Plant Evolution & Anatomy Chapters 29, 30, 35, 38

What you need to know! The function of xylem and phloem tissue The specific functions of tracheids, vessels, sieve-tube elements, and companion cells. The correlation between primary growth and apical meristems versus secondary growth and lateral meristems. The relationship between seed and fruit. The structure and functions of all parts of the flower.

Plants Evolve 500 mya from green algae Evidence: 1.Cellulose made the same way 2.Peroxisomes make enzymes to reduce photorespiration 3.Similar sperm 4.Both use cell plates during cellular division 5.Molecular homology

Alternation of Generations All land plants alternate between gametophytes (haploid) and sporophytes (diploid)

Alternation of Generations Primitive, non-vascular plants are dominated by the gametophyte generation (i.e. moss, liverwort, hornwort) Vascular plants (xylem & phloem) are dominated by the sporophyte generation

The Seed Evolved ~360mya Plant embryos packed with a food supply and protective coat Crucial Adaptations: 1.Reduced Gametophyte (microscopic) 2.Heterospory A.Megaspores  eggs B.Microspores  sperm 3.Ovules and eggs (protects megaspore) 4.Pollen and sperm (waterproof coat for fertilization away from water) 5.Seeds

The Seed Gymnosperms - naked seeds –Conifers (pines, spruces firs, redwoods) Angiosperms – flowers and fruits –Evolved ~200 mya –90% of all plants –Stamen – male –Carpel - female

Plant Organs Roots – anchorage, water & mineral absorption (root hairs), storage –Fibrous roots are a thin mat of roots just below the soil’s surface –Taproots are one thick vertical root with many lateral roots Shoot System: A.Stem – displays leaves 1.Terminal bud – growth upward 2.Axillary Buds – branches or lateral shoots B.Leaves – photosynthesis

Plant Tissue 1.Dermal – skin-like protective covering to keep water (cuticle) and prevent invasion 2.Vascular – Xylem (water and minerals from roots) & phloem (food from leaves) 3.Ground – Anything not dermal or vascular –Pith: inside vascular tissue –Cortex: outside vascular tissue

Plant Cells 1.Parenchyma – photosynthetic cells (most abundant) 2.Collenchyma – supportive cylinders to aid growth (celery strings) 3.Sclerenchyma – super tough cell walls for support (no growth)

Plant Cells 4.Xylem – conduct water A.Tracheids are long thin cells with walls strengthened by lignin B.Vessels are wider and found only in angiosperms (dead at maturity) 5.Phloem – conduct sugar and other organic compounds A.Sieve tubes are chains of cells highly modified for transport (lack nucleus, ribosomes and central vacuole) B.Companion cells support sieve tubes with numerous plasmodesmata

Plant Growth Flowering plants are classified as: 1.Annuals – one year 2.Biennials – two years 3.Perennials – many years Meristems are embryonic tissue responsible for growth throughout the plants lifecycle 1.Apical meristems: primary growth down (roots) and up (stem) 2.Lateral meristems: secondary growth outward (thickness) Morphogenesis is the development of body form and organization for all multicellular life