plant biology lecture 10- root structure and development

what role do roots play

• Anchor plant to soil

• Absorb water

• Important for storage

• Important for conducting (moving) water up plant as plant grows

• Provide structural support

where does the primary root develop from

the radicle (embryonic root)

what is the root cap

• made of modified parenchyma cells

• protects root apical meristem

• produces mucilage that lubes root to easily pass through soil

what are root hairs

epidermal cells that form outgrowths to increase surface area for absorbing water + material

what is this area

quiescent centre/promeristem

• cells in this area divide slowly, and are surrounded by cells that divide actively

what are the primary meristematic tissues in the dicot root

• Protoderm (epidermal cells)

• Ground meristem (ground tissue)

• Procambium (vascular tissue)

dicot roots have no pith

what happens when cell in the root grow

they elongate and push the tip of the root through the soil

cells eventually mature

where are root hairs produced

only in zone of cell maturation, or else they’ll get constantly shave off in zone of elongation/division

what is the endodermis

single ring of cells surrounding vascular tissue

• Innermost cell layer of the cortex

• Everything inside endodermis is the stele

• outside of pericycle

what is the difference in epidermis in root vs stem

stem: epidermis plays protective role and produces cuticle to eliminate water loss

root: epidermis is highly permeable to water + minerals can move across epidermal cells to vascular system

what are the 2 kinds of spaces in plant tissue

apoplast: cell walls and lots of intercellular space for substances to diffuse across walls

symplast: cytoplasm of cells and interconnections via plasmodesmata

how does water enter the root

water enters cortex tissue vis root hairs and goes through both symplast and apoplast.

once inside cortex, waters moves across space to xylem

Plant will force water into the symplast through the endodermis to control what enters the xylem and when

what is the purpose of casparian strips

prevents water from diffusing through intercellular spaces, and instead diverted into endodermis cells

• Allows plant to better regular substances

what stage of growth is this root

end of primary growth

what stage of growth is this root

start of secondary growth

what happens when plants start to undergo secondary growth

• pericycle divides and becomes multiple cell layers

• some pericycle becomes meristematic and creates ring of vascular cambium

what are the 3 roles of the pericycle

1. contributes cells to the formation of the vascular cambium

2. produces periderm

3. becomes the new outer layer of tissue for protection