Showing papers by "Robert Hall published in 1993"
TL;DR: In this paper, two areas of ophiolitic rocks from the Izmir-Ankara-Erzincan suture zone have been studied, and the results suggest that these two areas are probably joined under the Neogene cover.
Abstract: The Izmir-Ankara-Erzincan suture zone is the major Neotethyan suture in northern Anatolia. Two areas of ophiolitic rocks from this zone have been studied. The Besdeǧirmen area, north of Kutahya, includes dismembered ophiolitic rocks (the Kinik Ophiolite) and consists of serpentinized pyroxenites and periodotites together with gabbros and gabbro dykes. The Kaynarca area, south-east of Kutahya, contains medium to low grade metamorphic rocks (mainly amphibolites, amphibole schists and quartz schists) at the base of the Kinik Ophiolite. These two areas are probably joined under the Neogene cover.
The Besdeǧirmen pyroxenites contain spinel with a Cr number [Cr/(Cr + Al)] < 0·60 and are similar to peridotites from mid-ocean ridge (MOR) settings. Gabbro samples contain very calcic plagioclase (An87–100) and magnesio-hornblende as the principal phases; prehnite and zeolite are the most common late stage fracture infillings. The chemistry and mineralogy of the gabbros have features similar to rocks from both MOR and arc settings.
For the Kaynarca amphibolites there are at least two stages of amphibole growth. The first stage amphiboles are brownish green calcic varieties. In contrast, the second stage amphiboles record a medium to high pressure overprint with the growth of fibrous, bluish green varieties. The low crossite content of the amphiboles, and the absence of lawsonite, suggest the transition between blueschist and greenschist facies metamorphism. Trace element and rare earth element data from the amphibolite samples are comparable with oceanic island basalts.
Isotopic dating suggests a Coniacian-Ypresian age for the formation of the Besdeǧirmen gabbros, significantly younger than the Jurassic ages previously suggested for the formation of the main Izmir-Ankara ocean. Unlike many other Tethyan ophiolites the Kinik Ophiolite appears to represent a fragment of a Neotethyan ocean, rather than a supra-subduction zone environment. We suggest a back-arc basin setting for the formation of the Besdeǧirmen ophiolitic rocks.
The Kaynarca rocks formed as an oceanic island or seamount and the Kaynarca amphibolites were formed by intra-oceanic thrusting during the closure of the Izmir-Ankara-Erzincan ocean. Preliminary isotopic data suggest an Albian-Campanian age for this sub-ophiolite metamorphism. The sub-ophiolite metamorphic rocks were overprinted by low temperature-high pressure metamorphism related to Late Cretaceous subduction. Final emplacement is related to the terminal collisional event which occurred at the end of the Cretaceous.
51 citations
TL;DR: The effects of NaCl, feeder cells and the embedding of protoplasts in calcium alginate have been investigated in an attempt to improve culture conditions of recalcitrant sugar beet (Beta vulgaris L.) mesophyll protoplast.
Abstract: The effects of NaCl, feeder cells and the embedding of protoplasts in calcium alginate have been investigated in an attempt to improve culture conditions of recalcitrant sugar beet (Beta vulgaris L.) mesophyll protoplasts. While the use of NaCl in all instances proved detrimental to protoplast development, the other two treatments had clear beneficial effects. Minimum plating densities, necessary to sustain cell division, could be reduced to <5% (<4000 protoplasts / ml) of the control levels and plating efficiencies could be significantly enhanced by approx. 10 fold. Plants could still be regenerated from soft calli derived from mesophyll protoplasts cultured under the modified conditions at a frequency of 20-30 %. In particular, the use of alginate is considered of potentially great importance for the further application of beet protoplasts for other aims e.g. asymmetric hybridization.
26 citations
TL;DR: Cell division could be further increased by adding 25% conditioned medium to the protoplast culture medium, which had a positive effect particularly at low plating densities, where plating efficiencies up to 19 times higher than those for cultures lacking conditioned medium could be obtained.
13 citations
TL;DR: The ability to exchange cytoplasm between genotypes could prove of great benefit in this species, where CMS is routinely expioited for plant breeding and seed production purposes.
Abstract: Beta vulgaris is notoriously recalcitrant concerning biotechnological techniques. However, recently we have been able, for the first time, to report on the obtention of normal, diploid regenerants from mesophyll protoplasts of sugarbeet. This encouraging breakthrough lead to consideration of the application of somatic hybridization techniques to beet. The ability to exchange cytoplasm between genotypes could prove of great benefit in this species, where CMS is routinely expioited for plant breeding and seed production purposes. Detailed experiments have thus been carried out to determine the most appropriate techniques to use to this aim. Different protocols for protoplast pretreatments, fusion, culture, regeneration and DNA analysis have been tested and optimum conditions for each determined. The applicability of the chosen protocols for the production of asymmetric beet hybrids has been investigated. The results of this research will be presented and discussed in the context of other work being carried out in this field on Beta and on other species.
7 citations