1
EXPOSURE OF PLANTS TO STATIC
2
ELECTROMAGNETIC FIELDS:
3
THE EARLY GROWTH OF BASIL AND WAXY CORN
4
5
Running head: Exposure of Basil and Corn to Static Electromagnetic Fields
6
7
Punchalee Montriwat and Taweetham Limpanuparb*
8
9
Science Division, Mahidol University International College
10
999 Phutthamonthon 4 Road, Salaya,
11
Nakhonpathom, Thailand 73170. Tel. 02-441-5090 ext 3538; Fax. 02-441-9092;
12
Email: [email protected]
13
* Corresponding author
14
15
Abstract
16
Effects of static low-intensity electromagnetic field (EMF) on higher plants
17
were investigated. Thai basil (Ocimum basilicum var. thyrsiflora) and waxy
18
corn (Zea mays var. ceratina) were chosen as samples for the experiments.
19
There were two methods of electromagnetic exposure, indirect exposure (grow
20
the plants by using magnetically treated water) and direct exposure (grow the
21
plants under the electromagnetic field). For indirect exposure experiment
22
(0.3–6.77 mT), magnetically treated water was applied to Thai basil seeds once
1
23
a day for 7 consecutive days and the experiment was repeated once. No
24
significant difference in the heights was found between control groups and
25
treated groups whether DI or tap water was used. For direct exposure
26
experiment (0.16–4.80 mT), waxy corn seeds were grown between a pair of
27
electromagnets. Two controls were grown in absence of extra magnetic field;
28
one control group (No EM) was grown at room temperature while the other
29
control group (EM-0) was grown between a pair of electromagnets with similar
30
temperature to other magnetically treated groups.
31
completed in 4 days and was repeated once. Results indicated that there is no
32
height difference between control (EM-0) and the groups grown in
33
electromagnets; however, the controls (No EM), which was grown at room
34
temperature, were significantly shorter compared to those grown between
35
electromagnets. Our results suggest that the level of applied magnetic field has
36
no effect on the heights of the plants in this study.
The experiment was
37
38
Keywords: Magnetotropism, magnetically treated water, static magnetic field,
39
microwave
40
41
Introduction
42
Natural magnetic field (MF) is an environmental factor that living organisms can
43
hardly escape. Earth's MF or geomagnetic field (GMF) is a persistent natural
44
phenomenon throughout the evolution of all species. At present, GMF is static,
45
slowly varying, relatively homogeneous and weak. It ranges from below 30 µT in
2
46
the area of South Atlantic anomaly near the equator to almost 70 µT close to the
47
magnetic poles in south of Australia and in Northern Canada (Maffei, 2014). GMF
48
is known to act on living system and influence numerous biological processes
49
(Feychting, Ahlbom, and Kheifets, 2005).
50
Nowadays in a modern society, aside from the GMF, human has been
51
introducing a vast and growing range of man-made electromagnetic field (EMF),
52
which are physical fields generated by flows of electric current through an electrical
53
conductor. This results in growing concerns of their effects on biological systems.
54
Magnetic resonance imaging (MRI) and hair dryer are examples of exposure
55
sources, which release static EMF of ~3 T (inside) and ~6-2000 µT (30 cm away)
56
respectively (Feychting et al., 2005). Although initially considered too weak and
57
incapable of inducing physiological function of biomolecular systems, numbers of
58
studies suggest otherwise (Adey, 1993).
59
MF drew attention from scientists in various fields on its effects on living
60
organisms. It was suggested that MF acts in a similar cellular metabolic pathway
61
as invasive factors like osmotic (Munns, 2002), heat (Ruzic, and Jerman, 2002;
62
Sabehat, Weiss, and Lurie, 1998), or salt stress (Munns, 2002). There are attempts
63
to explain the effects of MF on living systems; magnetotaxis is widely studied in
64
insects, birds and mammals while magnetotropism is observed in some plants
65
(Galland and Pazur, 2005; Maffei, 2014; Occhipinti, De Santis, and Maffei, 2014;
66
Zhadin, 2001).
67
From experiments of exposing different subjects to a variety of types of MF
68
with wide spectrum of intensities, both significant changes and null results were
3
69
obtained. When shallot (Allium ascalonicum) sprouts were subjected to a static MF
70
of 7 mT for 17 days, increase in symplastic antioxidant enzyme activities exposed
71
and non-enzymatic antioxidant levels together with changes in leaf apoplast
72
compared to unexposed sprouts were observed (Cakmak, Cakmak, Dumlupinar,
73
and Tekinay, 2012). In okra (Abelmoschus esculentus) seeds, MF treatment of 99
74
mT for 3 or 11 min exhibited enhancement in germination percentage, numbers of
75
flowers, fruits, and seeds per plants, leaf area, height, and pod mass per plant (Naz
76
et al., 2012). In a blind experiment, hypocotyl lengths, gene (CHS, HY5, GST)
77
expression levels, blue-light intensity effects, and influence of sucrose in the growth
78
medium of Arabidopsis thaliana grown in MF of 1 mT, 50 mT, and approximately
79
100 mT were studied and no consistent, statistically significant responses of MF
80
were detected (Harris et al., 2009). By treating corn (Zea mays) seedlings with
81
static MF of 100 mT for 1 h or 200 mT for 2 h, it was found that growth and root
82
parameters, photosynthesis rate, stomatal conductance, and chlorophyll content
83
increased, while antioxidant enzyme activities decreased (Anand et al., 2012).
84
Increases in germination rate, height, and weight were found when corn seeds were
85
magnetically exposed to 125 or 250 mT of MF for different period of time (Flórez,
86
Carbonell, and Martínez, 2007). Under field conditions, a randomized design study
87
found that pre-sowing exposure of corn seeds to static MF (100 mT for 2 h and 200
88
mT for 1 h) was effective in improving all growth measures. Length, fresh weight,
89
and dry weight of leaves, shoots, and roots significantly increased (Shine and
90
Guruprasad, 2012). Limpanuparb (2001) also reported an increase in the heights of
91
corn seedling, which were grown between electromagnets for 4-5 days.
4
92
Some experiments were done indirectly through water that was previously
93
exposed to MF, “magnetically treated water” (MTW). There were claims that MF
94
help to descale metal surfaces, improve hydration of cement, alter ζ potential of
95
colloids, accelerate growth of plants, enhance calcium efflux through
96
biomembranes, or modify the structure of model lyposomes (Colic and Morse,
97
1999). Besides, in 2006, there was a claim that applying microwaved water can be
98
fatal to the plant (“Microwaved water - see what it does to plants”, 2015). Despite
99
a long history of research on the effects of MF on properties of water and biological
100
systems, the topic remains controversial and the true mechanism remains elusive.
101
A comprehensive review can be found in Montriwat’s report (Montriwat, 2015).
102
This study explored how different intensities of EMF affect first stage
103
growth of higher plants when applied directly and indirectly through MTW. Only
104
low intensities EMF (0.3–6.77 mT) was used and the experiments were done under
105
controlled laboratory condition.
106
107
Materials and Methods
108
There are are two main considerations for the design of our experiments, magnetic
109
field sources and model plants.
110
Firstly, electromagnets were chosen as a source of static MF due to its
111
resemblance to exposure condition in everyday life and convenience in controlling
112
strength and homogeneity of the MF. Electromagnets can also generate pulse or
113
frequencies of the magnetic field but these are beyond the scope of the current
114
study.
As electromagnets are operated by electrical current passing through
5
115
conductor coils, some heat is always released from the EMF apparatus. The amount
116
of heat usually correlates with the strength of the magnetic field and can be
117
considered an inseparable factor in household EMF exposure conditions.
118
Recognizing that reports on effects of magnetic field on biological systems are
119
controversial and heat may be a confounding variable, we designed our
120
electromagnets such that all of them generate the same amount of heat with varied
121
EMF intensity in a range found in domestic electrical appliances.
122
The second consideration is on the application of electromagnetic fields to
123
model plants. There are two modes of application, indirect and direct exposure.
124
Water was used as a medium to receive magnetic treatment in indirect exposure.
125
On the contrary, for direct exposure, plants were grown directly in the EMF
126
chamber. The exposure chamber of our apparatus is constrained to a volume of 7
127
× 7 × 7 cm3 because we aimed for high intensity and homogeneous magnetic filed.
128
Choices of model plants, growing medium, duration of experiment, and growth
129
measurement must accommodate this space limitation. For early growth of plant,
130
it is not practical and not required to put them in soil so we grew seeds on paper
131
and only watered them. The growth measurement can be either height or dry mass
132
but for tiny seedling it is inefficient to use dry mass. Even in the controlled
133
laboratory conditions, variations in temperature, lighting, humidity and other
134
factors may exist. Two batches were performed for each experiment to confirm the
135
results. Comparison of heights are valid only within the same batch.
136
Preparation of electromagnetic field
6
137
The EMF was generated by four pairs of electromagnets made by 1000
138
turns of 28 SWG copper wire (diameter = 0.376 mm, manufactured by Hitachi)
139
wound around square iron blocks (7 cm × 7 cm × 2.5 cm). The iron blocks were
140
the same as Limpanuparb (2001) but we designed the electromagnet so that all the
141
coils have equal number of turns of copper wire, thus dissipating similar amount of
142
heat. For each pair, two identical coils were positioned in parallel, 7.0 cm apart, in
143
the same area with same temperature.
144
The diagram and physical set up of EMF is shown on Figure 1. For indirect
145
exposure and direct exposure, total current of 1.20 A and 1.00 A was supplied
146
respectively to the four coils by a DC power supply (GW Instek, model: GPS-
147
3030DD). The temperature between electromagnets was 30°C (± 0.9°C) while room
148
temperature was maintained at 26°C (± 0.5°C) during the course of the experiment.
149
A lower current was used for direct exposure experiment because, in a pilot study,
150
it was found that a current of 1.20 A resulted in a temperature that was too high for
151
maize seeds, which was grown between copper coils, to germinate. About 4.85 W
152
and 3.36 W were generated by each copper coils during indirect and direct exposure
153
experiment, respectively. This is because an electromagnet has the windings
154
resistance, and electrical power is released as heat in a process called Joule heating
155
or ohmic heating (Knirsch, dos Santos, de Oliveira Soares Vicente, and Penna,
156
2010).
157
Opposite direction of turns (CW and CCW) generates MF of opposite
158
direction, which cancels each other out and results in different intensities of MF
159
among each magnetically treated group (0.30–6.77 mT for indirect exposure and
7
160
0.16–4.80 mT for direct exposure). Theoretically, control (EM-0) should produce
161
equal amount of heat as other MT groups and should not create any extra MF at all.
162
However, the maximum MF obtained was found to be 1.6 G, which is about 2.7
163
times of GMF. The values of MF were measured between the air gaps using AC/DC
164
gauss meter (Lutron, model: MG-3002). The properties of each pair and magnetic
165
flux densities are described in Table 1–2.
166
Plant sample and statistical analysis
167
Preliminary germination tests were done on seeds of rice (Oryza sativa),
168
Thai basil (Ocimum basilicum var. thyrsiflora), water convolvulus (Ipomoea
169
aquatic Forsk var. reptan), mung bean (Vigna radiata), and sunflower (Helianthus
170
annuus). It was found that Thai basil (obtained from Chia Tai Co., LTD) have the
171
highest germination rate and the lowest variation on stem height. Therefore, it was
172
chosen for indirect exposure experiment.
173
experiments, waxy corn (Zea mays var. ceratina obtained from Silverseed
174
Company) were used to allow comparison with the earlier report of Limpanuparb
175
(2001). The two species may be regarded as a representation of eudicot and
176
monocot plants. The number of seeds per treatment or control group is 50 and 20
177
for indirect and direct exposure experiments respectively and experiments were
178
repeated once. The stem heights of germinated seeds were measured after 7 days
179
(168 h) and 4 days (96 h) for indirect and direct exposure respectively.
180
Ungerminated seeds were considered as outliers and were not taken into account.
181
One-way analysis of variance (ANOVA) in PASW Statistics 18 was used to
8
However, for direct exposure
Scheffé’s method were used for mean
182
identify differences between groups.
183
comparisons because of unequal sample sizes.
184
Indirect exposure experiments
185
Both deionized (DI) water and tap water were used in the experiments to
186
explore if impurities in the field condition may affect the result. Firstly, four glass
187
jars were each filled with 100 ml water and exposed to MF between pairs of
188
electromagnets for 24 h while the control (No EM) group was left outside. For
189
microwaved water, 200 mL of water containing 4-5 boiling chips was heated up to
190
about 80°C by 700 W microwave (Samsung, model: M1817N, maximum 850 W)
191
for 1.5 min. All of the treated water was left outside electromagnet to cool down
192
to room temperature before application to the seeds. Both MTW and control water
193
were freshly prepared every day.
194
For each group, 50 Thai basil seeds were sown on tissue papers in styrofoam
195
trays in which small holes were made throughout to drain water. Every tray was
196
covered with another styrofoam tray to reduce evaporation and interference from
197
the environment. On the first day, 30 mL of treated or untreated water was poured
198
to the assigned group while sowing on tissue papers. From day 2 to 6, seeds were
199
watered with 10 mL of the magnetically treated, microwaved, or control water at
200
the same time every day.
201
Direct exposure experiments
202
The procedures of the direct exposure experiment were based on that of
203
Limpanuparb (2001) with only the modification on the electromagnetic filed
204
source. Waxy corn seeds were soaked in tap water for 24 h before planting. Only
9
205
20 seeds may be assigned to each group due to limited space of the magnetic field.
206
Ten seeds were evenly placed on A5 paper and covered with tissue papers and
207
watered with 20 mL of tap water. After that, the paper with seeds was carefully
208
rolled. For each group, two paper rolls were wrapped in the same plastic bag. Each
209
plastic bag was placed vertically in the glass jar between the pairs of electromagnets
210
except for the control (No EM), which was left in a glass jar outside electromagnet.
211
212
Results and discussion
213
Indirect exposure
214
Watering Thai basil seeds with water treated with 0.3–6.77 mT MF or
215
microwave once a day had no observable effect on its height after 168 h. Similar
216
results were obtained whether DI or tap water was used. The number of germinated
217
seeds whose stem lengths were recorded are shown in Table 3. In the first trial
218
using DI water, the EM-1000 group yielded highest mean of 1.94 cm while the
219
microwave group yielded lowest mean of 1.71 cm. The null hypothesis, which
220
stated that there is no difference between the mean stem heights of each groups,
221
was rejected by F-test (p-value = 0.023) suggesting that at least one pair of the mean
222
heights is different. However, after performing post hoc tests, Scheffé’s test
223
showed that the mean heights of all groups were the same. F-test for second trial
224
of DI water and both batches of tap water confirmed that the difference was not
225
statistically significant. Bar charts of the results are shown in Figure 2.
226
There is a skeptical attitude toward the mechanism that MF changes
227
properties of pure water, which does not contain any significant amount of
10
228
ferromagnetic or paramagnetic substances (Bogatin, Bondarenko, Gak, Rokhinson,
229
and Ananyev, 1999). Srisuthikul (2001) observed no change in the surface tension
230
of water circulating through 2000 G and 4000 G magnetic fields. Therefore, to
231
investigate whether the MF effect exists based on interaction between water and
232
ions or minerals and to simulate field conditions, the experiment was also conducted
233
using tap water.
234
Our results were in contrast with some reports in which an increase in
235
several parameters including height, weight, yield, and germination percentage
236
were reported when watered with MTW compared to control (El-Yazied, El-
237
Gizawy, Khalf, El-Satar, and Shalaby, 2012).
238
experiments were done under the field conditions, several possibilities such as ions
239
suspended in irrigation water, uncontrolled temperature, stage of plant growth and
240
duration of the experiment may contribute to this contradictory results. Moreover,
241
it is possible that different species of plant may have different susceptibility to
242
EMF. It is also well accepted that positive and significant results are more likely
243
to be published; hence, null results are relatively rare in the literature.
244
Direct exposure
Since some of the previous
245
For direct exposure of waxy corn seeds exposed to MF of 0.06–4.80 mT for
246
96 h, the null hypothesis stating that all groups have the same mean stem height
247
was rejected by F-test in both trials suggesting difference among groups exists (p-
248
value = 0.000). Scheffé's post hoc comparison confirmed that the mean height of
249
control (EM-0) group was not different from other EM groups (p-value ≥ 0.052)
250
(Figure 3). Nonetheless, it was found that the mean height of control (No EM) was
11
251
significantly lower than other groups in electromagnet (p-value ≤ 0.023) except for
252
EM-1000 (p-value = 0.241) in the first trial and control (EM-0) (p-value = 0.362)
253
in the second trial. Since control (EM-0) was not different compared to other EM
254
groups, evidently the difference between EM group and control reported earlier by
255
Limpanuparb (2001) are due to ohmic heat from electromagnets, not from the MF
256
itself as the temperature difference can be as large as 4.6°C (30.4°C between
257
electromagnet and 25.8°C outside the coils).
258
experiment, the diverse effects of electromagnets reported in the literature are
259
simply due to heat.
It is possible that, like in this
260
261
Conclusion
262
No significant difference was observed in the height of plants (waxy corn and Thai
263
basil) exposed to the level of MF used in this experiment (≤ 6.79 mT and household
264
microwave), which is comparable to the level of human daily exposure. In contrast
265
to previous findings where faster growth was attributed to magnetic field, our
266
design of electromagnet allowed us to conclude that the faster growth of the sample
267
plants was due to heat from the electromagnet. To the best of our knowledge, this
268
is the first experiment where (1) effects of both direct and indirect EMF applications
269
were studied (2) the confounding effect of heat from EMF was systematically
270
investigated. Unlike MF from permanent magnet, EMF and heat are inseparable.
271
The two control groups in absence of extra EMF, “EM-0” receiving the same
272
amount of heat with other treatment groups and “No EM” at room temperature
273
allowed us to distinguish the effects of heat from MF on the growth of plants.
12
274
Though a null result is reported in this paper, the implication of our findings is that
275
elevated temperature due to an electromagnet may explain many contradictory and
276
non-repeatable reports on the effect of EMF on living organisms.
277
278
279
Acknowledgement
Generous support from the Mahidol University International College is
280
gratefully acknowledged.
We appreciate the help from Mr. Athikhun
281
Suwannakhan, Ms. Supaporn Phomsurin, Mrs. Anchalee Leelapratchayanont, and
282
Ms. Pinthusorn Eiamratchanee for moral and technical support.
283
284
References
285
Adey, W. R. (1993). Biological effects of electromagnetic fields. Journal of cellular
286
biochemistry, 51: 410-410.
287
Anand, A., Nagarajan, S., Verma, A., Joshi, D., Pathak, P., and Bhardwaj, J. (2012).
288
Pre-treatment of seeds with static magnetic field ameliorates soil water
289
stress in seedlings of maize (Zea mays L.). Indian Journal of Biochemistry
290
& Biophysics, 49: 63-70.
291
Bogatin, J., Bondarenko, N. P., Gak, E. Z., Rokhinson, E. E., and Ananyev, I. P.
292
(1999). Magnetic treatment of irrigation water: experimental results and
293
application conditions. Environmental science & technology, 33(8): 1280-
294
1285.
295
Cakmak, T., Cakmak, Z. E., Dumlupinar, R., and Tekinay, T. (2012). Analysis of
296
apoplastic and symplastic antioxidant system in shallot leaves: Impacts of
13
297
weak static electric and magnetic field. Journal of plant physiology,
298
169(11): 1066-1073.
299
Colic, M. and Morse, D. (1999). The elusive mechanism of the magnetic `memory'
300
of water. Colloids and Surfaces A: Physicochemical and Engineering
301
Aspects, 154(1): 167-174.
302
El-Yazied, A. A., El-Gizawy, A., Khalf, S., El-Satar, A., and Shalaby, O. (2012).
303
Effect of magnetic field treatments for seeds and irrigation water as well as
304
N, P and K levels on productivity of tomato plants. Journal of Applied
305
Sciences Research, 8(4): 2088-2099.
306
307
Feychting, M., Ahlbom, A., and Kheifets, L. (2005). EMF and Health. Annual
Review of Public Health, 26(1): 165-189.
308
Flórez, M., Carbonell, M. V., and Martínez, E. (2007). Exposure of maize seeds to
309
stationary magnetic fields: Effects on germination and early growth.
310
Environmental and Experimental Botany, 59(1): 68–75.
311
312
Galland, P., and Pazur, A. (2005). Magnetoreception in plants. Journal of plant
research, 118(6): 371-389.
313
Harris, S.-R., Henbest, K. B., Maeda, K., Pannell, J. R., Timmel, C. R., Hore, P.,
314
and Okamoto, H. (2009). Effect of magnetic fields on cryptochrome-
315
dependent responses in Arabidopsis thaliana. Journal of The Royal Society
316
Interface.
317
Knirsch, M. C., dos Santos, C. A., de Oliveira Soares Vicente, A. A. M., and Penna,
318
T. C. V. (2010). Ohmic heating—a review. Trends in Food Science &
319
Technology, 21(9): 436 - 441.
14
320
321
322
323
324
Limpanuparb, T. (2001). [Magnetic field and its effects in plant growths] (in Thai).
Junior Science Talent Project (JSTP). in Thai)Thailand.
Maffei, M. E. (2014). Magnetic field effects on plant growth, development, and
evolution. Frontiers in plant science, 5.
Microwaved water - see what it does to plants. (2015). Snopes.Available from
325
http://www.snopes.com/science/microwave/plants.asp.
326
October 24, 2015.
327
328
329
330
Accessed
date:
Montriwat, P. (2015). Effects of magnetic field on first stage growth of higher
plants. Mahidol University International College. Thailand
Munns, R. (2002). Comparative physiology of salt and water stress. Plant, cell &
environment, 25(2): 239-250.
331
Naz, A., Jamil, Y., Iqbal, M., Ahmad, M. R., Ashraf, M. I., and Ahmad, R. (2012).
332
Enhancement in the germination, growth and yield of okra (Abelmoschus
333
esculentus) using pre-sowing magnetic treatment of seeds. Indian Journal
334
of Biochemistry & Biophysics, 49: 211-214.
335
336
337
338
339
340
Occhipinti, A., De Santis, A., and Maffei, M. E. (2014). Magnetoreception: an
unavoidable step for plant evolution? Trends in plant science, 19(1): 1-4.
Ruzic, R. and Jerman, I. (2002). Weak magnetic field decreases heat stress in cress
seedlings. Electromagnetic Biology and Medicine, 21(1): 69-80.
Sabehat, A., Weiss, D., and Lurie, S. (1998). Heat-shock proteins and cross‐
tolerance in plants. Physiologia Plantarum, 103(3): 437-441.
341
Shine, M. B., and Guruprasad, K. N. (2012). Impact of pre-sowing magnetic field
342
exposure of seeds to stationary magnetic field on growth, reactive oxygen
15
343
species and photosynthesis of maize under field conditions. Acta
344
Physiologiae Plantarum, 34(1): 255–265.
345
Srisuthikul, N. (2001). A study of the effect of a magnetic field on the reduction of
346
the surface tension of water. Mahidol University: Faculty of Graduate
347
Studies. Thailand.
348
349
Zhadin, M. N. (2001). Review of Russian literature on biological action of DC and
low-frequency AC magnetic fields. Bioelectromagnetics, 22(1): 27-45.
350
16
351
Table 1 Copper coil properties
Electromagnet
Copper wire (turns)
Resistant at 35°C
of electromagnet
pairs (Ω)
Clockwise
Counterclockwise
Effective
(CW)
(CCW)
(CW-CCW)
Control (EM-0)
500
500
0
53.2 and 53.4
EM-332
666
334
332
53.7 and 54.0
EM-666
833
167
666
56.4 and 53.4
EM-1000
1000
0
1000
53.3 and 53.3
352
17
353
Table 2 Magnetic exposure dosage
Electromagnet
Control (No EM)
Max magnetic flux density (G)
Max magnetic flux density (G)
at 0.30 A (for indirect exposure)
at 0.25 A (for direct exposure)
0.6 (GMF)
0.6 (GMF)
Control (EM-0)
3.0
1.6
EM-332
18.2
16.3
EM-666
37.3
32.5
EM-1000
67.7
48.0
354
355
18
356
Table 3 Number of germinated seeds
Groups
Indirect exposure
Tap
Direct exposure
DI
Trial 1
Trial 2
Trial 1
Trial 2
Trial 1
Trial 2
Control (No EM)
45
44
47
47
10
18
Control (EM-0)
49
45
47
48
9
17
EM-332
49
46
46
44
10
11
EM-666
48
49
47
47
11
14
EM-1000
42
45
49
48
13
11
Microwave
48
44
45
46
-
-
Total
281
273
281
280
53
71
357
358
19
359
360
361
362
Figure 1 Electromagnetic field source for the experiments; Electrical diagram
of electromagnets (left), Experimental setup of electromagnets (right)
363
364
20
365
F-test p-value = 0.023
F-test p-value = 0.051
366
F-test p-value = 0.719
F-test p-value = 0.157
367
368
Figure 2 Mean of Thai basil height with 95% confident interval
369
21
F-test p-value=0.000
F-test p-value=0.000
370
371
Figure 3 Means of waxy corn heights with 95% confident interval
372
22
373
23