48 PNL Volume 15 1983
Nozzolillo, C., S. Moy, and L. Boylen
Department of Biology
University of Ottawa, Canada
Plants grown from seeds of line WT 10 26 3 kindly provided by
W. K. Swiecicki (1) were observed throughout development under a 14-hr
day at 15C in a Conviron growth cabinet. The plants, dwarf with short
internodes, had stems of a normal green color in the upper internodes,
but, by the time the eighth node (sixth true leaf) had appeared, an
orangey cast was visible in the older internodes and in the petioles of
the leaves. The orange color was associated with vascular tissue as
could be seen in hand-cut cross sections, the color first appearing in
the walls of the phloem sclerenchyma bundle caps. In the oldest inter-
nodes, the color was also evident to some extent in xylem cell walls and
more prominently in the walls of the pith cells lying between the vas-
cular bundles. As the plants flowered and began to bear fruit, normal
green pods at first appeared, then the orange cast resulting from a
colored inner sclerenchyma tissue became evident. The peduncle of the
fruit also was an orangey color with the color especially prominent in
vascular sclerenchyma tissues, i.e. the orange color is associated with
Green stems from plants of WL 1754 and orange stems of WT 10 263
plants were extracted with acetone, and the extracts were partitioned
into lipid soluble chloroplast pigments and water soluble flavonoids.
Both fractions were subjected to thin layer chromatography on silica gel
with the solvent systems hexane: diethy1 ether: acetone, 6 0:30:20, for
chloroplast pigments, and ethyl acetate-methanol :water, 100:17.5:16.5,
for flavonoids. Chloroplast pigments were identical in both types of
extract, demonstrating that the orangey color is not a carotenoid.
Flavonol pigments were also similar in a one-dimenaional run, except for
the presence of a large blue fluorescing band in extracts of WT 10 263.
A similar observation was made when extracts from the green upper inter-
nodes were compared with extracts from the orange older Internodes of
the same WT 10 263 plant. The extracted residues of the orange tissues
retained a yellow color which could be dissolved only with a 10% solu-
tion of K0H. Neutralization of the bright yellow alkaline solution with
HC1 resulted in a fading of the color and the precipitation of an in-
soluble yellow substance. Attempts to identify the blue-fluorescing
compound and the insoluble yellow substance are in progress.
1. Swiecicki, W. K. 1982. PNL 14:65.