LEC 09

FIELD BOTANY – Lecture 09Dr. Donald P. Althoff

GrassesPart I

Seed-bearing

Flowers

gymnosperms DICOTS

MAGNOLIOPHYTA

Kingdom Division Class

ORDERS-FAMILIES-

Plantae

Magnoliophyta (Anthrophyta)

Liliopsida-moncots

Cyperales

1 2

Cyperaceae Juncaceae

3

Juncales

grasses sedges rushes

Grasses ______ diverse• Grasses: 600 genera

between ______________ species

• Sedges: 70 genera ~4,000 species

• Rushes: 8 genera ~400 species

Grasslands of the world

EQUATOR

Tropic ofCancer

Tropic ofCapricorn

Historically, prairie covered 400,000 mi2

of North America

____

C3 plants—all of carbon fixation andphotosynthesis happens in _______________just on the surface of the leaf.

C3 plants include most temperate plants(except many grasses)—more than _____ of all earth’s plants.

____

C4 plants—carbon fixation andphotosynthesis split between the_____________________________________.

Warm season grasses _________ plant group in the short, mixed, and tallgrass prairies

Stomata, CO2, & Fixation

• C3 plants--uses the enzyme rubisco to fix carbon dioxide to RuBP…after fixation is PGAL, a _________________

• C4 plants--do not directly use Calvin cycle and produce immediately a _________________

• ____ plants--uses PEP carboxsylase to fix CO2 at night (example: cacti)

CAM Plants• ____________________________

• Fixation of CO2 at night, stored in the form of malate in large vacuoles in the mesophyll cells is available the next day….

• Stomata remained ______ during the day!!!

H2O

O2

CO2

Calvincycle

3 carbon molecule

Calvincycle

4 carbon molecule before Calvin cycle

4 carbon molecule before Calvin cycle that is

“banked” at night

Calvin cycle completed during the day

Night

Day

stoma

____________cells

Leaf Structure for ___ and ___ plants

Leaf Structure

C3bundle sheath cells lack chloroplasts

C4bundle sheath cells __________________

CAM _____________ in mesophyll cells

Enzyme utilized

C3rubisco

C4pepco

CAM pepco

Optimum Temperature

C3 15 – 25 C __________

C4 30 – 40 C __________

CAM 35 C __________

05

10152025303540

3241505968778695104

oC oF

C3

Coolseason

C4

Warmseason

CAM

15-25oC60-77oF

30-40oC86-100oF

35oC

*Approximate optimum (dark shades) and range (light shades)when C3, C4, and CAM plants start to

grow/conduct photosynthesis efficiently

Growing season

What do we mean “cool” vs. “warm” season?• Peak period of plant productivity…and flowering

cool coolwarm

J F M A M J J A S O N D

F FF F FFFFF F

Productivity rate(tons/hectare/year)

C3 22 +/- 0.3

C4 39 +/- 17

CAM low & variable

C3 Plants - examples

• Peas• Spinach• Broccoli

• Kentucky bluegrass

• Tall fescue

C4 Plants - examples

• Corn• Soybeans• Tomatoes

• Indiangrass• Buffalo grass• Big bluestem• Blue grama

Adaptation to the Environment• These 3 different “ways” (i.e., C3, C4, and CAM)to accomplish

photosynthesis illustrate how organisms _________________ to their environment. Each has its advantages and disadvantages

• C4 – likely _______ in high light intensity, high temperature, and limited rainfall environments.

• C3 –likely _______ in lower light intensity, moderate temperature, and more abundant rainfall environments

• CAM – likely _______ in extremely arid environments (ferns and cone-bearing plants exhibit this process in

addition to many flowering plants like some orchids and lily species)

Characteristics to note for GRASSES

• Inflorescences• Spike vs. spikelets• Ligule “design” (see _____________ set)• Floret composition (palea, lemma, awns)• Seed heads (panicle vs. spike)• Fruits (are grains …compared to rushes and

sedges)

_______________ = arrangement of flowers on the stem

Spike vs. ________

Seed heads:_______ vs. _______

SPIKELET

FLORET

seed

palea

lemmaawn

FLORET

SPIKELET

awn

lemma

palea