Plant Bio Test 2

28. What does a negative photosynthetic rate indicate? When does the photosynthetic rate equal respiration?

. A negative photosynthetic rate indicates when respiration exceeds photosynthesis. a. The photosynthetic rate equals respiration when there is dim sunlight (early mornings and late evenings).

What is the Red drop effect?

. A sharp decrease in quantum yield (number of oxygen molecules released per quantum of light absorbed) at wavelengths greater than 680 nm in green plants. Red drop because 680 nm occurs in the red part of the spectrum.

40. What is a light compensation point? How do they compare in sun and shade plants?

. The (light) compensation point is the amount of light intensity on the light curve where the rate of photosynthesis exactly matches the rate of respiration.

What is the equation for photosynthesis?

6CO2 + 6H2O ------> C6H12O6 + 6O2

d. Photorespiration:

Location-Electron transport system of photosynthesis in the thylakoid membrane of the chloroplast.

a. Electron transport chain of respiration

Location-inner membrane of the mitochondria. Main products-ATP and H2O.

b. Krebs cycle

Location-mitochondrial matrix. Main products-NADH, FADH2, ATP, CO2.

Absorption of light energy

Location-photosystems on the thylakoid membrane of the chloroplasts

. Calvin cycle:

Location-stroma of the chloroplast (light-independent reaction). Main products-glucose.

21. What is the major limiting nutrient for plant growth and is it a micro or macro nutrient?

Nitrogen and it is a macronutrient

26. Do plants NEED oxygen?

Plants do need oxygen to survive. During respiration, they take in oxygen in order to give off carbon dioxide.

Why is absorption of too much light a problem for plants?

The chlorophyll and carotenoid molecules absorb more energy than they can handle and generate reactive species of oxygen that can destroy the plant.

Transpiration

The process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapor and is released to atmosphere

Describe photosystem 1

The second photosystem in the photosynthetic light reactions in plants. It is an integral membrane protein complex that uses light energy to produce the high energy carriers ATP and NADPH.

Bulliform Cells

large, bubble shaped epidermal cells that occur in groups on the upper surface of the leaves in many monocots

Biochemical reactions of psn

light energy from the sun is converted to stored chemical energy in glucose

translocation

the movement of materials from the leaves to other tissues throughout the plant

23. What is photorespiration? Where does it take place? How does it differ from respiration?

. A respiratory process in many higher plants by which they take up oxygen in the light and give out some carbon dioxide, contrary to the general process of photosynthesis. Leads to the loss of already fixed carbon as CO2. a. Photorespiration takes place in the stroma of the chloroplast (competes with the Calvin cycle). b. During photorespiration, the enzyme Rubisco acts on oxygen instead of carbon dioxide like during normal respiration.

41. What changes would you expect to see in a leaf of a tree seedling as it acclimates to full sun from a shady understory position (like after a tree fall gap occurs).

. An increase in photosynthetic rates, leaves oriented perpendicular to the sun, a thickening of the leaves, higher respiration rates.

47. Discuss the photosynthesis-transpiration compromise. Tell what regulates stomatal opening and what regulates stomatal closing.

. By closing stoma to conserve water, the diffusion of atmospheric CO2 into the leaf for carbon fixing is compromised. Productivity in the plant is therefore limited by the need to retain water. Closing stoma also builds up O2 from the light reactions in the leaf which further comprises carbon fixing by photorespiration. a. Stomatal opening: accumulation of potassium ions. Stomatal closing: accumulation of calcium ions.

24. What adaptations do plants have to limit photorespiration? Does it have any benefits?

. C3 carbon fixing plants are adapted to environments where they are able to keep their stomata open long enough during the day so natural circulation of gases keeps concentrations of CO2 and O2 in the leaf at proportions where photorespiration is less compromising and productivity is sufficient. C4 and CAM carbon fixing plants are adapted to climates where the need for water conservation limits the natural circulation of gases in the leaf because stomata must be restricted or closed during the day to reduce transpiration. a. Benefits-Photorespiration can have photoprotective effects (preventing light-induced damage to the molecules involved in photosynthesis), help maintain redox balance in cells, and support plant immune defenses.

What is the difference in C3 and C4 plants?

. C3 plants use the Calvin cycle in the dark reaction of photosynthesis, C4 plants do not; C3 plants in temperate conditions, C4 plants in tropical conditions; C3 bundle sheath cells do not contain chloroplasts, C4 bundle sheath cells do contain chloroplasts; C3 plants only possess one CO2 acceptor (pump), C4 plants have two CO2 acceptors (pumps); CO2 fixation faster in C4 plants compared to C3 plants.

38. In what kinds of environments do each of the alternative pathways of photosynthesis (C3, C4, CAM) have an advantage and why? Compare water use efficiencies, structure, form of organic compound that first captures CO2, timing of photosynthesis, photorespiration, maximum growth rates, CO2 limitation, light intensity optima, and geographic distributions. Use diagrams and graphs.

. C3: Temperate environments because they have no means to separate CO2 fixation and the Calvin cycle. a. C4: Tropical environments (moderately hot and dry) because they use a 4-carbon compound to effectively concentrate CO2 around Rubisco so it is less likely to bind to oxygen. b. CAM: Arid environments (extremely hot and dry) because they are able to open their stomata at night to collect CO2 so there is not as much water loss.

42. Why aren't there many (any) C4 plants in cool areas (high latitudes)?

. C4 plants utilize an enzyme in their mesophyll cells to accomplish photorespiration, but in the process, require more ATP, which means that C4 plants are efficient only in certain hot climates.

What is the difference between C4 and CAM plants?

. C4-Oxaloacetate is pumped to the bundle sheath cells, which surround the leaf vein. There, it releases the CO2 for use by Rubisco. By concentrating CO2 in the bundle sheath cells, C4 plants promote the efficient operation of the Calvin cycle and minimize photorespiration. a. CAM-Instead of fixing carbon during the day and pumping oxaloacetate to other cells, CAM plants fix carbon at night and store the oxaloacetate in large vacuoles within the cell. This allows them to have their stomatas open in the cool of the evening, avoiding water loss, and to use the CO2 for the Calvin cycle during the day, when it can be driven by the sun's energy.

22. What is cellular respiration? Where does it take place?

. Cellular respiration is the process in which plants take in glucose and oxygen and give out carbon dioxide and water and releases energy. Plants respire at all times of the day and night because their cells need a constant energy source to stay alive. a. Cellular respiration takes place in the cytosol (glycolysis) and in the mitochondria (Krebs cycle and electron transport chain).

What is the difference between diaheliotropic and paraheliotropic plants? Advantages of the movements?

. Diaheliotropic-plant species whose leaves orient themselves perpendicularly to the sun's rays in the morning (receive maximum sunlight). Paraheliotropic-plant species whose leaves orient themselves parallel to the sun's rays at midday (minimize surface exposure to the sun). a. Advantages of the movements-Diaheliotropic: increase radiation interception, enhance photosynthesis, increase growth rates of plants. Paraheliotropic: reduces dehydration by reducing leaf temperatures and water loss.

49. What environmental factors increase transpiration rates?

. Light, higher temperatures, higher humidity, negligible wind, constantly replaced soil water.

33. Describe the components of soil, their roles, and their relative abundances.

. Mineral soil particles-retain and supply nutrients; 45%. a. Humus-decomposing organic matter, increases water and nutrient holding capacity; 1-10%. b. Air-oxygen needed by the roots; 25-50% by volume. c. Water-keeps plants cool and act as the medium from which all nutrients are assimilated by the plant; 25%. d. Living organisms-"intestines of the Earth"- earthworms can digest 1 ton/year; 0.1% by weight.

54. What is bulk flow? How is it related to the movement of photosynthate in phloem?

. Movement of water and solutes together due to a pressure gradient. a. The high turgor pressure drives movement of phloem sap by bulk flow from source to sink (points of sugar delivery such as the roots), where the sugars are rapidly removed from the phloem at the sink.

50. What are four physiological adaptations of plants in dry environmental conditions?

. New seeds remain in their protective coverings longer, CAM photosynthesis, store water in fleshy leaves, can idle metabolism during droughts.

32. Describe a typical soil profile. How does a prairie soil differ from a forest soil?

. O horizon (dead organic litter), A horizon (rich humus), E horizon (concentrated plant roots, leeching materials), B horizon (little organic materials, clay minerals), C horizon (weakly altered, Ca and Mg carbonates), bedrock (unaltered rock, parent material). a. Prairie soils have a deeper A horizon (topsoil) because the deep roots last about a year or two after they die until the grass plant replaces them with new roots. This leaves behind easily broken down organic matter throughout several feet of soil. Forest soils have thinner A horizons, because most of the organic matter that trees add to the soil is through leaf fall at the surface. A second difference is that forest soils tend to be more acidic than prairie soils. Leaf litter is more acidic, and the higher rainfall in forested areas washes out basic soil cations.

25. When do plants respire? When is the respiration rate the highest? Will plants respire in the dark?

. Plants always respire. a. They respire more at night, because - they do it then instead of in the day because they do photosynthesis during the day, but they still respire a little bit. b. Yes, plants will respire in the dark.

46. What is turgor pressure? How is it maintained? What happens when the water potential due to turgor pressure=0?

. Pressure from fluid within the cell pushing against the cell wall. a. Turgor pressure is maintained via osmosis and transpiration. b. The hydrostatic pressure in the cell sap is equal to the atmospheric pressure meaning that no net force is exerted on the cell wall.

19. What are the various adaptations that shade leaves may develop?

. Shade leaves are typically larger in area, but thinner than sun leaves; shade leaves generally have more chlorophyll; the chloroplasts move within the cells to take up a position where they will absorb the maximum light without shading other chloroplasts below them.

51. What are five structural adaptations of plants in dry conditions?

. Shallow roots, stems heavily waxed to prevent water loss, leaves reduced to spines to increase the volume to surface ratio, stomatas open in the cool of night, collect water in blossoms and let stems shrivel out.

53. Explain how sugars move in plants. Why are they transported as di- and oligosaccharides rather than monosaccharides like glucose?

. Sugars produced in sources, such as leaves, need to be delivered to growing parts of the plant via the phloem in a process called translocation, or movement of sugar. The photosynthates from the source are usually translocated to the nearest sink through the phloem sieve tube elements. The pressure flow model works like this: a high concentration of sugar at the source creates a low solute potential, which draws water into the phloem from the adjacent xylem. This creates a high turgor pressure in the phloem. The high turgor pressure drives movement of phloem sap by "bulk flow" from source to sink, where the sugars are rapidly removed from the phloem at the sink. Removal of the sugar increases the solute potential, which causes water to leave the phloem and return to the xylem, decreasing the pressure potential. a. Sugars are transported as di- and oligosaccharides because they are more complex molecules which allows them to be water soluble and more efficient in energy storage. Because of their complexity they are also not as reactive as monosaccharides.

37. What is the Emerson Effect?

. The Emerson Effect is the increase in the rate of photosynthesis after chloroplasts are exposed to light of wavelength 680 nm and more than 680 nm. When simultaneously exposed to light of both wavelengths, the rate of photosynthesis is far higher than the sum of the red light and far red light photosynthesis rates.

36. Why is the action spectrum of photosynthesis not totally predictable by the absorbance spectra of the pigments involved?

. The Emerson Effect.

20. What is the first layer of soil called? What are the layers of a soil profile?

. The first layer of soil is called the O horizon. a. O horizon (surface litter), A horizon (topsoil), E horizon (zone of leaching), B horizon (subsoil), C horizon (parent material), and bedrock.

34. How does the size of the mineral particles in soil affect availability of water, oxygen, and nutrients for plants? Discuss how soil texture and structure affects plant growth.

. The larger mineral particles are less efficient at providing the plant with water, oxygen, and nutrients because the pores are too large to retain these properties. a. Coarse textured soils (sands and loamy sands) have large pores with limited ability to retain water. Although fine textured soils have the highest total water storage capacity due to large porosity values, a significant fraction of water is held too strongly (strong matric forces/low, negative water potentials) for plant uptake. Fine textured soils (clays, sandy clays and silty clays) have a pore size distribution consisting mainly of micropores. Loamy textured soils (loams, sandy loams, silt loams, silts, clay loams, sandy clay loams and silty clay loams) give rise to a wide range in pore size distribution that results in an ideal combination of meso- and micro-porosity.

52. What is translocation?

. Translocation is the movement of sugars from the leaves to other tissues.

48. What is transpiration? It is often called a necessary evil. Does it have any benefits to a plant?

. Transpiration is the process by which moisture is carried through plants from the roots to small pores on the underside of the leaf where it is changed to vapor and released to the atmosphere. a. Yes, it moves water and nutrients up from the roots, assists in cooling the plant, and helps maintains turgor pressure.

During which of the three major pathways of psn do stomata open at night?

CAM

How does chloroplast movement affect the absorption of light?

Chloroplasts move towards weak light to capture light efficiently (the accumulation response) and they escape from strong light to a position where light absorption is minimized ( the avoidance response)

2. Typically, the photosynthesis rate of a plant has a "dip" in the middle of the day. Why is this? Which type of photosynthesis doesn't usually experience this? What other adaptations do plants have that can reduce this dip?

During the middle of the day, the sun and heat is at its most intense. To stop themselves from loosing too much water, leaves will close their stomata or even curl up. When the stomata are closed, CO2 cannot enter the leaf and eventually it will run out. Rubisco will instead grab oxygen and start smashing that. It will tear things apart and create molecules that are unnecessary to the plant and will later have to be broken down. No energy is made.--Also called photorespiration.

16. Why is the biochemical pathway of photosynthesis not really light independent? (Why is it more appropriate to talk of the photochemical reactions and biochemical reactions of photosynthesis rather than the light and dark reactions?)

In order for the light independent reactions to occur, the light dependent reactions have to occur first meaning that light is still essential to create the molecules needed for the biochemical reactions.

g. Glycolysis:

Location-Cytosol. Main products-Pyruvate, NADH, and ATP.

h. Fermentation

Location-Cytosol. Main products-carbon dioxide, ethanol, and energy.

f. Electron acceptance of oxygen

Location-Electron transport chain of respiration.

CAM

a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions. The stomata in the leaves remain shut during the day to reduce evapotrasperation, but open at night to collect carbon dioxide

Photochemical Reactions

a chemical reaction initiated by the absorption of energy in the form of light

What is dark respiration

a form of respiration where carbon dioxide is realease without the aid of sunlight

Fermentaion

a metabolic process that consumes sugar in the absence of oxygen. The products are organic acids, gases, or alcohol.

C4

a plant that cycles carbon dioxide into four-carbon sugar compounds to enter into the Calvin cycle. These plants are very efficient in hot, dry climates, and produce a lot of energy.

Photorespiration

a respiratory process in many higher plants by which they take up oxygen in the light and give out some carbon dioxide, contrary to the general pattern of photosynthesis.

Kreb Cycle

a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-CoA into ATP and Carbon Dioxide

8. What are the three major biochemical pathways in photosynthesis? How can you tell by looking at a leaf cross section if it is a C4?

a. CAM, C3, C4 b. the bundle sheath cells surrounding the veins found in the leaves are photosynthetic in the C4 plant; whereas they are not photosynthetic in the C3 plants.

Why is it sometimes said that CAM plants photosynthesize at night?

at night, CAM plants open their stomata to collect water because it is cooler and not as dry which means less evaporation will occur. Even though they get the carbon dioxide they need at night, they still need light to do psn. Thus they store the CO2 collected at night in the form of a chemical called manic acid until it can be used the next day.

Chemiosmosis

generation of ATP by the movement of hydrogen ions across a membrane during cellular respiration or photosynthesis; ions moving down their electrochemical gradient

35. Name 7 essential macronutrients and 3 micronutrients and tell what each is necessary for.

i. Carbon, hydrogen, oxygen-important in photosynthesis and cellular respiration. ii. Nitrogen-present in the protein molecule, RNA, and DNA. Also important in energy molecules such as NAD and NADP. iii. Phosphorus-present in RNA and DNA, phospholipids, and energy molecules such as ATP and ADP. iv. Potassium-carbohydrate metabolism, essential for the translocation of sugar, required for stomatal opening, regulation of water, involved in enzyme activity. v. Calcium-associated with cell wall structures, involved in ion regulation, required for successful nitrogen fixation,in guard cells. vi. Magnesium-component of chlorophyll structure, activator for maximum photosynthesis and carbohydrate metabolism activity. vii. Sulfur-constituent of certain amino acids and coenzyme A which is involved in cellular metabolism. a. Micronutrients: . Iron-constituent of several enzymes and some pigments, essential for the synthesis of chlorophyll, assists in sulfate and nitrate reduction. i. Boron-cell wall strength and development, cell division, fruit and seed development, sugar transport, and hormone development. ii. Copper-activates some enzymes, required in the process of photosynthesis, essential in cellular respiration, and assists in plant metabolism. iii. Zinc-a key constituent of many enzymes and proteins, important in processes such as growth hormone production and internode elongation. iv. Chloride-opening and closing the stomata, chemically balances the potassium ion, and transport.

What is Rubiscos role in psn?

it is an enzyme involved in the first major step of the Calvin cycle which is carbon fixation. During this process atmospheric carbon dioxide is converted to energy rich molecules such as glucose.

27. How do plant roots get oxygen?

lls in the roots often need to get oxygen from the environment to stay alive. Even though roots are buried, they can absorb oxygen from the small air spaces in soil.

Calvin Cycle

part of the light independent reactions of psn that takes place in the stroma of the chloroplasts in which carbon atoms from CO2 are fixed (incorporated into organic molecules) and used to build three ringed sugars

Dark Respiration

respiration in plants that occurs regardless of lights

Phosphorylation

the addition of a phosphoryl group which allows cells to accumulate sugars because the phosphate group prevents the molecules from diffusing back across their transporter. Phosphorylation of glucose is a key reaction in sugar metabolism because many sugars are converted to glucose before being metabolized further

Kranz anatomy

the special structure of leaves in C4 plants where the tissue equivalent to the spongy mesophyll cells is clustered in a ring around the leaf veins outside the bundle-sheath cells.

Carotenoids play at least two significant roles in plants, what are they?

they absorb light energy for the use of photosynthesis they protect chlorophyll from photo damage

aerobic

with oxygen

anerobic

without oxygen