplasts, no exogenous CO₂ uptake occurs because the cork is impermeable to CO₂, and presumably water. The functional significance of competent chloroplasts in stems that do not transfer gas may be the production of high energy compounds for metabolism, the recycling of internally generated respiratory CO₂, or it may simply be a relictual feature in this species of the Fouquieriaceae.     

CELL DIVISION AND COLONY FORMATION IN THE GREEN ALGA COELASTRUM (CHLOROCOCCALES)1

Multinucleate cells of Coelastrum undergo precisely directed cytokinesis, guided by phycoplast microtubules, to form a number of uninucleate daughter cells which subsequently adhere to form characteristically patterned aggregates. As there is no movement of the daughter cells relative to one another before their adhesion, the disposition of cells in daughter colonies reflects the pattern of cytokinesis of parent cells. Centrioles lie at the poles of the mitotic nuclei which are partially enclosed by a perinuclear envelope of endoplasmic reticulum. The centrioles disappear at the time of cytokinesis of the parental cell and apparently reform de novo once the daughter cells have acquired a cell wall following their adhesion. The trilaminar layer of cell wall, often termed the pectic layer, does not stain with ruthenium red and resists acetolysis suggesting that it contains sporopollenin rather than pectin.     

DISJUNCT DISTRIBUTION OF THE XANTHOPHYLL LOROXANTHIN IN THE GREEN ALGAE (CHLOROPHYTA)1

Thirty-five green algal species, representing 17 orders in 5 classes, were examined for the presence of the xanthophyll loroxanthin by reversed-phase high-performance liquid chromatography. Of these, 16 possessed loroxanthin, including at least one member of each class of green algae. The distribution of loroxanthin as established by this and previous studies is disjunct within the Chlorophyta and does not appear to have any taxonomic significance. Most of the green algae examined possessed one or more xanthophyll pigments that have not been found in land plants.     

中国烟蚜不同地理种群的核型多态性研究(英文)

对中国不同地区 (湖南郴州、吉林长春、河南宜阳和江苏南京 )取食烟草的不同生活史的烟蚜Myzuspersicae (Sulzer)核型研究结果表明 :在红色型和褐色型中发现 4种染色体组型 ,即 2n =12 ,A1 与A3易位 ;3n =18,A1 与A3易位 ;3n =18,正常 ;2n =11。在黄绿色型中仅发现 2种染色体组型 ,即 2n =12 ,正常和 2n =12 ,A1 与A3易位。在 2n =12核型中 ,不同地区不同体色的烟蚜其染色体相对长度差异不显著 (α =0 .0 5)。