1. Chapter 28 Reproduction in Plants

2. Figure 28.1

3. Life Cycle of Flowering Plants
In contrast to animals with one type of adult generation, flowering plants exhibit an alternation of generations
includes a diploid & a haploid generation.
Sporophyte is diploid generation
Sporophyte produces haploid spores (meiosis)
Spores develop into a haploid gametophyte.
Gametophyte is haploid generation
Gametophyte produces haploid gametes (mitosis) gametes fuse to form diploid zygote.
Zygote develop into the sporophyte.

4. Sporophyte-Flower
A flower is the reproductive organ of a flowering plant; it develops within a bud.
Shoot apical meristem stops forming leaves to form flowers; axillary buds can become flowers directly.
Flower structures are modified leaves attached to a stem tip (receptacle)
Monocot flower parts = 3’s or multiples
Dicot flower parts = 4’s, 5’s or multiples

7. Sporophyte-Flower
Not all flowers have sepals, petals, stamens, and a pistil.
Complete flowers have sepals, petals, stamens, and a pistil; incomplete flowers do not.
Perfect flowers have both stamens and a pistil.
Staminate flowers have only stamens.
Pistillate flowers have only pistils.
Monoecious - If staminate and pistillate flowers are on same plant
Dioecious - If staminate and pistillate flowers are on different plants

8. Life Cycle of a Flowering Plant
Floral Structure & Function
Egg/Pollen Fertilization

9. Animation – Double Fertilization
Figure 28.5
Animation – Double Fertilization

14. Pollination Pollination and fertilization are separate events.
Pollination is strictly transfer of pollen from anther to stigma of a pistil.
Pollination occurs by wind or with assistance of particular animal pollinators.
Self-pollination is transfer of pollen from anther to stigma of the same plant.
Cross pollination is transfer of pollen from anther of one plant to stigma of another plant; it is evolutionarily advantageous because of genetic recombination resulting in new and varied plants.

16. Fertilization
Pollen tube grows through micropyle and releases both sperm cells into the ovule.
sperm nucleus + the egg nucleus = 2n zygote
sperm nucleus + 2 polar nuclei = 3n endosperm nucleus.
This is double fertilization
Zygote divides mitotically to become the embryo; endosperm nucleus divides mitotically to become endosperm
Embryo - is a young sporophyte.
Endosperm - tissue that will nourish embryo and seedling as they undergo development.

22. Animation

23. Embryonic Development
Embryo continues to differentiate into three parts.
Epicotyl between cotyledons & 1st leaves; it contributes to shoot development
Hypocotyl is below cotyledon and contributes to stem development
Radicle is below hypocotyl and contributes to root development

24. Monocot embryo = one cotyledon Dicot embryo = two cotyledons
cotyledon rarely stores food; rather, it absorbs food molecules from endosperm and passes them to embryo.
After differentiation into embryo and suspensor, one or two cotyledons develop.
Cotyledon (seed leaf) provides nutrient for a developing plant before it photosynthesizes.
Dicot embryo = two cotyledons
cotyledons usually store nutrients the embryo uses, obtaining those nutrients from endosperm.

25. Seeds and Fruits
As a zygote develops into embryo, integuments of the ovule harden and become seed coat.
Ovule matures into the seed
sporophyte embryo
stored food
Ovary (and sometimes other floral parts) develops into fruit (mature ovary that usually contains seeds).

26. Seed Dispersal
For plants to be widely distributed, seeds have to be dispersed away from parent plant.
Hooks, spines & bur attach to fur of animals
Birds & mammals eat fruits & defecate them
Squirrels gather seeds & bury them
Dispersal by water
Dispersal by wind
Touch-me-nots & Oxalis has seed pods burst

27. Animations
Germination in Dicots & Monocots

28. Germination in Dicots
Prior to germination, embryo consists of the following:
2 Cotyledons - supply nutrients to embryo & seedling; soon shrivels and disappears
Plumule—epicotyl bearing young leaves
Hypocotyl - which becomes the stem
Radicle - which develops into roots.
As dicot seedling emerges, the shoot is hook-shaped to protect delicate plumule.
As seed germinates in darkness, it etiolates (stem length increases; leaves remain small)
Phytochrome pigment = red and far-red light induces normal growth in light.

31. Germination in Monocots
Endosperm is food-storage tissue; cotyledon does not have a storage role.
Monocot “seed” is actually the fruit; outer covering is the pericarp.
Prior to germination, embryo consists of one cotyledon, a plumule, and a radicle.
Plumule and radicle are enclosed in protective sheaths: coleoptile and coleorhiza, respectively.
Plumule and radicle burst through these coverings when germination occurs.

34. Plants:Asexual Reproduction
Plants contain nondifferentiated meristem tissue and reproduce asexually by vegetative propagation.
In asexual reproduction, offspring arise from a single parent and inherit genome of that parent only.
Vegetative propagation utilizes meristematic tissue of a parent plant.
Nodes of stolons will produce strawberry plants.
Eyes of a potato plant tuber is a bud;produces new plant
Sweet potatoes can be propagated from modified roots.
Many trees can be started from small “suckers.”
Discovery that auxin will cause roots to develop has expanded ability to use stem cuttings.