Q4. Assertion: endosperm formed by the typical NCERT triple-fusion pathway is triploid. Reason: it develops from the primary endosperm cell, whose nucleus forms by the fusion of three haploid nuclei. Are both true, and does the reason explain the assertion?
Both are true, and the reason explains the assertion: the PEN forms by triple fusion of one male gamete and two polar nuclei, and the primary endosperm cell develops into the endosperm (NCERT page 18).
Q5. For double fertilisation in 15 ovules, what minimum numbers of male gametes and successful pollen grains are needed?
Each ovule needs both male gametes of one pollen tube (one for syngamy, one for triple fusion), so 15 × 2 = 30 male gametes, from 15 pollen grains (NCERT page 18).
Q6. Which cells of the embryo sac does NCERT Figure 1.13 (a) label as degenerating after fertilisation?
The synergids and the antipodal cells (NCERT Figure 1.13 (a), page 18).