Entrance Exams
Govt. Exams
A sorus (plural: sori) is a cluster of sporangia arranged on the abaxial surface of fern leaves, often covered by an indusium for protection.
Presence of archegonia, independent dominant gametophyte, and absence of true roots are distinctive features of bryophytes including mosses and liverworts.
As the endosperm develops and stores nutrients, the nucellus degenerates, allowing the endosperm to provide nutrition directly to the embryo through absorptive cells.
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.
The ovule arises as an outgrowth from the placenta (megasporophyll) and projects into the ovary cavity.
Polyembryony occurs through apomixis (asexual reproduction) and cleavage polyembryony where the embryo sac or embryo divides to form multiple embryos.
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.
Rhynia and Cooksonia fossils are from the Silurian period, representing early vascular plants with primitive conducting tissues.