WJEC Biology for AS Level Student Book: 2nd Edition

Exam practice questions 2 The cell surface membranes of root cells are responsible for differences in the concentration of ions in the roots when compared to those found in the surrounding soil solution. Inorganic ions are essential for cell metabolism in plants. (a) Describe the role of magnesium, calcium, and phosphate ions in plant cells and tissues. [3] To investigate the uptake of mineral ions by plants, barley seedlings were grown with their roots in a solution of mineral ions for four days. Air was bubbled through the solution. The concentration of the ions in the solution and the root tissue were determined. Ion Ion concentration / mmol dm –3 Surrounding solution Root tissue Calcium (Ca 2+ ) 1.0 57.0 Magnesium (Mg 2+ ) 0.3 33.0 Phosphate (PO 4 3– ) 0.9 1.6 (b) (i) With reference to the data, explain the relative concentrations in the surrounding solution and the root tissue after four days. [3] (ii) Explain why the growth of a barley seedling may be reduced if the solution did not have air bubbled through it. [4] (Total 10 marks) [© WJEC Unit 1 2017 Q6 ] WJEC Biology for AS Level 134