Characteristics of Zinc Uptake by Barley Roots

The linear uptake of zinc by excised barley roots (Hordeum distichon L.) in the time range from 20–120 min is not continued over periods of 20–28 h. In concentration dependent uptake experiments with intact barley roots three phases in the range up to 1.38 mM zinc could be detected independent of the tested uptake period. The kinetic constants increased with higher phases and the transition points were lowered with increasing time. The presence of copper did not inhibit the uptake of zinc competitively. On the contrary a slight stimulation in the uptake rates was observed indicating an interaction with the transition site. It is concluded that zinc and copper are taken up by separate mechanisms.     

Indirect Immunofluorescence Microscopy of Microtubular Structures in Male Germ Cells of Wildtype and l(3)pl (lethal-polyploid) Drosophila hydei

Tubulin-containing structures of the male germ cells of Drosophila hydei crossreact in indirect immu-nofluorescence microscopy with antibody directed against homogeneous porcine brain tubulin. There is no detectable difference in reactivity between germ cells of wildtype flies and the mutant l(3)pl (lethal-polyploid) which is characterized by microtubular abnormalities. However, the technique of indirect immunofluorescence microscopy allows the direct visualization of several abnormalities in the arrangement of the microtubular system of the mutant, particularly in the axonemal complex.     

Seed quality effects in bulb onions (Allium cepa L.)

The nature and persistence of seed quality effects produced by a range of seed production treatments was investigated in the autumn-sown onion crop. Genotypically equivalent seed lots raised in different glasshouses within the same year were found to germinate at significantly different rates. The seed lot which emerged earlier produced larger seedlings and this difference in size persisted throughout the growing period. In a comparison between the effects of hand crossing and self-pollination techniques the hand crossing method produced a much lower total seed yield but heavier seeds and larger plants. The induced effects persisted throughout the year but were not significant in the mature bulb characters. The implications of these results upon the control of seed production for plant breeding and genetical experiments is discussed.     

Egg-laying in response to prostaglandin injections in the Australian field cricket, Teleogryllus commodus

ABSTRACT. We report the effects of prostaglandin (PG) injection on egg-laying by sexually mature virgin crickets, Teleogryllus commodus Walker. High egg-laying activity is associated with PGE₁ PGE₂, 6-keto-PGE₁ and 15-keto-PGE₂, compounds that share the basic prostanoid backbone (C20 substituted fatty acid, 5 membered ring, a 7- and an 8-carbon aliphatic chain), and 9-keto, 11-hydroxyl ring substitutions. PGs without these ring features and other compounds that lack the prostanoid backbone have no or only intermediate egg-laying effects. Adding oxygen functionalities or an aliphatic double bond tends to increase egg-laying activity. Hence, 15-keto-PGF₂ and TxB₂, both of which have an additional backbone oxygen compared with their less active analogues, are highly active compounds. Two of the most active PGs, 15-keto-PGE₂ and 15-keto-PGE_2α, are the products of inactivating metabolism in mammalian systems, describing a fundamental difference in PG biochemistry with respect to mammals and insects.     

Semiempirical modeling of abiotic and biotic factors controlling ecosystem respiration across eddy covariance sites

In this study we examined ecosystem respiration (R_ECO) data from 104 sites belonging to FLUXNET, the global network of eddy covariance flux measurements. The goal was to identify the main factors involved in the variability of R_ECO: temporally and between sites as affected by climate, vegetation structure and plant functional type (PFT) (evergreen needleleaf, grasslands, etc.). We demonstrated that a model using only climate drivers as predictors of R_ECO failed to describe part of the temporal variability in the data and that the dependency on gross primary production (GPP) needed to be included as an additional driver of R_ECO. The maximum seasonal leaf area index (LAI_MAX) had an additional effect that explained the spatial variability of reference respiration (the respiration at reference temperature T_ref=15 °C, without stimulation introduced by photosynthetic activity and without water limitations), with a statistically significant linear relationship (r²=0.52, P<0.001, n=104) even within each PFT. Besides LAI_MAX, we found that reference respiration may be explained partially by total soil carbon content (SoilC). For undisturbed temperate and boreal forests a negative control of total nitrogen deposition (N_depo) on reference respiration was also identified. We developed a new semiempirical model incorporating abiotic factors (climate), recent productivity (daily GPP), general site productivity and canopy structure (LAI_MAX) which performed well in predicting the spatio‐temporal variability of R_ECO, explaining >70% of the variance for most vegetation types. Exceptions include tropical and Mediterranean broadleaf forests and deciduous broadleaf forests. Part of the variability in respiration that could not be described by our model may be attributed to a series of factors, including phenology in deciduous broadleaf forests and management practices in grasslands and croplands.