BIO 202 Lecture Notes - Lecture 6: Tracheid, Deciduous, Gymnosperm
Document Summary
Gymnosperms have seeds in cones and circular bordered pits in their tracheids. Lignin: complex polymer composed of many aromatics and oh groups. Circular bordered pills in the tracheids are characteristics of the secondary cell wall. Primary cell wall is deposited while the cell is elongating. Secondary cell wall is deposited to the inside of the primary cell wall after the cell has reached it"s maximum size. Circular bordered pits are formed between adjacent cells where the secondary cell wall leaves gaps/does not develop. Allows for transport of material between cells (pg106) Telome theory-vegetative branches are reduced and fuse to surround the sporangia, forming the integument of the ovule. Ginkgo biloba only living species in this class. We think of gymnosperms as evergreens with needles, but not all are. Have circular bordered pits, no flowers = gymnosperm. Flagella were lost. (the absence of a feature does not make it primitive) Look like palm trees, but palms are angiosperms.
