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/

• 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• Grass can be

• small – annual bluegrass• large – bamboo `

Grasses are vital to life on earth.

Grass Diversity

members of Poaceae plant familyMonocotyledonousmostly herbaceous (non woody)

jointed culms, sheathed leavesparallel 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 re-growth 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

Vascular Bundle surrounded by Bundle Sheath Cells

C4Plant

“Kranz Anatomy”

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

C4 plants: sugarcane, millet, corn, sorghum, bougainvillea

PEP carboxylase has no affinity for O2

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

Figure 4

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.

• 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

Flowering

What wasthe solution?

Go backto problems

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.

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 To overcome the lack of timber to build their houses the Homesteaders used sods of earth cut from the Plains as bricks. Homesteaders used sods of earth cut from the Plains as bricks. They built their houses out of this earth and called them sod They built their houses out of this earth and called them sod houses.houses.

Many sod houses were huge affairs, with many rooms, but they all Many sod houses were huge affairs, with many rooms, but they all suffered from the same problems. They were dirty, drafty and suffered from the same problems. They were dirty, drafty and leaked whenever it rained. The walls and floor were infested with leaked whenever it rained. The walls and floor were infested with lice, which crawled over the Homesteaders as they slept. Mud fell lice, which crawled over the Homesteaders as they slept. Mud fell off the ceiling into the Homesteaders’ cooking pots, and germs were off the ceiling into the Homesteaders’ cooking pots, and germs were rife. Despite this, many Homesteaders were proud of their first rife. Despite this, many Homesteaders were proud of their first ‘soddy’ and often lived in them for decades.‘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 NinoLa Nina

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Figure 4.15a

Figure 4.15c