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Fig. 1. gram mutations affect leaf growth and adabaxial asymmetry. (A)
Comparisons of the length and width of fully expanded leaves of wild-type
(filled bars) and gram-1 (open bars) at nodes 1 to 6. Values
represent means of eight replicates and error bars, one standard deviation.
(B) The adaxial wild-type leaf (top left) appears darker than the abaxial (top
right). In gram mutant leaves, strips of darker tissue extend
abaxially (arrowheads). (C) The wild-type adaxial leaf surface (left) consists
of large, irregular pavement cells and rectangular cells towards the leaf edge
(left in this image). Abaxial pavement cells (centre) are smaller and
interspersed with frequent stomata (s). The edge of the leaf (right) consists
of elongated edge cells (e). (D) In gram mutants, adaxial pavement
cells are unaltered whereas cells at the margins are more irregular (left),
edge cells are found abaxially (centre) and larger abaxial cells are seen, and
stomata and hairs (h) are found at the leaf edge. (E) A transverse section of
a wild-type leaf shows that, the junction between adaxial palisade mesophyll
(pm) and abaxial spongy mesophyll (sm) cells runs to the edge of the leaf
(arrowhead). In the gram mutant leaf (F), palisade mesophyll cells
(pm) are found abaxially at the margins and adaxial cells away from the margin
resemble spongy mesophyll. (G,H) gram mutants occasionally produce
needle-like leaves (arrowhead in G), that appear radial in transverse section
(H). (I) The arrangement of xylem elements internal to phloem in central
vascular bundles of these leaves suggests a loss of adaxial leaf identity.
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