Plant support and growth: Secondary Growth

What is secondary growth

it is woody growth, increased girth rather than length

Not all plants go through secondary growth

Annual plants, biennial plants, herbaceous perennials, tree ferns, and palms

Plants that do have secondary growth

all the seed plants except monocots

what is the function of Xylem

it is the main conducting tissue for water and minerals absorbed by roots

what is xylem composed of

parenchyma cells, fibers, vessels, tracheids, and ray cells

what are vessles

long tubes composed of vessel elements, which are open at each end

what are tracheids

tapered cells, not open at the end. often have pits in between them

Gymnosperm xylem has tracheids only

Anthophyte xylem has both tracheids and vessel elements

What is Phloem

it conducts photosynthates

what are photosynthates

dissolved foods, sugars, produce of photosynthesis

what are phloem composed of

sieve tube members and companion cells

what are sieve tube members

cylindrical cells, laid end-to-end

what is the epidermis

the outermost cell layer on all young plant organs, usually one cell thick, and forms a protective layer called the cuticle

what is the Axial system

vertically running cells (big vertical bunch of straws

what is the Radial system

Horizontally running cells (there are a few straws stuck horizontally through the big bunch)

what are the two secondary meristems

vascular cambium and cork cambium

What are rays

provide horizontal transport and storage in wood,

Phloem rays are triangular

what is the vascular cambium

the layer between the axial/radial systems and ?

what are the three parts of the Periderm

cork cambium, cork, phelloderm

what is the outer bark

all tissues outside of the innermost cork cambium

what is the inner bark

it is what is between the innermost cork cambium and vascular cambium

what is a result of continued secondary growth?

bark textures may seem to be flaking/peeling off

What are the characteristics of Heartwood

• darker

• non-conducting

• no food reserve, all dead cells

what are the characteristics of Sapwood?

• lighter

• conducting

what are annual rings?

visible rings that mark the end of a year’s growth in species in seasonal environments