Biology – 328 Lab Biology – 328 Lab Plants and Plants and People People

ObjectiveObjectiveUnderstanding origin of flowers, its

morphology and anatomy

To study flowers based on◦ Types of pollination◦ Presence of floral whorls◦ Presence of sexes◦ Line of symmetry◦ Sexual expression◦ Position of ovary

To study different types of inflorescences

BackgroundBackground

Origin – Modified shoot

Floral Morphologyo Calyx (sepals)o Corolla (petals) - 3’s in monocots and 4’s or 5’s in dicots)

o Perianth (calyx + corolla)o Gynoecium (pistil- stigma, style, ovary)

o Androecium (stamen- anther, filament)

o Receptacle

Floral anatomyFloral anatomyLocules – Open space inside ovary

Carpels – Basic developmental unit◦Apocarpous (carpels not fused) ◦Syncarpous (carpels fused)

Pistil ◦ Simple – Unicarpellate (1 carpel)◦ Compound – Syncarpellate (2 or more carpels FUSED)

Types of flowersTypes of flowersBased on pollination

◦ Entomophily (insect)◦ Anemophily (wind)

Based on presence of floral whorls◦ Complete flower - All 4 floral whorls

present ◦ Incomplete – Not all 4 floral whorls present

Based on presence of sexes◦ Perfect – Both sexes present◦ Imperfect – Not both sexes present

Based on line of symmetry◦ Actinomorphic (regular)– more than one

plane of symmetry◦ Zygomorphic (irregular)– One plane of

symmetry

Based on sexual expression ◦ Monoecious – “One house” (male and

female part present in the same flower in the same plant or different flowers in the same plant)

◦ Dioecious – “Two house” (male and female flowers in different flowers in different plants

Based on ovary position◦ Hypogynous (superior ovary) – Floral

whorls arranged below (=hypo) ovary (=gynous)

◦ Epigynous (Inferior ovary) – Floral whorls arranged above (epi) ovary (=gynous)

◦ Perigynous (superior ovary) – Floral whorls arranged around (=peri) overy (=gynous). Presence of well developed HYPANTHIUM (cup) made of receptacle and bases of sepals, petals and stamen

Types of inflorescencesTypes of inflorescencesRaceme – Unbranched inflo. with pedicel

and indeterminate (young flowers on top).Eg. Orchid, Milkwort

Spike – Same as receme but no pedicel (sessile flowers)Eg. Gladious, Hyacinth

Catkin/Ament - Same as spike, but unisexual Eg. Oak, Pecan, Birch, hickory, willow

Umbel – All pedicels arise from a common pointEg. Onion, Garlic

Compound Umbel – Group of umbels whose peduncles arise from same pointEg. All members of Apiaceae (carrot family)

Panicle – Inflorescence which branches and rebranches. For eg. Yucca, Lilac, Wisteria

Head/Capitulum – Dense arrangement of sessile flowers on a common receptacleEg. Sunflower, Daisy, Aster, Thistle

Today’s LabToday’s Lab• Carefully EXAMINE all floral material provided using the

following exercise and questions as a guideline.  To gain an ultimate familiarity with floral morphology, compare the material against descriptions and definitions in your lecture notes or textbook.  Become familiar with cross and long sections.

• 1.  Flowers are arranged in groups called inflorescences.  We will examine some inflorescences particular to certain families later in the semester.  For now, know what an inflorescence is and which one we looked at today.

• 2.  DRAW a longitudinal section of a typical flower labeling the following parts:  receptacle, calyx, sepals, corolla, petals, perianth, pedicel, ovary, ovule, style, stigma, pistil, gynoecium, anther, filament, stamen, and androecium.

Today’s LabToday’s Lab• 3.  EXAMINE by dissection the floral material provided making

long and cross sections of the flower and its parts.  On a separate sheet of paper, SKETCH the flowers and label the parts.  Then, FOR EACH FLOWER, answer the following questions:

• Is the flower actinomorphic (regular) or zygomorphic (irregular)? • How many sepals are present?  Petals?  Stamens?  Carpels?  To

count carpels, count the style branches and/or count the zones of placentation by cross- sectioning the ovary.

• Is the ovary inferior or superior? • Is the flower from a monocotyledonous or dicotyledonous plant? • Is the flower perfect (both sexes present) or imperfect?  Complete

(all four floral whorls) or incomplete?

SummarySummary

Today’s Lab Floral Origin, morphology and

anatomy Different types of flowers and

inflorescence

Next week’s lab – Fruits Quiz on Flowers