Plant Tissues and Meristems
All derived from
meristematic
tissue
• Meristematic
tissue is
composed of
aggregates of
small cells,
which have
the ability to
divide.
When the cells divides:
1 stem cell (initials)/1 differentiated cell
(derivatives)
Continually renewed
Most plants have 3 basic types of
tissues:
• Dermal
• Ground
• Vascular
Outer covering which protects
against physical agents and
organisms. It also prevents
water loss
Thin walled cells
Functions: storage,
photosynthesis, support,
secretion
Xylem/phloem: carryout long
distance conduction (water,
minerals, nutrients), provide
support
Plant Growth
Plants
Continual pattern of growth
Animals/leaves
Growth ceases at a point
Death:
Annuals (die yearly)
Biennials (2yr cycle)
Perennials (die due to infection,
environmental factors)
Apical Meristems- often are differentiated based on location within the plant.
1⁰ meristem
-produces new
tissues and
causes primary
growth
through
mitosis and
cell division
Grow tall to increase exposure to
light, CO2
Results in:
Herbaceous, nonwoody plants
Extends into soil
2⁰ meristem:
increase thickness
of stem/root
Results in:
Woody plants
Produces
cork cells
of outer
bark
Produces 2⁰ vascular tissue
- lies between xylem and
phloem
Plant Hormones
Means of communication within plant
Affect development and growth:
Environmental stimulus (day length/water)
Receptor types (detection of factors)
Genetic makeup
Hormones
Process of Hormone signaling
Specific cells have specific receptors
Receive environmental stimulus
Protein receptor activated
Initiates metabolic pathway
Plant hormones differ from
animal hormones.
-Plant hormones have varying
effects depending on the
receptor's location.
-Animals ususally have a
specialized gland to produce
the hormone.
-Plant hormones may be
produced throughout the
plant.
Produces hormone (produced throughout plant)
Travel via phloem
Target cell  affects specific area of plant
Auxin and Phototropism
Tropisms: growth/movement to directional external
stimuli
Positive – towards
Negative - away
Phototropism: response to light
Stems (+)
Roots (-)
Hormone
Increases flexibility of cell
walls in young plants
Auxin found in embryo of seed,
the meristems of apical buds and
young leaves.
Redistributed
to shaded side
Auxin only works on plants cells that have auxin receptors.
-increase plants flexibility, allowing cells to elongate during growth
Creates
curvature
towards light
Auxin repositions
closer to light.
Auxin and Phototropism
1. Auxin produced in all cells in stem on light side (auxin efflux)
2. Auxin moves by efflux pump action into the cell on the “dark” side of the cell.
3. Auxin and receptor form complex which activates H+ pump
4. The proton pumps H+ into cell wall
5. Causes pH drop; resulting in H-bonds between cellulose fibers – breaking cell wall
6. This results in the elongation of the cells on the side away from the light.
Auxin involved with:
– Stimulation of cell division in
meristematic tissue
– Xylem/phloem differentiation
– Development of lateral roots
– Suppress lateral bud growth
when found in apical bud
– Stimulate growth of flower parts
– Fruit production without
pollination
Changes in gene
expression
Micropropogation
-is used to stimulate
existing plant material
to produce large
numbers of progeny
(offspring).
Culture cells from shoot apex
Nutrient agar with growth
hormones
Uses:
• Rare/endangered plants
maintained
• Develop virus-free strains
• Alter genome to create
beneficial plants
Problems:
• Extremely expensive
• Difficult to maintain
pathogen free environment