Paleobotany

paleobot

any

S.Y.B.Sc. /{B} /{262} SEMESTER-4

PRAVIN PRADHAN

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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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