Structure, Transport, Reproduction and Hormones Botany Structure, Transport, Reproduction and Hormones

Structure- plants can be divided up into organs Shoot- grows above the ground Leaf- used for photosynthesis and gas exchange defense (spines on a cactus) storage (the layers on an onion) support (tendrils on a vine) Stem- used for transport -used for support Male and female reproductive organs Roots- grows below the ground used to absorb water and minerals used for support (adventitious roots) used for storage (carrots and yams)

Leaves can be modified Water plant leaves can be larger as they do not need as much support Evergreens and conifers leaves are shaped like needles to conserve water The structure connecting the blade to the stem is the petiole. The wide part of the leaf is the blade. A leaf that only has one blade is a simple leaf. A leaf that has several blades is a compound leaf.

Cross section of a leaf

Stomates: Transpiration- water loss in plants Gas exchange- carbon dioxide and oxygen

Transport An overview of the path of water and nutrients Transport system: Xylem- movement up Dead at maturity Phloem- movement up and down Is alive!

Veins in plants: Xylem and phloem tissue form the vascular bundles. These bundles are called VEINS. The veins in a leaf branch out extensively so that the xylem and phloem are close to the mesophyll cells. Parallel veins- monocots Branched veins- dicots The conducting tissues found in the leaf are continuous with those in the stem and root. (cross section of stem )

Movement of water: T.A.C.T Theory Tension- water molecules attracted to one another. Creates tension in a column of water. Surface tension- how insects stand on water Adhesion- water molecules are attracted to cellulose walls Cohesion- water molecules attracted to one another because of hydrogen bonds. Transpiration- water loss through the stomate due to water potential.

Roots:

Reproduction 1. Sepal-leaf like and protects the floral bud. 2. Petals-Usually showy with colors to attract pollinators 3. Stamen-male reproductive organ. Contains an anther where male gametophytes or pollen is produced. The anther sits on a long stalk called the filament which connects to the base of flower 4. Carpel-female reproductive organ. The swollen bottom or ovary contains one or more ovules where the female gametophyte is found. The ovary connects to a slender structure called the style. At the top of the style is the stigma where the pollen lands. Flowers can have multiple carpels or only one.

Pollen is species specific

Hormones Hormone- is a control chemical produced in a regular fashion by tissues or organs specialized for that function and exerting their highly specific effects on other tissues of that body. Plant Hormones- produced mostly in areas of growth: apical meristem, roots, young leaves, developing seeds or fruits Tissues that produce plant hormones are not as specialized as animal tissues that produce hormones. No hormone producing organs Used in regulating growth and development (Animal hormones can regulate other processes).

Plant Hormones

Tropism- directional growth in response to stimuli Phototropism- Plants are positive phototropic. They grow toward the light. Gravitropism-the shoots of plants grow away from gravity (negative gravitropism) and roots grow toward gravity (positive gravitropism) even if the plant is laid on its side.

Phototropism of the coleoptile plant:

Thigmotropism:

Fruit development: Fruit formation-If pollination and fertilization of a flower does not occur, the flower will wither and a weak layer of cells will develop. The flower will then fall off. If the flower is fertilized, then the pollen will release auxin which will stimulate the ovary or receptacle to grow and form fruit. As the embryo inside the seed, develops it will continue secreting auxins to continue the fruit development.

Ethylene-Is a simple gas *promote fruit ripening *promote leaf abscission (dropping of leaves) *promote senescence (aging) *break dormancy in buds & seed in some species in some plants