Original Articles


, Volume 214, Issue 1, pp 65-72

First online:

Phloem loading in the sucrose-export-defective (SXD-1) mutant maize is limited by callose deposition at plasmodesmata in bundle sheath—vascular parenchyma interface

  • C. E. J. BothaAffiliated withBotany Department, Rhodes University Email author 
  • , R. H. M. CrossAffiliated withElectron Microscopy Unit, Rhodes University
  • , A. J. E. van BelAffiliated withInstitut für Allgemeine Botanik und Pflanzenphysiologie, Justus-Liebig Universität Giessen
  • , C. I. PeterAffiliated withBotany Department, Rhodes University

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access


Using Lucifer Yellow we have demonstrated that the phloem-loading pathway from the mesophyll to the bundle sheath—vascular parenchyma interface inZea mays source leaves follows a symplasmic route in small and intermediate vascular bundles in control as well as in the green sections of mutant sucrose-export-defective (SXD-1) plants. In the anthocyanin-rich mutant leaf sections, Lucifer Yellow transport was prohibited along the same path, at the bundle sheath—vascular parenchyma interface in particular. Plasmodesmata at the latter interface in SXD-1 anthocyanin-rich leaf sections appear to be structurally altered through callose deposition at the plasmodesmal orifices. We suggest that a transport bottleneck at the bundle sheath—vascular parenchyma interface is thus orchestrated and regulated through callose formation, preventing symplasmic transport across this important loading interface.


Callose Lucifer yellow Plasmodesma Phloem loading Sucrose-export-defective mutant Zea mays