To find the greatest number of plants you can put in one row, you need to find the greatest common divisor (GCD) of the number of sunflower plants, corn plants, and tomato plants.
In this case, the number of sunflower plants is 45, the number of corn plants is 81, and the number of tomato plants is 63.
To find the GCD, you can list the factors of each number and find the largest factor that is common to all three numbers.
The factors of 45 are: 1, 3, 5, 9, 15, and 45.
The factors of 81 are: 1, 3, 9, 27, and 81.
The factors of 63 are: 1, 3, 7, 9, 21, and 63.
The largest factor that is common to all three numbers is 9.
Therefore, the greatest number of plants you can put in one row is 9.