Plants
Multicellular autotrophic eukaryotes
Plant Characteristics
Cell walls with cellulose
Chloroplasts containing chlorophylls a and b
Store food as starch
Challenges to Plant Life
Obtaining materials needed for life
light
easily available on land (water absorbs much of the sun’s energy)
water
hard to obtain on land; located in the ground where it is too dark for photosynthesis
evaporates easily into the atmosphere
carbon dioxide
higher concentration in air than in water
minerals
on or under the soil
Bringing gametes together for reproduction
water unavailable for flagellated sperm and eggs
use wind and animal pollinators
Dispersing offspring
water unavailable to carry new offspring to distant locations
wind and animals used to disperse offspring
Supporting the body
air provides little support
cell walls provide rigid support for plant bodies
Ultraviolet light
damages nucleic acids
pigments protect cells
Temperature
changes more rapidly and to greater extremes in air
Adaptations to Land
Cuticle
Waxy layer that prevents water loss.
Pores
Stomata: openings usually found on the underneath sides of leaves.
Used in gas exchange.
Two sausage shaped guard cells surround each opening.
Vascular tissues: allow transport of nutrients.
Tissue that forms vessels.
Xylem: transports water up from the roots.
Phloem: transports food down from the leaves.
Seed Dispersal
Plant Types
Non-vascular plants
Dominant gametophyte (haploid) generation
Reproduction requires water
Bryophytes: mosses
rhizoids: root-like structures
leaf-like structures
no stomata
Hepatophytes: liverworts
Anthocerotophyta: hornworts
Vascular plants
Seedless vascular plants
Dominant sporophyte generation
Depend on water for reproduction
Lycophyta: club mosses
Psilotophyta: whisk fern
Sphenophyta: horsetails
Pterophyta: ferns
Seed-producing plants
Gymnosperms
Cycadophyta: cycads
Gnetophyta: gnetophytes
Ginkgophyta: ginkgo
Coniferophyta: conifers
Angiosperms
Monocots
Contains one seed leaf
Produces only herbaceous tissue (no cambium)
Flower parts in multiples of three
Dicots
Contains two seed leaves
Produces woody tissue
Flower parts in multiples of four or five
The Plant Body
Root Structure
Tap root: main body of dicot roots.
Example: carrot.
Fibrous root: all roots of similar diameter.
Monocots, such as grasses.
Root cap protects tips of roots as they grow.
Root Function
Anchorage
Holding plant in the ground.
Tap roots travel deep into the ground.
Fibrous roots help prevent erosion of soil.
Absorption
Take up water and nutrients from the soil.
Conduction
Transport water upward from the ground in xylem.
Transport food downward from the leaves in phloem.
Storage
Store food or water in the tissues.
Example: carrot, sweet potato.
Stem Structure and Function
Contains vascular tissue to transport material to and from the leaves
Epidermal cells may contain chloroplasts for photosynthesis
May be underground or modified for food storage
Leaf Structure
Upper epidermis and lower epidermis protect leaf.
Palisade parenchyma contains chloroplasts.
Generalized plant tissue. May become specialized for transport, storage, or food production.
Chloroplasts: specialized cell organelle that contains chlorophyll, a pigment used to trap light energy for photosynthesis.
Spongy parenchyma contains chloroplasts and surrounds air spaces.
Stomata provide openings into the leaf space.
Leaf Structure
Vein made of a vascular bundle that transports materials to and from the leaf
Cuticle covers upper surface
Waxy, waterproof covering protecting surface plant tissue, such as leaves, stems, flowers, and roots.
Leaf Function
Photosynthesis
May be modified for food storage or for reproduction
Problems facing Plants
Obtaining water and mineral nutrients
roots in contact with moisture
symbiotic fungi
Transporting food and water within the plant
vascular tissues
Preventing evaporation
cuticle
Obtaining gases for photosynthesis and respiration
stomata
Obtaining sunlight for photosynthesis
green leaves or stems
Supporting the plant body
xylem
Coordinating growth
hormones
Getting gametes together
pollen
Dispersing new individuals
seeds
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