Plant Anatomy

Plant Structure Systems

Root System

• Anchors plants + absorb nutrients/water.

• Interactions w/ soil-fungi

• Types:

  • Taproots (Carrot): Storage roots.

    Fibrous roots (Grasses): Major anchoring and absorption role.

    Adventitious: Arrangements like aerial roots (Bonsai).

    Pneumatophores: Aerial roots for oxygen in waterlogged areas (Mangroves).

    Tuberous Roots (Sweet Potato): For nutrient storage.

Stem System

• Photosynthesis (in leaves)

• Gas exchange

• Reproduction (flowers/cones)

• Transporting nutrients and water.

• Types:

  • Runners/Stolon (Strawberries): Asexual reproduction.

  • Rhizomes: Underground stems for propagation.

  • Tubers (Potatoes): Storage for carbohydrates during dormancy.

  • Corms: Thickened stem for starch storage.

Leaf Structure and Function

Function: Gas exchange and photosynthesis.

Structure includes:

• Cuticle (waxy layer): Protects against dehydration.

• Mesophyll layers: Site for photosynthesis, including spongy parenchyma.

• Stomata regulation through guard cells.

Leaf Diversity and Modifications:

• Simple and compound leaves.

• Modifications for specific functions - tendrils for climbing, succulents with spines, carnivorous plants.

Plant Development Mechanism

• Growth - elongation of stem and root

  • Primary growth: lengthening

  • Secondary growth: thickening

• Morphogenesis - changing of forms

• Differentiation - Specializing cells into tissue types

Apical Meristems - cell division growth from root and stem

• Epidermal, Ground, Vascular tissue

3 main: Dermal, Ground, and Vascular

Dermal Tissue

• Function: Protective layer covering roots, stem, and leaves.

• Location: Surrounds whole plant structure.

Vascular Tissue

• Components: Xylem (water) and Phloem (sugars).

• Arranged in bundles

  • Central location in the roots, along the stems and in the leaf veins

Ground Tissue

• The bulk of the plants inner tissue

• Function: Responsible for photosynthesis and storage

• Components: Includes leaves Mesophyll

Types of Ground Tissue

Parenchyma - Most abundant, involved in storage + photosynthesis

• Primary cell wall → retains a nucleus, thin, and lacks 2ndary cell wall

• Mesophyll can also be Parenchyma → Palisade mesophyll (photosynthetic)

Collenchyma - Provides support while also allowing growth in young structures

• Polygonal shapes w/ unevenly thickened cell walls → thicker than Parenchyma

• Primary cell wall only, found in stems

Sclerenchyma - Strongest ground tissue providing max. support

• Has primary cell wall and a thick 2ndary cell wall → latter having lignin

• Types: Fibers and crystalized forms called Sclerids.

• Surrounds the phloem vascular tissue the provide support (older plants)

Components of Vascular Tissue

Xylem - Transports water + minerals from roots to other parts of the plant.

• Tracheid’s: long, narrow overlapping cells. Allows water movement in form of air bubbles

• Vessel Elements: Larger, pipe-like structures w/ perforation plates facilitating water passage

Both cell types are dead at maturity and get lignified secondary walls for efficient water transport.

Phloem - Transports sugars (sucrose)

• Sieve Tube Elements: Porous aiding in sugar solution flow.

• Companion Cells: Assist loading and unloading sugars. Alive at maturity to repair after pest damage.

Cells can produce proteins for damage repair and a long-term plug (callose) for sustained repair.

Dermal Tissue Detail

Epidermis - Outer layer; woody parts (periderm)

• Cuticle: waxy layer (cutin + other waxes) on plants surface

• Stomata: Regulate intake of CO2 and release of water.

• Trichomes: Hairs that deter pest and reduce light absorption for cooling

The 3 Species Concepts → Defines (new) species based off…

1. Biological: Interbreeding natural populations which are reproductively isolated from other groups

2. Morphological: Based on observing morphological feature differences

3. Phylogenetic: Based off shared ancestry and evolutionary history, using genetic data