Srivastava Shyam C.: Compressed Triassic fructifications from India and their usefulness in Gondwanas. In: Plant cell biology and development, (6). pp. 12-25. (1995)
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Absztrakt (kivonat)
There has been increased emphasis on the study ot Triassic fructifications from India during the last two decades. Dicroidium bearing Triassic beds of Nidpur have yielded excellently preserved compressions of fertile organs in attached and detached forms; these fertile structures associated with their vegetative remains are represented by micro- and megasporangiate organs and exhibit a variety of morphological forms assignable to different plant groups. Systematic studies of the fructifications suggest recognition of major taxonomic groups: Phycophyta, Bryophyta, Pteridophyta, Pteridospermophyta, Cycadophyta, Ginkgophyta and Coniferophyta; considering the diversities of reproductive structures, found in various groups, strides have been made to trace the ancestral relationships. The possible affiliations of the various fertile and vegetative organs are discussed, based on their distinctive epidermal features, comparative morphology, patterns of arrangements, in situ spore-pollen morphography, seed characters and the distributions of fossils. Epidermal studies of fertile structures enhanced taxonomic resolution is useful for interpreting the systematica and phylogeny. Some enigmatic fertile forms are interpreted as "morphological intermediates" a potential link to Paleozoic relatives and during the course of evolution may have given rise to Mesozoic forms spread over Gondwanic continents. Consistent association of certain fructifications underlines their usefulness in correlation, interpretation of systematica and the time of origin of major groups. Ptemchus - a pollen organ is such an example, always associated with leaf - genus Dicroidium which is by far the most common, ubiquitous and diverse fructification throughout the realm of Triassic in Gondwana continents. These taxa co-occur nowhere except in regions that were once parts of ancient Gondwanaland. This kind of consistent association can be used to infer the morphoelement comprising the unattached organs. The seed taxon Savitrispermum is quite prolific and plays a significant role in the correlation of the Triassic of Gondwana. Also noteworthy is the seed cone Nixtia, displaying a line of development in the direction of Cycadales and elucidates the origin of zamoid cycads. Other significant fructifications like Nidpuria and Lelestrobus are characterized by having pteridophytic structural organization but bear gymnospermous pollen grains. Likewise, Bosea also appears to be an intermediate form because of the pattern of its microsporophyll bearing pendant sporangia somewhat identical with that of Crossotheca but it is radically different in bearing costate pollen.
| Mű típusa: | Cikk, tanulmány, mű |
|---|---|
| Befoglaló folyóirat/kiadvány címe: | Plant cell biology and development |
| Dátum: | 1995 |
| Kötet: | 6 |
| ISSN: | 0866-5443 |
| Oldalak: | pp. 12-25 |
| Nyelv: | angol |
| Kiadás helye: | Szeged |
| Befoglaló mű URL: | http://acta.bibl.u-szeged.hu/46855/ |
| Kulcsszavak: | Paleobotanika - Triász-kor, Palinológia - Triász-kor |
| Megjegyzések: | Bibliogr.: 24. p. ; ill. ; összefoglalás angol nyelven |
| Szakterület: | 01. Természettudományok 01. Természettudományok > 01.06. Biológiai tudományok |
| Feltöltés dátuma: | 2017. júl. 11. 13:43 |
| Utolsó módosítás: | 2026. jan. 20. 12:22 |
| URI: | http://acta.bibl.u-szeged.hu/id/eprint/47809 |
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