Cost and Advantage of Soil Channel Formation by Contractile Roots in Successful Plant Movement

In most cases, contractile roots not only produce a pulling force on an underground plant (bulb, corm), but also push away the substratum and create a soil channel in which plant movement is made easier. Two specially-constructed experimental set-ups allowed the pulling and pushing activity of contractile roots in underground plant movement to be measured under identical standard conditions. Our results show that root channel formation is always advantageous for the accomplishment of movement. The extent of channel formation in relation to the size of the bulb or corm being moved was calculated as a percentage channel effect. A value of 100% indicates a channel effect sufficient to allow plant movement with no resistance. For smaller distances moved (20-30 mm) a small channel effect (10-40%) was found to be very efficient. For more extensive movement (> 50 mm) a 100% channel effect seems to be the optimum energetically. These systems of movement commonly exist in nature.