Transcript Ch.24 - Jamestown School District

Unit 7 Plants
Ch. 24 Reproduction of Seed Plants
Structure of Flowers

Flowers are reproductive organs composed
of 4 kinds of specialized leaves: sepals,
petals, stamens, & carpals
Sepals & Petals
Sepals - green leaves that enclose the bud
before it opens, & they protect the flower
while it is developing
 Petals - often brightly colored, found just
inside the sepals

– Attract insects & other pollinators to the flower
Stamens & Carpels
Stamen - the male parts, consist of an anther
& a filament
 Filament - a long, thin stalk that supports
the anther
 Anther - found at the tip of each filament,
where pollen grains
are formed

Stamens & Carpels
Carpels - (pistils) - the female parts,
consists of an ovary, style, & stigma
 Ovary - contains 1/more ovules where eggs
are produced
 Style - stalk connecting the ovary to the
stigma
 Stigma - top of the style, where pollen
grains land

Pollination

Most gymnosperms & some angiosperms
are wind pollinated, whereas most
angiosperms are pollinated by animals
Seed & Fruit Development

As angiosperm seeds mature, the ovary
walls thicken to form a fruit that encloses
the developing seeds
Seed Dispersal

Dispersal by Animals
– Seeds dispersed by animals are
typically contained in fleshy,
nutritious fruits
Seed Dispersal

Dispersal by Wind & Water
– Seeds dispersed by wind or water are typically
lightweight, allowing them to be carried in the
air or to float on the surface of the water
Seed Dormancy
Dormancy - when the embryo is alive but
not growing
 Environmental factors such as temperature
& moisture can cause a seed to end
dormancy & germinate

Seed Germination

Germination - early growth stage of the
plant embryo
Vegetative Reproduction
Vegetative reproduction - type of asexual
reproduction
 Vegetative reproduction
includes the production of
new plants from horizontal
stems, from plantlets, &
from underground roots

Vegetative Reproduction

Stolons - long, trailing stems that produce
roots when they touch the ground
– Ex.) strawberry plants
Plant Propagation

In plant propagation, horticulturists use
cuttings, grafting, or budding to make many
identical copies of a plant or to produce
offspring from seedless plants
Plant Propagation
Cutting - cut part of the plant stem & plant
it in the ground
 Grafting - when a piece of stem
or bud is cut from a parent plant
& attached to another plant

– The cut piece is called the scion
Plant Propagation

Budding - when buds are used as scions
Agriculture

Most of the people of the world depend on a
few crop plants, such as wheat, rice, & corn,
for the bulk of their food supply
Agriculture

Between 1970 & 2000, the amount of corn
grown per acre in the US increased more
than 60%