1. Chapter 24 PLANT STRUCTURE and FUNCTION

2. Overview of PLANT STRUCTURE
Reproductive shoot (flower)
Terminal bud
Node
Internode
Terminal
bud
Vegetative
shoot
Blade
Petiole
Stem
Leaf
Taproot
Lateral roots
Root
system
Shoot
Axillary
Vegetative organs are concerned with growth and nutrition
Flowers, seeds, and fruits are structures involved in reproduction.

3. Flowering Plants: Monocots or Eudicots
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Seed
Root
Stem
Leaf
Flower
Monocots
Root xylem and
phloem in a ring
Vascular bundles
scattered in stem
Leaf veins form
a parallel pattern
Flower parts in threes
and multiples of three
One cotyledon in seed
Eudicots
Root phloem between
arms of xylem
Vascular bundles
in a distinct ring
Leaf veins form
a net pattern
Flower parts in fours or
fives and their multiples
Two cotyledons in seed 10

4. ROOTS
Roots
Generally, the root system is at least equivalent in size and extent to the shoot system
Anchors plant in soil
Absorbs water and minerals
Produces hormones
Root hairs:
Projections from epidermal root hair cells
Greatly increase absorptive capacity of root

5. Roots 1
Roots anchor plant in soil, absorb minerals & water, & store food
fibrous roots (1)
mat of thin roots that spread out
monocots
tap roots (2)
1 large vertical root
also produces many small lateral, or branch roots
dicots
root hairs (3)
increase absorptive surface area 2 3

6. Shoots Shoots consist of stems, leaves & buds Stems Buds
nodes = points at which leaves are attached
internodes = stem segments between nodes
Buds
growth of shoot
terminal or apical bud = at tip of plant
axillary bud = in nodes on stem

7. STEMS Support for the plant body Carries nutrients throughout plant
Defense system to protect against predators and infection
Few millimeters to 100 meters

8. LEAVES
Leaves are the major part of the plant that carries on photosynthesis
Foliage leaves are usually broad and thin
Blade - Wide portion of foliage leaf
Petiole - Stalk attaches blade to stem
Leaf Axil - Axillary bud originates
Tendrils - Leaves that attach to objects
Bulbs - Leaves that store food

9. colored leaves (poinsetta)
Modified leaves
tendrils (peas)
spines (cacti)
succulent leaves
colored leaves (poinsetta)

10. Interdependent systems
Both systems depend on the other
roots receive sugars & other nutrients from photosynthetic parts
shoot system depends on water & minerals absorbed from the soil by roots
sugars
water

11. Putting it all together
Obtaining raw materials
sunlight
leaves = solar collectors
CO2
stomates = gas exchange
H2O
uptake from roots
nutrients

12. TISSUES OF FLOWERING PLANTS
Dermal
“skin” of plant
single layer of tightly packed cells that covers & protects plant
Vascular
transport materials between roots & shoots
xylem & phloem
Ground
everything else: storage, photosynthetic
bulk of plant tissue

13. DERMAL TISSUE Dermal Tissue Outer covering
Single layer of cells consisting of
Cuticle – waxy coating
Hairs
Guard Cells that surround stomata

14. Those would’ve been great names
Cells of GROUND TISSUE
Those would’ve been great names
for my kids!
Parenchyma
“typical” plant cells = least specialized
photosynthetic cells, storage cells
tissue of leaves, stem, fruit, storage roots
Collenchyma
unevenly thickened primary walls = support
Sclerenchyma
very thick, “woody” secondary walls (lignin) = support
Fibers (rope); Schlereids (grittiness, hardness of nuts, peach pit)
rigid cells that can’t elongate
dead at functional maturity

15. VASCULAR TISSUE Transports materials in roots, stems & leaves Xylem
carry water & minerals up from roots
tube-shaped dead cells
only their walls provide a system of microscopic water pipes
Phloem
carry nutrients throughout plant
sugars (sucrose), amino acids…
tube-shaped living cells

16. Xylem Dead at functional maturity Cell elongated into tubes tracheids
Aaaaah…
Structure-Function
again!
Dead at functional maturity
Cell elongated into tubes
tracheids
long, thin cells with tapered ends
walls reinforced with lignin = support
thinner pits in end walls allows water flow
vessel elements
wider, shorter, thinner walled & less tapered
perforated ends walls allows free water flow from one hole to the next

17. Phloem Living cells at functional maturity Cells
Aaaaah…
Structure-Function
again!
Living cells at functional maturity
lack nucleus, ribosomes & vacuole
more room: specialized for liquid food (sucrose) transport
Cells
sieve tubes
end walls, sieve plates, have pores to facilitate flow of fluid between cells, pump sugars
companion cells
nucleated cells connected to the sieve-tube
Surround sieve tubes; support phloem cells

18. Phloem: food-conducting cells
sieve tube elements & companion cells

20. Vascular tissue in herbaceous stems
dicot
trees & shrubs
monocot
grasses & lilies

21. What I should eat….
What I actually eat….

22. Root structure: dicot
phloem
xylem

23. Root structure: monocot