week 5 (roots, shoots, and primary growth)

taproot system

type of root system distinguished by a main vertically growing root and branching lateral roots

fibrous root system

type of root system distinguished by many equally prominent roots emerging from the stem

aerial roots

roots modified to be produced by above-ground structures

storage roots

roots modified to have increased parenchyma tissue to store sugars

mychorriza

root symbiosis with fungi for protection and increased water and nutrient uptake

AM (mychorrizas)

endomychorrizas (penetrating cell walls) present in most vascular plants

ECM (mychorrizas)

ectomychorrizas (surrounding cells) present in some tree and shrub species (generally in colder climates)

root nodules

root symbiosis with bacteria that creates large nodules and allows for nitrogen fixing

node

the point at which a leaf attaches to the stem

bud primordium

the point at which a bud (and subsequently a lateral shoot) develops

leaf primordium

the point at which a node (and subsequently a leaf) develops

internode

the stem space below a node/leaf, or above a bud/lateral shoot

promeristem (“central zone”)

the section of apical meristem that produces the primary meristems

stele

the arrangement of vascular tissue in a root/shoot

protostele

a central cylinder-like arrangement of vascular tissue found in all roots and some shoots of vascular plants

eustele

arrangement of vascular tissue that has discrete vascular bundles surrounding pith

open vascular bundles

vascular bundles that retain their procambial cells and ultimately will be used for secondary growth

closed vascular bundles

vascular bundles that completely develop into mature primary tissue, seeing no further growth

primary growth

plant growth in the extending or vertical direction

meristem

an embryonic region of tissue that is capable of continuously dividing and producing new cells of many kinds

apical meristem

meristem found at the tip of either the root or shoot

primary meristems

partially differentiated meristems produced by the apical meristem that can be meristematic for a long time

meristematic

capable of continuously creating new cells of many kinds

ground meristem

primary meristem that produces ground tissues

procambium

primary meristem that produces vascular tissue

protoderm

primary meristem that produces dermal tissue

rootcap

mass of parenchyma cells that protect a root’s apical meristem and guides direction of root growth

region of maturation

root growth region in which cells mature into primary tissues and root hairs form

region of elongation

root growth region in which cells elongate to increase root length

root hairs

short-lived extensions of the epidermis (specifically each a trichome) to increase surface area for water and mineral uptake

cortex

ground tissue region between the vascular bundle and epidermis, which stores materials and has intercellular space for the aeration of cells

endodermis

innermost section of the cortex which is tightly packed, lacking intercellular space and having Casparian strips

Casparian strips

hydrophobic sections of cells in the endodermis and exodermis which force water to enter cells, increasing water efficiency

exodermis

outermost section of the cortex immediately before the epidermis, characterized by Casparian strips

pericycle

the layer surrounding the vascular tissues which assists with secondary growth

phytomere

the structural order of shoots: bud, internode, node