Seed germination is blocked by numerous problems such as coat and endosperm dormancy, poor and non-uniform germination and long interval for plant establishment due to hypocotyl dormancy. A survey of the natural populations of P. hexandrum was conducted at some high altitude locations viz., Koksar, Kukumseri,Gondla and Chamba in Himachal Pradesh. Seeds and pods thus obtained were used for germination. Initial experiments with both physical and hormonal treatments enabled a quick breaking of dormancy and a high uniform germination within 45 days of sowing followed by high percentage of plant establishment with true leaf emergence
Seed storage studies indicated that viability could be
maintained for about 6 months at 4°C. After
10 months, it diminished with 50% loss in germination. However, when stored for one year, the seedling vigour
was affected as evident from no or reduced cotyledonary leaves of
the seedlings. The adverse effect of storage time on seed viability and vigour was also evident from the increased rate
of ion leakage. Biochemical changes associated with seed storage at
different temperatures were studied. When moisture content of freshly
harvested seeds was about 50%, storage at 4°C was identified to be
ideal.
Morphological and molecular characterization of reproductive development of Podophyllum hexandrum Royle for improvement of seed quality (Funded by the Department of Science and Technology, New Delhi)
The project aimed to investigate the problems associated with the seed germination, seedling establishment and to understand the reproductive development for quality seed production of P. hexandrum. The structure and arrangement of embryonic envelopes in seeds were examined to elucidate their role in germination. Water uptake by the seeds during germination showed a triphasic pattern with a reduced rate during phase III. Thick-walled endosperm cells acted as a physical barrier to the protrusion of radical. During germination, loss of cellular integrity of the endosperm cells in the micropylar region facilitated radicle-protrusion. The multi-layered endosperm and thick testa protect the embryo from extreme environmental conditions.
The biomass and podophyllotoxin contents of already domesticated biotype, (accession No.IHB/BT/42-53, P-1/08-03) was evaluated in first 2 years in the greenhouse at IHBT. The podophyllotoxin in underground parts increased with age and was comparable to plants collected from natural conditions (Table).
1-year old seedlings under green
house conditions
4.6
2-year old seedlings under green
house conditions
33.6
Collected from mature plants
growing in nature but whose age is unknown
42.8
Biomass and podophyllotoxin content in roots and rhizomes of seed-borne plants of P. hexandrum under ex situ condition