Plant Reproduction

Mostly About Reproductive Organs in Plants - Chapter 8

Plant KingdomGymnosperms - naked seeded plants don’t have flowers and don’t use insects to transport pollen.

This group includes pines, junipers, bald cypress, cicadas, podocarpus and the ginkgo tree.

Angiosperms - have flowers and often use insects to transport pollen. Includes dicots and monocots.

Dicots – you know their characteristics

This group includes oaks, roses, blueberries, honeysuckle, cactus and grapes.

Monocots – you know their characteristics

This group includes palms, grass, corn, orchids and bamboo.

Don’t forget that all plants undergo “alternation of

generations” in their cycle of existance. Each generation

alternates between the diploid sporophyte and the haploid

gametophyte.

Reproductive Organs

Male or Pollen cones ofred pine (Pinus resinosa).

Early second year cone of Knobcone Pine (Pinus attenuata).

This is the female cone of a Gymnosperm,

Flowers (dicot)

Monocot flower.

Complete flowers have sepals, petals, stamens, and pistils. Flower #1 is a complete flower. Incomplete flowers are missing one of more of the four basic parts. Flowers #2 & #3 are incomplete. Perfect flowers have both stamens and pistils. Flower #1 is a perfect flower. Imperfect flowers have either stamens or pistils, but not both. Flower #3 is an imperfect flower. Staminate flowers have only stamens. Pistillate flowers have only pistils. Monoecious plants have imperfect flowers with both sexes growing on the same plant. Dioecious plants have imperfect flowers with only one sex growing on each plant.

Complete Flower

IncompleteFlower

female

male

Pollination

• Wind – simple, plain, w/o nectar

• Vector pollination – large, fragrant, showy, w/ nectar

Other adaptations to help aide or encourage pollination

• Platforms (petal clusters)

• Nocturnal

• Devices (hammerback)

• Opening size

• Special scents

• Self-pollination is less adaptive

Cross pollination is favored

• Male flowers below female flowers

• Male flower matures before female flowers

• Anthers mature first in complete flowers

• Stigma longer than stamens

Pollen.

Pollinators

Pollination does NOT equal

Fertilization

Transfer of pollen is NOT the

joining of egg and sperm

Fertilization

Fertilization

Seed formation

• Post fertilization

• Wall of ovule = hard seed coat

• Zygote divides = embryo

• Triploid central cell = endosperm

• Many arctic plants cannot flower until the length of day light hours has reached at least a minimum value (long day plants). This means that warmer temperatures will not result in early flowering of the species, as it is dependent on light hours. Many temperate zone plants are short-day plants, where the shorter days of fall act as a trigger for flowering.

• Most plant species are day-neutral plants, which means their blooming times are controlled by temperature, moisture, or environmental factors other than day length

Seeds

Cones of (clockwise from top-left):Loblolly Pine (Pinus taeda)Jack Pine (Pinus banksiana)Gray Pine [with seeds] (Pinus sabiniana)Knobcone Pine (Pinus attenuata

Gymnosperm seed.

Dicot seed.

Monocot seed

Fruit Development• Ovary enlarges and

ripens• Seeds contained

within• Dry or fleshy

Do you know fruits from vegetables?

Seed Dispersal

Seed Germination

Summary

Asexual Reproduction• Vegetative reproduction

• From some vegetative organ rather than from the flower

• Includes roots, stems, leaves

• Part takes root and grows into a “clone” of the parent plant

• Strawberries and spider plants produce runners over the ground, irises and ferns produce rhizomes underground, daffodils and hyacinths produce daughter bulbs and potatoes produce daughter tubers.

Plant Hormones

Plant Growth

Growth

• Meristem tissue - source of new cells in plant growth

• apical meristem - produce growth in length (primary growth)lateral meristem - produce growth in thickness (secondary growth)

• Primary Growth: the growth initiated by the apical meristems of a plant or shoot. Basically what is meant by this term is the initial new growth of the plant stem and root. The parts of the stem and root which are the primary growth are mostly the very ends where the most growth is taking place and will take place.

• Secondary Growth: the increase in girth of the stems and roots of many plants, especially woody, perennial dicots. This occurs in plants such as a tree. When the plant grows it not only becomes taller but also the width or girth of the tree grows too. Obviously this is what is described as secondary growth.

Tropisms – growth responses by plants to their environment