Meristems of primary growth

outcomes of primary growth

adds length

produces new organs

establishes patters of cell differentiation

apical meristem contains:

promeristem

primary meristems

promeristem in seed free plants

single apical cell

promeristem in roots (non seed free)

group of apical initials

quiescent center

inactive meristematic calls which divide rarely and are surrounded by the promeristem

columella

vertical files of cells in the root cap used for gravity sensing

open type meristem

root meristem where primary meristems are only distinguishable a ways away from the promeristem

closed type meristem

root meristem where primary meristems are recognizable immediately adjacent to the promeristem

trichoblast

specialized epidermis cells for producing root hairs

Equisetum root w/ apical cell and trichoblasts

name the regions

black bar: permanent initials

1: central cylinder mother cells

2: cortical mother cells

3: columellar mother cells

4: columella

5: root cap

6: central cylinder

7: ground meristem and protoderm

Allium root tip; open type

Zea root tip; closed type-Zea type

Raphanus root tip; closed type-Raphanus type

characteristic T/Y divisions

Difference between Zea and Raphanus type roots

Zea: 3 apical tiers which give rise to:

• root cap

• ground meristem and protoderm

• central cylinder

Raphanus: 3 apical tiers which give rise to:

• root cap and protoderm

• ground meristem

  • central cylinder

central cell

cell representing quiescent center in Zea type roots, present between the top 2 tiers

statocytes

cells in root cap with amyloplasts (acting as statoliths) for gravity sensing

Pistia root tip; closed type-Raphanus type

lateral roots with root caps and primary meristems developing

shoot promeristem characteristics

outer layer enclosing a central region

in gymnosperms:

• surface meristem

• central mother cells

• sometimes transition zone

in angiosperms:

• tunica

• corpus

• sometimes transition zone

from top view:

• central zone

• peripheral zone

rib meristem

in shoots, central meristem which gives rise to pith

flank meristem

in shoots, peripheral meristem which gives rise to ground meristem, procambium, sometimes outer edge of rib meristem

Equisetum shoot tip with apical cell

Pinus shoot tip

• surface meristem

• central mother cells

• rib meristem surrounded by peripheral zone (flank meristem)

• sometimes transitional zone

Zea shoot tip

• 1 tunica layer

Vinca shoot tip

• 5 tunica layers

• transition zone under corpus

Elodea shoot tip

• 2 tunica layers

Coleus shoot tip

• 5 layer tunica

Equisetum intercalary meristem

• base of each internode

rhexigenous protoxylem lacunae

holes in internodes containing secondary wall thickenings. Produced by tearing of stretched protoxylem tracheids from elongation of internodes