A greenhouse experiment to test growth rates in tomato cultivars was conducted using sterile soil mix and watering with sterile solutions of water and fertilizer. Following germination, half of the plants in each group were transplanted into soil that was obtained from a nearby agricultural field (nonsterile) and the other half into sterile soil. After several weeks the plants that were transplanted into nonsterile soil exhibited a much higher growth rate compared to the plants transplanted into sterile soil. The most likely explanation for this result is

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The most likely explanation is that the plants transplanted into the nonsterile soil were inoculated with mycorrhizae. Mycorrhizae are beneficial fungi that form a symbiotic association with plant roots and enhance nutrient uptake, leading to improved plant growth. Since the nonsterile soil came from an agricultural field, it is likely that it already contained mycorrhizae, while the sterile soil did not. This would explain the observed difference in growth rates between the two groups of plants. Option B is not a likely explanation, as the sterile solutions of water and fertilizer were used for both groups of plants. Option C and D are not likely explanations either because overfertilization and improper water drainage would have affected both groups of plants equally, rather than just the ones transplanted into sterile soil.

A Greenhouse Experiment to Test Growth Rates in Tomato Cultivars