ABSTRACT
The development of roots is at least as sensitive to ethylene as that of other plant parts, and root tissues produce the gas in amounts that often reflect conditions at the root-soil interface. Ethylene may, therefore, be especially influential in fashioning the root system. This chapter utilizes findings from research with roots that have increased the understanding of the biochemical or molecular biological basis of ethylene formation or action. The same laboratory also reported that a range of naturally occurring and synthetic auxins stimulate both rooting and also ethylene evolution, as detected by bioassay. Inhibition of extension growth of roots on intact plants by the addition of sufficient ethylene is usually accompanied by increased radial expansion, leading to shorter, fatter roots, which often produce many additional root hairs although excised, cultured roots can behave differently. Auxin obviously has the ability to inhibit root growth strongly and independently of ethylene, although any additional gas generated may add to the effect.
