Conference PaperPDF Available

Plant Lighting Aspects for Plant Growth in Controlled Environments

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CIE 197:2011 ISBN 978 3 901906 99 2
PROCEEDINGS
Volume 1 Part 1
SUN CITY/SOUTH AFRICA • 10 JULY – 15 JULY 2011
CIE 27th Session • Sun City/ZA430
Navvab, M. • Lighting Aspects for Plant Growth in Controlled Environments
LIGHTING ASPECTS FOR PLANT GROWTH IN CONTROLLED
ENVIRONMENTS
Mojtaba Navvab
The University of Michigan
TCAUP, Arch Bldg.,2000 Bonisteel Blvd.
Ann Arbor MI 48109-2069, Voice: 734-936-0228
E-mail: moji@umich.edu
Abstract
The effective use of daylighting in the design of buildings is encouraged by design communities for
the benets of sustainability through the application of the guidelines established by the US Green
Building Council (USGBC). The Matthaei Botanical Garden Conservatory (MBGC) provides an indoor
environment for plants from many regions of the world. The garden space is divided into three different
thermal climatic conditions, namely tropical, temperate and arid. The results of one year measurements
of variables essential to plants’ growth within MBGC indicate that acclimatized plants could play a major
role in daylight design integration. This study aims to provide data to support recommendations by the
industry at large, to maintain a controlled environment in which plants can grow; the interaction of optical
radiation with other environmental parameters needs to be integrated. The time series data provide new
opportunities to examine and identify new optical sources suitable for plant culture in the absence of
daylight as a source.
Keywords: Spectral Power Distribution, Plants, Photosynthesis Rate, Carbon Dioxide, Daylight
1 Introduction
It is proven that daylighting systems and good indoor air quality are common features of sustainable
building design which do impact the occupants’ wellbeing and productivity. Plants are as much a part of
the architectural design of today’s interior design as are lighting and furniture. The interior landscaping
industry has grown ten-fold in the last decade. There is not a building constructed today without some
major effort given to interior landscaping. There is a plant loss of 20 to 40 percent each year for all
interior-scape projects due to various factors such as the quality of the soil, water, drainage, planters,
lighting systems and available daylight with its dynamics.
The MBGC is located in the City of Ann Arbor, Michigan, USA. Conservatory space provides an indoor
environment for plants in three different climatic conditioned spaces, namely tropical, temperate and
arid. These thermal climatic conditions are archived by the operational settings of the HVAC system
for each conditioned zone. Air temperature, relative humidity, solar irradiance and daylight illuminance
levels, Photosynthetically Active Radiation (PAR), Carbon Dioxide CO2, wind velocity, direction, rain
fall, and the accumulated solar exposure are measured within each climatic zone within and outside of
MBGC. The spectral power distribution is measured at selected times in specic areas and within each
climatic zone conditioned.
1.1 Lighting for Plants
Any daylighted building is impacted by the local climate. Given daylight as a light source for interior
plants in buildings, the lighting designer has to provide the position of the source (aperture size and
location) windows, skylights and their integration with the electrical lighting system. Since skylights are
totally exposed to the sky, fully automated or manually operable shading devices are essential. Daylight
is admitted primarily through the ceiling or the windows. Plants are mostly positioned on a vertical plane.
This has created a new plane for calculation where the vertical illuminance should be at least equal to
the horizontal illuminance. These factors produce various lighting conditions which are desirable or
undesirable depending on the lighting designers’ objectives. Factors to consider on lighting for interior
landscaping are as follows:1. Solar and daylight availability; 2. Distribution of Light; 3. Glazing system;
4. Light source; 5. Temperature environment; and 6. Plant types.
CIE 27th Session • Sun City/ZA 431
Navvab, M. • Lighting Aspects for Plant Growth in Controlled Environments
2.1 Solar and daylight Availability
The solar spectral irradiance falling on earth decreases as a function of the atmospheric conditions.
Air mass is determined by the slant path from the sun to Earth. The solar spectral irradiance is the
distribution of the solar constant radiant power as a function of wavelength in the absence of the Earth’s
atmosphere. The solar constant of 1367 W/M2 has 96% of its solar spectral irradiance contained in
the wavelength range from 270 to 2600 nm, while 49.6% lies in the 400 to 760 nm waveband. Figure
1 shows the standard NASA/ASTM solar irradiance for air mass = 0 (outside the Earth’s atmosphere),
air mass 1, and air mass 2, with their spectral irradiance values on Earth. It is noticeable that half of
the solar radiation is in the wavelength range that serves the human eye for vision and plants. Although
today’s’ climate and or stratospheric changes due to global warming may result in a very small increase
in the total solar energy, nonetheless, a disproportionate increase in the UVR below 340 nm would
increase the hazards of UVR. Such an increase would be very dangerous to animal and plant life
including humans. Figure 2 shows the total, direct sun and sky illuminance reaching earth as a function
of height (Pitts, Navvab 1995, Sliney 1980).
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Figure 1. Spectra Irradiance vs. air mass. Figure 2. Daylight availability vs. solar height
2.2 Distribution of light
The use of skylights with a tinted or fritted glazing system in addition to an automatic shading and
lighting system allows control of the distribution, intensity and duration of light; but it may not prevent the
plants’ exposure to ultraviolet and infrared wavelengths on either side of the visible spectrum. Bottom
leaves drop when light enters from above the plant vertically and lters throughout the canopy, leaving
little light reaching lower leaves. If light strikes the plant from the side (horizontally), the plant will bend in
the direction of the light. The shape of the tree is based on the sky or daylight distribution. For tall plants
supplemental interior lighting must be properly designed for good light distribution. The following factors
lter out valuable light: Tinted glass; Curtains; Building overhangs; Trees beyond window (especially
evergreens). Where the daylight is not uniform due to the fenestration design, the electric lighting
system and its distribution should do the job. Some vertical light helps to give a balanced shape, but if
the space is predominantly vertically lit, it may be necessary to position electrical light sources to provide
compensating illumination. Another strategy is to rotate plants to give growth signals to all sides. The
candlepower distribution of the lighting system is also important for the light distribution inside the space.
2.3 Glazing system
The glazing system and specic coating should be carefully selected. The glazing system used for the
MBG has two-layer glass which does not exceed 12 mm (1/2”) with PVB. Figure 3 shows the UM MBG
Arid zone and spectral transmittance of its glazing system. The UV transmittance is needed for the
animals and certain owers and is the key criteria for selecting the glazing system for botanical gardens
(Navvab 2005).
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Navvab, M. • Lighting Aspects for Plant Growth in Controlled Environments
2.4 Light sources
Electrical lighting systems provide part or most of the plants’ light level requirements indoors. The
illuminance levels should be between 2500 and 7500 lux, depending on the plant species used according
to IESNA (IESNA 1994). These light level requirement tables have not been upgraded during the last
four revisions of the handbook. A wide frequency spectrum is desirable (400 to 800 nm at least) to
activate all the plants’ functions. Color rendition can be a problem with some selected light sources.
A limited spectral output may be selectively absorbed by leaves. Fluorescent lighting can be very well
color-balanced, while mercury and sodium light are not easy to modify for color. Mercury lights tend
towards the blue end of the spectrum and sodium emits either a single wavelength yellow or a broader,
but still orange, color.
Figure 3. The UM-Botanical Garden arid zone and spectral transmittance of glazing system
Under Sun light leaves may appear gray or black. Despite this, of these latter types of sources, the
high-intensity discharge lamps, are favored for atrium lighting because they are efcient in high spaces
and their spectral characteristic can be altered with theatrical lighting lters to achieve the desired dark
period for plants. As part of the research collaborative effort among UM_TCAUP, School of Natural
Resources & Environment and support from industry representative “Planterra”, specic interior plants
were chosen for examining the impact of selected light sources on their growth. Each plant is located to
receive low and medium and high levels of light from a specic light source.
Figure 4. Full view of an indoor experimental set up for spectral power measurements
Figure 4 shows the full view of an indoor experimental set up for spectral power measurements under
two light sources: one (left) the Pipe light utilizing a sulfur light source and the other (right) HPS. Portable
data collection allows the measurements of the spectral power and the spectral reectance of the plant’s
leaves simultaneously. The objective is to correlate the amount of the spectral power from a specic
lamp to the photosynthesis’ rate produced by each lamp and its impact on the plants’ growth under
these specic conditions. The results would contribute to a series of recommended lighting schedule for
interior landscape design application including the light sources that contribute to the plants’ growth with
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Wavelength (nm)
% Transmittance
Extra clea r: 3+3+3 I G
Lami w/ Saflex PVB
Extra clea r: 3+3+3 I G
Lami w/ Uvekol PMMA
Older Clear: 5 mm
monolithic
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Navvab, M. • Lighting Aspects for Plant Growth in Controlled Environments
the least impact on the color of the interior environment.
Based on observation and measurements within various architectural projects, there is no evidence that
using special horticultural light sources in atria or interior spaces makes signicant differences in the
growth of acclimatized plants. Also, given current lighting design practices, the benets are too marginal
and color rendering is not at its best. To examine such effects of lighting systems on plant growth along
with the application of various electrical light sources with different spectral power distributions (e.g.
Incan, Fluor, HPS, HID, LED and Light Guiding system / Pipe with Sulfur light or daylight as a source);for
these lighting conditions are being investigated. Figure 5 shows the relative Spectral Power distribution
of these selected lamps (Bush-Brown 1996, Mpelkas 1981, Navvab 2005, 2009).
Figure 5. Spectral power distribution of various light sources under study of plant growth
2.5 Temperature Environment
The ideal temperature environment is between (16ºC or 62ºF) to (22ºC or 72ºF) with a relative humidity
of at least 50%. Temperatures greater than (29ºC or 85ºF) coupled with low lighting result in lowering of
plant vitality, and favors insect and disease reproduction. Temperatures less than (12ºC or 55ºF) may
cause chilling effects and produce damage to tropical plants. The degree of hardiness among plant
means some plants can withstand lower minimum winter temperatures (MWT) than others. Based on
the average MWT concept, The Botanical Garden building in Ann Arbor is within Zone 5. For example a
plant hardy in Michigan (zone 5) means it can survive a MWT of -29ºC to -23ºC (-20ºF to -10ºF). Figure
6 shows the measured hourly temperatures, humidity and total Irradiance within tropical zones and
the plant hardiness zones map based on average minimum winter temperature (MWT). Table 1 shows
specic zone limits within North America (Bickford 1973, Bush-Brown 1996).
2.6 Types of plants
Classication of plants used in interior landscaping: Tree: Grows as a single plant in container: Min.
Size 1 to 2 meter (m), Max. size 5m to 8m Examples: Weeping Fig, India Laurel, Japanese Loquai.
Floor Plant: Grows 0.4m to 1.5m tall. They are used separately or in groups. Examples: Norfolk Island
Pine, Lady Palm, Green Pleomele. Pot Plant: Wide Range of plants that grow in different size pots up to
0.20m. Examples: Asparagus Fern, Grape Ivy, Japanese Laurel.
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Incandescent 1 Incandescent 2 Fluorescent
Solfur HPS HID
Daylight- 01 Daylight-02 Daylight- 03
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3 Photo Response in Plants
Plants with their unique biology convert radiant energy into food. This process requires architects and
interior landscape designers to pay attention to plant lighting needs. There are two general lighting
system applications for horticultural needs: photosynthetic and photoperiods. Green plants take carbon
dioxide from the air and water and inorganic nutrients from the soil in the presence of light energy
from sunlight or electric light sources to produce carbohydrates. Foliage and light energy are both a
potential source of energy and loss of energy for the plants. Gain comes from photosynthesis and the
development of carbohydrates. Loss comes from respiration, using energy both in light and dark periods.
3.1 Photosynthesis
Photosynthesis is associated with green house lighting applications. The seasonal variations have limiting
factors and the lighting level shortcomings have to be satised by supplemental lighting as needed for
a given site location and the architectural design of the facility. There is a growing industry beyond the
environmental chambers or greenhouse design and their current uses in horticultural research for crop
growth studies which includes large scale commercial buildings, and is not limited to construction of
conservatories within hotels, resorts, retail stores and major shopping centers.
Table 1. Plant hardiness zones and the minimum winter temperatures (MWT).
zone 1 Below - - 50F/-46C
zone 2 - 50F/-46C to -40F/-40C
zone 3 - 40F/-40C to -30F/-34C
zone 4 - 30F/-34C to -20F/-29C
zone 5 - 20F/-29C to -10F/-23C
zone 6 - 10F/-23C to 00F/-18C
zone 7 00F/-18C to +10F/-12C
zone 8 + 10F/-12C to +20F/-7C
zone 9 + 20F/-7C to +30F/-1C
zone10 + 30F/-1C to +40F/+4C
Figure 6. Measured hourly temperatures, humidity and total Irradiance within tropical zones.
The lighting systems designed for these applications rely heavily on control of the photoperiod since
the use of these buildings given human occupancy schedules requires mixed use of electrical lighting
sources with different spectral distributions. The use of controls along with light lters provides the
specic band of spectrum and the plant exposure time from light to dark for owering in addition to the
simulation of the natural photosynthetic cycle needed for specic plants. Solar radiation does impact all
phases of plant growth. Photosynthesis is the key phase. While plants use the light along with water and
carbon dioxide to form carbohydrates, oxygen is released as a byproduct. Some amount of oxygen is
used during this process due to respiration. Although the respiration continues during the dark period,
the photosynthesis stops. The green pigments or green coloring by chlorophyll is a major index for the
action spectra during the photosynthetic carbon xation. Studies show the peak for both processes
occurs around 435 to 445 nm in blue and 650 to 675 nm in red, and if plants are left in the dark for a
few days, the chlorophylls decompose, and the yellowing of the leaves signals the plants’ destruction.
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Navvab, M. • Lighting Aspects for Plant Growth in Controlled Environments
Higher plants have three times more need of light than lower plants due to the differences in their
chlorophylls (Bickford 1973, Mpelkas 1981). The photo response is initiated by phytochrome reactions
which govern the growth response in plants. The phytochrome molecule is a blue color protein acting
as an enzyme in two reversal forms. One known as Pr or P660, and the second form is called (Pfr) or
P735 by the radiation that is absorbed. However, the second form can no longer absorb the red region
of the radiation. This is due to restoration needs of phytochrome to Pr or P660 which occurs during the
dark period at a slower rate. The rate depends on the temperature and humidity. Figure 7 shows the
spectral sensitivity functions on Relative Quantum Efciency (RQE); Phytochrome red absorbing state
(Ar) phytochrome far red absorbing state (Afr), Phototropic Response (Ptr); and, photopic and scotophic
sensitivity functions for human eye. Table 2 shows lighting requirements for some of these selected
plants (IESNA 1994, Bickford 1973). Daylight can be more benecial to plants than electric light sources.
In most cases, with the application of current information available on how to increase light duration,
daylight could be used for lighting interior plants. One of the major advantages in the application of
daylight for plants is its full spectrum and dynamic light qualities. The plants adapt to most extreme
lighting conditions, however a quite noticeable problem arises from the use of mixed light sources for
the illumination of plants. This causes color rendering distortions which become more obvious when light
sources of different color temperatures are aimed directly onto the plants’ area. As a plant emerges from
the seed, its photoreceptors are present. Plants with formed germination start the photosynthesis. The
following sections describe the effects of these factors and their impact on designs providing daylight
for plants. During photosynthesis, plants use energy in the region of the electromagnetic spectrum from
400-700 nm (Pitts, IESNA 1994). The radiation in this range, referred to as Photosynthetically Active
Radiation (PAR), can be measured in energy units (watts m-2) or as Photosynthetic Photon Flux Density
(PPFD), which has units of quanta (photons) per unit time per unit surface area. The scaled units most
commonly used are micromoles of quanta per second per square meter (µmol s-1 m-2)
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Relative Response %
RQE Ar Afr Ptr Photopi c Scotopic
Figure 7. Plant and human eye spectral sensitivity functions. Table 2. Plants minimum light Levels
3.2 Photoperiods and the required radiant energy
Light is one of the major maintenance factors in landscape lighting. It supplies energy to plants which
affect the key photo responses that convert light energy into chemical energy. These reactions produce
the conditions that provide the maintenance requirements for plants. There is a correlation between the
light and dark period which affects all plants. Studies show the length of darkness impacts plants more
than the light period. Red light with its peak at 660 nm is the major variable inuencing the photoperiod
response. Light destroys the origen substance that is necessary for induction of owering. The critical
concentration of origen that is needed for short day plants requires long dark period exposure. The
proper light requirements for interior plants or the best photo period is 12 to 16 hours of daylight and
electric light. Preferably 8-12 hours of darkness every 24 hours provides proper chlorophyll development
and function, and produces normal plant response. Based on studies by Tazawa (1996), Hirota (1984)
CIE 27th Session • Sun City/ZA436
Navvab, M. • Lighting Aspects for Plant Growth in Controlled Environments
and Rogers (1996). The following environmental parameters and consideration for plant growth with
respect to Photo Period Density (PPD), Photosynthetic Active Radiation (PAR) and Photosynthetic
Photon Flux Density (PPFD) are recommended (Rogers 1996, Bickford 1973).
1) A minimum PPD of six hours is required; however a PPD of 8-12 hours is more ideal. 2) A minimum
PPD of six hours requires a minimum of 694mmol/m2.s (152-W/m2) to obtain 15mol PAR/day or a
minimum level of 1000 mmol/m2.s (219-W/m2). 3) Plants with low shade factors have a PPFD minimum
requirement of 230 mmol/m2.s (50-W/m2) for 12 hours to obtain 10 mol PAR/day. 4) Plants with high
shade factors have a PPFD minimum requirement of 350 mmol/m2.s (77-W/m2) for 12 hours to obtain
15 mol PAR/day. Plants with low shade factors require less daylight. Note: 100 lux from cool white
uorescent lamp is approximately equal to 1.3mmol/m2.s.
3.3 Carbon Dioxide
Experimental studies show that the carbon dioxide enrichment of the green house atmospheres contribute
to the growth of plants. Typical outdoor air contains 250 to 300 PPM (Part Per Million) carbon dioxide
by volume. The greenhouse has less when it is absorbing the light. Crop growth drops when carbon
dioxide is less than 200, and stops at 125 PPM. Figure 8. shows the carbon dioxide concentration in a
greenhouse while the vents are closed during the winter season. As the daylight enters the space, the
CO2 drops due to the photosynthesis process, and it peaks again as the daylight period ends. The CO2
is too low during the daytime as compared to outside during winter season conditions. The results of
the same studies show the photosynthesis rate increases as a function of CO2 concentration. Levels of
1000 to 1400 PPM should be maintained for best outcomes and utilization of daylight and electric light.
The CO2 is a major factor in total plant growth. In the process of photosynthesis, the water and light
interactions form the carbohydrates and oxygen. Some of the carbohydrate is converted to compounds
that maintain the growth rate of the plants. This process is expressed chemically within the following
equation:
6 CO2(carbon dioxide)+12 H2O(water)+Radiant Energy=C6 H12 O6(carbohydrate)+O6 (oxygen)
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0246810 12 14 16 18 20 22 24
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2
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Green House Air
Outside Air
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Photosyn thesis Rate
1400 PPM
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600 PPM
300 PPM
Figure 8. CO2 Concentration vs. Time. Figure 9. CO2,Light intensity and Photosynthesis Rate.
Figures 10 and 11 show the carbon dioxide concentration and the (PAR) as a function of the rate of
photosynthesis computed based on the Figure 9 data as measured within each climatic conditioned
zones. The results show clear trends and noticeable differences among the conditioned zones,
specically the arid and the tropical zones. The CO2 production associated to various plants types within
each zone provides opportunity for the creation of specication to interior lighting designers as to which
plants provide higher yields in cleaner indoor environments through the plants use of CO2 produced by
occupants of the buildings.
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Navvab, M. • Lighting Aspects for Plant Growth in Controlled Environments
Figure 10. CO2 vs. Photosynthesis Rate Figure 11. PAR vs. Photosynthesis Rate
4 Light Intensity
There are three major effects which must be considered by daylighting designers and utilized at the
beginning of the design process. The factors are: (1) The amount of light and its intensity; (2) The
duration of the exposure; and (3) The spectral characteristics of the daylight. Light intensity levels and
sufcient light levels are important to produce energy reserves in the plant in excess of its respiration
needs. Otherwise respiration will use all of the energy collected in photosynthesis, and plants will
deteriorate and die. It is obvious that the radiant energy for plants and that for human vision overlap given
the spectral characteristic of the natural and electrical light sources used in buildings. The sensitivity
functions of the human eye (photopic and scotopic) and plants’ photosynthesis processes are shown in
Figure 6. The use of lux (lm/m2) or irradiance (w/m2) allows one to quantify the illuminance or irradiance
falling on the surface of plants. The latest luminance scanning system allows one to quantify these
levels in more detail. Figures 12 shows the actual images of an indoor plants for tropical, temperate,
arid zones including the luminance (cd/m2) levels on each plant surface. Most plants identied in the
current literature (IESNA 1994) require illuminance in range of 2500 to 7500 lux given the control system
provided by the lighting system in order to maintain a photoperiod of 14 hours. The use of shades and
lighting control systems allow not only the reduction of these intensities, but also the durations.
Tropical, Temperate, Arid Zones
Figure 12. Full view of daylight including the luminance (cd/m2) levels on each plant surface
The specic movement of a plant’s parts is due to illumination. It is called phototropism. The term,
positive tropism, is used to indicate that the plant bends toward the light source, while negative tropism
indicates that the growth is away from the light source. Sunower heads turn toward the east in the
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Navvab, M. • Lighting Aspects for Plant Growth in Controlled Environments
morning, and toward the west in the evening, following the course of the sun. Phototropic responses
(PTR) are not equal in all parts of the visible spectrum. Some researchers have found that the most
effective wavelengths ranged from 400 to 480 nanometers, which are the violet and blue regions of
the spectrum. See Figure 7. No phototropic effect is produced by the red end of the spectrum. For this
reason, quantitative determinations of auxins (natural hormones) are made in the red light. In the green
region, the phototropic effect is very slight. Phototropism may be manifested under very low intensities.
It should be recalled that the photochemical effect of light on plants equals the product of time and
intensity.
4.1 Plants acclimatization
The typical lighting intensity in an interior space is between 50 and 200 dalux or fc. Some times
illuminance levels are reported in “dekalux” or 10 lux (10.766 lx=fc), which is approximately equivalent
to a 99 %-98 % shade level. The hourly measured illuminance within each climatic conditioned zone
are shown in Figure 13 in units of dalux. The dynamic variations within the zones are due not only
to the outdoor atmospheric conditions but also to the operation schedules of the automatic shading
system to prevent the harsh effect of the high levels of daylight reaching some of the plant with less light
intensity requirements. Some of the interruptions in data collection as shown in these gures are due to
storm impact on the computer network system. Shade level is the term used by shade cloth producers
and interior landscape designers to indicate the percentage of sun light reduction. Commercial shade
cloth is available in the many patterns of wave density for acclimatization of plants. The 47% shade
admits 53% of the sun beam. To acclimatize plant material at the actual installation site is no different
than acclimatizing the same plant under an extremely high shade level. Both approaches will result
in extensive foliage loss to typical leaf-dropping in varieties of plants such as Ficus benjamina and
Brassaia actinophylla and this method will cause the plants to deplete their food reserves in order to
reestablish this lost foliage. If the conditions are maintained in the same low-light environment, these
plants will never be able to regain their depleted food reserves and reestablish the added protection that
these reserves represent. It is highly recommended that plant material not be acclimatized at the actual
installation site unless additional lighting is provided during the adaptation period.
Figure 13. Measured hourly daylight illuminance within each climatic conditioned zone in MBG
4.2 Required illuminance
Illuminance, or the amount of light, is the strongest determinant of success for indoor planting. Sufcient
light to promote growth must reach not only the trees, but also the ground-cover planting below them.
The energy needs of most suitable plants are equivalent to at least the supply of 70 to 100 dalux
or fc for 12 hours per day, with 250 to 750 dalux over a similar period, as the absolute minimum for
survival. In daylighting terms, a daylight factor of 10 to 20 per cent will be needed under the 1500 dalux
or fc standard sky light only (no sun - dark winter days). Since this supply may not be available all
year, supplementary sources must also be provided. These sources should preferably be off at night,
keeping the daily rhythm normal. The way daylight is brought in to indoor space will affect its level and
the growth pattern of plants. Higher sky luminance exists at the zenith of the sky rather than near the
horizon, therefore skylights will deliver two or three times as much light per unit area as vertical glazing.
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Navvab, M. • Lighting Aspects for Plant Growth in Controlled Environments
Light levels for maintaining interior plants are classied in three groups: 1) Low (100 to 150 dalux)
Philodendron, Golden Aglaonema, Corn Plant, 2) Medium(150 to 250 dalux) Asparagus Fern, Green
Dracaena, Rubber Plant,
3) High (250 to 350 dalux or fc.) Norfolk Island Pine, Fan Palm, Podocarous.
4.3 Methods of Calculation and Application
During the winter the daylight is approximately one third of the summer daylight. The position of the
sun is lower in the sky. Cloudy weather is more frequent, and hours of daylight are fewer. Extending the
day length with electric light sources is essential to overcome the deciencies of winter light. Total light
requirements for interior plants: Total light per day is the product of the intensity of light times its duration.
Total light per day = dalux or fc times hours of daylight/day. Example: 200 dalux ´ 12 hrs. = 2400 dalux
or fc / day. At the nursery, better growth conditions usually prevail, and new re-growth can be more easily
stimulated. It should be remembered that once a plant has been acclimatized for lower light conditions,
this condition is not easily reversed. The chlorophyllous structure has by acclimatization been placed
in a highly susceptible, though very functional, state. To subject this exposed structure to high light
intensities can be very dangerous to the plant. Some acclimatized plants can be converted back to full-
sun plants. This must, however, be done in steps of several hundred to a thousand foot-candles at a time,
and the process could take up to six months. Use of lters might be helpful in this process. The fact that
measurements of visible and total radiation from the sky and sun (real or simulated) are typically made
with instruments that integrate radiation at various wavelengths presents some difculties. As discussed
above plants are especially affected by light at wavelengths below 550 nanometers (although the atrium
or retail spaces with skylight or window glazing are specied to exclude wavelengths below 400 nm).
Color-corrected photocells are weighted to be substantially less sensitive to wavelengths near 400 nm
than to those near 550 nm. The use of irradiance meters would provide better accuracy in quantifying
the amount of radiation reaching the plant from lamps of different spectral energy distribution and the
estimation of the efcacy of the mixed lighting systems.
5 Final Remarks
Properly selected plants and strategic location throughout the building could serve as a measuring
system or the so called “Plant as a Meter”. Plants have little control over their own living environment
and do not require “Monkey Survey” to measure their preferences within some statistical scale as to
weather or not they are “somewhat” satised with their living environment. By the time the plant is in the
defoliated stage, it is too late and it indicates the poor status of their environment to the occupants of
the space. The latest results support the use of plants in buildings as a passive LEED commissioning
protocol/procedure to measure the validity of the claims for the designs to be successfully implemented
as integrated lighting design without major cost to the owners, and provides active participation of
the building occupants. Both indoor and outdoor measured results show correlation among selected
variables as a function of time and season. Providing clear direction or recommendation to maintain
a controlled environment in which plants grow is essential. It is important to identify the capabilities
and the limitations of the growth chambers, and not to extrapolate results from a well dened control
environment to eld-growth plants. Generated predictive models provide opportunities to compare the
experimental results to eld measurements. This study reports on the critical environmental conditions
(outside as well as inside) where experimental results could be used for the replication of experiments
and parametric studies within controlled chambers.
The associated results are intended to provide recommendations to researchers for evaluating data
generated from controlled environment experiments. The results from spectral measurements provide
opportunities to examine the interaction of optical radiation with other environmental parameters, and
to identify the limitation of the new and current optical sources used for plant culture. It is important to
recognize that these are guidelines, not rigid rules. The objectives of the experiment and intended use
of the results need to be considered as these guidelines are applied. The major development in new
lighting systems will have a major impact on plant response, and this growing industry has created a
new market in plant production within the commercial building sector. The increased amount of basic
research in this eld of design is contributing to new areas of daylighting application and applied
research as relates to plant growth.
CIE 27th Session • Sun City/ZA440
Navvab, M. • Lighting Aspects for Plant Growth in Controlled Environments
References
BICKFORD, ELWOOD, D., and DUNN, S. Lighting for Plants Growth. The Kent State University Press,
1973, ISBN 0-87338-116-5.
BUSH-BROWN, L. American garden Book, Macmillan Inc.N.Y.,1996. ISBN0-02-860995-6.
HIROTA, H. and SHIOZAWA, K. Inuence of Shading on the Initial Growth of Turf (in Japanese), Turf
Studies, Vol. 1305, No. 1, 1984.
IESNA - Illuminating Engineering Society of North America, IESNA Handbook 1994, NY, 2001.
MPELKAS, C. Horticultural Light Sources, Sylvania Engineering Bulletin O-352, 05/1981.
NAVVAB, M. Daylighting Aspects for Plant Growth in Interior Environments, International Journal of
Light and Engineering, Vol:16, No#4 32-39, 30-04-2009, ISSN 0039-7067,
NAVVAB, M. et al. Solar and daylighting and airow performance of botanical garden, ASES, 2005.
NAVVAB,M.,PRAYHOONANG,C. “Application of the New Standards for the Evaluation of Daylight and
Solar Availability Measurements”, Journal of the Illuminating Engineering Society (August 1995):113-
130.
PITTS D.G., et al. “Environmental Vision”, Bullerworth Heinmann, ISBN0750690518.
ROGERS N.J. et al. The Sport Tutf Management and Research Program at Michigan State University
Safty in American Football, ASTM, STP, Earl Hoemer, Ed., ASTM, 1996, pp. 132-144.
TAZAWA, S. Application of Articial Luminous Source to Growing Plants (in Japanese), Journal of The
Illuminating Engineering Institute of Japan, April 1996.
SLINEY, D.H., MARSHALL, W.J., CAROTHERS, M.L., KASTE, R.C. Hazard Analysis of Broad-band
Optics Sources. Aberdeen Proving Ground, MD. US Army Environmental Hygiene Agency, 1980.
THIMIJAN, R.W. and HEINS, R.D. 1983. Photometric radiometric and quantum light units of measure:
A review of procedures for introversion. Hort Science 18(6):818-822.
Acknowledgment
This project is funded by the Sustainable Design Research Laboratory at UM-TCAUP. Special thanks
to Mike Palmer for his effort providing access to the UM-Botanical Garde. The research collaboration
efforts between the UM_TCAUP http://www.tcaup.umich.edu/ and School of Natural Resources &
Environment http://www.snre.umich.edu/ and support from industry representative “Planterra” http://
www.planterra.com/ U of M, Matthaei Botanical Garden Conservatory (MBG). http://www.lsa.umich.edu/
mbg/plan/hours.asp
... The intensity of light is measured in lux unit (lumens.m-2). Most plants need to light within a range of 2500 -7500 lux to maintain a 14-hour light period (Navvab, 2000;IESNA 1994). The optimum energy needs for plants equals at least 753 to 1077 lux for 12 hours a day (Navvab, 2000). ...
... Most plants need to light within a range of 2500 -7500 lux to maintain a 14-hour light period (Navvab, 2000;IESNA 1994). The optimum energy needs for plants equals at least 753 to 1077 lux for 12 hours a day (Navvab, 2000). The level of 4000 lux is sufficient to equate the rate of photosynthesis with the rate of respiration, while the next level (over 4000 lux), in which increasing light intensity does not lead to increase photosynthesis, is called light saturation. ...
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BICKFORD, ELWOOD, D., and DUNN, S. Lighting for Plants Growth. The Kent State University Press, 1973, ISBN 0-87338-116-5.
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NAVVAB, M. Daylighting Aspects for Plant Growth in Interior Environments, International Journal of Light and Engineering, Vol:16, No#4 32-39, 30-04-2009, ISSN 0039-7067,
Influence of Shading on the Initial Growth of Turf
HIROTA, H. and SHIOZAWA, K. Influence of Shading on the Initial Growth of Turf (in Japanese), Turf Studies, Vol. 1305, No. 1, 1984.
Application of the New Standards for the Evaluation of Daylight and Solar Availability Measurements
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NAVVAB,M.,PRAYHOONANG,C. "Application of the New Standards for the Evaluation of Daylight and Solar Availability Measurements", Journal of the Illuminating Engineering Society (August 1995):113130.
Environmental Vision
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PITTS D.G., et al. "Environmental Vision", Bullerworth Heinmann, ISBN0750690518.