Plant Physiology
Morphology
Seasonality andLife Cycles
Grazing and Plant Growth
SeasonalGrowth Rates
Germinationand SeedlingEstablishment
GrazingOptimization
Carbohydrates and
Allocation
Reproduction
GrassAnatomy
ForbAnatomy
ShrubAnatomy
You are hereSecondary Compounds
GrazingResistance
Forage Quality
RANGE PLANT GROWTH AND DEVELOPMENT
RDM
Grazing Effects
Photosynthesis
Water andNutrients
Life Cycles and
Phenology
Seasonality and Life Cycles Terminology Life Cycles Seasonal growth
rates Forage Quality RDM
Seasonality andLife Cycles
SeasonalGrowth Rates
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Forage Quality
RDM
Life Cycles and
Phenology
The Phenology Handbook, pg 1-15 George et al. 2001. Annual Range Forage Production George and Bell. 2001. Using Stage of Maturity……..
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Seasonality andLife CyclesREADING AND REFERENCES
SEASONALITY & LIFE CYCLES
SEASONALITY & LIFE CYCLES
Terminology Life Cycles Forage Quality Seasonal growth rates RDM
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Plant Physiology
TERMINOLOGY
Annual Perennial
Seasonality andLife Cycles
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Grass: monocot, most are not woody
Forb: dicot, non-woody
ShrubDicot,
woody
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Seasonality andLife CyclesTERMINOLOGY
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Seasonality andLife CyclesTERMINOLOGY
PHENOLOGY is the science that measures the timing of life cycle events for plants, animals, and microbes, and detects how the environment influences the timing of those events.
In the case of flowering plants, these life cycle events, include leaf budburst, first flower, last flower, first ripe fruit, seed set, leaf shedding, others.
SEASONALITY & LIFE CYCLES
Terminology Life Cycles Forage Quality Seasonal growth rates RDM
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Plant Physiology
LIFE CYCLES
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Seasonality andLife Cycles
ANNUAL LIFE CYCLES
Annuals Germination Vegetative
Seedling establishment
Leaf growth Winter growth is slow Growth accelerates
in spring Flowering Seed Set, Drying Dry and Die
Seasonality andLife Cycles
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ANNUAL LIFE CYCLE CALENDAR
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N D J F M A M J J A S O
Germination & Seedling Establishment
Slow Vegetative Growth Rapid Vegetative Growth Little or No Vegetative Growth
Tiller Development
Flowering
Seed Development
Seed Set
Drying Stems & Leaves
Dry & Dead Stems & Leaves
Seasonality andLife Cycles
Timing of phenological events
PERENNIAL LIFE CYCLES
Perennials Lives several years Sexual reproduction Vegetative
reproduction Stolons and Rhizomes
Winter dormancy Dry season dormancy Vegetative phase Flowering Seed set and dispersal Dormancy
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Seasonality andLife Cycles
PERENNIAL LIFE CYCLE CALENDAR
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N D J F M A M J J A S O
Dormant or Slow Vegetative Growth Rapid Vegetative Growth Slow Vegetative Growth
Dormant Tiller Development Tiller Development
Dormant Carbohydrate Use Carbohydrate Storage
Apical Meristems Near Soil Surface Flower Stems Elongate
Flowering
Seed
Development
Seed Set
Drying Stems &
Leaves
Dry & Dead Stems & Leaves
Seasonality andLife Cycles
Timing of phenological events
PHENOLOGY AND LIFE CYCLES
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Seasonality andLife Cycles
Phenological events
SEASONALITY & LIFE CYCLES
Terminology Life Cycles Forage Quality Seasonal growth rates RDM
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Plant Physiology
Crude protein decreases in annual grasses with stage of maturity(see ANR Publications 8019 and 8022)
PHENOLOGY AND FORAGE QUALITY
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Seasonality andLife Cycles
SEASONALITY & LIFE CYCLES
Terminology Life Cycles Forage Quality Seasonal growth rates RDM
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Plant Physiology
SEASONAL GROWTH RATES
Series10
500
1000
1500
2000
2500
3000
3500
lbs/
ac
Average Monthly Peak Standing Crop at UC SFREC
D1 J1 F1 M1 A1 M1 Peak
http://groups.ucanr.org/sierrafoothill/files/67089.pdf
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Seasonality andLife Cycles
SEASONAL GROWTH RATES
Growth rates of perennials in northeastern California
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1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul0
200
400
600
800
1000
1200
1400
lbs/
ac
Seasonality andLife Cycles
SEASONALITY & LIFE CYCLES
Terminology Life Cycles Seasonal growth rates Forage Quality RDM
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Plant Physiology
LITTER: RESIDUAL DRY MATTER
Moderate grazing results in recommended RDM levels
Heavy grazing results in low RDM levelsLight grazing results in high
RDM levels
Seasonality andLife Cycles
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SUMMARYSeasonality and
Life Cycles
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In this section you have learned the differences between annual and perennial life cycles and how plant growth rates and forage quality change as range and pasture plants move through their life cycle.
Plant PhysiologySeasonality and
Life Cycles
Grazing and Plant Growth
SeasonalGrowth Rates
Germinationand SeedlingEstablishment
GrazingOptimization
Carbohydrates and
Allocation
Reproduction
GrassAnatomy
ForbAnatomy
ShrubAnatomy
You are hereSecondary Compounds
GrazingResistance
Forage Quality
RANGE PLANT GROWTH AND DEVELOPMENT
RDM
Grazing Effects
Photosynthesis
Water andNutrients
Life Cycles and
Phenology
Morphology
Morphology Grass Anatomy Forb Anatomy Shrub Anatomy Reproduction
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Reproduction
GrassAnatomy
ForbAnatomy
ShrubAnatomy
Morphology and Development
Briske, 1991. Chp 4. Dev. Morph and Phys of Grasses. Introduction and Developmental Morphology Sections.
Skinner and Moore. Growth and Dev of Forage Plants
How Grass Grows
READING AND REFERENCESMORPHOLOGY
MORPHOLOGY
Grass Anatomy Forb Anatomy Shrub Anatomy Reproduction
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Plant Physiology
GRASS ANATOMY
Please review “How Grass Grows” at the link below. Overview of the Grass Plant
Shoot Development Crown Leaf Formation Leaf Expansion Dynamics Tillering Rhizome and Stolon Development Flowering
Root Development Germination Process Seasonal Development
http://www.files.ahnrit.vt.edu/files/flash/howgrassgrows/howgrassgrows.swf
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Morphology and Development
GROWING POINTS
Apical meristems (flower) Axillary buds (give rise to
tillers, rhizomes and stolons) Intercalary meristems or collar
(leaf expansion) Some growing points become
elevated as the growing season progresses.
Buds near the ground are less likely to be grazed
Delaying bud elevation reduces risk of bud removal by grazing
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Morphology and Development
Apical meristems (flower) Axillary buds (give rise to
tillers, rhizomes and stolons) Intercalary meristems or collar
(leaf expansion) Some growing points become
elevated as the growing season progresses.
Buds near the ground are less likely to be grazed
Delaying bud elevation reduces risk of bud removal by grazing
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Morphology and DevelopmentGROWING POINTS
Apical meristems (flower) Axillary buds (give rise to tillers,
rhizomes and stolons) Intercalary meristems or collar
(leaf expansion) Some growing points become
elevated as the growing season progresses.
Buds near the ground are less likely to be grazed
Delaying bud elevation reduces risk of bud removal by grazing
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Morphology and DevelopmentGROWING POINTS
Apical meristems (flower) Axillary buds (give rise to tillers,
rhizomes and stolons) Intercalary meristems or collar
(leaf expansion) Some growing points become
elevated as the growing season progresses.
Buds near the ground are less likely to be grazed
Delaying bud elevation reduces risk of bud removal by grazing
Apical meristem rising
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Morphology and DevelopmentGROWING POINTS
VEGETATIVE PHASE
In the vegetative phase, shoots consist predominantly of leaf blades.
Leaf blade collars remain nested in the base of the shoot and there is no evidence of sheath elongation or culm development.
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Morphology and Development
ELONGATION (TRANSITION) PHASE
Floral induction - Apical meristems is gradually converted from a vegetative bud to a floral bud.
During the transition phase, leaf sheaths begin to elongate, raising the meristematic collar zone to a grazable height.
Culm internodes also begin elongation in an "un-telescoping" manner beginning with the lowermost internode thereby raising the meristematic zone (floral bud and leaf bases) to a vulnerable position.
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Morphology and Development
REPRODUCTIVE PHASE
The flowering phase begins with the conversion from vegetative to floral bud.
Much of this is unseen until the emergence of the seed head from the sheath of the flag leaf (boot stage).
Within a few days, individual florets within the seed head are ready for pollination.
Apical meristem rising
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Morphology and Development
MORPHOLOGY
Grass Anatomy Forb Anatomy Shrub Anatomy Reproduction
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Plant Physiology
FORB ANATOMY
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Morphology and Development
FORB GROWING POINTS
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Growing point or apical bud
Morphology and Development
MORPHOLOGY
Grass Anatomy Forb Anatomy Shrub Anatomy Reproduction
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Plant Physiology
SHRUB ANATOMY
Coast live oak resprouts
Chamise resprouts
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Morphology and Development
MORPHOLOGY
Grass Anatomy Forb Anatomy Shrub Anatomy Reproduction
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Plant Physiology
REPRODUCTION
Long Day Plants Short Day Plants Sexual Reproduction (flowers and seeds) Vegetative Reproduction (stolons, rhizomes)
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Morphology and Development
Some plants are long-day plants and others are short-day plants.
The long-day plants reach the flowering phenological stage after exposure to a critical photoperiod and during the period of increasing daylight between mid April and mid June.
Generally, most cool-season plants with the C3 photosynthetic pathway are long-day plants and reach flower phenophase before 21 June.
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Morphology and DevelopmentREPRODUCTION -
LONG DAY PLANTS
Short-day plants are induced into flowering by day lengths that are shorter than a critical length and that occur during the period of decreasing day length after mid June.
Short-day plants are technically responding to the increase in the length of the night period rather than to the decrease in day length.
Generally, most warm-season plants with the C4 photosynthetic pathway are short-day plants and reach flower phenophase after 21 June.
The annual pattern in the change in daylight duration follows the calendar and is the same every year for each region.
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Morphology and DevelopmentREPRODUCTION
SHORT DAY PLANTS
REPRODUCTION
Plant populations persist through both asexual (vegetative) reproduction and sexual reproduction.
The frequency of true seedlings produced from seed is low in established grasslands and occurs only during years with favorable moisture and temperature conditions in areas of reduced competition from older tillers, and when resources are easily available to the growing seedling.
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Morphology and Development
Sexual reproduction is necessary for a population to maintain the genetic diversity enabling it to withstand large-scale changes.
However, production of viable seed each year is not necessary to the perpetuation of a healthy grassland.
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Morphology and DevelopmentREPRODUCTION
SEXUAL
Reproductive shoots are adapted for seed production rather than for tolerance to defoliation
Grass species that produce a high proportion of reproductive shoots are less resistant to grazing than are those species in which a high proportion of the shoots remains vegetative.
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Morphology and DevelopmentREPRODUCTION
SEXUAL
Vegetative growth is the dominant form of reproduction in semiarid and mesic grasslands
Annual plants are dependent on seed production each year for survival.
Short-lived perennials depend on seed production.
Long-lived perennials rely more on vegetative reproduction.
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Morphology and DevelopmentREPRODUCTION
ASEXUAL OR VEGETATIVE
TILLERINGMorphology and
Development
REPRODUCTION
Bunch grasses spread by the production of tillers.
Stoloniferous grasses spread by lateral stems, called stolons, that creep over the ground and give rise to new shoots periodically along the length of the stolon.
Rhizomatous grasses spread from below ground stems known as rhizomes.
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Morphology and Development
ASEXUAL OR VEGETATIVE
SUMMARY
.
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Morphology and Development
In this section you learned about plant growing points, how plants grow, phases of plant growth and reproduction. You learned that vegetative reproduction in the form of tillers, stolons and rhizomes are more important than reproduction via seeds in most grasslands. You also learned that buds close to the ground are less vulnerable to grazing than when they are elevated.
Plant Physiology
Morphology
Seasonality andLife Cycles
Grazing and Plant Growth
SeasonalGrowth Rates
Germinationand SeedlingEstablishment
GrazingOptimization
Carbohydrates and
Allocation
Reproduction
GrassAnatomy
ForbAnatomy
ShrubAnatomy
You are hereSecondary Compounds
GrazingResistance
Forage Quality
RANGE PLANT GROWTH AND DEVELOPMENT
RDM
Grazing Effects
Photosynthesis
Water andNutrients
Life Cycles and
Phenology
Plant Physiology Germination &
Seedling Establishment
Photosynthesis Carbohydrates
and Carbohydrate Allocation
Water and Nutrients
Secondary Compounds
Plant Physiology
Germinationand SeedlingEstablishment
Carbohydrates and
Allocation
Secondary Compounds
Photosynthesis
Water andNutrients
McKell, C.M. 1974. Morphogenesis and management of annual range plants in the United States. Pg 111-116.
Briske, 1991. Chp 4. Dev. Morph and Phys of Grasses. Grazing Resistance Section.
Waller and Lewis. 1979. Occurrence of C3 and C4 photosynthetic pathways in North American grasses.
Carbohydrate Reserves: What you learned may be wrong.
PLANT PHYSIOLOGY
READING AND REFERENCES
PLANT PHYSIOLOGY
Germination and Seedling Establishment
Photosynthesis Carbohydrates and Carbohydrate
Allocation Water and Nutrients Secondary Compounds
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Plant Physiology
GERMINATION & SEEDLING ESTABLISHMENT
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Plant Physiology
See Anatomy Embryo Endosperm (food
reserves) Seed coat (pericarp)
Variable seed production Empty seeds
Empty Seeds
Seed Coat
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Plant PhysiologyGERMINATION & SEEDLING ESTABLISHMENT
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Plant PhysiologyGERMINATION & SEEDLING ESTABLISHMENT
PHOTOTROPISMReturn to Course Map
Plant Physiology
Oxygen is required for respiration during germination.
Oxygen is found in soil pore spaces but if a seed is buried too deeply within the soil or the soil is waterlogged, the seed can be oxygen starved.
Some seeds have impermeable seed coats sometimes called hard seed.
Hard seed is common in legumes
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Plant PhysiologyGERMINATION & SEEDLING ESTABLISHMENT
Temperature also influences germination.
Seeds from different species and even seeds from the same plant germinate over a wide range of temperatures.
Seeds often have a temperature range within which they will germinate, and they will not do so above or below this range.
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Plant PhysiologyGERMINATION & SEEDLING ESTABLISHMENT
Some seeds require exposure to cold temperatures (vernalization) to break dormancy.
Seeds in a dormant state will not germinate even if conditions are favorable.
Some seeds will only germinate following hot weather and others exposed to hot temperatures during a forest fire which cracks their seed coats.
Some seeds need to pass through an animal's digestive tract to weaken the seed coat enough to allow the seedling to emerge.
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Plant PhysiologyGERMINATION & SEEDLING ESTABLISHMENT
Variability in the rate of germination exists between and within species.
Seed size has been shown to be a critical factor in promoting seedling vigor.
In legumes and other forbs, seed coat hardness or impermeability often retards germination but spreads germination over years which is a survival advantage for the species.
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Plant PhysiologyGERMINATION & SEEDLING ESTABLISHMENT
On annual rangelands estimates of germinable seed exceed 20,000 per m2.
On annual rangelands the number of plants early in the growing season has been reported to vary from 20 to nearly 100 per square inch.
Considerable reduction in this number takes place as the season progresses. The lost seedlings decay and provide a flush of nutrients early in the growing season.
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Plant PhysiologyGERMINATION & SEEDLING ESTABLISHMENT
Rapid root growth is fundamental to establishment and development of annual rangeland plants.
Individual plants and species may gain an advantage over competitors if they exhibit rapid root growth and are able to maintain both rapid root and top growth.
Annual grasses frequently exhibit root growth rates greater than native perennial grasses
Annual grass (cheatgrass) roots (b) grew faster in this study than blue bunch wheatgrass (native perennial ) roots (a) (Harris 1977, JRM)
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Plant PhysiologyGERMINATION & SEEDLING ESTABLISHMENT
PLANT PHYSIOLOGY
Germination and Seedling Establishment
Photosynthesis Carbohydrates and Carbohydrate
Allocation Water and Nutrients Secondary Compounds
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Plant Physiology
CO2 + H2O CH2O + O2
Sunlight
Chlorophyll
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Plant PhysiologyPHOTOSYNTHESIS
FOUR FUNDAMENTAL CONCEPTS
Plants are the only source of energy for grazing animals.
The formation of sugars, starches, proteins and other foods is dependent on photosynthesis.
Plants do not get food from the soil. They obtain raw materials needed for photosynthesis and subsequent food production
When leaves are removed from plants, food-producing capacity is reduced.
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Plant Physiology
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To learn more about Photosynthesis:
http://www.youtube.com/watch?v=_wO9f3ER17M
Plant PhysiologyPHOTOSYNTHESIS
4. Physiological efficiency
5. Soil nutrients6. Water supply7. Temperature
Factors that influence photosynthetic rate1. Leaf area2. Light intensity and quality3. CO2 content of the air
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Plant PhysiologyPHOTOSYNTHETIC RATE
Relationship between light interception and leaf area (Brougham 1956)
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Plant PhysiologyLEAF AREA AND LIGHT INTENSITY
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Lightly grazed
Closely grazed
Plant PhysiologyPHOTOSYNTHESIS & LIGHT INTENSITY
(Parsons et al. 1983)
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Plant PhysiologyPHOTOSYNTHESIS & LEAF AREA
Relationship between leaf area and herbage yield (Brougham 1956)
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Plant PhysiologyPRODUCTION & LEAF AREA
Gross & Net Production
0
20
40
60
80
100
0 1 2 3 4 5 6 7 8 9 10
Leaf Area Index
Pho
tosy
nthe
sis
(% o
f m
axim
um G
PP
)
GPP NPP R
GROSS & NET PRIMARY PRODUCTION
NPP=GPP - R GPP and NPP
increase as leaves are added until upper leaves begin shading lower leaves then R increases resulting in decrease in NPP
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Plant Physiology
STOMATES AND WATER RELATIONS
Guard Cells
Stomate
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Plant Physiology
Water required for photosynthesis
Lost through stomates (transpiration)
Arid and semi-arid lands frequently subjected to water stress
Drought tolerant
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Plant PhysiologyWATER RELATIONS
PHOTOSYNTHETIC PATHWAYS
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Plant Physiology
C3, C4 & CAM Pathways
C3 because CO2 is first incorporated into a 3-carbon compound.
Stomata are open during the day. Photosynthesis takes place
throughout the leaf.
Adaptive Value: more efficient than C4 and CAM
plants under cool and moist conditions and,
under normal light conditions. Most plants are C3.
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Plant PhysiologyC3 PHOTOSYNTHESIS
CO2 is first incorporated into a 4-carbon compound
Stomata are open during the day. Photosynthesis takes place in inner bundle
sheath cells Adaptive Value:
Photosynthesizes faster than C3 plants under high light intensity and high temperatures.
Better water use efficiency than C3 because CO2 uptake is faster and so does not need to keep stomata open as much (less water lost by transpiration) for the same amount of CO2 gain for photosynthesis
C4 plants include several thousand species in at least 19 plant families
Examples: fourwing saltbush, corn, and many summer annual plants
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Plant PhysiologyC4 PHOTOSYNTHESIS
Crassulacean Acid Metabolism (CAM) Stomata open at night and are usually closed
during the day. The CO2 is converted to an acid and stored
during the night. During the day, the acid is broken down and
the CO2 is released for photosynthesis Adaptive Value:
Better Water Use Efficiency than C3 plants CAM-Idle
When conditions are extremely arid, CAM plants can just leave their stomata closed night and day.
CAM plants include many succulents such as cactuses and agaves and also some orchids and bromeliads
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Plant PhysiologyCAM PHOTOSYNTHESIS
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Plant Physiology
Waller, S.S. and J.K. Lewis. 1979. Occurrence of C3 and C4 Photosynthetic Pathways in North American Grasses. Journal of Range Management 32:12-28 for an review and list of C3 and C4 range plants.
COOL & WARM SEASON GRASSES
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Plant PhysiologyROOT GROWTH TEMPERATURES
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Plant PhysiologyWATER USE EFFICIENCIES
C3 VS C4
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Plant PhysiologyCO2 CONCENTRATION
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Plant PhysiologyLIGHT, TEMPERATURE AND CO2
C3 VS C4:
PLANT PHYSIOLOGY
Germination and Seedling Establishment
Photosynthesis Carbohydrates and Carbohydrate
Allocation Water and Nutrients Secondary Compounds
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Plant Physiology
Carbohydrates are the plant’s energy sourceEnergy needed for:• Root
replacement• Leaf and stem
growth following dormancy
• Respiration during dormancy
• Bud formation• Regrowth
following top removal
REDUCED CARBOHYDRATE STORAGE
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Plant Physiology
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Plant PhysiologyCARBON DISTRIBUTION/ALLOCATION
CARBON DISTRIBUTION/ALLOCATION
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Plant Physiology
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Plant PhysiologyCARBON DISTRIBUTION/ALLOCATION
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Plant PhysiologyCARBON DISTRIBUTION/ALLOCATION
PLANT PHYSIOLOGY
Germination and Seedling Establishment
Photosynthesis Carbohydrates and Carbohydrate
Allocation Water and Nutrients Secondary Compounds
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Plant Physiology
WATER AND NUTRIENT UPTAKE
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Plant Physiology
For more information on plant water movement see these two videos:http://www.youtube.com/watch?v=tRNe_UHw7F4http://www.youtube.com/watch?v=umUn8D6gEOg&feature=related
AVAILABLE WATER
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Plant Physiology
NUTRIENT UPTAKE
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Plant Physiology
MYCORRHIZAE
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Plant Physiology
PLANT PHYSIOLOGY
Germination and Seedling Establishment
Photosynthesis Carbohydrates and Carbohydrate
Allocation Water and Nutrients Secondary Compounds
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Plant Physiology
SECONDARY COMPOUNDS
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Plant Physiology
Many secondary compounds are toxic to livestock and humans. For more information see “Livestock-Poisoning Plants of California.
SECONDARY COMPOUNDS
Conifers accumulate monoterpenes
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Plant Physiology
TERPENES
Lignin Flavenoids Tannin
isoflavenoids in legumesTannins in oak leaves
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Plant PhysiologySECONDARY COMPOUNDS
PHENOLICS
Alkaloids
SECONDARY COMPOUNDS
Cynanogenic glycosides
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Plant Physiology
NITROGEN CONTAINING COMPOUNDS
SECONDARY COMPOUNDS
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Plant Physiology
ALLELOPATHY
SUMMARY
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Plant Physiology
In the plant physiology section you learned about germination and seedling establishment, photosynthesis, carbohydrate storage and allocation, plant water relations and nutrient uptake and secondary compounds. You learned that fire and heat can influence germination along with soil moisture and temperature. You also learned that photosynthetic rate increases with leaf area to some optimum level and then slows with continued increases in leaf area. You learned about three photosynthetic pathways (C3, C4 and CAM) and their adaptive value. You learned that carbohydrates produced during photosynthesis are used for plant growth or stored to meet future needs. And finally you learned about secondary compounds
Plant Physiology
Morphology
Seasonality andLife Cycles
Grazing and Plant Growth
SeasonalGrowth Rates
Germinationand SeedlingEstablishment
GrazingOptimization
Carbohydrates and
Allocation
Reproduction
GrassAnatomy
ForbAnatomy
ShrubAnatomy
You are hereSecondary Compounds
GrazingResistance
Forage Quality
RANGE PLANT GROWTH AND DEVELOPMENT
RDM
Grazing Effects
Photosynthesis
Water andNutrients
Life Cycles and
Phenology
Grazing and Plant Growth
Grazing Effects Grazing
Optimization Grazing Resistance
Grazing and Plant Growth
GrazingOptimization
GrazingResistance
Grazing Effects
Briske, 1991. Chp 4. Dev. Morph and Phys of Grasses. Grazing Resistance Section.
Trlica, J. 2006. Grass Growth and Response to Grazing.
A quick lesson in plant structure, growth and regrowth for pasture-based dairy systems.
Noy-Meir, I. 1993. Compensating growth of grazed plants and its relevance to the use of rangelands.
GRAZING & PLANT GROWTH
READING AND REFERENCES
GRAZING AND PLANT GROWTH
Grazing Effects Grazing Optimization Grazing Resistance
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Grazing and Plant Growth
GRAZING EFFECTS
Detrimental Effects Growth Promoting Effects
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Grazing and Plant Growth
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Grazing and Plant GrowthDETRIMENTAL GRAZING EFFECTS
Removal of photosynthetic tissue
Reduced carbohydrate storage
Reduced root growth Reduced seed
production
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Grazing and Plant Growth
1. Grazing that is too heavy can reduce leaf area and reduce photosynthesis and carbohydrate production.
Grazing can influence leaf area
REDUCED LEAF AREA FOR PHOTOSYNTHESIS
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Grazing and Plant Growth
1. Heavy grazing can weaken root systems increasing moisture stress
Grow leaves, stems, roots andbuds.
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REDUCE GROWTH
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Grazing and Plant Growth
1. Heavy grazing can weaken root systems increasing moisture stress
Leaves, stems, roots and other plant parts
REDUCE GROWTH
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Grazing and Plant Growth
Seed production
REDUCE GROWTH
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Grazing and Plant Growth
Carbohydrates are the plant’s energy source
REDUCED CARBOHYDRATE STORAGE
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Grazing and Plant Growth
Detrimental Effects Growth Promoting Effects
GRAZING EFFECTS
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Grazing and Plant Growth
Increased photosynthesis
Increased tillering Reduced shading Reduced transpiration
GROWTH PROMOTING EFFECTS
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Grazing and Plant Growth
1. Intensity 2. Timing3. Frequency4. Grazing of surrounding plants
INFLUENCES ON GRAZING EFFECTS
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Grazing and Plant Growth
1. Decreases evapotranspiration2. Moderates surface microclimate during germination and
seedling establishment3. Slows surface runoff and increases infiltration4. Protects soil from erosion
LITTER
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Grazing and Plant Growth
Grazing too close reduces reserves and slows recovery following grazing
GRAZING TO CLOSE
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Grazing and Plant Growth
Plant A was allowed to grow for three months without clipping. Healthy root system
Plant B was clipped to 3 inches every three weeks for 3 months. Healthy root system
Plant C was clipped to 1 inch every week for 3 months. Very weak root system and might not survive a drought
A CBReturn to Course Map
DETRIMENTAL EFFECTS OF GRAZING
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Grazing and Plant Growth
Heavy Grazing: Decreased photosynthesis Reduced carbohydrate
storage Reduced root growth Reduced seed production Reduced ability to compete
with ungrazed plants Reduce accumulation of
litter or mulch which decreases water infiltration and retention, plus it protects soil from erosion.
Light to Moderate Grazing: Increased plant productivity Increased tillering Reduced shading of lower
leaves Reduced transpiration
losses Reduced ability to compete
with ungrazed plants Reduction of excessive litter
or mulch that can physically or chemically inhibit vegetative growth. Excessive mulch promotes pathogens and insects that can damage forage plants.
Negative effects of heavy grazing vs. possible effects of light to moderate grazing on range plant physiology
SUMMARY
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Grazing and Plant Growth
Grazing Effects Grazing Optimization Grazing Resistance
GRAZING AND PLANT GROWTH
GRAZING OPTIMIZATION
There are levels of grazing that can result in increased productivity
G.O. is a complex and sometime controversial subject.
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Grazing and Plant Growth
GRAZING OPTIMIZATION HYPOTHESIS
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Grazing and Plant Growth
GRAZING OPTIMIZATION HYPOTHESIS
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Grazing and Plant Growth
Gross & Net Production
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GPP NPP R
NPP=GPP - R GPP and NPP
increase as leaves are added until upper leaves begin shading lower leaves then R increases resulting in decrease in NPP
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Gross & Net Production
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GRAZING OPTIMIZATION
NPP=GPP - R GPP and NPP increase as
leaves are added until upper leaves begin shading lower leaves then R increases resulting in decrease in NPP
Grazing reduces leaf area G.O. says if grazing keeps
LAI near 4, NPP is optimized.
May occur in some species, more likely in pasture.
Some species are extremely susceptible to grazing even at light intensities.
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Grazing and Plant Growth
GRAZING OPTIMIZATION
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Grazing and Plant Growth
C = ‘control’ no clippingTB = terminal bud removed only
60 = 60% current annual growth removed100 = 100% current annual growth removed
GRAZING OPTIMIZATION
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Grazing and Plant Growth
MECHANISMS CONTRIBUTING TO COMPENSATORY PLANT GROWTH
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Grazing and Plant Growth
Herbivore-induced physiological processes Accelerated photosynthesis per unit leaf area Accelerated nutrient absorption per unit root mass Greater resource allocation to shoots Increased tiller initiation Improved water status
Herbivore-mediated environmental modification Increased irradiance on remaining leaves and young tillers Conservation of soil water following leaf area removal Accelerated rate of nutrient cycling Increased activity of decomposer organisms
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Grazing and Plant Growth
Grazing EffectsGrazing OptimizationGrazing Resistance
GRAZING AND PLANT GROWTH
GRAZING RESISTANCE
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Grazing and Plant Growth
GRAZING AVOIDANCE
Mechanical Biochemical
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Grazing and Plant Growth
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Grazing and Plant Growth
PLANT MORPHOLOGY Grass, forb and shrub species produce viable
axillary buds have greater potential to regrow following grazing
Grass, forb, and shrub species that protect meristems have the potential to regrow quickly following grazing.
Grasses that develop tillers at different times during the grazing season tolerate grazing better than plants that do not
GRAZING TOLERANCE
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Grazing and Plant Growth
PLANT PHYSIOLOGY Ability to regrow quickly following grazing Ability to compete for water and nutrients
enable some plants to regrow more quickly In some plant grazing stimulates absorption
of nutrients. However, in many species removal of leaves and stems decreases nutrient absorption.
Ability to quickly move nutrients and carbohydrates between roots and shoots
GRAZING TOLERANCE
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Grazing and Plant Growth
Grasses
Higher proportion of culmless (stemless) shoots than species with low resistance
Greater delay in elongation of the apical buds than species with low resistance
Sprout more freely from basal buds after defoliation than species with low resistance.
Higher ratio of vegetative to reproductive stems than species with low resistance.
GRAZING RESISTANCE FACTORS
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Grazing and Plant Growth
Forbs Produce a large number of viable
seeds Delayed elevation of growing points Poisons and chemical compounds
that reduce palatability
GRAZING RESISTANCE FACTORS
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Grazing and Plant Growth
Shrubs Spines and thorns volatile oils and tannins
that reduce palatability Branches make removal of
inner leaves difficult Only current year’s growth
is palatable and nutritious for most species.
GRAZING RESISTANCE FACTORS
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Grazing and Plant Growth
Most to least resistant1. Grasses 2. Shrubs 3. Forbs
*Many exceptions do occur.
GRAZING RESISTANCE OF FORAGE
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Grazing and Plant Growth
In the final section you learned about grazing and plant responses to grazing.
You learned that grazing can have detrimental as well as growth promoting effects on plants.
We discussed the theory of grazing optimization and some of the mechanisms that can result in compensatory plant growth.
And finally we discussed mechanisms that allow plants to resist the effects of grazing.
SUMMARY
THE END: UNUSED SLIDES
The Phenology Handbook, pg 1-15 George et al. 2001. Annual Range Forage Production George and Bell. 2001. Using Stage of Maturity……..
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Seasonality andLife CyclesREADING AND REFERENCES
SEASONALITY & LIFE CYCLES
Briske, 1991. Chp 4. Dev. Morph and Phys of Grasses. Introduction and Developmental Morphology Sections.
Skinner and Moore. Growth and Dev of Forage Plants
How Grass Grows
READING AND REFERENCESMORPHOLOGY
McKell, C.M. 1974. Morphogenesis and management of annual range plants in the United States. Pg 111-116.
Briske, 1991. Chp 4. Dev. Morph and Phys of Grasses. Grazing Resistance Section.
Waller and Lewis. 1979. Occurrence of C3 and C4 photosynthetic pathways in North American grasses.
Carbohydrate Reserves: What you learned may be wrong.
PLANT PHYSIOLOGY
READING AND REFERENCES
Briske, 1991. Chp 4. Dev. Morph and Phys of Grasses. Grazing Resistance Section.
Trlica, J. 2006. Grass Growth and Response to Grazing.
A quick lesson in plant structure, growth and regrowth for pasture-based dairy systems.
Noy-Meir, I. 1993. Compensating growth of grazed plants and its relevance to the use of rangelands.
GRAZING & PLANT GROWTH
READING AND REFERENCES
McKell, C.M. 1974. Morphogenesis and management of annual range plants in the United States. Pg 111-116.
Briske, 1991. Chp 4. Dev. Morph and Phys of Grasses. Grazing Resistance Section.
Waller and Lewis. 1979. Occurrence of C3 and C4 photosynthetic pathways in North American grasses.
Carbohydrate Reserves: What you learned may be wrong.
PLANT PHYSIOLOGY
READING AND REFERENCES
Grass Anatomy Growing Points (buds, meristems) Developmental Anatomy
Forb Anatomy Growing Points (buds, meristems)
Reproduction Sexual Asexual
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Morphology
PLANT PHYSIOLOGY Germination and Seedling
Establishment Photosynthesis
Factors that influence photosysnthesis C3, C4, CAM Photosynthesis
Carbohydrates and Carbohydrate Allocation
Water and Nutrients Secondary Compounds
Plant Physiology
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Grazing and Plant Growth Grazing Effects Grazing Optimization Grazing Resistance
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Plant Physiology
Morphology
Seasonality andLife Cycle
Grazing and Plant Growth
Life CyclesAnd
PhenologySeasonal
Growth Rates
Germinationand seeding
establishment
GrazingOptimization
Carbohydrates andCarb. Allocation
Reproduction
GrassAnatomy
ForbAnatomy
ShrubAnatomyYou are here
Secondary Compounds
GrazingResistance
Forage Quality
PHYSIOLOGY AND MORPHOLOGY OF RANGE PLANTS
RDM
Grazing Effects
Photosynthesis
Water andNutrients
Plant Physiology
Morphology
Seasonality andLife Cycle
Grazing and Plant Growth
Life CyclesAnd
PhenologySeasonal
Growth Rates
Germinationand seeding
establishment
GrazingOptimization
Carbohydrates andCarb. Allocation
Reproduction
GrassAnatomy
ForbAnatomy
ShrubAnatomy
You are here
Secondary Compounds
GrazingResistance
Forage Quality
PHYSIOLOGY AND MORPHOLOGY OF RANGE PLANTS
RDM
Grazing Effects
Photosynthesis
Water andNutrients
Plant Physiology
Morphology
Seasonality andLife Cycle
Grazing and Plant Growth
Life CyclesAnd
PhenologySeasonal
Growth Rates
Germinationand seeding
establishment
GrazingOptimization
Carbohydrates andCarb. Allocation
Reproduction
GrassAnatomy
ForbAnatomy
ShrubAnatomyYou are here
Secondary Compounds
GrazingResistance
Forage Quality
PHYSIOLOGY AND MORPHOLOGY OF RANGE PLANTS
RDM
Grazing Effects
Photosynthesis
Water andNutrients
CHAPTER 5: RANGE PLANT PHYSIOLOGY
1. Basic concepts of plant growth2. Importance of carbohydrate reserves3. Grazing effect on forage plants 4. Grazing resistance in grasses, forbs and
shrubs5. Grazing theory a. Why palatable plants dominate
rangelands with good grazing management?
b. Why unpalatable plants dominate rangelands under sustained heavy grazing (over grazing)?
A FEW BASIC PRINCIPLES CONCERNING THE INFLUENCE OF GRAZING ON PLANTS
1. Plants must have leaves for photosynthesis.
2. Grazing has the least effect on plants during the dormant season when they are photosynthetically inactive.
3. Grazing has the most severe effect on plants towards the end of the growing season ( seed formation to seed hardening) because the plant’s demands for carbohydrates are higher and little time remains of optimal temperature and moisture conditions for regrowth.
4. Grazing early in the growing season has less effect on plants than late in the growing season because considerable time remains when temperature and moisture are optimal for regrowth.
WHY PLANTS MUST STORE CARBOHYDRATES 1. Root replacement and growth2. Regeneration of leaves and stems
after dormancy 3. Respiration during dormancy 4. Bud formation 5. Regrowth after top removal by
grazing.
PHOTOSYNTHESIS AND CARBOHYDRATES Factors that influence photosysnthesis C3, C4, CAM Photosynthesis Carbohydrates and Carbohydrate
Allocation
REPRODUCTION
Recruitment maintains plant community Sexual Reproduction (flowers and seeds) Vegetative Reproduction (stolons, rhizomes) Annuals dependent on seed production Short-lived perennials depend on seed production Long-lived perennials rely more on vegetative
reproduction.
Relationship between herbage dry matter and leaf area (Brougham 1956)
Increased photosynthesis
Increased tillering
Increased photosynthesis Reduced transpiration
Reduced shading
Reduced transpiration
SUMMARY EFFECTS OF LIGHT TO MODERATE GRAZING
Increased plant productivity Increased tillering Reduced shading of lower leaves Reduced transpiration losses Reduced ability to compete with ungrazed plants Reduction of excessive litter or mulch that can
physically or chemically inhibit vegetative growth. Excessive mulch promotes pathogens and insects that can damage forage plants.
LIFE CYCLES Return to Course Map
Bilbrough and Richards (1993)
C = ‘control’ no clippingTB = terminal bud removed only
60 = 60% current annual growth removed100 = 100% current annual growth removed
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Grazing and Plant Growth
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Grazing and Plant Growth
CARBOHYDRATE STORAGE1. Root replacement and growth2. Regeneration of leaves and stems
after dormancy 3. Respiration during dormancy 4. Bud formation 5. Regrowth after top removal by
grazing.
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Grazing and Plant Growth
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GRAZING OPTIMIZATION
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Grazing and Plant Growth
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