Chapter 35- Plant Structure And Growth

Chapter 35- Plant Structure and Growth

1. List the characteristics of an angiosperm. Angiosperms are characterized by flowers and fruits, evolutionary adaptations that function in reproduction and dispersal of the seed.

2. Explain the differences between monocots and dicots. Monocots are named for their single cotyledon (seed leaf), their veins are usually parallel, their vascular bundles are complexly arranged, they have a fibrous root system, and floral parts usually are in multiples of three. Dicots, which have two cotyledons, have veins that are usually netlike, their vascular bundles are arranged in rings, taproots are 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. Differentiation of the plant body into an underground root system and an aerial shoot system consisting of stems, flowers and leaves. Neither system can live without the other. Lacking chloroplasts and living in the dark, roots would starve without sugar and other organic nutrients imported from the photosynthetic tissues of the shoot system. Conversely, the shoot system depends on water and minerals absorbed from the soil by roots. Vascular tissues, continuous throughout the plant, transport materials between roots and shoots.

6. Describe how plant cells grow. A plant cell consists of a protoplast enclosed in a cell wall. The protoplast is bounded by the plasma membrane. Outside the plasma membrane is the primary cell wall and in some plants a secondary cell wall. Between the primary walls of adjacent plant cells is the middle lamella, a sticky layer that cements the cells together. The protoplasts of neighboring cells are generally connected by plasmodesta, cytoplasmic channels that pass through pores in the walls. The plasmodesta may be concentrated in areas called pits, where the distance between adjacent protoplasts is narrowed. When matured, most living plant cells have a large central vacuole that occupies as much as 90% of the volume of the protoplast. A membrane called the tonoplast separates the contents of the vacuole from the thin layer of cytoplasm. Within the vacuole is the cell sap, a complex aqueous solution that helps the vacuole play an important role in maintaining the turgor, or firmness of the cell.

7. Distinguish between parenchyma and collenchyma cells with regards to structure and function. Parenchyma cells are the least specialized plant cells, performing general metabolic and storage functions. They retain the ability to divide and differentiate into other cell types under certain conditions. Collenchyma cells support young parts of the plant shoot without retraining growth.

8. Describe the differences in structure and function of the two types of sclerenchyma cells. Sclerenchyma cells, fibers and sclereids, are supportive cells with thick, lignified secondary walls. Many lack protoplasts; thus, at maturity they are able to elongate. The fiber cells are elongated sclerenchyma cells. Sclereids are irregularly shaped sclerenchyma cells with very thick, lignified secondary cells.

13. Describe the functions of the dermal tissue system, vascular tissue system and ground tissue system. Plant tissues are arranged into three continuous systems. The dermal tissue, or epidermis, is an external layer of tightly packed cells that functions in protection. The vascular tissue system, consisting of xylem and phloem, provides transport and support. The predominantly parenchymous ground tissue system functions in organic synthesis, storage and support. 18. Distinguish between the arrangement of vascular tissues in roots and shoots. Root tips, protected by the root caps, grow and develop by the activities of cells int he zones of cell division, elongation and maturation. Just behind the apical meristem in the zone of cell division, are three primary meristems of the root . The protoderm gives rise to the epidermis, the procambium forms the central vascular stele, and the ground meristem produces ground tissue of the cortex. Subsequent lateral roots arise from the pericycle of the stele. In contrast to the single stele of the root, the vascular tissue of stems run in vascular bundles surrounded by ground tissue in characteristic patterns that differ between monocots and dicots.

20. Using a diagram, describe the basic structure of a root, a stem, and a leaf. I am familiarized with the structure of a root, stem and leaf.

Chapter 36 - Transport in Plants

1. List three levels in which transport in plants occurs and describe the role of aquaporins. Transport occurs at the level of individual cells, at the short-distance level of lateral transport within plant organs, and at the long-distance level of sap flow within the xylem and phloem. Different mechanisms operate at these different levels of transport.

2. Trace the path of water and minerals from outside the root to the shoot system. 1: Roots absorb water and dissolved minerals from the soil. 2: Roots also exchange gases with the air spaces of soil, taking in O2 and discharge in CO2. This gas exchange supports the cellular respiration of root cells. 3: Water and minerals are transported upward as xylem sap within xylem, from the roots into the shoot system. 4: Transpiration, the evaporation of water from leaves creates a force within leaves that pulls xylem sap upward. 5: Leaves also exchange gases through stomata, taking in the CO2 that provides carbon for photosynthesis and expelling O2. 6: Sugar is produced by photosynthesis in the leaves and 7: is transported within phloem in a solution called phloem sap and other non-photosynthetic parts of the plant.

8. Define water potential. The combined effects of solute concentration and pressure are incorporated into a single measurement called water potential.

9. Explain how solute concentration and pressure affects water potential. Differences of water potential drive the osmotic movement of water into and out of plant cells. Solutes lower water potential, and pressure increases water potential.

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. When a plant is placed in a hypotonic environment, the lower water potential in the cell due to its higher solute concentration causes the osmotic uptake of water. Eventually, pressure exerted by the elastic wall equilibrates walter potential of the cell and its surroundings, and water entry and exit are not balanced for the turgid cell. In a hypertonic environment, the cell initially has a greater water potential than its surroundings. The cell loses water and plasmolyzes. After plasmolysis is complete, the water potentials of the cell and its surroundings are the same. Plasmolysis kills most plant cells.

12. According to the transpiration-cohesion-adhesion theory, describe how xylem sap can be pulled upward in xylem vessels. The transpiration-cohesion-tension mechanism transports xylem sap. Evaporative water loss during transpiration generates surface tension of the water film coating mesophyll cells. This tension, or negative pressure causes water to move by bulk flow out of the xylem vessels. The cohesion of water is due to hydrogen bonding relays the transpirational pull on xylem sap all the way down to the roots.

13. Explain why a water potential gradient is required for the passive flow of water through a plant, from soil. The water flow of water through a plant from soil fits the equation for water potential. Since water moves from where its potential s higher to where it is lower, mesophyll cells will lose water to the surface film lining air spaces, which in turn loses water by transpiration. The water lost via the stomata is replaced by water that is pulled out of the leaf system.

15. Describe both the disadvantages and benefits of transpiration. I can well differentiate between the disadvantages and benefits of transpiration.

18. List three cues that contribute to stomatal opening at dawn. At least three cues contribute to stomotal opening at dawn. First, light itself stimulates guard cells to accumulate potassium and become turgid. This response is triggered by the illumination of a blue-light receptor in a guard cell. Activation of these receptors stimulates the activity of ATP-powered proton pumps in the plasma membrane of the guard cells,. Light may also stimulate stomotal opening by driving photosynthesis in guard cell chloroplasts, making ATP available for active transport. A second factor cause stomata to open is depletion of CO2 within air spaces of the leaf, which occurs when photosynthesis begins at mesophyll. A third cue is an internal clock located in the guard cells regulating cyclical processes.

19. Describe environmental stresses that can cause stomata to close during the daytime. Environmental stresses can cause a stomata to close during daytime. When the plant is suffereing water deficiency, guard cells may lose turgor. In addition, a hormone called abscisic acid signals guard cells to close the stomata. High temperatures and excessive transpiration also induce stomotal closure.

Chapter 37 Plant Nutrition

1. Describe the chemical composition of plants including: a. Percent of wet weight as water: About 80%-85% of hebaceous plant is water, and plants grow mainly by accumulating water in the central vacuoles of their cells. However, more than 90% of the water absorbed by plants is lost by transpiration. b. Percent of dry weight as organic substances: Organic substances account for about 95% of the dry weight of plants. Carbon, oxygen, and hydrogen, are the most abundant elements in the dry weight of a plant. c. Percent of dry weight as inorganic minerals: Inorganic materials make up the remaining 5% of dry weight in plants. The minerals in a plant reflect the composition of the soil in which the plant is growing. Plants growing on mine tailings, for instance, may contain gold or silver.

3. Distinguish between macronutrient and micronutrient. Macronutrients are elements required by plants in relatively large amounts. Micronutrients are elements that plants need in very small amounts.

4. List the nine macronutrients required by plants and describe their importance in normal plant structure and metabolism. The nine macronutrients required by plants are carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus, calcium, potassium, and magnesium. Carbon, oxygen, and hydrogen are major components of plant's organic compounds. Nitrogen, phosphorus and sulfur are components of nucleic acids, proteins, and coenzymes. Potassium is a cofactor functional in protein synthesis. Calcium is important in formation and stability of cell walls, maintenance of membrane structure and permeability, activates some enzymes and regulates many responses of cells to stimuli. Magnesium is a component of chlorophyll and activates many enzymes.

5. List seven micronutrients required by plants and explain why plants need only minute quantities of these elements. The eight micronutrients required by plants are iron, chlorine, copper, manganese, zinc, molybdenum, boron, and nickel. These elements function in plants mainly as cofactors of enzymatic reactions. It is because micronutrients generally play catalytic roles that plants need only minute quantities these elements.

7. Explain how soil is formed. Soil originates in the weathering of rocks, often due to freezing and cracking. Once rocks dissolve into small particles, organisms like algae are able to invade the rock accelerating decomposition. This results in the formation of topsoil, a mixture of decomposed rock, living organisms, and humus. However, the most fertile soil is usually loams, made up of a mixture of sand, silt, and clay.

10. Explain how humus contributes to the texture and composition of soil. Vents clay from packing together and builds a crumbly soil that retains water but is still porous enough for the adequate aeration of roots. Humus is also a reservoir of mineral nutrients that are returned gradually to the soil as microorganisms decompose the organic matter.

11. Explain why plants cannot extract all of the water in soil. Plants cannot extract all of the water in soil because roots suffocate due to the fact that air spaces would be replaced by water; roots may also be attacked by molds that favor soaked soil. However, some plants are adapted to waterlogged soil and have modified roots that act as a snorkel acquiring oxygen from the air.

15. List the three mineral elements that are most commonly deficient in farm soils. Nitrogen, phosphorus, and potassium are the three mineral elements that are most commonly deficient in farm soils.

16. Describe the environmental consequence of overusing commercial fertilizers. The excess minerals not used by plants are wasted because they may be rapidly leached from the soil by rainwater or irrigation. To make matters worse, this mineral runoff may enter the groundwater and eventually pollute streams an lakes.

29. Describe modifications for nutrition that have evolved among plants including parasitic plants, carnivorous plants, and mycorrhizae. Parasitic plants either supplement their photosynthetic nutrition or give up photosynthesis entirely by tapping into the vascular tissues of host plants. Carnivorous plants obtain nitrogen and minerals by killing and digesting insects. Micorrhizae help the plant by enhancing mineral nutrition, water absorption, and resistance to pathogens.

Chapter 39 - Control Systems in Plants

2. List five classes of plant hormones, describe their major functions, and recall where they are produced in the plant. Auxin - produced in embryo of seed, meristems of apical buds, and young leaves. It stimulates stem elongation root growth, differentiation and branching, development of fruit; apical dominance; phototropism and gravitopism.

Cytokinins - Synthesized in roots and transported to other organs. It affects root growth and differentiation; stimulate cell division and growth, germination, and flowering.

Gibberelins - produced in meristems of apical buds and roots, young leaves, and embryo. They promote seed and bud germination, stem elongation, leaf growth; stimulate flowering and development of fruit; affect root growth and differentitiation.

Abscisic - produced in the leaves, stems, and green fruit. It inhibits growth; closes stomata during water stress; counteracts breaking of dormancy.

Ethylene - produced in tissues of ripening fruits, nodes of stems, senescent leaves, and flowers. It promotes fruit ripening; opposes some auxin effects; promotes or inhibits growth and development of roots, leaves, and flowers, depending on species.

3. Explain how a hormone may cause its effect on plant growth and development. Hormones control plant growth and development by affecting the division, elongation, and differentiation of cells. Some hormones also mediate shorter-term physiological responses of plants to environmental stimuli.

25. Define circadian rhythm and explain what happens when an organism is artificially maintained in a constant environment Circadian rhythm is a cycle with a frequency of about 24 hours. These persist even when the organism is sheltered from environmental cues. If an organism is kept in a constant environment, circadian rhythms deviate from a 24-hour period. These free running periods vary from about 21 to 27 hours, depending on the particular rhythmic response.

27. Define photoperiodism. Photoperiodism is a physical response to day length.

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. Short day plants require a light period shorter than a critical length to a flower. These include chrysanthemums, and bloom in late summer, fall or winter. Long day plants generally flower in late spring or early summer. This includes spinach and lettuce. Day-neutral plants flower when they reach a certain stage of maturity, regardless of day length at that time. Long day plants flower when the night is shorter than the critical length.