Transport and Compartmentation of Abscisic Acid in Roots of Hordeum distichon under Osmotic Stress

Using modified compartmental analysis the unidirectional fluxesof abscisic acid (ABA) and their cytoplasmic and vacuolar contentsin ³H-ABA preloaded barley root segments (Hordeum distichoncv. Aura) have been studied. When root segments were stressedosmotically with sorbitol (osmotic potential of the media ⁰= 0.2 MPa) cytoplasmic and vacuolar contents of ABA were enhanced.Under increased stress cytoplasmic and vacuolar contents weremuch lower than in the unstressed controls. ABA fluxes werevery sensitive to osmotic stress and ABA transport from thecytoplasm of the xylem parenchyma to the xylem vessels (_cx)was rapidly inhibited. The cultivar Aura has higher cytoplasmicand vacuolar ABA contents than the barley cultivar Kocherperle.This correlates well with the higher stress tolerance of theAura cultivar. Key words: Abscisic acid, Compartmentation, Osmotic stress     

Hormonal Control of the Teleost Ovary

The endocrine basis of gonadal development, reproductive processes,and many peculiarities related to reproduction in females ofthe highly diveisified teleosts can not yet be described satisfactorily.Although estrogens have been extracted from ovaries and peripheralblood of several species and various steroids were found tobe produced by ovarian tissue in vitro, there is an almost completelack of knowledge about their physiological role. It is beyond any doubt that hormones of the pituitary have amarked influence on ovarian maturation but many problems awaitfurther clarification. It is not yet clear whether gonadotropichormones might have a direct influence on certain traits ofbehavior in females. Biochemical work and a large number ofhistophysiological studies are at variance with regard to thequestion whether one or two gonadotropic hormones exist in teleosts.Technical difficulties (eg., shortage of hormonal material fromvarious sources, species specificity of gonadotropic hormone(s), widely scattered data from a large array of species withconsiderable differences in reproductive biology) hamper comparativeanalysis, Investigations on the hypothalamic control of endocrineevents are just in their beginning. The unique occurrence ofambisexual species in teleosts raises many questions which remainto be solved.     

An Overview of the Organization of the Brain of Actinopterygian Fishes

SYNOPSIS. The brain of actinopterygian fishes can be subdividedinto five principal parts, rhombencephalon, cerebellum, mesencephalon,diencephalon and telencephalon, each of which contains a numberof separate morphological entities: nuclei, areas or zones.Analysis of the origin and termination of the cranial nervesand their components reveals that many of the morphologicalentities distinguished in the actinopterygian brain can be interpretedin terms of elementary sensory and motor functions. Experimentalanatomical and physiological studies on the fiber connectionsof the entities thus defined have led to a functional interpretationof many other parts of the brain. Thus, the central circuitryrelated to such sensory functions as hydrodynamic pressoreception,electroreception, vision, gustation and olfaction are well-known,and the same holds true for the motor systems related to feedingand locomotion. However, there are still many regions in theactinopterygian brain the functional significance of which ispoorly understood, and it should be emphasized that most ofour knowledge on the organization of the brain of this grouprests merely on observations in teleosts. One of the most interestingaspects of actinopterygian neurobiology is that the telencephalonin this group develops in a way which differs fundamentallyfrom that found in all other craniates, and that the telencephalonshows a marked progressive differentiation in the series: polypterids—chondrosteans—halecomorphs—teleosts.     

Filament histology and anther dehiscence

Several distinctive histological features of the stamen, especially of the filament, are described, some of these for the first time: for example, commonness of (a) mesarch xylem maturation, amphicribral bundles or else collateral strands with phloem considerably enveloping the xylem, and clustering of sieve elements of a bundle and their spatial separation from tracheary elements, (b) exclusively helical wall thickenings of tracheary elements and absence of sclerenchyma, (c) open stomata, a weakly developed cuticle, a prominent intercellular-space system, xylem lacunae, and (d) tannins and crystals. Some of the features in category (a) seem related to the nutritional needs of developing pollen grains in the anther. Features in category (b) are directly related to the usual expansion of the stamen, in particular the filament, before and at anthesis. Features in category (c) (and possibly (d)) probably promote a rapid loss of water or a disruption of the water supply to the anther, and therefore might facilitate anther dehiscence (these features could operate either in isolation or in unison). Tannins, crystals, and secretory structures have been implicated in the protection of pollen against predators.     

The Effect of Phloem Ringing on Root Growth and Potassium Uptake by Helianthus annuus

The effect of phloem ringing on the uptake and transport ofpotassium by the roots of 4 week old sunflower plants has beeninvestigated. Ringing caused a rapid decline in both K⁺ uptakeand its transport (⁸⁶Rb tracer) to the shoot. The rate of rootelongation and the levels of sucrose in the root showed paralleldecreases after ringing. Measurement on isolated roots indicatedthat the effect of ringing the stem on K⁺ uptake by the rootswas confined to the apical 10 mm that included the extensionzone. It is postulated that the decline in potassium uptakeand transport, brought about by ringing, is due to the severanceof the sucrose supply which stops root growth. Key words: Roots, Growth, Salt uptake     

Regulation of Protein Synthesis in Embryos of Ilyanassa obsoleta

Much of the protein synthesis during early development in Ilyanassaresults from the translation of oogenetic mRNA. We show thatmicrotubule proteins are products of this translation, and thattheir synthesis is subject to translation level regulation.We also show that translation level regulation is involved inthe function of the polar lobe by making comparisons of theelectrophoretic patterns of synthesis of ¹⁴C labeled proteinsof normal embryos with the patterns of synthesis of ³H labeledproteins of embryos from which the polar lobes had been removedat the trefoil stage. Controls utilizing biochemical and morphologicalmarkers were performed to assure that normal and delobed embryoswere developing at equivalent rates. The expression of significantdifferences in the patterns of protein synthesis were foundbetween normal and delobed embryos, and these differences werenot dependent upon concomitant RNA synthesis. These differenceswere observable as early as after only 24 hours of development,although organogenesis does not begin until much later in development.Therefore, the observed differences probably reflect determinativeevents. The results support the hypothesis that the developmentaldeterminants of the polar lobe may include specific, preformedmRNA sequences, or specific regulators of translation.     

Mitochondrial and nuclear markers support the monophyly of Dolichopodidae and suggest a rapid origin of the subfamilies (Diptera: Empidoidea)

Abstract. The Dolichopodidae is a species‐rich dipteran group with almost 7000 described species. The monophyly of the subfamilies and their relationships remain largely unknown because the polarities of key morphological characters are unclear and molecular data are available only for 9 of the 19 proposed subfamilies. Here we test whether molecular data from two nuclear (18S, 28S) and four mitochondrial (12S, 16S, Cytb, COI) genes can resolve the higher‐level relationships within the family. Our study is based on 76 Oriental species from 12 dolichopodid subfamilies and uses eight species of Empididae and Hybotidae as outgroups. Parsimony and likelihood analyses confirm the monophyly of the Dolichopodidae, as well as the monophyly of five of the ten subfamilies represented by more than two species [Sympycninae, Sciapodinae, Dolichopodinae, Hydrophorinae (excluding tribe Aphrosylini), Neurigoninae]. There is strong support for restoring the tribe Aphrosylini as a separate subfamily Aphrosylinae. The monophyly of Medeterinae, Peloropeodinae and Diaphorinae is dependent on which tree reconstruction technique is used, how indels are coded, and whether the fast‐evolving sites are excluded. Overall, we find that our sample of Oriental species is largely compatible with the subfamily concepts that were developed for the northern temperate fauna. However, our data provide little support for relationships between the subfamilies. Branch lengths, saturation, and distance plots suggest that this is probably the result of the rapid origin of dolichopodid subfamilies over a relatively short time. We find that genera that are difficult to place into subfamilies based on morphological characters are generally also difficult to place using molecular data. We predict that a dense, balanced taxon sample and protein‐encoding nuclear genes will be needed to resolve the higher‐level relationships in the Dolichopodidae.     

No overlap in song repertoire size between yearling and older Starlings Sturnus vulgaris

We recorded the song of 25 male Starlings Sturnus vulgaris to investigate differences in song characteristics between yearling and older males. Older males had significantly larger repertoire sizes and sang significantly longer average song bouts than yearling males. Since older males had almost twice as large a repertoire size as yearling males and since there was no overlap in repertoire size between yearling and older males, our data indicate that the repertoire size of Starlings increases after the first year of life. The largest difference between yearling and older males occurred in the 'variable song types' which are the song types containing most of the heterospecific imitations sung in a song bout.     

Developmental Capacity of Aneuploid Xenopus Species Hybrids

Diploid as well as triploid Xenopus interspecific hybrids generate aneuploid eggs because of the presence, at meiosis, of univalent chromosomes which are presumably distributed at random. Zygotes obtained from such eggs, fertilized by either normal or UV-irradiated sperm, were analysed for their developmental capacities. All monosomics die in the course of embryogenesis, whereby optimum capacities correspond closely with those observed in monosomic mammalian embryos, especially in mice. In contrast, hyperdiploid Xenopus are relatively viable: although many die exhibiting the'haploid syndrome'or various other abnormalities, 8% of them reach metamorphosis, and 1–2% become adults. Of the latter, the karyotype was established in 13 individuals. Among them, 8–16 supernumerary chromosomes were found to be present.