The effects of a short‐day treatment on pool‐size, synthesis, degradation, and transport of 3‐indole‐acetic acid (IAA) in Scots pine (Pinus sylvestris L.) seedlings were studied. The short‐day treatment decreased the pool of free IAA in the needles but did not significantly affect the pool‐sizes of free IAA in the shoot‐axis, hypocotyls, cotyledons and roots. The bound alkali‐hydrolysable IAA‐pools were not affected by the short‐day treatment. The synthesis and degradation of radioactive IAA were also unaffected by the short‐day treatment. The transport of radioactive IAA was greatest from needles to roots, and this transport was significantly decreased by the short‐day treatment.