19. Which of the following statements about the polarity of an embryo is FALSE?
(A) It fixes the structural axis of the body.
(B) It is established only after the zygote has divided.
(C) It is essential to the development of all higher organisms.
(D) It refers to the condition in which one end is different from the other end. It is a key component of biological pattern formation.

15. In photosynthetic pathway, compared to C3 plants, C4 plants (A) have the higher rate of photorespiration. (B) only use PEP carboxylase for carbon fixation. (C) have specialized bundle sheath cells. (D) do not use rubisco for carbon fixation. (E) are adapted to life in the temperate climate.

16. It is usually advantageous to a species if the offspring of a sporophyte are genetically different than the parent sporophyte. Which of the following would be the least likely to ensure genetically different offspring? (A) Pistil and stamens within a flower mature at different times. (B) The pollen produced on a plant cannot germinate on stigmas on the same plant. (C) The species is dioecious. (D) The species is monoecious. (E) The plant is pollinated by bees.

17. Which of the following statements about apoplastic phloem loading is FLASE? (A) It is driven by a proton gradient. (B) The mechanism is sucrose-proton co-transport. (C) The sieve tube provides much of the energy for transport. (D) In some cases. Active transport occurs across the plasma membrane of the sieve tube. (E) In some cases. Active transport occurs across the plasma membrane of the companion cell. O

18. In a vascular plant, the least amount of resistance occurs as water moves between: (A) tracheids through pit-pairs. (B) tracheids through perforations. (C)tracheids through plasmodesmata. (D) vessel elements through pit-pairs. (E) vessel elements through perforations.

20. Which of the following would not typically cause coat-imposed dormancy? (A) impermeability of the seed coat to water. (B) impermeability of the seed coat to oxygen. (C) prevention of the release of growth promoters from the seed. (D) rigidity of the seed coat. (E) prevention of the release of growth inhibitors from the seed.

21. Which of the following statements concerning strigolactone is FALSE? (A) It is a terpenoid derived from carotenoids. (B) It stimulates bud growth. (C) It is present in root exudates. (D) It promotes the formation of mycorrhizae. (E) It stimulates seed germination of root-parasitic plants.

22. The subapical meristem produces young cells of the pith and cortex called: (A) protoderm (B) provascular tissue. (C) ground meristem. (D) metaxylem (E) protoderm and ground meristem.

23. Why would a gene for cytokinin synthesis be fused to a promoter that is expressed only in senescent leaves? (A) to delay leaf senescence. (B) to confer resistance to herbicides. (C) to confer resistance to BT toxin. (D) to increase starch content. (E) to increase glyphosate production.

24. Which of the following crops was NOT initially cultivated in the New World? (A) maize. (B) common beans. (C) barley. (D) lima beans. (E) peanuts.

25. The pedicel of a flower is: (A) a leaflike structure that contains the ovules. (B) the part of the flower stalk to which flower parts are attached. (C) the stalk of a flower or an inflorescence. (D) the stalk of a flower in an inflorescence. (E) the stalk that attaches an ovule to the ovary.