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Botany Exam 3


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Parts of a Flower
Sepals (calyx)
Petals (corolla)
Stamens (androecium)
Carpels (gynoecium)
Parts of a Carpel
Stigma: receives pollen
Style: where pollen tubes grow
Ovary: contains ovules
Monoecious vs. Dioecious
Monoecious: both male and female flowers on the same plant
Dioecious: separate plants for male and femals
Position of Ovary:

Hypogynous flower
No fusion between petals, sepals, and stamens.
Perianth and stamens are attached to the receptacle below the ovary which sits on top.
Position of Ovary:

Perigynous flower
Fusion of petals, sepals, and stamens into a cup-shaped extension of receptacle.
Superior ovary
Position of Ovary:

Epigynous flower
Petals, sepals, and stamens are attached above the ovary.
Inferior ovary, enclosed within the receptacle.
Double Fertilization
Both sperm cells of the mature sperm gamteophyte (microgametophyte) join with the mature embryo sac (megagametophyte). One with the egg and the other with the polar nuclei. Results in fertilization and triple fusion.
Triple Fusion
Fusion of one of the sperm nuclei with the two polar nuclei results in a triploid endosperm nucleus
5 Major Groups of Hormones
Abscisic acid
Cues for Seed Germination
Seed scarification
Cold/Hot temperature
Exposure to light
Three Steps to Seed Germination
Imbibition: uptake of water by the seed
Seed swells
Activates production of enzymes and proteins and use of the endosperm

Cause phototropism and gravitropism.
Carrier proteins move to one side while auxin promotes growth on the said which causes benging in the other direction.
Inhibit leaf abscission.
Apical dominance (produced at tip).
Initiating root growth.
Promoting stem elongation.
Controlling fruit development.

Produced at roots.
Inhibits stem elongation.
Stimulates lateral bud growth.
Regulates leaf expansion and delay leaf senescence.
Can cause light requiring seeds to germinate in the dark (rapd cell division).

Promotes leaf abscission.
Speeds ripening of fruit.
Positive feedback to speed its own production.

Abscisic Acid (ABA)
"Stress Hormone"
Keeps seed dormant (inhibits germination).
Stomatal aperture regulation.
Inhibits stem elongation.

Normal stem elongation.
Fruit growth, even from unpollinated flowers.
Bring spring buds out of winter dormancy.
Break seed dormancy.
Bolting (increase in cell number and elongation).
External Growth Factors
Gravitropism: amyloplasts will accumulate at the bottom of the cell and signal that it is "bottom"
Thigmotropism: growth in response to touch, tendrils, or roots around rocks
Circadian Rhythms
Some plants shut flowers down at night.
Entrainment: response to variations in day length.
Photoperiodism: response
Nastic Movements
Thigmonasty: movement in response to touch
Heliotropism: tracks the sun, changes direction throughout the day

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