Fig. 1.

Roots of 9-month-old hydroponically grown Hakea actites initially cultivated without N and then grown for 26 weeks with different N forms. No-nitrogen (A) and a low N concentration (15 μM N) of NH₄NO₃, glycine, or BSA (B, C, D). Plants grown with a higher N concentration (150 μM N) did not produce cluster roots. Cluster roots are highlighted by white circles. Scale bar = 20 mm. (This figure is available in colour at JXB online.)