Plants - Back to Basics ¨ Why are plants important? ¨ Plant structures - from the bottom up ¨ Plant life processes - making food and using energy (respiration, photosynthesis, transpiration)

Energy Flow ¨ Energy reaches Earth from the sun (electromagnetic energy) ¨ Solar energy is transformed into chemical energy (sugars) by plants ¨ All animals ultimately rely on energy captured by plants

Roots ¨ absorb water and minerals from soil ¨ anchor plant in soil or other substrate ¨ store food ¨ xylem tissue transports water and minerals from roots to other parts of plant (xylem UP) ¨ obtain sugars and other organic nutrients from the leaves

Respiration ¨ process by which energy is released from sugars ¨ requires oxygen ¨ plants take in oxygen through their roots for use in respiration

Stems ¨ shoot = stem and leaves ¨ nodes = where leaf is attached to stem ¨ stem consists of nodes and internodes (segments between nodes)

Stems, continued ¨ terminal bud = point at tip of shoot with developing leaves, nodes and internodes ¨ axillary bud = buds at nodes; new branches grow from axillary buds

Modified stems ¨ stolons = horizontal stems above ground ¨ rhizomes = horizontal stems below ground ¨ bulbs = vertical, underground shoots (stems with modified leaves)

Leaves ¨ solar panels ¨ blade with petiole (stalk) ¨ petiole = joins the leaf to a node on the stem (grasses and some other plants lack petioles)

Leaf Arrangement ¨ Simple leaf vs. compound leaf l simple, compound (palmate, pinnate, doubly pinnate) ¨ Venation l parallel, palmately net-veined, pinnately net-veined

Leaf Shape ¨ Deciduous = plants that drop all of their leaves at one time once a year l in response to seasonal changes (temperature, precipitation) ¨ Evergreen = plants with green leaves throughout the year l leaves are shed and replaced individually

Leaf anatomy

Photosynthesis ¨ process by which plants make sugars (convert sun’s energy into food) ¨ takes place in chloroplasts ¨ uses carbon dioxide and water to make sugars and oxygen ¨ phloem tissues transport sugars to non-photosynthetic parts of the plant (phloem DOWN)

¨ plants use sugars for food (energy) and to make larger molecules, such as cellulose ¨ plants store extra sugars as starch ¨ most important process for life on Earth Photosynthesis, continued

Photosynthesis vs. Respiration Photosynthesis Produces food Stores energy Occurs in cells that contain chloroplasts Releases oxygen Uses water Respiration Uses food for plant energy Releases energy Occurs in all cells Uses oxygen Produces water

Transpiration ¨ transpiration is the loss of water from a plant through evaporation ¨ transpiration drives the movement of water, minerals and nutrients through the plant

Transport from roots to stems ¨ roots take in water and dissolved minerals ¨ roots take in oxygen and give off carbon dioxide ¨ water and minerals transported up from roots by the xylem ¨ transpiration through leaves (stomata) creates force that pulls xylem sap upwards

Transport in stems and leaves ¨ leaves take in carbon dioxide and give off oxygen ¨ sugars created by photosynthesis transported to rest of plant by phloem

Plant reproduction ¨ Reproduction in vascular plants with seeds l seed = embryo with stored food in a protective covering 360 million years ago l flowering plants = seeds in protective chamber (ovary) 130 million years ago

Gymnosperms ¨ seeds not in a protective chamber (“naked seed”) ¨ most bear cones (pollen cones and seed cones) ¨ conifers are the most diverse group of gymnosperms

Gymnosperms cycad Douglas fir seed cone Alaska yellow-cedar

Angiosperms ¨ flowering plants = seeds in a protective chamber (ovary) ¨ two major divisions of angiosperms: ¶ monocots · dicots

Flowers Ê sepal Ë petal Ì stamen l filament l anther Í carpel (pistil) l ovary l style l stigma X fruit = mature ovary

Flowering plant life cycle seed germinating seed seedling mature plant with flowers fruit (develops from ovary) seed (develops from ovule) germinated pollen grain on stigma pollen tube ovary ovule

Pollination  Fertilization ¨ pollen grains attach to stigma l pollen contains sperm cells ¨ pollen grain germinates ¨ pollen tube grows toward and into the egg cell ¨ fertilization occurs when a sperm nucleus unites with an egg nucleus ¨ cross-pollination vs. self-pollination

Flowers Banksia plants in Australia Fruit with seed pods open

Animals and Flowering Plants: Adaptations ¨ pollination l modified flowers insects small mammals (esp. bats) birds ¨ seed dispersal l carried l passed through digestive tract