Download Plant Kingdom Introduction

Plant Kingdom
Introduction
Remember Photosynthesis!
• Sun + 6CO2 + 6H2O C6H12O6 + 6O2
Remember Respiration!
• C6H12O6 + 6O2 6CO2 + 6H2O + 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 CO2 and O2 levels
Conditions compared
• On Land
– No support
– Water limited
– Lots of light
– Lots of CO2 and O2
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 CO2 in and O2 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!