Effects of Ethylenediaminetetraacetic Acid, Auxin and Gibberellic Acid on Phytochrome Controlled Nyctinasty in Albizzia julibrissin

Nyctinastic closure of Albizzia julibrissin pinnules is inhibited by 5 × 10^?2M ethylenediaminetetraacetic acid. At least two hours of incubation are required for maximum inhibition and destruction of the phytochrome effect. Concentrations of 10^?3 to 10^?5M naphthaleneacetic acid reduced the nyctinastic closure of pinnules but not the phytochrome response. Similar results were obtained with indoleacetic acid and gibberellic acid. No appreciable differences in pinnule movements could be attributed to pH. Chelation or the inhibition of ion transport resulting in, or caused by, changes in membrane permeability are suggested as possible mechanisms involved in these effects.