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Life Histories and Tradeoffs
Tradeoffs
“If two processes require the use of
a limiting resource, then allocation
of the resource to one process
requires de-allocation to the
second.”
Key Stages in the Life-History of a Plant
Seed Maturation
Flowering
seed phase
Growth
Dispersal
Dormancy
Pollination
Germination
Growth in Plants
Growth
Apical meristems
Source of plant elongation;
often acting to suppress
lateral growth from other
nodes
Growth
Apical meristems
Axillary meristems
at nodes
Gives rise to leaves and
flowers; can also form lateral
branches when not
suppressed by apical
meristem
Growth
Apical meristems
Axillary meristems
at nodes
Internodes
Growth between adjacent
nodes
Growth
Apical meristems
Axillary meristems
at nodes
Internodes
Secondary growth
Cambium in many perennial
plants (not monocots) allows
them to increase in girth over
time
Plant growth is generally
a Modular Process
Clonal Growth
Forms of Clonal Growth
Phalanx
Guerilla
Modes of Foraging Behavior
Number of Branches (n)
Ramet size (S)
Shoot
q
Root
Branch angle (q)
Optimal Foraging?
Nutrient Rich
Nutrient Poor
Nutrient Rich
Optimal Foraging: Rich Habitat
X
Optimal Foraging: Poor Habitat
X
Optimal Foraging through a Plastic Response
Predictions
Nutrient Rich Habitat
Nutrient Poor Habitat
• Short internodes
• Long internodes
• Profuse branching
• Few branches
• Acute branch angles
• Obtuse branch angles
• High shoot:root
• Low shoot:root
An Experimental Test of
Optimal Foraging
The plant: Glechoma hederacea
Slade, A. J., and M. J. Hutchings. 1987. The effects of nutrient availability on foraging in the clonal herb
Glechoma hederacea. Journal of Ecology 75:95-112.
General Growth Pattern
Experimental Design
Nutrient poor
Legend
Nutrient rich
Mixed
Predictions and Results
Nutrient Rich Habitat
Nutrient Poor Habitat
• Short internodes
• Long internodes
• Profuse branching
• Few branches
• Many large ramets
• Few small ramets
• High shoot:root
• Low shoot:root
Predictions and Results
Mixed Treatment
Nutrient Rich Areas
• Short internodes
Nutrient Poor Areas
• Long internodes
Intermediate
locations
• Profuse
branchinggrowth• in
Fewall
branches
• Many large ramets
• Few small ramets
• High shoot:root
• Low shoot:root
General Interpretation
• Glecoma hederacea exhibits a plastic growth
response to nutrient conditions
• This response is not localized, but represents
an average to conditions encountered across
the clone
What role does physiological
integration play?
Physiological Integration through Movement of
Resources
Xylem: Transport of raw
materials, e.g., H20
and soil nutrients
Phloem: Transport of
products of
photosynthesis
Experimental Examination of Integration
through Xylem
Experimental design
• Cut leaf off
• Inject fuchsin
dye into xylem
Price, E. A. C., C. Marshall, and M. Hutchings. 1992. Studies of
growth in the clonal herb Glechoma hederacea. I. Patterns of
physiological integration. Journal of Ecology 80:35-38.
Experimental Examination of Integration
through Xylem
Experimental results
• Complex pattern of nutrient flow,
depends on xylem architecture
• Apparent unidirectional
flow of nutrients
Leaf with dye
Leaf without dye
Experimental Examination of Integration
through Phloem
Leaf labeled
with 14C
Experimental Examination of Integration
through Phloem
Resulting radiograph
Leaf labeled
with 14C
Experimental Examination of Integration
through Phloem
Interpretation
• Photosynthate stays in leaf
or is transported to young
developing tissues
• Source-sink relationship
General Interpretation of Experiments
• Patterns of physiological
integration can be shown
• Resource sharing seems to
be in the direction of
younger ramets
• Optimal foraging is an ideal
that is only partially met
Forms of Asexual Reproduction
in Plants
Clonal Growth (revisited)
Rhizome
Stolon
Bulbils
Suckers
Plantlets
Fragmentation: jumping cholla
Agamospermy
Production of seeds
with no
fertilization
Key Stages in the Life-History of a Plant
Seed Maturation
Flowering
seed phase
Growth
Dispersal
Dormancy
Pollination
Germination
Sexual
Reproduction in
Plants
Typical Angiosperm Lifecycle
Alternation of generations
• Sporophyte (2n)
• Gametophytes (1n)
Typical Angiosperm Lifecycle
Alternation of generations
• Sporophyte (2n)
• Gametophytes (1n)
Fertilization
Gender Expression in Plants
♂
♀
Hermaphrodites
Sequential Hermaphrodism
Some plants change
sex over time!
Jack-in-the-pulpet
(Arisemea triphyllum)
Distribution of Flower Types