Question

Student to attempt either option (A) or (B):
(A) 
(i) Write two crucial changes, the seed undergoes while reaching maturity that enable them to be in a viable state until the onset of favourable conditions. 
(ii) Name the oldest viable seed excavated from Arctic Tundra as per the records. 
OR (B) 
(i) Pea flower produced seed sets. Give reason. 
(ii) In case of Polyembryony, an embryo ‘P’ develops from a synergid and the embryo ‘Q’ develops from the nucellus. State the ploidy of embryo ‘P’ and ‘Q’.

Hint:

In polyembryony, embryos can arise from different tissues with varying ploidy levels, such as haploid gametophytic cells (synergids) or diploid sporophytic cells (nucellus).

Answer 1

(A):
Step 1: For (i), essential adaptations include dehydration, enabling dormancy and preventing premature germination, and the formation of protective seed coats to shield the embryo from environmental hazards.
Step 2: For (ii), the Silene stenophylla, unearthed from the Arctic Tundra and approximately 32,000 years old, is the most ancient germinable seed discovered.
OR
(B):
Step 1: For (i), pea flowers achieve seed set through self-pollination, a process facilitated by their cleistogamous nature, ensuring fertilization within the same flower.
Step 2: For (ii), embryo ‘P’, derived from a synergid, is haploid (n) as synergids are part of the female gametophyte. Conversely, embryo ‘Q’, originating from the nucellus, is diploid (2n) because the nucellus is sporophytic tissue.