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), 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 for the difference in growth rate between plants in sterile vs. nonsterile soil is the presence of mycorrhizae in the nonsterile soil. Mycorrhizae are beneficial fungi that form a symbiotic relationship with plant roots, increasing nutrient uptake and promoting growth. Since sterile soil lacks these fungi, the plants in sterile soil may have been at a disadvantage for growth. The difference in fertilizer or water drainage is less likely to be the cause since both groups were given the same sterile solutions of water and fertilizer.

A Greenhouse Experiment to Test Growth Rates in Tomato Cultivars