MSc

The present investigations were carried out in the Department of Plantation Crops
and Spices, College of Horticulture, during the year 1995-1996. The study was undertaken
with the objective of understanding the reproductive behaviour and pollination
mechanism in adapathiyan and to unravel the reasons for low fruit set. It was also
envisaged to evaluate the morphotypes for morphological and qualitative differences, to
attempt hybridisation between morphotypes and to assess the seedling variability to isolate
the ideal types.
Flowering pattern of morphotypes were almost similar. A protracted flowering
period of 4-5 months starting from June-November was observed in all the types except
green cordate in which peak season was noted in September- October while in others it
was August-September, Flower bud development in adapathiyan could be divided into 12
arbitrary stages which needed 25 to 28 days from visual flower bud emergence to flower
opening.
Adapathiyan is a profuse flowering plant bearing cymose inflorescence in the leaf
axils with 2-20 flowers per inflorescence and 10-64 inflorescence per plant. Flowers are
bisexual, regular, complete and actinomorphic, typical of milkweed family. The peak
anthesis time was between 09.00 and 09.30 hours. Anther dehiscence was observed in
flowers on fourth day of opening at a time interval of 11.00 to 13.00 hours. Stigma
remained receptive at the anthesis time on the first day of flower opening.
Pollen grains were more or less oval in shape with 50-75µ diameter. Pollen
production per pollinia could not be estimated as a proper suspenion of pollen grains in
water containing extran could not be obtained. Pollen fertility assessed by Alexander's
stain test indicated a high range of 90-100 per cent. In vitro pollen germination m
Brewbaker and Kwack's medium gave only approximate idea about pollen fertility.

Adapathiyan plants are cross pollinated by insects. Xylocopu spp (carpenter bees)
were identified to be the pollinating agents. Among the different modes of pollination
tried, open pollination gave the highest fruit set (12.6%) followed by natural cross
pollination (11.7%) and artificial crossing with germinated pollinia (6.4%). The low fruit
set may be due to the injury caused to the flower during pollination or self incompability
operating at pre and post fertilisation stages. Natural and artificial self pollination did not
result in any fruit set denoting the existence of self incompatibility mechanism but all the
morphotypes were cross compatible.
Fruits required a period of 102-158 days to complete maturity. Purple elongate
types took 150.4 days to complete maturity while green elongate type took 123.4 days.
Each fruit contained numerous seeds in the range of 170-447. Hundred seed weight varied
from 0.60-0.79 g. Seed germination percentage was recorded in the range of 18.00-46.25.
Morphotypes when compared with respect to biometric characters which showed
high positive correlation with yield purple elongate types recorded maximum values for
internodal length (7.64 cm) and number of branches (2.8). Highest value for collar girth
was observed in purple cordate (2.4 cm). These observations suggest purple elongate and
purple cordate to be high yielding. But maximum root yield was observed in purple
cordate (65.6 g per plant) and green cordate (60.6 g per plant) while purple elongate
recorded 49.3 g per plant root yield. Biochemical studies on the morphotypes figured
maximum value for soluble sugars (8.52 %) in purple elongate and minimum in green
elngate type (4.76%). Since the medicinal properties of adapathiyan are attributed to the
soluble sugars, purple elongate types can be considered as medicinally important. Amino
acid content in roots recorded highest value of 0.882 per cent in green elongate type
whereas root protein was maximum in purple cordate (0.76%) and leaf protein in green
cordate (2.27%).
Variability studies in seedlings of hybrid and open pollinated progenies showed
that purple pigmentation and cordate leaf shape dominated in the progenies. Mendelian


ratio was not followed with respect to these characters in the progenies. Evaluation of
seedling progenies with respect to biometric characters showed that the hybrid and open
pollinated progenies did not form separate groups statistically. Thus it is made clear that
self pollination being prohibited inherently, open polliniated progenies are as good as
artificial hybrid progenies and purple elongate and purple cordate are good seed parents.