Transport in Plants

Transport in Plants

Objectives

  • Explain the function of vascular tissue.

  • Explain how roots help facilitate transport in plants.

  • Explain the functions of stems.

  • Describe the functions of leaves.

  • Explain how transport in plants is facilitated by their structures.

Standard BIO.12.B

  • Explain the interactions among systems performing functions of transport, reproduction, and response in plants facilitated by their structures.

Anchoring Phenomenon

  • What is the world's largest organism?

Vascular Plants

  • Vascular plants have specialized tissues to transport water, minerals, and oxygen.

  • These specialized tissues enable large growth in certain plants.

Roots

Functions of Dermal Tissue

  • Protection and absorption.

  • Made of epidermis cells with thin root hairs that penetrate soil, maximizing surface area for water and mineral uptake.

Movement of Water and Minerals

  • Water and minerals move through the cortex from the epidermis centralized to the root.

  • Cortex also stores photosynthesis products, such as starch.

Endodermis Role

  • Endodermis encloses the vascular cylinder and is vital for water and mineral movement into the root center.

Apical Meristems

  • Produce new cells at root tips; the root cap protects meristem as the root grows through soil, secreting a slippery substance to ease movement.

Water Passage Into Roots

Active Transport

  • Cell membranes of root hairs use ATP-powered active transport proteins to uptake nutrients.

Osmosis

  • High mineral ion concentration in plant cells causes osmotic movement of water into the plant.

Stems

Functions of Stems

  • Provide support, form part of the transport systems (xylem and phloem), protect against predation, produce leaves, branches, flowers, and aid in photosynthesis.

Structure Comparison

  • Monocots have scattered vascular bundles; dicots and gymnosperms have circular arrangements.

Primary and Secondary Growth

Growth Patterns

  • Plant growth, unlike animals, is variable but follows general patterns for size and shape.

Primary Growth

  • Growth occurs through apical meristems at root and stem ends, adding length to the plant.

Secondary Growth

  • The vascular cambium divides to produce secondary xylem (inside) and secondary phloem (outside).

Anatomy of a Leaf

Structure

  • Leaves are optimized for light absorption; thin, flattened blades attached to stems by petioles.

Epidermis

  • Comprised of thick-walled cells and waxy cuticles to protect tissues and reduce evaporation.

Vascular Tissue

  • Leaves’ vascular tissues link directly to stem vascular tissues, facilitating fluid transport (xylem and phloem in veins).

Mesophyll

  • Contains ground tissue cells where photosynthesis occurs - sugars are transported via phloem.

Stomata

  • Small epidermal openings for gas exchange (CO2, water, and O2 diffusion).

How Guard Cells Function

Gas Exchange

  • Guard cells control stomata opening/closing, balancing gas exchange and water loss to survive.

Responses to Environment

  • Stomata open during the day for photosynthesis, close at night to prevent water loss. Environmental conditions also influence stomata behavior.

Capillary Action

Water Properties

  • Plants utilize water's cohesive properties to pull water upwards.

Xylem Structure

  • Composed of tracheids and vessels forming interconnected tubes facilitating water transport.

Adhesion and Transpiration

  • Cellulose-lined tubes facilitate water adhesion, pulling water from leaf ground tissue when transpiration occurs.

Nutrient Transport

Pressure-Flow Hypothesis

  • Phloem transport relies on actively pumping sugars into sieve tubes, driven by pressure differences.

Source to Sink Flow

  • Sugars are moved where needed (sink cells) after being transported from regions rich in sugars (source cells). Osmosis regulates pressure flow by water leaving the phloem.

Vascular Plants - The Four Kingdoms

TEKS Checkpoint

  • Describe how stomata help a plant maintain homeostasis.