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Physiol. Mol. Biol. Plants, 14(4)–October, 2008
299Photosynthetic response of Cannabis sativa
Correspondence and Reprint requests : Suman Chandra
Photosynthetic response of Cannabis sativa L. to variations in
photosynthetic photon flux densities, temperature and CO2 conditions
Suman Chandra1, Hemant Lata1, Ikhlas A. Khan1,2 and Mahmoud A. Elsohly1,3
1National Center for Natural Product Research, School of Pharmacy, University of Mississippi, MS-38677, USA.
2Department of Pharmacognosy, University of Mississippi, MS-38677, USA.
3Department of Pharmaceutics, School of Pharmacy, University of Mississippi, University, MS 38677, USA.
ABSTRACT
Effect of different photosynthetic photon flux densities (0, 500, 1000, 1500 and 2000 μmol m-2s-1), temperatures (20, 25,
30, 35 and 40 oC) and CO2 concentrations (250, 350, 450, 550, 650 and 750 μmol mol-1) on gas and water vapour exchange
characteristics of Cannabis sativa L. were studied to determine the suitable and efficient environmental conditions for its
indoor mass cultivation for pharmaceutical uses. The rate of photosynthesis (PN) and water use efficiency (WUE) of Cannabis
sativa increased with photosynthetic photon flux densities (PPFD) at the lower temperatures (20-25 oC). At 30 oC, PN and
WUE increased only up to 1500 μmol m-2s-1 PPFD and decreased at higher light levels. The maximum rate of photosynthesis
(PN max) was observed at 30 oC and under 1500 μmol m-2s-1 PPFD. The rate of transpiration (E) responded positively to
increased PPFD and temperature up to the highest levels tested (2000 μmol m-2s-1 and 40 0C). Similar to E, leaf stomatal
conductance (gs) also increased with PPFD irrespective of temperature. However, gs increased with temperature up to 30 oC
only. Temperature above 30 oC had an adverse effect on gs in this species. Overall, high temperature and high PPFD showed
an adverse effect on PN and WUE. A continuous decrease in intercellular CO2 concentration (Ci) and therefore, in the ratio
of intercellular CO2 to ambient CO2 concentration (Ci/Ca) was observed with the increase in temperature and PPFD. However,
the decrease was less pronounced at light intensities above 1500 μmol m-2s-1. In view of these results, temperature and light
optima for photosynthesis was concluded to be at 25-30 oC and ~1500 μmol m-2s-1 respectively. Furthermore, plants were
also exposed to different concentrations of CO2 (250, 350, 450, 550, 650 and 750 μmol mol-1) under optimum PPFD and
temperature conditions to assess their photosynthetic response. Rate of photosynthesis, WUE and Ci decreased by 50 %,
53 % and 10 % respectively, and Ci/Ca, E and gs increased by 25 %, 7 % and 3 % respectively when measurements were
made at 250 μmol mol-1 as compared to ambient CO2 (350 μmol mol-1) level. Elevated CO2 concentration (750 μmol mol-
1) suppressed E and gs ~ 29% and 42% respectively, and stimulated PN, WUE and Ci by 50 %, 111 % and 115 % respectively
as compared to ambient CO2 concentration. The study reveals that this species can be efficiently cultivated in the range of
25 to 30 oC and ~1500 μmol m-2s-1 PPFD. Furthermore, higher PN, WUE and nearly constant Ci/Ca ratio under elevated CO2
concentrations in C. sativa, reflects its potential for better survival, growth and productivity in drier and CO2 rich environment.
[Physiol. Mol. Biol. Plants 2008; 14(4) : 299-306] E-mail : suman@olemiss.edu
Key words : Cannabis sativa, Photosynthesis, Transpiration, Water use efficiency
Abbreviations : PPFD - Photosynthetic photon flux density, PN - Photosynthesis, Rd – Dark respiration, PN max - Maximum
rate of photosynthesis, E - Transpiration, gs - Leaf stomatal conductance, Ci - Leaf internal CO2 concentration, Ci/Ca - Internal
to ambient CO2 concentration, WUE - Water use efficiency
Research Article
The ability of a species to acclimate and adapt to
environmental variations is directly/indirectly associated
with its ability to modulate photosynthesis and water
vapour exchange (Pearcy, 1977; Berry and Downtown,
1982; Stoutjesdijk and Barkman, 1992; Ayuko et al., 2008;
Dieleman and Meinen, 2008; Kruse et al., 2008), which
in turn affects biochemical and physiological processes
in the leaf and, consequently the physiology and
productivity of whole plant. Studies on gas exchange
characteristics may provide valuable information on
functioning of plants in variable environment.
Photosynthesis, being the primary source of carbon
and energy, plays a prominent role in the logistics of
plant growth. There is a close correlation between
Physiol. Mol. Biol. Plants, 14(4)–October, 2008
300 Chandra et al.
productivity and yield of the plants with their
photosynthetic rate, in the given environment, as more
than 90% of dry matter of live plants is derived from
photosynthetic CO2 assimilation (Zelitch, 1975).
Therefore, photosynthesis is a valuable physiological
tool to evaluate the response of plants to environmental
stresses and for the rapid selection of plants for a
particular environmental condition (Joshi and Palni, 2005;
Monclus et al., 2006) or selection of suitable
environmental conditions for a particular plant species.
Furthermore, elevated CO2 may increase
photosynthetic carbon assimilation and may accelerate
plant growth and potentially improve productivity.
Indeed, a doubling in CO2 concentration increases crop
yield by 30% or more, in experiments conducted under
close environmental conditions such as green houses
and growth chambers (Kimball, 1983a, b; 1986; Cure,
1985; Poorter, 1993; Idso and Idso, 1994). Therefore, in
the present study, C. sativa plants were exposed to a
range of CO2 concentration to understand their response
in term of their photosynthetic capacity to the range of
elevated CO2 labels.
Cannabis sativa L. is widely distributed around the
world. Originally indigenous to temperate regions of
Asia, it now grows in a variety of habitats ranging from
sea level in tropical areas to alpine foot hills of
Himalayas. Cannabis has a long history of the medicinal
use in Middle East and Asia, with references as far back
as the 6th century B.C. This species was introduced in
the Western Europe medicine in the early 19th century
A.C. to treat epilepsy, tetanus, rheumatism, migraine,
asthma, trigeminal neuralgia, fatigue, and insomnia
(Doyle and Spence, 1995; Zuardi, 2006). C. sativa
contains cannabinoids, a unique class of terpenophenolic
compounds, which accumulates mainly in glandular
trichomes of the plant (Hammond and Mahlberg, 1977).
Over 70 cannabinoids have been isolated from Cannabis
sativa, the major biologically active compound being
Δ9- tetrahydrocannabinol, commonly referred as THC
(Mechoulam and Ben-Shabat, 1999). Besides its
psychoactivity, THC possesses analgesic, anti-
inflammatory, appetite stimulant and anti-emetic
properties making this cannabinol a very promising
therapeutic drug, especially for cancer and AIDS patients
(Sirikantaramas et al., 2005). The pharmacologic and
therapeutic potency of preparations of Cannabis sativa
L. and its main active constituent Δ9-
tetrahydrocannabinol (THC) has been extensively
reviewed by researchers (Mechoulam, 1986; Formukong
et al., 1989; Grinspoon and Bakalar, 1993; Mattes et al.,
1993; 1994; Brenneisen et al., 1996).
THC has a tremendous commercial value in the
pharmaceutical market. Since C. sativa is a natural and
inexpensive source of THC (as compared to producing
it synthetically), efforts to select Cannabis varieties
with high THC content are underway. However, due to
the allogamous (cross fertilization) nature of the species,
it is very difficult to maintain the chemical profile of
selected high THC-producing genotypes under field
conditions. Since this plant is also used as an illicit
drug, its cultivation in open field must be done in
secured areas and is highly regulated in the USA and
some other parts of the world. Considering these
limitations, indoor cultivation of a selected high yielding
genotype/clone under controlled environmental
conditions is the most suitable way to maintain its
potency and efficacy while circumventing the regulatory
problems. The objective of this study was to determine
the effect of light intensity, temperature and CO2
conditions on gas and water vapour exchange
characteristics of C. sativa L. to establish suitable and
efficient environmental conditions for its indoor
cultivation.
MATERIAL AND METHODS
To study the photosynthetic response of C. sativa under
different PPFD and temperature levels, leaves of twenty
vegetatively propagated, four month old plants from a
single mother plant of high yielding Mexican variety
were exposed to a range of PPFD (0, 500, 1000, 1500 and
2000 μmol m-2s-1) and temperature conditions (20, 25, 30,
35 and 40 oC) under controlled humidity (55 ± 5 %) and
CO2 (350 ± 5 μmol mol-1) concentration to determine
suitable environmental conditions for it’s optimum
photosynthetic assimilation. Thereafter, leaves were
acclimated under optimum light and temperature
conditions and exposed to different CO2 concentrations
(250, 350, 450, 550, 650 and 750 μmol mol-1) to study the
effect of CO2 on photosynthetic and water vapour
characteristics of this species. All the measurements
were carried out on five upper undamaged, fully
expanded and healthy leaves of each plant with the
help of a closed portable photosynthesis system (Model
LI-6400; LI-COR, Lincoln, Nebraska, USA) equipped with
light, temperature, humidity and CO2 controls. Different
PPFD were provided with the help of an artificial light
source (Model LI-6400-02; light emitting silicon diode;
LI-COR), fixed on the top of the leaf chamber and were
recorded with the help of quantum sensor kept in range
of 660-675 nm, mounted at the leaf level. The rate of
dark respiration was measured by maintaining the leaf
cuvette at zero irradiance. To avoid any radiation from
Physiol. Mol. Biol. Plants, 14(4)–October, 2008
301Photosynthetic response of Cannabis sativa
outside the leaf chamber was covered with a black cloth
through the respiratory measurements. Temperature of
the cuvette was controlled by the integrated Peltier
coolers, which is controlled by the microprocessor.
Different concentrations of CO2 were supplied to the
cuvette of climatic unit (LI-6400-01, LI-COR Inc., USA)
by mixing pure CO2 with CO2 free air and were measured
by infrared gas analyzer. All the measurements for gas
and water vapour exchange were first recorded at lowest
PPFD and temperature condition and then subsequently
to the increasing levels of these parameters. Similarly,
leaves under optimum PPFD and temperature conditions
were first exposed to the lowest level of CO2
concentration followed by elevated levels. Air flow rate
(500 mmol s-1) and relative humidity (55 ± 5%) were kept
nearly constant throughout the experiment. Since steady
state photosynthesis is reached within 30–45 min, the
leaves were kept for about 45–60 min under each set of
light conditions before the observations were recorded.
Four gas exchange parameters viz., photosynthetic rate
(PN), transpirational water loss (E), stomatal conductance
for CO2 (gs) and intercellular CO2 concentration (Ci)
were measured simultaneously at steady state condition
under various permutations and combinations of light
and temperature. Water use efficiency (WUE) was
calculated as a ratio of the rate of photosynthesis and
transpiration. A correlation and multiple regression
analysis of data was performed on the basis of multiple
linear hypothesis PN, E, gs, Ci, Ci/Ca and WUE as a
dependent variable on PPFD, temperature and different
CO2 concentrations using SYSTAT-11 (Systat Software
Inc. San Jose, CA, USA) statistical software.
RESULTS AND DISCUSSION
Both photosynthetic assimilation and biomass
production are temperature- and light-dependent
processes. The potential for photosynthetic acclimation
to growth temperature is quite variable between species.
Generally, variations in PN reflect adjustment to the
respective growth environment and also to the resistance
to climate rigors. Although plants can exhibit a high
degree of plasticity with respect to temperature response
of photosynthesis, there is a general consensus that
the optimum temperature for photosynthesis for an
individual plant species reflects the environmental
temperature range for which the species is genetically
and physiologically adapted (Berry and Bjorkman, 1980).
On other hand, response of photosynthesis to PPFD
has been a long standing interest. At the leaf surface,
low PPFD might be a limiting factor and high PPFD may
be a threat to the plant metabolism if the irradiance
exceeds the demand of photosynthesis (Osmond, 1994;
Aguirre-von Wobeser et al., 2000). Therefore,
determination of the conditions for optimum gas and
water vapour exchange processes is a prerequisite for
growing any species indoor. According to our data on
C. sativa, temperature optima for PN was observed at 30
oC. In general, temperature higher than 30 oC had an
adverse effect on PN (Fig. 1A). At 25 oC, rate of
photosynthesis increased with increasing PPFD, but this
trend peaked with 1500 μmol m-2s-1 PPFD at 30 oC, and
decreased at higher light intensities. Similar effect of
Fig. 1. A. Variations in net photosynthesis in C. sativa with
varying photosynthetic photon flux densities (PPFD) and
temperature conditions. B. The temperature dependence of
Dark respiration in Cannabis sativa.
Photon Flux Density (μmolm
-2
s
-1
)
0 500 1000 1500 2000
Net Photosynthesis
μ
( m
(ol m
-2
s
-1
)
0
5
10
15
20
25
20
25
30
35
40
A
Temperature (
o
C)
20 25 30 35 40
Dark Respiration
μmol m
-
2
s
-
1
)
0
1
2
3B
Physiol. Mol. Biol. Plants, 14(4)–October, 2008
302 Chandra et al.
PPFD was observed at temperatures higher than 30 oC.
Maximum rate of photosynthesis (PN max) was 24.60 μmol
m-2s-1 at 30 oC and under 1500 μmol m-2s-1 PPFD. The
interaction of PPFD and temperature demonstrates that
high PPFD and higher temperature together (PPFD ×
temperature) had an adverse effect on PN. In general,
effect of PPFD (r = 87) was more prominent in regulating
PN in Cannabis sativa as compared to temperature (r =
46).
An increase in Rd (μmol m-2s-1 PPFD) was observed
with increasing temperature up to 30 oC and decreased
at higher temperature (Fig. 1B). Working on two different
populations of Podophyllum hexandrum, Singh and
Purohit (1997) reported a linear increase in Rd with
temperature (up to 40 oC) in alpine population whereas;
in temperate population, Rd increased with temperature
up to 30 oC and decreased at higher levels. 2 to 10 fold
increase in Rd was reported by Joshi and Palni (1998)
in different tea leaves with increase in temperature from
20 to 40 oC; higher temperature however, was associated
with clones having higher photosynthetic rates. In C.
sativa, decrease in Rd followed a trend similar to PN,
with varying temperatures. Reduced PN, and increased
Rd are reported to limit the productivity in some plant
species at higher temperatures (Alexander et al., 1995;
Thornton et al., 1995).
Stomatal conductance was commensurate to PPFD
levels, irrespective of temperature (Fig. 2). A positive
correlation (r = 56) was observed between PPFD and gs
in C. sativa. On other hand, gs increased with increasing
temperature up to a maximum value at 30 oC and
decreased at higher temperatures under all the PPFD
labels. Maximum value of gs was recorded at 30 oC and
highest level of PPFD (2000 μmol m-2s-1).
In contrast to gs, E increased in response to both
higher temperature and high PPFD. Lowest value of E
(2.38 ± 0.28 mmol m-2s-1) was observed at 20 oC under
0 μmol m-2s-1 PPFD, whereas highest value (7.60 ± 0.33
mmol m-2s-1) was recorded at 40 oC under 2000 μmol
m-2 s-1 (Fig. 3). Transpiration rate is known to depend
on gs (Alexander et al., 1995), and it seems to be major
factor driving E in the present study. An increase in E
and decrease in gs is reported in many plant studies
(Rawson et al., 1977; Schulze et al., 1972).
Intercellular CO2 concentration (Ci) decreased with
increase in PPFD and temperatures up to highest level
tested (PPFD up to 2000 μmol m-2s-1 and temperature up
to 40 oC (Fig. 4). Highest Ci (367 ml L-1) was observed
at lowest PPFD and temperature conditions i.e. 20 oC
and 0 μmol m-2s-1 PPFD and, thereafter lowest Ci (149 ml
L-1) was recorded at highest PPFD and temperature
conditions. However, the decrease was less pronounced
at light intensities above 1500 μmol m-2s-1. Effect of
temperature on depression of Ci was more prominent
above 30 oC. Higher temperature and higher light
together had a significant adverse effect on Ci of this
species. Photosynthetic data particularly on Ci and gs,
Fig. 2. Variations in stomatal conductance in C. sativa with
varying photosynthetic photon flux densities (PPFD) and
temperature conditions.
Fig. 3. Variations in rate of transpiration in C. sativa with
varying photosynthetic photon flux densities (PPFD) and
temperature conditions.
Photon Flux Density (
(
μmol m
mmol m
-2
-2
s
s
-1
-1
)
)
0 500 1000 1500 2000
Stomatal Conductance
0
50
100
150
200
250
300
20
25
30
35
40
Photon Flux Density (μmol m
-2
s
-1
)
0 500 1000 1500 2000
(mm ol m
-2
s
-1
)
Rate of Transpiration
0
2
4
6
8
20
25
30
35
40
Physiol. Mol. Biol. Plants, 14(4)–October, 2008
303Photosynthetic response of Cannabis sativa
indicates that both stomatal and mesophyll factors seems
to be involved in the mechanism of control of
photosynthesis by temperature and light in C. sativa.
Similar to Ci, a gradual decrease in Ci/Ca ratio was
also observed with increasing PPFD and temperature
conditions (Table 1). About 32 %, 41 %, 44 %, 50 % and
57 % decrease in Ci/Ca ratio was observed at 20, 25, 30,
35 and 40 oC respectively when plants were exposed
from 0 to 2000 μmol m-2s-1 PPFD. Similarly, about 3 %,
17 %, 29 %, 37 % and 39 % depression was observed
under 0, 500, 1000, 1500 and 2000 μmol m-2s-1 PPFD
when plants were exposed to 40 oC as compared to 25
oC. Although essentially a biochemical process,
photosynthesis is often regarded as a diffusive process.
The rate of diffusion of CO2 is largely controlled by two
factors, gs and CO2 concentration gradient between
carboxylation site and ambient air (Ca). This CO2
concentration gradient at given gs and Ca is established
predominantly by Ci, which is a result of mesophyll
efficiency. Therefore, the diffusive entry of CO2 into
leaf is a reflection of intrinsic mesophyll capacity.
Sheshshayee et al. (1996) have reported Ci/gs ratio as
an indicator of mesophyll efficiency and a representation
of mesophyll control on PN. Our data also represent
highest mesophyll efficiency (i.e. lowest Ci/gs ratio)
around 30 oC and 1500 μmol m-2s-1 PPFD. Values of Ci/
gs ratio increased with temperature higher than 30 oC,
which further confirms that a combination of 30 oC
temperature and 1500 μmol m-2s-1 PPFD may be best
suitable for the indoor cultivation of C. sativa.
Fig. 4. Variations in intercellular CO2 concentration in C.
sativa with varying photosynthetic photon flux densities
(PPFD) and temperature conditions.
Fig. 5. Variations in water use efficiency in C. sativa with
varying photosynthetic photon flux densities (PPFD) and
temperature conditions.
Table 1. Effect of different photosynthetic photon flux density and temperature conditions on Ci/Ca ratio in the
leaves of Cannabis sativa.
Light Intensities Temperature (0C)
(μmol m-2s-1)
20 25 30 35 40
000 1.04 ± 0.12 1.04 ± 0.14 1.02 ± 0.11 1.01 ± 0.09 1.01 ± 0.07
500 0.82 ± 0.05 0.79 ± 0.06 0.74 ± 0.06 0.71 ± 0.06 0.68 ± 0.05
1000 0.80 ± 0.06 0.75 ± 0.04 0.66 ± 0.06 0.59 ± 0.04 0.57 ± 0.06
1500 0.71 ± 0.04 0.62 ± 0.06 0.58 ± 0.05 0.51 ± 0.05 0.45 ± 0.04
2000 0.70 ± 0.06 0.61 ± 0.05 0.57 ± 0.05 0.50 ± 0.04 0.43 ± 0.03
Photon Flux Density (μ
mol m
-2
s
-1
)
0 500 1000 1500 2000
Intercellular CO
2
Concentration
μlL
-1
)
0
100
200
300
400
20
25
30
35
40
(
Photon Flux Density (μ
mol m-2
s
-1
)
0 500 1000 1500 2000
Water Use Efficiencyx 100
0
2
4
6
20
25
30
35
40
Physiol. Mol. Biol. Plants, 14(4)–October, 2008
304 Chandra et al.
At 20 and 25 oC, WUE increased with increase in
PPFD up to 2000 μmol m-2s-1 (Fig. 5). On the other
hand, WUE increased only up to 1500 μmol m-2s-1 PPFD
at 30 oC and decreased thereafter at higher light levels.
Temperature higher than 30 oC had an adverse effect on
WUE of this species. The maximum WUE was observed
at 30 oC and under 1500 μmol m-2s-1 PPFD.
Photosynthesis appears to have a greater influence than
E over regulating water use efficiency in C. sativa. A
highly significant positive correlation was observed
between WUE and PN (r = 0.92). Together, high
temperature and high PPFD had an adverse effect on
the WUE in C. sativa.
Increasing atmospheric CO2 is a global environmental
concern. Atmospheric CO2 has risen from pre- industrial
value of ~ 280 μmol mol-1 to present concentration of ~
372 μmol mol-1 and is expected to exceed 700 μmol mol-
1 by the end of century (Prentice et al., 2001; Long et
al., 2004). Since ambient CO2 concentration as a
substrate is still a limiting factor for photosynthesis in
C3 plants, attempts are being made to study how changes
in atmospheric CO2 concentration will affect crops
(Bowes, 1993; Drake et al., 1997; Long et al., 2004).
This study on Cannabis sativa shows that PN, WUE
and Ci decreased by 50 %, 53 % and 10 % respectively,
and Ci/Ca, E and gs increased by 25 %, 7 % and 3 %,
respectively, when measurements were made at 250 μmol
mol-1 as compared to ambient CO2 (~350 μmol mol-1)
level (Table 2). An average of 30 to 33 % increase in PN
and productivity of C3 plants with doubling atmospheric
CO2 concentration has been already reported by Kimball
1983a, b; 1986; Idso and Idso 1994; Bazzaz and Gabutt,
1988; Cure and Acock, 1986. In C. sativa, a doubling of
CO2 concentration (750 μmol mol-1) suppressed E and gs
~29 % and 42 % respectively, and stimulated PN, WUE
and Ci by 50%, 111 % and 115 % respectively as
compared to ambient CO2 concentration. Doubling CO2
level had a significant effect on all these parameters.
Suppression in gs and consequently in E (Emaus et al.,
1993; Thomas et al., 1994) and improvement in PN and
WUE and Ci (Kimball 1983a, b; 1986; Idso and Idso
1994, Morison, 1993) under elevated CO2 concentration
is reported in many other plant species. Higher WUE
under elevated CO2, primarily because of decreased gs
and E, may enable this species to survive under drought
conditions. This species maintained nearly constant
values of Ci/Ca with increasing CO2 concentration
despite the increase in PN and WUE, and decrease in gs
and E, represents a close coordination between stomatal
and mesophyll functions (Morison, 1993) and reported
to improve growth and productivity of plant (Jones,
1992).
In view of our results, it is concluded that C. sativa
can utilize a fairly high level of PPFD and temperature
for its gas and water exchange processes, and can
perform much better if grown at ~ 1500 μmol m-2 s-1
PPFD and around 25 to 30 oC temperature conditions.
Furthermore, higher PN, WUE and nearly constant Ci/Ca
ratio under elevated CO2 concentration, reflects its
potential for improved growth and productivity in drier
and CO2 rich environment.
ACKNOWLEDGMENTS
This research was supported by National Institute of
Drug Abuse (NIDA), USA, Contract # NO1DA-0-7707.
Table 2. Effect of different levels of CO2 on net photosynthesis (PN), transpiration (E), stomatal conductance (gs),
internal CO2 concentration (Ci), Ratio of internal to external CO2 concentration (Ci/Ca) and water use
efficiency (WUE) on the leaves of Cannabis sativa.
CO2 levels PNEg
sCi Ci/Ca WUE ×
(μmol mol-1)(μmol CO2(mmol H2O (mmol CO2(μl L-1) ratio 100
m-2s-1)m
-2s-1)m
-2s-1)
250 12.48 ± 1.76 5.69 ± 0.47 202.76 ± 19.78 138.00 ± 11.42 0.55 2.19
350 24.64 ± 2.24 5.31 ± 0.35 195.99 ± 18.40 202.00 ± 14.00 0.47 4.64
450 24.76 ± 1.89 5.76 ± 0.44 189.78 ± 16.97 260.00 ± 19.34 0.58 4.30
550 26.54 ± 2.12 4.87 ± 0.38 148.37 ± 13.99 330.00 ± 22.47 0.60 5.46
650 30.48 ± 2.76 4.65 ± 0.76 136.08 ± 12.36 385.00 ± 33.24 0.61 6.56
750 36.80 ± 3.18 3.75 ± 0.33 112.76 ± 10.32 435.00 ± 37.23 0.58 9.81
Physiol. Mol. Biol. Plants, 14(4)–October, 2008
305Photosynthetic response of Cannabis sativa
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