Chapter 3BOT3015L

Biology of Flowering Plants: Reproduction

Flowers and Pollination

Presentation created by Danielle SherdanAll photos from Raven et al. Biology of Plants except when otherwise noted

Today

• Introducing angiosperms, flower structure and function

• Pollination

• Evolutionary trends in floral structure

• Inflorescences

• Monocots and dicots

• Introducing angiosperms, flower structure and function

• Pollination

• Evolutionary trends in floral structure

• Inflorescences

• Monocots and dicots

Saguaro cactus Apple

Cherry

Flowers are distinguishing characteristics of angiosperms

All fruits come from flowers

Sunflowers

Cattleya orchid

Angion=vesselSperma=seedAngiosperms have seeds contained in a vessel (developing ovary)

Flowers

What are the functions of flowers?

How are these functions important for the survival of species?

Honeysuckle

Flower dissectiona guided tour

Notice the arrangement of the floral parts

Arrangements of floral organs

Spiral arrangement of floral organs.

Stamens

Sepals

Petals

Carpels

Arrangement of floral organs in whorls.

Primitive Advanced

Flower dissectiona guided tour

Note that the petals are inserted after the sepals

What are the functions of these floral parts?

Alternation of Generations

generalized plant life cycle

In angiosperms, gametophytes are borne within the reproductive structures of the flower; thus flowers are important when discussing evolution of angiosperms

Flower dissectiona guided tour

stamen

What are the functions of the stamens?

Hint: collectively, the stamens are termed the androecium (andro=male, ecium=house).We will discuss the microgametophyte next week

The stamens of most grasses (left) and the paper birch (right) are easily blown by wind.The flowers of most grasses do not have showy petals, why?

Flower dissectiona guided tour

stamen

We will discuss more about the megagametophyte next week

Ovary, ovules (within ovary), style, and stigma comprise the carpel (megasporophyll)

What are the functions of the carpel?

Alternation of Generations

generalized plant life cycle

In angiosperms, gametophytes are born within the reproductive structures of the flower; thus flowers are important when discussing evolution of angiosperms

Requires pollination

Today

• Introducing angiosperms, flower structure and function

• Pollination

• Evolutionary trends in floral structure

• Inflorescences

• Monocots and dicots

Pollination

In angiosperms, movement of the microgametophyte (pollen grain) to the megagametophyte in the ovule of the carpel

How does a sessile organism, the microgametophyte in the case of angiosperms move?

Vectors

In the following discussion, notice the co-evolution of flowers and their biotic vectors

Some plants make big investments in attracting animal pollination vectors

Nectar

Notice the pollen on the hummingbird’s forehead and the stigma that touches it as he feeds

Some plants make big investments in attracting animal pollination vectors

Pollen

Seat bee gathering pollen from the stamens of a cactus

flower

Some plants make big investments in attracting animal pollination vectors

Cypridium sp.

Koning, Ross E. 1994. Pollination Adaptations. Plant Physiology Information Website. http://koning.ecsu.ctstateu.edu/Plants_Human/pollenadapt.html. (5-25-105).

Drugs (Intoxication)

Some plants make big investments in attracting animal pollination vectors

Ophrys bécasse Charentephotonature-pvd.chez.tiscali.fr/ ophrys.htm

Prospect of Sex (pseudocopulation)

Ophrys speculum

Plants that rely on wind make big investments in pollen

grass birch

Notice the stigmas that fan out to easily catch pollen

Pollination Biology movie

Today

• Introducing angiosperms, flower structure and function

• Pollination

• Evolutionary trends in floral structure

• Inflorescences

• Monocots and dicots

Evolutionary Trends in Floral Structure

1. Reduction in number of parts

Perfect and Imperfect flowers

FromOutlaw lecture

Evolutionary Trends in Floral Structure

1. Reduction in number of parts

3. Fusion of organs

2. Cyclic arrangement (vs. spiral)

Fusion of floral parts

Angel trumpet has fused petals that form a floral tube

Outlaw lecture notes

Fusion of organs

Notice the stamens fused to the carpel of this hibiscus flower

Danielle SherdanNE Tallahassee, FL

Fusion of floral partsSuperior and Inferior ovaries

Superior ovary (primitive)—note typical appearance of order of insertion of floral parts.

Superior, parts still appear to arise in normal order.

Inferior, floral tube fused to ovary wall, making ovary appear to arise below other floral parts.

Primitive Advanced

Evolutionary Trends in Floral Structure

1. Reduction in number of parts

3. Fusion of organs

2. Cyclic arrangement (vs. spiral)

4. Away from marginal placentation

Placentation

Parietal

Axile

Free central

Primitive

Advanced

MarginalSeeds attached

to margin of single carpel

Fusion of carpels

The ovary develops into the fruit, another distinguishing characteristic of angiosperms

Within each ovule, double fertilization, a distinguishing characteristic of angiosperms, produces the zygote and endosperm.

Evolutionary Trends in Floral Structure

1. Reduction in number of parts

3. Fusion of organs

2. Cyclic arrangement (vs. spiral)

4. Away from marginal placentation

5. Away from regularity e.g. toward bilateral symmetry over radial symmetry

Bilateral and Radial Symmetry

This orchid, an advanced monocot, displays bilateral symmetry

This wintergreen displays radial symmetry, which is primitive, but fused carpels, which is advanced

Today

• Introducing angiosperms, flower structure and function

• Pollination

• Evolutionary trends in floral structure

• Inflorescences

• Monocots and dicots

InflorescencesGroups of flowers in particular arrangements

Lupine

Some examples

InflorescencesGroups of flowers in particular arrangements

What is a fitness advantage of having inflorescences?

What is a fitness disadvantage of having inflorescences?

InflorescencesGroups of flowers in particular arrangements

Notice that these composites display many evolutionarily advanced characteristics

Today

• Introducing angiosperms, flower structure and function

• Pollination

• Evolutionary trends in floral structure

• Inflorescences

• Monocots and dicots

Monocots and Dicotsthe two major groups of angiosperms

Monocots and dicots have several differentiating characteristics

Number of cotyledons

Function of cotyledonsSeed structure at maturity

Number of flower parts

Root structure

Secondary growth in shootArrangement of vascular bundles

Leaf venation

Observe today

In your lab notebook, create a table to contrast these traits in monocots and dicots