BIOL 201 Final: Vascular seed plants summary for exam
Document Summary
Dichotomous branching axes, or stems with terminal sporangia. Cooksonia oldest fossil plant (no leaves only stem) Rhynia: inhibited mudflats, slender leafless aerial stem, tracheids identified in central axis, sporangia on some branches (involved in photosynthesis, consisted of upright dichotomously branched aerial system attached to dichotomously branched rhizomes. Dichotomous branching aerial stems covered with cuticle, upper ones contains stomata. More specialized dichotomy: sporangia that tend to be closer together (rather than separate, not only lateral sporangia but vertical, spine like outgrowths (for photosynthesis) Downwards growing branches may have functioned like roots. Branching = more complex main axis forming lateral branch systems that dichotomize several times. Persisted for about 50 my (420 to 370 mya) Homosporous: simple vascular tissue (xylem surrounded by phloem, i. e. one kind of spore produced in one kind of sporangium mitosis bisexual gameophytes. Larger with a main axis (and lateral branching) Clusters (more grouping (or clustering) of sporangia)
