Sensitive detection of mycoplasmalike organisms in field-collected and in vitro propagated plants of Brassica, Hydrangea and Chrysanthemum by polymerase chain reaction

A polymerase chain reaction (PCR) protocol, previously designed for amplification of a DNA fragment from aster yellows mycoplasmalike organism (MLO), was employed to investigate the detection of MLO DNA in field-collected and in vitro micropropagated plants. PCR with template DNA extracted from symptomatic, naturally-infected samples of Brassica, Chrysanthemum and Hydrangea, each yielded a DNA band corresponding to 1.0 Kbp. However, no DNA product was observed when either infected Ranunculus (with phyllody disease) or Gladiolus with (symptoms of ‘germs fins’) was used as source of template nucleic acid for PCR; further experiments indicated absence of target DNA in the case of Ranunculus and the presence of substances in Gladiolus which inhibited the PCR. The MLO-specific DNA was detected by PCR using less than 95 pg of total nucleic acid (equivalent to total nucleic acid from 1.9, ug tissue) in the case of field-collected Hydrangea and less than 11.4 pg of nucleic acid (equivalent to total nucleic acid from 19 ng of tissue) in the case of field-collected Brassica. The findings illustrate highly sensitive detection of MLOs in both field-grown and in vitro micropropagated infected plants.     

Hyolith guts in the Cambrian of northern Australia -turning hyolithomorphs upside down

A single specimen of the early Middle Cambrian (Ordian) orthothecimorph hyolith Gudugu-wan hardmani with preserved gut filling has been discovered in the Montejinni Limestone, Wiso Basin, northern Australia. This represents only the eighth such occurrence worldwide. The specimen is unique among orthothecimorphs in retaining the gut filling in combination with the external mould of the operculum and invites revision of the accepted soft-part recon struction in this group, whereby the opercular lateral processes are now recognized to be ventral. Thus orthothecimorph conchs, if horizontal in life, would have been oriented ventral side down, while hyolithomorphs adopted the reverse orientation: horizontal, ventral side up.     

Light-limited growth and photosynthetic characteristics of two planktonic desmid species

1. Staurastrum chaetoceras, originating from a eutrophic environment, and Cosmarium abbreviatum var. planctonicum, from an oligo-mesotrophic one, were grown at 20°C in continuous-flow culture under varied light conditions. 2. Maximum growth rate in S. chaetoceras was approximately 50% higher than in C. abbreviatum, corresponding to a higher photosynthetic capacity. 3. Higher dry weight values and dark respiration rates in C. abbreviatum (compared with S. chaetoceras) support the suggestion from growth-irradiance curves that C. abbreviatum has to invest a greater part of its photosynthetic energy in the construction and maintenance of specific cell components. 4. The differences in growth and photosynthetic parameters might be related to the presence of a copious mucilaginous cell envelope in C. abbreviatum; such an envelope is lacking in S. chaetoceras. 5. The possible ecological significance of these species-specific differences is discussed.     

Fossil epithelial cell imprints as indicators of conodont biology

von Bitter, P.H. & Norby, R.D. 1994 10 15: Fossil epithelial cell imprints as indicators of conodont biology.
Size and growth characteristics of microsculpture polygons on the cup nodes of the bladelike Pa elements of the conodont Lochriea commutata support the hypothesis that they are epithelial cell imprints. They are ˜2–6 pn wide and ˜4–10 pn long and are the same size throughout growth of the element. The epithelial imprints increased in number with growth, either linearly or periodically; the latter possibility may be important for defining specific growth stages of conodont elements. The imprint location on the top of nodes suggests that the latter were tissue-covered and that the scissor-model of function applies to these bladelike Pa elements. The location of the imprints also reflects evolutionary history: a probable ancestor, L. cracoviensis (Belka), also lacks a platform and possesses well-developed microsculpture polygons on broad cup nodes. Finally, correlation between internal white matter and external microsculpture suggests that internal osteocytes may have supplied the external secreting cells with calcium phosphate from the inner storage bank. Conodont biology, fossil epithelial imprints, polygonal microsculpture, Carbonferous, Lochriea commutata .     

The effect of a foliar disease (rust) on the development of Gastrophysa viridula (Coleoptera: Chrysomelidae)

Abstract.

• 1 Gastrophysa viridula Degeer (Coleoptera: Chrysomelidae) and the pathogenic rust fungus Uromyces rumicis (Schum.) Wint. both occur on leaves of Rumex crispus L. and R.obtusifolius L. Individual stages of beetle development, and egg laying, were compared on healthy and infected leaves of each plant species in the laboratory. Oviposition choice was investigated in the field and laboratory.
• 2 Beetles reared on infected leaves of each species had greater larval mortality and slower development than those reared on healthy leaves. Although larvae feeding on infected leaves consumed up to 2.5 times more dry weight than those reared on healthy leaves, they had a lower relative growth rate and pupated at a lower weight. These changes were consistent with the reduced nutritive quality of rust-infected Rumex leaves.
• 3 Fecundity of beetles reared on infected leaves of both species was considerably reduced. Eggs laid by beetles feeding on infected R.crispus leaves also had a reduced viability.
• 4 The beetle developed consistently poorer on healthy R.crispus than on healthy R.obtusifolius throughout its life-cycle. Differences in larval performance were greater between host species than between infected and healthy leaves.
• 5 Oviposition was similar on infected and healthy R.crispus in both the laboratory and field. However, adults consumed less, and laid fewer eggs on infected than on healthy R.obtusifolius. The pattern of egg laying on different aged leaves was affected by rust infection: a greater proportion of eggs was laid on the older, infected leaves, than on the equivalent aged leaves on the healthy plants. Few larvae survived from eggs laid on rusted leaves in the field.