Flowers
Flowers are modified Leaves. This is not readily apparent in most cases. However, there are cases in which floral organs display a gradient of leaf traits starting with the Sepals which are most leaf-like to Carpels which are highly specialized and do not resemble leaves.
The most basic Floral Terms are given below.
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. Receptacle = Place on stem where floral organs originate & attach
Sepals = Lowest order of floral organs, first to develop, can be green & leaf-like, Collectively = Calyx
Petals = Inserted on the Receptacle just above the Sepals, usually brightly colored, Collectively = Corolla
Perianth = Collective term for Sepals + Petals
Stamen = Inserted above Petals, consists of Anther & Filament, Collectively = Androecium
Anther - Part of Stamen that Produces Pollen
Filament - Stalk that bears the Anther
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. Carpel = Inserted above Stamens, uppermost floral organ, Consists of Stigma, Style & Ovary, Collectively = Gynoecium
Stigma - Tip of the carpel, Receptive to Pollen
Ovary - Base of the carpel, contains Ovules
Style - Connects the Stigma to the Ovary
Apocarpous - Flower with Free Carpels
Hypogenous
- "Superior Ovary" - Other floral organs attached below the gynoecium
on the receptacle.
Coalescence or Fusion - Fusion or union of floral organs from the same whorl or type - Designated by Sym or Syn
.
Complete - Has all four floral Organs
Incomplete - One or more floral organs missing
Perfect - Flower with Androecium & Gynoecium
Imperfect - Missing Androecium or Gynoecium
.Carpellate Flower - Imperfect that has Carpels only
Staminate Flower - Imperfect that has Stamens only
Monoecious (One House) - One plant has BOTH Carpellate & Staminate Flowers
Dioecious (Two Houses)- One plant has only staminate flowers & another plant has only Carpellate Flowers
Hypogenous
- "Superior Ovary" - Other floral organs attached below the gynoecium
on the receptacle.
Perigynous
- Sepals, Petals & Stamens arise from a tubular extension of the receptacle
called the Hypanthium which surrounds the Ovary but is NOT fused to the Ovary
Wall.
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. Epigynous - "Inferior Ovary" - Stamens, Petals & Sepals appear to grow from the top of the Ovary
. Flowers & Fruits-
The Flower represents the most important reproductive adaptation for plants. The Ovules of the flower are enclosed bu the Ovary Wall or Pericarp. This protects them during their development and maturation. Furthermore, the Pericarp becomes the principal part of the Fruit.
. Fruits not only add another protective layer but they also have specific adaptations for seed dispersal via biotic and abiotic agents.
. Ancestral flowers contained many Sterile and Fertile Elements and relied on wind or water for fertilization and seed dispersal. More specialized or Advanced Flowers have highy specialized adaptations for both of these vital reproductive functions. The successful, rapid evolutionary explosion of Angiosperms could not have ocurred without the advent of the flower.
. The table below contans a few example of flowers which have various mixtures of Ancestral and Derived Traits. The "Primitive" flowers are on the left and the "Advanced" are towards the right
The Vegetative Organs are the Root, Stem and Leaf. The flower contains various Organs.
Floral organs are modified leaves! They are formed at the shoot apex in the same manner as other leaves, and some floral parts like sepals and petals may be clearly leaf-like in their morphology.
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. Most Stamens and Carpels are not "leafy" in their appearance. However, some plants produce leaf-like Stamens and Carpels. Furthermore, careful anatomical studies have shown that these floral organsare highly modified leaves
. The Floral Organs
SepalsThe Sepals constitute the Calyx
The Petals comprise the Corolla
The Sepals and Petals are collectively called the Perianth.
Stamens comprise the Androecium (Male House)
Carpels comprise the Gynoecium (Female House).
The morphological unit of the Gynoecium is the Carpel.
The term Pistil has been used in the past to describe the gynoecium and this can cause some confusion in terminology.
A Gynoecium of a flower may contain 1 carpel, 2 carpels or n Carpels.
The Carpels may be free (Apocarpous) or united (Syncarpous)
. .
Ranunculus - Apocarpous Gynoecium
We will use the Buttercup (Ranunculus) as a model of an Apocarpous Flower
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The Carpels contain Ovules in their Ovaries.
These contain the Megagametophyte which is called the Embryo Sac in angiosperms.
Androecium: The Stamens consist of two parts. The Anther & the Filament that supports it.
The Anther produces Pollen which is the Microgametophyte
.
. The Lily Flower
Lilium is typically used to teach floral morphology and sexual reproduction. Consequently, we will examine it!
Perianth = Tepals = 3 Free Sepals & 3 Free Petals
Androecium = 6 Free Stamens
Gynoecium = 3 Carpels (Syncarpous)
Superior Ovary= Hypogenous
Outline
Dicots versus Monocots
Structure of Flowers
Fruits
Fleshy
Dry
Fruit and Seed Dispersal
Seeds
Germination
Longevity
Dicots versus Monocots
Dicots
Two cotyledons
Flower parts in fours or fives
Leaves with distinct vein network
Vascular cambium present
Vascular bundles in ring
Pollen grain with three apertures
Monocots
One cotyledon
Flower parts in threes
Leaves with parallel primary veins.
Vascular cambium absent
Vascular bundles scattered
Pollen grain with one aperture
Structure of Flowers
Each flower, which begins as an embryonic primordium that develops into a bud, occurs as a specialized branch at the tip of a peduncle which may have branchlets of pedicles.
Pedicle swells at its tip into a small pad (receptacle).
Other parts of the flower are attached to the receptacle.
Structure of Flowers
Outermost whorl typically consists of three to five sepals.
Sepals (calyx) may be fused together.
Next whorl consists of three to many petals (corolla).
Calyx and corolla form the perianth.
Structure of Flowers
Several to many stamens are attached to the receptacle around the base of the pistil.
Each stamen consists of a filament with an anther at the top.
Pollen grains developed and disseminated in anthers.
Structure of Flowers
Pistil consists of Stigma, Style, and Ovary.
Superior Ovary - Calyx and corolla are attached to the receptacle at the base of the ovary.
Inferior Ovary - Receptacle grows up and around the ovary.
Calyx and corolla appear to be attached at the top.
Inflorescences - Group of several to hundreds of flowers.
Fruits
Fruit is an ovary and its accessory parts that have developed and matured.
Usually contains seeds.
All fruits develop from flower ovaries and accordingly are found exclusively in flowering plants.
Fruits
Fruit Regions
Exocarp - Skin
Endocarp - Inner boundary around seed(s).
Mesocarp - Fleshy tissue between exocarp and endocarp.
Three regions are collectively called the pericarp.
Fruits
Dry Fruits That Split at Maturity (Dehiscent)
Follicle - Splits along one side or seam.
Legume - Splits along two sides or seams.
Silique - Splits along two sides or seams, but seeds are borne on central partition exposed when the two halves separate.
Capsules - Consist of at least two carpels, and split in a variety of ways.
Fruits
Aggregate Fruits
Derived from a single flower with several to many pistils.
Individual pistils mature as a clustered unit on a single receptacle
Raspberries, Strawberries.
Multiple Fruits
Derived from several to many individual flowers in a single inflorescence.
Pineapples, Figs
Fruit and Seed Dispersal
Wind Dispersal
Small and Lightweight seeds.
Animal Dispersal
Seeds pass through digestive tract.
Fruits and seeds catch in fur or feathers.
Oils attract ants.
Water Dispersal
Some fruits contain trapped air.
Mechanical Ejection of Seeds
Seeds
Structure
Cotyledons - Food storage organs that function as first seed leaves.
Plumule - Embryo shoot.
Epicotyl - Stem above cotyledon.
Hypocotyl - Stem below attachment point.
Radicle - Stem tip developing into a root.
Germination
Germination is the beginning or resumption of seed growth.
Seed must be viable.
Some require period of dormancy.
Scarification
After Ripening
Favorable Environmental Factors
Imbibe water
Longevity
Viability of most seeds is significantly extended when the seeds are stored under conditions of low temperatures and kept dry.
A few species produce seeds with no period of dormancy.
Vivipary
Review
Dicots versus Monocots
Structure of Flowers
Fruits
Fleshy
Dry
Fruit and Seed Dispersal
Seeds
Germination
Longevity
Outline
Origin of Cultivated plants
Ranunculaceae Family
Lauraceae Family
Papaveraceae Family
Brassicaceae Family
Rosaceae Family
Fabaceae Family
Euphorbiaceae Family
Cactaceae Family
Lamiaceae Family
Solanaceae Family
Apiaceae Family
Cucurbitaceae Family
Asteraceae Family
Poaceae Family
Liliaceae Family
Orchidaceae Family
Origin of Cultivated Plants
Cultivated Plants appear to have originated in six major regions:
Chinese Region
African Continent
South Asia and Pacific Islands
North America
South and Central America
Ranunculaceae Family
Buttercups
Nearly all 1,500 member species are herbaceous.
Most members are at least slightly poisonous.
Papaveraceae Family
Most member species are herbs distributed throughout the temperate and subtropical regions north of the equator.
Opium Poppies
Morphine and Codeine
Heroin
Papaverine and and Noscapine
Brassicaceae Family
Four flower petals are arranged in a cross.
Nearly all 2,500 species are herbs distributed primarily throughout the temperate and cooler regions of North America.
Many cultivated edible plants.
Cabbage, Cauliflower, Brussels Sprouts, Broccoli, Radish, Turnip, Horseradish, Watercress, and Rutabaga.
Rosaceae Family
Rose Family
Includes more than 3,000 species.
Family is subdivided into subfamilies on the basis of flower structure and fruits.
Enormous economic impact.
Garden Ornamentals
Fragrances
Hips
Vitamin C
Fabaceae Family
Legume Family
Third largest of flowering plant families.
13,000 members.
Many important crop plants.
Peas
Beans
Peanuts
Alfalfa
Carob
Euphorbiaceae Family
Spurge Family
Widespread in temperature regions both north and south of the equator.
Several economically important plants.
Cassava
Para Rubber Tree
Cactaceae Family
The Cactus Family
Potentially more than 1,500 species.
Most occur in dry, subtropical regions.
Usually showy flowers.
Most have edible fruit.
Lamiaceae Family
Mint Family
Easy to distinguish because of a unique combination of angular stems that are square in cross section, opposite leaves, and bilaterally symmetrical flowers.
Mint oils have been used medicinally and as an antiseptic in different parts of the world.
Menthol
Liliaceae Family
Lily Family
Approximately 4,550 members.
Occur in almost any area supporting vegetation.
Asparagus
Sarsaparilla
Meadow Saffron (colchicine)
Aloe
Onions and Garlic
