Plant Kingdom Introduction
Remember Photosynthesis! Sun + 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2
Remember Respiration! C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + ATP + heat
Plant Kingdom All Plants: Eukaryotic Multi-cellular Most contain chlorophyll in chloroplasts Use mitochondria Live on land and water Do not move from place to place
Plant Kingdom Origin and Evolution For most of the history of the Earth life existed in the ocean. Plants moved to land first Evolved from algae
Early Plants Oldest plant: Rhynia major, Silurian ~420 mya Simple, no seeds, no leaves Rely on water for reproduction Similar plants live today
Rhynia major
Plant Evolution
Conditions compared
Conditions compared In water: Lots of water (duh) Support Light limited Limited CO 2 and O 2 levels
Conditions compared On Land No support Water limited Lots of light Lots of CO 2 and O 2
Adaptations to land Problem: Support. In water density supports plant Land Solution: Cell walls made of cellulose, trees also have lignin for extra support
Adaptations to land Problem: Protection from drying out Land Solution: Cell walls and waxy cuticle that covers leaves and stems. Roots and special cells to carry water in Vascular plants
Classification: Seedless Plants Seedless Nonvascular: No vascular tissues, reproduce with spores. Need water for reproduction. Eg. mosses, liverworts. Seedless Vascular: Vascular tissues, reproduce with spores. Need water for reproduction. Eg.: ferns, horsetails, lycophyta.
Classification: Plants with Seeds Gymnosperms: Vascular. Reproduce with seeds, no flowers. Eg.: pine trees, gingko, firs, junipers. Angiosperms: Vascular. Reproduce with seeds, have flowers. Eg.: grass, rose, corn, daisy.
Evolution of Plants
Classification
Typical Land Plant
Vascular Flowering Plant
Vascular tissue Plants need to move materials through their bodies This is done in the vascular tissues Vascular tissues are tube-shaped cells 2 kinds of vascular tissue: Xylem Phloem
Xylem Dead cells Transport water and minerals from roots up to the shoot
Xylem Cells
Phloem Living cells Transport sugars down from leaves to the roots and across to other parts of the plant sap
Adaptations: Roots Plants use their roots to absorb water and anchor the plant Roots have small fungi called mycorrhizae that live next to them (myco = fungus, rhizae = root) Mycorrhizae are symbiotic fungi that help the plant absorb minerals and water
Mycorrhizae
Adaptations: Leaves Most photosynthesis takes place in the leaves, but sometimes the stem is important too Gas exchange happens through pores in the leaf called the stomata Stomata are surrounded by two cells called the guard cells When there is enough water in the plant the guard cells open up and let CO 2 in and O 2 out A waxy layer (not cells) called the cuticle helps keep water in the plant. It coats the leaves and stems
Leaf Diagram
Leaf structure Most light falls on the upper side of the leaf Most chloroplasts are located in the palisade layer in the upper part of the leaf Most gas exchange happens in the spongy layer on the lower side of the leaf Most stomata are located on the underside of the leaf
Cuticle sem photos http://www.biologie.uni-hamburg.de/bonline/e05/r03.htm
Leaf cross-section
Stomata
Leaf cross section
Water Loss: Transpiration Water moves out of cells by osmosis Water lost through stomata by osmosis is transpiration Plants minimize transpiration by closing the stomata Transpiration helps pull water through plant to the leaves where it is used in photosynthesis (remember water is polar!)
Trees and water
Support In water the density of the water supports the algae On land, plants had to adapt a support system Support is provided by the cell walls (cellulose) Plants also have a chemical called lignin that hardens the cell walls Lignin provides tremendous support
Lignin Support!