The researchers studied how using special bacteria and zinc fertilizer can affect the growth and quality of marigold plants. They tested different ways of applying the bacteria and zinc to see which combination worked best. They found that plants treated with the bacteria and a moderate amount of zinc grew the tallest and had the heaviest flowers. These plants also had the highest levels of certain nutrients and compounds that make the flowers colorful and healthy. Overall, using the bacteria and zinc together can make marigold plants grow better and produce more vibrant flowers.