Plant Structure

Plant Body Plan• The apical–

basal pattern and the radial pattern are parts of the plant body plan

• They arise through orderly development

Plant Body Plan

• Plant development differs from that of animals

• The plant body is modular, and the growth of stems and roots is “indeterminate”

• Leaves, flowers, and fruits show “determinate” growth.

Plant Cells• Some produce a thick secondary wall• Adjacent cells are connected by plasmodesmata

extending through both cell walls

Angiosperms Monocots

– have a single cotyledon– narrow leaves with parallel veins– flower parts in multiples of three– stems with scattered vascular bundles

Dicots (eudicots)– have two cotyledons– broad leaves with netlike veins– flower parts in fours or fives– vascular bundles in a ring

Figure 34.1

Figure 34.1

Monocots & Dicots

Plant Tissue Systems

• Vascular tissue system conducts water, minerals, and the products of photosynthesis

• Dermal tissue system protects the body surface

• Ground tissue system produces and stores food materials; serves as “anchor”

Vegetative OrgansInclude:• roots, which

form a root system

• stems and leaves, which form a shoot system

Leaves

Plant Body Plan

• Meristems are localized regions of cell division

• Apical meristems at the tips of stems and roots produce the primary growth of those organs

Plant Body Plan

• Shoot apical and root apical meristems give rise to primary meristems

Plant Body Plan• In some plants, the products of

primary growth make up the entire plant body Other plants show secondary growth

• Two lateral meristems, the vascular cambium and cork cambium, are responsible for secondary growth

Plant Body Plan• Young roots have

apical meristems that gives rise to the root cap and 3 primary meristems

• 3 primary meristems produce the three tissue systems

Plant Body Plan

• Root tips have three zones: the zones of cell division, cell elongation, and cell differentiation

Plant Body Plan• The dermal

tissue system consists of the epidermis, part of which forms root hairs responsible for absorbing water and minerals

Roots • The cortex of a young root surrounds

the endodermis which controls access to the stele (pericycle, xylem, phloem)

Roots

• Lateral roots arise in the pericycle• Monocot roots have a central pith region

Real Images - Roots

Dicots Monocots

Real Roots

Stems

• Vascular tissue in young stems is divided into vascular bundles, each containing xylem and phloem

• Pith occupies the center of the eudicot stem

• Cortex lies to the outside of vascular bundles in eudicots, and pith rays lie between them.

Stems

Monocots: vascular bundle scattered

Dicots: vascular bundle in a ring

xylem

phloem

Stems – real images

DicotsMonocots

Stems and Roots • Many dicot stems

and roots show secondary growth, in which vascular and cork cambiam give rise to secondary xylem and phloem

• As secondary growth continues, wood and bark are produced

Figure 34.19 – Part 2Figure 34.19 – Part 2

Secondary Growth

Photosynthesis• Mesophyll is the

photosynthetic tissue of a leaf

• Veins bring water and minerals to the mesophyll and carry products of photosynthesis to other parts of the plant body

Photosynthesis • A waxy cuticle

prevents water loss from the leaf, but is impermeable to carbon dioxide

• Guard cells control opening of stomata, leaf openings that allow CO2 to enter and water to escape

Figure 34.23

Figure 34.23

Cross-section of Leaf

Stomata