Anatomy, Morphology, & Growth of Angiosperms – Ch. 5-8

Two plant groups: monocots & dicots

Structure Reflects Function http://www.fugu-sg.org/~elia/cambodia/templesfacesweb/pages/A3_Embracing_Roots.htm

Structure of a plant determined by: 1. Genetics 2. Environment – two time scales: 1. Long-term: 2. Short-term: plasticity = wide range of phenotypes for each genotype. Allows plants to adjust to changing environment (ex. Shorter plant in dry year so that it can still reproduce)

Cells Tissues Muscle cell Muscle tissue Organs Heart Systems Circulatory system

Three organs: Roots, stems, leaves

1.

Roots

– • • Store food (carbos from photosynthesis) to be used for flowering & fruiting Covered with root hairs – increased surface area for absorption

Fig 35.2

Prop roots Buttress roots Sweet Potato – storage root Aerial strangler roots

Modified Roots – Fig 35.4

Pneumatophores

• • • • 2. Stems/shoots Support, transport Some photosynthesis Two types of shoots 1. Vegetative – 2. Reproductive – Two parts of stem: 1. Node – 2. Internode – stem segments between nodes

Two types of buds 1.

2.

Terminal bud – contains a shoot apical meristem; shoot growth is concentrated here Axillary buds – Apical dominance = the presence of an apical bud inhibits the growth of axillary buds. -remove or depress apical bud, axillary buds begin to grow.

• Stolons – Modified Shoots (stems): Asexual, vegetative propagation • Rhizomes – • Bulbs – swollen underground shoots • Tubers – swollen rhizomes Stores food for later growth

Fig 35.5

3. Leaves – main photosynthesis organs http://www.knotweed.co.uk/japknot_Info.htm

Modified leaves • Compound, doubly compound – why??

Tendrils Spines Fig 35.7 – Modified leaves Succulents

Leaf types: Simple leaf = Compound leaf = divided into distinct units called leaflets

Four types of leaf arrangement : 1. Acaulescent – 2. Alternate – 3. Opposite – leaves borne across from each other at the same node 4. Whorled – 3 or more leaves arising from the same node.

Three main tissues: Dermal, Vascular, Ground Fig 35.8

1. Dermal tissue or epidermis

• • Root hairs are specialized epidermal extensions Secretes waxy cuticle of the leaf

2. Ground Tissue • fills the space between dermal and vascular tissue systems.

• Diverse functions: In dicots: pith cortex

3. Vascular Tissue • function in transport between roots & shoots, and structural support of plant – Xylem: – Phloem: Food transported to roots & non photosynthetic parts such as the flowers

The Plant Cell Fig 7.8

5 Differentiated Plant Cell Categories 1. Parenchyma 2. Collenchyma 3. Schlerenchyma 4. Water-conducting cells of the xylem 5. Sugar-conducting cells of the phloem

1. Parenchyma • thin and flexible cell walls

2. Collenchyma • Usually grouped in strands to support young parts of plants without restraining growth • Flexible, elongate with growing shoots

3. Schlerenchyma • May be dead at functional maturity – ??? • cell walls left behind as skeleton

4. Water conducting cells of the xylem: • 2 types: tracheids & vessel elements

Tracheids

• Water flows from cell to cell (laterally) through pits in cell wall • Support function

Vessel Elements • End walls are perforated for free flow of water • More efficient as water conductors than tracheids

Fig 35.9

5. Sugar-conducting cells of the phloem Sieve-tube members: • Lack a nucleus, ribosomes, vacuole • Cells separated by perforated sieve plates – allow sugar movement

Fig 35.9

Growth & Development

http://www.cneccc.edu.hk/subjects/bio/album/Chapter20/PLANT_GROWTH.html

• Development =

Three processes of development: 1.

Growth = 2.

3.

Cellular differentiation = generation of different cell types Morphogenesis – creation of body form & organization.

1. Growth

• Cell division no expansion

Growth

• = due to water uptake in the vacuole

Fig 35.24

Cell division • Occurs in only in meristems!

Meristems • = • Two types of meristems: 1. Apical meristem – 2. Lateral meristems – extend lengthwise along the axis of the stem & roots. Responsible for growth in

girth

in older parts of the plant (called

secondary growth

). Exist only in perennials

Fig 35.10

Primary Growth of Roots

• Root cap – layer of cells that protect the RAM as it pushes through the soil

Fig 35.12

Arrangement of Primary Tissues in Roots 1.

Epidermis – 2.

Stele – 3.

• Ground tissue – mostly parenchyma cells of the

cortex

– area between the stele & epidermis; stores food & takes up minerals.

Endodermis – single cell layer between cortex & stele. Selective barrier for uptake of soil solution contents into vascular system.

Eudicot/Gymnosperm root cross section Epidermis Endodermis Cortex Stele Fig 35.13

xylem phloem

Primary Growth of Shoots

• Bud = cluster of leaf primordia created by meristem. No internodes • Lateral branches arise from axillary buds

Fig 35.15

Primary tissue arrangement of stems – Ground tissue = pith & cortex

Eudicot/Gymnosperm stem cross section pith phloem cortex xylem epidermis Fig 35.16

Schlerenchyma cells

Tissue arrangement of leaves • 3 parts: 1. Upper & lower epidermis – tightly interlocked cells, secrete waxy cuticle. Contains stomata flanked by guard cells 2. Vascular tissue – 3. Mesophyll – ground tissue between upper & lower epidermis

Fig 35.17

Secondary Growth

• Two lateral meristems: 1. Vascular cambium – produces secondary xylem (=

wood

) & phloem 2. Cork cambium – replaces the epidermis with cork: tough, thick cover for stems, roots.

Secondary growth of stems •

Vascular cambium

– layer of cells between primary xylem & primary phloem. Puts on successive layers of secondary phloem to outside & secondary xylem to inside =====> stem widens • Wood = accumulation of secondary xylem. Dead at maturity, contains lignin

•

“bark”

=

Cork cambium

• Cork continually sloughs off

Fig 35.18

Fig 35.20

Three types of life cycles: 1.

Annual – 2.

3.

Biennial – complete life cycle in two years (first year = vegetative, second year = reproductive). Some need a cold winter period to initiate flowering from vegetative state. Ex. carrots Perennial – live year after year, do not die after reproduction. Examples: trees, shrubs, some grasses. Causes of death = fire, disease