MSc

The study entitled “Seed production potential, dormancy and seed storage
behaviour in Sida spp.” was undertaken at the Department of Plantation Crops and
Spices, College of Horticulture, Vellanikkara during 2012-2014. The study aimed to
assess seed production potential and characterize dormancy in three Sida species
(Sida alnifolia, Sida acuta and Sida cordifolia) and to standardize ideal pre-treatment
for improving germination and to study seed storage behaviour in Sida alnifolia.
Flowering and fruiting in Sida species was staggered and started four months
after planting. Flowering and fruiting was earliest in Sida acuta and latest in Sida
alnifolia. Maximum seed rain and seed production potential was exhibited by Sida
acuta. The fruits and seeds were biggest in Sida cordifolia.
Physical characterization of dormancy by analysis of seed coat thickness and
embryo size of three species revealed that hard thick seed coat comprising endoderm,
mesoderm, periderm and presence of thick corrugated impermeable cuticle was a
major limiting factor restricting the exchange of water and gases. Acid scarification
brought out reduction in all layers of the seed coat with maximum reduction in cuticle
thickness. Upon storage, the total thickness of the seed coat and individual layers
was slightly reduced but embryo area, perimeter and cuticle thickness increased
slightly.
The physiological conditions tried such as exposure of seeds to different
temperatures, light and dark and exposure to stress by hydration and dehydration
failed to promote germination in fresh seeds. Irrespective of the species, seeds
whether fresh or stored, also failed to germinate without pre-treatment.
Germination studies under field conditions indicated that seeds exposed to
natural weathering showed a spontaneous response on receipt of rain and the
germination was completed in ten days with highest germination (74.50 per cent) in
Sida acuta followed by Sida alnifolia (67.50 per cent) and least in Sida cordifolia
(42.50 per cent).
Biochemical analysis of seeds revealed that species differed in the content of
total extractives, total phenol and total alkaloid and Sida acuta recorded higher
contents of total extractives and total alkaloid whereas total phenol content was
higher in Sida alnifolia. Analysis of the seed leachates indicated species difference in
the content of minerals and electrical conductivity. Sida acuta recorded the highest
potassium and EC values.
Among the eighteen pre-treatments tried for improving germination, chemical
scarification using Conc. H2SO4 was significantly superior and recorded higher
germination per cent and speed of germination. Untreated seeds failed to germinate.
Scarification of seeds with Conc. H2SO4 for higher duration of 30 minutes was
selected as the best treatment considering improvement in water imbibition,
germination per cent, speed of germination, growth and vigour of seedling and
significant reduction in the intensity of dormancy.
Storage studies revealed that upon storage, germination, vigour of seedling and
reduction in dormancy factors were at a positive side compared to fresh seeds.
Storage of seeds under cooler atmosphere either refrigerator or freezer was found to
improve the water imbibition, content of minerals, germination and vigour of
seedling compared to ambient storage.
The present investigations could thus establish that seeds of Sida species exhibit
coat imposed dormancy and require two months of after ripening period, posing
problems in germination. Pre-treatment of seeds with Conc. H2SO4 for 30 minutes is
suggested to bring down dormancy and improve germination and vigour of seedlings.
Exposing the seeds to natural weathering is a simple way of improving germination.
The seeds can be effectively stored under cooler conditions in refrigerator / freezer
for one year or longer which also lowered dormancy and improved germination and
vigour of seedlings.