The Effects of Proximity to Unrelated and Kin Plants on Determining [not sure that’s
necessary] Wheatgrass (Triticum aestivum) Root Growth
Ashley Huffman, Andrew Dyjak, and Karl Jackson
Department of Biological Science
Saddleback College
Mission Viejo, CA 92692
28 April 2014
Plant growth, especially root development, can be effected by the type and
proximity of plants neighboring it neighboring plants. A proposed question arose
regarding distance to kin plants and whether this would inhibit or promote root
development. It was predicted that wheatgrass plants grown near unrelated plants of the
same species would produce larger roots than those grown next to kin plants. Liquid
Sunshine wheatgrass seeds were planted into three different groups (with kin Liquid
Sunshine wheatgrass seeds, with unrelated Common wheatgrass seeds and with unrelated
Red Hard wheatgrass seeds [Are these different cultivars?]) and the roots were then
measured after twenty days. The mean length of the Liquid Sunshine wheatgrass plant
roots grown in the first tray, or kin group, was 10.83cm (N = 10). The mean length of the
Liquid Sunshine wheatgrass plant roots grown in the second tray, with the Common
wheatgrass plants, was 13.41cm (N = 10). The mean length of the Liquid Sunshine
wheatgrass plant roots grown in the third tray, with the Red Hard wheatgrass plants, was
12.79cm (N = 10). Wheatgrass plants grown within close proximity to unrelated plants of
the same species do not produce larger roots when compared to those grown next to kin
plants (p = 0.172026, one-tailed ANOVA).
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Introduction
There has been a prevalent association
between root development and plant relatedness
observed by many scientific studies, yet the extent of
this relationship and its impact on agriculture is still
highly debated. Based on the research by Biedrzycki &
Bais, [(2011) move inside comma] it was found that
plants can, in fact, recognize other plants in their
surroundings based on relatedness. Biedrzycki & Bais,
[(2010) move inside comma] noted that plant–plant
interactions have been well documented and range
from negative interactions, such as allelopathy, to
positive interactions such as the release of volatile
compounds as a warning to other plants. Fang et al.,
[(2013) move inside comma] found that belowground
tissues, such as roots, can not only detect, but also
respond to changes in their environment; exhibiting
adaptation in their morphology and physiology in
response to environmental stimuli, such as alteration in
total root length, root system volume, and root depth.
Further analysis by Milla et al., [(2009) move
inside comma] found that certain plants can identify
their kin in competitive settings through root
recognition, and can, in turn, react by decreasing their
root growth when competing with relatives. A specific
example of this was illustrated by Dudley & File
(2007) which reported that an annual plant exhibited
kin recognition, as the plant produced more roots when
grown in pots with strangers (plants of the same
species, but grown from seeds collected from different
mother plants) versus being grown with kin plants
(plants grown from seeds collected from the same
mother plant).
In another related study, Murphy & Dudley
(2009), it too produced similar results in which they
analyzed data that indicated plants exhibited both
increased competition toward stranger plants and
reduced interference (cooperation) toward kin plants.
The broader impacts of this topic have also been
investigated in the study by Milla et al., [(2009) move
inside comma] which asserted the generalization that
kin recognition may act as a widespread, major
microevolutionary mechanism in plants to reduce
competition among related plants and create
competition between unrelated plants. Our current
study addresses many of these issues and will focus
primarily on the question of whether wheatgrass plants
grown within close proximity to unrelated plants of the
same species will produce larger roots as opposed to
those grown next to kin plants.
Materials and Methods
The experiment was performed at the Biology
Greenhouse at Saddleback College in Mission Viejo,
California, <[insert comma] from 2-21 April 2014.
There were four sets of 10 Liquid Sunshine wheatgrass
plants (Triticum aestivum) used in this study (N = 10).
Prior to planting, these 40 Liquid Sunshine wheatgrass
seeds were harvested from one mature organic Liquid
Sunshine wheatgrass plant [mother plant obtained from
where?]. All of the wheatgrass seeds were planted on 2
April 2014 following the same planting procedure.
Three large plastic planting trays (20.32cm x 20.32cm)
[brand?] were used with twenty wheatgrass seeds per
tray, arranged in the following order; the first tray was
the kin group and had twenty organic Liquid Sunshine
wheatgrass seeds from the same plant, the second tray
had ten organic Liquid Sunshine wheatgrass seeds and
ten organic Common wheatgrass seeds with alternating
planting, and the third group had ten organic Liquid
Sunshine wheatgrass seeds and ten organic Hard Red
wheatgrass seeds again with alternating planting. [How
closely related are these breeds? Where are the other
seeds from?] The setup and arrangement of the
planting is shown in Figure One.
water. All trays/groups were watered three times a
week with de-ionized water and were originally planted
towards the middle of the greenhouse, but once
sprouting occurred (on day 8) were relocated to a
window location in the greenhouse. After the growth
period of twenty days passed, the roots were cut,
washed, dried, measured and then weighed and
compared to determine the outcome of the hypothesis.
On 21 April 2014, all Liquid Sunshine
wheatgrass plant roots were cut, washed using deionized water to ensure no soil remained in the roots
and then blotted dry with a paper towel. Each of the
plant’s longest roots were measured using a metric
ruler to the nearest 0.1cm and recorded into the lab
notebook. Due to the roots being extremely small, thin,
and intertwined with the other roots, it was difficult to
measure each root on the plant, so the longest root was
measured and recorded. In addition, the roots were
very small and a more precise scale was needed to
individually weigh each root. Therefore, the total
weight for the roots of all 10 plants in each group was
found to the nearest 0.01g with an analytic balance
(Scout Pro [business location?]) in a 150ml. All data
were transferred to MS Excel (Microsoft Corporation,
Redmond, Washington) where all further statistical
manipulations were performed.
Results
Tray 2
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LS x LS
LS x CW
Tray 3
LS x RHW
Figure 1. Diagram of planting arrangement. LS =
Liquid Sunshine Wheatgrass; CW = Common
Wheatgrass; RHW = Red Hard Wheatgrass (Note:
Diagram not to scale).
The planting method used was obtained from
the organic seed packets (Botanical Interests & Handy
Pantry Seed Co. [location of business?]) and all trays
were filled with Foxfarm Natural & Organic Ocean
Forest Potting Soil [location of business and perhaps
batch number?] and respectively labeled. Using the
layout seen in Figure One, all seeds were planted with
1/4 inch (0.635cm) spacing between each seed and
planted 1/8 inch (0.318cm) deep. The seeds were then
carefully covered with soil and watered with de-ionized
The mean length of the Liquid Sunshine
wheatgrass plant roots grown in the first tray, or kin
group, was 10.83cm (N = 10). The mean length of the
Liquid Sunshine wheatgrass plant roots grown in the
second tray, with the Common wheatgrass plants, was
13.41cm (N = 10). The mean length of the Liquid
Sunshine wheatgrass plant roots grown in the third
tray, with the Red Hard wheatgrass, was 12.79cm (N =
10). After 20 days of germination, it was found that
there was no statistical difference between the mean
root lengths of all three groups (p = 0.172026, onetailed ANOVA). These This data are is shown in
Figure Two.
ROOT LENGTH (CM)
Tray 1
16
14
12
10
8
6
4
2
0
1
2
3
GROUP/TRAY
Figure 2. Comparison of mean root length for Liquid
Sunshine wheatgrass plants grown next to kin plants
and next to unrelated plants of the same species (N =
10). The mean root length of wheatgrass plants grown
next to unrelated plants of the same species is not
larger than the mean root length of wheatgrass plants
grown next to kin plants (p =0.172026, single factor
ANOVA). [Specifically say which group is 1, 2, and 3]
TOTAL WEIGHT (G)
The total weight for all of the Liquid Sunshine
wheatgrass plant roots in each tray was also collected
and found to be 0.14g for tray 1, 0.27g for tray 2, and
0.32g for tray 3. Since only total weight was recorded,
statistical analysis could not be run for these data but a
graph has been included to show the weight difference
among the roots in Figure Three.
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
1
2
3
GROUP/TRAY
Figure 3. Comparison of total weight for Liquid
Sunshine wheatgrass plant roots grown next to kin
plants and next to unrelated plants of the same species
(N = 10).
Discussion
In this study, the results did not support the
proposed hypothesis. The Liquid Sunshine wheatgrass
plants grown within close proximity to unrelated plants
of the same species did not produce larger roots when
compared to Liquid Sunshine wheatgrass plants grown
next to kin plants. Although the data collected yielded
larger numbers in groups 2 and 3 for both mean root
length and overall root weight when compared to group
1, statistically this there was not a large enough
difference to show prove the hypothesis to be correct.
The overall trend of the kin group having the shortest
mean root length and lowest total root weight was
clearly evident, however, this difference in size was not
great enough to definitively conclude that proximity to
kin plants effects root size. There are several factors
that may have contributed to why these results were
obtained.
Despite efforts to ensure a consistent
environment by growing all the wheatgrass plants
specimens in the same greenhouse and placing them in
the same location within the greenhouse, certain
conditions observed contradict the belief that this
environment was uniform for all trays. For example,
although all of the groups were watered the same
amount and at the same times, the consistency of how
‘wet’ the soil was would fluctuate. The air circulation
within the greenhouse may have caused the soil in
certain trays to become dryer and inhibited root
growth. In addition, the trays seems seemed to be
growing at different rates, with tray 2 seeming to grow
the slowest. An uneven distribution of direct sunlight,
as well as proximity to air ventilation, may have
contributed to why tray 2 seemed to be growing at a
slower rate than the other trays.
Although we can conclude that the
environmental conditions within the greenhouse may
not have been optimal for ideal plant growth, there are
other factors which may have effected affected the
results as well. Despite the pH of the soil not having
been measured, it could have been a variable which
affected the outcome of this study. More significantly,
however, the type of plant used in this experiment is
not one that any of the previous research has been
based upon. In addition, the research gathered for this
study used different methods of growing and
measuring the plants and their roots. As in Dudley &
File (2007) which reported that an annual plant
exhibited kin recognition, as the plant produced more
roots when grown in pots with strangers versus being
grown with kin plants. The use of large plastic trays
instead of individual pots, as well as the need for a
different species of plant, could have negatively
impacted the wheatgrass plant’s root growth. This is
especially true when taking into account how
intertwined and thin the roots of the wheatgrass plants
were and furthermore supports the necessity of a
different species of plant, perhaps an annual or bean
plant, whose roots are much more defined. [You’re
right, the species itself was probably to blame; grasses
are adapted to growing in close proximity to
conspecifics, it’s doubtful that they’d display
aggression toward one another.]
Further studies are needed to distinctly define
the effects of proximity to unrelated and kin plants on
determining root growth. Suggestions for such future
endeavors include using different plants to study whose
roots are much more well-defined in addition to using
different methods of evaluating them, such as
measuring distance of roots from other plants and/or
individually weighing and measuring each root. The
findings produced from these future experiments could
yield results that would impact agricultural practices
currently in place in order to accommodate the need for
plants in geographical areas that will not outcompete
each other for nutrients. [Are there any particular
species or scenarios you’d recommend?]
Literature Cited
Biedrzycki, ML, and Bais, HP. 2011. Kin Recognition:
Another Biological Function for Root Secretion.
Landes Bioscience Plant Signaling & Behavior vol
5(4): p 401–402.
Biedrzycki ML, and Bais HP. 2010. Kin Recognition in
Plants: a Mysterious Behaviour Unsolved. Journal of
Experimental Botany vol 61: p 4123–4128.
Dudley, SA, and File, AL. 2007. Kin Recognition in an
Annual Plant. Biology Letters vol 3: p 435-438.
Fang, S, Clark, RT, Zheng, Y, Iyer-Pascuzzi, AS,
Weitz, JS, Kochian, LV, Edelsbrunner, H, Liao, H, and
Benfey, PN. 2013. Genotypic Recognition and Spatial
Responses by Rice Roots. Proceedings of the National
Academy of Sciences of the United States of America
vol 110: p 2670–2675.
Milla, R, Forero, DM, Escudero, A, and Iriondo, JM.
2009. Growing with Siblings: a Common Ground for
Cooperation or for Fiercer Competition Among Plants?
Proceedings of the Royal Society Lond B Biological
Sciences vol 276(1667): p 2531-2540.
Murphy GP, and Dudley SA. 2009. Kin Recognition:
Competition
and
Cooperation
in
Impatiens
(Balsaminaceae). American Journal of Botany vol 96:
p 1990–1996.
Review Form
Department of Biological Sciences
Saddleback College, Mission Viejo, CA 92692
Author (s):__Ashley Huffman, Andrew Dyjak, Karl Jackson___________
Title:_The Effects of Proximity to Unrelated and Kin Plants on Determining Wheatgrass
(Triticum aestivum) Root Growth__________________________
Summary
Summarize the paper succinctly and dispassionately. Do not criticize here, just show that you understood the paper.
The authors attempted to determine whether wheatgrass responds to the presence of unrelated
conspecifics by altering its roots’ growth patterns. It was hypothesized that, when in the
presence of non-kin plants, root size would increase in order to outcompete its neighboring
conspecifics. Plants were grown over the course of 19 days in three groups, one consisting
entirely of kin plants, and the other two consisting of a mix of the target cultivar and another
variant of the species. While the mean root size and mass was higher in the non-kin groups,
there was still no statistical difference between these and the control of all kin plants.
General Comments
Generally explain the paper’s strengths and weaknesses and whether they are serious, or important to our current
state of knowledge.
Overall, the paper is strong and well written. The authors could expand upon the reasoning
behind their hypothesis further (why, specifically, would a plant grow larger roots when it is near
a competitor?) and they could also explain the different breeds of wheatgrass (what are the
differences? Are they natural or artificially bred?). Otherwise, the data is well presented and all
sections are strong
Technical Criticism
Review technical issues, organization and clarity. Provide a table of typographical errors, grammatical errors, and
minor textual problems. It's not the reviewer's job to copy Edit the paper, mark the manuscript.
Publishing dates need to be moved within commas, more info on supply companies is needed,
some minor grammar errors, eliminate column format.
This paper was a final version
This paper was a rough draft
Recommendation
 This paper should be published as is
 This paper should be published with revision
 This paper should not be published