10-1

Chapter 10: Plant Reproduction, Growth, and

Development

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

10-2

Sexual Reproduction in Flowering Plants

Sexual reproduction requires gametes, often as egg and sperm.

In flowering plants, the structures that produce the egg and sperm are located within the flower.

10-3

Flower structure

The reproductive portions of a flower are the stamen (male part), consisting of a filament and an anther, and the pistil (female part), made up of stigma, style, and ovary.

Sepals enclose a whorl of petals that are usually colored to attract pollinators.

The ovary contains one or more ovules.

10-4

Alternation of Generations

The sporophyte of flowering plants is dominant and produces two types of spores, microspores and megaspores.

Fig 10.1

10-5

Alternation of generations in a flowering plant

The sporophyte (2N) produces haploid (N) spores by meiosis.

A spore develops into a haploid gametophyte that produces gametes.

Fig 10.1

10-6

Fig 10.2

Sperm travel down the pollen tube; one sperm unites with the egg and becomes a zygote that develops into an embryo. The other sperm unites with the polar nuclei to produces triploid (3n) endosperm that nourishes the embryo. These two fusions are known as double fertilization.

10-7

The ovule wall hardens and becomes the seed coat.

The seed consists of the sporophyte embryo, stored food, and a seed coat.

The ovary may develop into a fruit.

10-8

Growth and Development in Plants

Development is a programmed series of stages from a simpler to a more complex form.

Cellular differentiation is specialization during development.

10-9

Development of a dicot embryo after double fertilization Fig 10.3

Becomes the Shoot

Becomes the Stem

Becomes the Root

Seed Leaves

Store nutrients taken from the endosperm

10-10

The monocot embryo has only one cotyledon that rarely stores food.

10-11

Dispersal of Seeds

Seeds are modified to be distributed far from the parent plant, by wind, animal carrier, or by ocean currents.

10-12

Germination of SeedsGermination of seeds occurs if there is

sufficient water, warmth, and oxygen to sustain growth.

Dormancy may be required before germination, and some seeds require periods of cold or minimal moisture.

10-13

Common garden bean, a dicotFig 10.5

10-14

The coleoptile and coleorhiza are protective sheaths around the monocot plumule and radicle.

Corn, a monocotFig 10.6

10-15

Asexual Reproduction in Flowering Plants

Non-differentiated meristem tissue allows a plant to reproduce by asexual vegetative propagation.

In horticulture, identical offspring produced by vegetative cuttings are clones.

10-16

Propagation of Plants in Tissue Culture

Plant cells are totipotent, having all the genetic potential to become mature specialized plants.

Fig 10.7

10-17

Genetic Engineering of Plants

Various techniques introduce foreign DNA into protoplasts that are propagated in tissue culture.

10-18

Control of Plant Growth and Development

Since each plant cell is totipotent, hormones have a role in determining cellular differentiation.

10-19

Plant Hormones

There are five common groups of plant hormones:

Auxins – promotes cell elongation and prevents growth of axillary buds (apical dominance)

Gibberellins – promote growth of stems and can break seed dormancy

Cytokinins – promote cell division

Abscisic acid – Stress hormone

Ethylene – ripens fruit and causes abscission of leaves by increasing enzyme activity

10-20

Effects of plant hormonesFig 10.9

Auxins Gibberellins

10-21

Effects of ethylene Fig 10.9

10-22

Plant Responses to Environmental Stimuli

Plant growth and development are influenced by environmental stimuli such as light, day length, gravity, and touch.

10-23

Positive phototropismPositive phototropism is due to the migration of auxin (stimulates cell elongation) from the bright side to the shady side of a stem.

Fig 10.10

10-24

Negative gravitropism

In negative gravitropism, stems curve away from gravity due to auxin on the lower side of the stem.

Fig 10.11

10-25

FloweringShort-day (long night) plants flower when the

days get shorter than a critical length. Long-day (short night) plants flower when the

days get longer than a critical length.

Day-neutral plants do not depend on day length for flowering.

Phytochrome is a plant pigment believed to be involved in regulating the response of plants to day length.

10-26

Transport in the Mature Plant

Active transport concentrates minerals in root cells and xylem.

Water (and some minerals) then diffuses into the root cells and forms positive root pressure.

Water and Mineral Transport in Xylem

Fig. 9.8

10-27

Cohesion-tension theory of xylem transport

Polar water molecules are cohesive and adhere to the walls of the xylem vessel and fill the water pipeline.

Transpiration, evaporation of water from leaves, creates a negative pressure that pulls the water column upward.

Fig 10.15

10-28

Opening and Closing of Stomata

Guard cells on either side of a stoma regulate its opening and closing, by changing turgor pressure.

10-29

Pressure-flow theory of phloem transport (translocation)

Sugar is actively transported into sieve-tube elements and water follows passively and creates pressure .

Sap moves to ‘sinks’ and sugar is actively transported out of phloem

10-30

Adaptations of Roots for Mineral Uptake

Plants are important for concentrating minerals that are used by consumers including humans.

10-31

Root nodules

Bacteria in the root nodules of legumes are symbionts that convert the nitrogen in the atmosphere to NH4

+.

10-32

Mycorrhizae

Mycorrhizae increase water and mineral uptake and improve nutrient transfer

10-33

Epiphytes (air plants) do not grow in soil and therefore must use roots to extract moisture from air and catch rain and minerals in leaves.

Parasitic plants send out root-like haustoria that tap into the xylem and phloem of the host stem.