Plant Flowers Flashcards

Plant Flowers

  • A flower is a modified shoot specialized for reproduction.
  • It consists of a short axis (thalamus) with nodes, condensed internodes, and four whorls of floral leaves.
  • Flowers arise from terminal or axillary flower buds.

Parts of Flowers

  • Four floral whorls (base to top): Calyx, Corolla, Androecium, and Gynoecium/Pistil.
  • Complete flowers have all four whorls; incomplete flowers lack one or more.
  • Calyx and corolla are non-essential; androecium and gynoecium are essential for reproduction.
  • Cyclic arrangement: floral organs arranged in distinct strata.
  • Acyclic arrangement: floral organs arranged in a spiral manner.
  • Hemicyclic/spirocyclic: floral parts partly cyclic, partly acyclic.

Classification of Flowers

  • Bisexual (hermaphroditic): have both androecium and gynoecium.
  • Unisexual: have either androecium (male/staminate) or gynoecium (female/pistillate).
  • Monochlamydeous: have essential whorls and one non-essential whorl.
  • Polygamous plants: bear both unisexual and bisexual flowers.
  • Monogamous plants: have unisexual flowers.
  • Monoecious plants: have both staminate and pistillate flowers.
  • Dioecious plants: have only male or female flowers.
  • Regular flowers: uniform size and shape in each whorl.
  • Irregular flowers: unequal size in each whorl.
  • Actinomorphic flowers: divisible into similar halves along any vertical plane; complete and regular flowers are always actinomorphic
  • Zygomorphic flowers: divisible into two similar halves along one particular plane; irregular.
  • Symmetrical flowers: actinomorphic and zygomorphic flowers.
  • Asymmetric flowers: cannot be divided into equal halves in any plane.

Parts of Flowers - Calyx

  • Outermost whorl, units are sepals.
  • Typically green, can produce food through photosynthesis.
  • Regular calyx: sepals are same size; irregular calyx: sepals have different sizes.
  • Gamosepalous: fused sepals; polysepalous: free sepals.
  • Pappus: hairy sepals.
  • Spurred: one sepal forms a tubular structure.
  • Petaloid: brightly colored calyx.
  • Spinous: sepals modified into spines.
  • Hooked: one sepal modified into hook-like structure.
  • Caducous: falls off soon after flower opening.
  • Deciduous: falls off with petals.
  • Persistent: remains on the fruit.
  • Accrescent calyx grows as a jacket around the fruit.
  • Marcescent: no growth after fertilization.
  • Tubular: sepals appear tube-like.
  • Infundibuliform: sepals appear funnel-like.
  • Urceolate: sepals appear urn-shaped-like.
  • Bilabiate: consists of two lips.
  • Campanulate: sepals appear bell-shaped.
  • Cupulate: sepals appear cup-like.

Parts of Flowers - Corolla

  • Set of petals, often thin, delicate, brightly colored, and sweet-smelling.
  • Sepaloid: thick, succulent, green petals.
  • Dichlamydeous: has both calyx and corolla.
  • Monochlamydeous: single whorl of perianth.
  • Perianth: when calyx and corolla are indistinguishable.
  • Polypetalous corolla: free petals with claw (stalk-like lower portion) and limb (upper expanded portion).
  • Gamopetalous corolla: fused petals, with tube (lower portion) and limb (upper portion).
  • Apetalous flowers: lack corolla.
  • Coronal outgrowth/corona: outgrowths or appendages for attraction.
  • Regular corolla: uniform sized and shaped petals.
  • Irregular corolla: different sized and shaped petals.
  • Gamopetalous: fused petals; polypetalous: free petals.
  • Types of Polypetalous and regular corolla:
    • Cruciform: four free and clawed petals.
    • Rosaceous: five spreading lobes, not clawed.
    • Caryophyllous: four free clawed petals with spreading lobes.
  • Polypetalous and irregular corolla
    • Papilionaceous - has five free and unequal petals
  • Gamopetalous and regular flowers:
    • Tubular: petals appear tube-like.
    • Campanulate (bell-shaped): petals form bell shape.
    • Infundibuliform (funnel-shaped): petals form funnel shape.
    • Rotate (wheel-shaped): petals form wheel-like shape.
    • Hypocrate (salver-shaped): petals form a narrow tube with limbs at right angle.
  • Gamopetalous and Irregular Corolla:
    • Ligulate: petals form a short tube and bears tongue shaped lobes.
    • Bilabiate (two-lipped): petals have two projecting lips, the upper lip has two petals and the lower lip with three petals (throat always open).
    • Personate: lips are so close together the throat is always closed.

Aestivation

  • Arrangement of sepals and petals in bud condition.
  • Valvate: adjacent petals/sepals touch without overlaps.
    • Valvate induplicate: margins of the petals are folded inwards
  • Contorted/twisted: petals/sepals overlap such that each overlaps the next.
  • Imbricate: one sepal/petal is completely outside, another is completely inside, and the rest are partly inside/outside.
    • Imbricate descending (vexillary): Posterior petal is completely outside and the anterior is completely inside
    • Imbricate ascending: the posterior petal is completely inside and the anterior petal is complete outside
  • Quincuncial: five units, two completely exterior, two completely interior, one partially interior/exterior.
  • Induplicate-convolute: combination of twisted and induplicate types; narrow tubular lower and a broad spreading circular upper portions.

Parts of Flowers - Androecium

  • Third whorl of the flower, male reproductive part.
  • Stamen: anther (pollen production in microsporangia) and filament (stalk).
  • Anther: bilobed knob with connective tissue; contains two lobes and four chambers (dithecus).
  • Thecae consist of microspores; anther is tetramicrosporagiate due to four microsporangium.
  • Epidermis: outer lining that protects the anther.
  • Archaesporial cells:
    • Large cells with dense cytoplasm, hypodermal.
    • Undergo periclinal division into primary parietal cells and inner primary sporogenous cells.
    • Parietal cells (protect inner sporogenous cells) further divide to form differentiated layers of cells
    • Outer endothecium – monolayer of flattened cells
    • Middle layer – has 1-3 layers of parenchymatous cells
    • Inner tapetum – nutritive layer to the growing sporogenous cells
  • Bilobed anther: occurs in mature stamens of angiosperms
  • Unilocular anther: occur by destruction of connective tissue, lobe, or longitudinal grooves.
  • Attachment to filament:
    • Adnate: anther is in continuation with the filament.
    • Innate/basifixed: filament attached to the basal region.
    • Dorsifixed: filament attached to the dorsal/back side.
    • Versatile: anther attached to the middle of the filament.
  • Anthesis: anther dangles out of the flower.
  • Dehiscence: anther bursts and discharges pollen grains during anthesis.
  • Based on the direction of dehiscence, anther releases pollen either transversal, longitudinal, poricidal or valvular

Parts of Flowers - Gynoecium

  • Innermost whorl, made of carpels, female reproductive part (produces fruit after fertilization).
  • Composed of stigma, style, and ovary.
  • Stigma: top sticky part of carpel (receives pollen).
  • Style: tube through which sperm cells reach the ovary.
  • Ovary: fertilization occurs here, produces eggs, has ovary wall and ovules.
  • Monocarpous/unicarpellate: single carpel.
  • Apocarpous/chloricarpous: multiple distinct carpels.
  • Syncarpous: multiple fused carpels.
  • Ovary types:
    • Superior: attached on the receptacle above other floral parts.
    • Perigynous: surrounded by receptacles.
    • Inferior: lies below the attachment of floral parts (epigynous).