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Unformatted text preview: 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)...
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- Summer '09