William White
Lab 1
Introduction and Lab Questions
Anthocyanin is a purple pigment made in various plant species. Experiments by
Mancinelli and Rabino (1975) showed that anthocyanin formation can be incited by
various qualities far red light exposed to cabbage. To expand upon their experiment,
light-dependant anthocyanin formation was studied in Dahlias. The purpose of this lab
was to determine in an all-or-nothing manner how anthocyanin is dependant upon light
exposure for Dahlias (genus - Dahlia). Preliminary field observation data was gathered
to determine which strains formed anthocyanin with light dependant pathways. By
finding out which varieties are light dependant further studies on color exposure and light
quality can be pursued.
Results
Experimental setup
Hypothetically, if anthocyanin formation is light dependant then blocking light exposure
to unpigmented areas should prevent formation of anthocyanin pigments.
To test light dependence, light exposure was blocked on plant internodes by wrapping
3cm wide aluminum foil strips around the plants for one week. For each plant 2
internodes were covered with an uncovered internode between each (See figures 1 and 2).
Experiments can be split into three groups: 1) Control plants to show aluminum foil
neither causes nor bleaches anthocyanin formation, 2) plants where both covered
internodes were green [Figure 1], and 3) plants where one internode had anthocyanin
pigmentation and the second internode was green (Figure 2 – note pigmentation
difference between top and bottom foil areas).
Fig 1
Figure 1 shows CG Elegance just
after foil treatment. Note that
both covered internodes are green
Fig 2
Figure 2 shows Pooh immediately
after foil was added. Note the
green upper node and brown
lower node
The table below shows the varieties treated and internode colors before and after foil
treatment
Variety
Internode colors before
Internode colors after
Notes
Smooth Operator
Both fully purple
Entire plant remained
purple
Blackberry
Ripple
Both internodes green
Entire plant remained
green
CG Elegance
Both internodes green
Pooh
Upper internode –
green
Lower internode –
brown (pigmented)
Nodes remained
green while flanking
internode turned
purple, sharp
boundary
Upper internode
remained green with
purple flanking
reigion
Lower indernode had
no noticeable changes
Smooth operator
acts as a control to
show the foil does
not bleach existing
pigment (Figure 3)
Blackberry Ripple
does not form
anthocyanin with
or without light,
negative control
for light treatment
Light dependant
(Figure 4)
Alpen Diamond
Both internodes were
green
Upper internode
remained green while
internode flanking
region became purple
Lower internode
remained green and
some pigment
appeared in flanking
region
Figure 2 and 5 –
Showed light
dependence as a
function of age
(older internodes
did not have
extensive change)
Figure 6 (upper)
and 7 (lower) –
shows light
dependence, but
older internode did
not show as sharp
contrast as upper
internode.
Figure 3 – Smooth Operator
Figure 3 shows the Smooth Operator control. Foil was left on for picture to show treated
nodes. No color was removed from the purple stems.
Figure 4 – CG Elegance after
Figure 4 shows CG Elegance after foil blocking for one week. CG Elegance shows the
sharpest contrast between the covered (green) and uncovered (pigmented) areas.
Figure 5 – Pooh After
Figure 5 shows Pooh after light blocking treatment. The covered internodes are at the top
and bottom of the photo (top has green band). Pooh showed a dramatic difference
between the two nodes.
Figure 6
A
B
Figure 6 shows the two Alpen Diamond covered internodes. The top node (a) shows a
clear green strip flanked by purple pigmentation with the lower node (b) shows a more
subtle difference in color between the two internodes.
Conclusions
The results of the experiments showed that some varieties are light sensitive. Blackberry
ripple was shown not to form anthocyanin regardless of light exposure. No conclusions
about Smooth Operator’s light dependence can be drawn, but other groups showed
Smooth Operator pigmentation does exhibit light dependence. Alpen Diamond, CG
Elegance, and Pooh all showed light-dependant anthocyanin formation.
Results from Pooh indicate that the time period of light exposure signaling anthocyanin
formation is independent for each internode, so older internodes (lower on the plant) may
stop forming pigment while younger internodes are still sensing light and forming
anthocyanins.
A logical extension of this experiment would be to look for color/wavelength dependence
on anthocyanin formation by covering the plants with various color filters. Based on
Mancinelli and Rabino (1975) far red/red light caused anthocyanin pigmentation in
cabbage, but dahlia anthocyanin pigmentation could depend on blue light or even
ultraviolet light exposure.
References
Mancinelli, Alberto L. and Isaac Rabino. Photocontrol of Anthocyanin Synthesis: IV.
Dose Dependence and Reciprocity Relationships in Anthocyanin Synthesis. Plant
Physiol. 1975 Sep;56(3):351-355.