Reproduction of Seed Plants

Dragonfly – Ch. 24 Adv Bio – Ch. 38

I. Reproduction with Cones and Flowers A. Alternation of Generations 1. all plants have a life cycle in which a diploid sporophyte generation alternates with a haploid gametophyte generation 2. gametophyte plants produce both male and female gametes (ie – egg & sperm) 3. when the gametes join, they form a zygote that begins the next sporophyte generation

Evolution of the Gametophyte and the Sporophyte

Gametophyte (N) Sporophyte (2N)

Bryophytes Ferns Seed plants

B. Life Cycle of Gymnosperms 1. reproduction takes place in cones 2. cones are produced by mature sporophyte plants

3. Pollen Cones and Seed Cones a. Pollen cones 1) male cones 2) smaller b. Seed cones 1) female c. Ovules 1) located near the base of each scale 2) where egg cells develop

4. Pollination a. Gymnosperm life cycle takes 2 years b. Pollen grains blown by the wind 5. Fertilization and Development a. Pollen tube 1) grows when a pollen grain lands near an ovule 2) contains 2 haploid sperm – only 1 is needed b. Fertilization occurs and produces a diploid zygote

C. Structure of Flowers 1. reproductive organs 2. contains 4 kinds of specialized leaves a. Sepals 1) outermost circle of floral parts 2) enclose the bud before it opens

b. Petals 1) often brightly colored 2) attract insects and other pollinators

c. Stamens - male 1) anther a) meiosis – produces haploid male gametophytes – pollen grains 2) filament a) long, thin stalk supports anther

d. Carpels or pistils 1) produce female gametophyte 2) ovary a) contains 1 or more ovules where female gametophytes are produced 3) style a) narrow stalk 4) stigma a) at the top of style b) sticky part where pollen grains land

D. Life Cycle of Angiosperms 1. reproduction takes place in the flower 2. after pollination and fertilization, the seeds develop inside protective structures

E. Fertilization in Angiosperms 1. endosperm a. Food-rich tissue in the seed that provides nutrients to the seedling

2. Double fertilization a. Two distinct fertilizations occur b. One of the sperm nuclei fuses with the egg nucleus to produce a diploid zygote 1) this will grow into the new plant embryo c. The other sperm nucleus fuses with two polar nuclei to form a triploid (3N) cell which grows into the endosperm

II. Seed Development and Germination

A. Seed and Fruit Development 1. as angiosperm seeds mature, the ovary walls thicken to form a fruit that encloses the developing seeds 2. fruit a. Any seed that is enclosed within its embryo wall

B. Seed Dispersal 1. animals 2. wind 3. water

C. Seed Dormancy 1. period in which the embryo is alive, but not growing 2. environmental factors such as temperature and moisture can end dormancy causing the seed to germinate

D. Seed Germination 1. the early growth stage of the plant embryo 2. absorbed water causes the seed to swell breaking the seed coat 3. embryo uses endosperm for nourishment

Section 24-2

Monocots have 1 Cotyledon that Remains with the seed

Seed Germination

in Dicots have 2 Cotyledons that Emerge above ground Remain below ground

III. Plant Propagation and Agriculture

A. Vegetative reproduction 1. the production of new plants from horizontal stems, plantlets, and underground roots

B. Plant Propagation 1. the production of offspring through artificial means 2. cuttings a. A length of stem that includes lateral buds is cut from the parent plant and partially buried in soil or rooting mixture to take root b. sometimes requires rooting hormones

3. grafting a. A piece of stem is cut from the parent plant and attached to another plant 4. budding a. A bud from one plant is inserted into the stem of another plant where it continues to grow

C. Agriculture 1. most of the world’s population depends upon wheat, rice, corn, and soybeans for the bulk of their food supply 2. Biotechnology and the Future