Plant Structure and Growth

CHAPTER 35

PLANT STRUCTURE AND GROWTH

OUTLINE

I. Introduction to Modern Plant Biology

A. Molecular biology is revolutionizing the study of plants

B. Plant biology reflects the major themes in the study of life

II. The Angiosperm Body

A. A plant's root and shoot systems are evolutionary adaptations to living on land

B. Structural adaptations of protoplasts and walls equip plant cells for their specialized functions

C. The cells of a plant are organized into dermal, vascular, and ground tissue systems

III. Plant Growth

A. Meristems generate cells for new organs throughout the lifetime of a plant: an overview of plant growth

B. Primary growth: apical meristems extend roots and shoots by giving rise to the primary plant body

C. Secondary growth: lateral meristems add girth by producing secondary vascular tissue and periderm

OBJECTIVES

1. List the characteristics of an angiosperm.

Flowers and fruits, evolutionary adaptations that function in reproduction and the dispersal of seeds, characterize angiosperms.

2. Explain the differences between monocots and dicots.

Monocots have one cotyledon, the veins are usually parallel, vascular bundles are complexly arranged, have fibrous root system, and their floral parts are usually in multiples of three. Dicots have two cotyledons, the veins are usually netlike, they have vascular bundles arranged in ring, taproot usually present and their floral parts are usually in multiples of four or five.

3. Describe the importance of root systems and shoot systems to plants and explain how they work together.

Roots anchor the plant in the soil, absorb minerals and water, conduct water and nutrients, and store food. The shoot system consists of vegetative shoots, which bear leaves, and floral shoots, which terminate in flowers. Neither system can live without the other. Lacking chloroplasts and living in the dark, roots would starve from the photosynthetic tissues of the shoot system. Conversely, the shoot system depends on water and minerals absorbed from the soil by roots.

6. Describe how plant cells grow.

Meristems generate cells for new organs throughout the lifetime of a plant. Apical meriatems elongate shoots and roots through primary growth. Lateral meristems add girth to woody plants through secondary growth.

7. Distinguish between parenchyma and collenchyma cells with regards to structure and function.

Parenchyma cells, relatively unspecialized cells that retain the ability to divide, perform most of the plants metabolic functions of synthesis and storage. Collenchyma cells, which have unevenly thickened cell walls, support young, growing parts of the plant.

8. Describe the differences in structure and function of the two types of sclerenchyma cells.

The two forms of sclerenchyma cells are fibers and sclerids. Long, slender, and tapered, fibers usually occur in bundles. Sclerids are shorter than fibers and irregular in shape. Nutshells and seed coats owe their hardness to sclerids.

13. Describe the functions of the dermal tissue system, vascular tissue system and ground tissue system.

Dermal tissue protects the plant and sometimes-even help in the absorption of water and minerals. Vascular tissues functions in the transport and support, and ground tissues fill the space between the dermal and vascular tissue systems. Among the diverse functions of ground tissue are photosynthesis, storage, and support.

CHAPTER 36

TRANSPORT IN PLANTS

OUTLINE

I. An Overview of Transport Mechanisms in Plants

A. Transport at the cellular level depends on the selective permeability of membranes

B. Proton pumps play a central role in transport across plant membranes

C. Differences in water potential drive water transport

D. Vacuolated cells have three major compartments

E. The symplast and apoplast both function in transport within tissues and organs

F. Bulk flow functions in long-distance transport

II. Absorption of Water and Mineral by Roots

A. Root hairs, mycorrhizae, and a large surface area of cortical cells enhance water and mineral absorption

B. The endodermis functions as a selective sentry between the root cortex and vascular tissue

III. Transport of Xylem Sap

A. The ascent of xylem sap depends mainly on transpiration and the physical properties of water

B. Review: xylem sap ascends by solar-powered bulk flow

IV. The Control of Transpiration

A. Guard cells mediate the photosynthesis-transpiration compromise

B. Xerophytes have evolutionary adaptations that reduce transpiration

V. Translocation of Phloem Sap

A. Phloem translocates its sap from sugar sources to sugar sinks

B. Pressure flow is the mechanism of translocation in angiosperms

OBJECTIVES

1. List three levels in which transport in plants occurs and describe the role of aquaporins.

-Cellular Level, Tissue and Organs Level, Whole-Plant Level

2. Trace the path of water and minerals from outside the root to the shoot system.

8. Define water potential.

- Water potential is the negative pressure or tension of water.

9. Explain how solute concentration and pressure affects water potential.

- Osmosis occurs depending on the concentration of a solute, wherever there is more negative pressure is where water potential will be greatest since is always negative.

10. Predict the direction of net water movement based upon differences in water potential between a plant cell and a hypoosmotic environment, a hyperosmotic environment or an isosmotic environment.

- Net water movement will move to the hypo-osmotic environment since there is less water there. Water will move to the plant cell when encountered with a hyper-osmotic environment and no change will occur when the environment is iso-osmotic.

12. According to the transpiration-cohesion-adhesion theory, describe how xylem sap can be pulled upward in xylem vessels.

- Sap is pulled upward in xylem vessels by transpiration, which is the evaporation of liquids from the leaves. However, this would not be possible is water was not cohesive. Whenever one water molecule is removed it pulls the other, which are put together in a column due to adhesion, it sticks to the cell walls.

13. Explain why a water potential gradient is required for the passive flow of water through a plant, from soil.

- Water potential is the reason (one of them) why water moves at all. Water always moves from a place of lower negative pressure to a place of higher negative pressure.

15. Describe both the disadvantages and benefits of transpiration.

- Transpiration allows water to be moved to all parts of the plant, however since it is essentially evaporation too much of it could be detrimental to a plant.

18. List three cues that contribute to stomatal opening at dawn.

- Light. Induces guard cells to take up K+ by:

1. Activating a blue light receptor which stimulates proton pumps in the plasma membrane
2. Driving photosynthesis in guard cells chloroplasts, making ATP available for the ATP driven proton pumps.

- Decrease of CO2 in leaf air spaces due to photosynthesis in the mesophyll

- An internal clock in the guard cells. This will make them open even if the plant is kept in dark

19. Describe environmental stresses that can cause stomata to close during the daytime.

- There is a water deficiency resulting in flaccid guard cells.

- Mesophyll production of absidic acid (a hormone) in response to water deficiency signals guard cells to close.

- High temperature increases CO2 in leaf air spaces due to increased transpiration, closing guard cells.

CHAPTER 37

PLANT NUTRITION

OUTLINE

I. Nutritional Requirements of Plants

A. The chemical composition of plants provides clues to nutritional requirements

B. Plants require nine macronutrients and at least eight micronutrients

C. The symptoms of mineral deficiency depend on the function and mobility of the element

II. Soil

A. Soil characteristics are key environmental factors of terrestrial ecosystems

B. Soil conservation is one step toward sustainable agriculture

III. The Special Case of Nitrogen As a Plant Nutrient

A. The metabolism of soil bacteria makes nitrogen available to plants

B. Improving the protein yield of crops is a major goal of agricultural research

IV. Nutritional Adaptations: Symbiosis of Plants and Soil Microbes

A. Symbiotic nitrogen fixation results from intricate interactions between roots and bacteria

B. Mycorrhizae are symbiotic associations of roots and fungi that enhance plant nutrition

C. Mycorrhizae and root nodules may have an evolutionary relationship

V. Nutritional adaptations: Parasitism and Predation By Plants

A. Parasitic plants extract nutrients from other plants

B. Carnivorous plants supplement their mineral nutrition by preying on animals

OBJECTIVES

1. Describe the chemical composition of plants including:

a. Percent of wet weight as water

b. Percent of dry weight as organic substances

c. Percent of dry weight as inorganic minerals

- 80-85% of an herbaceous plant is water

- 95% organic substances

- 5% minerals, to some extent determined by soil composition.

3. Distinguish between macronutrient and micronutrient.

- Macronutrients are elements required by plants in large amounts. Micronutrients are elements required by plants in small amounts.

4. List the nine macronutrients required by plants and describe their importance in normal plant structure and

metabolism.

- Nitrogen, Potassium, Phosphorous, Calcium , Magnesium, Hydrogen, NO3-, H2PO4-, SO4-. Hydrogen ions in soil displace positively charged mineral ions from clay, making them available to plants. Potassium, Calcium and Magnesium adhere by electrical attraction to negatively charged clay molecules.

5. List seven micronutrients required by plants and explain why plants need only minute quantities of these elements.

- I already know this.

7. Explain how soil is formed.

- I already know this.

10. Explain how humus contributes to the texture and composition of soil.

- I already know this.

11. Explain why plants cannot extract all of the water in soil.

- I already know this.

15. List the three mineral elements that are most commonly deficient in farm soils.

- Nitrogen, Potassium and Phosophorous.

16. Describe the environmental consequence of overusing commercial fertilizers.

- The overuse of commercial fertilizers are not retained in the soil for long, so the minerals not used by the plants are leached off by rainwater or irrigation and drained into the groundwater and eventually pollute streams and lakes.

29. Describe modifications for nutrition that have evolved among plants including parasitic plants, carnivorous plants, and mycorrhizae.

- Parasitic plants have evolved to grow projections called haustoria to steal xylem sap

from the vascular tissue of the host tree. Carnivorous plants, due to poor soil, have

developed a system where they receive carbohydrates from photosynthesis and nitrogen

and minerals by killing and digesting insects; insect traps have evolved by the

modification of leaves.

CHAPTER 38

PLANT REPRODUCTION

AND DEVELOPMENT

OUTLINE

I. Sexual Reproduction

A. Sporophyte and gametophyte generations alternate in the life cycles of plants: a review

B. Male and female gametophytes develop within anthers and ovaries, respectively

C. Pollination brings female and male gametes together

D. Researchers are unraveling the molecular mechanisms of self-incompatibility

E. Double fertilization gives rise to the zygote and endosperm

F. The ovule develops into a seed containing an embryo and a supply of nutrients

G. The ovary develops into a fruit adapted for seed dispersal

H. Evolutionary adaptations of seed germination contribute to seedling survival

II. Asexual Reproduction

A. Many plants can clone themselves by asexual reproduction

B. Vegetative propagation of plants is common in agriculture

C. Sexual and asexual reproduction are complementary in the life histories of many plants: a review

III. Cellular Mechanisms of Plant Development

A. Growth, morphogenesis, and differentiation produce the plant body: an overview

B. The cytoskeleton guides cell division and expansion

C. Cell differentiation depends on gene regulation

D. Pattern formation determines the location and tissue organization of plant organs

OBJECTIVES

1. Outline the angiosperm life cycle.

- I already know this.

2. List the four floral parts in their order from outside to inside of the flower.

- Sepals, petals, stamens and carpels.

3. From a diagram of an idealized flower, correctly label the following structures and describe their function:

a. Sepals c. Stamen: filament and anther

b. Petals d. Carpel: style, ovary, ovule and stigma

- I already know this.

8. Explain by which generation, structures, and process gametes are produced.

- Pollen grains develop within the sporangia of anthers at the tips of stamens. Within each sac are numerous microsporocytes, the diploid cells that give rise to pollen. Meiosis forms four haploid microspores from each microsporocyte. Each microspore then undergoes a mitotic division, giving rise to a pollen grain that becomes a mature male gametophyte when the cell divides to form sperm. The embryo sac develops within an ovule. A diploid cell, a megasporocyte, divides by meiosis and gives rise to four cells where only one survives to become the megaspore. The mitotic divisions of the spore form the embryo sac.

10. Describe the formation of a pollen grain in angiosperms.

-Pollen grains develop within the sporangia of anthers at the tips of stamens. Within each sac are numerous microsporocytes, the diploid cells that give rise to pollen. Meiosis forms four haploid microspores from each microsporocyte. Each microspore then undergoes a mitotic division, giving rise to a pollen grain that becomes a mature male gametophyte when the cell divides to form sperm.

13. Distinguish between pollination and fertilization.

- Pollination is the first step towards fertilization; it leads to it. For the egg to be fertilized, the male and female gametophytes must meet and unite their gametes through pollination, the process of placing pollen onto the stigma of a carpel. Once the stigma identifies a pollen grain as compatible, the pollen grain produces a tube that extends down between the cells of the style toward the ovary.

14. Describe how pollen can be transferred between flowers.

-Pollen can be transferred between flowers by the wind or animals. Pollination occurs when a pollen released from anthers and carried by wind or animals land on sticky stigmas at the tips of carpels (though not necessarily on the same flower or plant). Fruits, carried by wind or animals, help disperse seed some distance from their source plant.

18. From a diagram, identify the following structures of a seed and recall a function for each:

a. Seed coat d. Radicle g. Endosperm

b. Embryo e. Epicotyl h. Cotyledons

c. Hypocotyl f. Plumule i. Shoot apex

- a. Seed coat- protects the embryo and its food supply

c. Hypocotyl- Terminates in the radicle

d. Radicle- embryonic root.

e. Epicotyl- above the cotyledons

f. Plumule- consists of the shoot tip with a pair of miniature leaves.

g. Endosperm- surrounds the embryo

h. Cotyledons- surrounds the embryo

19. Explain how a monocot and dicot seed differ.

-A monocot seed has a single cotyledon, called a scutellum. This seed leaf is very thin but has a large surface area, the better to absorb nutrients from the endosperm during germination. A dicot seed retains its food supply and have cotyledons that are very thin.

20. Describe several functions of fruit and explain how fruits form.

- Fruits protect the enclosed seeds and aids in their dispersal by wind or animals. The fruit begins to develop after pollination triggers hormonal changes that cause the ovary to grow tremendously. The wall of the fruit becomes the pericarp, the thickened wall of the fruit. As the ovary grows, the other parts of the flower wither away in many plants. This formation of the flower parallels the development of the seeds.

CHAPTER 39

CONTROL SYSTEMS

IN PLANTS

OUTLINE

I. Plant Hormones

A. Research on how plants grow toward light led to the discovery of plant hormones: science as a process

B. Plant hormones help coordinate growth, development, and responses to environmental stimuli

C. Analysis of mutant plants is enhancing plant research

D. Signal-transduction pathways link cellular responses to hormone signals and environmental stimuli

II. Plant Movements as Models for Studying Control Systems

A. Tropisms orient the growth of plant organs

B. Turgor movements are relatively rapid, reversible plant responses

III. Control of Daily and Seasonal Responses

A. Biological clocks control circadian rhythms

B. Photoperiodism synchronizes many plant responses to changes of season

IV. Phytochromes

A. Phytochromes function as photoreceptors in many plant responses to light and photoperiod

B Phytochromes may help entrain the biological clock

V. Plant Responses to Environmental Stress

A. Plants cope with environmental stress through a combination of developmental and physiological responses

VI. Defense Against Pathogens

A. Resistance to disease depends on a gene-for-gene recognition between plant and pathogen

B. The hypersensitive response (HR) contains an infection

C. Systemic acquired resistance (SAR) extends protection against pathogens to the whole plant

OBJECTIVES

2. List five classes of plant hormones, describe their major functions, and recall where they are produced in the plant.

-Please refer to the AP Biology book in page 753, Table 35.1, An Overview of Plant Hormones.

3. Explain how a hormone may cause its effect on plant growth and development.

- Hormones may cause its effect on plant growth and development by plant hormones help coordinate growth, development, and responses to environmental stimuli. In general, these hormones control plant growth and development by affecting the division, elongation, and differentiation of cells.

25. Define circadian rhythm and explain what happens when an organism is artificially maintained in a constant environment.

- A physiological cycle of about 24 hours, present in all eukaryotic organisms, that persists even in the absence of external cues.

27. Define photoperiodism.

- A physiological response to day length, such as flowering plants.

28. Distinguish among short-day plants, long-day plants, and day-neutral plants; give common examples of each; and explain how they depend upon critical night length.

- Please refer to the AP Biology Book on page 765, Figure 35.13Photoperiodic control of flowering.