Abstract
Plants perceive the shade stimulus to escape from it. This response, known as the shade avoidance response, is triggered by reduction in the level of Pfr phytochrome. We aim to understand spatio-temporal network governing the shade avoidance response. In this direction, we have shown; 1) the light signal is perceived by cotyledons at early night, 2) the signal is completely transferred from cotyledons to the other parts within 4 to 6 hrs, and 3) the actual elongation takes place towards the morning (Kobayashi et al., JSPS Annual Meeting, 2010). In the present study, we investigated the involvement of auxin in the above process. Assuming that auxin was provided to the hypocotyl from the shoot apex, we disconnected the apex from the other parts by laser ablation. Consequently, we found that this connection was required for the promotion of elongation by FR. More importantly, exogenous auxin promoted the elongation in the laser-ablated seedlings only when the seedlings were treated with FR in advance. Hence, FR apparently affected the sensitivity of the elongation zone to exogenous auxin. The gene expression analysis is now in progress to further characterize this phenomenon.
