Presence of Tyloses at the Blade/Sheath Junction in Senescing Leaves of Lolium temulentum L.

Aspects of age-related changes occurring in the blade/sheathjunction of leaves ofLolium temulentum L. were studied usingautoradiography, light and transmission electron microscopy.With increasing leafage the apical transport of sheath-appliedradioactive amino acids was retarded at the sheath side of theblade/sheath junction. An anatomical study revealed the presenceof tyloses in the protoxylcm lacunae of vascular bundles atthis region in senescing leaves. The possible involvement oftyloses in grass leaf senescence is discussed.