Plant Structure and Growth

Overview

Lifecycles– Annual, biennial, perennial

Basic Plant parts

Plant cell walls, simple tissue types

Plant growth:– Meristems– Primary Tissues– Primary growth – apical meristems– Secondary growth – lateral meristem – Secondary tissues

Flowering Plant Lifecycles

• Annual – germinates, flowers set seeds and dies in one growing season

• Biennial- germinates grows first season, storing up energy underground. Second spring plant use energy to quickly bloom (bolting) set seed and die.

• Perennial grows for several seasons until mature, Blooms and sets seed for years.

bolting

Basic Plant Parts

• Shoot system: photosynthesis, reproduction– Stems with nodes – Leaves - axilliary bud at base of each– Flowers and fruits (cones in gymnosperms)

• Root system ; Anchors plant; Storage organs; absorption of water and nutrients.– Roots, root hairs– Mycorrhizae– Nitrogen fixing bacteria

Angiosperm Diversity

Amborella trichopoda Water lily (Nymphaea “Rene Gerard”)

Star anise (Illicium floridanum)

BASAL ANGIOSPERMS

HYPOTHETICAL TREE OF FLOWERING PLANTS

MAGNOLIIDS

Am

bore

lla

Wat

er li

lies

Star

ani

sean

d re

lati

ves

Mag

nolii

ds

Mon

ocot

s

Eud

icot

s

Southern magnolia (Magnoliagrandiflora)

Orchid(Lemboglossumrossii)

MonocotCharacteristics

Embryos

Leafvenation

Stems

Root

Pollen

Flowers

Pollen grain withone opening

Root systemUsually fibrous(no main root)

Vascular tissuescattered

Veins usuallyparallel

One cotyledon Two cotyledons

Veins usuallynetlike

Vascular tissueusually arranged

in ring

Taproot (main root)usually present

Pollen grain withthree openings

Zucchini (CucurbitaPepo), female(left) and male flowers

Pea (Lathyrus nervosus,Lord Anson’s blue pea),a legume

Dog rose (Rosa canina), a wild rose

Pygmy date palm (Phoenix roebelenii)

Lily (Lilium“Enchant-ment”)

Barley (Hordeum vulgare), a grass

AntherStigma

Californiapoppy(Eschscholziacalifornica)

Pyrenean oak(Quercuspyrenaica)

Floral organsusually in

multiples of three

Floral organs usuallyin multiples of

four or fiveFilament Ovary

EudicotCharacteristics

MONOCOTS EUDICOTS

Fig. 35.2

Simple Plant Tissue Types• Tissues- cells with a common structure and

function and specialized connections. • Parenchyma- Soft, rounded cells with thin

primary cell walls, air spaces between cells– Many are Totipotent Cells- undifferentiated that

can still divide– Some are specialized: chlorenchyma, phloem

• Collenchyma- irregularly thicken primary cell wall, no air spaces. Elastic support.

• Sclerenchyma – rigid secondary cell wall. May have no cytoplasm left: Wood, Xylem, vessels, fibers, tracheids. Also seed coat.

Fig 35.11

Xylem

• Sclerenchyma• Dead at maturity• Hollow• Grows to size

first then makes secondary cell wall

• Tracheids• Vessel elements• Secondary xylem

is true wood.• Conducts water

from roots to leaf

Young Xylem

• We’ll go over different types in lab

• Transports sugar solution from source to sink.• Parenchyma-Living tissue, uses active

transport.• Sieve tube members and companions cells

Phloem

Plant Tissues comprise Organs

• Dermal tissues cover the plant– Epidermis, stomata, trichomes, bark

• Vascular Tissues transport materials– Xylem carries water– Phloem carries sugar solution

• Ground Tissues – metabolic functions, growth– Meristems, photosynthesis, storage

• Organs-groups of tissues forming a larger structure, with a common structure and function.

Fig 35.7

Plant cell wall structure• Adjoining cells held together by middle

lamella (polysaccharides of pectin)• Cells first make thin, flexible primary cell

walls.• Plant cells can still enlarge / divide with

primary cell wall.• Some cells lay down three rigid secondary

cell wall layers with ligin inside primary cell wall.

• Plasmodesmata connect cytoplasm between neighboring cells through cell walls.

Fig 6.28

Cell Elongation

• How cellulose microfibrils are laid down determine the direct of elongation.

• Elongation takes place when a cell only has primary cell wall.

• Once proper size and shape is attained, secondary cell wall material is added inside the primary cell wall.

Plane of Cell division

• Determines the cell shape

Plane of symmetry

Plant Growth• Indeterminate growth• Primary growth: cells derived from the apical

meristems (both root and shoot).– Makes the plant grow taller and roots deeper.– Makes leaves, flowers fruits

• Secondary Growth: cells derived from the lateral meristems.– Adds girth to plant– Vascular cambium makes secondary xylem

(wood) and secondary phloem.– Cork cambium adds to bark

• Meristems- localized areas of cell divisions– Plants grow in zones, not all over whole organism

Fig. 35.12

Fig. 35.17

Apical Meristem

• Divides cells that form primary meristem tissues– Protoderm – further divides to

make dermal layers– Procambium – divides to form

xylem and phloem, residual layer becomes vascular cambium

– Ground Meristem – forms pith and cortex

• Plants grow like building a brick wall- add bricks at top (primary growth), then add girth to sides (secondary growth).

Primary growth

• Herbaceous – no true wood• May have tough parts –

Collenchyma or Sclerenchyma.

• All cells derived from apical meristem

• Forms separate vascular bundles in stem.

• You fall madly in love with you’re a lab mate in 131 – and hand in hand you both carve you initials 4 feet off the ground on the Bishop Pine (Pinus muricata) in the turn-around by the LS building.

• The Bishop Pine grows 3 feet a year.• Two years later you return to DVC after

finishing up at UC Santa Cruz in Organismal Biology to visit you old favorite Biology instructor.

• How far off the ground are your initials then?

Secondary Growth• In Ferns, Gymnosperms and Eudicots, not in

monocots• Vascular cambium layer begins to form.

– Divides off more cells.– Cells to the inside become secondary xylem

(wood) Cells to outside become secondary phloem.

• Adds girth, pushing outer layer farther out.• Parenchyma in phloem rays fill-in space

until cork cambium starts making bark.

Fig. 35.20

Annular growth rings• In temperate or wet /dry seasonal zones

• In spring new growth use a lot of water, xylem cells grow very large (early wood).

• Under water stress late in the season xylem cells very narrow (late wood).

• Evidence of past climates, period of drought.

Monocot and Eu-dicot

• Monocots do not have secondary growth.– Palm trees, bamboo - not true wood!!

• We’ll compare anatomical variation between these groups in lab– Learn differences between monocot , dicot

anatomy of leaves, stems, roots.