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ABSTRACT
As the world’s population grows, sustainable food production and consumption
has emerged as a complex biological problem. Managing this problem will
require informed action by all citizens, which necessitates heightened
comprehension of complicated quantitative datasets from multiple sources of
information. This makes it imperative that undergraduates develop quantitative
skills and information literacy in the context of biology. This laboratory module
provides a framework for conducting discovery experiments that examine the
resource demand (i.e., water use) of cultivation methods (compost-based,
hydroponic) and their impact on the nutritional value of microgreens. Students
use experimental and published data to compare the nutritional value and
resource demands of microgreens to that of vegetables produced on industrial
farms. Quantitative analyses culminate in critical thinking and discussion
through which students come to a consensus on the potential of microgreens to
be a sustainably produced crop that serves human nutritional needs.
Key Words: biological literacy; microgreens; discovery research; quantitative
analysis; information literacy; sustainability.
Introduction
As the world’s population grows at unprece-
dented rates with the concurrent demand on
natural resources, humankind is faced with
the need to develop ways to live more sus-
tainably on Earth. Living sustainably requires
balancing concerns for human well-being
with those for protecting the ecosystems on
which life depends (Walker & Salt, 2006).
Finding this balance necessitates understand-
ing the many, and usually interdisciplinary,
facets of any given problem, and how they
are interrelated (UNESCO, 2003). These interrelationships are increas-
ingly encoded in large and complicated quantitative datasets in multi-
ple sources of information (Schultheis & Kjelvik, 2015). This makes
information literacy vital to the future success of society; the need
for undergraduates to develop quantitative skills to analyze this infor-
mation and draw conclusions from it is especially dire, as many have
left high school with inadequate quantitative skills (Massey, 1989;
Foreman & Steen, 1999; U.S. Department of Education, 1996;
AAAS, 2011). As a result, it is imperative that undergraduates have
the opportunity to develop quantitative skills and information liter-
acy, especially in the context of real-world biological problems that
they will face in the future irrespective of their declared majors and
professional goals.
One example of a real-world problem is the emerging planetary
food crisis. The earth’s population is expected to reach nine billion
by the year 2050, and to accommodate the nutritional needs of this
population, agricultural yields will need to increase by 70–100 percent
(AAM, 2012). Simply upscaling current industrial agricultural opera-
tions is not a viable solution because it would increase the already
unsustainable demand on water as well as resources to manufacture
fertilizers (Metson et al., 2013; Kim & Lauder, 2013). These issues, and
others with industrial agriculture, have some wondering if distributed
agriculture, in which people take responsibility for
growing some of their own food, might more effi-
ciently redistribute and/or reduce the demand on
resources. For instance, fossil fuel use would be
reduced as people buy less industrially farmed pro-
duce that is transported long distances from rural
to urban areas (Evans et al., 2012). Distributed agri-
culture may increase the accessibility to more nutri-
tious and safer foods, as produce from industrial
farms can lose substantial nutritional value during
transport (Rickman et al., 2007) and is at risk for
microbial contamination as it is handled during proc-
essing (e.g., Opara, 2003).
One crop that may make distributed agricul-
ture feasible, even for urban dwellers and inexperienced gardeners,
is microgreens. However, few scientific studies have evaluated the
potential of microgreens to be a sustainably produced crop that
Living sustainably
requires balancing
concerns for human
well-being with those
for protecting the
ecosystems on which
life depends.
The American Biology Teacher, Vol. 79, No 5, pages. 375–386, ISSN 0002-7685, electronic ISSN 1938-4211. ©2017 National Association of Biology Teachers. All rights
reserved. Please direct all requests for permission to photocopy or reproduce article content through the University of California Press’s Reprints and Permissions web page,
www.ucpress.edu/journals.php?p=reprints. DOI: https://doi.org/10.1525/abt.2017.79.5.375.
THE AMERICAN BIOLOGY TEACHER MICROGREEN FARMING & NUTRITION
375
INQUIRY &
INVESTIGATION
Microgreen Farming and Nutrition:
A Discovery-Based Laboratory
Module to Cultivate Biological
and Information Literacy in
Undergraduates
•CAROLYN F. WEBER
serves human nutritional needs. Such evaluations can be conducted
via the experiments and quantitative analyses in the laboratory
module described below (Figure 1). These experiments engage
undergraduates in discovery research, which has been correlated
with increased student motivation and learning gains (NRC,
2003; Weaver et al., 2008; AAAS, 2011), while integrating quanti-
tative analyses and biological and information literacy into intro-
ductory biology courses (Table 1). This integration is consistent
with recommendations from the American Association for the
Advancement of Science (AAAS, 2011) for revising undergraduate
biology education and works toward achieving the Information Lit-
eracy Competency Standards for Higher Education outlined by the
Association of College and Research Libraries (ACRL, 2000).
Why Study Microgreens?
Microgreens are edible seedlings that are usually harvested 7–14 days
after germination when they have two fully developed cotyledon leaves
(Xiao et al., 2012). A wide variety of herbs (e.g., basil, cilantro), vegeta-
bles (e.g., radish, broccoli, mesclun), and even flowers (e.g., sunflowers)
are grown as microgreens. Microgreens are generally more flavorful,
some of them quite spicy, than their mature counterparts, and have
grown in popularity among culinary artists for adding texture and flavor
accents to salads, sandwiches, and other dishes (Treadwell et al., 2010;
Wallin, 2013). The increasing culinary demand as well as the ease with
which microgreens can be grown, even by inexperienced gardeners in
urban settings, has piqued interest in growing and eating them.
Figure 1. This diagram highlights how discovery experiments on microgreen growing methods and nutrition can create a
platform for teaching biological, quantitative, and information literacy, culminating in a real-world critical thinking exercise.
Photograph taken by Jason T. Werth.
THE AMERICAN BIOLOGY TEACHER VOLUME. 79, NO. 5, MAY 2017
376
Interest in microgreens has also been generated by popular web-
sites (e.g., Warner, 2012) touting the findings of Xiao et al. (2012),
which indicate that microgreens may have 4 to 40 times the amount
of some nutrients and vitamins as the vegetables a mature plant would
produce. However, Xiao et al. (2012) note that the nutritional aspects
they measured varied widely among microgreen types, providing fod-
der for future study. Furthermore, the methods used to grow micro-
greens are diverse and could significantly affect their nutritional
value, but have not been extensively investigated in this context.
Additionally, a systematic comparison of the environmental impacts
(i.e., water use, nutrient demand) of microgreen cultivation methods has
not been conducted and should be considered alongside their impacts
on nutritional value when deciding how to grow microgreens. Many
growers use soil-based methods, but some use hydroponic methods to
avoid contamination of microgreens by soil microbes that can accelerate
spoilage or cause illness (Xiao et al., 2014). Hydroponic methods
involve growing microgreens on fiber mats moistened with fertilizer,
which exerts strong control over growth rate and nutritional value.
Growers using soil-based methods routinely report that soil is a big
expense as “new”soil is put into each tray of microgreens they grow,
and that washing the harvest to reduce soil microbial contamination
can be time-consuming and costly. However, it is not clear if switching
to hydroponic methods represents a solution, as one would need to
repeatedly purchase and discard hydroponic mats as well as use fertilizer.
Module Objectives and Rationale
This laboratory module outlines a discovery research project (Figure 1)
that was designed for a semester-long (15-week) Biology II Laboratory
course for undergraduates (Idaho State University (ISU), Pocatello) that
meets formally twice per week (3 hours total) and requires students to
do some work outside of class (see Table 2). In this course, groups of
3–5 students perform discovery research projects under the direction
of a mentor; these projects are the sole focus in lab and are not com-
pleted alongside traditional Biology II Laboratory activities/exercises.
There were three specific learning objectives for this module:
1. Use writing assignments based on videos and primary liter-
ature (Table 3) to grow student biological literacy (Table 1)
and awareness of the following: (a) the impacts of industrial
Table 1. Core Concepts for Biological Literacy (AAAS, 2011) and Information Literacy Competency
Standards for Higher Education (ACRL, 2009), indicating which ones are emphasized by the laboratory
module described in this article.
Five Core Concepts for Biological Literacy (AAAS, 2011) Core Concepts
emphasizedConcept Description
Evolution The diversity of life evolved over time by processes of
mutation, selection, and genetic change.
Structure & Function Basic units of structure define the function of all living things. X
Information Flow, Exchange, &
Storage
The growth and behavior of organisms are activated through
the expression of genetic information in context.
Pathways & Transformations of
Energy & Matter
Biological systems grow and change by processes based
upon chemical transformation pathways and are governed
by the laws of thermodynamics.
X
Systems Living systems are interconnected and interacting. X
Information Literacy Competency Standards for Higher Education (ACRL, 2009)
Standards addressed
Standard Description
1 The information-literate student determines the nature and
extent of the information needed. X
2 The information-literate student accesses needed information
effectively and efficiently. X
3 The information-literate student evaluates information and its
sources critically and incorporates selected information into
his or her knowledge base and value system.
X
4 The information-literate student, individually or as a member
of a group, uses information effectively to accomplish a
specific purpose.
X
5 The information-literate student understands many of the
economic, legal, and social issues surrounding the use of
information, and accesses and uses information ethically and
legally.
THE AMERICAN BIOLOGY TEACHER MICROGREEN FARMING & NUTRITION
377
agriculture on the environment, (b) the food crisis that is
emerging alongside unprecedented human population growth
rates, and (c) the relevance of biology to everyday life and its
connections to other disciplines (e.g., economics, sociology,
politics).
2. Engage students in analyzing quantitative experimental data
to: (a) demonstrate the importance of soil quality and agricul-
tural methods on the nutritional value of food, (b) compare
the nutritional value of microgreens to that of vegetables,
and (c) empower them to think critically about the potential
for microgreens to be sustainably produced and to serve
human nutritional needs.
3. Assist students in developing information literacy with an
emphasis on standards outlined by the ACRL (Table 1).
Objective 1 seeks to immerse students in the interdisciplinary nature
of biology. This module’s activities emphasize Core Concepts of Bio-
logical Literacy (Table 1) and use the emerging food crisis to link
them to diverse disciplines (i.e., economics, politics, sociology) that
become relevant as communities work toward sustainable food pro-
duction and consumption. Additionally, this module forces students
Table 2. Weekly schedule of module activities for a 15-week semester, and desired student outcomes.
Students met formally for class twice per week (3 hours total). *Activities requiring work beyond formally
scheduled class times. Writing assignments are detailed in Table 3.
Week Module Activities Desired Student Outcomes
1
•Class discussions: Introduction to microgreens and the food crisis
•Writing assignment 1*
•Increased awareness of environmental
impacts of industrial agriculture, food
crisis, and the interdisciplinary nature
of biology.
2
•Class discussions: Cultivation methods used in industrial and distributed
agriculture. Pros and cons of cultivation methods with respect to
environmental health.
3
•Class discussions: Nutritional value of plants & its relationship to soil
quality. Macro and micronutrients in human nutrition.
4
•Design & set-up of trial experiment
•Writing assignment 2*
•Gain experience in utilizing the
scientific method and iteration (using
preliminary data to refine
experimental design).
•Practice of and use of basic laboratory
skills to generate quantitative data.
5
•Harvest trial experiment
•Hands-on orientation to protocols for extracting protein, enumerating
microbes on plant surfaces, analyzing nutrient content of plant material
6
•Finalize experimental design and prepare materials (e.g., agar plates,
fertilizer solution)
7•Set up and run experiment through the week*
8
•Harvest compost experiment*
•Microbial counts, protein analysis, dry and grind plant material
9
•Harvest hydroponic experiments*
•Microbial counts, protein analysis, dry and grind plant material
•Package and send plant material to Penn State for elemental analysis
10
•Introduction to data and graphical analysis for harvest biomass and
protein content
•Learn and utilize quantitative analysis to:
develop an understanding of the
importance of soil quality and
how agricultural methods impact
the nutritional value of food and
compare the nutritional value of
microgreens and vegetables
think critically about the potential of
microgreens to be a sustainably
cultivated source for human
nutrition
develop information literacy
11
•Analysis of elemental analysis data
•Locate published nutritional data for broccoli florets, and compare with
microgreen data
12
•Locate water usage and growth time data on industrial broccoli crops
•Quantitative analysis (Table 4, Appendix)
13
•Analytical discussions of microgreen data and their potential to be a
sustainably grown source of human nutrition
•Begin poster construction
14
•Introduction to abstract writing
•Poster construction
•Gain experience in communicating
scientific findings via both written and
oral means.
15 •Poster presentation
THE AMERICAN BIOLOGY TEACHER VOLUME. 79, NO. 5, MAY 2017
378
“to integrate concepts across levels of organization and complexity”
(NRC-NA, 2009) as they learn sub-cellular processes, such as plant
acquisition of nutrients during growth, and how this affects the
health of human populations.
Objectives 2 and 3 aim to empower students to use the data that
they generate along with published data to perform quantitative
analyses through which they can come to an informed consensus
on the potential of microgreens to be a nutrient-rich, sustainably
produced food. This exercise forces students to define what informa-
tion they need, how to acquire it, and how they will use it. This not
only works toward achieving information literacy (Table 1), which is
important to student performance and lifelong learning (Maughan,
2001), but also puts students in a position to improve their quanti-
tative skills in a biological context. This module demonstrates how
readily available facts can be utilized in problem solving, which is
an important role for contemporary higher education in the techno-
logical era (AAAS, 2011).
Module Implementation
A weekly schedule of module activities and associated desired stu-
dent outcomes are located in Table 2. For the first six weeks of the
semester, students were introduced to microgreens and methods of
cultivating them via class discussions, trial experiments, and writing
assignments (Table 2, Table 3). In class discussions and writing
assignments, students confronted the pros and cons of various culti-
vation methods, discovered that there was not much data in the pri-
mary scientific literature about microgreen nutrition, and compared
industrial and distributed agriculture. Trial experiments performed
Table 3. Writing assignments that were used to introduce students to microgreens or to engage them in
higher-level thinking about microgreen nutritional analyses and nutrient cycling. Students were provided
with a video link or an article and questions requiring a written response.
Assignment no. Video link/article Writing assignment questions
1
Cornell Small Farms: https://
www.youtube.com/watch?
v=JA8p5IT91H8
1. What is sustainable farming?
2. Based on the microgreen production process described in the Cornell
Small Farms video, do you think microgreen farming is sustainable? Why or
why not? Please provide specific examples in your response.
2
Xiao et al. (2012) 1. What types of microgreens did the authors study? How were the
microgreens grown, in soil, hydroponically, or some other way? Was any
fertilizer used?
2. What vitamins and other chemicals of nutritional value did the authors
measure in the microgreens?
3. For each of the four chemicals of nutritional value measured (see your
answers to question 2), why exactly is it beneficial for humans to consume
these; that is, what function do they perform in the human body?
4. The introduction to this article and many blogs that I have seen online say
that microgreens, in general, have much more nutritional value than
the vegetables that would be produced from mature vegetable plants.
Compare the amount of α-tocopherol in beet microgreens with that in
raw beets (the actual vegetable). You will need to do some research online
to find the latter.
5. Xiao et al. (2012) describe measuring the dry weight of the microgreens
that they worked with. Why is it important to determine the dry weight of
microgreens when examining their nutritional content?
3
Refsgaard et al. (2005) 1. What is a closed nutrient cycle?
2. Consider microgreens grown on compost and on hydroponic mats. Does
either method completely close nutrient cycles? Does one method close
nutrient cycles more than the other? Explain your answer with specific
examples.
3. Consider a world where 50% of the population in urban areas starts to
grow all of their “vegetables”as microgreens inside their homes (as we did
in the lab). Does this indoor “urban farming”make any progress toward
closing nutrient cycles relative to a situation where 100% of urban people
continued to eat vegetables grown using industrial agricultural methods
(that is, grown in rural areas out in the field, harvested and transported to
urban grocery stores)?
THE AMERICAN BIOLOGY TEACHER MICROGREEN FARMING & NUTRITION
379
on compost and hydroponic mats gave students preliminary data on
how quickly microgreens would grow under laboratory conditions,
how much water they would require, and the biomass yields that
could be anticipated. Based on this knowledge, students defined
research questions and designed an experiment to address them
under the guidance of a mentor (Figure 1).
Planting, growth, harvest, and laboratory analyses (protein con-
tent, microbial counts) took place over the next three weeks (six lab
periods, weeks 7, 8, and 9; Table 2). During weeks 10, 11, and 12
(Table 2), students analyzed their data to determine harvest biomass
(Figure 2a), microbial counts on microgreen surfaces (Figure 2b),
microgreen protein and water content, as well as total water or fertil-
izer solution application; they also located the published data that they
needed for comparative quantitative analyses (Figure 2c; Table 4).
Nutritional comparisons were performed using the elemental analysis
data obtained for broccoli microgreens and published nutritional data
Figure 2. Student-generated data for broccoli microgreens grown in three different ways (C = compost, HF = hydroponic-
fertilized, HW = hydroponic water): (A) average harvest biomass (N = 5) ± 1 SE; (B) average number of microbial colony-forming
units (CFUs) ± 1 SE; (C) nutritional ratios (microgreens: broccoli) for protein content and eight chemical elements. Statistically
significant differences among the growing treatments were examined for biomass yields and number of CFUs using a Welch’s
ANOVA followed by a Tukey’s post-hoc test (α= 0.05) in the program R (version 3.2.2, R Development Core Team, 2011). Elemental
analysis data obtained for microgreens was compared with published nutritional values of raw broccoli florets obtained from SELF
Nutrition Data (2014).
THE AMERICAN BIOLOGY TEACHER VOLUME. 79, NO. 5, MAY 2017
380
for raw broccoli florets (Figure 2c). Specific laboratory procedures and
materials are located below, and quantitative data analysis details are
located in Table 4 and the Appendix.
In the final three weeks of the semester (weeks 13, 14, and 15),
students considered all data analyses on nutritional value and
resource demand, and came to a consensus on whether or not
broccoli microgreen production and consumption posed advan-
tages over industrially producing and consuming broccoli florets
(Figure 2; Table 2). Students also constructed a poster detailing
their findings and conclusions. On the last day of class, they pre-
sented it at a symposium in the Department of Biological Sciences
at ISU.
Experimental Procedures and
Materials
Procedures and materials used to conduct the experiment outlined
in Figure 1 are described below. Quantitative manipulation of data
(e.g., dimensional analyses) to facilitate comparative analyses is
detailed in the Appendix.
Growing Microgreens
All growing and insert trays and humidity domes used in the experi-
ments were obtained from Handy Pantry (Salt Lake City, UT).
Table 4. Integrating quantitative analysis and information literacy to answer the following question: How
much water would be needed to grow a quantity of broccoli microgreens that is nutritionally equivalent to
the mass of broccoli (vegetable) produced on one acre of an industrial farm? *Calculated based on the
average of the microgreen: vegetable ratios displayed in Figure 2c for compost-grown microgreens.
What do we need to know to answer the
question?
Where can the information be found or
derived from?
Calculation and/or
quantity
Experi-mental
data Publ’d lit. Calculations
Relative nutritional value of broccoli
microgreens to broccoli (vegetable) XX
a
X1.85*
Mass of broccoli (vegetable) produced per acre
on an industrial farm X
b
X
800 boxes per acre
(23 lbs per box) = 18,400
lbs. = 8,346,100 g
Serving size of broccoli vegetable X
a
91 g
Servings of broccoli (vegetable) produced per
acre on an industrial farm X
a,b
X8,346,100 g / 91 g =
91,715 servings
Serving size of broccoli microgreens that is
nutritionally equivalent to a serving of broccoli
(vegetable)
XX
a
X
91 g / 1.85 = 49.2 g
Average mass of microgreens harvested from
25-sq.-inch trays X24 g
Amount of water applied to each 25-sq.-inch
tray from seed sowing to harvest X60 mL
Water applied to 1 acre of industrially produced
broccoli (vegetable) during growing season X
c
2,480 to 3,700 cubic
meters per acre
Number of 25-sq.-inch trays of broccoli
microgreens that would produce a harvest mass
that is nutritionally equivalent to that of broccoli
(vegetable) produced from 1 acre of industrial field.
XX
a,b
X
(91,715 servings × 49.2 g
microgreens per serving) /
24 g per tray = 188,016
trays
How much water would it take to cultivate
188,016 trays of broccoli microgreens? XX
188,016 trays × 60 mL
per tray = 11,280,960 mL
How many times more water would it take to
cultivate broccoli (vegetable) on an industrial
farm than broccoli microgreens? X X
c
X
2.48 × 10
9
mL /
11,280,960 mL = 220
3.7 × 10
9
mL / 11,280,960
mL = 328
a
SELF Nutrition Data (2014).
b
Björkman & Shail (2011).
c
Le Strange et al. (2010).
THE AMERICAN BIOLOGY TEACHER MICROGREEN FARMING & NUTRITION
381
Five grams of broccoli seed (Mountain Valley Seeds, Salt Lake
City, UT) was sowed in each of fifteen, 5 in. × 5 in. insert trays
containing compost or Micro-Mat Hydroponic Growing Pads
(Handy Pantry, Salt Lake City, UT). Five insert trays containing
compost (C) and five insert trays containing hydroponic mats
were watered with sterile deionized water (HW); a second set of
five insert trays containing hydroponic mats were watered with
a sterile fertilizer solution (HF; see Appendix). All insert trays
were placed into 10 in. × 20 in. black plastic growing trays for
incubation; HF and HW replicates were maintained in separate
growing trays to avoid contaminating the HW replicates with fer-
tilizer solution. After sowing, seeds were kept in the dark until
germination (ca. 36 hours) by placing a second set of trays over
the top of the growing trays. After germination, growing trays
were covered with clear humidity domes and incubated under
constant light produced by GE Plant and Aquarium Ecolux Bulbs
at room temperature. Lights were positioned ca. 6 inches above
the surface of the growth substrate. Sterile water or fertilizer solu-
tion (10 to 25 mL volumes) was applied to each insert tray as
needed during growth, using sterile serological pipets to minimize
microbial contamination. Compost was generated using a Worm
Factory and operating instructions from Uncle Jim’s Worm Farm
(Spring Grove, PA) two months prior to setting up experiments.
Harvesting Microgreens
Microgreens were harvested 7 days (C) or 14 days (HF and HW)
after sowing using ethanol-cleaned scissors to cut the stems as
close to the growth substrate as possible. Microgreens were
weighed immediately on an analytical balance to determine the
total fresh weight in grams (gfw). From each experimental repli-
cate, ca. 0.1 gfw was placed into a protein extraction filter car-
tridge (see “Protein analysis,”below), and 0.150 to 0.230 gfw
were placed into 10 mL conical tubes containing 5 mL of sterile
1X phosphate buffer (see Appendix) for washing microbes from
the microgreen surfaces to determine microbial counts. The
remaining biomass was weighed and placed into a drying oven
at 80°C for 48 hours, after which the microgreens were weighed
again to determine their water content.
Elemental Analysis
Dried microgreens (2 g per treatment) were ground in a mortar and
pestle and sent to the Pennsylvania State Agriculture Analytical
Services Program (University Park, PA). Each of the three compos-
ite samples, one per growing treatment, contained equal masses of
plant material from each of the five experimental replicates.
Protein Analysis
Protein was extracted from microgreens using materials and the pro-
tocol supplied in the Minute
TM
Total Protein Extraction Kit for Plant
Tissues (Invent Biotechnologies, Eden Prairie, MN). Protein concen-
tration in extracts was determined using the colorimetric assay of the
Pierce
TM
BCA (bicinchoninic acid) Protein Assay Kit (Pierce Biotech-
nology, Rockford, IL) and a Thermo Scientific Evolution 60 Spectro-
photometer. Protein standards for calibration were constructed
according to protocols of the protein assay kit, using denaturing lysis
buffer from the protein extraction kit as a diluent. Protein content
was also determined for broccoli seeds and locally obtained, raw
broccoli florets.
Microbial Counts
Microgreens placed into conical tubes containing 5 mL of 1X phos-
phate buffer were rotated on a LABQUAKE ® Rotisserie (Barnstead
Thermolyne) for 45 minutes. Phosphate-buffer-containing microbes
(100 µL) was serially diluted seven times for each of the 15 experi-
mental replicates. From each of the seven serial dilutions, 25 µL was
spreadplated onto a tryptic soy agar (TSA; Sigma Aldrich) plate for
enumerating colony-forming units (CFUs). Plates were inverted and
incubated for 48 hours at room temperature. CFUs were counted
on the lowest dilution plate containing a countable number of CFUs
for each of the 15 microgreen samples.
Discussion
Module objectives were accomplished as evidenced by the students’
successful completion of writing assignments, data analyses, and
a poster detailing their findings and conclusions. Although the
compost-grown microgreens had less protein than those grown
hydroponically, students argued that the substantially higher quanti-
ties of several nutritionally important elements in compost-grown
microgreens (Figure 2c) in combination with lower average microbial
loads (Figure 2b), higher biomass yields (Figure 2a), lower water
requirements, and faster generation times made the case for growing
microgreens on compost rather than hydroponic mats. In the writing
assignment based on Refsgaard et al. (2005), students articulated that
using compost made it possible to capture nutrients from kitchen
scraps in microgreens, thus helping to close nutrient cycles and bol-
stering the case for growing microgreens on compost rather than on
hydroponic mats. The students demonstrated a new respect for soil
quality in pointing out that compost-grown microgreens contained
much higher amounts of some nutritionally important elements, such
as potassium; without prompting, they began to speculate about the
connection between the high potassium content of compost-grown
microgreens and the large number of banana peels that went into
the compost that we used in the experiment.
Students utilized their data to support claims in the popular lit-
erature that microgreens may be more nutritious than vegetables
with respect to some nutritionally important elements, but were able
to qualify their statements by indicating that this would be highly
dependent upon the growing method (Figure 2c). In addition to
requiring no fertilizer, analyses indicated that growing broccoli
microgreens on compost may require 220 to 328 times less water
than industrially produced broccoli in California’s Central Valley
(Table 4). In addition to their relatively high nutritional value, com-
post-grown microgreens may require smaller quantities of resources
than industrially grown broccoli florets. Students also discussed that
consuming microgreens could result in less waste, as people eat the
entire plant, rather than eating only broccoli florets and throwing
away the stems, as commonly occurs.
There are several ways in which this module could be adapted to
address different research questions. Given the scarcity of nutritional
data on microgreens, students could generate novel data by conduct-
ing nutritional analyses on a wide variety of microgreens. Addition-
ally, within soil/compost-based and hydroponic growing methods,
there are numerous variations that could also be examined for their
impact on microgreen nutrition (i.e., varied composting methods
and materials, alternative fertilizer solutions).
THE AMERICAN BIOLOGY TEACHER VOLUME. 79, NO. 5, MAY 2017
382
Although this module was implemented in Biology II Laboratory,
it could be adapted for upper-level undergraduates who have more
research experience and/or are pursuing advanced study in plant scien-
ces. Much remains that is poorly understood with respect to seedling
physiology, especially how that might translate to the nutritional value
of a crop for human consumption. For instance, the protein content
of seedlings can vary widely depending on the growing conditions
(Nelson & Millar, 2015), and plants are known to directly take up
available amino acids (Sauheitl et al., 2009)—something to consider
adding to hydroponic fertilizer solution.
Conclusions
Student interest in this module was piqued by the fact that it allowed
them to do research in the context of a real-world biological problem
that affects human and environmental health. This module also gave
students direct experience with growing plants in ways that avoided
many of the cons of industrial agriculture (e.g., fertilizer, pesticide-
use, high water and fossil fuel demand), and a couple of the students
reported that they had plans to start growing microgreens them-
selves. On the basis of quantitative data, much of which is at our fin-
ger tips, this module demonstrated to students that everyone can
make informed choices that feedback positively on human and envi-
ronmental health.
Acknowledgments
Experiments were conducted by AMOEBA (Authentic Mentoring Of
Engaged Biologists Alliance; NSF DUE 1140286, J.P. Hill), which
incorporated discovery research into the introductory biology curric-
ulum at ISU. I thank Jason T. Werth for superb technical support. Any
opinions, findings, conclusions, or recommendations expressed
within are solely the author’s and do not necessarily reflect the views
of the National Science Foundation. This article was written in fond
memory of Myrtle Camille Bart, whose love for plants lives on.
References
AAM (American Academy of Microbiology). (2012). How Microbes Can
Help Feed the World: Report on an American Academy of Microbiology
Colloquium. Washington, DC. Retrieved from http://academy.asm.org/
index.php/browse-all-reports/800-how-microbes-can-help-feed-the-
world
AAAS (American Association for the Advancement of Science). (2011).
Vision and Change in Undergraduate Biology Education: A Call to
Action. Retrieved from http://visionandchange.org/finalreport/
ACRL (Association of College and Research Libraries). (2000). Information
Literacy Competency Standards for Higher Education. American Library
Association. Retrieved from http://www.ala.org/acrl/standards/
informationliteracycompetency
Björkman, T. & Shail, J. (2011). Eastern Broccoli Project. Retrieved from
http://www.hort.cornell.edu/bjorkman/lab/broccoli/WNYBrocyield
potential.pdf
Evans, S., Valsecchi, F., Pollastri, S. (2012). Eco-urban agriculture:
Design for distributed and networked urban farming in Shanghai.
Paper presented at Cumulus, Helskinki, Finland, 24–26 May 2012
(pp. 1–14).
Foreman, S. L., & Steen, L. A. (1999). Beyond eighth grade: Functional
mathematics for life and work. Research report. Berkeley, CA: National
Center for Research in Vocational education.
Kim, K., & Lauder, T. S. (2013, February 23). 261 California drought maps
show deep drought and current recovery. Los Angeles Times. Retrieved
from http://www.latimes.com/science/la-me-g-california-drought-map-
htmlstory.html
Le Strange, M., Cahn, M. D., Koike, S. T., Smith, R. F., Daugovish, O.,
Fennimore, S. A., . . . & Cantwell, M. I. (2010). Broccoli Production in
California. University of California Agriculture and Natural Resources
Communication Services. Retrieved from http://anrcatalog.ucanr.edu/
pdf/7211.pdf
Massey, W. E. (1989). Science education in the United States: What the
scientific community can do. Science, 245, 915–921.
Maughan, P. D. (2001). Assessing information literacy among
undergraduates: A discussion of the literature and the University of
California-Berkeley assessment experience. College and Research
Libraries, 71–85.
Metson, G. S., Wyant, K. A., & Childers, D. L. (2013). Introduction to
P Sustainability. In K. A. Wyant, J. R. Corman, & J. J. Elser (Eds.),
P Sustainability in Phosphorus, Food, and Our Future (pp. 1–19).
New York: Oxford University Press.
NRC (National Research Council). (2003). BIO2010: Transforming
undergraduate education for future research biologists. Washington,
DC: The National Academies Press.
NRC-NA (National Research Council of the National Academies). (2009).
A New Biology for the 21st Century. Washington DC: National
Academies Press.
Nelson, C. J., & Millar, A. H. (2015). Protein turnover in plant biology.
Nature Plants. doi:10.1038/nplants.2015.17
Opara, L. U. (2003). Traceability in agriculture and food supply chain:
A review of basic concepts, technological implications, and future
prospects. Food Agriculture and Environment, 1(1): 101–106.
R Core Development Team. (2011). R: A Language and Environment for
Statistical Computing. Vienna: Author.
Refsgaard, K., Jenssen, P. D., & Magid, J. (2005). Possibilities for closing the
urban-rural nutrient cycles. In N. Halberg, H. F. Alrøe, M. T. Knudsen, &
E. S. Kristensen (Eds.), Global Development of Organic Agriculture:
Challenges and Promises (pp. 1–34). Wallingford, UK: CABI Publishing
Rickman, J. C., Barrett, D. M., & Bruhn, C. M. (2007). Nutritional comparison
of fresh, frozen and canned fruits and vegetables. Part 1. Vitamins C
and B and phenolic compounds. Journal of the Science of Food and
Agriculture, 87, 930–944.
Sauheitl, L., Glaser, B., & Weigelt, A. (2009). Uptake of intact amino acids by
plants depends on soil amino acid concentrations. Environmental and
Experimental Botany, 66(2), 145–152.
SELF Nutrition Data, know what you eat. (2014). Retrieved from http://
nutritiondata.self.com/facts/vegetables-and-vegetable-products/2356/2
Schultheis, E. H., & Kjelvik, M. K. (2015). Data nuggets: Bringing real data
into the classroom to unearth students’quantitative and inquiry skills.
American Biology Teacher, 77(1), 19–29.
Treadwell, D., Hochmuth, R., Landrum, L., & Laughlin, W. (2010).
Microgreens: A New Specialty Crop. University of Florida IFAS
Extension HS1164.
UNESCO. (2003). The United Nations decade for education for sustainable
development. United Nations Educational, Scientific, and Cultural
Organization. Retrieved from http://portal.unesco.org/education/en/ev.
php-URL_ID=26295&URL_DO=DO_TOPIC&URL_SECTION=201.html
U.S. Department of Education. (1996). Remedial education at higher
education institutions in fall 1995. NCeS 97-584. Washington, DC:
National Center for education Statistics.
Walker, B., & Salt, D. (2006). Living in a Complex World. In Resilience
Thinking (pp. 1–38). Washington, DC: Island Press.
THE AMERICAN BIOLOGY TEACHER MICROGREEN FARMING & NUTRITION
383
Wallin, C. (2013). Growing Microgreens for Profit. Anacortes, WA: Headstart
Publishing, LLC.
Warner, J. (2012). Tiny Microgreens Packed with Nutrients. WebMD.
Retrieved from http://www.webmd.com/diet/20120831/tiny-
microgreens-packed-nutrients
Weaver, G. C., Russell, C. B., & Wink, D. J. (2008). Inquiry-based and
research-based pedagogies in undergraduate science. Nature Chemical
Biology, 4, 577–580.
Xiao, Z., Lester, G. E., Luo, Y., & Wang, Q. (2012). Assessment of vitamin
and carotenoid concentrations of emerging food products: Edible
microgreens. Journal of Agriculture and Food Chemistry, 60,
7644–7651.
Xiao, Z., Nou, X., Luo, Y., & Wang, Q. (2014). Comparison of the growth of
Escherichia coli O157:H7 and O104:H4 during sprouting and microgreen
production from contaminate radish seeds. Food Microbiology, 44, 60–63.
CAROLYN F. WEBER studies in the College of Health Sciences, Des Moines
University, Des Moines, IA 50312, USA; e-mail: Carolyn.F.Weber@dmu.edu
APPENDIX
DATA MANIPULATIONS TO FACILITATE COMPARATIVE ANALYSES
Some data manipulation is necessary to facilitate comparative analyses of elemental and protein contentrations as well as micro-
bial counts of microgreens grown using varied methods. Such manipulation is also necessary to compare nutritional data for
microgreens to published nutritional data for vegetables. These manipulations are detailed below.
Water content: Protein and elemental concentration of plant materials are generally reported for the gram dry mass of material,
because the water content of the microgreens may vary and water is not a structural part of the plant material. Therefore, the
water mass is usually subtracted before comparing protein and elemental contentrations in plant materials.
To determine the water content of plant material, measure the masses of the following: empty foil weigh boat (foil mass),
foil weigh boat with freshly harvested microgreens (foil + plants), and foil weigh boat with plants after they have been dried
(foil + dry plants).
Mass of fresh plants is usually denoted “gfw”(grams fresh weight) and is calculated as follows:
•(foil + fresh plants) –(foil) = gfw
Mass of dry plants is usually denoted “gdw”(grams dry weight) and is calculated as follows:
•(foil + dry plants) –(foil) = gdw
The percent water content is calculated as follows:
•[1 –(gdw / gfw)] × 100 = % water content
Microbial counts: Using the protocol in the main text, a known mass of plant material is placed into phosphate buffer to
wash the microbes from its surfaces. The phosphate buffer is then serially diluted 10-fold in sterile phosphate buffer, seven
times. Then, each serial dilution is spread-plated onto an agar plate. To determine the number of microbes on the plant
material, students should examine all seven plates for a given plant sample and count the number of colonies on the lowest
dilution that they can count (i.e., not a bacterial lawn). In the lab make sure students record the following information:
•number of colonies on the plate that they count
•serial dilution on the plate on which they counted colonies
•mass of plants from which microbes were extracted
•volume of phosphate buffer that the plants were placed into
•volume spread-plated from each serial dilution.
As an example, let’s assume that 1 gfw of plant material was placed into 5 mL of phosphate buffer. The phosphate buffer
containing microbes was serially diluted. From each serial dilution, 25 µL was plated onto an agar plate. Let’s say that
50 colonies were counted on the plate that received 25 µL of 1000-fold dilution. This means that the 1000-fold dilution
had 2 colonies/µL.
To calculate the number of microbes in the original phosphate buffer extract (undiluted) containing the plant material:
•(2 colonies / µL of 1000-fold dilution) × 1000 = 2000 colonies / µL of undiluted extract
•2000 colonies / µL of undiluted extract × 5000 µL total volume = 10,000,000 colonies extracted from plant material
This means that there were 10,000,000 microbes on 1 gfw of plant material.
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Protein concentration: Determining the protein concentration of plant material using the colorimetric method described in the
main text makes use of concepts that are usually presented in General Chemistry, such as Beer’s Law; it might be helpful to
review this with students so that they understand how the spectrophotometer works. When students are collecting data in
the lab, make sure that they know the following information:
•mass of plants used in the protein extraction
•water content of plants
•protein concentration and spectrophotometric absorbance of each standard used to create a standard curve
•spectrophotometric absorbance of each protein extract from plant material
•total volume of the protein extract.
The first step in determining the protein concentration in the protein extracts from plant materials is to plot the absorbance
values for the protein standards as a function of their concentration. For example:
The linearity of the standard curve should be examined by calculating the R
2
value, and the equation of the line should be
calculated. Most graphing programs will do this for you, as in the example graph above.
Depending on their familiarity with linear equations, students may need to be introduced to the equation of a line and what
the variables mean:
•y=mx+b
where y = any y-value on the graph, x = the corresponding x-value, m = slope of the line (y / x), and b = the y-intercept
(when x = 0).
Students may need help applying this information to calculating the protein concentration in their protein extracts. Remind
them of what they know (absorbance, y), what they are looking for (concentration, x), and that the equation of the line pro-
vides m and b. Therefore, all they need to do is plug in their absorbance values for y and solve for x.
This calculation will give them the protein concentration of the protein extract that was put into the colorimetric reaction,
so determining the protein content of the plants requires a few more quantitative manipulations. As an example, let’s assume
that 50 µL of protein extract was placed into the colorimetric reaction, and based on the standard curve, it was determined that
this extract has a concentration of 1000 µg protein / mL. This means that the protein extract had a concentration of 1 µg
protein / µL.
If the total volume of the protein extract was 100 µL, then you would calculate the total mass of protein extracted from the
plants as follows:
•(1µg protein / µL) × 100 µL = 100 µg of total protein extracted
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385
If protein was extracted from 0.1 gfw plant material, this means that the protein content of plant material is:
•100 µg protein / 0.1 gfw = 1000 µg protein / gfw
To compare protein contents across plant samples (across which water content may vary), it is necessary to calculate the protein
content in terms of protein mass / gdw. For this calculation, let’s assume that the water content of the plants was 90%. This
means that if 0.1 gfw was placed into the extraction, the gdw in the extraction was:
•0.1 gfw × (1 –0.9) = 0.01 gdw
This means that the protein content per gdw was:
•100 µg total protein extracted / 0.01 gdw = 10,000 µg protein / gdw
Elemental analysis: The elemental analysis data for microgreens obtained from the Penn State Agricultural Analytical Services
Laboratory were returned in two forms: percent or parts per million. For comparison to the nutritional data for vegetables,
which are going to be listed per gfw, these data need to be converted to mass of element / gfw.
Considering percentage data first, we can calculate what they mean in the context of 1 gdw. (Use gdw because the plant
material for the elemental analysis was dry.) Let’s assume we are talking about a plant sample that contains 2% iron (Fe):
•0.02 × 1 gdw = 0.02 g Fe / gdw
Now, if we want to determine the Fe concentration in fresh plants, we need to know the percent water content. Let’s assume
that the percent water content of this plant sample was 90%; this means that 10% of the sample weight was plant material or
gdw. So:
•1 gdw = (0.1) × X gfw
X = 10 gfw
If 1 gdw (which equates to 10 gfw) contained 0.02 g Fe, then the Fe concentration in a fresh plant sample could be calculated as:
•0.02 g Fe / 10 gfw = 0.002 g Fe / gfw
Now, let’s consider the case where the elemental concentration is provided as parts per million (ppm). If you take 1 g and divide
that into 1 million parts, you get 0.000001 g, which is the equivalent of 1 µg. This means that a plant sample of 1 gdw that
contains 4 ppm manganese (Mn) has 4 µg Mn / gdw. If you want to put this in terms of what the elemental concentration
is in terms of fresh weight, you need to take the water content into consideration as above. Let’s assume, again, that the plants
had a water content of 90%:
•1 gdw = (1 –0.9) × X gfw
X = 10 gfw
In this case, there are 4 µg Mn for 10 gfw, or:
•4 µg Mn / 10 gfw = 0.4 µg Mn / gfw
CHEMICAL COMPOSITION OF FERTILIZER AND PHOSPHATE BUFFER
Dilute fertilizer solution applied to hydroponic mats in the HF treatment:
1X phosphate buffer:
0.025 M Na
2
HPO
4
0.011 M KH
2
PO
4
1.07 mM NH
4
NO
3
0.015 mM KH
2
PO
4
1.96 µM MgSO
4
7H
2
O
0.72 µM CaCl
2
2H
2
O
0.4 µM FeSO
4
7H
2
O
0.28 µM sodium EDTA 2H
2
O
5.9 nM MnSO
4
H
2
O
5.9 nM CuSO
4
5H
2
O
7.2 nM ZnSO
4
7H
2
O
0.12 µM H
3
BO
3
0.12 nM (NH
4
) 6Mo7O
2
4H
2
O
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