A. Plants have 3 organs: 1. Roots-
AnchorAbsorb water and nutrients
2. Leaves-Photosynthesis
3. Stems-Support and transport
B. Plant Organs are made of 3 Plant Tissues: Dermal Tissue- Epidermal cells
Outer covering or “skin” of the plant
Vascular Tissue- Xylem & PhloemTransport of water, nutrients,
and sugars
Ground Tissue- CortexFills up the space between the
vascular and dermal tissues
Plant Organs are made of 3 Plant Tissues:
Dermal TissueEx. Cuticle, Trichomes, & Root hairs
Plant Organs are made of 3 Plant Tissues:
Vascular Tissue (two types) a. Xylem- transports water up
b. Phloem- transports sugar to parts that do not photosynthesize
Xylem
Phloem
Plant Organs are made of 3 Plant Tissues:
Ground Tissue-Fills up the space between the vascular and dermal tissues
a. Parenchyma- thin cell walls, in leaves for photosynethesis
b. Collenchyma- thick cell walls, strong and flexible for support, ex. Strings of celery
c. Sclerenchyma- extremely thick cell walls, vey strong for support, ex. Grit in pears
a. b. c.
C. Plants grow at Meristems
Meristems- clusters of undifferentiated cells
Plants are made of merismatic tissueThis tissue undergoes differentiation-
become different cellsFound at the tips of roots and buds, are
apical meristemsThis allows the plant to continue
growing in length above and below ground, primary growth
Primary Growth vs. Secondary Growth
ROOTS There are 2 types of roots: 1. Taproot (dicots)- one long, thick primary
root ex. Carrot
2. Fibrous root (monocots)- many small thin roots bundled together ex. Grasses
B. Root Structure & Growth
1. Root Cap- very tip of the root, protects root as it grows
2. Root Hairs- tiny projections from the epidermis 3. Cortex- layer of ground tissue 4. Vascular cambium- center of root with vascular
tissues
C. Root Function Anchor the plant to the ground Absorb water and nutrients from the soil
Casparian strip- surrounds each endodermis cell and doesn’t allow backflow of water creating root pressure and moving water by osmosis through the xylem tissue
Without this pressure plants would wilt
LEAF: General Structure Blade- thin flattened section used to catch light,
main part of the leaf A. Simple- one blade per petiole
B. Compound- many leaflets per petiole
Petiole- piece of leaf that connects to the stem
B. Leaf Function 1. Photosynthesis- occurs in mesophyll cells 2. Gas Exchange- movement of CO2 & O2 in and
out 3. Transpiration- loss of water through a plants
leaves 90% of water that enters a plant is lost due to
transpiration
Leaf Function: Photosynthesis Photosynthesis- occurs in mesophyll cells
a. Palisade mesophyll- tall, columnar cells, tightly packed
b. Spongy mesophyll- loose cells with many air spaces
c. Vein- vascular tissues to move water & sugars through
Leaf Function: Gas Exchange Gas Exchange- movement of CO2 & O2 in and out
a. Guard cells- cells that control opening and closing of stomata
b. Stomata- pores that allow gases into spaces, spongy mesophyll
Leaf Function: Transpiration
Transpiration- loss of water through a plants leaves (90%)
Process is possible because of waters 2 properties:1. Cohesion- molecules of the
same kind tend to stick together
2. Adhesion- attraction between unlike molecules
Cohesion & Adhesion
STEMS: Structure 1. Node- where leaves attach 2. Internode- regions between nodes 3. Bud- location near nodes, produces new stems
& leavesLateral bud- give rise to branchesTerminal bud- apical meristem
Stem Function 1.Produce- leaves and branches 2.Hold- leaves up into the sunlight 3.Transport- substances between roots and
leavesa. Water pulled through xylem up from roots
○ Root pressure- no back flow○ Capillary action- adhesion of water to tubes○ Transpiration- loss of water through leaves
b. Sugars pushed through phloem○ Pressure-flow hypothesis- water moves food
from high concentration to low
Lenticels
Stem Growth 1. Primary growth- length of stems
a. end of roots and shoots at apical meristems
2. Secondary growth- width/thickness of stemsa. Vascular cambium- merismatic tissue in between
xylem and phloem that produces new vascular tissueb. Cork Cambium- produces outer covering of stems
(cork)c. Wood- layers of xylem
○ 1. Heartwood- old, no longer conducts water○ 2. Sapwood- younger, still conducts water
d. Bark- phloem, cork cambium, and cork; breaks off as stem gets thicker