Chapter 25 - Plant Reproduction
I. Sexual Reproduction in Seedless Plants
A. Non-vascular plants (ex. moss)
1. Gametophyte generation is larger than sporophyte
2. Gametophyte has separate male (sperm producing) and female (egg producing) structures
a) Archegonium - produces eggs
b) Antheridium - produces sperm
c) Sexual reproduction requires water to allow sperm to swim to the egg, therefore these plants do not thrive away from water, some species must wait for a covering of water from rain or flooding to reproduce
3. Sporophyte (smaller than gametophyte) - produces spores in the sporangium
B. Seedless Vascular Plants (ex. fern)
1. Sporophyte is larger than the gametophyte
a) Spores are produced in the sporangia
b) Sorus - cluster of sporangia found on the lower side of the fronds
2. Gametophyte (smaller than sporophyte)
a) Archegonium - produces eggs
b) Antheridium - produces sperm
c) Requires water for fertilization
II. Sexual Reproduction in Seed Plants
A. Tiny gametophytes (made of only a few cells) are male or female
1. Male gametophyte becomes a grain of pollen
2. Female gametophyte becomes an ovule
3. After fertilization the ovule develops into the seeds
a) Pollination - transfer of sperm to the egg
b) Pollen tube - develops during pollination, allows sperm to pass directly to the egg
B. Pollinators (ex. bats, birds, bees & other insects)
1. Attracted by the bright colors, sugary nectar, strong odors, or bold shape of the flowers
2. Symbiotic relationship (animals get food, plants get pollen distributed)
3. Most flowers use animal pollinators, those that use the wind tend to lack the bright colors, nectar, odors, etc.
C. Seeds = plant embryo (develops into sporophyte)
1. Seed coat - protective outer layer of the seed, protects from mechanical injury, allows for delayed growth of embryo until favorable conditions are met
2. Endosperm - nutritious tissue for the embryo
3. Cotyledons - “seed leaves” transfer nutrients from the endosperm to the embryo
D. Cones
1. Found in gymnosperms (ex. conifers)
2. Consist of circles of scales
3. May be male or female in nature
4. Male and female cones are often found on the same tree
a) Seed cones (female)
b) Pollen cones (male)
5. Pollen is carried on the wind from the pollen cones to the (open) seed cones, seed cones will close after pollination
E. Flowers
1. Found in angiosperms (ex. daisy, magnolia)
2. Four basic parts
a) Sepals - outermost layer, protects the bud
b) Petals - second layer, attracts pollinators
c) Stamens - found inside the petals, consists of the thread-like filament, and a pollen producing sac called an anther
d) Pistil - innermost layer, produces ovules within the enlarged lower portion called the ovary
3. Complete flowers - have all four parts (sepals, petals, stamens, & pistils)
4. Incomplete flowers - lack one of the four parts
5. Perfect flowers - have both stamens and pistil
6. Imperfect flowers - have either stamens or a pistil
III. Asexual Reproduction
A. Also called vegetative reproduction
B. Offspring are genetically identical to the parent
C. Faster than sexual reproduction
D. Structures involved may include stems, roots, and leaves
1. Runners - horizontal above ground stem
2. Bulbs - short underground stems of monocots with fleshy leaves
3. Corm - short underground stems of monocots with scaly leaves
4. Rhizome - horizontal underground stem
5. Tuber - fleshy underground stem
E. Plant propagation - growing new plants from the vegetative parts
1. Bulbs divide as they grow
2. Rhizomes, roots, and tubers can be split into pieces that will grow into new shoots
3. Tissue culture - cuttings of a plant are placed in a sterile medium to produce new plants