Plant Growth

Growth in Animals Animals grow throughout the whole

organism many regions & tissues at different rates

Growth in Plants Specific regions of growth: _____________

stem cells: perpetually embryonic tissue regenerate new cells

___________________ growth in length primary growth

___________________ growth in length primary growth

___________________ growth in girth (width) secondary growth

Apical meristems

shoot shoot

Root structure & growth

protecting the meristem

Shoot growth

Young leafprimordium

Apical meristem

Older leafprimordium

Lateral budprimordium

Vascular tissue

Apical bud & primary growth of shoot region of stem growth __________________

“waiting in the wings”

protecting the meristem

Woody plants grow in height from tip primary growth ______________________

Woody plants grow in diameter from sides secondary growth ______________________

_____________________ makes 2° phloem & 2° xylem

_____________________ makes bark

Growth in woody plants

Primaryphloem Primary

xylemSecondaryphloem

Secondaryxylem

Annualgrowthlayers

Lateralmeristems

Primaryxylem

Primaryphloem

Bark

Epidermis

Secondary growth

Secondary growth growth in diameter

thickens & strengthens older part of tree

____________________________________ growing ring around tree

____________________________________ growing ring around tree

Vascular cambium

last year’s xylemearly

late

phloem

bark

Phloem produced to the outsideXylem produced to the inside

corkcambium

vascularcambium

Why are early & late growth

different?

phloem

Woody stem cork cambium

vascular cambium

xylem

earlylate

phloem bark

How old is this tree?

12

3

Tree trunk anatomy

tree girdling

What does girdling do to a tree?

Aaaargh!Murderer!Arborcide!

Tree trunk anatomy

tree girdling

What does girdling do to a tree?

Aaaargh!Murderer!Arborcide!

Where will the carving be in 50 years?

Plant hormones __________________ __________________ __________________ __________________ and more…

Auxin (IAA) Effects

controls cell division & differentiation

__________________ growth towards light asymmetrical distribution of auxin cells on darker side elongate faster

than cells on brighter side __________________

Gibberellins Family of hormones

over 100 different gibberellins identified

Effects stem elongation ____________________ ____________________

plump grapes in grocery stores have been treated with gibberellin hormones while on the vine

Abscisic acid (ABA) Effects

____________________ ____________________

high concentrations of abscisic acid germination only after ABA is inactivated or

leeched out

survival value: seed will germinate only under optimal conditions

light, temperature, moisture

Ethylene Hormone gas released by plant cells Effects

____________________ ____________________

like in Autumn apoptosis

One bad apple spoils the

whole bunch…

Fruit ripening Adaptation

hard, tart fruit protects developing seed from herbivores

ripe, sweet, soft fruit attracts animals to disperse seed

Mechanism triggers ripening process

breakdown of cell wall softening

conversion of starch to sugar sweetening

positive feedback system ethylene triggers ripening ripening stimulates more ethylene production

clusters of fruit ripen together

Apoptosis in plantsWhat is the evolutionary advantage of loss of leaves in autumn?

Many events in plants involve apoptosis response to hormones

ethylene auxin

death of annual plant after flowering senescence

differentiation of xylem vessels loss of cytoplasm

shedding of autumn leaves

2007-2008

Don’t take this lying down…

Ask Questions!!

Apical meristems

shoot shoot

Root structure & growth

protecting the meristem

Shoot growth

Young leafprimordium

Apical meristem

Older leafprimordium

Lateral budprimordium

Vascular tissue

Apical bud & primary growth of shoot region of stem growth __________________

“waiting in the wings”

protecting the meristem

Woody plants grow in height from tip primary growth ______________________

Woody plants grow in diameter from sides secondary growth ______________________

_____________________ makes 2° phloem & 2° xylem

_____________________ makes bark

Growth in woody plants

Primaryphloem Primary

xylemSecondaryphloem

Secondaryxylem

Annualgrowthlayers

Lateralmeristems

Primaryxylem

Primaryphloem

Bark

Epidermis

Vascular cambium

last year’s xylemearly

late

phloem

bark

Phloem produced to the outsideXylem produced to the inside

corkcambium

vascularcambium

Why are early & late growth

different?

phloem

Woody stem cork cambium

vascular cambium

xylem

earlylate

phloem bark

How old is this tree?

12

3

Basic plant anatomy 1

Leaves Function of leaves

photosynthesis energy production CHO production

gas exchange transpiration simple vs. compound

Parenchyma Parenchyma cells are unspecialized, thin, flexible &

carry out many metabolic functions all other cell types in plants develop from parenchyma

Collenchyma Collenchyma cells have thicker primary walls &

provide support help support without restraining growth remain alive in maturity

the strings in celery stalksare collenchyma

Sclerenchyma Thick, rigid cell wall

lignin (wood) cannot elongate mostly dead at maturity

Cells for support xylem vessels xylem tracheids fibers

rope fibers sclereids

nutshells seed coats grittiness in pears

tracheids

vessel elements Vascular tissue

Aaaah…Structure–Function

again!

vessel element

dead cells

Xylem move water & minerals up from roots dead cells at functional maturity

only cell walls remain need empty pipes to efficiently move H2O transpirational pull

Phloem: food-conducting cells carry sugars & nutrients throughout plant

sieve tube

companion cell

living cells

plasmodesmata sieve plate

Phloem: food-conducting cells sieve tube elements & companion cells

Vascular tissue in stems

dicottrees & shrubs

monocotgrasses & lilies

collect annual rings

Vascular tissue in roots: dicot

xylemphloem

xylem

phloem

Vascular tissue in roots: monocot

Anther

FilamentStamen

StigmaStyleOvary

Carpel

Sepal

Petal

Ovule

sepalspetals

Flower Modified shoot with 4 rings

of modified leaves sepals petals stamens

male carpel

female stamens

carpel

adaptations through mutations

What is a Cotyledon? Cotyledon: seed leaf in the embryo of an

angiosperm that hold food for the developing plant May form a leaf after germination