A novel phototropic response to supplementary ultraviolet (UV-B and UV-A) radiation in the siliquas of oilseed rape (Brassica napus L.) grown under natural conditions

An outdoor polychromatic response spectrum for the phototropic curvature of the seed pods (siliquas) of oilseed rape (Brassica napus L. cv. Rebel) has been measured. The plants were sown and grown at a location of 52° 12 N and 0° 07 E under natural daylight and ambient environmental conditions with supplementary ultraviolet (UV-B and UV-A) radiation. This radiation had central wavelengths of 313, 319, 324, 339, 348, 356 or 377 nm and was supplied daily for 10 hours at an irradiance of 0.13 W m–2. An action maximum for phototropic curvature of the siliquas was observed at 319 and 324 nm.