My Account: Log In | Join | Renew
Search
Author
Title
Vol.
Issue
Year
1st Page

Abstract

 

This article in CS

  1. Vol. 24 No. 3, p. 593-597
     
    Received: Oct 1, 1983
    Published: May, 1984


 View
 Download
 Alerts
 Permissions
 Share

doi:10.2135/cropsci1984.0011183X002400030038x

Phototropic Leaflet Reorientation in Alfalfa in Response to Vectorial Light1

  1. R. Reed and
  2. R. L. Travis2

Abstract

Abstract

The phototropic reorientation of alfalfa (Medicago sativa L.) leaflets in response to vectorial light involves a complex series of movements in which the elevational angle of the leaflets either increases or decreases, the compass direction of the leaflet midrib changes and the leaflet rotates about its midrib axis. The exact combination of movements depends upon the leaflet position on the plant and the azimuth and elevational angle of the vectorial light source. The photoreceptor for leaflet reorientation is sensitive to blue light, insensitive to red and far red light and is located in the pulvinule. The time required for leaflet reorientation was dependent upon the vectorial photosynthetic photon flux density (PPFD). At high PPFD (850 to 1600 μmol m-2 s-1) reorientation proceeded rapidly with the full response requiring 45 to 60 min. As the PPFD was decreased the rate of reorientation also decreased. At the lowest PPFD tested (100 μmol m-2 s-I) the response only occurred after a 2 h lag period but then proceeded at a rapid rate with the leaflet attaining its final position in 30 rain. Upon completion of the reorientation response the adaxial surface of the leaflet was nearly perpendicular to the light source. The final position was independent of PPFD.

  Please view the pdf by using the Full Text (PDF) link under 'View' to the left.

Copyright © .