Introduction to PlantsKingdom: Plantae

Plants: Cell wall Autotroph (photosynthesis) Multi-cellular

12 Divisions (Phyla) Anthophyta = Angiosperms (flowering plants)

Largest # of species (~250,000 - 90% plants) Seed plants: product seed w/in a fruit Key adaptations: flowers & fruits Sporophytes are trees, shrubs, herbs that flower 2 main groups: Monocots & Dicots

Monocots vs. Dicots

Monocot Dicot

• One cotyledon (seed leaf) •Two cotyledon

• Parallel veins in leaves •Netted veins in leaves

• Fibrous root system •Taproot

• Floral parts in multiples of 3 •Floral parts in multiple layers of 4 or 5

• Complex vascular arrangement •Ring vascular arrangement

• Eg. grass, corn, palm, onion, tulip, bamboo •Eg. bean, pea, rose, sunflower

Concept 35.1 The plant body has a heirarchy of organs, tissues, and cells

Basic Organs

• Roots• Stems• Leaves

Types of Tissue

• Dermal• Vascular• Ground

Cell Types

• Parenchyma• Collenchyma• Sclerenchyma• Xylem• Phloem

•Above ground•Stems, leaves

•Underground (usually)•Roots

Shootsystem

Rootsystem

A. Roots Anchors plant, absorbs H2O & minerals, stores

sugars/starches Root hairs – tiny extensions of epidermal cells,

increase surface area for H2O and mineral absorption

Mycorrhizae: symbiosis with fungi

Root hairs

Fibrous Roots Taproots•Mat of thin roots spread just below surface •One thick, vertical root

•Shallow •Many lateral (branch) roots

• Increased surface area •Firmly anchors

•Monocots •Stores food in root

•Dicots

Fibrous Root(scallion)

Taproot(carrot)

Roots

B. Stems Alternating system of nodes (leaf

attachment) and internodes Function: display leaves

Terminal bud – growth concentrated at apex (tip)

Apical dominance: terminal bud prevents growth of axillary buds; growth directed upward, toward light

Axillary buds – located in V between leaf and stem; forms branches (lateral shoots)

Pinching/pruning – removing terminal bud

Stems

Modified stems• Runner or stolin

– Aspen, strawberries, grass– Grow on surface– For asexual reproduction

• Rhizome– Iris, ginger, potato, onion– Grow underground– Store food & DNA for new plant– Tuber: end of rhizome

• Bulb – underground shoot– Onion – storage leaves

C. Leaves◦ epidermis of underside interrupted by stomata

(pores)◦ Mesophyll: ground tissue between upper/lower

epidermis◦ Parenchyma: sites of photosynthesis◦ Cuticle: waxy layer

Three Tissue Systems

A. Dermal Tissue• Single layer, closely packed cells that cover

entire plant• Protect against water loss & invasion by

pathogens• Cuticle: waxy layer• Epidermis, periderm

B. Vascular Tissue

• Continuous throughout plant• Transports materials between roots & shoots

1. Xylem: transport H2O and minerals up from root

2. Phloem: transports food from leaves to other parts of plantstele

C. Ground Tissue

• Anything that isn’t dermal or vascular• Function: storage, photosynthesis, support• Pith: inside vascular tissue• Cortex: outside vascular tissue

III. Cell TypesA. Parenchyma: most abundant

Perform metabolism, synthesizes & stores organic products

B. Collenchyma: grouped in cylinders, support growing parts of plant

C. Sclerenchyma: rigid support cellD. Xylem: water conduction

Tracheids, vessel elements – dead, tubular, elongated cells

E. Phloem: sugar, organic cmpd. conduction Sieve tubes, plates, companion cells – alive

cells which aid movement of sugar

PARENCHYMA CELLS

Parenchyma cells in Elodea leaf, with chloroplasts (LM) 60 µm

80 µmCortical parenchyma cells

Collenchyma cells (in cortex of Sambucus, elderberry; cell walls stained red) (LM)

COLLENCHYMA CELLS

SCLERENCHYMA CELLS

SUGAR-CONDUCTING CELLS OF THE PHLOEM

WATER-CONDUCTING CELLS OF THE XYLEM

5 µm

Fiber cells (transverse section from ash tree) (LM)

25 µm

Sclereid cells in pear (LM)

Cell wall

Sieve-tube members:longitudinal view

30 µm

15 µm

Companioncell

Companioncell

Sieve-tubemember

Plasmodesma

Sieveplate

Sieve plate with pores (LM)

Nucleus

Cytoplasm

Sieve-tube members:longitudinal view(LM)

Vessel elements withperforated end walls

Vesselelement

Tracheids

Pits

Tracheids and vessels(colorized SEM)

TracheidsVessel 100 µm

Primary and Secondary Growth(apical vs. lateral meristems)

Concept 35.3 Primary growth lengthens roots and shoots

Root cap: protects meristem as it pushes through soil; also secretes polysaccharide lubricant

Zone of Cell Division: apical meristem; new cells produced

Zone of Elongation: cells elongate; push root tip ahead

Zone of Maturation: growth & differentiation complete; fully mature cells

Root Hairs

Concept 35.4 Secondary growth adds girth to stems and roots in woody plants

• Involves lateral meristems– Vascular cambium: produces secondary xylem

(wood)– Cork cambium: produces tough covering that

replaces epidermis• Bark = all tissues outside vascular cambium