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1973 1977 1983 1984 1985 1987 1988 1990
PLANT SYSTEMS QUESTION 1973: L. PETERSON/ECHS Seeds that are randomly positioned when planted in a pot of soil placed on a window sill produce seedlings with downward growing roots and upward growing shoots. Above ground, the shoots are oriented toward light. Describe the physiological mechanisms that occur to produce: a) the downward growth of the roots b) the upward growth of the shoots c) the bending of the shoots toward light STANDARDS: NOT MORE THAN FIFTEEN TOTAL POINTS WERE GIVEN. ONE POINT FOR EACH OF THE FOLLOWING: __ The hormone involved is auxin. __ In vertical roots or stems, auxin is uniformly distributed. __ In horizontally placed roots, auxin accumulates on the lower side. __ The accumulation of auxin on the lower side in roots inhibits cell elongation in the area. __ In horizontally placed stems, auxin accumulates on lower side. __ Accumulation of auxin in stems is stimulatory. __ In a laterally illuminated stem, auxin accumulated on the shady side. __ There is lateral transport of auxin from the sunny to the shady side, or from top to bottom in horizontally placed stems and roots. TWO POINTS FOR EACH OF THE FOLLOWING: __ Auxin is produced in the stem apex. __ Auxin causes cell elongation in stems. __ Optimum for root growth is an amount much less than for stem growth. __ In high concentration, auxin is inhibitory in both stems and roots. __ Lateral movement of auxin requires energy. __ Auxin movement is too fast to be explained by diffusion. __ The perception of auxin in stem tips is light promoted (carotenes or flavenes). __ Discussion of the perception of gravity. __ Evidence that the site of perception is the tip. FIVE POINTS FOR THE FOLLOWING: The downward growth of roots...the geotropic response of root is dependent on the production of a growth inhibitor or inhibitors produced in the root cap. The inhibitor(s) move from the cap through the apex to the elongating cells. If the root is horizontal, a large part of the sub- stance is transported laterally to the lower side. The difference in concentration produces unequal growth,...the lower side is more inhibited and root therefore turns down.
PLANT SYSTEMS QUESTION 1979: L. PETERSON/ECHS In relation to plants, describe in detail one way of: a) measuring the rate of transpiration b) measuring the rate of photosynthesis c) separating pigments STANDARDS: A. TRANSPIRATION: Max. = 6 points __ a functional and structural definition of transpiration __ factors affecting rate in vivo (2 points) __ mention method of measurement (2 points) __ method discussed in some detail (3 points) B. PHOTOSYNTHESIS: Max. = 6 points __ definition by equation or by statement of function __ factors affecting rate in vivo (2 points) __ naming a possible method of determining rate (2 points) __ method discussed in some detail (3 points) __ rate of disappearance of CO2 or rate of appearance of CHO or O2 C. PIGMENT SEPARATION: Max. = 6 points __ separation method mentioned (2 points) __ separation method discussed (3 points) __ pigment composition __ pigment function __ molecular characteristics of pigments
PLANT SYSTEMS QUESTION 1983: L. PETERSON/ECHS Relate the structure of an angiosperm leaf to each of the following: a) Adaptations for photosynthesis and food storage b) Adaptations for food translocation and water transport c) Specialized adaptations to a desert environment STANDARDS: PART A __ Cuticle transparent to allow light in __ Palisade Parenchyma - site of photosynthesis __ Spongy Parenchyma - site of photosynthesis __ Altered leaf shape + Photosynthetic efficiency __ Stoma controls passage of gas and water __ Turgor pressure controls guard cell behavior PART B __ Xxlem transports water to leaf tissue __ Phloem transports "food" from leaf tissue to sink __ Bulk-mass flow mechanism of phloem movement __ Transpiration defined PART C __ Small leaves __ Altered stoma behavior __ Specialized physiology (4C) __ Details of oxaloacetate
PLANT SYSTEMS QUESTION 1984: L. PETERSON/ECHS Define the following plant responses and explain the mechanism of control for each. Cite experimental evidence as part of your discussion. a) Phototropism b) Photoperiodism STANDARDS: PHOTOTROPISM: Max. = 9 points if experimental evidence is given Max. = 7 points if experimental evidence is lacking __ Definition - movement in response to light (involving growth) - 2 points __ Possibility of negative response Mechanism __ Auxins __ Distribution (apex -> stem or lateral) __ elongation of cells __ stem tip or coleoptile Evidence (2 points for any of the following) __ Darwin - covered coleoptiles __ Paal - cut coleoptiles - agar, uneven placement __ Boysen-Jensen - mica __ Went - bioassay PHOTOPERIODISM: Max. = 9 points if experimental evidence is given Max. = 7 points if experimental evidence is lacking __ Definition - response to light/dark periods __ flowering (or other response) Mechanism __ Categories of plants (LDP, SDP) __ Receptor in leaf __ LDP (if night shorter than minimum) __ SDP (if night longer than minimum) __ night not day __ existence of phytochrome in two forms __ PFR/PR interconvertible __ PFR active form __ ratio (PR/PFR) important __ possible hormonal involvement Evidence __ light flash in dark __ grafting __ ratio of PR/PFR
PLANT SYSTEMS QUESTION 1985: L. PETERSON/ECHS Describe the structure of a bean seed and discuss its germination to the seedling stage. Include in your essay hormonal controls, structural changes, and tissue differentiation. STANDARDS: STRUCTURE: Max. = 8 points __ Seed coat (protection) __ Embryo (new plant) __ Cotyledons (store food) __ Epicotyl (new shoot) __ Hypocotyl (new stem/root) __ Radicle (1st root) __ Plumule (1st leaves) __ Hilum scar (attachment) __ Micropyle (pollen tube entry) GERMINATION DISCUSSION: Max. = 12 points __ Imbibition of water (increases metabolism) __ Correct temperature (enzymes) __ Oxygen (for respiration) __ Radicle emerges 1st (establishes root) __ Subsequent shoot (photosynthesis when stored food gone) __ Formation of hook/arch (pulls epicotyl) __ Epigeal germination a. Hormonal Control -- Auxin in geotropism (+ or -) -- More auxin, lower 1/2 axis -- Stem/root affected differently -- Gibberellins stimulate length growth -- Cytokinins stimulate cell division -- Abscisic acid inhibits root cell elongation b. Structural Changes (Note: some germination discussion is structural change) -- Formation of root cap -- Dropping spent cotyledons -- Change, dark-to-light-growth -- Branch root production -- Leaf primordia -- Two different foliage leaves c. Tissue differentiation -- Cell division, elongation, maturation -- Xylem, phloem (elaboration) -- Apical meristem -- Protoderm, ground meristem, procambium -- Several vascular strands, stem; one, roots -- Collenchyma, sclerenchyma -- Mesophyll, epidermis, guard cells -- Endodermis pericycle -- Root hair formation
PLANT SYSTEMS QUESTION 1987: L. PETERSON/ECHS Describe the effects of plant hormones on plant growth and development. Deisgn an experiment to demonstrate the effect of one of these plant hormones on plant growth and development. STANDARDS: PART I. EFFECTS: Max. = 7 points __ For identifying a plant hormone __ For correctly defining a plant hormone For correctly describing the effects of a plant hormone (most frequently mentioned hormones and effects given below, but see addendum for a more complete master list): AUXINS __ Promote cellular elongation __ Promote softening of cell walls __ Involved in phototropism __ Involved in geotropism __ Involved in apical dominance GIBERELLINS __ Stimulate cell elongation __ Produce bolting in biennials __ Stimulate production of starch digestion enzymes in some seeds __ Reverse effects of genetic dwarfism CYTOKINETINS __ Promote growth in size of leaf cells __ Stimulate cell division __ Release buds from apical dominance ETHYLENE __ Promotes ripening of fruit ABSCISIC ACID __ Promotes stomatal closure __ Promotes resistence to water stress __ Promotes seed and bud dormancy __ formerly thought to promote abscission FLORIGEN __ May induce flowering Extra points, up to two, awarded for each association of a hormone with a correct, specific effect. In order for two points to be awarded, two different hormones must be associated with their specific effects. PART II. EXPERIMENTAL DESIGN Max. = 7 points Appropriate understanding or indication of: __ Basing design on past observations or the literature __ Problem, statement, or question posed __ Hypothesis __ Use of adequate sample size or replicates __ Maintaining uniform conditions __ Control or understanding of the concept of control __ Treatment of experimental group __ Taking of data __ Evidence supports or refutes the hypothesis One extra point awarded for a particularly innovative experimental design and another for especially well organized and detailed description of the experiment. (Max. = 2 points) ADDENDUM TO STANDARDS / MASTER LIST OF PLANT HORMONAL EFFECTS: AUXINS GIBBERELLINS promote cellular elongation stimulate cell elongation in stem promote phototropism in stems promote bolting and flowering in biennials promote softening of cell walls promote production of starch digesting enzymes promote growth of branch or adventitious roots in grass seeds promote renewed cell division in cambium promote pollen germination promote differentiation of vascular tissue increase size of grapes and loosen clusters promote joining of vascular tissue of leaves break seed and bud dormancy with that of stems stimulate leaf growth in monocots affect transcription of at leaves ten genes inhibit root formation involved with growth stimulate development of "male" flower parts inhibit growth of main roots stimulate auxin production inhibit production of abscission layer stimulate cell division at the stem apex act as a herbicide for dicots may stimulate the production of auxins exert apical dominance by inhibition of cell stimulate fruit-set in some species elongation stimulate vascular cambium to produce artificially promotes parthenocarpy secondary phloem stimulates protein synthesis CYTOKININS ABSCISIC ACID (ABA) promote growth in size of leaf cells promote stomatal closure stimulate cell division promote seed and bud dormancy promote conversion of immature plastids promote resistance to water stress to chloroplasts counters effects of auxin inhibit senescence of leaves induces apical meristem to stop mitosis help break dormancy in some seeds and cytokinesis enhance flowering in some plants induces leaf primordia to form protective promote fruit development in some species bud scales release lateral buds from apical dominance keeps twigs dormant until leaching occurs involved in root geotropism by inhibiting elongation of cells on lower side ETHYLENE FLORIGEN (hypothetical) promotes ripening of fruit may induce flowering promotes radial growth in stems and roots contributes to leaf drop produces horizontal growth of stems affects sex expression in some monoecious species promotes wound healing
PLANT SYSTEMS QUESTION 1988: L. PETERSON/ECHS Trace the pathway in a flowering plant as the water moves from the soil through the tissues of the root, stem, and leaves to the atmosphere. Explain the mechanisms involved in conducting water through these tissues. STANDARDS: ANATOMY AND PATHWAY: Max. = 6 points __ Pathway....some relationship from root to leaf required for a 10 mention of "root tissue -> transport tissue -> leaf tissue e.g. root hair -> xylem -> stomata Max. 5 - Anatomy of Pathway __ Soil water or capillary water __ Root hairs or Epidermis __ Cortex or Parenchyma __ Plasmodesmata __ Endodermis __ Pericycle __ Procambium __ Xylem or Vessels or Tracheids or Vascular Bundle __ Petioles __ Mesophyll Cells or Leaf Parenchyma __ Intercellular Spaces __ Stomata or Guard Cells Max. 2 - Additional Points __ Symplastic - water moves through protoplasts, plasmodesmata __ Apoplastic - water moves along cell walls __ Elaboration of Sylem - e.g. dead cells, hollow cells, main water transport __ Casparian Strip - involvement in directional or selective flow __ 10% of water through the cuticle MECHANISMS OF WATER MOVEMENT: Max. = 6 points Explanation of Mechanism = 1 point / Name alone = 0 point __ Osmosis - diffusion of water through semipermeable membrane __ Transpiration - evaporation of water from leaf __ Cohesion - water forms chain through H bonding, molecules adhere to each other __ Adhesion - water adheres to cell walls, unlike molecules attract __ Root Pressure - water enters root due to solute accumulating in root cells, force exerted by root cells on water column __ Water potential - negative pressure in leaves; positive pressure in roots; flow is along gradient of decreasing water potential Max. 2 - Additional Points __ Root hairs - large surface area -> absorption __ Stomatal mechanism - open stomates allow transpiration/how guard cells act to regulate flow __ Stomate placement relative to rate of transpiration, effect on transpiration __ Root pressure - requires an energy dependent mineral movement into xylem __ Guttation (proof of root pressure) __ Elaboration of water potential relative to cohesion and adhesion
PLANT SYSTEMS QUESTION 1990: L. PETERSON/ECHS Discuss the adaptations that have enabled flowering plants to overcome the following problems associated with life on land. a. The absence of an aquatic environment for reproduction b. The absence of an aquatic environment to support the plant body c. Dehydration of the plant STANDARDS: A. ABSENCE OF AN AQUATIC ENVIRONMENT FOR REPRODUCTION: Max. = 4 points __ Flowers - attraction for insects - shape, color, smell, chemical, nectar. Mimicry for pollination (coevolution) __ Timing of reproduction Male __ Microspores - pollen / Reduced Gametophyte __ Lack of motility of gamete - pollen grain modification for transport e.g. light weight/structure __ Pollination - transport of male gametes, wind, insects (self-pollination) Female __ Reduced gametophyte (in megaspore or megasporangium) __ Protected gametophyte - embryo inside ovary, carpel, pistil __ Evolution of seed __ Fertilization - internal - pollen tube, endosperm __ Fruit and seed dispersal __ Seed dormancy B. ABSENCE OF AN AQUATIC ENVIRONMENT TO SUPPORT THE PLANT BODY: Max. = 4 points __ Stem - support __ Root - anchorage __ Vascular tissue - xylem fibers, tracheids, vessels, heartwood, dead tissues, phloem fibers or Vascularization __ Vines, Tendrils __ Cell wall - lignin, cell wall support, cellulose __ Cambium - secondary thickening __ Sclerenchyma - whole wall support Collenchyma - corner wall support __ Prop, buttressed roots __ Turgor pressure C. DEHYDRATION OF THE PLANT: Max. = 4 points __ Root hair, absorption __ Cuticle, wax, acellular __ Bark - suberin, cork Scales - bud protection Sepal/petals - floral part protection __ Seed coat / Pollen grain wall __ Stomates - function to control water movement __ Xylem - water transport __ Leaf/stem/root modifications (2 points max.) surface area reduction in desert plants/succulents stomates under surface leaf rolling hairs and trichomes interlocked epidermal cells hypodermis cortex - water storage or retention loss of leaves / abscission layer __ CAM/C4 plants - modified stomate functions __ seed dormancy (if not mentioned in part A)