You are growing plants hydroponically (rooted in an aqueous solution rather than soil). For one group of plants, the solution for the "control group" contains normal levels of salts and nutrients, while the solution for the "treatment group" has a high concentration of large molecular weight solutes that are excluded by roots. You find that the plants in the treatment group are on average smaller than those in the control group, but there is no significant difference between the groups in the amount of CO₂being fixed by the average plant. What differences at the cellular level between groups would you expect to make an important contribution to the difference in size of the shoots?

Question

Quizplus · Accepted Answer

The high concentration of large molecular weight solutes in the treatment group solution would restrict the movement of water and nutrients to the roots, resulting in smaller and fewer cells in the elongation and mature zones of the shoots. This would lead to shorter cells and smaller shoots in the treatment group, compared to the control group. The girth of cells and orientation of cellulose molecules in cell walls are unlikely to have a significant effect on shoot size. However, the lower auxin levels and cell wall extensibility in the treatment group could also contribute to the smaller shoot size.

You Are Growing Plants Hydroponically (Rooted in an Aqueous Solution