Transformation of Solarium and Nicotiana Species using an Ri Plasmid Vector

Davey, M. R., Mulligan, B. J., Gartland, K. M. A., Peel, E.,Sargent, A. W. and Morgan, A. J. 1987. Transformation of Solanumand Nicotiana species using an Ri plasmid vector.—J. exp.Bot. 38: 1507–1516. Five Nicotiana species (N. benthemiana, N. debneyi, N. occidentals,N. plumbaginifolia, N. tabacum) and three Solanum species (S.dulcamara, S. nigrum, S. tuberosum) were transformed by wild-typeand engineered Ri plasmids. Depending on the host plant, rootstransformed by Agrobacterium strain A4TIII with an Ri plasmidcarrying a chimaeric nopaline synthase-kanamycin resistancegene, were 3 to 40 times more resistant to kanamycin than rootstransformed by the wild-type plasmid of strain A4T. Similarly,plants regenerated from A4TIII-derived roots of N. debneyi,N. plumbaginifolia and N. tabacum were 8 to 16 times more resistantthan A4T plants, and survived at 400 µg cm³ of kanamycin.A4TIII plants of S. nigrum flowered in vitro at 600–1000µg cm³ of kanamycin. Transformed roots and most regeneratedplants synthesized Ri-speciflc opines, while DNA hybridizationconfirmed the presence of DNA homologous to that from wild-typeand engineered Ri plasmids in transformed plants of S. nigrum. Key words: Agrobacterium, Ri plasmid, transformed roots, plant regeneration, kanamycin resistance.     

The Movement of Sugars into the Sieve Elements of Bark Strips of Willow: I. METABOLISM DURING TRANSPORT

¹⁴C-labelled sugars (sucrose, glucose, and fructose) were suppliedto the cambial surface of bark strips of willow, and in conjunctionwith the aphid stylet technique (Weatherley, Peel, and Hill,1959), the movement into and distribution of activity in thesieve tube sap was examined. As well as sucrose, free hexosesand sugar phosphates were found to contain the ¹⁴C-label, andrapid interconversions occurred between these compounds somewherealong the entry route. Sucrose entry into the sieve elementswas accompanied by at least a partial breakdown into its componenthexoses, and the involvement of a sugar phosphate pool was alsodemonstrated. Possible transformation sites on the entry routebetween the solution bathing the cambial surface and the sieveelement vacuole are discussed.     

Predation on bellerophontiform molluscs in the Palaeozoic

Shell repair assumed to result from failed predation is documented in 66 specimens of Ordovician-Carboniferous bellerophontiform tergomyan and gastropod molluscs to examine the relationship between the distribution and appearance of injuries, shell morphology and the internal anatomy of the molluscs, as well as the attack strategies of the presumed predators. Furthermore, the distribution of repaired injuries from failed attacks along the apertural margin as a reflection of the nature of the margin and emarginations is investigated. Bellerophontiform molluscs are ideal for this study because of their distinctive isostrophic morphology and the possibility to directly compare broad and narrow conchs with either deep or shallow medial emarginations. The results show that taxa with a deep medial emargination in the form of a slit have significantly more medial injuries than lateral ones. Near-equal frequencies of lateral and medial injuries in specimens with a shallow emargination (slit or sinus) suggest random distribution. Shell form (narrow or broad) does not exert overall control on the distribution of injuries except, perhaps, in some broad explanate shells with an insignificant medial emargination. While this suggests that it is the type of medial emargination that governs distribution of injuries in these forms, it is not clear if this is a result of passive selection due to structural geometry or preferential targeting by predators (i.e. site-specific mode of attack). Predation strategies on bellerophontiform molluscs thus seem to be dependent on the morphological features of the shells rather than their interpretation as tergomyan or gastropod.     

SCAPHOPODIZATION IN PALAEOZOIC MOLLUSCS

Abstract:  The relationship of a variety of problematic Early Palaeozoic fossils to the true scaphopods (Late Palaeozoic–Recent) is clarified by the recognition that a trend towards the development of a tubular shell is a recurrent theme within Palaeozoic benthic molluscs. This trend is here termed scaphopodization and can be recognized already in the Cambrian in helcionelloids such as Yochelcionella and Eotebenna . The problematic Early Palaeozoic tubular fossils Janospira , Jinonicella and Rhytiodentalium are interpreted as pseudo-scaphopod derivatives of the apparently exogastric ribeirioid rostroconchs. The direction of coiling of the protoconch indicates that they are not closely related to the true scaphopods, which were derived from endogastric concocardioidean rostroconchs in the Devonian or Carboniferous. Scaphopods show a comparable underlying morphological blueprint to these conocardioideans, but they represent a distinct stream-lining to the infaunal habitat.     

Middle Cambrian monoplacophorans from Bornholm and Australia, and the systematic position of the bellerophontiform molluscs

Berg-Madsen, Vivianne & Peel, John S. 1978 04 IS: Middle Cambrian monoplacophorans from Bornholm and Australia, and the systematic position of the bellerophontiform molluscs
Minute Middle Cambrian monoplacophorans originally reported from Australia are redescribed on the basis of material from the Kalby Clay of Bornholm. A recent classification of Bellerophon. Sinuites and related genera as monoplacophorans is discussed and rejected. Members of the group are returned to the Gastropoda on account of their similarity in ornament, musculature and inferred water circulation patterns, with contemporary fossil helically coiled gastropods. Water circulation patterns are deduced in Protowenella flemingi and support the assignment to the Monoplacophora. Kulhyella poulseni n.gen. n.sp. is described.     

The Movement of Sugars and Phosphates into the Sieve Elements of Bark Strips of Willow

On the basis of the distribution of radioactivity between sucrose,organic phosphates, and hexose in sieve-tube exudate obtainedvia severed stylets, it has been postulated (Peel and Ford,1968), that two pathways exist for the movement of sugars fromthe bathing solution into the sieve elements of bark strips.These pathways were designated the direct and the indirect.Theexperiments described in the present paper show that the distributionof radioactivity in stylet exudate when labelled sugars aremoving by the indirect pathway may be influenced by the simultaneoustransport of other solutes. Phosphates moving by either thedirect or indirect pathway can influence the activity distributionin stylet exudate, as can sugars moving by the direct pathway.     

The Movement of Ions from the Xylem Solution into the Sieve Tubes of Willow

Sieve-tube exudate was obtained as honeydew from colonies ofthe aphid, Tuberolachnus salignus (Gmelin), feeding on isolatedstem segments of willow. Potassium and sodium were shown tobe present in this honeydew. On perfusing the xylem with a solutionof potassium or sodium chloride, a considerable uptake of thecation took place. This uptake was followed, after a periodof several hours, by an increase in the concentration of theparticular cation in the honeydew. A relationship was shown to exist between the concentrationof these cations in a given segment and their concentrationin honeydew obtained from that segment. No such relationshipexisted, however, with different segments. These results arediscussed in relation to the factors which possibly controlthe movement of solutes into the sieve tube.     

Demonstration of Solute Movement from the Extracambial Tissues4

When ¹⁴CO₂ was applied to the leafy shoot of a stem segment,the xylem of which was perfused with distilled water, a proportionof the activity was detected in the xylem exudate, mainly inthe form of sucrose. Experiments in which ³⁶Rb, ²²Na, or ³²P-phosphatewere applied to the cambial surface of a raised portion of barkrevealed that these solutes could also pass into the xylem exudate.With the ions, the amount which moved into the xylem vesselswas dependent upon the time of year at which the experimentswere performed.