Post on 24-Dec-2015
Plants
• Primary source of energy– Sun -> grass -> deer -> humans
• Carbon cycle– Take in carbon dioxide, produce glucose and
oxygen
Bit of History• Tall grass prairies and forests – Resources for homes & agriculture– Mid – 1800s approx 6.7 million forested acres (1/5)
– By 1900s only 1.5 million acres remained• Breadbasket of the world
– Forest cover has increased to 2.1 – 2.5 million acres• Result from less livestock grazing• State & Federal cost – sharing reforestation programs
Leaves
• “Food Factory” through photosynthesis• Leaf is made of specialized cells• Vary in shape, size, and arrangement – Help identify plants
– Simple, compound– Toothed, pointed, smooth– Lobed, ovate, lanceolate– Whorled, alternate, opposite
• Food manufactured in leaf moves down through the stem to the roots– Used or stored in stem or root
• Sometimes cells in roots, stems, and leaves– Respiration• Oxygen used to produce energy for cells• Too much water can affect efficiency
Types of Stems• Woody or nonwoody (herbaceous)• Stolons– Grow along soil surface – Produce new plants
• Tuber– Store energy
• Cacti– Green fleshy stems– Store water and photosynthesis
• Modified for protection
Stem Structures
• Did you know that a sign nailed 2m (7ft) high on a tree will remain at that height, even though the tree may grow much taller?
Stem Structure
• Grow in length only at tip• Apical meristems– Primary tissues
• Lateral meristems– Secondary growth (diameter)
Stem Features• Node– Leaf attaches to stem
• Internode– Space between nodes– Lateral bud
• Bud– Stem or leaf– Apical meristem enclosed by bud scales
Primary Growth in Stems
• Apical meristem– Dermal, protect plant– Ground, cortex and pith• Pith located at center of stem
– Vascular tissue, occurs in bundles• Xylem (inside) and phloem (outside)
Secondary Growth in Stems• Stems increase in thickness– Cell division in vascular cambium (xylem/phloem)– Dicot and gymnosperms (Monocot Trees may differ)• Stem forms b/w xylem and phloem in vascular bundle
– Vascular cambium • produces 20 xylem (inside) and phloem (outside)
– 20 xylem represents the wood of the plant
• New cambium cells increases stems diameter
• Older xylem stop producing water– Darken wood called heartwood
• Will increase in diameter– Lighter – colored wood called sapwood
• Stays about the same
• Phloem near outside of stem– Bark
• Cork, cork cambium, and phloem– Protective layer– Cork cells die at maturity
• Cannot elongate and will rupture as stem increases in diameter
• Bark pattern (maples and oaks)
Annual Rings• Springwood– Water plentiful– Vas. Cambium form new xylem cells– Wide and thin cell walls
• Summerwood– Water scarce– Vas. Cambium forms smaller thicker cells
• Difference causes a change in appearance• One ring each year used to determine age
Transport of Water• Water and mineral nutrients occur in xylem• Water is constantly evaporating from plant– Stomata– Transpiration
Roots
• Anchor the plant in the soil• Absorb and transport water and mineral
nutrients• Storage for water and organic compounds
Types of Roots• Taproot– Primary root– Rarely more than one – two meters
• Fibrous root system– Numerous small roots
• Adventitious roots– Specialized roots grow from other places– Leaves and stems – corn and epiphytic orchid (aerial roots)
Root Structures• Root cap– Covers apical meristem– Produces oil
• Root hairs– Extensions of epidermal cells– Increase surface area
• Dependent on stems and leaves for energy• Store starch
Sexual and Asexual
• Asexual– No seeds– Leaf, stem, or root
• Sexual– Union of pollen and egg– Pollination– Fertilization • Pollen tube, male gametes unite with egg cell to form
zygote