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Light is not evenly distributed in Dutch glass greenhouses, but this can be improved with diffuse light. Modern greenhouse coverings are able to transform most of the light entering the greenhouse into diffuse light. Wageningen UR Greenhouse Horticulture has studied the effect of diffuse light on crops for several years. Modelling and experimental studies showed that crops such as fruit vegetables with a high plant canopy as well as ornamentals with a small plant canopy can utilize diffuse light better than direct light. Diffuse light penetrates the middle layers of a high-grown crop and results in a better horizontal light distribution in the greenhouse. Diffuse light is absorbed to a better degree by the middle leaf layers of cucumber, resulting in a higher photosynthesis. The actual photosynthesis of four pot plant species was found to be increased and crop temperatures were lower during high irradiation. The yield of cucumbers was increased, and the growth rate of several potted plants was increased. These investigations have resulted in a quantitative foundation for the potentials of diffuse light in Dutch horticultural greenhouses and the selection and verification of technological methods to convert direct sunlight into diffuse light.
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The Effect of Diffuse Light on Crops
S. Hemming, T. Dueck, J. Janse and F. van Noort
Wageningen University and Research Centre (Wageningen UR), P.O. Box 16
Bornsesteeg 65, 6700 AA Wageningen
The Netherlands
Keywords: covering material, photosynthesis, light distribution, cucumber, Ficus,
Schefflera, chrysanthemum, kalanchoe
Abstract
Light is not evenly distributed in Dutch glass greenhouses, but this can be
improved with diffuse light. Modern greenhouse coverings are able to transform
most of the light entering the greenhouse into diffuse light. Wageningen UR
Greenhouse Horticulture has studied the effect of diffuse light on crops for several
years. Modelling and experimental studies showed that crops such as fruit
vegetables with a high plant canopy as well as ornamentals with a small plant
canopy can utilize diffuse light better than direct light. Diffuse light penetrates the
middle layers of a high-grown crop and results in a better horizontal light
distribution in the greenhouse. Diffuse light is absorbed to a better degree by the
middle leaf layers of cucumber, resulting in a higher photosynthesis. The actual
photosynthesis of four pot plant species was found to be increased and crop
temperatures were lower during high irradiation. The yield of cucumbers was
increased, and the growth rate of several potted plants was increased. These
investigations have resulted in a quantitative foundation for the potentials of diffuse
light in Dutch horticultural greenhouses and the selection and verification of
technological methods to convert direct sunlight into diffuse light.
INTRODUCTION
Light is not evenly distributed in Dutch glass greenhouses. Fruit vegetables like
cucumber have a high leaf area index and intercept a large quantity of light with the upper
leaves, while the middle and lower leaves receive much less light and contribute very
little to photosynthesis, growth and in the end, production. The crop would benefit if
upper leaves would intercept less incident light and the middle and lower leaves a greater
proportion, in order to realize a more uniform light interception over the foliage. Hovi et
al. (2004) showed that a higher amount of artificial light within a crop achieved by inter-
lighting significantly increased photosynthesis of the lower leaves of cucumber. The same
effect can be realized by diffuse light. From earlier investigations in forests (Farquhar and
Roderick, 2003; Gu et al., 2003), apple trees (Lakso and Mussleman, 1976) and grass
canopies (Sheehy and Chapas, 1976) it is known that diffuse light is able to penetrate
deeper into a plant canopy in comparison to direct light and that photosynthesis in forests
is increased by diffuse light. There are also indications that plants have developed
mechanisms to use diffuse light more efficiently (DeLucia et al., 1996; Vogelmann,
1996). In young plants and small plants like pot plants the horizontal light distribution is
not optimal. Shadows cast from the greenhouse construction have a negative influence on
the plant production. In order to realize a uniform production, the light distribution has to
be uniform over the whole canopy. This can be achieved by diffuse light. Light can be
made diffuse by modern covering materials (Hemming et al., 2004). Such materials
contain pigments, macro- or microstructures, which are able to transform all incoming
direct light into diffuse light. Depending on the design of the structure the incoming light
scatters, the angle of incidence is changed. Efficient structures make the light diffuse
without a significant reduction in light transmission.
During the past four years Wageningen UR has investigated the potential of
diffuse covering materials used in Dutch greenhouses (Hemming et al., 2004). The
suitability of several greenhouse covering materials and their optical properties (PAR
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Proc. IS on Greensys2007
Eds.:S. De Pascale et al.
Acta Hort. 801, ISHS 2008
transmission τdirect and τdiffuse, haze) was investigated in laboratories as well as in practice.
On the basis of light and crop models (Goudriaan, 1988; Marcelis et al., 2000) the effect
of diffuse light on crop photosynthesis was studied (Hemming, 2006). In this paper the
effect of diffuse covering materials on light distribution, plant photosynthesis, plant
growth and development will be elaborated. The results are based on crop experiments
with cucumbers and four different types of potted plants.
MATERIALS AND METHODS
In four greenhouse compartments, each 150 m2, experiments were conducted first
with cucumbers and later with four pot plant species. In two compartments the crops
received mainly diffuse light, in the other two compartments they received natural light.
To change the light conditions inside the greenhouse, roof and side-walls of the glass
greenhouses were covered with either a diffuse plastic film “F-Clean diffuse” or with a
clear plastic film “F-Clean”, both 100 μm from Asahi Glass Europe bv. The optical
properties of both materials are described in Figure 1. The diffuse material had a haze of
50%. Cucumbers ‘Shakira’ were planted on April, 18th 2006. They were grown in 18
rows with 3.5 plants per m2. Rockwool was used as substrate with an average pH of 5.3
and an average EC of 3. On May, 9th, the crop reached the wire, the top was removed, and
two shoots remained. The first flower appeared in the sixth bud after 10 days, and the first
flower in the sixteenth bud appeared after 16 days. First harvest took place on May, 9th
and crop ended on July, 26th 2006. Cuttings of pot chrysanthemum ’Danielson’ and
kalanchoe ‘Kerinci’ and young plants of Ficus benajmina ‘Exotica’ and Schefflera
‘Compacta’ were potted on August, 30th 2006 in a 13 cm pot filled with substrate flush
fine from TrefEgo. Plants were grown in natural short day. Schefflera and Ficus were
fertilized with N-P-K 9-2-4, an EC of 1.7 and a pH of 5.6, chrysanthemum and kalanchoe
were fertilized with NPK 4-2-4, an EC of 2.0 and a pH of 5.6. Plants were grown with 50
plants per m2 and 20 plants per m2 at the end of the growing period. Chrysanthemum tops
were removed after 14 days.
In all compartments greenhouse climate was regulated and monitored: dry and wet
bulb temperature [oC], relative humidity [%], CO2-concentration [ppm], ventilation
opening [%], global radiation [W m-2], PAR [μmol m-2 s
-1]. Crop temperature was
monitored with four IR-camera’s of Growlab Hogendoorn bv, The Netherlands. PAR Lite
sensors and pyranometers CM10 from Kipp & Zonen bv, The Netherlands, were installed
above the crop for permanent measurements. Additionally, light distribution within the
crop, with different heights, on diffuse and clear days, in young and full-grown crops was
measured vertically and horizontally with a Sunscan system from Delta-T Ltd., U.K.
The photosynthetic capacity was measured with an advanced mobile
photosynthesis system (LCpro+, ADC Bioscientific Ltd., U.K.) with a leave chamber of
6.25 cm2. Measurements were carried out in different crop layers of cucumber at two light
levels (465 µmol m-2 s
-1 and 1250 µmol m-2 s
-1) on fully-grown leaves at a CO2-
concentration of 700 ppm, a temperature of 21°C and a relative humidity of 85%.
Moreover full light response curves were measured for the four pot plants. The amount of
chlorophyll was estimated with a SPAD 50 meter from Minolta. For cucumber the
amount of protein content [µg g-1] and the RuBisCo-content [µg g-1] was determined.
Destructive measurements were carried out to examine possible changes in crop
morphology of cucumber every second week. Cucumbers were analyzed in four different
leaf layers, e.g. amount of leaves per layer [-], fresh weight of leaves, stems and fruits per
layer [g], dry weight of leaves, stems and fruits per layer [g], dry matter content, leave
area per layer [m2], LAI per plant [-], SLA per plant [g m-2]. Destructive measurements of
the four pot plants were carried out after six weeks and at the end of the crop growth
period. Next to the parameters mentioned above, the length of the plant [cm], the amount
of lateral shoots [-], dry weight and fresh weight of buds and flowers [g] and the time of
flowering [date] were measured for the flowering pot plants. Leave orientation was
determined with 2D and 3D image analysis techniques.
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RESULTS AND DISCUSSION
To estimate the potential of diffuse greenhouse covering materials, the amount of
natural global radiation has to be known. The Dutch climate is characterised by 3650 MJ
m-2 global radiation per year, of which 1081 MJ m-2 direct light. This amount can be
potentially transformed into diffuse light, the rest is already diffuse. Only 200 MJ m-2 of
the direct light occurs during the winter month, 880 W/m2 during the summer month. It
can be assumed that a diffuse covering material will give the most advantages during
spring, summer and autumn months. However, as long as no light losses appear under the
covering, no disadvantages are to be expected during the winter months.
During the experiments, the greenhouse climate in the different treatments (diffuse
or natural) was comparable (Table 1Error! Reference source not found.).
Measurements in cucumber showed that crop temperature in higher leaf layers in the crop
was 0.2-0.8°C lower in the diffuse treatment, but was 0.4°C higher in the lower layers on
days with high irradiation (data not shown). The amount of PAR light under the diffuse
covering was about 4% less than under the other treatment (Fig. 2). However, the
horizontal light distribution was much more equally under the diffuse covering (Fig. 3).
Measurements of light distribution inside the cucumber crop showed that after three
weeks of growth, more than 85% of the light was being intercepted by the crop and a
difference in light interception between treatments could be observed. More light was
intercepted in the diffuse treatment on clear days, especially by the intermediate leaf
layers (Fig. 4). No difference in light interception between the diffuse and direct light
treatments was observed on cloudy days (data not shown). Leaves at intermediate leaf
layers on the main stem as well as young leaves on the secondary branches had a higher
rate of photosynthesis at normal light conditions (500 µmol m-2 s-1) in diffuse light (Fig.
5). Photosynthesis at light-saturating conditions (1250 µmol m-2 s
-1) was higher under
direct light and in all leaf layers. Upper and middle leaves also contained more
chlorophyll when grown under diffuse light, whereas lower leaves showed lower SPAD
values (Table 2Error! Reference source not found.).
It can be concluded that more light is absorbed by the middle leaf layers and
photosynthesis is increased, thus the assimilation rate was higher due to diffuse light. The
crop temperature probably influenced this process as well, as it was much higher under
direct than under diffuse light conditions. According to theory, the physiologically older
leaves deeper in the crop receive less light, have less RuBisCo and are photosynthetically
less active. RuBisCo was found to be slightly higher in diffuse light and decreased in
lower layers of the crop (Table 3Error! Reference source not found.). This may be due
to a better light absorption in the middle of the crop so that RuBisCo is still able to
actively contribute to the photosynthesis process without being broken down and
reallocated to younger parts of the crop receiving more light.
The proportion harvested cucumbers in relation to plant biomass increased from
June onwards due to diffuse light. Cucumber production in kilo’s increased by 4.3% and
the number of cucumbers increased by 7.8% (data not shown). The fruits were somewhat
smaller on average. However, the light transmission in the diffuse light treatment was ca.
4% lower than under clear covering. Given the same light transmission, the difference
between treatments would have been even greater. With 4% more light, the estimated
difference in production would have been 7.8% in kilo’s and 11% in number of fruits.
This increase in production might have been actually realized if suppliers had been able to
produce greenhouse roof material without the loss of light transmission in the process.
The quality of fruits was judged on a regular basis and was slightly lower in the diffuse
light treatment. However, this did not influence the longevity of the fruits after harvest.
Similar positive effects of diffuse light have also been shown with pot plants. The
growth rate of all pot plants was increased. After six weeks chrysanthemum showed a
higher plant height, more branches, more leaves, a higher leaf area, a higher leaf and stem
dry weight, a higher relative growth rate (RGR) and more flowers. Comparable results
were observed for the other three species of pot plants after six weeks (data not shown).
Similar to the photosynthesis in cucumber, that of the four pot plant species was higher
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under diffuse light than under the clear covering (Fig. 6). Crop experiments with pot
plants were conducted in autumn to analyze the effect diffuse covering materials in
different seasons. The positive effects of diffuse light were clearly visible until the
beginning of November (week 45). After that the light loss of the covering used in the
experiments, about 4%, overruled the positive effects of diffuse light. Since the
experiment with chrysanthemum was finished by then, no negative effects were observed
(Table 4Error! Reference source not found.). The experiment with Ficus, however,
continued until the beginning of December (week 49). From Error! Reference source
not found. it can be clearly seen that the growth rate decreased in December as a result of
lower light levels in the diffuse treatment.
CONCLUSIONS
In conclusion, diffuse light has a positive influence on the production of cucum-
bers, especially during the summer. This positive effect can be explained by a change in
light penetration into the crop and by an increased photosynthesis capacity, so that a crop
like cucumber can utilize diffuse light better than direct light. In addition, diffuse roof
material results a lower crop temperature, especially higher in the crop which likely leads
to a more optimal conditions for photosynthesis.
In our opinion, a diffuse roof material for greenhouses with a minimal loss of light
should be further developed. This means that materials should be used with minimal 50%
haze, a light transmission of at least 90% (perpendicular) and 82% (hemispherical). A
lower light transmission will result in a loss of production, especially in the winter when
light is the limiting factor. Diffuse light in the crop is actually less important in the winter
because most of the natural light is already diffuse due to the predominantly cloudy
weather. The advantage of diffuse light can be realized in late spring, summer and early
autumn when natural light has a more direct character, and when too much (direct) light
in undesirable for many crops. In an earlier study, Hemming et al. (2005) examined the
economic prospects of diffuse roof material and concluded that at a 5% production
increase is possible and a diffuse roof material can be profitable. Diffuse covering
materials have potential advantages for other crops as well, i.e. sweet pepper, as well as
for cut flowers like rose.
ACKNOWLEDGEMENTS
This research is funded by the Dutch Ministry of Agriculture, Nature and Food
quality (LNV) in the scope of the research programme “Energy in protected cultivation”.
Literature Cited
DeLucia, E.H., Nelson, K., Vogelmann, T.C. and Smith, W.K. 1996. Contribution of
intercellular reflectance to photosynthesis in shade leaves. Plan, Cell and Environment
19: 159-170.
Farquhar, G.D. and Roderick, M.L. 2003. Pinatubo, diffuse light and the carbon cycle.
Science 299: 1997-1998.
Goudriaan, J. 1988. The bare bones of leaf-angle distribution in radiation models for
canopy photosynthesis and energy exchange. Agric. and Forest Meteo. 43: 155-169.
Gu, L., Baldocchi, D.D., Wofsy, S.C., Munger, J.W., Michalsky, J.J., Urbanski, S.P. and
Boden, T.A. 2003. Response of a Deciduous Forest to the Mount Pinatubo Eruption:
Enhanced Photosythesis. Science 299: 2035-2038.
Hemming, S., Dueck, T., Marissen, N., Jongschaap, R., Kempkes, F. and van de Braak,
N. 2005. Diffuus licht – Het effect van lichtverstrooiende kasdekmaterialen op
kasklimaat, lichtdoordringing en gewasgroei. Wageningen UR report 557.
Hemming, S., van der Braak, N., Dueck, T., Elings, A. and Marissen, N. 2005. Filtering
natural light by the greenhouse covering – More production and better plant quality by
diffuse light? Acta Hort. 711: 105-110.
Hovi, T., Nakkila, J. and Tahvonen, R. 2004. Interlighting improves production of year-
round cucumber. Scientia Horticulturae 102 (3): 283-294.
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Lakso, A.N. and Musselman, R.C. 1976. Effects of Cloudiness on Interior Diffuse Light
in Apple Trees. J. Amer. Soc. Hort. Sci. 101 (6): 642-644.
Marcelis, L.F.M., van den Boogaard, H.A.G.M and Meinen, E. 2000. Control of crop
growth and nutrient supply by the combined use of crop models and plant sensors. In:
Proc. Int. Conf. Modelling and Control in Agriculture, Horticulture and Post-Harvested
Processing. IFAC, p.351-356.
Sheehy, J.E. and Chapas, L.C. 1976. The Measurement and Distribution of Irradiance in
Clear and Overcast Conditions in Four Temperature Forage Grass Canopies. J. Appl.
Ecol. 13(3): 831-840.
Vogelmann, T.C., Bornman, J.F. and Yates, D.J. 1996. Physiologia Plantarum 98, 43-56.
Tables
Table 1. Greenhouse climate during the cucumber experiments using a diffuse and a clear
covering material in 2006.
Clear Diffuse Average
North/South
Day Air temperature [oC] North 23.8 23.9 23.8
South 24.1 24.1 24.1
Average Clear/Diffuse 24.0 24.0
Relative humidity [%] North 68.9 69.7 69.3
South 75.3 76.6 76.0
Average Clear/Diffuse 72.1 73.2
CO2-concentration [ppm] North 430.1 414.0 422.1
South 418.4 436.4 427.4
Average Clear/Diffuse 424.2 425.2
Opening ventilation [%] North 93.3 94.2 93.8
South 99.6 101.1 100.4
Average Clear/Diffuse 96.5 97.6
Table 2. Average SPAD-values (=f([chlorophyl] m-2)) of four different leaf layers of
cucumber, divided in stem and side branches, between 9th of May and 11th of July
2006. grown under a diffuse and clear covering.
Stem Side branches
Leaf layer Crop height Clear Diffuse Clear Diffuse
4 150-200 cm 45,1 48,4 53,5 53,2
3 100-150 cm 40,0 42,6 44,1 43,5
2 50-100 cm 37,6 34,6 - -
1 0-50 cm 32,6 29,6 - -
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Table 3. RuBisCo content (mg g-1 fresh weight) ± standard deviation in four different leaf
layers of cucumber at the 9th of May and 16th of June 2006, grown under a diffuse and
clear covering.
RuBisCo content [mg g-1 fresh weight]
9th of May RuBisCo content [mg g-1 fresh weight]
16th of June
Clear Diffuse Clear Diffuse
Leaf
layer Side
branch Stem Side
branch Stem Side
branch Stem Side
branch Stem
4 - 3,1±2,3 - 3,9±2,2 4,0±2,1 5,4±3,1 5,9±1,9 5,2±3,2
3 - 1,3±1,1 - 1,7±1,6 7,5±3,4 0,9±0,2 6,5±2,2 1,6±1,7
2 - 0,9±0,8 - 1,2±0,8 - - - -
1 - 0,6±0,4 - 0,8±0,6 - - - -
Table 4. Plant growth parameters of chrysanthemum grown under a diffuse or clear
covering. Significances are shown with * at α=0.05, n=10, ns=not significant, -
parameter not measured.
Week 41 Week 45
Clear Diffuse Clear Diffuse
Plant height [cm] 32.15 34.75 * 43.20 44.45 *
Number of branches [-] 4.50 5.50 * 4.90 4.85 ns
Number leaves [-] 71.0 93.2 * 78.2 88.7 *
Leaf area [cm2] 900 1148 * 1175 1347 *
Leaf dry weight [g] 1.96 2.42 * 2.53 2.93 *
Stem dry weight [g] 1.39 1.78 * 4.31 5.00 *
SLA [m2 g-1] - - - 0.047 0.046 ns
RGR [average g g-1 wk-1] 0.56 0.70 0.94 1.06
Number flowers [-] - - - 27.4 30.7 *
Flower dry weight [g] - - - 2.56 2.65 ns
Table 5. Plant growth parameters of Ficus grown under a diffuse or clear covering.
Significances are shown with * at α=0.05 and ** at α=0.10, n=10, ns=not significant, -
parameter not measured.
Week 41 Week 49
Clear Diffuse Clear Diffuse
Plant height [cm] 39.2 41.1 * 64.1 63.0 ns
Number of branches [-] 9.25 9.95 ** 12.8 13.0 ns
Number leaves [-] 31.5 34.0 ns 68.8 65.2 ns
Leaf area [cm2] 496 532 ** 1340 1247 **
Leaf dry weight [g] 2.02 2.11 ns 5.66 5.06 *
Stem dry weight [g] 0.93 0.92 ns 3.38 3.21 ns
RGR [average g g-1 wk-1] 0.49 0.51 0.65 0.59 *
SLA [m2 g-1] - - - 0.024 0.025 ns
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Figures
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
400 450 500 550 600 650 700
PAR transmission [-]
wavelength [nm]
F-Clean clear tdir
F-Clean clear tdiff
F-Clean diffuse tdir
F-Clean diffuse tdiff
τ
dir
τ
diff
τ
dir
τ
diff
Fig. 1. Optical properties of a diffuse (F-Clean diffuse on glass) and a clear (F-Clean on
glass) covering material used in experimental greenhouses.
y = 0.775x
R² = 0.995
y = 0.746x
R² = 0.997
0
10
20
30
40
50
60
0 20406080
inside
outside
PAR [mol m
-2
day
-1
]
Clear South Diffuse South
y = 0.777x
R² = 0.997
y = 0.720x
R² = 0.996
0
10
20
30
40
50
60
0 20406080
inside
outside
PAR [mol m
-2
dag
-1
]
Clear North Diffuse North
Fig. 2. PAR measurements inside and outside the greenhouse in experimental green-
houses covered with a diffuse and a clear covering.
Fig. 3. Horizontal light distribution in greenhouses covered with a diffuse and a clear
covering material on a clear day.
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0
50
100
150
200
250
0 204060801
00
Crop height [ cm]
Light interception [%]
April 19
th
, 2006
0
50
100
150
200
250
0 204060801
Crop height [cm]
Light interception [%]
May 3
rd
, 2006
Clear
Diffuse
00
Clear
Diffuse
0
50
100
150
200
250
0 204060801
00
Cro p height [cm]
Light interception [%]
April 25
th
, 2006
0
50
100
150
200
250
0 204060801
Crop height [cm]
Light interception [%]
May 23
rd
, 2006
Clear
Diffuse
00
Clear
Diffuse
Fig. 4. Vertical light distribution and light interception of a cucumber crop on four
different dates grown under a diffuse and a clear covering on four clear days.
0
5
10
15
20
25
Middle layer
stem
Upper layer
stem
Middle layer
branch
Upper layer
branch
Photosynthesis [µmol m-2 s-1]
June 28
th
, 2006
Diffuse
Clear
0
2
4
6
8
10
12
0 100 200 300 400 500
Photosynthesis [µmol m-2 s-1]
Light intensity [µmol m-2 s-1]
Diffuse
Clear
Fig. 5. Photosynthesis in two leaf layers of
a cucumber crop on June, 28th,
grown under a diffuse and a clear
covering
Fig. 6. Actual photosynthesis in four
different pot plant crops grown
under a diffuse and a clear
covering.
1300
... The simulated light interception with the same incident radiation showed that canopies could intercept diffuse light better than direct light. This corresponded with the study of Hemming on the effect of diffuse light, which indicated that an increase of the ratio of diffuse light could increase the photosynthesis of the canopy, and consequently increased the production [21]. Because diffuse light was scattered in all directions, it could penetrate deeper into a plant canopy compared to direct light. ...
... By means of diffuse light, a higher uniformity of light distribution could be realized [21]. This uniform light distribution helped realize equality in production. ...
... Modern covering materials could help create more diffuse light. These materials contained pigments and macro-or microstructures that transformed all the incoming direct light into diffuse light, without significantly reducing light transmission [21]. ...
... The simulated light interception with the same incident radiation showed that canopies could intercept diffuse light better than direct light. This corresponded with the study of Hemming on the effect of diffuse light, which indicated that an increase of the ratio of diffuse light could increase the photosynthesis of the canopy, and consequently increased the production [21]. Because diffuse light was scattered in all directions, it could penetrate deeper into a plant canopy compared to direct light. ...
... By means of diffuse light, a higher uniformity of light distribution could be realized [21]. This uniform light distribution helped realize equality in production. ...
... Modern covering materials could help create more diffuse light. These materials contained pigments and macro-or microstructures that transformed all the incoming direct light into diffuse light, without significantly reducing light transmission [21]. ...
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... Also, in terms of light quality, under the pearl PSN there is a higher amount of dispersed light when compared to the other treatments (Shahak, 2008), which can help females and males in the colony localization. The pearl PSN improves light penetration into the most shaded canopies compared to direct light (Hemming et al., 2008). Thus, when compared to the other treatments, the light under the pearl PSN is more available within the canopy and more evenly distributed in the environment (Hemming et al., 2008;Kong et al., 2013). ...
... The pearl PSN improves light penetration into the most shaded canopies compared to direct light (Hemming et al., 2008). Thus, when compared to the other treatments, the light under the pearl PSN is more available within the canopy and more evenly distributed in the environment (Hemming et al., 2008;Kong et al., 2013). It is possible that under our experimental conditions, the coccinellid preferred more indirect light conditions provided by the pearl PSN instead of direct light. ...
Article
Photo-selective nets (PSNs) can increase agricultural crop production by modifying the quantity and quality of light that reaches the plants. PSNs also have the potential to affect arthropod pest populations and their natural enemies. The present study aimed to assess the impact of PSN systems on coccinellid predation. Experiments were carried out in microcosm conditions to evaluate the efficiency (prey localization and predation) of the multicolored Asian lady beetle, Harmonia axyridis (Pallas), when preying on the green peach aphid, Myzus persicae (Sulzer), on potato plants. Three colors of nets were tested and compared to control (no net): black SN (standard net), pearl PSN, and red PSN, using H. axyridis third-instar larvae (L3), females and males. We hypothesized that pearl and red PSN and black SN would alter the predator behavior, delaying the time to aphid colony localization, or by reducing overall aphid predation. Our results showed that aphid colonies were not affected by any PSN or the black SN in the absence of predators. Aphid colony localization by adult coccinellids was delayed under black SN, and favored under pearl PSN, but overall aphid predation was unaffected by net type. There were no significant differences among treatments in interplant movement of L3, females, or males. We conclude that, under laboratory conditions, pearl PSN, red PSN, and black SN can affect aphid colony localization by H. axyridis, but do not affect predation efficiency. Subsequent trials in the field would be required to further clarify the effects of PSNs on H. axyridis foraging behavior.
... Meteorological factors are important conditions in the growth of crops and are related to farm animal health, human health, and residential suitability (Hu et al., 2019;Seymour, 2016). The primary consideration for inhabitants is food satisfaction, and the TEM, PRE, EVP, and SSD groups determined the type and growth season of crops, which selected, to some extent, the style of production and social characteristics (McLeman and Smit, 2006;Hemming et al., 2008;Hu et al., 2011;Che et al., 2014;Cui et al., 2019;Fletcher et al., 2020). In addition, other climatic factors have an impact on comfort level and human heath, such as TEM, APR, and RHU (Tsutsumi et al., 2007;Davis et al., 2016;Yang and Matzarakis, 2019;Raymond et al., 2020). ...
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The geospatial distribution pattern in traditional Chinese settlements (TCSs) reflects the traditional harmony between humans and nature, which has been learned over centuries. However, TCSs have experienced serious disturbances by urbanization and migration. It is crucial to explore the local wisdom of geospatial patterns and dominant factors for TCSs at the national scale in China. This study sought to determine the geospatial wisdom of traditional settlements to enrich our future settlement development with the aim of establishing Chinese settlement values for modern living. Herein, a dataset of 4000 TCSs were analyzed and clustered for environmental factors that affect their geospatial patterns by machine learning algorithms. We concluded that (1) five geospatial patterns of TCSs were clustered on a national scale, and the threshold of environmental factors of TCS groups was detected. (2) Environmental conditions and settlement concepts interacted and determined the similarities and differences among TCS groups. (3) The key boundary for TCSs and the dominant factors for each zone were determined, and topographical conditions and hydrologic resources played significant roles in all five TCS zones. This study provides a better understanding of the adaptability of the environment in relation to the TCSs and aids in planning TCS conservation and rural revitalization.
... New cover materials have been developed, such as photo-selective films but also diffuse-light films, which have the characteristic to distribute the photosynthetically active radiation (PAR) in a more uniform manner to all the leaves of the canopy [25], with an overall improvement of the growth and development of the plants [26,27]. Fausey et al. [28] observed a linear relationship between the amount of light and dry mass of shoots in several perennial herbaceous species grown in greenhouses, and Hemming et al. [29] recommended the use of cover material with a minimum diffusivity of 50% and a transmittance of 90%. Conditions of high diffuse radiation elicit a plant production increase as a result of a higher efficient yield per unit of PAR [30]. ...
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The quantity and quality of wall rocket (Diplotaxis tenuifolia L.) production are strongly influenced by the cultivation system, in particular the protected environment conditions and nitrogen fertilization. In the present research, we tested two greenhouse cover films (Film1: diffuse light; Film2: clear), to verify the effects on yield and nitrate content (a detrimental factor of quality) of rocket leaves, fertilized with optimal (N2) or sub-optimal nitrogen dose (N1), or unfertilized (N0). In addition, we combined the N fertilization with a biostimulant application, declared by the manufacturer as able to reduce nitrate content. Film1 provided a 36% yield increase over Film2 and allowed an increasing production until the V harvest, opposite to what was recorded under Film2, where the yield increased only until the III harvest. Additionally, biostimulant application boosted the yield (+40%), as well as nitrogen fertilization. Both factors had the best performance under Film1, where N1 yield was even equal to N2-Film2. The nitrate content showed a seasonal trend (lower values in spring harvests) and it was boosted by nitrogen (1096, 3696, and 4963 mg/kg fresh weight, for N0, N1, and N2, respectively) and biostimulant application (3924 vs. 2580 mg/kg fresh weight). Therefore, the use of diffuse-light film seems useful to obtain higher yield with a halved N dose as well as in combination with biostimulant application, but the latter did not confirm the capacity to contain nitrate, at least for this crop and in this cultivation system.
... Looking beyond hot climates, this solution could be also useful for greenhouses where light needs to be spread equally on all the plants. 35 FTIR spectrum shown in Figure 6b is typical for cellulose-based materials. The total absorption around 1000 cm -1 indicates the porous material would absorb mid-IR from black body emission of objects at room temperature. ...
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Improving building energy performance requires the development of new highly insulative materials. An affordable retrofitting solution comprising a thin film could improve the resistance to heat flow in both residential and commercial buildings and reduce overall energy consumption. Here we propose cellulose aerogel films formed from pellicles produced by the bacteria Gluconacetobacter hansenii as insulation materials. We studied the impact of density and nanostructure on the aerogels' thermal properties. Thermal conductivity as low as 13 mW/(K*m) was measured for native pellicle-based aerogels dried as-is with minimal post-treatment. The use of waste from the beer brewing industry as a solution to grow the pellicle maintained the cellulose yield obtained with standard Hestrin-Schramm medium, making our product more affordable and sustainable. In the future, our work can be extended through further diversification of the sources of substrate among food wastes, facilitating larger potential production and applications.
... In addition to the standard poly, growers are trying different poly covers to alter light characteristics, such as luminance or diffuse poly, to improve crop performance [20]. Luminescence poly can prevent direct sunlight and avoid high temperatures in the tunnel, thus reducing plant stress and improving plant growth. ...
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Spectral characteristics of solar radiation have a major role in plant growth and development and the overall metabolism, including secondary metabolism, which is important for the accumulation of health-promoting phytochemicals in plants. The primary focus of this study was to determine the effect of spectral characteristics of solar radiation on the nutritional quality of lettuce (Lactuca sativa L., cv. red leaf ‘New Red Fire’ and green leaf ‘Two Star’ and tomato (Solanum lycopersicum L., cv. BHN-589) grown in high tunnels in relation to the accumulation of essential nutrients and phytochemicals. Solar spectrum received by crops was modified using photo-selective poly covers. Treatments included commonly used standard poly, luminescence poly (diffuse poly), clear poly, UV blocking poly, exposure of crops grown under the standard poly to full sun 2 weeks prior to harvest (akin to movable tunnel), and 55% shade cloth on the standard poly. All the poly covers and shade cloth reduced the PAR levels in the high tunnels, and the largest reduction was by the shade cloth, which reduced the solar PAR by approximately 48%. Clear poly allowed the maximum UV-A and UV-B radiation, while standard poly allowed only a small fraction of the solar UV-A and UV-B (between 15.8% and 16.2%). Clear poly, which allowed a higher percentage of solar UV-A (60.5%) and UV-B (65%) than other poly covers, increased the total phenolic concentration and the antioxidant capacity in red leaf lettuce. It also increased the accumulation of flavonoids, including quercetin-3-glucoside, luteolin-7-glucoside, and apigenin-3-glucoside in red leaf lettuce, compared to the standard poly. Brief exposure of crops grown in high tunnels to full sun prior to harvest produced the largest increase in the accumulation of quercetin-3-glucoside, and it also resulted in an increase in luteolin-7-glucoside and apigenin-3-glucoside in red leaf lettuce. Thus, clear poly and brief exposure of red leaf lettuce to the full sun, which can increase UV exposure to the plants, produced a positive impact on its nutritional quality. In contrast, shade cloth which allowed the lowest levels of solar PAR, UV-A and UV-B relative to the other poly covers had a negative impact on the accumulation of the phenolic compounds in red leaf lettuce. However, in green leaf lettuce, luminesce poly, clear poly, UV-block poly, and shade treatments increased the accumulation of many essential nutrients, including protein, magnesium, and sulfur in green leaf lettuce compared to the standard poly. Poly cover treatments including shade treatment did not affect the accumulation of either carotenoids (lutein, β-carotene, and lycopene) or essential nutrients in mature tomato fruits. The results show that clear poly cover can enhance the accumulation of many phenolic compounds in red leaf lettuce, as does the brief exposure of the crop to the full sun prior to harvest. Thus, UV radiation plays an important role in the accumulation of phenolic compounds in red leaf lettuce while the overall spectral quality of solar radiation has a significant influence on the accumulation of essential nutrients in green leaf lettuce.
... Protective covering in low-tech greenhouses influences the micro-environment primarily as a result of alteration in light intensity and quality; these interact with various physio-biochemical plant processes, thereby affecting plant growth and development [7,24]. In protected structures, NVP showed a more positive effect on the growth of cucumber plants than the net houses (INP and SNH), whereas among the net houses, INH was better for various growth parameters. ...
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Protected vegetable cultivation is a fast-growing sector in which grafting plays a crucial role for success. Cucumber is predominantly grown under protected conditions. The popular slicing (mini) cucumber comprises two segments, single- and cluster-fruit-bearing. In the present study, the performance of select fruit-bearing hybrids grafted as scions onto commercial Cucurbita hybrid rootstock ‘NS-55’ was evaluated under three different low-cost protected structures in arid regions.With respect to type of protected structure, cucumber performance was superior under a naturally ventilated polyhouse (NVP) than an insect net house (INH) or a shade net house (SNH). Micro-climate parameters inside NVP (air temperature, RH and PAR) were more congenial for cucumber than those in net houses, thereby facilitating improved physiology (chlorophyll fluorescence, chlorophyll and plant water potential) and leaf mineral status. Grafting invariably improved growth and yield parameters under all protected structures. Overall plant performance was better in the grafted clusterfruit-bearing hybrid ‘Terminator’ than the single-fruit-bearing hybrid ‘Nefer’ or their non-grafted counterparts. Furthermore, NVP was found to be superior to net houses for water productivity, and grafted plants were more water use efficient than their counterpart non-grafted plants. Thus, NVP can be considered a suitable low-cost protected structure in conjunction with grafting to boost cucumber crop and water productivity in arid regions.
... The positive effect on yield can be explained by the higher amount of diffuse radiation that this type of netting provides, resulting in greater light availability for the plant. These results agree with previous studies in which shade nets with a greater capacity to increase diffuse light significantly increased fruit yield in other horticultural crops due to an increased plant photosynthetic capacity (Hemming et al. 2008). In addition, pearl-gray netting significantly increased fruit weight, fruit diameter, and seed weight (Table 2). ...
Article
Photo-selective colored nets have been used as a tool to reduce climatic stress and improve yields in horticultural crops, but there is no knowledge regarding responses of hazelnut crops under these nets. The objective of this research was to study the influence of photo-selective nets on the microclimate, physiological characteristics of leaves, and yield in hazelnut. During three consecutive seasons, a hazelnut orchard ´Tonda di Giffoni´ was covered with black, blue-gray, and pearl-gray colored nets with a standard density of 4 warp and weft threads cm−1. Uncovered trees were used as the control. Microclimatic conditions (solar radiation intensity and composition, air temperature, relative humidity, and vapor pressure deficit, VPD), yield components (accumulated yield; yield by harvest date; fruit weight, FW; and seed weight, SW), and leaf physiological characteristics (net photosynthesis rate, An; stomatal conductance, gs; specific leaf weight, SLW; and stomatal density, SD) were evaluated. Pearl-gray netting had the greatest increase in diffuse (47%) and global (5%) solar radiation compared to blue-gray and black nettings. VPD decreased by 12% under black netting, but only by 5% under pearl-gray and blue-gray netting. Pearl-gray nets significantly increased accumulated yield, FW, and SW by 12, 13, and 6% compared to the control, respectively. Black and blue-gray nets reduced SD by 8 and 30% and SLW by 15 and 20%, respectively. Pearl-gray netting did not alter either SD or SLW. A significant relationship between An and gs was found under all nets, but not for the control. The relationship between An and gs was significantly positive for pearl-gray netting and negative for blue-gray netting. Photo-selective netting is a physiology-based tool that improves yield in hazelnut orchards under extreme climate conditions. Pearl-gray netting is the most promising alternative for this fruit crop.
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Volcanic aerosols from the 1991 Mount Pinatubo eruption greatly increased diffuse radiation worldwide for the following 2 years. We estimated that this increase in diffuse radiation alone enhanced noontime photosynthesis of a deciduous forest by 23% in 1992 and 8% in 1993 under cloudless conditions. This finding indicates that the aerosol-induced increase in diffuse radiation by the volcano enhanced the terrestrial carbon sink and contributed to the temporary decline in the growth rate of atmospheric carbon dioxide after the eruption.
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(1) An instrument is described for measuring the distribution of irradiance in grass canopies. (2) The irradiance distributions for overcast and clear conditions were quite distinct; light from an overcast sky was more uniformly spread through the canopies than light from a clear sky. (3) Each of the four cultivars had its own characteristic irradiance distribution pattern which was maintained in clear and overcast conditions. The extinction coefficients ranged from 0.11 to 0.16 for S345 and 0.80 to 1.20 for S24 in overcast and clear conditions. The relative ranking of cultivars for the extinction coefficients, measured in clear and overcast conditions, and mean leaf angle were identical, suggesting that the angular structure of the canopy plays an important part in determining light distribution in grass canopies. The results suggest that, in a grass canopy, the distribution of light coming directly from the sun may be satisfactorily described by Monteith's S function.
Article
Three cucumber stands (Cucumis sativus L. cv. Cumuli) were grown in southern Finland to investigate the effects of two supplemental lighting regimes on yield and efficiency of electricity consumption in lighting for year-round production. The lighting regimes examined included top lighting (TL), where all of the lamps were mounted above the canopy and top + interlighting (T + IL) which comprised 75% of top lamps and 25% of the lamps mounted vertically 1.3 m above the ground between the single plant rows. The artificial photosynthetic photon flux (PPF) near the plant rows, the air temperature and vapour pressure deficit (VPD) in the canopy were noted to be slightly higher in T + IL than in TL. The total (natural + artificial) PPF inside the greenhouse during cultivation of the winter, spring and summer stands were 19.4, 29.5 and 38.6molm−2day−1 in TL and 20.4, 31.5 and 41.2molm−2day−1 in T + IL, respectively. Top + interlighting was shown to enhance cucumber productivity; T + IL increased the annual total and first class fruit weight and number, fruit size and percentage of first class fruit. A total annual increase of 20% in first class fruit weight was achieved through a 6% increase in electricity consumption for lighting purposes. The first class fruit weights in winter, spring and summer stands were 32.0, 42.1 and 30.8kgm−2 in TL and 38.2, 55.4 and 32.1kgm−2 in T + IL, respectively. The efficiency of electricity consumption for lighting was better for the whole year in T + IL than in TL (120g versus 108g first class fruit weight kWh-1). Efficiency varied between stands; T + IL proved more efficient than TL during the winter and spring seasons, whereas TL was more efficient in summer.
Article
The potential contribution of intercellular light reflectance to photosynthesis was investigated by infiltrating shade leaves with mineral oil. Infiltration of leaves of Hydrophyllum canadense and Asarum canadense with mineral oil decreased adaxial leaf reflectance but increased transmittance. As a result of the large increase in transmittance, infiltration caused a decrease in absorptance of 25% and 30% at 550 and 750 nm, respectively. Thus, intercellular reflectance increased absorptance in these species by this amount. In a comparison of sun and shade leaves of Acer saccharum and Parthenocissus quinquefolia, oil infiltration decreased absorptance more in shade than in sun leaves. This difference suggests that the higher proportion of spongy mesophyll in shade leaves may increase internal light scattering and thus absorptance. The importance of the spongy mesophyll in increasing internal reflectance was also evident in comparisons of the optics of Populus leaves and in the fluorescence yield of oil-infiltrated leaves of several sun and shade species. Oil infiltration decreased the quantum yield of fluorescence (Fo) by 39–52% for shade leaves but only 21–25% for sun leaves. We conclude that the greater proportion of spongy parenchyma in shade leaves increased intercellular light scattering and thus absorptance. Direct measurements with fibre-optic light probes of the distribution of light inside leaves of Hydrophyllum canadense confirmed that oil infiltration decreased the amount of back-scattered light and that most of the light scattering for this species occurred from the middle of the palisade layer to the middle of the spongy mesophyll. We were not, however, able to assess the potential contribution of reflectance from the internal abaxial epidermis to total internal light scattering in these experiments. Using a mathematical model to compare the response of net photosynthesis (O2, flux) to incident irradiance for control leaves of H. canadense and theoretical leaves with no intercellular reflectance, we calculated that intercellular reflectance caused a 1.97-fold increase in photosynthesis at 20 μmol m−2s−1 (incident photon flux density). This enhancement of absorption and photosynthesis by inter-cellular reflectance, without additional production and maintenance of photosynthetic pigments, may maintain shade leaves above the photosynthetic light compensation point between sunflecks and maintain the light induction state during protracted periods of low diffuse light.
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The effects of leaf-angle distribution in radiation models for canopy photosynthesis and energy exchange can be accurately described by using as few as three leaf-angle classes (0–30°, 30–60° and 60–90°). On this basis, simple equations have been developed and tested for reflectance, extinction and distribution of radiation in leaf canopies. In these equations the spherical leaf-angle distribution, default in most models, serves as a point of reference.
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Verslag van een project waarin de potenties van het gebruik van diffuus licht in de Nederlandse kastuinbouw onderzocht wordt.
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Similar to clouds, volcanic eruptions increase the proportion of diffuse light reaching Earth's surface. As Farquhar and Roderick show in their Perspective, this change in the geometry (rather than intensity) of light can have a profound influence on photosynthesis and the carbon cycle. They highlight the research article by Gu et al ., who have measured changes in net COexchange following the eruption of Mt. Pinatubo in 1991. Volcanoes, pollution, and greenhouse gases may all increase diffuse light, with important consequences for Earth's carbon cycle and climate.
Filtering natural light by the greenhouse covering -More production and better plant quality by diffuse light? Acta Hort
  • S Hemming
  • N Van Der Braak
  • T Dueck
  • A Elings
  • N Marissen
Hemming, S., van der Braak, N., Dueck, T., Elings, A. and Marissen, N. 2005. Filtering natural light by the greenhouse covering -More production and better plant quality by diffuse light? Acta Hort. 711: 105-110.