The figure below shows the results of a study to determine the effect of soil air spaces on plant growth.

-The best explanation for the shape of the growth response curve in the above figure is that

Question

The figure below shows the results of a study to determine the effect of soil air spaces on plant growth.
 
-The best explanation for the shape of the growth response curve in the above figure is that

Quizplus · Accepted Answer

The growth response curve shows that plant growth increases with increasing soil air spaces up to a certain point, after which growth levels off and then declines. This pattern is consistent with the idea that roots require oxygen for respiration and growth, and that lack of oxygen (due to low soil air spaces) can limit plant growth. Therefore, E is the most likely explanation for the shape of the growth response curve. Choice A is incorrect because while plants do need air for photosynthesis, this is more related to the presence of carbon dioxide in the air than to soil air spaces. Choice B is incorrect because nitrogen (N₂) is not typically absorbed by roots, but rather converted into other forms such as nitrate or ammonium. Choice C is also incorrect because transpiration (water loss through leaves) would not be the primary cause of reduced growth at low soil air spaces. Finally, choice D is incorrect because the growth response curve shows that increased soil air spaces do affect both root mass and top growth (stems and leaves).

The Figure Below Shows the Results of a Study to Determine