Archontoulis, S.V.

Danalatos, N.G.

Struik, P.C.

NARCIS 

Leaf photosynthesis of kenaf (cv. Everglades 41) as affected by different light intensity and temperature regimes

Wageningen Yield 

LEAF PHOTOSYNTHESIS OF KENAF (CV. EVERGLADES 41) AS AFFECTED BY DIFFERENT  
LIGHT INTENSITY AND TEMPERATURE REGIMES  
 
S.V. Archontoulis1, 2 *, P.C. Struik1 and N.G. Danalatos2
1 Wageningen University, Dept. of Plant Sciences, Crop and Weed Ecology Group, Haarweg 333, 6709 RZ Wageningen,  
The Netherlands. E-mail: sotirios.archontoulis@wur.nl
2 University of Thessaly, Dept. of Crop Production and Agricultural Environment, Fytoco, 38446 Volos, Greece. 
 
ABSTRACT: Plant production is driven by photosynthesis. Kenaf (Hibiscus cannabinus L., Malvaceae) is a highly 
productive, warm-season annual crop, with a C3 – photosynthetic pathway. In the present work, the effect of different 
light intensity and temperature regimes on leaf photosynthesis (CO2 assimilation) and transpiration rate were 
investigated. The gas exchange measurements took place in an open field kenaf crop in central Greece, on three days 
(July 11th, August 11th and September 8th) during the summer of 2004, using an LC-pro portable leaf chamber. The 
results demonstrated that maximum net assimilation rates of about 50 kg CO2 ha-1 h-1 could be reached (at 1675 µmol 
PAR m-2 s-1), particularly at early stages of development. These data may explain the high biomass production of 
kenaf under Greek (and more generally Mediterranean) conditions, observed in recent studies. Moreover, the 
optimum temperature for maximum assimilation increased with an increase in light intensity. Transpiration rates 
increased exponentially with an increase in leaf temperature at all light levels. At temperatures above 35 oC, a single 
leaf may transpire the equivalent of 30 mm per day at full canopy.  
 
Keywords: kenaf, CO2 balance, photosynthesis, transpiration  
 
1 INTRODUCTION  
 
Kenaf (Hibiscus cannabinus L., Malvaceae) is a 
warm-season annual crop, with a C3 – photosynthetic 
pathway, achieving high biomass yields in Greece [1, 2].  
Although kenaf is a C3 crop and uses CO2, solar 
radiation, water and nitrogen less efficiently than C4
crops, recent studies from Greece and Italy showed 
assimilation rates in excess of 50-58 kg CO2 ha-1 h-1 (32-
37 µmol CO2 m-2 s-1) [2, 3].  
The global environment is changing rapidly; 
especially CO2 concentration and air temperature are 
increasing. The earth’s atmospheric CO2 concentration 
has increased from 280 ppm since the start of the 
industrial revolution, to a current level of around 370 
ppm, and continues to rise at approximately 1.8 ppm per 
year [4]. Due to the increase of the CO2 level, it is 
expected that the maximum, minimum and mean global 
temperatures will also increase by 3–4 oC [4]. These key 
factors affect plant growth, development and function, 
starting with photosynthesis, the most important process 
in the plant kingdom, sustaining all life forms on earth.  
Temperature affects the photosynthetic rate due to its 
pervasive role in the regulation of the plant’s biochemical 
reaction rates, the plant’s morphogenesis, and the 
exchange of CO2 and energy between the plant and the 
atmosphere. Plants show an optimum range of 
temperature for photosynthesis, and beyond this range 
carbon assimilation decreases [5]. It has been shown for 
kenaf (cv. Tainnung 2) that this happens when leaf 
temperature increases from 26 to 40 oC [3].  
The level of irradiance is an important ecological 
factor which determines the assimilation rate. Under high 
(photoinhibition) or low light intensities, the diffusion 
rate of CO2 from the air to the stomata is the major factor 
limiting CO2 assimilation. Under saturated light 
conditions (2000-2300 µmol m-2 s-1) and abundant water 
supply, maximum kenaf (cv. Tainnung 2) assimilation 
rate ranged from 47 to 59 kg CO2 ha-1 h-1 (29.9 to 37.7 
µmol CO2 m-2 s-1) [3].  
Despite its great potential for multiple uses (paper, 
construction materials, energy), only few articles report 
experimental field data on the physiology of kenaf. 
Especially data on assimilation rate as affected by 
environmental and agronomic factors are scarce. 
Knowledge on kenaf’s carbon balance, as a response of 
assimilation and respiration rate to environmental 
conditions, is fundamental for understanding and 
assessing crop growth and productivity. 
The objective of the present work is to determine the 
effect of different light intensities (in the range of 0 to 
2000 µmol PAR m-2 s-1) and temperatures (in the range of 
10 to 40 oC) on leaf photosynthesis and transpiration of 
the kenaf variety Everglades 41.   
 
2 MATERIALS AND METHODS 
 
2.1 Experimental area – experimental set-up  
All gas exchange measurements took place at the 
University of Thessaly experimental site in Palamas, 
Karditsa, located in Western Thessaly, central Greece 
(coordinates: 39o25’43.4’’ N, 22o05’09.7’’ E, altitude 
107 m) during the summer of 2004. The soil was a deep 
loamy fertile soil, classified as Aquic Xerofluvent [6]. 
The measurements were conducted in a kenaf field 
experiment (treatments: 2 sowing dates × 2 varieties × 2 
plant densities in a completely randomized block design 
with 3 replicates), and particularly in the treatments 
“S1V2D1” and “S2V2D1”; where S1 is sowing date 1/6/04, 
S2 is sowing date 1/7/04, V2 is cultivar Everglades 41, 
and D1 is plant density 20 plants m-2. All plots received a 
basal dressing of 50 kg P ha-1 and 100 kg K ha-1 before 
sowing, while a top dressing of 100 kg N ha-1 (as 
ammonium sulphate) was applied when the plants 
reached a height of 0.4 m. Weather data (radiation, air 
temperature, rainfall, air humidity, wind speed and class-
A pan evaporation rate (PET) was recorded hourly on an 
automatic meteorological station which had been 
installed a few meters from the experimental site. 
 
2.2  Gas exchange measurements 
Net photosynthetic rate (A), transpiration rate (E), 
stomatal conductance (Gs), intercellular CO2
concentration (Ci), leaf temperature (Tl), chamber 
temperature (Tch), atmospheric CO2 concentration (Cref) 
and incident irradiance at leaf surface (Qleaf) were 
instantaneously measured using the LC-pro, Leaf 
Chamber Analysis System (Li-Cor, Lincoln, England). 
All parameters were automatically recorded every 5 
minutes over a 5-hour period. Temperature and incident 
irradiance in the leaf chamber were adjusted each time 
(records under artificial conditions set by analysis 
system). Measurements were done from 12:00 to 20:00 h 
for three different days (treatment “S1V2D1” on July and 
August 11th and “S2V2D1” on September 8th). The crop 
received drip irrigation at frequent intervals, to fully 
match the PET. Irrigation was applied on the dates 9/7, 
4/8, and 30/8 with approximately 50 mm per irrigation.  
 
3 RESULTS AND DISCUSSIONS 
 
3.1 Weather conditions 
The study area is characterized by a typical 
Mediterranean climate with hot, dry summers and cool 
humid winters. Figure 1 illustrates the diel trend of 
weather parameters in the study area during the 
observation days.  Wind speed was in the range of 0.6-
1.0 m s-1 during the observation period. Maximum air 
temperatures during gas exchange measurements were 
moderate on September 8th but very high on July 11th.
Irradiance levels were very high on the first two 
observation dates, but significantly lower on the 
observation date in September. The relative humidity 
fluctuated at low levels around 40-50% during the 
observation period. In combination with the high 
temperatures, especially on July 11th, one might expect 
high transpiration needs. The daily evaporation on July 
11th, August 11th, and on September 8th was 6.56, 6.39, 
and 6.32 mm, respectively (i.e. average water losses of 
about 64 t ha-1). The irradiation measured in the Thessaly 
lowlands during the summer months reached values close 
to the maximum for earth surface level.   
 
3.2 Crop characteristics 
Specific Leaf Area (SLA, green leaf area over leaf 
weight), Leaf Area Index (LAI, leaf area over surface 
area) are of great importance in understanding the 
processes of plant growth and photosynthesis.  
 
Table I: Crop growth data of kenaf (cv. Everglades 41) 
on the dates at which gas exchange measurements took 
place (each value is an average of three replicates).  
Day 11/7/04 11/8/04 8/9/04 
Treatment S1V2D1 S1V2D1 S2V2D1
Plant height (cm) 48 165 160 
Number of main 
nodes per plant 11.5 33.3 37.8 
Dry weight (t ha-1) 0.74 5.01 4.02 
SLA (m2 kg-1) 24.09 17.15 18.53 
LAI (m2 m-2) 1.02 2.07 2.62 
SLA and LAI influence the leaf area ratio and thus 
the relative growth rate of the crop. The higher SLA and 
LAI, the higher the growth rate (more light intercepted, 
higher net assimilation rate) and thus the higher the 
biomass production. Table I summarizes some crop 
growth data measured during the days on which gas 
exchange was measured.  [2].  
 
Figure 1: Diel trends in weather data (wind speed in m s-
1, air temperature in oC, incident irradiance in W m-2 and 
relative humidity in %) in the study area in 2004 for three 
days (July 11th, August 11th, and September 8th). All gas 
exchange measurements were conducted between 12:00 
and 20:00 h.  
 
3.3 Temperature response curve 
Figure 2 illustrates the net assimilation rate (in kg 
CO2 ha-1 h-1) of kenaf as a function of leaf temperature at 
various levels of light intensity (in µmol m-2 s-1) for three 
different days. The equipment was programmed to 
provide a temperature range of 5-45oC, but due to the 
extremely high temperatures prevailing during the first 
two observation days (Fig. 1) and the fact that 
temperature adjustment in this LC-pro is limited to ± 10 
oC, the actual range was smaller, especially during the 
first observation day.   
The data on the temperature response are plotted in 
Fig. 2. At each level of PAR, a polynomial curve can be 
fitted through the temperature response of the 
photosynthesis, at least for the later two observation 
dates. Two types of interaction between temperature and 
PAR can be observed: i. The optimum temperature for 
photosynthesis increases with an increase in the level of 
radiation; and ii. Beyond the optimum, the temperature 
response is stronger at a higher radiation level than at a 
lower PAR level. These experimental results are 
consistent with predictions of temperature responses from 
the crop growth simulation model GECROS [7].   
 
Fig. 2: Temperature response curves of kenaf (cv. 
Everglades 41) at five light intensities (PAR) and for 
three observation days in central Greece in 2004. (Net 
assimilation rate of flag leaf in kg CO2 ha-1 h-1).   
The maximum net photosynthetic rate (> 50 kg CO2
ha-1 h-1) was recorded on July 11th at a light intensity of 
1675 µmol m-2 s-1 and a leaf temperature of 25 oC. The 
total dry weight of the plant at that date was lower than 
on the later two days (Table I), resulting in lower 
(maintenance) respiration needs and more assimilates 
available for growth. The maximum assimilation rate 
decreased over time (for other two dates with similar 
development stages: 42 kg CO2 ha-1 h-1; 1675 µmol m-2 s-
1; Fig. 2) and was found for higher leaf temperatures (25-
29 oC). The increase in optimum temperature for 
photosynthesis may be attributed to the adaptation of the 
leaves to high temperatures.  
In conclusion, the optimum temperature for kenaf 
(cv. Everglades 41) assimilation is between 25 and 29 oC
and depends on the development stage. Below and 
beyond this optimum the photosynthetic rate is lower. In 
the sub-optimum part, the photosynthetic machinery is 
limited by the enzymatic reaction rates (kinetic properties 
of Rubisco are temperature-dependent). In the supra-
optimum part, the oxygenation reaction of Rubisco 
increases more than the carboxylation, so that 
photorespiration becomes more important. [8].    
 
3.4 Light response curve 
 
Fig. 3: Light response curves of kenaf cv. Everglades 41 
at two temperature ranges and on three observation dates 
in central Greece in 2004. Data are net assimilation rates 
of flag leaf in kg CO2 ha-1 h-1. (T: temperature range 20-
30 oC; U: temperature range 30-40 oC). 
Radiation drives photosynthesis. Plotting the net 
assimilation rate versus the incident irradiance, light 
response curves were constructed (Fig. 3). For simplicity, 
only two ranges were distinguished (above and below 30 
oC). The plotted data show that at low irradiance (until 
600 µmol m-2 s-1) the rate of CO2 assimilation increases 
linearly and is light-limited. At high irradiance, 
photosynthesis becomes light-saturated and is limited by 
the carboxylation rate, which is governed by some 
combination of CO2 diffusion into the leaf and 
carboxylation capacity [8].  
On all observation dates, the temperature range 20-30 
oC provides higher rates of net assimilation than the 
range 30-40oC, due to low photorespiration in the former 
temperature range. Based on Fig. 3 it can be stated that 
on the dates August 11th and September 8th, CO2 fixation 
was stabilized at light intensities greater than 1500 µmol 
m-2 s-1, in contrast to the first observation day when the 
rate seems to increase even beyond that light level.  
 
3.5 Transpiration rate 
 Most of the water taking part in the transpiration 
process is used for cooling purposes, i.e. to maintain a 
certain temperature equilibrium in the plant. Plotting 
transpiration rates measured on August 11th against the 
leaf temperature (Fig. 4), provides an exponential 
relationship, independent of radiation, which can be well 
described by the formula: 
 
Y=0.1246e0.1457*temp (R2=94%, Fig. 4).  
 
At air temperatures above 35oC, a single leaf transpired 
the equivalent of 30 mm per day of a full canopy.   
 
Fig. 4: Leaf transpiration rate of kenaf (cv. Everglades 
41), as a function of leaf temperature at different light 
intensities on August 11th, 2004 in central Greece. 
Different markers represent different levels of irradiance.  
 
4 CONCLUSIONS 
 
It can be concluded that kenaf (cv. Everglades 41) is 
characterized by a high photosynthetic capacity. 
Maximum rates of about 50 kg CO2 ha-1 h-1 were 
achieved at early crop development stages, when the 
maintenance respiration was still at a low level. The 
optimum temperature for maximum assimilation 
increased with an increase in light intensity; the optimum 
temperature for kenaf was in the range of 25-29 oC.  
Transpiration rates increased exponentially with 
increasing leaf temperature at all light levels. At 
temperatures above 35 oC, transpiration may reach 30 
mm/day. The above data may explain the particularly 
high biomass production of kenaf under Greek, and more 
generally under Mediterranean conditions, found in 
recent studies, and can be used in crop-growth simulation 
models to predict kenaf growth and biomass yield.    
 
5 ACKNOWLEDGEMENTS 
 
This work was partially financed by the E.U. Project 
QLK5-CT-2002-01729 “Biomass Production Chain and 
Growth Simulation Model for Kenaf”. 
 
6 REFERENCES  
 
[1] Danalatos, N.G., and Archontoulis, S.V., 2004. 
Potential growth and biomass productivity of kenaf 
under central Greek conditions: II. The influence 
of variety, sowing time and plant density. 
Proceedings of the 2nd World Biomass Conference, 
10-14 May, Roma, Italy, pp. 319-322. 
[2] Danalatos, N.G., and Archontoulis, S.V., 2005. 
Sowing time and plant density effects on growth 
and biomass productivity of two kenaf varieties in 
central Greece. Proceedings of the International 
Conference on Industrial Crops and Rural 
Development, 17-21 September 2005, Murcia, 
Spain, pp. 889-901. 
[3] Cosentino, S.L., Riggi, E., and D’Agosta, G., 2004. 
Leaf photosynthesis in kenaf (Hibiscus cannabinus 
L.)  in response to water stress. Proceedings of the 
2nd World Biomass Conference, 10-14 May, Roma, 
Italy, pp. 374-376. 
[4] Heinemann, A.B., Maia, Aline de H.N., Neto, D.D., 
Ingram, K.T., and Hoogenboom, G., 2005. Soybean 
(Glycine max (L.) Merr.) growth and development 
response to CO2 enrichment under different 
temperature regimes. European Journal of 
Agronomy (in press).  
[5] Allen, D.J., and Ort, D.R., 2001. Impacts of chilling 
temperatures on photosynthesis in warm-climate 
plants. Trends in Plant Science 6, 36–42. 
[6] USDA, 1975. Soil Taxonomy. A basic system of soil 
classification for making and interpreting soil 
surveys. Agric. Handbook 466. Washington DC, 754 
pp. 
[7] Yin, X., and van Laar, H.H., 2005. Crop Systems 
Dynamics.  An ecophysiological simulation model 
for genotype-by-environment interactions. 
Wageningen Academic Publishers, Wageningen, 
The Netherlands, 153 pp. 
[8] Atwell, B., Kriedemann, P., and Turnbull, C., 1999. 
Plants in action. Adaptation in nature performance. 
Macmillan publishers Australia PTY LTD.  
 


Leaf photosynthesis of kenaf (cv. Everglades 41) as affected by different light intensity and temperature regimes

Abstract

Similar works

Full text

Available Versions

NARCIS

Wageningen Yield