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The present thesis deals with the reproductive biology and in
vitro culture of Abroma augusta.
The plant, belonging to the family Sterculiaceae, is a large
perennial shrub, reaching a height of 6 to 7 m. It sends off sparse,
slender, somewhat horizontal, shaggy branches bearing series of erect
fruits and showy, maroon pendulous flowers produced terminally in
scorpioid cymes.
Abroma augusta is known to occur in Nepal, Bhutan, China,
Philippines, Indonesia and Malaysia. In India, the species is reported to
be widely distributed throughout the hot and moist parts of the country,
from Punjab and Uttar Pradesh, eastwards to Sikkim, Arunachal
Pradesh, Assam, Meghalaya and Tripura, ascending to 1200 m and
southwards in peninsular India. In wild state, Abroma augusta is found
to grow sporadically often as isolated individuals and sometimes in
small populations growing as escapes along roadsides, on banks of
ponds, left-out private plots, fallow lands, etc. Rarely a few are also
seen to be grown in gardens for the showy, maroon lantern flowers.
Abroma augusta is a valuable medicinal plant and has long been
used in our indigenous system of medicine. The commercial drug is
derived from profusely branched woody roots. The drug is considered
to be a uterine tonic, an emmenagogue, an abortifacient and antifertility agent. It shows contractile action on the uterus and is used for
the treatment of dysmenorrhoea, amenorrhoea, sterility and other
menstrual disorders. Presence of the alkaloid, abromine together with
some alkaloidal bases (choline, betaine) and some phytosterols (βsitosterol, stigmasterol), a basic compound (picrate) and a fixed oil have
been identified in of the plant.
Due to increasing human populations leading to habitat
destruction and other anthropogenic effects, Abroma augusta has
become almost threatened in nature, at least in this part of the country.
Only a limited number of individuals were found to grow in natural
habitats.
The study of the reproductive biology of any plant is most
essential to formulate suitable strategies for its conservation and
cultivation. Therefore, to unravel the reproductive biology of any plant,
details of its pollination biology as well as those of its seed biology are
to be worked out. The study of the pollen biology of a plant, its pollen
vectors, pollination mode, stigma receptivity, floral attractants and
rewards, etc. come under the purview of pollination biology. The seed
biology of a plant is an even broader domain. Seed production, seed
predation, seed dispersal, germination behaviour, dormancy (if any) and
dormancy breaking treatments, vivipary (if any), etc. are important
parameters in understanding the seed biology of a plant species.
However the reproductive biology of Abroma augusta have not
yet been worked out so far. There is no report of any work done on the
pollination biology of Abroma augusta, excepting the mention made by
van der Pijl (1953) that Milichiidae are its floral visitors in Java. Also,
various aspects of seed ecology of the species are yet to be worked out.
Protocols for in vitro culture of the species are hitherto unknown.
In view of the medicinal values, additional economic prospects
and threatened status of Abroma augusta, the present work involving
the detail studies in its reproductive biology and in vitro culture was
undertaken to formulate suitable strategies for successful conservation
and propagation of the invaluable medicinal plant. The work is based
on wild plants growing in small populations or as isolated individuals in
and around Burdwan, Santiniketan and Medinipur, together with four
plants grown in the experimental garden of Botany Department,
Burdwan University.
The thesis comprises altogether five chapters.
In Chapter-I, the Introduction, at first the significance of the
knowledge of reproductive biology and in vitro culture for conservation
and propagation of economically important threatened plants has been
mentioned followed by the nomenclature, synonymy and systematic
position, geographic distribution, habit, ecological settings, economic
importance with special reference to medicinal values, bioactive
compounds, significance of the study of the reproductive biology of
Abroma augusta and a brief review of previous works done in related
taxa have been dealt with briefly.
Chapter-II deals with the details of the material on which the
present work is based and the general methodologies adopted for the
investigations.
Chapter-III
encompasses
the
overall
observations
and
discussions which have been subdivided into following four sections.
Section III A, entitled Floral biology and pollination ecology,
includes the details of the age of attainment of reproductive maturity,
flowering phenology, flower opening, flower structure, flower
longevity, anther dehiscence, pollen production, pollen morphology,
pollen viability, floral visitors vis-a-vis pollinators, activity of the
pollinators in and around the flower, floral attractants and rewards,
pollen presentation and dispersal, stigma receptivity, homogamy,
anthesis, pollination syndrome, ovule production, pollen-ovule ratio and
breeding system of Abroma augusta.
In Section III B, entitled Post-pollination developments,
accounts of fruit-flower ratio, percentage of fruit-set and stages of fruit
development since pollination have been given.
Section III C is entitled as Seed ecology. In this section, seed
production, seed-ovule ratio, seed dispersal, seed predation, seed
structure, vivipary of premature seeds, dormancy and scarification
requirement of freshly harvested mature seeds have been dealt with.
Section III D, entitled as In vitro culture, includes details of the
protocols formulated for callogenesis of Abroma augusta from seedling
explants as well as explants from mature individuals. However, it must
be mentioned that in spite of repeated efforts, no regeneration of the
calluses could be obtained.
Finally Chapter-IV and Chapter-V include the concluding
remarks and the references respectively.
.