Phytochrome-regulated organogenesis in lettuce tissue culture

Abstract

LIGHT intensity and daily photoperiod are known to affect organ development in tissue culture¹, but little information is available on the spectral region influencing organogenesis. Studies with tobacco callus have shown that shoot initiation is enhanced by blue light^2,3 and that red light has no influence. Red light, on the other hand, promotes callus growth and adventitious bud formation in some species^4,5 and induces the elongation of endogenous buds in cultured root segments of Convolvulus arvensis L.⁶. The latter phenomenon is regulated by phytochrome⁶. In the culture conditions described here, lettuce cotyledon cultures develop well-formed shoots under daily (16-h photoperiod) irradiation from broad-band emitting fluorescent lamps. Dark-grown control cultures, on the other hand, form significantly fewer shoots. We describe here the enhancement of shoot formation in lettuce cotyledon cultures by red light and demonstrate that organogenesis is under phytochrome control⁷.