Flower, Fruits and Seed

• Flower

  the sporophytic structure of angiosperms specialized for sexual reproduction

  a modified reproductive shoot

  Flowers are determinate shoots; they cease growing after the flower and fruit are formed.
• Typically composed of four types of floral organs: carpels, stamens, petals, and sepals that take the form of concentric whorls when viewed from above.

  Flower structure
• When viewed from above, these organs take the form of concentric whorls: Carpels form the first (innermost) whorl, stamens the second, petals the third, and sepals the fourth (outermost) whorl.
• All are attached to a part of the stem called the receptacle.
• Pedicel - the flower stalk, may be absent in sessile flowers
• Bract - subtend flowers, modified, generally reduced leaf
• Receptacle - tissue or region of a flower to which the other floral parts are attached.
• Perianth – perigonium, outermost, nonreproductive group of modified leaves of a flower
• Tepals - If the perianth is relatively undifferentiated, or if its components intergrade in form
• Calyx - outermost series or whorl of modified leaves. Individual units: sepals, typically green, leaflike, and function to protect the young flower
• Corolla - innermost series or whorl of modified leaves in the perianth. Individual units: petals, which are typically colored (nongreen) and function as an attractant for pollination
• Hypanthium - floral tube, a cuplike or tubular structure, around or atop the ovary, bearing along its margin the sepals, petals, and stamens
• Nectary - specialized structure that secretes nectar
• Androecium - refers to all of the male organs of a flower
• Stamen - a microsporophyll, which characteristically bears two thecae (each theca comprising a pair of microsporangia). Consists of a stalk called the filament and a terminal structure called the anther, within the anther are chambers called microsporangia (pollen sacs) that produce pollen.
• Anther - discrete pollen containing units, found in the stamens of the great majority of angiosperms. The tissue between and interconnecting the two thecae is termed the connective, to which the filament (if present) is attached.
• Microsporangia are the sites of production of pollen grains, the immature male gametophytes of seed plants.
• Gynoecium - refers to all of the female organs of a flower
• Carpel - modified, typically conduplicate megasporophyll that encloses one or more ovules
• A carpel (megasporophyll) has an ovary at its base and a long, slender neck called the style. At the top of the style is a sticky structure called the stigma that captures pollen. Within the ovary are one or more ovules, which become seeds if fertilized; the number of ovules depends on the species.
• Complete flowers have all four basic floral organ
• Some species have incomplete flowers, lacking sepals, petals, stamens, or carpels.
• STAMINATE with only stamens (male flowers) Sagittaria cuneata
• CARPELLATE with only carpels (female flowers) Luffa
• no petals - Thalictrum thalictroides

  
• floral symmetry ► presence and number of mirror-image planes of symmetry. Can be an important adaptation relative to pollination systems
• ACTINOMORPHIC radial symmetry, more than one dividing plane.

  
• ZYGOMORPHIC bilateral, one bilateral dividing plane

  
• ASYMMETRIC - lacks any plane of symmetry, usually the result of twisting parts

  
• flower inflorescence

  ► a collection or aggregation of flowers on an individual plant

  ► often enhance reproduction
• involucre/ inflorescence bract group or cluster of bracts subtending an entire inflorescence
• identify

  A) flower

  B) pecundle

  C) inflorescence bract

  
• DETERMINATE - first flower to open is at the top or middle, cymes
• INDETERMINATE first flowers to open are at the base, spikes, racemes, panicles.
• floral diagram ► represent a diagrammatic cross-sectional view of a flower bud, showing the relative relationship of perianth, androecial, and gynoecial components
• placentation ► refers to the positioning of the ovules and takes into account the number and position of placentae, septa, and locules
• flower development ► Flower formation involves a phase change from vegetative growth to reproductive growth. — Triggered by a combination of environmental cues and internal signals
• identify

  A) placenta

  B) septa

  C) locule

  D) ovule

  
• AXILE - placentae arising from the column in a compound ovary with septa

  
• APICAL - placenta at the top of the ovary