Question 13 Answer and Explanation _ACT December 2016 Form 74H Science Section

Passage II

Triticum aestivum wheat plants grown in a particular soil are affected by salt (NaCl) in the soil, overwatering of the soil, or both. A study examined the effects.

The following 5 steps were performed:

1. Forty identical pots were divided equally into 4 groups (Groups 1—4).

2. Five kilograms (kg) of the soil was put into each Group 1 pot and each Group 3 pot. A mixture of 4.98 kg of the soil and 20 g of NaCl was put into each Group 2 pot and each Group 4 pot.

3. Ten wheat seeds were planted in each pot and watered daily until all the seeds sprouted. Then 7 of the 10 seedlings were removed from each pot.

4. Over the next 4 months, all the pots received the same amount of sunlight and the same amounts of nutrients daily. Each Group 1 pot and each Group 2 pot received 500 mL of water daily. Each Group 3 pot and each Group 4 pot received 500 mL of water daily, except for 3 consecutive weeks during the third month. Over that 3-week period, each Group 3 pot and each Group 4 pot was overwatered by keeping the water level 1 cm above the top of the soil.

Table 1 describes the differences among the groups.

5. At 4 months, 2 averages were calculated for the plants in each group of pots: the average plant mass (roots included), in g per plant, and the average grain yield (mass of grain produced), in g of grain per plant.

The average plant mass results are shown in Figure 1. and the average grain yield results are shown in Figure 2.

Figures adapted from Muhammad Saqib, Javaid Akhtar, and Riaz Hussain Qureshi, "Pot Study of Wheat Growth in Saline and Waterlogged Compacted Soil: [Part] I. Grain Yield and Yield Components."©2004 by Elsevier B. V.

13. The researchers who performed the study most likely compared the results shown in Figure 1 for the Group 1 pots and the Group 2 pots to answer which of the following questions?

A. What effect did NaCl alone have on average plant mass?

B. What effect did NaCl alone have on average grain yield?

C. What effect did overwatering alone have on average plant mass?

D. What effect did overwatering alone have on average grain yield?

Answer and Explanation

Your Answer is

Correct Answer is A

Explanation

Looking at table 1, the difference between Group 1 and Group 2 is that Group 2 has NaCl, so comparing these two experimental groups can see whether NaCl alone will have an impact on the results. The ordinate of Figure 1 is the average plant mass, so the comparison result is the effect of NaCl alone on the plant mass.

Figures adapted from Muhammad Saqib, Javaid Akhtar, and Riaz Hussain Qureshi, "Pot Study of Wheat Growth in Saline and Water­logged Compacted Soil: [Part] I. Grain Yield and Yield Compo­nents."©2004 by Elsevier B. V.

Figures adapted from Muhammad Saqib, Javaid Akhtar, and Riaz Hussain Qureshi, "Pot Study of Wheat Growth in Saline and Waterlogged Compacted Soil: [Part] I. Grain Yield and Yield Components."©2004 by Elsevier B. V.