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.     

A phylogenetic analysis of the fungus-growing ants (Hymenoptera: Formicidae: Attini) based on morphological characters of the larvae

A phylogenetic hypothesis of the fungus-growing ants (subfamily Myrmicinae, tribe Attini) is proposed, based on a cladistic analysis utilizing forty-four morphological characters (109 states) of the prepupal worker larva. The fifty-one attine species analysed include representatives of eleven of the twelve currently recognized attine genera, excluding only the monotypic workerless parasite Pseudoatta ; the non-attines include two outgroups (species of the basal myrmicine genera Myrmica and Pogonomyrmex ), two myrmicine species presumed to be distantly related to the attines, and twelve species representing taxa that have been proposed by prior workers as possible sister groups of the Attini. There is strong character support for the monophyly of the Attini and for a sister-group relationship of the Attini and the Neotropical Blepharidatta brasiliensis. The Attini are divided into two distinct lineages, an 'apterostigmoid' clade (containing Apterostigma and Mycocepurus) and an 'attoid' clade (containing all other attine genera except Myrmicocrypta). The attine genus Myrmicocrypta appears to be paraphyletic with respect to these two groups; the species M.buenzlii in particular retains many attine plesiomorphies.
These results indicate that the fungus-growing behaviour had a single evolutionary origin in the ants. They also indicate that mycelium cultivation is plesiomorphic and that yeast cultivation is derived within the Attini, overturning the long-standing assumption that the yeast-growing Cyphomyrmex species are the most primitive Attini. Behavioural and ecological investigations into the origin and evolution of the fungus-growing behaviour might more profitably focus on species in the attine genus Myrmicocrypta , as well as those in the closely related non-attine genera Blepharidatta and Wasmannia.     

Ionic Balance of Root-Shoot Nitrate Transfer in Dwarf Bean

The Dijkshoorn-Ben Zioni model about potassium recycling in higher plants proposes a stoichiometric coupling between the upward transport of nitrate and potassium, and therefore a 1:1 ratio of these ions in the xylem sap. Phaseolus vulgaris grown in media with different NO₃: K⁺ ratios, however, only rarely showed equimolar concentrations of the two ions in the bleeding sap. Ratios between 0.2 and 11 were observed and the ratios between concentrations of the ions in the exudate and in the external solution were positively correlated. An analysis of the major inorganic constituents of the exudate revealed an ionic balance that requires negligible amounts of charges from organic molecules.     

Nitrate Uptake and Reduction of Aseptically Cultivated Spruce Seedlings, Picea abies (L.) Karst

Spruce (Picea abies (L.) Karst.) seedlings were asepticallycultivated and the effects of different N-nutrition on net uptakeand reduction of nitrate were investigated. The characteristicsof nitrate uptake were calculated, K_s as 0?2 mol m^–3 andV_max as 18 µmol g^–1 d^–1. Low pH, and Al³⁺ in the medium caused adecrease in nitrate uptake rate. An in vivo assay was set upwhich allowed the measurement of NRA in both roots and needlesof spruce seedlings. The in vivo nitrate reductase activitywas repressed by ammonium and stimulated by nitrate. Nitratereduction was similar to nitrate uptake, negatively affectedby low pH and ammonium. Therefore, a limited N-supply to spruceseemed to occur when pH was low in the rhizosphere combinedwith the presence of Al³⁺ and . Key words: Spruce, nitrate uptake, nitrate reduction     

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.