Transcript The Geography of Grass

The Geography
of Grass
Lecture 3
Justin Borevitz
Land Institute
Wind Powered Desalinization
• Perth Seawater Desalination Plant,
Seawater Reverse Osmosis (SWRO),
Kwinana, Australia
• "Supplying 17% of Perth’s
needs, the plant will be the
largest single contributor to
the area’s integrated water
supply scheme
•Electricity for the
desalination plant comes
from the new 80MW Emu
Downs Wind Farm, which
consists of 48 wind turbines
located 30km east
Grass Physiology
• Water loss, leaves? Stems, stomata,
meristem
• http://www.missouriplants.com/Grasses/
Grass Diversity
•
•
•
•
•
•
•
•
650-785 genera
10,000 species
USA: 170 genera and 1400 species
Grass family has the most warm-season plants
Grasses can be warm- or cool-season plants, so
grasses are the most widely adapted plants
Grasses are annuals or perennial
There are no biennial grasses
Grasses are vital to life on earth.
Grass can be
• small – annual bluegrass
• large – bamboo
`
members of Poaceae plant family
Monocotyledonous
mostly herbaceous (non woody)
jointed culms, sheathed leaves
parallel veination
•
•
•
Role of stomata
Plants open stomata
(microscopic pores in their
leaves) to gain CO2, and in
the process they lose
water.
Plants must regulate this
loss by regulating stomatal
conductance from their
leaves.
It's a trade-off; to get more
carbon, they must 'spend'
water.
Development of the Root System
•
•
•
•
•
Radicle (primary root) appears at germination
Seminal roots develop from the seed
Radicles and seminal roots are short-lived
Adventitious roots develop from coleoptile node
Additional roots can form at nodes
Rizhomes
• Stem or root?
Rhizomes
•
•
•
•
•
•
•
•
Quackgrass, johnsongrass, Kentucky bluegrass,
switchgrass, reed canarygrass are highly
rhizomonous
Rhizomes start from an axillary bud
Grow laterally underground
Rhizomes are actually a series of buds and can
root at each node
Rhizomes contain stored food
Rhizomonous species create thick sods
Thick sods purify the water by acting as a filter
Tall fescue has short rhizomes – looks like a
bunchgrass
•
•
•
•
•
•
•
Stolons
Lateral stems located above
ground
Have a creeping nature
Form from axillary buds
Have nodes and internodes
Each node produces a new
bud
Stoloniferous species form
sods
Bermudagrass and
buffalograss are highly
stoloniferous
•
•
•
Stems
Thick, lower internodes form a crown in perennial
grasses
The crown stores carbohydrates and proteins
Some species, like timothy, develop a corm
Elongation: once or every time?
Most tillers go through the elongation process to
develop a reproductive culm only once.
Some species have tillers that essentially elevate
the shoot apex at every regrowth:
• timothy
• reed canarygrass
• smooth bromegrass
•
•
These grasses must be managed properly or
they will disappear from the stand.
Many of these grass do have active tillering.
Protecting meristems
• Plants need active shoot apices and other
meristems to provide new growth or regrowth after harvest.
• Critical management period for grasses
occurs during reproductive growth (after
transition) when internode elongation
elevates the shoot apex to a vulnerable
height.
• Timothy, smooth bromegrass, and prairie
grass are examples of grasses susceptible
to mismanagement (untimely defoliation).
• Defer grazing or clipping until crown buds
are ready for growth (boot stage or later).
Grazing implications
• Grasses in vegetative stages,
producing lots of leaves are the best
for grazing
• Elongation indicates the shoot apex
(growing point) is rising and may be
vulnerable
• Grasses in reproductive stage have
more culm which is not as palatable
or nutritious
• Hay is best cut before the
inflorescence appears above the
flag leaf (boot stage) because of the
balance between yield and quality
Photorespiration
• RUBISCO binds O2 instead of CO2
• Photorespiration occurs in hot
climates and when there is high
oxygen levels and low levels of carbon
dioxide
• Plants avoid photorespiration by C4
photosynthesis
• C4 plants concentrate CO2 in special
cells
Matt Ritter CalPoly San Luis Obispo
C4
Plant
“Kranz
Anatomy”
Vascular Bundle surrounded by Bundle Sheath Cells
C4 Carbon Fixation
C4 cells have both the Calvin
Cycle and the C4 mechanism
C4 fixation occurs in mesophyll
cells and the Calvin Cycle occurs
in the bundle sheath cells
PEP carboxylase has no
C4 plants: sugarcane, millet,
affinity for O2
corn, sorghum, bougainvillea
Approaches to Photosynthesis
Radiation effects
• Photosynthesis increases in
a nearly linear manner with
irradiance to near 50% full
sun for C3 plants.
• C4 plant photosynthesis
continues to increase with
increased radiation due to
PEPCase keeping CO2 levels
low creating a larger gradient.
• At full sun, C4 species
photosynthesis rates may be
double that of C3 species.
• Thus, C3 grasses are
more digestible and
higher in protein!!!
David B. & Kimberly J. Hannaway OSU ForagesTextChapter5.ppt
• C3 grow better in cool seasons Examples:
– Legumes: alfalfa, red clover, white clover, crimson
clover, birdsfoot trefoil
– Grasses: tall fescue, orchard grass, ryegrasses,
timothy, smooth bromegrass, Kentucky bluegrass
– Brassicas: turnips,rape, kale, swedes
– Cereal grains: oats, wheat, triticale, rye
– all dicotyledonous weed species
• C4 higher Water Use Efficiency
–
–
–
–
–
–
corn
big bluestem
switchgrass
bermudagrass
sorghum sudangrass
summer annual grass weeds are typically C4
Local Adaptation
• Flowering time
• Moisture, water use efficiency.
• Clinal variation North to South, East to
West
• John McKay’s talk
Nature Genetics 38, 711 - 715 (2006)
Published online: 28 May 2006; | doi:10.1038/ng1818
The PHYTOCHROME C photoreceptor gene mediates natural variation in flowering and growth responses of Arabidopsis
thaliana
Sureshkumar Balasubramanian, Sridevi Sureshkumar, Mitesh Agrawal, Todd P Michael, Carrie Wessinger, Julin N Maloof, Richard Clark, Norman Warthmann, Joanne Chory & Detlef Weigel
Figure 4. Latitudinal cline of PHYC alleles.
(a) Proportion of Ler-type (black) and Col-0–type (white) PHYC alleles at different
latitudes among apparently FRI functional strains. The absolute numbers for each of
the classes is given on top of the histograms. (b) Distribution of P values of a
nominal logistic regression model with latitude as a factor and genotypes as
response. Allele information of 65 random SNP markers with similar allele frequency
as that of PHYC was available in a set of 163 strains. This information was used as a
response. Note genome-wide skew towards small P values. (c) Distribution of P
values for interaction of a given random marker with FRI in an interaction model with
latitude as the response and FRI and marker genotypes as factors with interaction.
Flowering
• When stimulated to flower…
• Shoot apex (terminal meristem, apical
meristem, primordial meristem) stops
producing leaves
• Shoot apex focus on developing an
inflorescence
• Not all tillers become reproductive at
any given season
• Once a tiller produces an
inflorescence, the tiller and roots die
Before it can grow crops land has to be ploughed. Until
the arrival of the homesteaders in the 1860s however,
the soil on the Plains had never been cut by a plough.
The Prairie grass that covered the Plains had thick
deep roots of up to 10cm. These roots grew in dense
tangled clumps that were difficult to cut. The first
homesteaders that arrived on the Plains brought their
iron ploughs from the Eastern USA. These could cut
through the previously ploughed soft soils there, but
they broke when used on the Great Plains.
Go back
to problems
What was
the solution?
To cut through the soil of the Plains the homesteaders
needed a much stronger plough. In 1830 an Illinois
blacksmith named John Deere had made a steel plough
for one of his neighbours, in order to solve the same
problem the homesteaders faced. This ‘Sodbuster’
plough was soon adopted by the homesteaders and
provided them with the means to plough their land.
Steel is a much stronger metal than iron, so the plough
did not break.
To overcome the lack of timber to build their houses the
Homesteaders used sods of earth cut from the Plains as bricks.
They built their houses out of this earth and called them sod
houses.
Many sod houses were huge affairs, with many rooms, but they all
suffered from the same problems. They were dirty, drafty and
leaked whenever it rained. The walls and floor were infested with
lice, which crawled over the Homesteaders as they slept. Mud fell
off the ceiling into the Homesteaders’ cooking pots, and germs were
rife. Despite this, many Homesteaders were proud of their first
‘soddy’ and often lived in them for decades.
Prairie Weather
• Grasses ride the Prairie Climate
Rollercoaster
• 80C differential! -40C to +40C
– Day changes of >15C, not correlated with day
night, like the desert.
• Semi arid, cannot sustain forestland
– As Europeans were used to
– But not an obvious desert
Jet Stream
• Prevailing Winds from the West
– Desert, southwest,
– Pacific, northwest,
– Artic North (Winter), or gulf South (summer)
• Chicago area, gulf meats Pacific!
Thunderstorms
• Wind, dense to less dense
– Moist, cold air is more dense, than dry warm
Adiabatic cooling results in rain shadows
on the back side of mountains.
Earth has three Hadley
cells per hemisphere with
breaks at 0, 23-30, 50-60
and 90 degrees.
Jupiter, which is a larger
planet than Earth, has
more Hadley cells.
~
El Nino
~
La Nina
~
Figure 4.15a
Figure 4.15c