BIOL 102 Lecture Notes - Lecture 22: Lygodium, Lycopodiopsida, Water Potential
Document Summary
How to meet the challenge of the land. Get and transport nutrients/h2o to where it"s needed. Megaphylls : leaves as we generally know them. May have evolved as a flattening of branching stem with overtopping growth . Make large true leaves with extensive vascular supply. Lygodium microphyllum : old world climbing fern . Single type of gametophyte produces both mae and female spore. Sporophytes produces spores of two different sexes. Sets the stage for sexual dimorphism of seed plants. Ovule- structure containing the female gametophyte (and egg cell) surrounded by the nucleus and one or two integuments. Provides a protective environment for the developing embryo. In the resting stage it can stay dormant for long periods of time and then grow under favorable conditions. Nutrient reserve for the germination and growth of the embryo. Have only one kind of xylem cell, tracheid, except for gnetophytes, which also have vessel elements like angiosperms.
