GENETIC EVIDENCE FOR MULTIPLE ORIGINS OF DIOECY IN THE HAWAIIAN SHRUB WIKSTROEMIA (THYMELAEACEAE)

Dioecy is unusually common in the Hawaiian Islands, yet little is known about the evolutionary biology of this breeding system. A native shrub, Wikstroemia, has an unusually diverse array of breeding systems: two forms of dioecy, cryptic and morphological dioecy, as well as hermaphroditism (perfect flowers). The existence of two forms of dioecy is significant for three reasons: 1) the presence of cryptic unisexuals that are functionally unisexual, but retain the appearance of hermaphroditism in both sexes, is strong evidence for the ancestral status of hermaphroditism; 2) the production of nonfunctional pollen, by female cryptic unisexuals, is a new instance of a phenomenon which has previously been reported for a few other species; 3) the two forms of dioecy are morphological markers which are useful in hybridization studies for tracing the genetic basis of their inheritance. Crosses were made between cryptically unisexual individuals (C), between morphologically unisexual individuals (M), and between the two types of unisexuality. The offspring of crosses between individuals with the same sex type usually resulted in offspring with that sex type, but most of the progeny of between-sex type crosses were, unexpectedly, perfect-flowered hermaphrodites. These results show that genetic control of sex determination is not homologous in all populations, suggesting that dioecy has evolved at least twice in Hawaiian Wikstroemia. The genetic data further suggest that males are the heterozygous sex.     

EVIDENCE FOR REGULATION OF PROTEIN SYNTHESIS AT THE TRANSLATION LEVEL IN RESPONSE TO DIETARY ALTERATIONS

Rats were maintained for several days on a protein-free diet which, approximately 14 hr before decapitation, was changed to a protein-rich diet. Microsomal subfractions of liver were obtained by sucrose density gradient centrifugation. The sedimentation patterns of the microsomal subfractions and of the polysomes were found to be unchanged after the alteration of the diet whereas the ability to incorporate amino acid was markedly enhanced. No significant differences in the RNA/protein ratio of the microsomal subfractions were observed. The changes in amino acid incorporation which were unrelated to concurrent changes in the amount of polysomes are discussed.     

TRANSFER OF PROTEINS FROM THE CHLOROPLAST TO VACUOLES IN CHLAMYDOMONAS REINHARDTII (CHLOROPHYTA): A PATHWAY FOR DEGRADATION

Several chloroplast proteins were detected by immunoelectron microscopy within dense granules in cytoplasmic vacuoles in the alga Chlamydomonas reinhardtii Dangeard. Transfer from chloroplast to vacuoles of two major, pulse-labeled polypeptides, the large subunit of rubisco and the α subunit of ATPase, which are synthesized on chloroplast ribosomes, was demonstrated by the recovery of these polypeptides in vacuolar granules over a several-hour time period. The ultrastructure of cryofixed algal cells was examined to search for structures that would provide insight into the transfer of chloroplast proteins to vacuoles. Micrographs showed that the two membranes of the envelope were appressed, with no detectable intermembrane space, over most of the chloroplast surface. Protrusions of the outer membrane of the envelope were occasionally found that enclosed stroma, with particles similar in size to chloroplast ribosomes, but generally not thylakoid membranes. These observations suggest that chloroplast material, especially the stromal phase, was extruded from the chloroplast in membrane-bound structures, which then interacted with Golgi-derived vesicles for degradation of the contents by typical lysosomal activities. A protein normally targeted to vacuoles through the endomembrane system for incorporation into the cell wall was detected in Golgi structures and vacuolar granules but not the chloroplast.     

家兔伏核—杏仁核神经通路在吗啡镇痛中的作用

用辐射热照射家兔鼻嘴侧部皮肤,测量其躲避反应潜伏期作为痛反应阈,简称痛阈。通过预先埋植的慢性套管向伏核或杏仁核内进行注射,结果表明:(1)在家兔的伏核内微量注射吗啡可产生镇痛作用,该作用可被杏仁核内注射纳洛酮所削弱,并有量效依从关系;在杏仁核内注射甲啡肽抗血清(ME AS)或β-內啡肽抗血清(β-EP AS)亦可削弱上述镇痛作用;(2)在杏仁核内微量注射吗啡可产生镇痛作用,此作用不能被伏核内注射纳洛酮所阻断;(3)在伏核内注射吗啡所产生的镇痛作用可被同一部位注射γ-氨基丁酸(GAEA)受体阻断剂氯甲基荷包牡丹碱所增强,被 GABA 受体激动剂异鹅羔胺所削弱。上述结果提示:在家兔脑内从伏核到杏仁核可能存在一条与镇痛有关的神经通路,伏核内的阿片样物质及杏仁核内的甲啡肽,β-内啡肽可能参与镇痛信息的传递,而伏核内的 GABA 可能有对抗吗啡镇痛的作用。     

HETERODICHOGAMY IN GRAYIA BRANDEGEI (CHENOPODIACEAE): REPORT FROM A NEW FAMILY

The reproductive biology of Grayia brandegei was examined. Although monoecious, Grayia brandegei exhibits a phenotypic dimorphism of protogynous and protandrous mating types known as heterodichogamy. For individual plants, the temporal separation of staminate and pistillate flowering phases appears to be complete. No self-fertilization is possible in protandrous plants, but may be possible in protogynous plants provided pistillate flowers remain unfertilized. Flowering phases of protogynous and protandrous mating types are synchronized and reciprocal, ensuring cross-fertilization between mating types. Less than 15% overlap of sexual functions occurred between plants of the same mating type. Protogynous and protandrous plants were randomly dispersed in the environment and in relation to each other. Mating type frequencies did not differ significantly from 1:1. We discuss the possibility of a heterodichogamous pathway to dioecy.     

SECONDARY SEX CHARACTERISTICS IN SPINACIA OLERACEA L.: QUANTITATIVE EVIDENCE FOR THE EXISTENCE OF AT LEAST THREE SEXUAL MORPHS

Spinacia oleracea L. was grown hydroponically across an experimental salinity gradient with treatments of 0.0, 1.5, 3.0, 4.5, and 6.0 grams of NaCl/liter of nutrient medium. Plant height, root biomass, vegetative biomass, fruit morphology, average fruit weight, and fruit mass: volume ratio were examined in each treatment to determine if differences other than primary sex characteristics exist between male, female, and monoecious plants. Average fruit weight was the only parameter examined that was not useful as a secondary sex characteristic. Orthogonal contrasts examining plant height, vegetative biomass, and root biomass of plants were distinct from one another across the salinity gradient. Similarly, female and monoecious plants differed significantly from one another in terms of root biomass and the average mass: volume ratio of the fruit each sexual morph produced, as well as the proportion of smooth to wrinkled fruit produced. The data indicate that male, female, and monoecious plants are three distinct sexual morphs.     

PHOTOPERIOD EVIDENCE IN THE INTRODUCTION OF XANTHIUM STRUMARIUM TO TAHITI AND HAWAII FROM MEXICO

Successful invasion of islands in the Pacific by Xanthium probably resulted from the chance introduction of a morpho-physiological form adapted to subtropical coastal habitats in North America. This hypothesis was tested by comparing naturalized plants from Tahiti in the Society Islands and Oahu in the Hawaiian Islands with collections from various coastal sites in Mexico. Plants from Tampico and Ciudad Mante, Tamaulipas; Veracruz (Antigua), Veracruz; and Salina Cruz, Oaxaca have morphological and physiological similarity to the Pacific introductions; however, each collection has certain niche relations that are slightly different from each other. All of the collections are in the same morphological complex and have apparent critical nights of 10.75–11 hr for reproduction. This morpho-physiological form is probably indigenous to Mexico, and it is widely distributed on the northeastern coastal plain of Tamaulipas.     

FLUCTUATIONS IN FREE AMINO ACID POOLS OF GYMNODINIUM SIMPLEX (DINOPHYCEAE) IN RESPONSE TO AMMONIA PERTURBATION: EVIDENCE FOR GLUTAMINE SYNTHETASE PATHWAY1,2

An ammonia limited chemostat culture of Gymnodinium simplex (Lohm.) Kofoid & Swezy was perturbed with ammonia and fluctuations in the free intracellular amino acid pools were followed 80 min. The steady-state value of glutamate was 2.07 ± 10^-15 mol cell^-1 and of glutamine was 0.31 ± 10^-15 mol cell^-1. Five minutes after the perturbation, a substantial rise in glutamine was observed with a corresponding decrease in glutamate. This is considered a result of glutamine synthetase acting as the primary ammonia assimilating enzyme. The level of ammonia and the major free amino acids reached a maximum 10 min after the perturbation and then slowly decreased.     

江苏金坛盐矿形成时期盐湖水体成分:来自石盐包裹体的证据

我国白垩纪晚期-古近纪由于燕山运动和喜马拉雅运动,形成了一系列的断陷盆地,金坛盐矿就是该时期始新世中晚期的盐湖沉积.本次研究首次在国内半定量的进行了石盐原生包裹体的分析,发现其中Ca2+缺失而富含SO2-4,原始卤水成分为Na-Mg-K-Ca-C1-SO4体系.     

EVIDENCE FOR SEXUAL REPRODUCTION IN THE PRIMITIVE GREEN ALGA NEPHROSELMIS OLIVACEA (PRASINOPHYCEAE)1

Evidence for a specialized sexual process in Nephroselmis olivacea Stein is presented. This alga is a member of the Prasinophyceae, which is regarded by some as the most primitive Class of green plants. N. olivacea has a heterothallic type of mating system. Plus and minus gametes were morphologically similar but showed different behaviors during the mating process. The minus gamete settled to the substratum, attaching by its ventral side. The plus gamete attached to the dorsal side of the minus gamete by the region near the flagellar bases of the plus gamete. The mature zygotes were spherical and strongly adhered to the substratum. After zygote germination, two biflagellate daughter cells, each with two pyrenoids were liberated. These cells divided, resulting in four vegetative cells, each with a single pyrenoid.     

下丘脑弓状核区参与由中脑导水管周围灰质到伏核的上行镇痛通路

在家兔中脑导水管周围灰质(PAG)内微量注射吗啡产生的镇痛作用可被伏核内注射β-内啡肽抗体所对抗,在损毁下丘脑弓状核区(ARH)后该对抗效应消失。但损毁ARH并不影响PAG注射吗啡所引起的镇痛作用,也不影响伏核注射纳洛酮对于PAG内注射吗啡引起镇痛的对抗作用,以上结果提示,(1)从PAG到伏核的上行镇痛通路中有ARH及β-内啡肽能纤维参与;(2)除β-内啡肽以外,伏核内尚有其它阿片肽发挥镇痛作用。     

THE RELATION OF EXERCISE TO BUBBLE FORMATION IN ANIMALS DECOMPRESSED TO SEA LEVEL FROM HIGH BAROMETRIC PRESSURES

1. Bullfrogs (Rana catesbiana) and rats have been subjected to high barometric pressures and studied for bubble formation on subsequent decompression to sea level. Pressures varying from 3 to 60 pounds per square inch, in excess of atmospheric pressure, were used. 2. Muscular activity after decompression is necessary for bubble formation in bullfrogs after pressure treatment throughout the above range. Anesthetized frogs remained bubble-free following decompression. Rats compressed at 15 to 45 pounds per square inch likewise did not contain bubbles unless exercised on return to sea level. 3. Bubbles form without voluntary muscular activity in anesthetized rats previously subjected to pressure of 60 pounds per square inch. Small movements involved in breathing and other vital activities are believed sufficient to initiate bubbles in the presence of very high supersaturations of N₂. 4. Bubbles appear (with exercise) in rats previously compressed at 15 pounds per square inch, and in bullfrogs subjected to pressure at levels as low as 3 pounds per square inch above atmospheric pressure. The percentage drop in pressure necessary for bubble formation is less in compressed animals than in those decompressed from sea level to simulated altitudes. 5. The action of exercise on bubble formation in compressed frogs and rats is attributed to mechanical factors associated with muscular activity, combined with the high supersaturation of N₂. CO₂ probably is not greatly involved, since its concentration does not reach supersatuation, as it does at high altitude. 6. Anoxia following decompression from high barometric pressures has no observable facilitating effect on bubble formation.     

SEXUAL REPRODUCTION IN EPHEDRA NEVADENSIS (EPHEDRACEAE): FURTHER EVIDENCE OF DOUBLE FERTILIZATION IN A NONFLOWERING SEED PLANT

Since the initial discovery of double fertilization in angiosperms in 1898, a number of reports of double fertilization-like events in the genus Ephedra have appeared. Until recently, convincing documentation of double fertilization in Ephedra had not been presented. In Ephedra nevadensis, following entry of a single binucleate sperm cell into the egg cell, one sperm nucleus migrates in a chalazal direction to fuse with the egg nucleus. Contemporaneous with this first fertilization event, the ventral canal nucleus regularly migrates from its initially apical position within the egg cell to a more central position within the egg cytoplasm, where it fuses with a second sperm nucleus. Based on quantitative microspectrofluorometric analysis, occasional supernumerary nuclei within the egg cell (derived by migration through pores in the cell walls between jacket cells and the central cell or egg cell) can be ruled out as participating in the second fertilization event. The evolutionary establishment of double fertilization in Ephedra (or its ancestors) was dependent on a number of specific developmental preconditions: 1) persistence of the ventral canal nucleus (which is degenerate in many groups of nonflowering seed plants) through the time of normal fertilization; 2) regular displacement of the ventral canal nucleus from its initially apical position within the egg cell to a position within the egg cytoplasm where fusion of the egg nucleus with the first sperm nucleus earlier occurred; 3) acquisition of egg-like features by the ventral canal nucleus that allow it to attract and fuse with a sperm nucleus; and 4) consistent entry of a second sperm nucleus into the archegonial cavity to participate in a second fertilization event. Although it cannot be determined definitively whether double fertilization in Ephedra is evolutionarily homologous with double fertilization in flowering plants, comparative evidence is consistent with the hypothesis that double fertilization arose in a common ancestor of the Gnetales and angiosperms.     

EXPERIMENTAL STUDIES OF COMMUNITY EVOLUTION I: THE RESPONSE TO SELECTION AT THE COMMUNITY LEVEL

Coevolution generally refers to the process of two or more organisms adapting to each other as a result of individual selection. Another possibility, however, is that coevolution may result from selection acting directly at the community level. Certain types of multispecies associations, such as lichens, which are a symbiotic association between an alga and a fungus, are examples of simple two species communities that may be units of selection. The study presented here uses two species communities of Tribolium castaneum and T. confusum in an investigation of selection acting at the community level. Selection at the community level is performed on one trait measured in one species and correlated responses in other traits measured both within species and among species are monitored. I demonstrate that community selection, defined as the differential survival and or reproduction of communities, can result in significant changes in the phenotype of a community. The observed changes in the phenotype of a community as a result of community selection included changes in the trait under selection (direct effects of selection), as well as changes in traits that are not under selection (correlated responses to selection). Furthermore, two types of correlated responses to selection were observed. The first, within-species correlated responses to selection, are changes in a trait measured in one species as a result of community selection acting on another trait measured in the same species. The second, between-species correlated responses to selection, are changes in a trait measured in one species as a result of community selection acting on a trait measured in another species. Between species correlated responses to selection are of particular interest because they cannot be mediated by pathways of gene action that are internal to an individual, rather they can be mediated only through ecological pathways. In other words, between-species correlated responses to selection suggest that genetically based interactions among individuals are contributing to the response to community selection. These among species ecological pathways of gene action cannot contribute to a response to selection at a lower level; thus community selection may be able to bring about a response to selection that is qualitatively different from the response selection that would occur as a result of selection acting at a lower level.     

EVOLUTION OF DIOECY IN BUCHLOE DACTYLOIDES (GRAMINEAE): TESTS FOR SEX-SPECIFIC VEGETATIVE CHARACTERS,ECOLOGICAL DIFFERENCES,AND SEXUAL NICHE-PARTITIONING

Buchloe dactyloides is a perennial dioecious grass in which male and female inflorescences are so strikingly dimorphic that they were originally assigned to different genera. The objective of this paper is to present the results of tests for sex-specific vegetative characters, ecological differences, and sexual niche-partitioning, combining them with prior information on the reproductive biology of Buchloe for an evaluation of the key factors leading to the evolution of dioecy and sexual dimorphism. Field and greenhouse data were collected from Oklahoma and Kansas populations on vegetative characters, allocation to reproduction, and relative growth and competitive success along resource gradients. Except for greater susceptibility to leaf rust by males, there were no significant differences between males and females in vegetative characters, total biomass, or reproductive effort. Field studies of spatial distributions of males and females failed to show any relation to soil, topography, or soil moisture. In a 45-month greenhouse experiment starting at the seedling stage, the relative growth and competitive success of randomly paired individuals showed no evidence for differential competitive success or for niche-partitioning of males and females. The “outcrossing advantage” and subsequent sexual specialization of the female inflorescence appear to be the major factors underlying this dimorphic system.     

INFRASPECIFIC VARIATION OF SESQUITERPENE LACTONES IN AMBROSIA PSILOSTACHYA (COMPOSITAE)

The distribution of fifteen sesquiterpene lactones in sixty-two populations of Ambrosia psilostachya ranging from Canada to Mexico, and cytological observations for seven populations are reported. Chemical data for four Mexican populations of A. cumanensis Kunth are presented. The origin of chemically unique populations of A. psilostachya which occur on the islands and peninsulas that line the Texas Gulf coast are discussed with respect to the chemical, morphological and cytological data.