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.
8. What is the most likely reason that 7 seedlings were removed from each pot in Step 3 ?
Your Answer is
Correct Answer is G
Explanation
General knowledge questions.
Examine common sense, so the answer cannot be found in the article and the chart. After the seeds germinate, the seedlings are thinned out (that is, some of the weaker seedlings are pulled out) in order to select stronger plants and allow the stronger plants to have enough growth space and resources.