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 Growth Dispersal Flowering seed phase 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) Internode length (l) Shoot q Branch angle (q) Root

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

Intermediate growth in all locations Predictions and Results Mixed Treatment Nutrient Rich Areas Nutrient Poor Areas Intermediate growth in all locations Short internodes Long internodes Profuse branching Few branches Many large ramets Few small ramets High shoot:root Low shoot:root

What role does physiological integration play? 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

Production of seeds with no fertilization Agamospermy Production of seeds with no fertilization

Key Stages in the Life-History of a Plant Seed Maturation Growth Dispersal Flowering seed phase 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