Plant Unit- Chapter 22: Life Cycle of Ferns (p.562-563)

First Plants evolved from multicellular green Algae like Protists

Flowering

Cone bearing Flowers with seeds enclosed in fruit

Ferns

Seeds

Moss

Water Conducting Vascular Tissue

Algae

About 90% (235,000) of plant species are flowering!

Ferns

• Rhizomes: underground stems
• Fronds: large leaves
• Damp, dark forests
• Need water to reproduce.

Chapter 23 (page 580-582, 586)

Vascular Tissue –transport water and nutrients throughout the plant

1. Xylem – transports water

• Tracheid – long, narrow hollow cells with thick cell walls that are impermeable to water and resist pressure
• Vessel Element – wide cells that are arranged end to end on top of one another like a stack of tin cans to form a continuous tube through which water can flow.

2. Phloem – transports food

• Sieve Tube Elements – the main phloem cells; arranged end to end (like vessel elements) to form sieve tubes.
• Companion Cells – Surround sieve tube elements. Support the phloem cells and aid in the movement of substances in and out of the phloem stream.

Meristematic Tissue –produces new cells by mitosis.

• Found in the tips of shoots and roots. Responsible for the growth that takes place throughout the life of a plant.
• Plants grow for as long as they live.
• Apical Meristem – Found at the tip of the stem or root

Chapter 24: Reproduction of Seed Plants Notes (p.612-621)

Flowers are the reproductive organs of angiosperms. Most produce both male and female gametophytes.

1. Sepals –green, outermost circle of leaves that enclose and protect the flower.
2. Petals – are brightly colored to attract insects and other pollinators to the flower.
3. Stamens – the male reproductive structure composed of a filament and an anther
1. Filament – a long, thin stalk that supports an anther.
2. Anther – an oval sac male gametophytes (pollen grains) are produced.
4. Carpels (pistils) – the female reproductive structure that produce ovules.
1. Ovary – contains ovules
2. Style – a narrowed stalk that is above the ovary.
3. Stigma – a sticky portion at the top of the style where pollen grains land.
4. Compound Carpel –several carpels fused together to form a single reproductive structure.

Pollination –

a. Animal Pollinators – insects, birds and bats; carry pollen from one flower to another and are attracted by bright colors and sweet nectar of the flower. Animals get food and plants get their pollen transferred.

b. Wind Pollination – not as reliable as animal pollination so produce more pollen

§ Fertilization of Angiosperms

o Pollen tube –grows into the style until it reaches the ovary and enters the ovule.

o Embryo Sac – two distinct fertilizations (Double Fertilization) take place

§ One of the sperm nuclei fuses with the egg nucleus to produce a diploid zygote that grows into the plant embryo.

§ The other sperm nucleus fuses with two endosperm nuclei in the embryo sac to form a triploid cell that grows into endosperm. Endosperm – a food-rich tissue that provides the embryo with a food source as it grows.

§ Seed and Fruit Development

Fruit – a ripened ovary that contains seeds and a seed coat.

Seed Coat – the outer layer that protects the delicate embryo and its tiny food supply Seed Dispersal

o Dispersal by Animals –seeds are eaten by animals. The tissue surrounding the seeds protects them as they pass through the digestive system.

o Dispersal by Wind and Water – seeds dispersed by wind or water are lightweight. Coconuts are dispersed by water.

§ Seed Dormancy – a period during which the embryo is alive but not growing. Environmental factors such as temperatures and moisture can cause a seed to end dormancy and germinate.

o Benefits of Dormancy – can allow for long-distance dispersal; allow seeds to germinate under ideal growth conditions; some seeds are opened by fire (some pine trees) allowing seeds to regrow after a fire destroys all of the old trees.

§ Seed Germination

o Germination – the early growth stage of the plant embryo; when seeds germinate they absorb water causing the endosperm to swell cracking open the seed coat.

Chapter 25: Plant Responses and Adaptations

• Plant Signals – plants send signals to one another indicating when to grow, when not to grow, and when to develop into a new kind of cell.
• Length of Growth – plants never stop growing
• Controlling Factors – plants grow in response to environmental factors such as light, moisture, temperature and gravity.

Plant Hormones

• Hormones – substances that are produced in one part of a plant and affect another part (Target Cell/Tissue) of the same plant

1. Auxins – stimulate cell elongation and are produced in the apical meristem and transported downward into the rest of the plant. Auxins also regulate cell division in meristems.

o Phototropism – the tendency of a plant to grow toward a source of light.

o Auxins & Phototropism – when light hits one side of the stem, the auxins are broken down. Cells on the dark side elongate and the stem bends away from the shaded side toward the light.

o Gravitropism – the tendency of a plant to grow in a direction in response to the force of gravity.

o Auxins and Gravitropism – auxins build up on the lower sides of roots and stems and the auxins stimulate cell elongation on the lower side of stems helping turn the plant upright and the roots downward.

o Thigmotropism – the response of plants to touch.

§ Touched regularly – may have stunted growth; sometimes quite dramatically.

§ Climbing Plants – the stems of these plants don’t grow straight up, but grows sideways and twists instead.

o Lateral Bud – a meristematic area on the side of a stem that gives rise to side branches; growth at these buds is inhibited by auxins.

o Auxins and Branching – Auxins also regulate cell division in meristems.

o Apical Dominance –the closer the bud is to the stem’s tip, the more its growth is inhibited. If you cut off the tip of the stem, the apical meristem is removed and the auxins.

o Auxinlike Weed Killers – high concentrations of auxins inhibit growth and so many of these compounds are used as herbicides. (2-4 D)

2. Cytokins – hormone produced in growing roots and in developing fruits and seeds.
• Stimulate cell division and the growth of lateral buds
• Cause dormant seeds to sprout.
• Delay the aging of leaves and
• Play important early stages of plant growth.
• Cytokins often produce effects opposite to those of auxins.

3. Gibberellins –produced in the seeds and cause dramatic increases in size during early stages of growth, in stems and fruits.

4. Ethylene –stimulates fruits to ripen. (Bananas)

Rapid Responses – some plant responses do not involve growth and are very quick.

o EX: Venus flytrap – has sensory hairs that are triggered by insects. When the sensory cells are triggered, an electrical signal is sent from cell to cell. Osmotic pressure along with cell wall expansion then cause the leaf to snap shut, trapping the insect inside.

§ Winter Dormancy – Regulated by phytochrome. As cold weather approaches, deciduous plants turn off photosynthesis pathways, transport materials from leaves to roots, and seal leaves off from the rest of the plant. This occurs because in the autumn/winter photosynthesis is poor and it is more efficient for the plant to shed its leaves than to photosynthesize during the winter.

o Falling Leaves – The change in the amounts of auxins and ethylene results in the shutting down of the leaves. First chlorophyll synthesis stops and light destroys the remaining green pigments revealing the yellow and orange carotenoids and the reddish anthocyanins that were present all along but hidden by the chlorophyll. All available carbohydrates are transported out of the leaf and much of the leaf’s water is extracted.

o Leaf Abscission - a layer of cells forms at the petiole sealing the leaf off from the plant’s vascular system. The leaf falls off as a result.

o Overwintering in Meristems – hormones produce important changes in apical meristems. After leaves fall off, meristems produce thick, waxy scales that for a protective layer over leaf buds allowing terminal buds to survive the coldest of winters.

• Carnivorous Plants - plants that digest insects for nutrients that are deficient in their environments.
• Parasites – plants that extract water and nutrients directly from a host plant. They harm their host organisms.

§ Epiphytes – Plants that grow directly on the bodies of other plants; attached to the plants they grow on, but they gather their own moisture and produce their own food unlike parasites.

Chemical Defenses – many plants manufacture compounds that have powerful effects on animals as a defense. Some of these chemicals act as a poison killing the insects, others prevent them from reproducing.