Plant Structure and Function

Specialized Tissues in PlantsPlant Organs: Roots, Stems, and LeavesRoots

Anchor the plant and absorb nutrients and water Mutualistic relationship with mycorrhizae and

rhizobacteria

Transport Nutrients to the plant

Store Food

Specialized Tissues in PlantsStems

Support the plant

Transport water and nutrients

Protect against predators and disease

Specialized Tissues in PlantsLeaves

Conduct photosynthesis

Increased SA:V with leaf size

Protect against water loss Waxy cuticle Stomata and Guard Cells

Specialized Tissues in PlantsPlant Tissues: Dermal, Vascular, and Ground Tissue

Specialized Tissues in Plants

Dermal TissueCovers the plant

Epidermis (epi = upon) – single layer of cells on the outside of the plant

Cuticle – layer of wax that covers the epidermis and prevents water loss (polarity?)

Trichomes – tiny hairlike projections for protection Bark – covers the epidermis in woody plants Root hair cells are found on the epidermis of roots

to help absorb water (SA:V)

Specialized Tissues in PlantsVascular Tissue

Vessels that transport water and nutrients Plant “bloodstream”

Xylem – carries water Phloem – carries nutrients

Vascular Tissue - XylemTracheids – hollow plant

cells of the xylem with thick cell walls strengthened by lignin Lignin resists water and is a

major constituent in wood Openings in the cell walls of

tracheids allow water to pass from cell to cell and therefore be transported throughout the plant

Vessel Elements - hollow plants cells of xylem stacked end to end. Water passes from cell to cell

through slit-like openings on the ends of each cell

Vascular Tissue – PhloemSieve Tube Elements –

cells of the phloem that are arranged end to end and allow nutrients to flow throughout the plant in a watery stream

Companion Cells – cells of the phloem that the sieve tube cells and aid in the movement of nutrients

Specialized Tissues in PlantsGround Tissue

Produces and Stores food (sugars) Composes most of the edible portions of plants

Contributes to the physical support of the plantGround tissue is composed of three main types

of cells Parenchyma Collenchyma Sclerenchyma

Ground TissueParenchyma

Makes up the highest percentage of ground tissue Thin cell walls Large central vacuole Limited cytoplasm

Contain many chloroplasts in leaves and are the main sight of photosynthesis

Ground TissueCollenchyma

Chains of strong, flexible cell walls Provide support for plant organs

Sclerenchyma Extremely thick and rigid cells walls

Found on seed coats (strong!) Have been used to make rope from hemp

Plant Growth and MeristemsMeristems – regions of

specialized plant cells in which mitosis produces new cells ready for differentiationThe undifferentiated cells

produced are much like the stem cells of animals

Located in parts of plants that undergo rapid growth

Allow even the oldest trees to produce new leaves and new reproductive organs each year

Apical Meristem – located at the end (apex) of a root or stem.Leads to increase in root

or stem lengthOnce produced, the new

cells differentiate into new dermal, vascular, and ground tissue

Floral MeristemsProduce the tissues of

flowers Includes the plant’s

reproductive organs as well as the colorful petals that surround them