Re: I read of capillary action in cut plants. I am trying it in a plant in soil

Complete question:

I am putting red food color directly into the soil. It has been a week. 
How come it won't turn red like the celery did? I need an answer for my 
science project due real soon. I don't see any red growing up the stem. Is 
this still called capillary action? Will it grow up soon?

Response:

In science, your hypothesis will not always be correct but that does not 
matter. You still have experimental results to report. Your results indicate 
that the food coloring cannot enter an intact plant. Food coloring entry 
requires that the stem or root be cut so the food coloring can enter the cut 
end of the plant xylem, the little tubes in the plant that carry water upward.

What you might want to do at this point is to cut off one of your plants and 
see if the dye will move up the cut stem. That will confirm that movement of 
food coloring can occur in the type of plant you are using if the stem is cut.

Capillary action is not really responsible for upward movement of water in 
intact plants or food coloring in cut stems of living plants. Capillary action 
occurs in initially empty, small diameter tubes with both ends open. The empty 
tube is stood upright with the bottom end just under the surface of water, and 
water moves up the empty tube. The smaller the tube diameter, the higher the 
water rises. Unless you cut both the top and bottom of the stem and the plant 
xylem is empty of water to begin with, in which case the plant would most 
likely be dead, then it does not meet the conditions for capillary action.