Plant Tissues

Sequestering Carbon in Forests Human activities are increasing the amount of CO2 in the atmosphere exponentially, with potentially catastrophic effects on Earth’s climate Plants remove CO2 from the atmosphere by photosynthesis and sequester it in their tissues Carbon locked in molecules of wood and other durable plant tissues can stay out of the atmosphere for centuries

Wood Carbon is a major part of cellulose and lignin that reinforce specialized cells and structures that allow a woody plant to grow tall Figure 25.1 Wood. Wood’s porous structure (above) allows it to transport water and nutrients throughout the plant. Despite its porosity, wood is strong enough to support a plant body that can be hundreds of feet tall (opposite). Carbon that gets incorporated into sturdy plant tissues such as wood can stay out of the atmosphere for centuries. Lignin is a class of complex organic polymers that form important structural materials in the support tissues of vascular plants and some algae

Organization of the Plant Body Most flowering plants have aboveground shoots, including stems, leaves, and flowers Most kinds also have below-ground roots Monocots and eudicots differ in tissue organization

The Basic Body Plan Pipelines inside stems conduct water, nutrients, and photosynthetically produced sugars between leaves and roots Roots absorb water and dissolved minerals, and usually serve to anchor the plant; some plants have specialized root cells that store carbohydrates

Three Plant Tissue Systems Ground tissue system Makes up the bulk of the plant body Stores materials, functions in photosynthesis, and structurally supports the plant Vascular tissue system Tubes distribute water and nutrients through a plant body Dermal tissue system Covers and protects the plant body Includes simple and complex tissues

Body Plan of a Tomato Plant Vascular tissues conduct water and solutes Ground tissues make up the plant body Dermal tissue covers root and shoot surfaces

Body Plan of a Tomato Plant shoot tip (terminal bud) lateral bud node flower dermal tissues vascular tissues leaf seeds in fruit withered seed leaf (cotyledon) ground tissues Vascular tissues (purple) conduct water and solutes. They thread through ground tissues that make up most of the plant body. Epidermis, a type of dermal tissue, covers root and shoot surfaces. stem shoots roots primary root lateral root root tip Fig. 25.2, p. 398

Eudicots Versus Monocots Tissues and other characteristics are organized differently in monocots and eudicots: Seeds Flowers Leaves Pollen Vascular Bundles

Eudicots Versus Monocots Monocots and eudicots are named after their cotyledons – leaf-like structures that contain food for a plant embryo cotyledon The primary leaf in the embryo or the “seed leaf”

Eudicot and Monocot Cotyledons A Eudicots In seeds, two cotyledons (seed leaves of embryo) Fig. 25.4a.1, p. 399

In seeds, one cotyledon (seed leaf of embryo) Eudicot and Monocot Cotyledons B Monocots In seeds, one cotyledon (seed leaf of embryo) Fig. 25.4b.1, p. 399

Cotyledons

Flower parts in fours or fives (or multiples of four or five) Eudicot Flowers Flower parts in fours or fives (or multiples of four or five) Fig. 25.4a.2, p. 399

Flower parts in threes (or multiples of three) Monocot Flowers Flower parts in threes (or multiples of three) Fig. 25.4b.2, p. 399

Eudicot and Monocot Flowers

Leaf veins usually forming a netlike array Eudicot Leaves Leaf veins usually forming a netlike array Fig. 25.4a.3, p. 399

Leaf veins usually running parallel with one another Monocot Leaves Leaf veins usually running parallel with one another Fig. 25.4b.3, p. 399

Eudicot and Monocot Leaves

Pollen grains with three pores or furrows Eudicot Pollen Pollen grains with three pores or furrows Fig. 25.4a.4, p. 399

Pollen grains with one pore or furrow Monocot Pollen Pollen grains with one pore or furrow Fig. 25.4b.4, p. 399

Eudicot and Monocot Pollen

Vascular bundles organized in a ring in ground tissue of stem Eudicot and Monocot Vascular Bundles Vascular bundles organized in a ring in ground tissue of stem Fig. 25.4a.5, p. 399

Eudicot and Monocot Vascular Bundles Figure 25.4 Comparing some of the characteristics of A eudicots and B monocots. Vascular bundles throughout ground tissue of stem Fig. 25.4b.5, p. 399

Vascular Bundles

Monocot Eudicot