Flower Reproduction: Stamen and Carpel

• A flower contains male and female reproductive parts.

Flower Parts

• Stamen is the male reproductive part.
• Carpel or pistil is the female reproductive part.
• Filament and anther are parts of the stamen.
• Stigma, style, and ovary are parts of the carpel.
• Petals together form the corolla.
• Sepals together form the calyx.
• The ovule forms within the ovary.
• The receptacle is located at the base of the flower.

Floral Whorls

• Sepals and petals are accessory parts.
• Stamen/androecium and carpel/pistil/gynoecium are vital parts.

Carpel Evolution

• Begаn as a modified leaf with sporangia.
• Leaf edges curled inwards and fused through evolution.
• Three carpels fused to form a three-chambered ovary.

Stamen Evolution

• The leaflike portion of the stamen progressively reduced.
• Only the microsporangia remained.

Stamen vs Carpel

• Stamen is the male fertilizing organ, consisting of a pollen-containing anther and a filament.
• Carpel is the female reproductive organ, consisting of an ovary, stigma, and usually a style.
• Stamen is the male reproductive structure, while carpel is the female reproductive structure.
• Androecium refers to the collection of anthers and filaments (a stamen), gynoecium refers to a single set of the ovary, style, and stigma (a carpel).
• Stamen occurs surrounding the female reproductive structure, and carpel occurs at the center of the flower.
• Stamen produces pollen grains, while carpel produces ovules.
• Stamen releases pollen grains for pollination, and with carpel the stigma captures pollen grains.
• Pollen grains germinate, producing male gametes, and with carpel, ovules possess eggs inside the embryo sac.

Gynoecium, Pistil, Carpel

• Gynoecium refers to all female parts of a flower.
• Pistil is a structure consisting of the ovary, style(s), and stigma(s).
• Carpel is a conduplicate megasporophyll, and it can be a unit of pistil if the pistil is compound, with more than one carpel.

Gynoecium Terminology

• Monocarpous (single carpel) is termed a simple pistil; like avocado and most legumes
• Apocarpous (multiple distinct carpels) are termed simple pistils; like strawberry and buttercup
• Syncarpous (multiple connate carpels) are termed a compound pistil; like tulip and most flowers

Androecium

• Stamen parts include the anther, thecae, filament, and staminal disk.
• Types of stamen arrangements include tetradynamous and didynamous.

Connation

• Connation is the fusion of floral parts from the same whorl.
• Fused filaments form a staminal tube.
• Types of fused filaments arrangements include diadelphous and monadelphous.
• Anthers can be connate, or syngenesious.

Perianth fusion Examples

• Aposepalous/apopetalous means unfused.
• Synsepalous/sympetalous means fused.

Floral Variations

• Floral whorls may be complete (all 4 whorls are present) or incomplete (either/or are not present).
• Essential parts can be perfect (both stamen and pistil are present;hermaphroditic) or imperfect (either/or are not present).
• Symmetry can be radial/actinomorphic (2 equal halves; odd amounts) or bilateral/zygomorphic (dividing 2 equal halves only by medial cut through the central axis).
• Nature of the corolla can be polypetalous (many petals in one plant) or gamopetalous (fused petals).
• Flowers can be apetalous which means no petals.
• Ovary position can be perigynous, epigynous (ovary is covered with sepals), or hypogynous (more attached to the base).
• Arrangement of parts includes ovary superior (hypogynous or perigynous) or ovary inferior (epigynous).
• Placentation types include marginal, axile, parietal, free-central, basal, and apical.

Inflorescence

• Inflorescence is a collection/aggregation of flowers.
• A peduncle is the stalk of the inflorescence, while inflorescence axes are the branches of the inflorescence.
• A bract is a flower bract or inflorescence bract.
• A flower bract subtends an individual flower.
• Inflorescence bract subtends an entire inflorescence or an inflorescence axis.
• An Involucre is a group of inflorescence bracts subtending an entire inflorescence.
• A spathe is a specialized single inflorescence bract, which subtends an entire inflorescence with a spadix in Araceae.
• Inflorescence positions can be terminal or axillary.
• Inflorescence development can be determinate (terminal flower develops first) or indeterminate (basal flower develops first).

Indeterminate Inflorescences Types

• Raceme
• Panicle
• Spike
• Catkin
• Corymb
• Head

Determinate Inflorescences Types

• Dichasium

Specialized Inflorescences

• Spadix

Flower Variation Summary

• Four whorls: complete / incomplete
• Essential parts: perfect / imperfect
• Nature of corolla: polypetalous (free petals) / gamopetalous (fused petals) / apetalous (no petals)
• Symmetry: actinomorphic / zygomorphic
• Position of Ovary: superior / inferior
• Attachment of floral parts: Epi- / hypo- / perigynous
• Placentation: Marginal / axile / basal / free central / parietal
• Inflorescence: solitary / raceme / cyme / umbel / corymb / spike / panicle / catkin / spadix / composite

Flowers

• Important for sexual reproduction and also important for evolution
• Flowers produce variable offspring, creating diversity
• Variation is needed for natural selection to happen
• Being advantageous to an organism also requires being advantageous to another organism.
• Most plants have both sexes on one body.

Selfing

• Selfing is indreeding.
• Only 10-15% of flowering plants are selfers.
• Selfers rely on self-compatibility.
• Selfing can be be accompanied by structural mechanisms.
• Some species are obligate selfers with no choice.

Methods to Prevent Self-Pollination

• Dichogamy is when anthers and stigmas mature at different times; includes protandry and protogyny.
• Plants can have unisexual flowers; one-gendered plant.
• Incompatibility when plants produce a chemical in the stigma to prevent germination of their own pollens.
• Heterostyly exists as thrum-eyed (anthers high up and stigmas low down) and pin-eyed (stigmas high up and anthers low down).