Plant growth lighting fixture

A plant growth lighting fixture comprising,

• a lighting fixture main body having a light exit surface;
• a light source held on the lighting fixture main body;
• and
• a reflective-type circularly polarizing plate that selectively reflects circularly polarized light having a particular rotational direction in a particular wavelength range,
• wherein the reflective-type circularly polarizing plate has a support and a circularly polarized light reflecting layer held on the support,
• the lighting fixture main body has a holding mechanism for detachably mounting the reflective-type circularly polarizing plate with a main surface of the reflective-type circularly polarizing plate facing the light exit surface, and
• the holding mechanism has grooves that accommodate two opposite end portions of the reflective-type circularly polarizing plate, and the reflective-type circularly polarizing plate is detachably mounted by inserting the two opposite end portions of the reflective-type circularly polarizing plate into the grooves.