|MadSci Network: Botany|
Cut flowers are often dyed by placing the stems in a dye solution. However, flowers and leaves of intact plants probably cannot be dyed by watering them with a dye solution because the dye solution is not absorbed by the intact roots. Roots are very selective in what they absorb and generally only absorb water and mineral nutrients. Cut flowers have the roots removed so the dye can easily enter the cuts in the water-conducting tubes (called xylem). If you want to do an experiment with dyes and plants, you might compare a soil-grown plant with a cut flower. If you grew a plant in hydroponics and carefully cut the tips off many of the roots, then maybe you could get dye to enter. However, unless the plant was in flower or the leaves of the plant are mainly white, like in a variegated spider plant, it might be difficult to see a color change in the leaf even if the dye entered. I once potted chrysanthemum cuttings in potting soil and watered them with a fertilizer solution containing a red iron chelate. I noticed a little red coloring in the leaf tips because some of the roots had been damaged and the chelate could enter the xylem. One plant whose flower color can be changed by the chemical composition of the soil is the florist hydrangea. Making the soil pH acid by adding aluminum sulfate or sulfur causes blue flowers. Keeping the soil pH high makes the flowers pink. The aluminum absorbed by the flower causes the pigment in the flower to change to blue. Aluminum is unavailable to the plant at a high pH. One way to make plants change color is to grow them in hydroponics and deprive them of one or more mineral nutrients. For example, iron deficient plants often turn from green to yellow or white because of iron deficiency. References Re: Can all white flowers be turned color with food coloring the water? Re: ARE ANY FLOWERS NATURAL INDICATORS OF THE ACIDITY OF THE SOIL? Re: Capillary action in flowers with hot water? Hydrangea and soil pH
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