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Frequently asked questions (FAQS):
Q.1 Where from was Rhynia discovered
Ans. Rhynia was discovered by Kidson and Lang (1917)
from Rhynie Chert bed in village Rhynine of Aberdeenshire
disrict of Northern Scotland.Rhynia is thus named for
the village Rhynine were the fossil was first discovered.
They were fossilized petrifactions.They flourished during
Devonian period.
Q.2 Give an account of general morphology of Rhynia:
The plant body of Rhynia was simple,herbaceous with
slender, branched creeping rhizome bearing an upright
stem with dichtomous branches. Branching of Rhynia
is both dichotomous and adventitious. The sporophyte
comprised a creeping rhizome with rhizoids and uprght
dichotomously branching axis.
Q.3 Highlight the evulutionary importance of Rhynia?
Rhynia is evolutionarily very important as it is belived that
Rhynia and its relatives gave rise to large number of land
plants, including angiosperms. Zimerman’s telome therory
is based on the Rhynia like plants. It reveals possibility
of complex forms have been formed from Rhynia l ike
ancestor.
Q4 What are the primitive land characters of Rhynia?
Structure of Rhynia shows a number of
Primitive land characters which are parenchymateous
organisation of the axis which had differentiated into
parts like epdermis, cortex and stele. This reduced the
total exposed area in the desicating habitat. Presence of
a thick layer of cuticle on epidermis reduces the loss of
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water from aerial parts. Stomatal pore was regulated with
guard cells in order to control loss of water from the plant.
Sporangia were terminal for beter dispersal of spores.
Sporangial wall and spore wall was very thick to avoid
desication.
Q.5 The genus Rhynia had both sporophytic and
gametophytic generations, elaborate:
Rhynia showed both sporophytic aswell as
gametophytic generations. Rhynia has a sporophyte
which shows two main morphological parts of a creeping
rhizomatous part which gave rise to an upright aerial axis
bearing terminal sporangi. Remyophyton delicatum which
was a unisexual gametophyte of Rhynia. This promoted
out breeding.Its axis was also vascular. The development
of gametophyte was endoscopic 1,e development of
gametophyte started inside the sporangia. Gametophyte
developed through four stages viz. Globular stage, Tear
drop stage Protocorm stage and gametophore stage.
Q.6 Why R. Major is not now regarded as a species of
genus Rhynia:
Ans.Anotomical characters of R. major are different. Edwards
(1986) concluded that R. major is not related to R. gwynevaughaii because former did not have xylem tracheids. He
termed the water conducting cells of R. major as hydrom and
outer food conducting cells as leptome. He did not regard R.
major as a vascular plant and named it Aglaophyton major.
Q.7 What type of environmental conditions were present in
the habitat of Rhynia during Devonian:
Ans. Habitat of Rhynia was very harsh. These plants lived
near volcanoes, with sulphur rich atomosphere and acidic
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soils.
Q.8 Xylem in Rhynia was evolutionary primitive elaborate:
Aerial axis of Rhynia was protostelic. Xylem tracheids were
annular and occasionally spiral, which are found in primitive
plants.
Q.9 Comment on the nature of hemispherical buldeges:
Ans. Surface of the axis bore membraneous conspicuous
emergences or hemispherical projections. These are
interpreted to be formed due to damage og sucking insects.
Q.10 What was the nature of rhizoids in Rhynia:
Rhynia lacked roots, but rhizoids were present which helped
in absorption and anchorage. But nature of rhizoids was
not clear. Whether they were unicellular, multicellular or
branched or unbranched no evidence is present.
Q. 11 Write a short note on the sporangia of Rhynia:
Ans. Sporangia of Rhynia were club shaped and terminal.
Their three layered wall consisted of epidermis, a three ceel
thichk middle layer and inner thin walled tapetum.Some
spores were in the form of tetrads, which suggested that
they were formed by meiosis.
Q 12. What is webbing
Ans. Webbing is an elementary process in plant development.
In Webbing or syngensis the adjacent telomes and
mesomes developed parenchyma between them.It led to
leaf formation.
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Q13.What is overtopping
Ans. Overtopping was first step which eleminated dichotomy,
one branch(main axis) overtoped the other which remained
small and lateral. Thus short and long branches were
developed.
Q 14. Comment on the Merks view of Rhynia gametophyte
Mercker (1955, 59) is of the view that the rhizomematous
parts of the Rhynia represent the gametophyte while as
the aerial portion represents the sporophyte. This view is
supported by the presence of the flask shaped structures
or cavities in the subtarenian portin which were supposed
to be the degenerated sex organs. Besides this, there was
a group of four cells with an opening on the surface, which
resembles the ptridophyte archegonia.
Q 15. Write a short account on Rhynia
Ans. Rhynia is a fossil pteridophydes which was discovered
by Kidson and Lang (1917) from Rhynie Chert bed in village
Rhynine of Aberdeenshire disrict of Northern Scotland. Habitat
of Rhynia was very harsh. Rhynia and all its contemporary
plants were terrestrial xerophytes. Internal structure of the
plant reveals a number of primitive characters. Nothing
substantial was known about the gametophyte of Rhynia
till recently, but unequivocal gametophytes of Rhynia have
been discovered. Rhynia is evolutionary very important as
it is belived that Rhynia along with it‘s relatives have give
rise to large number of land plants including angiosperms.
Zimerman‘s telome therory is based on the Rhynia like
plants. It reveals the possibility of how complex forms could
have developed from Rhynia like ancestors.