Problems 7-9. Perennial desert shrubs of the genus Atriplex are typically dioeci

Question

Problems 7-9. Perennial desert shrubs of the genus Atriplex are typically dioecious; they consist of separate male and female plants. Species within this genus also have varying levels of ploidy. Four-wing saltbush (A. canescens) and saltsage (A. tridentate) are wide-spread species throughout the American west. Both are fully fertile. In 1979, Stutz et al. (Amer. J. Bot. 1181-1193) reported the discovery of an isolated female four-wing saltbush plant surrounded by a large population of saltsage near the south shore of the Great Salt Lake. Chromosomes counts in the somatic cells of the saltsage population consistently yielded 2n=54. Seed collected from the isolated female four-wing saltbush plant were grown in a garden. The plants that arose from the seeds were sterile and had 45 chromosomes in the somatic cells. 7. How many chromosomes are in the somatic cells of the four-wing saltbush female plant? A. 8 B.9 C. 12 D. 13 E. 18 F. 24 G. 27 H. 36 1.45 J.54 8. What is the ploidy of the four-wing saltbush plant? A. monoploid C. triploid E. pe B. diploid pentaploid G. septaploid D. tetraploid F. hexaploid octaploid 9. What is the ploidy of the sterile progeny plants grown in the garden A. monoploid C. triploid IB. diploicl E. pentaploid G. septaploid F. hexaploidH. octaploid D. tetraploid

Explanation / Answer

7.

The somatic cells of four wing saltbush female plants consistently exhibited diploid number of chromosomes 2n = 54. Therefore, option J is correct.

8.

The four wing saltbush contained 2n = 54 chromosomes and this means, the chromosoems are two sets or diploid. The haploid set include n = 27 chromosomes. Option B is correct.

9.

Sterile plants had shown 2n = 45 chromosomes. This means, the haploid set might contain n = 22 and then 2n becomes 44. But somatic cells contained 45 chromosomes. Thus, the condition must be 2n+1. This means, the sterile plants are sterile. Option C is correct.

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