Govt. Exams
Entrance Exams
Both ferns and gymnosperms lack vessels in xylem and have sieve cells instead of sieve tubes in phloem, but ferns typically have scattered vascular bundles.
Equisetophytes (horsetails) are characterized by jointed stems with silica deposition, reduced scale-like leaves in whorls, and spores in terminal strobili.
Bryophytes display clear alternation of generations with the gametophyte being the dominant, independent phase while the sporophyte is small and dependent.
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.
