paleobot
any
S.Y.B.Sc. /{B} /{262} SEMESTER-4
PRAVIN PRADHAN
}
PALAEOBOTANY
Introduction to PALAEOBOTANY
Derived from Greek words
“Palaeon” = old and “Botany” = study of plants.
Deals with the identification of plants remains of geological age, and its reconstruction.
Includes the study of terrestrial plant fossils, as well as Marine ones such as seaweeds.
Importance of palaeobotany
Reconstruction of ancient ecological systems and climate, known as palaeoecology and palaeoclimatology respectively.
Study of green plant development and evolution.
Important to the field of Archaeology.
HISTORY
First fossil record was found in SILURIAN period of PALAEOZOIC ERA.
Spores and cuticles, were found in ordovician period.
Angiosperms (flowering plants) evolved during the Mesozoic, and Early Cretaceous. (approx. 130 million years ago)
PLANT FOSSILS
A plant fossil is any preserved part of
a plant that has long since died.
Bits of charcoal that are only a few hundred years old.
RHYNIE CHERT found
in SCOTLAND bearing the
fossils of mosses and lycopods.
(see image beside)
EVOLUTION OF MORPHOLOGY
LEAVES
Evolved to originate as spiny
outgrowths.
Before the evolution of leaves,plants had the photosynthetic
apparatus on the stems.
The branching pattern of
megaphyll veins may belietheir origin as webbed,dichotomising branches.(see image right)
Leaf lamina.
The leaf architecture
probably arose multiple
times in the plant lineage
(see image left)
Importance ofevolved leaves
To protect early plants from herbivory.
Better transpiration rates and gas exchange.
Helps to carry out better Photosynthesis.
Figure beside shows the diversity in leaves
evolved according to their suitable
environmental conditions.
ROOTS
Organs differentiated from stems – did not arrive until later.
Roots are rarely preserved in the fossil record.
Their evolutionary origin is sparse.
Rhizoids are prehistoric roots.
Rhizoids probably evolved more than once.
The root of
Lepidodendrales
(image beside)
Importance ofevolved ROOTs
provide anchorage to the substrate.
provide a source of water and nutrients from the soil.
allow plants to grow taller and faster.
Stigmaria, a common
fossil tree root.
(image beside)
Stems
Ferns were the first to have a growth of woody habit.
Progymnosperms were the first plants to develop true wood.
The trunk of early
tree fern Psaronius,
showing internal-structure.
(image beside)
Importance ofevolved STEMs
The most obvious advantage is the harvesting of more sunlight for photosynthesis.
Spores can be blown greater distances if they start higher.
Provided support and water transport.
External mold of
Lepidodendron trunk.(image beside)
SEEDS
Germination of microgametophytes and megagametophytes, paved the way for seeds.
Seed plants from Belgium has been identified the earliest seed plants - about 20 million years.
The first "spermatophytes" (seed plants) i.e. the first plants to bear true seeds
are called "pteridosperms“
(seed ferns).
The fossil seed
Trigonocarpus
(image beside)
Importance ofevolved SEEDs
increased the success rate of fertilised gametophytes.
increases the biodiversity of forests.
Helps the plant to survive for
generations.
The transitionalfossil of seed of
Runcaria.(image beside)
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