MIXED MATING SYSTEMS IN HAWAIIAN BIDENS (ASTERACEAE)

Floral features related to the breeding system were studied for 11 species of Hawaiian Bidens. Protandry and male sterility promote outcrossing, while self-compatibility and geitonogamy contribute to inbreeding. The combination of these floral mechanisms results in a mixed mating system in all species studied. Outcrossing rates of 15 populations of these species ranged from 0.43 to 0.88, averaging 0.65. Apparent selling rates of females ranged from 0 to 0.25 in seven gynodioecious populations surveyed, suggesting that there is variation in the level of biparental inbreeding among populations. The presence of females increased the level of outcrossing by an average of 9% in gynodioecious populations. This study indicates that the efficiency of gynodioecy as an outcrossing mechanism largely depends on the current outcrossing rate of hermaphrodites, the frequency of females, and the extent of genetic substructuring in populations. On average, autogamy contributed 4%, geitonogamy contributed 24%, and consanguineous mating contributed 15% to the realized selfing rate (43%) in the hermaphrodites of these species.     

CHROMOSOME NUMBERS OF HAWAIIAN FLOWERING PLANTS AND THE SIGNIFICANCE OF CYTOLOGY IN SELECTED TAXA

Chromosome numbers are reported for 128 species of flowering plants indigenous or endemic to Hawaii, including first reports for 13 genera and 82 species. The special significance of reports for Ilex, Tribulus, Keysseria, Pisonia, Boerhavia, Jacquemontia, Claoxylon, Lipochaeta, Railliardia, and Dubautia are discussed. The cytological and morphological variation in Railliardia and Dubautia is considered and their treatment as congeners is advocated. The cytogeogruphic pattern in Dubautia and Railliardia and other factors suggest that the ancestral chromosome number of the Hawaiian tarweeds is n = 14. Their derivation from a western North American progenitor similar to Adenothamnus is considered plausible if not indeed likely.     

ADAPTIVE RADIATION AND GENETIC DIFFERENTIATION IN HAWAIIAN BIDENS

The genus Bidens (Asteraceae) has undergone extensive adaptive radiation on the Hawaiian Islands. The 19 species and eight subspecies endemic to Hawaii exhibit much more morphological and ecological differentiation than the continental members of the genus. However, the Hawaiian taxa have the same chromosome number and retain the capacity to interbreed in all possible combinations. Twenty-two populations of 15 Hawaiian taxa and four populations of American taxa were compared at 21 loci controlling eight enzyme systems. Populations of Hawaiian taxa are highly polymorphic. However, little genetic differentiation has occurred among taxa in spite of the high levels of genetic variability. Genetic identities calculated for pairs of populations show that populations of the same taxon are genetically more similar than are populations belonging to different taxa, but all values are high. The level of genetic differentiation that has occurred among the species of Hawaiian Bidens is comparable to the level of genetic differences found among populations within single continental plant species. Moreover, there is no correlation between the isozyme data and morphological data. No groups of taxa are evident in the genetic data, although morphological groups exist. Genetic differentiation at isozyme loci has not occurred at the same rate as the acquisition of presumably adaptive morphological and ecological characters in Hawaiian Bidens. Adaptive radiation may be limited to a few genes controlling morphological and ecological characters.     

MICROSPOROGENESIS AND TAPETAL DEVELOPMENT IN NORMAL AND MALE-STERILE CARROTS (DAUCUS CAROTA)

Zenkteler , Maciej . (U. Adam Mickiewicz, ul. Stalingradzka 14, Poznan, Poland.) Microsporogenesis and tapetal development in normal and male-sterile carrots (Daucus carota). Amer. Jour. Bot. 49(4): 341–348. Illus. 1962.—Meiosis and anther development proceed normally in fertile plants. Nine pairs of chromosomes are present at diakinesis and at metaphase I. The mature pollen grains possess 2 male gametes at the time of shedding; 80–92% of the pollen appears normal. A cross-shaped configuration at pachytene characteristic of a reciprocal translocation is present in the completely pollen-sterile plants indicating that one of the parents is homozygous for an interchange between 2 members of the chromosome complex. Chromosome bridges with fragments at anaphase I and anaphase II lead to aberrant chromosome distribution during meiosis. Complete microspore abortion is associated with a periplasmodium formation of the tapetum and anther wall deterioration.     

COMPARATIVE REPRODUCTIVE BIOLOGY OF HERMAPHRODITIC AND MALE-STERILE IRIS DOUGLASIANA HERB. (IRIDACEAE)

A comparative study of the reproductive biology of male-sterile and hermaphroditic plants in a gynodioecious population of Iris douglasiana Herb. (Iridaceae) was conducted at the University of California's Marine Laboratory at Bodega Bay, California, between 1976–1979. Each year of the study, there were 11.1% male-sterile plants in the population, some of which began blooming at the same time as the earliest blooming hermaphrodites. Male-sterile flowers made up between 7–21% of the flowers produced during the male-sterile flowering period. Male-sterile flowers had smaller sepals and petals than hermaphrodites, there were fewer of them per square meter, and they had fewer pollinated stigmas than did hermaphroditic flowers. In a test to determine pollinator preference, intact hermaphroditic flowers tended to have more pollinated stigmas than did hermaphrodites with their stamens removed or those flowers with shortened sepals made to resemble the smaller male-sterile flowers. Floral phenology and nectar-flow patterns were similar in both types of flowers as were the kinds of amino acids and sugar rewards in the nectar. Male-sterile flowers, however, produced much less nectar per flower. There were no significant differences in the number of ovules per flower or the number of seeds produced per capsule between the two flower types, but the loss of seeds through larval predation was much greater in capsules from hermaphroditic flowers. Early flowering and setting of seed by plants with male-sterile flowers could give them a reproductive advantage over plants with hermaphroditic flowers which experience higher levels of larval predation later in the growing season.     

COMPARATIVE ANATOMY OF SOME PARENTS AND HYBRIDS OF THE HAWAIIAN MADIINAE (ASTERACEAE)

Comparative leaf morphology and anatomy was examined in five species and four hybrids involving three genera of Hawaiian Madiinae (Asteraceae). The comparisons included Argyroxiphium grayanum, Dubautia ciliolata subsp. ciliolata, D. knudsenii subsp. knudsenii, D. scabra subsp. leiophylla, D. scabra subsp. scabra, and Wilkesia gymnoxiphium, and the hybrids A. grayanum × D. scabra subsp. leiophylla, D. ciliolata subsp. ciliolata × D. scabra subsp. scabra, D. knudsenii subsp. knudsenii × D. scabra subsp. leiophylla, and W. gymnoxiphium × D. scabra subsp. leiophylla. Foliar morphology, leaf tissue organization, and various characters of stomata and trichomes were compared, using epidermal peels, cross and paradermal sections, and clearings of leaves. Pronounced anatomical differences among these closely related taxa were characterized, and effects of hybridization on the expression of anatomical features were documented. Most comparisons of parents and hybrids revealed statistically significant differences in leaf size, distribution of adaxial and abaxial stomata, and marginal and surface trichomes. In most instances hybrids demonstrated intermediate status in their foliar characters, indicating that these features are inherited from both parents. However, differences in foliar characters were usually of sufficient magnitude to allow recognition of hybrids as well as parents.     

A COMPARATIVE LIGHT- AND ELECTRON-MICROSCOPIC STUDY OF MICROSPOROGENESIS IN MALE-FERTILE AND CYTOPLASMIC MALE-STERILE SUNFLOWER (HELIANTHUS ANNUUS)

Cytoplasmic male sterility (CMS) in sunflower anthers is compared with its normal (N) line by using light and electron microscopy. Degeneration and disintegration of CMS tapetum and microspore tetrads occur after meiosis II, resulting in sterility. At the onset of meiosis, the CMS tapetum enlarges radially and shows signs of disorganization of organelles and walls. The developing CMS meiocytes and tetrads of microspores do not show these abnormalities when compared with their N counterparts. The CMS microspore tetrads remain viable until a rudimentary exine forms around each microspore. At this time, the radially enlarged tapetum disintegrates, followed by disintegration of the tetrads. In N-line microsporogenesis, a peripheral, dense tapetum is present at the tetrad stage, and as each locule enlarges, free spaces occur around the tetrads. After a rudimentary exine with associated spines and colpi is formed around each microspore, the callose holding each tetrad together dissolves, freeing the microspores for further development. Eventually the binucleate tapetum becomes plasmodial, persisting until the vacuolate pollen stage.     

ATTRACTIVE STRUCTURES AND THE STABILITY OF HERMAPHRODITIC SEX EXPRESSION IN FLOWERING PLANTS

Plant attributes serving both male and female sex functions are thought to favor hermaphroditic breeding systems over systems where sex expression is separated between individuals. Morphological features used by plants to attract biotic pollinators can be considered in this light, because such “attractive” structures are prerequisite for both pollen donation and receipt. A model involving allocation of a limiting resource between attractive structures benefiting both sex functions, structures benefiting male function only, and structures benefiting female function only, is constructed and analyzed using the evolutionary stable strategy (ESS) approach. Contrary to expectation, conditions resulting in large allocation to attractive structures tend to destabilize hermaphroditism, although the effect is slight. Substantial asymmetry in the benefits accruing to male and female fertility for a given investment in pollinator attraction produces more pronounced effects, reducing the parameter space in which hermaphroditism is expected. Results of this model are used to assess the importance of “accelerating gain” curves previously suggested for the evolution of dioecy in flowering plants. Accelerating gains associated with fruit production and dispersal represent female function only, and can be sufficient to initiate evolution toward dioecy. Accelerating gains associated with pollinator attraction may contribute to the evolution of separate sexes only if male function benefits from increased investment in attractive structures at a disproportionate rate compared to female function. Even in this instance, though, hermaphroditism may be evolutionarily stable.     

INBREEDING DEPRESSION IN SCHIEDEA GLOBOSA AND S. SALICARIA (CARYOPHYLLACEAE), SUBDIOECIOUS AND GYNODIOECIOUS HAWAIIAN SPECIES

Progeny produced by inbreeding were compared to progeny derived from outcrosses for gynodioecious Schiedea salicaria and subdioecious S. globosa to assess fitness consequences of breeding system on parental fecundity (seeds per capsule) and progeny measures of fitness (germination, survival, biomass, and number of flowers). Results from both species indicated that inbreeding depression occurred at all measured stages of the life history. In both species, different females showed different levels of inbreeding depression. Multiplicative fitness functions of the ratio of values for selfed and outcrossed progeny in S. salicaria resulted in inbreeding depression values of 0.62–0.94. Within- vs. between-family crosses of S. globosa also resulted in inbreeding depression values as high as 0.49. These values suggest that inbreeding depression may promote the evolution of dioecy within S. globosa and S. salicaria, depending on the levels of natural outcrossing.     

甘肃木本植物新分类群

我们在对甘肃迭部县境内白龙江上游林区进行植物调查中,发现六个新变种,特报道之。     

安徽白马寨、清凉峰和六股尖的新地理分布植物

近年来我们从事了安徽省植物的调查、研究与植物标本的采集工作,1983年4—11月间,本文作者沈显生、张小平、刘登义三人曾分别到皖鄂边境的本省金寨县白马寨(海拔1729米)、皖浙边境的本省歙县清凉峰(海拔1787米)、皖赣边境的本省休宁县六股尖(海拔1630米),广泛收集资料和采集大量植物标本,并进行整理与鉴定。现将确认为是安徽省地理分布新记录的属共5个(Actaea L., Eutrema R. Br., Aegopodi-     

花叶开唇兰（兰科）大小孢子发生和雌雄配子体发育

花叶开唇兰的胚珠倒生,双珠被,薄珠心．雌配子体发育属蓼型,成熟胚囊７细胞．大小孢子发生过程中壁上都有胼胝质出现．小孢子四分体为四面体形,左右对称形,交叉形,Ｔ形,它们聚集成花粉小块．花粉散出时为２细胞型．药室壁４层,绒毡层底分泌型．     

刺五加大、小孢子发生和雌、雄配子体发育的观察

刺五加Eleutherococcus senticosus(Rupr．et Maxim．)Maxim．雄株的小孢子发生和雄配子体发育过 程正常,大孢子发生和雌配子体发育过程多不正常。雄花具5个花药,花药4室,药壁发育属双子叶型, 腺质绒毡层,绒毡层细胞多具2核。小孢子母细胞经减数分裂形成四面体形四分体,其胞质分裂为同时 型。成熟花粉为3细胞型。子房下位,5室;每室有上胚珠和下胚珠,上胚珠退化,下胚珠倒生、具单珠 被、厚珠心;大孢子母细胞经减数分裂形成线形或“T”形四分体,偶尔有2个并列或串联的四分体或在 四分体之上又出现孢原细胞。其功能大孢子位置不确定。雌配子体发育中异常现象较多。开花时,雌 配子体主要为反足细胞退化后的四细胞胚囊。刺五加雌株的小孢子母细胞不能进行减数分裂或减数分 裂不正常,不能形成四分体。开花时,药室空瘪,无花粉形成。其大孢子发生和雌配子体发育过程正常, 大孢子母细胞减数分裂形成线形或“T”形四分体,合点端大孢子为功能大孢子,胚囊发育属蓼型。开花 时,雌配子体主要为七细胞八核或七细胞七核胚囊,其卵器尚未发育成熟。刺五加两性株的小孢子发生 过程无异常,但雄配子体发育过程有部分异常;开花时,药室内有或多或少的空花粉,且花粉粒大小悬 殊,大的直径达35μm,小的仅15～18 μm。两性株的雌蕊发育大部分正常,也有一些异常胚囊形成。开 花时,雌配子体主要是七细胞八核胚囊、七细胞七核胚囊和反足细胞退化后的四细胞胚囊,其卵器也未发育成熟。     

DIFFERENTIAL GERMINATION OF RAY AND DISC ACHENES IN HEMIZONIA INCRESCENS (ASTERACEAE)

The differential germination responses of ray and disc achenes of Hemizonia increscens (Asteraceae) were compared in field and laboratory investigations in order to gain insight into the ecological and evolutionary significance of heterocarpy. In the field, 200 ray and 200 disc achenes were placed in native, sterilized soil in a series of cleared, randomized, replicated plots. In a nearby plot a similar number of achenes were placed in plastic petri dishes in which high moisture conditions were maintained. Disc achene germination occurred under relatively minimal moisture conditions (<1 cm rainfall for 19 days) and relatively mild temperature regimes (21–7 C). Disc achene germination began three days after planting in the field plot and four days after they were put into the field petri dishes. In contrast, the onset of ray achene germination occurred 21 days after planting in the field plot and 19 days after planting in the field petri dishes. Averages of 2.05 and 2.71 disc achenes/day germinated in the field plot and field petri dishes, respectively. These contrasted with averages of 0.57 and 0.50 ray achenes/day germinated in the field plot and in the field petri dishes, respectively. A total of 67.5% and 69% disc achenes germinated in the field plot and the field petri dishes, but only 18% and 16.5% ray achenes germinated in the field plot and field petri dishes, respectively. Three separate treatments, using 100 ray and 100 disc achenes in each, were performed in laboratory growth chambers: 1) nicking the fruit coat, 2) excising the embryo, and 3) leaving the fruit coat intact. Onset of germination for all disc achene treatments occurred after three days. No significant differences were found among the three disc achene treatments in timing, rate, or germination percentage. All three disc treatments in the laboratory closely paralleled those for disc achenes in the field plots in time and germination percentage, but rates of germination were not as high. Germination of the nicked and excised ray achenes treatments began after four days, while germination of the untreated ray achenes began after 27 days. Untreated ray achenes in the laboratory paralleled the ray achenes in both field experiments in rate and germination percentage, but were delayed in time of germination. The nicked and excised ray achene treatments, however, were similar to the disc achene treatments in time of germination, and were not significantly different from disc achenes in rate of germination. These data suggest 1) that ray and disc achenes are markedly different in germination under identical conditions in field and laboratory experiments, and 2) this difference in germination response may be due to the thicker pericarp of the ray achenes.     

EVOLUTIONARILY STABLE SELFING RATES OF HERMAPHRODITIC PLANTS IN COMPETING AND DELAYED SELFING MODES WITH ALLOCATION TO ATTRACTIVE STRUCTURES

I present a resource-allocation model to analyze how patterns of allocation to reproductive structures influence the evolution of selfing rates in hermaphrodites subject to competing and delayed forms of self-fertilization. The evolutionarily stable state does not depend on the mode of pollination. In contrast to previous models in which the number and the size of flowers were not considered, intermediate selfing is not evolutionarily stable with linear constraints on flower number and size. In contrast, intermediate selfing can be evolutionarily stable with nonlinear constraints on flower number and size. Optimal allocations to attractive structures increase and selfing rates decrease in the presence of inbreeding depression. In particular, stable intermediate levels of selfing may be favored when flower number is strongly constrained. Thus, nonlinear constraints on flower number and size could favor the evolution of intermediate selfing in either the delayed or the competing modes of selfing. Outcrossing is not favored in the absence of inbreeding depression, a result inconsistent with Holsinger's results in which allocation to attractive structures was not considered.     

ABERRANT MICROSPOROGENESIS AND STERILITY IN IMPATIENS SULTANI (BALSAMINACEAE)

Three mutants of Impatiens sultani (named as ‘Orange', ‘Crimson', and ‘Pink') show an unusually wide spectrum of aberrations in microsporogenesis. These aberrations range from premeiotic cytomixis to meiotic and postmeiotic irregularities such as precocious disjunction, tripolar separation of chromosomes, chromosome bridges, various patterns of atypical cytokinesis, supernumerary divisions of the meiotic products, and irregular divisions in the microspore. As a result of these abnormalities Orange is partially and Crimson and Pink are completely pollen sterile. The stigmas of Pink, besides, do not support pollen germination. The failure of pollen germination is attributed to the defective stigmatic fluid of Pink, which, compared to that of Orange and Crimson lacks organic compounds absorbing UV light at 261 nm. This constitutive deficiency in stigmatic fluid appears to be a little investigated facet of female sterility.