Flowers, Seeds and Fruits
The major function of flowers is reproduction of the plant.


Flower Diagram- labeled
I. Functions of flower parts:
   A. Stamen- male reproductive structure
         1. Anther- produces the pollen 
                Pollen production- diagram
         2. Filament- supports the anther

   B. Pistil (Carpel) - female reproductive structure
        1. Stigma- sticky structure for capturing pollen
        2. Style- tube which connect stigma to ovary
        3. Ovary- contains one or more ovules, which have one egg cell
              a. ovules- contain an egg cell and the 2 polar nuclei within an embryo sac
              b. integument- outer covering of the ovule

   C. Sepals- enclose the flower before it opens; usually green; collectively the sepals are referred to as the calyx; located on the lowest portion of the receptacle.
   D. Petals- aid in attracting insects and other pollinators; usually brightly colored; collectively the petals are referred to as the corolla.
                   
   E. Receptacle- terminal portion of a branch leading to the flower

II. Pollination- transfer of pollen from the anther to the stigma
                    Pollination slide show
                    Pollination diagram
   A. Cross-pollination- transfer of pollen from the anther of one plant to the stigma of a different plant
   B. Self-pollination- transfer of pollen from the anther of one flower to the stigma of another flower on the same plant.
       1. Most flowers cross-pollinate.  Few rely on self-pollination. Cross-pollination increases genetic variability, which increases a population's chances of survival.
       2. Some flowers have mechanisms that prevent self-pollination.  These may include having the stamens and pistils mature at different times, or having them (stamens and pistils) arranged within the flower so that self-pollination is unlikely.
   C. Pollination mechanisms
       1. wind
       2. water
       3. animals (bees, flies, butterflies, moths, birds, mammals)

III. Pollination and Double Fertilization
   A. Pollen grain forms the "pollen tube" which grows down the style of the pistil.
   B. When the pollen tube reaches the ovary, it penetrates the integuments of an ovule and two sperm cells are released into the embryo sac.  Diagram of pollen tube reaching ovule.
   C. One sperm fertilizes (fuses with) the  egg cell, forming a zygote.
   D. The other sperm fuses with the 2 polar nuclei in the center, becoming a triploid cell (3n).

IV. After Fertilization
   A. The fertilized egg becomes the zygote and continues to develop into a plant embryo
   B. The triploid cell becomes the endosperm, a food source for the developing plant.   Dicots usually convert their food reserves to cotyledons, whereas monocots keep their food reserves in mostly as endosperm.
   C. The ovule forms a seed.
   D. The integuments form a seed coat
   E. The ovary becomes a fruit.
   F. Note- Some flower ovaries have only one ovule, so their fruits will have only one seed.  Flower ovaries with may ovules will produce fruits with many seeds.

V. Seeds
    A. Seed structure (Dicot)  (Monocot)
        1. Cotyledon-
             a. acts as a food source for the developing embryo until the new leaves develop;
             b. sometimes called embryonic leaves
             c. develops from endosperm
        2. Embryo
             a. radical- portion of embryo that develops into the root; first part to develop
             b. hypocotyl- portion of embryo that develops into the upper root/lower stem
             c. epicotyl- portion of the embryo that develops into the upper stem and first true leaves
       3. Seed coat- surrounds and protects the seed.
    B. Seed Germination
       1. First to develop are the roots, from the radical, to absorb water and nutrients for the plant.
       2. Next to develop is the lower stem, from the hypocotyl.
       3. Last to develop are the upper stem and leaves, from the epicotyl.
       4. Once the first true leaves appear, the cotyledons will wither, as the leaves take over food production duties.
     C. Comparison of monocot and dicot germination
    

VI. Fruits    (Types of Fruits)
    A. Function- dispersal of seeds
    B. Type of fruit is determined by how it is intended to be dispersed
    C. Examples:
        1. Maple trees produce fruits that are sometimes called "helicopters", which are designed to be dispersed by wind.  Fruits of dandelion flowers are also designed to be dispersed by wind.
        2. Fruits with burrs are designed to attach to animal fur, so they can be carried away.
        3. Most fleshy fruits are designed to be eaten by animals.  However, the seeds pass unharmed through their digestive tract, and are deposited much later and usually at a great distance from where they originated.

VII. Other resources:
Basic concepts of flowers and fruits- includes more detail, as well as information on types of fruits
Notes: seeds and germination- includes more detail, especially regarding the chemical changes involved
Notes: flower to fruit- includes more detail, especially regarding functions and types of fruits