Tissue culture of forest trees: Clonal multiplication of Eucalyptus grandis L

Axillary shoot proliferation was obtained using explants of Eucalyptus grandis L. juvenile and mature stages on a defined medium. Murashige and Skoog medium (MS) supplemented with benzyladenine (BA), naphthalene acetic acid (NAA) and additional thiamine. Excised shoots were induced to root on a sequence of three media: (1) White's medium containing indoleacetic acid (IAA), NAA and indole butyric acid; (IBA), (2) half-strength MS medium with charcoal and (3) half-strength MS liquid medium. The two types of explants differed in rooting response, with juvenile-derived shoots giving 60% rooting and adult-derived ones only 35%. Thus, the factors limiting cloning of selected trees in vitro are determined to be those controlling rooting of shoots in E. grandis.

Visual ecology of Indian carpenter bees II: adaptations of eyes and ocelli to nocturnal and diurnal lifestyles

Most bees are diurnal, with behaviour that is largely visually mediated, but several groups have made evolutionary shifts to nocturnality, despite having apposition compound eyes unsuited to vision in dim light. We compared the anatomy and optics of the apposition eyes and the ocelli of the nocturnal carpenter bee, Xylocopa tranquebarica, with two sympatric species, the strictly diurnal X. leucothorax and the occasionally crepuscular X. tenuiscapa. The ocelli of the nocturnal X. tranquebarica are unusually large (diameter ca. 1 mm) and poorly focussed. Moreover, their apposition eyes show specific visual adaptations for vision in dim light, including large size, large facets and very wide rhabdoms, which together make these eyes 9 times more sensitive than those of X. tenuiscapa and 27 times more sensitive than those of X. leucothorax. These differences in optical sensitivity are surprisingly small considering that X. tranquebarica can fly on moonless nights when background luminance is as low as 10(-5) cd m(-2), implying that this bee must employ additional visual strategies to forage and find its way back to the nest. These strategies may include photoreceptors with longer integration times and higher contrast gains as well as higher neural summation mechanisms for increasing visual reliability in dim light.

In vitro propagation of Eucalyptus grandis L. by tissue culture

Multiple shoots were induced from nodal segments of five year old trees of Eucalyptus grandis L. on solid medium containing Murashige and Skoog's (MS) Basal medium supplemented with additional thiamine, BAP and NAA. Rooting could be achieved from shoot culture on half strength MS salts or white's medium supplemented with low auxins like IAA, IBA and NAA.

Culture Condition Dependent Changes Of 4-Thiouridine In The Transfer-Rna Of Azotobacter-Vinelandii

4..T~iouridine, a thionucleoside present in the transfer RNA of the free living, nitrogen-fixing ?actenu~ Azotobacter »inelandii shows a culture condition dependent change. When thebacterium IS grown Intheabsen~e ofanyfixed nit~ogen thetRNA contains 4-thiouridine to theextent of 45% of the total sulphur Incorporated. This gets reduced to 5%when the bacterium is grown in the presen~e of.e~ces~ ofamm~nium salt.Instead, a new thionucleoside which appears to be a derivative of 4-thloundlne IS found In the tRNA to the extent of 28%of the total sulphur incorporated.

Modulation of arginine decarboxylase activity in cucumber (Cucumis sativus) cotyledons in short-term organ culture

Among the various amines administered to excisedCucumis sativus cotyledons in short-term organ culture, agmatine (AGM) inhibited arginine decarboxylase (ADC) activity to around 50%, and putrescine was the most potent entity in this regard. Homoarginine (HARG) dramatically stimulated (3- to 4-fold) the enzyme activity. Both AGM inhibition and HARG stimulation of ADC were transient, the maximum response being elicited at 12 h of culture. Mixing experiments ruled out involvement of a macromolecular effector in the observed modulation of ADC. HARG-stimulated ADC activity was completely abolished by cycloheximide, whereas AGM-mediated inhibition was unaffected. Half-life of the enzyme did not alter on treatment with either HARG or AGM. The observed alterations in ADC activity are accompanied by change in Km of the enzyme. HARG-stimulated ADC activity is additive to that induced by benzyladenine (BA) whereas in presence of KCl, HARG failed to enhance ADC activity, thus demonstrating the overriding influence of K+ on amine metabolism.

Isolation and Culture of a Thermophilic Fungus, Melanocarpus albomyces, and Factors Influencing the Production and Activity of Xylanase

Summary: An uncommon thermophilic fungus, Melanocarpus albomyces, was isolated from soil and compost by incubating samples in a glucose/sorbose/asparagine liquid medium, followed by enrichment culture in medium containing sugarcane bagasse as carbon source. The culture filtrate protein of the fungus grown in the presence of bagasse or xylose hydrolysed xylan and some other polysaccharides but cellulose was not hydrolysed. High extracellular xylanase (EC 3.2.1.8) activity was produced by cultures grown on xylose or hemicellulosic materials. The enzyme was induced in glucose-grown washed mycelia in response to addition of xylose or xylan but not by alkyl or aryl β-D-xylosides. Cultures produced higher enzyme yields in shaken flasks than in a fermenter. Gel-filtration chromatography of culture filtrate protein showed the presence of two isoenzymes of xylanase, whose relative proportions varied with the carbon source used for growth. The extent of hydrolysis of heteroxylans or the hemicellulosic fraction of bagasse by culture filtrate protein preparations was greater when the cultures had been grown on bagasse rather than xylose as the inducing substrate. The activity of xylanase preparations was increased when an exogenous β-glucosidase was added.

In vitro culture of the allergenic weed Parthenium hysterophorus L

Excised stem, leaf segments and whole flower of the allergenic weed P. hysterophorus were cultured on Murashighe and Skoog's basal medium supplemented with hormones. Shoot buds readily formed in the stem callus cultured on MS Medium supplemented with IAA and BAP or Kinetin. The leaf callus formed roots alone in a wide variety of media. Suspension cultures were initiated from the leaf and stem callus. The leaf callus elicited a positive patch test response for delayed hypersensitivity in 4 patients suffering from Parthenium dermatitis, thus indicating its ability to synthesise the allergenic principle(s).

A model for visual recognition of alphanumerics

In this paper we propose a hypothetical scheme for recognizing the alphanumerics. The scheme is based on the known physiological structure of the visual cortex and the concept of a short Lino extractor nouron (SLEN). We assumo four basic typca of such units for extracting vertical, horizontal, right and left inclined straight line segments. The patterns reconstructed from the scheme show perfect agreement with the test patterns. The model indicates that the recognition of letters T and H requires extraction of the largest number of features.