PROBLEM TO BE SOLVED: To provide a short-day device readily set up in a greenhouse, easily changeable in size, and also facilitated in maintenance work for cultivation plants. SOLUTION: The short-day device is structured as follows: forming a base framework so as to be decomposable; setting up a ceiling-movable frame body 5 provided with a light-shielding sheet 8 and flexibly foldable and extendable, at the ceiling part of the base framework so that the ceiling part can be opened or closed via the light-shielding sheet 8; and attaching a side face curtain openably and closably also at the sides C, D of the base framework. COPYRIGHT: (C)2009,JPO&INPIT
