1.1. A scientist is investigating two substances X and Y,  which may affect the growth of ne roots from a cut plant stem. They used a ringing experiment to investigate the transport of substances X and Y through the plant stems taken from a grapefruit plant. A length of stem from each grapefruit plant was cut and then placed a small block of agar at the top of each stem as a food source. Substance X or Y was added to some of the agar blocks.

Figure 1

Table 1

Treatment 1 was used as a control for the experiment. Explain how the result from treatment 1 is used by the scientist.

1.2. Using Figure 1 and Table 1, explain the effects of substance X on root growth.

1.3. Substance Y is known to be transported through the plant via the phloem. Suggest a value for J from the table in part (a) and justify your answer.

1.4. During the experiment the scientist ensured that the temperature was constant for all the leaf stems. Suggest why this is important.