Plants:Structure and Function

A protective covering that surrounds the seed

Anchor the plant in place and absorb water and other minerals from the soil.

Carries water and food to the rest of the plant.

Makes the plant's food.

Makes seeds.

Grouped by Characteristics• Vascular

– Three main parts: roots, stems and leaves• Roots can be different sizes:

– Fibrous and tap roots• Storage roots: beets, carrots, sweet potatoes and turnips

– Roots have different functions: anchoring the plant, taking in water and minerals, and store food.

• Nonvascular– Simple; most grow in moist places– No vascular tissues.– Includes mosses, liverworts, hornworts and algae

Vascular Plants: Stems

• Function of Stems– Support, transport of water & food

• Most stems grow upward• Some stems grow sideward

– Types of stems• Green• Woody

– Transport of materials• Xylem & phloem

Vascular Plants: Leaves

• Leaves come in variety of shapes and sizes• Leaves are arranged in different ways

Plant Tissue Groups

Plant Tissues

• A tissue is a group of cells organized to form a functional unit or a structural unit

• Plants have 3 tissue systems:– Ground tissue– Vascular tissue (xylem and phloem)– Dermal tissue (exterior)

Ground Tissue• Parenchyma

– Found throughout the plant, these tissues perform important functions like photosynthesis, food storage, and secretion

• Collenchyma– Structural support in herbaceous plants– Found just under the stem epidermis and along leaf veins

• Sclerenchyma– Hard structural support (trees)– May be alive or dead and still function structurally– One type of sclerenchyma is fiber (wood)

Dermal

• Epidermis - outermost layer composed of single layer of ground parenchyma cells

• Periderm - many layers thick, found on woody plants, replaces epidermis, parenchyma cells

Xylem and Phloem

• Both add structural support• Xylem - conducts water and minerals, long

tapering cells that act as pipes of a sort• Phloem - conducts food

Root Structure

Root Structure• Root Cap

– Protects the growing tip of the root and helps it grow down• Apical meristem

– Root tip where growth occurs• Zone of Elongation

– Area in plant roots where recently produced cells grow and elongate prior to differentiation.

• Zone of Maturation– Cells have differentiated into the different plant tissues

• Root Hairs– Help absorb water and nutrients

• Vascular Cylinder– The center of the root occupied by a core of vascular tissue (xylem and

phloem)

Vascular Cylinder

• Xylem– Tissue whose basic function is to transport water

but will transport some minerals• Phloem

– Tissue whose basic function is to transport sugars throughout the plant

Water Transport in the Root

Internal Leaf Structure

Internal Structure

• Cuticle– Protective covering on the leaf

• Epidermis– Out layer of cells that helps to protect from water

loss, regulate gas exchange, and secrete metabolic compounds

– Stomata are found in the leaf epidermis• Mesophyll

– Interior of the leaf, specialized for photosynthesis

What Prevents Water from Leaving the Plant?

• What type of environmental conditions would increase transpiration?– Sunny, warm, dry, windy weather all increase evaporation

• Guard cells control stomata– Stomata = pores in leaves– Keep stomata open during day and closed at night– How do they open? Close?

• Ions move into vacuoles creating concentration gradient• Water moves into vacuoles via osmosis• Reverse gradient, lose water

What Prevents Water from Leaving the Plant?

Tree Structure

The Big Question:How does water

move from roots to leaves?

Transpiration moves water up xylem vessels

Transpiration moves water up xylem vessels

Transpiration moves water up xylem vessels

Transpiration Moves Water Up Xylem Vessels

• Transpiration exerts an upward pull– What is responsible for this pull?

• Diffusion! And a bonus – no energy required!!

• The “string” of water is held together by cohesion and is helped upward by adhesion

• Is known as “transpiration-cohesion-adhesion mechanism”