Roots ofNicotiana sylvestrisLack Phototropism

• Published in: International journal of plant sciences 2004-07, Vol.165 (4), p.565-570
• Main Authors: Lucas, Sasha Y., Kiss, John Z.
• Format: Article
• Language: English
• Subjects: Curvature; Fluence; Hypocotyls; Lighting; Phototropism; Plant roots; Plants; Root tips; Seedlings; Soil quality
• ISSN: 1058-5893; 1537-5315
• DOI: 10.1086/383333

The interaction between phototropism and gravitropism is important in early plant development, and these two tropisms are important for the continued survival of the plant. Of these tropisms, root phototropism has been largely unstudied for decades but has received increased attention with the availability of molecular tools associated with usingArabidopsis thalianaas a model plant. Roots ofA. thalianaseedlings, while exhibiting a strong positive gravitropism, also have a negative phototropism induced by blue light and mediated by the phototropin family of photoreceptors. In addition,A. thalianaroots exhibit a positive phototropism mediated by phytochromes A and B. The major focus of our research was to examine root phototropism inNicotiana sylvestris, which also has been a model system in studies of physiology and development. Results with orientation and time course experiments with unilateral illumination demonstrate that roots ofN. sylvestrisseedlings are not phototropic in the presence of white or blue light. While orientation experiments initially indicated a possible red light–induced phototropic curvature in roots, time course studies and experiments with a high‐resolution computer‐based feedback system confirmed thatN. sylvestrisroots were phototropically insensitive to red light as well. The reasons for the apparent lack of root phototropism inN. sylvestrismay be related to recently reported differences in cytoplasmic regulation of phytochrome compared toA. thalianaand also to the spectral qualities of the soil in whichN. sylvestrisnaturally occurs.