Symposium Poster Final
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Anthocyanins are red and purple pigments whose function in leaves is poorly understood. These
pigments often accumulate in stressed, juvenile, or senescent (e.g. autumn) leaves. One
hypothetical role is photoprotection, or blocking excess light from damaging leaves. This
damage can lead to reduced photosynthesis, a phenomenon called photoinhibition. Other
hypotheses include protection from insect herbivores and disease. However, anthocyanins are
metabolically costly to produce, and they may block some usable light. Blocking of light could
lead to comparatively lower photosynthesis in low light conditions.
Research ObjectiveExamine the effects of anthocyanin accumulation on photosynthesis, photoinhibition, and leaf herbivory and disease using three crop species.
I thank Mary Canady and Jeremy Tardiff for use of a plot at the Bowdoin Organic Garden. I also thank Mike and Lucretia Woodruff for loaning a plot on their farm. Thank you to Jack
OBrien for advice on organizing data, and to Fedco Seeds for donating seed. This project was funded by the Bowdoin Life Sciences Fellowship.
Herbivory and Disease
I collected data weekly for plants at two sites over the course of several weeks. Damage
from disease/class of herbivores was recorded as the proportion of leaves affected by a
certain type of damage.
Two plots were established to diversify the herbivore and disease pressures plants
o Bowdoin Organic Garden: In a suburban environment. Herbivores associated with lawns,
such as leafhoppers and oriental beetles, were predicted to be more common.
o Milkweed Farm: In an agricultural setting surrounded by woodland. Herbivores that
commonly attack crop plants, such as flea beetles and cabbage white caterpillars, were
predicted to be more common.
Data is shown for fully expanded leaves at the Bowdoin Organic Garden on July 24, 2015
Green lettuce shows higher disease damage than red lettuce (Fig 1, Sidaks post hoc, t(53) =
2.25, p < 0.0001); other species have low levels of disease. May be evidence for protection
Flea beetle damage was significantly higher in green variety of kale (Fig 1, Sidaks post hoc,
t(53) = 2.25, p = 0.005). This is possible evidence for anthocyanins repelling flea beetles.
(Note: Flea beetle damage was much more common at Milkweed Farm, and preliminary data
analysis suggests green lettuce was more affected than red lettuce.)
There were no consistent trends for damage from leafhoppers and other herbivores.
On-going data analysis will take into account temporal and site differences.
Examining Functional Roles for Anthocyanins in Plant Leaves
Benjamin M. West; Advisors: Barry Logan and Jaret Reblin
Red Kale Green Kale Red Lettuce Green Lettuce Red Shiso Green Shiso Bicolored* Shiso*green upper side of leaf, red underside
Photosynthesis and Photoprotection
Photosynthesis was measured as CO2 uptake at various light intensities.
Degree of photoinhibition was quantified using a chlorophyll-fluorescence
based measurement of photosystem II (PSII) efficiency.
There was no significant differences between varieties regarding the light
intensity at which net photosynthesis equals zero (Figs 2A-C, two-way ANOVA,
F(1, 24) = 0.004, p > 0.9). This does not support hypothesis of detrimental
light blocking by anthocyanins.
There was a higher maximum photosynthetic rate in green lettuce than red
lettuce (Sidaks post-hoc, t(24) = 3.43, p = 0.007) . This would not be due to
anthocyanins blocking light.
There were no signs of photoinhibition in any variety (Fig 2D, Fv/Fm > 0.8)
and no differences in maximum PSII efficiency between red and green
varieties (Fig 2D, two-way ANOVA, F(1, 78) = 0.77, p = 0.4). Anthocyanin
accumulation appeared to confer no additional photoprotection in these crop
species under sunny field conditions.
Bicolored shiso had lower max PSII efficiency than red shiso (Fig 2D, Tukeys
post-hoc after a one-way ANOVA, p = 0.004). This does not seem to be an
Figure 2. Plots of photosynthetic rates at varying light intensities for red- and
green-leafed crop plants (A C) and maximum photosystem II efficiency for the
same plants measured after a sunny day. n.s. = not significantly different; values
with different letters above them are significantly different.
= green, = red, = bicolor
Anthocyanins may play a role in repelling flea beetles and decreasing disease
susceptibility. Trends regarding damage from other herbivores are currently unclear
but may become apparent as more data is analyzed.
Anthocyanin accumulation does not appear detrimental to photosynthesis at low
Neither red nor green crop plants become photoinhibited under sunny summer
conditions. If anthocyanins are providing a photoprotective role in red plants, other
photoprotective mechanisms must be equally active in the green plants.
Figure 1. Average proportions of fully expanded leaves of crop plants affected by various types of
damage. Statistical differences within plant species shown. n.s. = not significantly different; values
with different letters above them are significantly different at a value of p 0.05, and pairs of bars
with a star over them are significantly different from each other at a value of p 0.05.
= green, = red, = bicolor