Govt. Exams
Entrance Exams
The mature embryo sac with 7 cells (3 antipodal cells, 2 synergids, 1 egg cell, 2 polar nuclei) represents the female gametophyte in angiosperms.
Gymnosperms lack true vessels and rely on tracheids for water conduction and mechanical support in the xylem.
The central cell of the female gametophyte contains two polar nuclei (2n total). When one sperm nucleus (n) fuses with this central cell, the resulting endosperm is triploid (3n).
The typical angiosperm embryo sac (Polygonum type) is 7-celled and 8-nucleate consisting of egg apparatus, central cell, and synergid cells.
The mature male gametophyte (pollen grain) in gymnosperms contains two sperm cells (after mitosis of generative cell) and one tube cell.
Bryophytes were the first plants to develop adaptations for land, including a cuticle (though thin) and stomata for gas exchange, though some bryophytes retain both.
The nucellus is a multi-cellular tissue surrounding the embryo sac that provides nutrition to the developing female gametophyte.
After fertilization, the zygote undergoes mitosis to form suspensor and embryo proper, which together develop into a seedling after germination.
Ring arrangement of vascular bundles, cork cambium, and secondary growth are characteristics of dicot gymnosperms like Pinus and Cedrus.
The integument of the ovule develops into the seed coat (testa), which protects the embryo and endosperm in seeds of both gymnosperms and angiosperms.
