ArticlePDF Available

Light quality management in fruit Orchards: Physiological and technological aspects


Abstract and Figures

Light quality (sunlight spectrum) management promises to provide a new technological alternative to sustainable production in horticultural crops. However, little information exists about physiological and technological aspects on light quality management in fruit crops. Sunlight composition changes widely in orchard canopies, inducing different plant responses in fruit trees mediated by phytochrome (PHY) and cryptochrome (CRY) activity. High proportion of far-red (FR) in relation to red (R) light increases shoot elongation, while blue (B) light induces shoot dwarfng. Red and ultraviolet (UV) light increases fruit skin anthocyanin synthesis, while FR light shows a negative effect. Red and B light can also alter leaf morpho-physiological traits in fruit trees, such palisade thickness, stomatal aperture, and chlorophyll content. Besides improvement of photosynthetically active radiation (PAR) availability, the use of refective flms improves UV and R light proportion, with positive effects on PHY mediated-responses (fruit color, fruit weight, shoot growth), as reported in apple (Malus domestica Borkh.), peach (Prunus persica [L.] Batsch), and sweet cherry (Prunus avium [L.] L.). Colored nets widely alter spectral light composition with effects on plant growth, yield, and quality in apple, kiwifruit (Actinidia deliciosa [A. Chev.] C.F. Liang & A.R. Ferguson), peach, and blueberry (Vaccinium corymbosum L.) orchards. Mechanisms of colored nets seem to be associated to photosynthetic and morphogenetic process regulated by PAR availability, R/B light proportion, and CRY activity. Alteration of light quality affects signifcantly fruit tree plant responses and could be a useful tool for sustainable (e.g. lower use of chemicals and labor-practices) management of yield and quality in modern orchards.
Content may be subject to copyright.
Richard M. Bastías1, 2*, and Luca Corelli-Grappadelli1
Light quality (sunlight spectrum) management promises to provide a new technological alternative to sustainable production
in horticultural crops. However, little information exists about physiological and technological aspects on light quality
management in fruit crops. Sunlight composition changes widely in orchard canopies, inducing different plant responses in
fruit trees mediated by phytochrome (PHY) and cryptochrome (CRY) activity. High proportion of far-red (FR) in relation
to red (R) light increases shoot elongation, while blue (B) light induces shoot dwarng. Red and ultraviolet (UV) light
increases fruit skin anthocyanin synthesis, while FR light shows a negative effect. Red and B light can also alter leaf
morpho-physiological traits in fruit trees, such palisade thickness, stomatal aperture, and chlorophyll content. Besides
improvement of photosynthetically active radiation (PAR) availability, the use of reective lms improves UV and R
light proportion, with positive effects on PHY mediated-responses (fruit color, fruit weight, shoot growth), as reported in
apple (Malus domestica Borkh.), peach (Prunus persica [L.] Batsch), and sweet cherry (Prunus avium [L.] L.). Colored
nets widely alter spectral light composition with effects on plant growth, yield, and quality in apple, kiwifruit (Actinidia
deliciosa [A. Chev.] C.F. Liang & A.R. Ferguson), peach, and blueberry (Vaccinium corymbosum L.) orchards. Mechanisms
of colored nets seem to be associated to photosynthetic and morphogenetic process regulated by PAR availability, R/B light
proportion, and CRY activity. Alteration of light quality affects signicantly fruit tree plant responses and could be a useful
tool for sustainable (e.g. lower use of chemicals and labor-practices) management of yield and quality in modern orchards.
Key words: Red, far-red and blue light, phytochrome, cryptochrome, photo-morphogenesis, reective lms, colored nets.
1Università di Bologna, Dipartimento di Colture Arboree, Viale
Fanin 46, Bologna, Italy.
2Universidad de Concepción, Facultad de Agronomía, Av. Vicente
Méndez 595, Chillán, Chile.
*Corresponding author (
Received: 14 February 2012.
Accepted: 5 July 2012.
he sunlight use efciency (i.e. converting light
energy to dry matter) has long been the main research
focus to obtain sustainable fruit production and quality
in orchard systems. In the recent years, however, more
technological innovation are required for adequate light
management in fruit trees, due to changes of paradigm of
efciency in orchard systems, which must include other
factors, such as climate change, energy cost, and need of
reduction of environmental impact (Palmer, 2011; Blanke,
2011). Optimizing of sunlight use has been achieved
in orchard systems thanks to research development in
cultural practices such as pruning, training system, tree
arrangement, and orchard design, directed toward the
improvement of “quantity of light” (i.e. the amount of
photosynthetically active radiation, PAR) intercepted
and distributed by orchards (Jackson, 1980; Palmer,
1989; Bastías and Widmer, 2002; Corelli-Grappadelli,
2003; Corelli-Grappadelli and Lakso, 2007). However,
alongside the PAR quantity that provide the energy
and carbon needed for sustained tree and fruit growth,
plant growth and development also respond to subtle
changes in the light quality (i.e. spectral composition of
sunlight), processes regulated by specic pigment-based
photoreceptors, including red (R) and far-red (FR) light
absorbing phytochromes (PHY) and ultraviolet (UV)
and blue (B) light absorbing cryptochromes (CRY) and
phototropins (PHO) (Fankhauser and Chory, 1997;
Kasperbahuer, 2000; Smith, 2000; Lin, 2002). More
signicant advances in light quality management have
been achieved in vitro plant culture and greenhouse
systems by using supplemental lighting sources (e.g.
light emitting diodes, LEDs), colored soil mulches and
photo-selective lters to manipulate the plant growth,
yield and quality (Muleo et al., 2001; Oren-Shamir
et al., 2001; Hemming, 2011). Nevertheless, due to
the difculty of conditioning the light environment of
orchards, the management of light quality has been much
less developed in fruit trees grown under eld conditions,
consequently more studied have been developed under
controlled conditions (Erez and Kadman-Zahavi, 1972;
Baraldi et al., 1994; 1998; Rapparini et al., 1999). Since in
recent years, manipulation of plant responses by changes
in the light quality composition promises to provide new
technological alternatives for sustainable manipulation of
growth, yield, and quality of harvest in agricultural and
horticultural crops (Devlin et al., 2007; Rajapakse and
Shahak, 2007), the purpose of this article was to review
the current status on light quality management in fruit trees
under eld conditions, with emphasis in physiological
and technological aspects and its potential application for
manipulation of plant growth, productivity, and quality in
orchard systems.
Light quality relations in orchards
Light quality composition. Sunlight reaching the earth
surface changes its spectral and energetic prole in
part due to the normal climate variability and, in recent
years, because of man-induced causes, such as the loss
of stratospheric ozone that affects UV light absorption,
or atmospheric pollutants and CO2 levels that affects
infrared (IR) light absorption. In general the light spectra
that concerns plant physiologists is between 280 and 800
nm, which includes UV-B (280-320 nm), UV-A/B (300-
400 nm), PAR (400-700 nm), and FR (700-800 nm). The
PAR radiation is subdivided into various bands and the
most important for plant physiological processes are B
(400-500 nm), green (G, 500-600 nm) and R (600-700
nm) light (Nobel, 1983; Grant, 1997; Combes et al.,
2000; Corelli-Grappadelli, 2003). In fruit orchards, the
spectral distribution of solar radiation changes widely
as the light penetrates and scatters within the tree
canopy due to the structure and optical properties of the
canopy components, such as leaves, fruits, and branches
(Palmer, 1977; Baldini et al., 1997). In general, the light
environment inside the tree canopy is made up by two
components: the unltered solar radiation (direct and
diffuse) that has passed through gaps in the vegetation,
and the ltered radiation that has been attenuated by the
optical properties of reectance and transmittance of
the leaves, which have a crucial importance in the light
spectrum modication in fruit trees (Grant, 1997; Baldini
et al., 1997).
In walnut (Juglans regia L.) leaves, values of leaf
reectance and transmittance in the FR spectrum are
estimated to be near 50% and in the G spectrum around
20% for both optical properties (Combes et al., 2000),
while in apple (Malus domestica Borkh.) the reectance
and transmittance values in the G spectrum are 10% and
4%, respectively and in the FR spectrum are near 50%
and 30% (Palmer, 1977). Awad et al. (2001) demonstrated
that under sunny conditions, the inner position of apple
tree canopy reduced 40-48% the UV, B, and G light
proportion, while R light was reduced in 58% and FR
light increased in 33%, which affects markedly the R/FR
ratio. Thus, R/FR ratio reached values of 1.6 at different
outside positions of the tree canopy, but near 0.5 in the
inner canopy (Table 1).
Similarly, in peach tree (Prunus persica [L.] Batsch)
canopies the R/FR ratio decreased with height of the tree
and this effect was more marked with time, until full
canopy development. Early in the season the R/FR values
in the top and bottom of the tree canopy were around 1.1
in both parts, while later, near fruit harvest, they reached
values of 0.5 at the top of canopy and 0.3 at bottom,
almost a 50% of difference (Baraldi et al., 1994).
The role of photoreceptors. The reduction of the R/FR
ratio in the inner regions of the tree canopy may produce
different morphological and physiological responses
mediated by the photoreceptors called phytochromes
(PHY) that are responsible for R and FR light signal
transduction (Fankhauser and Chory, 1997; Smith,
2000; Devlin et al., 2007). Phytochrome possesses the
capacity of detecting wavelengths from 300 to 800 nm
with maximum sensitivity in the R (600-700 nm) and
FR (700-800 nm) wavelengths. Phytochrome activity
can be changing continuously through the two inter-
convertible states that naturally occur: R absorbing (Pr)
and FR absorbing (Pfr) forms, which absorb maximally
near 660 and 730 nm, respectively (Sager et al., 1988;
Rajapakse and Kelly, 1994; Smith, 2000). Because the
inner tree canopy has light rich in FR photons (Palmer,
1977; Baraldi et al., 1994; Combes et al., 2000; Awad
et al., 2001), the majority of the PHY pool is converted
to the inactive Pr form, with loss of the active Pfr form.
To estimate the PHY pool mediated responses, the R/
FR ratio has been commonly used. However, most
plant physiologists consider that the R/FR ratio does
not accurately explain PHY-mediated plant responses
and therefore mathematical models using spectral
light information have been proposed to estimate the
PHY photoequilibrium (Φc): the equilibrium state of
biologically active Pfr form in relation to total PHY
(Pfr/Ptotal) (Sager et al., 1988; Rajapakse and Kelly,
1994; Kasperbahuer, 2000; Smith, 2000). Different
reports demonstrate that Φc provides a better indicator
of expected photomorphogenic responses to a specic
spectral light quality in orchard canopies (Baraldi et al.,
1994; 1998; Rapparini et al., 1999; Combes et al., 2000).
In walnut orchards, the curve that relates the R/FR ratio
with Φc have shown a hyperbolic relationship between
both components from the top to the inner canopy, with
marked variations of R/FR ratio (from 0.3-1.2) and less
important variations in Φc (from 0.35-0.68), thus Φc
is especially sensitive to R/FR changes in the range of
0.2-0.7 (shade conditions), but insensitive indeed to R/
Top 5.6 7.9 16.3 18.7 11.6 1.6
2.9 4.1 9.5 7.9 15.4 0.5
Inner (-48%) (-48%) (-41%) (-58%) (+33%) (-68%)
Outer east 5.2 7.4 16.0 19.0 11.7 1.6
Outer west 5.9 8.0 15.9 17.8 11.4 1.6
F-test *** *** ** *** *** ***
Adapted from Awad et al., 2001; **p < 0.01; ***p < 0.001.
UV Blue Green Red
Table 1. Spectral composition of the sunlight at different canopy positions
in apple orchards.
Spectral composition (% of total available light)
of tree
FR above about 1.0 (Combes et al., 2000). Although
PHY detects not only R and FR but also B and UV light,
current research indicates the presence in the most plants
of specic photoreceptors for the B and UV regions,
denominated crypthocromes (CRY) and phototropins
(PHO) (Lin, 2002; Devlin et al., 2007). In peach trees,
it has been shown that beside the effect of PHY on plant
growth, the CRY is also involved either independently
or in conjunction with PHY (Erez and Kadman-Zahavi,
1972; Baraldi et al., 1998; Rapparini et al., 1999).
Plant responses to light quality in fruit trees
Growth and development. Under high relative
proportions of FR light the Φc is shifted toward the inactive
Pr form. In these conditions, fruit trees exhibit different
morphological changes, probably associated to “shade-
avoidance” strategies evoked by decreasing Pfr form,
such as shoot elongation, increased apical dominance and
reduced leaf thickness (Baraldi et al., 1994; Combes et
al., 2000). Indeed for many trees the elongation rate of the
shoots has an inverse relationship with the Φc (Pfr/Ptotal)
(Gilbert et al., 2001). In a classic study, Erez and Kadman-
Zahavi (1972) demonstrated that apical growth activity of
peach plants was strongly affected by changes in the Φc
in Pfr form, but also demonstrated that B light are quite
important role in these responses. These observations
were conrmed more later, when, still in peach, was
demonstrated that prolonged irradiation with B photons
induced an inhibitory effect on shoot elongation, and the
morphological responses to B light were widely modied
and enhanced the inhibitory effect on stem elongation
under lower level of Φc, providing the evidence of the
interaction of PHY and CRY in the regulation of shoot
growth in fruit trees (Baraldi et al., 1998; Rapparini et
al., 1999).
The role of light quality conditions, specically
R and FR light, on growth partitioning among fruit
and shoots has been also suggested. In horticultural
crops, long-term FR light exposure initiates events that
result in more carbohydrates being partitioned to stems
and less to leaves and roots as compared to plants that
received R light, affecting the allocation to developing
fruits (Kasperbahuer, 2000; Glenn and Puterka, 2007).
In apple trees, have been underlined the essential role
of light quantity on carbohydrate partitioning patterns
(Tustin et al., 1992; Corelli-Grappadelli et al., 1994;
Corelli-Grappadelli, 2003), but the effects of light quality
conditions in these patterns are not totally studied in fruit
Dormancy. Different physiological studies indicate that
perception of photoperiod is related to levels of PHY,
which apparently interact with biosynthesis of plant
hormones during control of dormancy-related processes
in fruit trees (Olsen, 2006). However, the role of PHY
and photoperiod on dormancy release has not been totally
understood in fruit trees. In general, it has been postulated
that in a short day FR light is dominant, decreasing the
bud meristematic activity, while in a long day, R light is
dominant and has the opposite effect (Erez and Kadman-
Zahavi, 1972). Previous reports in peach demonstrated that
limitation of illumination affected bursting of vegetative
buds when it occurred shortly before sprouting. In general
R light is more active on bud break and its effects on buds
are reversed by a subsequent FR illumination (Erez et al.,
1968). Baraldi et al. (1994) proposed in apple and peach
that ower bud differentiation can be modulated by R/
FR ratio. However, the spectral light composition has no
effect on ower bud burst or ower bud differentiation, as
was demonstrated by Erez et al. (1966) and Baraldi et al.
(1998). Probably the relationship between PHY system,
photoperiod and dormancy depends also on genetic
factors. For example, photoperiod has no effect on growth
cessation and dormancy induction in apple and pear,
but a partial effect in Prunus species, such as peach and
sweet cherry (Prunus avium [L.] L.), where a pronounced
interaction of photoperiod and temperature exists on the
regulation of growth cessation (Heide and Prestrud, 2005;
Heide, 2008).
Leaf morphology and function. Many authors have
shown the close relationship between orchard light
conditions and morphological and physiological traits.
Thus, in fruit species such as peach (Nii and Kuroiwa,
1988), olive (Olea europaea L.) (Gregoriou et al., 2007),
and apple (Tustin et al., 1992; Corelli-Grappadelli et
al., 1994); sun leaves presented more leaf mass per
area ratio, stoma density and palisade cell thickness
compared to shade leaves. Although anatomical
differences of sun and shade leaves can be attributed to
light intensity changes, the role of light quality has been
also postulated (Kim et al., 2005). Examination of peach
leaf expansion showed that the combination of B + FR
light reduced signicantly leaf area and the thickness
of top and mesophyll palisade layers compared to R +
FR light combination. In addition, leaves exposed to R
+ FR light presented greater thickness of the palisade
mesophyll (Table 2) (Baraldi et al., 1998).
The Φc values demonstrated that, opposite to the
argument that indicates that low Φc generally increases
leaf expansion, in this case leaf expansion was reduced
cm2 %
Transparent 0.57 31.3a 28.8a 67.0a 61b
R/FR 0.49 33.2a 23.5b 46.2b 59b
BL/FR 0.13 24.3b 20.9c 38.5c 67a
Neutral 0.57 33.9a 20.5c 34.0d 67a
Adapted from Baraldi et al., 1998; Φc: phytochrome photoequilibrium.
Table 2. Effect of different light spectrum conditions on leaf peach
Thickness (µm)
Top layer
under lower Φc (Table 2). This behavior was conrmed
in further experiments, concluding that probably the
inhibitory effects of B + FR light on leaf expansion and
thickness are controlled by a specic CRY independent of
the PHY system (Rapparini et al., 1999). Changes in leaf
chlorophyll content were also detected under different
light quality conditions in citrus trees: plants under
nets with more B light proportion had the greatest leaf
chlorophyll a, b and total chlorophyll content, compared
to those with more R light proportion (Li and Syvertsen,
2006). In apple trees, leaf chlorophyll synthesis under
nets with more R and G light transmission was up to
46% highest (Solomakhin and Blanke, 2008). Recent
studies demonstrated prolonged exposition of apple
leaves under nets with more light transmission in the B
spectra increased the leaf stomatal conductance and leaf
transpiration (Bastías et al., 2011), probably by direct
effect of B light on stimulation of stomatal opening has
been previously reported (Farquhar and Sharkey, 1982;
Shimazaki et al., 2007).
Fruit color development. Fruit skin color depends
on the concentration of various pigments, such as
anthocyanins, chlorophylls, and carotenoids, but red
color is due to anthocyanin pigments, mainly cyanidin
3-galactoside (Ju et al., 1999; Awad et al., 2001;
Layne, 2001). Anthocyanin biosynthesis is another
important light-depending process and has been widely
used as a model to study the effect of light quality in
vegetative tissues, while its formation is controlled by
a high-energy photoreaction and has a photo-protective
function to excess light (Mancinelli, 1985; Arakawa et
al., 1985; Arakawa, 1988; Steyn et al., 2002). Different
experiments demonstrated that simultaneous irradiation
with white and UV-B light stimulated anthocyanin
production synergistically in apple fruits. Although the
effectiveness of R light was lower than that of UV-B, it
produces a synergistic effect when given simultaneously
with UV-B. Furthermore, long-term treatment with R and
FR light showed a signicant R-FR reversible response
of photo-regulation of anthocyanin synthesis in apple
skin, indicating a possible role of PHY system and that
FR light could possibly even inhibit color development.
This was conrmed under eld conditions, where at low
light levels and above a critical FR/R ratio (~ 1), there
was no anthocyanin formation in apple fruits (Arakawa
et al., 1985; Arakawa, 1988; Awad et al., 2001).
Manipulation of light quality in orchard systems
Light reection management. The use of reective
ground cover materials such as white woven plastics and
aluminum foil is a good approach for improvement the
light use in orchard systems (Ju et al., 1999; Widmer et al.,
2001; Layne, 2001; Whiting et al., 2008), while have also
become tested with other reective material such as straw,
lime, and biodegradable white paint in organic orchards
(Blanke, 2007). Cover orchard oor with reective
materials produces important effects on improving of fruit
color, fruit size, and return bloom in apple orchard (Ju et
al., 1999; Widmer et al., 2001; Blanke, 2011), as well on
better fruit rmness, sugar content, advanced in maturity
and source:sink relationships in peach and sweet cherry
(Layne, 2001; Whiting et al., 2008).
The main effect of reective lm is the increases
of PAR reection by reecting light incoming to oor
back into the tree canopy, improving widely the light
availability to shading parts of the tree canopy (Widmer
et al., 2001), as well helping to overcome the light
deciency generated in protected fruit orchards under
hail nets or under shade nets (Blanke, 2011). In orchard
with traditional grass ground cover, the PAR reected is
almost 5-10%, while with reective ground covers PAR
reection incoming reached up to 30-40% (Widmer
et al., 2001; Layne, 2001; Glenn and Puterka, 2007;
Blanke, 2007; Figure 1). Although, positive effects
of reective lms on fruit quality and productivity
are attributed to improving the PAR use for net C
assimilation (Whiting et al., 2008), the role of light
quality conditions have been also proposed (Ju et al.,
1999; Layne, 2001). It was demonstrated that reective
lms increases signicantly the UV light component
of sunlight. Indeed different reports have shown that
reection of UV light by reective lms was up to
80% of light incoming to orchard oor (Ju et al., 1999;
Blanke, 2007; Figure 1).
A greater UV light reection was associated
with increased of UDP-galactose:avonoid-3-o-
glucosyltransferase (UFGalT), the most important
enzyme in the anthocyanin synthesis pathway, but
changes in carbohydrate assimilation were not observed
(Ju et al., 1999). Reective lms also increases R light
component to inner parts of canopy, which affects
largely the R/FR ratio (Figures 1). Data taken from
different reports have shown that R/FR calculated in
apple and peach orchards with reective ground lms
was up two fold greater than grass (Layne, 2001; Glenn
and Puterka, 2007). The combined effect of reective
Figure 1. Quantitative values of photosynthetically active radiation (PAR),
ultraviolet (UV) and red/far-red (R/FR) light proportion in fruit orchards
with grass (A) and reective ground covers (B) (data taken from Ju et al.,
1999; Widmer et al., 2001; Layne, 2001; Glenn and Puterka, 2007; and
Blanke, 2007).
lms on increases of UV and R light proportion should
be stimulating by synergistic effect the anthocyanin
synthesis (Arakawa et al., 1985; Arakawa, 1988) and
can explain the better color development in fruits grown
with reective lms (Layne, 2001; Widmer et al., 2001;
Blanke, 2007), whereas the large R/FR ratio can explain
the enhanced the fruit weight, associated probably
to the PHY mediated process affecting the dry matter
partitioning to developing fruit (Glenn and Puterka,
Light spectrum management. Recently a new approach
has been developed for manipulation of light quality in
orchard systems, based on plastic photo-selective colored
nets with special optical properties (Shahak et al., 2004).
Depending on type of color, photo-selective nets alter
widely the spectral light composition (Figure 2). In
general white and/or black nets are wavelength neutral and
reduced by the same amount full sunlight over the entire
range. In contrast, the red and blue nets altered widely
the spectral light distribution. Red net increased the light
transmission in R and FR spectra (600-800 nm), while the
blue net enhanced the proportion of B light (400-500 nm)
and reduced the R light proportion (600-700 nm) (Oren-
Shamir et al., 2001; Shahak et al., 2004; Solomakhin and
Blanke, 2008; Bastías et al., 2011; Lobos et al., 2012).
Horticultural effects of colored nets have been recently
evaluated in fruit orchards. In apple orchards, red net
improved fruit size compared to black net (Shahak et
al., 2008). Solomakhin and Blanke (2008) also reported
increased apple fruit size under colored nets, but without
effect on yield. In peach, fruit grown under red nets were
rmer, sweeter and fruit size was also improved (Shahak
et al., 2008), while in highbush blueberries (Vaccinium
corymbosum L.), red and white nets increased the number
of fruits and yield per plant in comparison with traditional
black net (Retamales et al., 2008; Lobos et al., 2012).
Although the use of colored nets is already taking hold
among fruit growers, physiological mechanisms involved
in this technology are still not totally understood. Possible
explanations have been attributed to the effect of light
conditions on leaf gas exchange process (Shahak et al.,
2004). The most important effect of colored nets is on
reduction of PAR availability. Moderate shading, as was
demonstrated in citrus and apple trees, would reduce plant
radiation, heat and water stress, increase gas exchange
and availability of carbohydrates for fruit and tree growth
(Jifon and Syvertsen, 2003; Corelli-Grappadelli and
Lakso, 2007).
The question is: Why does color of nets affect
differentially vegetative and fruit growth? Colored nets
altered gas exchange and morphological aspects in
blueberries, but the effect was more linked to reduction
of radiation load (PAR quantity), while light quality
conditions under colored nets had a weaker effect on leaf
gas exchange and morphological characteristics (Lobos et
al., 2012). However, changes in leaf chlorophyll content
were detected by effect of spectral light composition
under colored nets in citrus trees: plants under blue nets
had the greatest leaf chlorophyll a, b, and total chlorophyll
content, whereas leaves under red nets had the lowest (Li
and Syvertsen, 2006). Solomakhin and Blanke (2008)
also demonstrated that apple leaf chlorophyll synthesis
under red and green nets was increased, but this did not
affect leaf photosynthesis capacity.
Later, also in apple, was demonstrated that irrespective
of PAR intensity, blue net was more effective than red net
to increase leaf net CO2 assimilation and transpiration
(Bastías et al., 2011). From the photo-morphogenetic point
of view, the PHY and CRY action could be also involved
(Rajapakse and Shahak, 2007). Solomakhin and Blanke
(2008) underlined the possible role PHY on vegetative
growth and development of apple trees grown under
colored nets, but the R/FR ratio (principal component
of PHY activity) does not change widely among colored
nets. More clear differences have been found in the R/B
ratio among blue and other net colors (Oren-Shamir et al.,
2001; Shahak et al., 2004; Bastías et al., 2011).
In kiwifruit (Actinidia deliciosa [A. Chev.] C.F. Liang
& A.R. Ferguson), blue nets reduced signicantly the
vigor of vines, whereas the red net appeared to stimulate
vigor (Basile et al., 2008), while apple trees grown under
red net presented greater shoot length in comparison to
those grown under full sunlight and neutral white net
(Figure 3). Intensity of PAR and R/FR ratio did not
differ among red and white nets (Figures 3A and 3B);
however, the B/R ratio under red net was 5-10% lower
than white and full sunlight conditions, respectively
(Figures 3C). Since changes in B/R ratio are associated
to CRY photoreceptor regulating shoot dwarng and/or
elongation (Baraldi et al., 1998; Rapparini et al., 1999;
Cummings et al., 2008), management of B and R light
proportions by colored nets could be an interesting tool
to manipulate the vegetative growth and development in
fruit orchards.
Figure 2. Spectral irradiance (visible plus near-infrared) pattern of full
sunlight and different colored nets (Adapted from Bastías et al., 2011).
Orchard canopies present marked changes on light
quality conditions and mainly in the R/FR ratio and PHY
mediated plant responses.
Shoot growth and fruit color development are the most
clearly plant response regulated by light quality conditions
in fruit trees. Changes in the proportion in B, R, and FR
light alter the pattern of shoot growth and anthocyanin
synthesis, mediated by the interaction of PHY and CRY
photoreceptors. However, the effect of light quality on
leaf morphological and functional characteristics should
be studied with more attention in further research.
Light quality manipulation could be achieved by
reective lms and colored nets in orchard systems.
Although the positive effects of this technology are
normally associated to improving the PAR use for net
C assimilation, different reports demonstrated that,
irrespective PAR availability, reective lms and colored
nets alter widely the light quality composition in the UV,
B, and R light with ensuing effects on PHY and CRY
plant mediated responses such as shoot growth, color
development, and fruit growth.
On summary, alteration of light quality makes signicant
differences in fruit trees and could be a useful tool for
sustainable (e.g. lower use of chemicals and labor-practices)
manipulation of yield and quality in orchards. Since novel
technologies such as reective lms and colored nets, which
are already taking hold among fruit growers, alters widely the
light quality conditions; more research and knowledge will
be necessary in the future about interactions of plant and light
quality under orchard systems.
We thank to colleagues from the Department of Fruit Tree
and Woody Plant Science (University of Bologna) and
the National Research Council (CNR, Bologna, Italy),
including Drs. Pasquale Losciale, Federica Rossi and
Osvaldo Facini for the helpful contributions during the
elaboration of the present manuscript.
Manejo de la calidad de la luz en huertos frutales:
Aspectos siológicos y tecnológicos. El manejo de la
calidad de la luz (espectro de la luz solar) promete proveer
una nueva alternativa tecnológica para la producción
sostenible de cultivos hortícolas. Sin embargo, existe poca
información acerca de aspectos siológicos y tecnológicos
sobre el manejo de la calidad de la luz en cultivos frutales.
La composición de luz solar cambia ampliamente en la
canopia de los huertos, induciendo diferentes respuestas en
la planta mediadas por la actividad del tocromo (PHY) y
criptocromo (CRY). Una alta proporción de luz roja-lejana
(FR) en relación a la roja (R), incrementa la elongación de
brotes, mientras que la luz azul (B) induce un acortamiento
de brotes. La luz R y ultravioleta (UV) incrementan la
síntesis de antocianinas en la piel de los frutos, mientras que
la luz FR muestra un efecto negativo. La luz R y B también
pueden alterar caracteres morfo-siológicos de la hoja en
árboles frutales, tales como grosor de la palizada, apertura
estomática y contenido de clorola. Además de mejorar la
disponibilidad de la luz fotosintéticamente activa (PAR), el
uso de lm reectantes mejora la proporción de luz UV y R,
con efectos positivos sobre respuestas mediadas por el PHY
(color de fruto, peso de fruto y crecimiento de brotes), como
se reportó en manzano (Malus domestica Borkh.), duraznero
(Prunus persica [L.] Batsch) y cerezo (Prunus avium [L.]
L.). Las mallas de color alteran ampliamente la composición
espectral de la luz con efectos sobre el crecimiento de planta,
rendimiento y calidad en huertos de manzano, duraznero,
kiwi (Actinidia deliciosa [A. Chev.] C.F. Liang & A.R.
Ferguson) y arándano (Vaccinium corymbosum L.). Los
mecanismos de las mallas de color parecen estar asociados
a procesos fotosintéticos y morfogenéticos regulados
por la disponibilidad de PAR, la proporción de luz B/R,
y actividad del CRY. La alteración de la calidad de la luz
afecta signicantemente respuestas de la planta en árboles
frutales y podría ser una herramienta útil para el manejo
sostenible (ej. bajo uso de químicos y prácticas laboriosas)
del rendimiento y calidad en huertos modernos.
Palabras clave: luz roja, roja lejana y azul, tocromo,
criptocromo, foto-morfogénesis, lm reectantes, mallas
de color.
Figure 3. Mean shoot length (A); photosynthetic photon ux density, PPFD (B); and red/far-red (R/FR), and blue/red (B/R) light proportions (C); estimated
in ‘Fuji’ apple trees grown under full sunlight and red and white nets (Bastías et al., unpublished data).
Arakawa, O. 1988. Photoregulation of anthocyanin synthesis in
apple fruit under UV-B and red light. Plant Cell Physiology
Arakawa, O., Y. Hori, and R. Ogata. 1985. Relative effectiveness
and interaction of ultraviolet-B, red and blue light in anthocyanin
synthesis of apple fruit. Physiologia Plantarum 64:323-327.
Awad, M., P. Wagenmakers, and A. Jager. 2001. Effect of light on
avonoid and chlorogenic acid levels in the skin of ‘Jonagold’
apples. Scientia Horticulturae 88:289-298.
Baldini, E., O. Facini, F. Nerozzi, F. Rossi, and A. Rotondi. 1997.
Leaf characteristics and optical properties of different woody
species. Trees-Structure and Function 12:73-81.
Baraldi, R., F. Rapparini, A. Rotondi, and G. Bertazza. 1998. Effects
of simulated light environments on growth and leaf morphology of
peach plants. Journal of Horticultural Science and Biotechnology
Baraldi, R., F. Rossi, O. Facini, F. Fasolo, A. Rotondi, M. Magli, and
F. Nerozzi. 1994. Light environment, growth and morphogenesis
in a peach tree canopy. Physiologia Plantarum 91:339-345.
Basile, B., R. Romano, M. Giaccone, E. Barlotti, V. Colonna, C.
Cirillo, et al. 2008. Use of photo-selective nets for hail protection
of kiwifruit in Southern Italy. Acta Horticulturae 770:185-192.
Bastías, R.M., P. Losciale, C. Chieco, F. Rossi, and L. Corelli-
Grappadelli. 2011. Physiological aspects affected by photoselective
nets in apples: Preliminary studies. Acta Horticulturae 907:217-
Bastías, R., and A. Widmer. 2002. Blattächenindex und
lichtaufnahme in verschiedenen Apfel-Anbauformen.
Schweizerischen Zeitschrift für Obst- und Weinbau 4:66-69.
Blanke, M. 2007. Alternatives to reective mulch cloth (Extenday
®)? Scientia Horticulturae 116:223-226.
Blanke, M. 2011. Managing open eld production of perennial
horticultural crops with technological innovations. Acta
Horticulturae 916:121-128.
Combes, D., H. Sinoquet, and C. Varlet-Grancher. 2000. Preliminary
measurement and simulation of the spatial distribution of the
Morphogenetically Active Radiation (MAR) within an isolated
tree canopy. Annals of Forest Science 57:497-511.
Corelli-Grappadelli, L. 2003. Light relations. p. 195-216. In Ferree,
D.C., and I.J. Warrington (eds.) Apples: Botany, production and
uses. CAB International, Wallington, Oxford, UK.
Corelli-Grappadelli, L., and A.N. Lakso. 2007. Is maximizing orchard
light interception always the best choice? Acta Horticulturae
Corelli-Grappadelli, L., A.N. Lakso, and J.A. Flore. 1994. Early
season pattern of carbohydrate partitioning in exposed and shaded
apple branches. Journal of the American Society for Horticultural
Science 119:596-603.
Cummings, I., E. Foo, J.L. Weller, J.B. Reid, and A. Koutoulis. 2008.
Blue and red photoselective shadecloths modify pea height through
altered blue irradiance perceived by the cry1 photoreceptor.
Journal of Horticultural Science and Biotechnology 83:663-667.
Devlin, P., J. Christie, and M. Terry. 2007. Many hands make light
work. Journal of Experimental Botany 58:3071-3077.
Erez, A., and A. Kadman-Zahavi. 1972. Growth of peach plants
under different ltered sunlight conditions. Physiologia Plantarum
Erez, A., S. Lavee, and R.M. Samish. 1968. The effect of limitation
in light during the rest period on leaf bud break of the peach
(Prunus persica). Physiologia Plantarum 21:759-764.
Erez, A., R.M. Samissi, and S. Lavee. 1966. The role of light in leaf
and ower bud break of the peach (Prunus persica). Physiologia
Plantarum 19:650-659.
Fankhauser, Ch., and J. Chory. 1997. Light control of plant
development. Annual Review of Cell and Developmental Biology
Farquhar, G.D., and T.D. Sharkey. 1982. Stomatal conductance and
photosynthesis. Annual Review of Plant Physiology 33:317-345.
Gilbert, I.R., P.G. Jarvis, and H. Smith. 2001. Proximity signal and
shade avoidance differences between early and late successional
trees. Nature 411:792-794.
Glenn, D.M., and G.J. Puterka. 2007. The use of plastic lms and
sprayable reective particle lms to increase light penetration in
apple canopies and improved apple color and weight. HortScience
Grant, R.H. 1997. Partitioning of biologically active radiation in
plant canopies. International Journal of Biometeorology 40:26-
Gregoriou, K., K. Pontikis, and S. Vemmos. 2007. Effects of
reduced irradiance on leaf morphology, photosynthetic capacity,
and fruit yield in olive (Olea europaea L.) Photosynthetica
Heide, O. 2008. Interaction of photoperiod and temperature in the
control of growth and dormancy of Prunus species. Scientia
Horticulturae 115:309-314.
Heide, O., and A. Prestrud. 2005. Low temperature, but not
photoperiod, controls growth cessation and dormancy induction
and release in apple and pear. Tree Physiology 25:109-114.
Hemming, S. 2011. Use of natural and articial light in horticulture
interaction of plant and technology. Acta Horticulturae 907:25-36.
Jackson, J.E. 1980. Light interception and utilization by orchard
systems. Horticultural Reviews 2:208-267.
Jifon, J.L., and J.P. Syvertsen. 2003. Moderate shade can increases
net gas exchange and reduce photo inhibition in citrus leaves. Tree
physiology 23:119-127.
Ju, A., Y. Duan, and Zh. Ju. 1999. Effects of covering the orchard
oor with reecting lms on pigment accumulation and fruit
coloration in ‘Fuji’ apples. Scientia Horticulturae 82:47-56.
Kasperbahuer, M.J. 2000. Phytochrome in crop production. p. 407-
434. In R.E. Wilkinson (ed.) Plant-Environment interactions.
Marcel Dekker, New York, USA.
Kim, G-T., S. Yano, T. Kozuka, and H. Tsukaya. 2005.
Photomorphogenesis of leaves: shade avoidance and
differentiation of sun and shade leaves. Photochemical and
Photobiological Science 4:770-774.
Layne, D. 2001. Tree fruit reective lm improves red skin coloration
and advances maturity in peach. HortTechnology 11:234-242.
Li, K-T., and J. Syvertsen. 2006. Young tree growth and leaf function
of citrus seedlings under colored shade netting. HorstScience
Lin, Ch. 2002. Blue light receptors and signal transduction. Plant
Cell 14:S207-S225.
Lobos, G., J.B. Retamales, J. Hancock, J.A. Flore, N. Cobo, and A.
Del Pozo. 2012. Spectral irradiance, gas exchange characteristics
and leaf traits of Vaccinium corymbosum L. ‘Elliot’ grown under
photoselective nets. Environmental and Experimental Botany
Mancinelli, A. 1985. Light-dependent anthocyanin synthesis: A
model system for the study of plant photomorphogenesis. The
Botanical Review 51:107-157.
Muleo, R., S. Morini, and S. Casano. 2001. Photoregulation of
growth and branching of plum shoots: Physiological action of
two photosystems. In Vitro Cellular and Developmental Biology
- Plant 37:609-607.
Nii, N., and T. Kuroiwa. 1988. Anatomical changes including
chloroplast structure in peach leaves under different light
conditions. Journal of Horticultural Science 63:37-45.
Nobel, P.S. 1983. Biophysical plant physiology and ecology. 608 p.
W.H. Freeman, New York, USA.
Olsen, J.E. 2006. Mechanism of dormancy regulation. Acta
Horticulturae 727:157-165.
Oren-Shamir, M., E. Gussakovsky, E. Shpiegel, A. Nissim-Levi, K.
Ratner, R. Ovadia, et al. 2001. Coloured shade nets can improve
the yield and quality of green decorative branches of Pittosporum
variegatum. Journal of Horticultural Science and Biotechnology
Palmer, J.W. 1977. Light transmittance by apple leaves and canopies.
Journal of Applied Ecology 14:505-513.
Palmer, J.W. 1989. Canopy manipulation for optimum utilization of
light. p. 245-262. In C.J. Wright (ed.) Manipulation of fruiting.
Butherworths, London, UK.
Palmer, J.W. 2011. Changing concept of efciency in orchard
systems. Acta Horticulturae 903:41-50.
Rajapakse, N.C., and J.W. Kelly. 1994. Problems of reporting spectral
quality and interpreting phytochrome-mediated responses.
HortScience 29:1404-1407.
Rajapakse, N.C., and Y. Shahak. 2007. Light quality manipulation
by horticulture industry. p. 290-312. In Whitelam, G., and
K. Halliday (eds.) Light and plant development. Blackwell
Publishing, London, UK.
Rapparini, F., A. Rotondi, and R. Baraldi. 1999. Blue light regulation
of the growth of Prunus persica plants in a long term experiment:
morphological and histological observations. Trees-Structure and
Function 14:169-176.
Retamales, J.B., J.M. Montecino, G.B. Lobos, and L.A. Rojas. 2008.
Colored shading nets increase yields and protability in highbush
blueberries. Acta Horticulturae 770:193-197.
Sager, J.C., W.O. Smith, J.L. Edwards, and K.L. Cyr. 1988.
Photosynthetic efciency and phytochrome photoequilibria
determination using spectral data. Transactions of the American
Society of Agricultural Engineers 31:1883-1889.
Shahak, Y., E. Gussakovsky, Y. Cohen, S. Lurie, R. Stern, S. Kr,
et al. 2004. ColorNets: A new approach for light manipulation in
fruit trees. Acta Horticulturae 636:609-616.
Shahak, Y., K. Ratner, Y. Giller, N. Zur, E. Or, E. Gussakovsky, et
al. 2008. Improving solar energy utilization, productivity and fruit
quality in orchards and vineyeards by photoselective netting. Acta
Horticulturae 772:65-72.
Shimazaki, K-I., M. Doi, S. Assman, and T. Kinoshita. 2007. Light
regulation of stomatal movement. Annual Review of Plant
Biology 58:219-247.
Smith, H. 2000. Phytochromes and light signal perception by plants
– an emerging synthesis. Nature 407:585-591.
Steyn, W.J., S.J. Wand, D.M. Holcroft, and G. Jacobs. 2002.
Anthocyanin in vegetative tissues: A proposed unied function in
photoprotection. New Phytologist 155:349-361.
Solomakhin, A., and M. Blanke. 2008. Coloured hailnets alter light
transmission, spectra and phytochrome, as well as vegetative
growth, leaf chlorophyll and photosynthesis and reduce ower
induction of apple. Plant Growth Regulation 56:211-218.
Tustin, S., L. Corelli-Grapadelli, and G. Ravaglia. 1992. Effect of
previous-season and current light environments on early-season
spur development and assimilate translocation in ‘Golden
Delicious’ apple. Journal of Horticultural Science 67:351-360.
Whiting, M.D., C. Rodríguez, and J. Toye. 2008. Preliminary testing
of reective ground cover: Sweet cherry growth, yield and fruit
quality. Acta Horticulturae 795:557-560.
Widmer, A., W. Stadler, und C. Krebs, 2001. Bessere Fruchtqualität
mit weisser, lichtreektierender Bondenfolie? Schweizerischen
Zeitschrift für Obst- und Weinbau 17:470-473.
... Mechanisms of colored nets seem to be associated to photosynthetic and morphogenetic process regulated by PAR availability, R/B light proportion, and cryptochrome activity. Modification of light quality affects significantly plant responses and could be a useful tool for sustainable management of yield and quality in orchards [34]. AbbasniaZare et al. [35] stated that the Croton and Aglaonema plants shaded by the yellow net produced the most number of leaves, whereas the non-shaded plants produced the lowest number. ...
... 'Selva' [37]. The combination of B + FR light can reduce significantly leaf morphology and function compared to R + FR light combination [34]. ...
... Flower bud differentiation can be modulated by R/ FR ratio. However, the spectral light composition has no effect on flower bud burst or flower bud differentiation [34]. Although both red and yellow nets could increase the vegetative growth of cut flowers, they may differ in influencing the time required for flowering. ...
BACKGROUND: The strawberry is an important commercial crop, the improvement of its yield and quality is an imperative task. OBJECTIVE: The present research aimed to study the effect of colored netting and foliar application of amino acids on the physiological characteristics of strawberries subjected to different irrigation intervals. METHODS: The study was carried out as a factorial experiment based on a randomized complete block design with three factors including colored net at 4 levels (no netting, green, red, and yellow netting), organic acids at 4 levels (control, humic acid, glutamine, and arginine), and three levels of irrigation intervals (2, 4, and 6 days) in the greenhouse of Lahijan Agricultural Research Station, Iran. RESULTS: The results showed that the highest leaf number, shoot weight, chlorophyll and carotenoid content were related to yellow netting. The highest fruit yield, anthocyanins, and flavonoids were observed in the treatments of no-netting, green netting, and red netting, respectively. Data for the effect of organic acids showed that the glutamine-treated plants exhibited the highest yield, the humic acid-treated plants displayed the highest anthocyanin and carotenoid content, and the arginine-treated plants demonstrated the highest vitamin C content. The irrigation interval of 6 days caused to the lowest leaf number, flower and fruit number, shoot weight, fruit yield, and carotenoid content. Data for the trilateral effect of ‘netting×organic acid×irrigation’ showed that the highest flower number and fruit yield were obtained from ‘green netting×glutamine×4 days’, the highest anthocyanin content was obtained from ‘green netting×humic acid×2 days’, and the highest chlorophyll content was obtained from ‘green netting×control×6 days’. The treatment of ‘yellow netting×control×2 days’ was related to the highest flavonoid content. CONCLUSIONS: The application of colored nets provides the strawberry with more optimal vegetative and reproductive growth.
... Apple tree cultivars have all been selected and studied under optimal conditions, and their acclimation to different degrees of shade has mainly been studied under shade nets (Zibordi et al., 2009;Bastías and Corelli-Grappadelli, 2012;Lopez et al., 2018). ...
... While an alteration of leaf morpho-physiological traits (i.e. palisade thickness, stomatal aperture, and chlorophyll content) and an increased elongation is expected (Bastías et al., 2012), little is known of the other architectural traits (i.e. number of ramifications, bud types) that apple trees will express in natural and fluctuating shade produced by upper trees and their adaptation to a changing environment. ...
... Shoots in full sun light are able to export photoassimilates to fruit three weeks after full bloom while similar export for shaded shoots is reached only five weeks AFB for 70% of the shoots (Corelli- Grappadelli, 2003), suggesting that under shade shoot growth has priority over the fruit for photo-assimilate (Bepete and Lakso, 1998). Light quality also impacts fruit development, while shade has been reported to reduce fruit growth another study reports an increase of maximal fruit growth up to 20% under blue shade nets that reduced the R:FR ratio and increased in the Blue:Red ratio (Bastías et al., 2012). ...
Agroforestry systems structured around fruit trees to produce fresh fruit is still under-developed in temperate zones. This study is based on the idea that the fruit tree can be integrated into multi-strata agroforestry systems where it would be grown with timber trees occupying the upper stratum and shrubs and/or herbaceous plants in the lower stratum. In addition to the production of fresh fruit, such systems would then combine different agro-ecosystemic services. The study focuses on a major temperate fruit species at the national and global levels, the apple tree. The general objective is to acquire a detailed knowledge of the tree's architectural development, its flowering and the quality of its fruiting, along these competition gradients. The work focuses on three actions: (i) defining an indicator to characterize each apple tree environment in this complex agrosystem, (ii) analyse at the tree scale the impact of agroforestry on morphological, phenological and architectural traits, and (iii) analysing the daily and annual sap flow regarding environmental variables and in relation to the aforementioned architectural traits. Using the light as a variable to analyse our architectural data, we have shown that apple trees did express shade avoidance traits affecting morphology (decreased taper and increased slenderness and specific leaf area), architecture (fewer growing shoots and proportion of flower clusters) and phenology (reduced number of days at full bloom). Finally, we have shown that sap flow and transpiration per unit of leaf area was affected by environmental variables (vapour pressure deficit and reference evapotranspiration). Shade did not change apple trees sap flow daily dynamics and reduced water and transpiration per unit of leaf area mainly because of morphological and architectural adaptation to shade in our experimental conditions. An increase of leaf area or a complexification of the apple tree architecture (i.e. the number of ramifications) increased transpiration per unit of leaf area during the summer. Our results suggest that while the architecture of apple trees is modified by a reduction in light intensity, it is not until a reduction of 65% that the capability to produce fruit is impeded.
... Netting for sunburn control has been widely used in apple orchards due to its effects on attenuating solar radiation and decreasing fruit surface temperature (Gindaba and Wand 2005;Bastías and Corelli-Grappadelli 2012;Kalcsits et al. 2017). However, alongside the mentioned benefit, netting can also stimulate tree vigour (Iglesias and Alegre 2006;Basile et al. 2014;Aoun and Manja 2020) and decrease colour development and fruit sugar content (Dussi et al. 2005;Iglesias and Alegre 2006;Solomakhin and Blanke 2010a). ...
... However, alongside the mentioned benefit, netting can also stimulate tree vigour (Iglesias and Alegre 2006;Basile et al. 2014;Aoun and Manja 2020) and decrease colour development and fruit sugar content (Dussi et al. 2005;Iglesias and Alegre 2006;Solomakhin and Blanke 2010a). Variations in solar radiation and fruit surface temperature, as well as the effect on reducing sunburn and colouration of fruit under the netting, depending on the material and colour used, as well as mesh size and type (Iglesias and Alegre 2006;Blanke 2007;Bastías and Corelli-Grappadelli 2012;Kalcsits et al. 2017). ...
Sunburn is possibly the main problem affecting the apple production in the Southern Hemisphere including Chile. This study focused on determining the effect of shade nets to reduce sunburn incidence and reflective mulch to improve colour on canopy microclimate, vegetative growth, fruit quality, return bloom and profitability of two apple cultivars (‘Gala Baigent’ and ‘Fuji Raku Raku’) in southern Chile. The treatments evaluated were net, mulch, net + mulch. Trees without net or mulch served as the control. Results showed that PAR transmitted under the netting was reduced in an average of 26% and the mulch increased the reflected PAR from 3% to 5% (grass row control) to 20%–37%. Shoot length, yield, fruit maturity and return bloom were not affected using either net or mulch. The incidence of sunburn under net was reduced by 76%–80%, compared to the control; however, it also reduced fruit colouration, especially in ‘Fuji Raku Raku’. The use of mulch under shade net increased the amount in 27% and 9% (average of seasons) of fruit in the Premium category of colour for ‘Gala Baigent’ and ‘Fuji Raku Raku’, respectively, which is only economically justified in circumstances of high incidence of sunburn and limitations of fruit colour.
... Light is the basic element for realizing the desired quality of fruit (Bastías and Corelli-Grappadelli, 2012). Robinson et al. (2017) in their research indicated that efficient light interception is the foundation of orchard productivity. ...
... In fact, netting is known to alter the orchard microclimate and canopy light interception from both qualitative and quantitative points of view. Their shading effect, which varies depending on thread color, net weave, and material, reduces the amount of PAR reaching the orchard but can increase diffuse light, thus improving light penetration and distribution within the canopy (Iglesias and Alegre, 2006;Bastıás and Corelli Grappadelli, 2012). ...
... Light transmission through these cover materials promotes the differential stimulation ofsome physiological responses regulated by light, such as photosynthesis, as a function of photosynthetic photon flux density (PPFD) and leaf content of a and b chlorophylls [3,11,12] Plant morphology (height, branching, internode length, etc.) is influenced by both light quality and intensity [13]. According to the literature, photo-selective shading nets change plant growth and leaf anatomy [8,13,15,16],reduce physiological disorders [3,14,21] and increment fruit yield and quality [3,[17][18][19] of different cultivated vegetables The quality of vegetables at harvest and after harvest is conditioned by the use of colored nets ( Table 2). Selahle2015 [38] Photo-selective shade nets with light modification in spectral intensity and quality can improve the overall quality, aroma volatiles, and bioactive compounds in vegetables and culinary herbs at harvest [20]. ...
Full-text available
The aim of this review is to summarize our recently reported findings on the use of pre-harvest treatments (shade nets), applied either directly or in combination with other techniques (grafting) in order to minimize physiological disorders and maximize and maintain the phytochem-ical content of vegetables. The use of colored nets for shading vegetables to protect against stress (intense solar radiation, heat stress, drought, drying winds and hailstorms) during the summer months is an effective and inexpensive method and it provides plant protection and altered micro-climate and modified intensity and quality of light. Moreover, use of colored nets supports a more intensive vegetative growth, longer vegetation, increased yield and it reduces a number of physiological disorderswhileimproving the morphological and nutritional quality of vegetables. Under color nets, tomato plants provided the fruits with thicker pericarp, firmness, higher content of lyco-pene, less percent of physiological disorders and better tolerance to transport and storage. Shade-grown plants generally have higher total chlorophyll and carotenoid contents, an increase in the total yield and a decrease in physiological disorders accompanied with an increase in the content of total phenolic compounds and flavonoids. Grafting can increase yield and fruit size and improve or reduce external and/or internal fruit quality and retained better postharvest quality, compared to the fruits from non-grafted plants. Further investigations using shade nets alone or in combination with grafting are needed to ensure the use of adequate strategies for managing plant growth of different plant species with limited physiological disorders, for increased marketable yield and for maintaining quality during storage.
... In a fruit orchard, the canopy dimension dynamically changes, and, consequently, the spectral distribution of the incoming radiation varies widely, as the light penetrates and scatters within the tree canopy due to the structure and optical properties of plant organs [65,66]. In general, the spectral modifications of light inside the tree canopy have a crucial role in growth partitioning among fruit and shoots, affecting the allocation to developing fruits in plant growth and fruit quality [67]. The effects of modification of the CRYs and PHYs abundance and photosensitivity of plants in response to the changing light on cross talks during host-pathogen interaction remain to be studied in fruit trees, and the molecular mechanisms underlying the interaction of monochromatic light with plant and bacteria remain poorly understood because they are influenced by environmental conditions. ...
Full-text available
Pathogenesis-related (PR) proteins are part of the systemic signaling network that perceives pathogens and activates defenses in the plant. Eukaryotic and bacterial species have a 24-h ‘body clock’ known as the circadian rhythm. This rhythm regulates an organism’s life, modulating the activity of the phytochromes (phys) and cryptochromes (crys) and the accumulation of the corresponding mRNAs, which results in the synchronization of the internal clock and works as zeitgeber molecules. Salicylic acid accumulation is also under light control and upregulates the PR genes expression, increasing plants’ resistance to pathogens. Erwinia amylovora causes fire blight disease in pear trees. In this work, four bacterial transcripts (erw1-4), expressed in asymptomatic E. amylovora-infected pear plantlets, were isolated. The research aimed to understand how the circadian clock, light quality, and related photoreceptors regulate PR and erw genes expression using transgenic pear lines overexpressing PHYB and CRY1 as a model system. Plantlets were exposed to different circadian conditions, and continuous monochromic radiations (Blue, Red, and Far-Red) were provided by light-emitting diodes (LED). Results showed a circadian oscillation of PR10 gene expression, while PR1 was expressed without clear evidence of circadian regulation. Bacterial growth was regulated by monochromatic light: the growth of bacteria exposed to Far-Red did not differ from that detected in darkness; instead, it was mildly stimulated under Red, while it was significantly inhibited under Blue. In this regulatory framework, the active form of phytochrome enhances the expression of PR1 five to 15 fold. An ultradian rhythm was observed fitting the zeitgeber role played by CRY1. These results also highlight a regulating role of photoreceptors on the expression of PRs genes in non-infected and infected plantlets, which influenced the expression of erw genes. Data are discussed concerning the regulatory role of photoreceptors during photoperiod and pathogen attacks.
... Light quantity and quality have been manipulated in horticultural research and industry for numerous decades to augment plant growth and development (Corré, 1983;Stuefer and Huber, 1998;Taiz and Zeiger, 2010). This is because light properties, such as quality (spectral composition), have a prominent influence on the primary metabolism of plants, influencing morphology, cell elongation and resource allocation (Bastías and Corelli-Grappadelli, 2012;Reed et al., 1993). In addition, light properties have a direct effect on secondary metabolite production, as was demonstrated by Ilić and Fallik (2017) and Sivakumar et al. (2017). ...
As the global desire for natural remedies derived from botanicals increases, the pressure on plant populations and biodiversity intensifies. Therefore, to conserve biodiversity as a valuable genetic and biochemical resource, sustainable utilisation and commercial production should be prioritised. Myrsine africana L. (MA), has recently been found to possess significant cosmeceutical properties, such as elastase inhibition (anti-wrinkle) and anti-tyrosinase (skin even tone) activity. However, this species is relatively slow growing, recalcitrant to adventitious root (AR) development, and has slightly insufficient bioactivity in raw extracts. These factors reduce the economic feasibility of producing this commercially valuable indigenous species. Consequently, this may enhance wild harvesting of this species, placing pressure on wild populations. Manipulation of light is a common practice in plant production to exploit plant growth and development, as light quantity and quality effectively influence the primary and secondary metabolism of plants. Therefore, the current study aimed to investigate the influence of selected photoselective shade net on vegetative growth and metabolites of MA shoot material. Results displayed significantly enhanced growth (p < 0.001) under green (50% density), black (50%) and red (80%) shade net in comparison to the control (cultivation under full sun) and inhibited growth under blue (50%) shade net. Shade net effectively influenced starch and soluble carbohydrate content. Furthermore, significantly higher elastase inhibition was observed under green and red shade net treatments in comparison to the control in autumn, with IC50 values of 18.59 µg/mL, 19.28 µg/mL and 37.93 µg/mL, respectively. In addition, bioactivity was significantly higher in autumn (p < 0.001) under green, red and control treatments. It can be concluded that photoselective shade net may be used to enhance plant growth and bioactivity of MA.
Full-text available
Li, Q.; Li, Q.; Li, X.; Liu, Z.; Ma, F.; Guan, Q.; Zhang, D.; et al. Effects of Four Photo-Selective Colored Hail Nets on an Apple in Loess Plateau, China. Horticulturae 2023, 9, 1061. Abstract: Hail, known as an agricultural meteorological disaster, can substantially constrain the growth of the apple industry. Presently, apple orchards use a variety of colored (photo-selective) hail nets as a preventative measure. However, it is unclear which color proves most effective for apple orchards. This study provides a systematic investigation of the impact of four photo-selective colored hail nets (white, blue, black, and green; with white being the control) on the microenvironment of apple orchards, fruit tree development, fruit quality, and yield over a two-year period (2020-2021). Different photo-selective nets do not evidently alter the intensity of light, although the nets' shading effects decrease in the order from black to green to blue. Among them, blue nets increased the proportion of blue light, while green nets enhanced the proportion of green light. On the other hand, black, green, and blue nets diminished the proportion of red and far-red light. Such photo-selective nets effectively lowered soil temperature but did not have an impact on relative humidity and air temperature. Encasing apple trees with blue nets promoted growth, increasing shoot length, thickness, leaf area, and water content, while simultaneously decreasing leaf thickness. Black nets had comparable effects, although the impacts of green nets were inconsistent. Different photo-selective nets did not significantly influence the leaf shape index or overall chlorophyll content. However, black and green nets reduced the chlorophyll a/b ratio, while blue nets slightly boosted this ratio. Additionally, blue nets proved beneficial for apple trees' photosynthesis. With the employment of a principal component analysis and comprehensive evaluation, this study concludes that blue nets offer the most favorable environmental conditions for apple growth while protecting apple orchards against hail, compared to black, white, and green nets.
Full-text available
The use of paper or nylon bags (fruit bagging) to surround tree fruit during development provides protection from a variety of pest-disease complexes for peach without yield reduction and different-colored bags have the potential to improve fruit quality based on findings from other crops. An experiment was conducted in 2019 at two locations in central Florida on peach [ Prunus persica (L.) Batch] ‘TropicBeauty’ and ‘UFSun’ to analyze the impact of a commercially available white paper fruit bag combined with a photoselective insert. The insert reduced the amount of light outside the spectrum range of interest for blue (400–500 nm), green (500–600 nm), or red (>600 nm) wavebands, or decreased fluence rate with a neutral density black (>725 nm) insert. Relative to ambient, temperature inside all bagging treatments during the daytime hours was increased by 5.1 °C. During the same time, relative humidity was reduced by 10.1%, but calculations revealed that the water vapor pressure was elevated only for treatments that had a plastic colored (blue, green, or red) insert. An orthogonal contrast revealed that the elevated water vapor around the fruit in a colored bag increased the concentration of chlorophyll at harvest but had no effect on other quality parameters. Compared with unbagged fruit, red-bagged fruit were 1.8 times firmer and green-bagged fruit and had a lower peel chroma. White-bagged (without photoselective insert) fruit had similar nutrient concentrations for the peel, flesh, and pit when compared with unbagged fruit. When bags remained on the fruit until harvest, anthocyanin concentration in unbagged fruit peel was double the amount in white bags and 6-fold more than the bags with color inserts. Different-colored bagging treatments did not influence insect attraction or fruit quality parameters, such as fruit size, diameter, difference of absorbance (DA) index, total soluble solids (TSS), titratable acidity (TA), pH, peel lightness, peel hue, flesh lightness, flesh hue, or flesh chroma. Relative to full sun, the colored bag treatments allowed between 3.7% (black) and 17.4% (red) of the photosynthetically active radiation ( PAR ). Additional research is needed to determine if an increase in fluence rate at specific spectral wavelengths can affect the quality for peach grown in bags in the field.
Full-text available
Nets are frequently used to protect agricultural crops from excessive solar radiation, environmental hazards or pests. We have developed a new concept, by which the nets are designed to specifically filter sunlight, concomitant with providing the desired physical protection. A series of photoselective nets (Color Nets) was developed for outdoor use, each one absorbing different spectral bands, and at the same time increasing the relative proportion of scattered/diffused light. The spectral manipulation is aimed at specifically promoting physiological responses, while light scattering improves light penetration into the inner canopy. The relative enriching of the intercepted light with "good" parts of the spectrum, while reducing "bad" parts, may allow better utilization of the solar energy. Earlier studies of ornamental crops, traditionally grown under black shade nets, revealed differential responses to the photoselective shading. Ongoing studies of low-shading Color Nets in numerous fruit crops and climatic regions showed that nets of the same shading factor but different chromatic properties can differentially affect various attributes of tree performance, including production, fruit size and quality, and advancement or delay in the timing of harvest. The netting further ameliorates extreme climatic fluctuations, reduces heat/chill stresses, and improves the resulting canopy activity and water use. The results demonstrate the potency of photoselective netting for improving the agro-economical performance of horticultural crops, especially (but not only) in harsh climates and arid zones.
Full-text available
Young citrus trees and seedlings in Florida's commercial nurseries are often grown under shade cloth netting to avoid high light and temperature. To investigate the potential benefit of altering radiation by colored shade nets, `Cleopatra' mandarin (Cleo, C. reticulata Blanco) seedlings and potted `Valencia' trees [ Citrus sinensis (L.) Osbeck] on Cleo or Carrizo [Carr, C. sinensis × Poncirus trifoliate (L.) Raf.] rootstocks were grown in full sun or under 50% shade from blue, black, silver, grey, and red colored shade nets. Changes in photosynthetically active radiation (PAR) and temperatures under the shade were monitored. Leaf function and leaf chlorophyll contents were measured, and plants were harvested by the end of the experiment for shoot and root growth measurements. Plants under the shade received an average of 45% PAR and had lower mid-day leaf temperature than plants in full sun. Plants under blue nets had greatest leaf chlorophyll a, b, and total chlorophyll content, whereas those under red nets had the lowest. However, shading improved photosystem II efficiency from measurements of leaf chlorophyll fluorescence (Fv/Fm) regardless of the color of shade nets. Shading increased shoot growth, shoot to root ratio, and total plant dry weight of Cleo seedlings, especially those under silver nets.
The sections in this article are Introduction Regions of Light Spectrum Important for Plant Growth and Development Plant Responses to Quality of Light Light Manipulation by Horticulture Industry Future Prospects
Two-year-old peach (Prunus persica Sieb, et Zucc. cv. Ohkubo) trees were shaded so as to receive approximately 50%, 25%, 10% of full daylight from the bud sprouting stage, and their growth was compared with that of unshaded control trees two months after treatment. Compared with those in the control group, average leaf area was increased 45%, 71% and 36% by 50%, 25% and 10% of full sun, respectively. Shade-grown leaves were thinner, flatter, and darker green than sun-grown ones; leaves grown in heavy shade (10% of full sun) had one or two poorly developed palisade layers; in contrast, sun-grown leaves had two or three layers of well developed palisade cells. Dry weight per fresh weight or per unit area of leaf was highest in sun-grown leaves and lowest in leaves grown in heavy shade. Stomatal density decreased with shading. Chlorophyll content per unit leaf area or per dry weight increased with shading. Shade-leaf chloroplasts (10% and 25% of full sun) were larger and rich in thylakoids, while sun-leaf chloroplasts (50% and 100% of full sun) showed poorly stacked grana. Starch accumulation in the chloroplasts of sun- leaves was markedly higher than in shade-leaf chloroplasts. In the smaller chloroplasts from the palisade cells in sun-leaves, chloroplast nuclei (ct-nuclei) were localized at the periphery of the plastids, frequently in a discrete band, differing from the central random location of ct-nuclei in the shade-leaves (10% and 25% of full sun).
We introduce here a new approach for improving the utilization of solar radiation by fruit trees. This approach is based on selective filtration of the light by plastic shade nets (cloths) with special optical properties that modify the quality of natural radiation. A series of colored shade nets (ColorNets) were developed to specifically modify the incident radiation (spectrum, scattering and thermal components). Depending on the pigmentation of the plastic and the knitting design, the nets provide varying mixtures of natural, unmodified light, with spectrally modified scattered light. Use of the nets aims to optimize desirable physiological responses, in addition to providing physical protection. Following the substantial effects of several ColorNets on shoot elongation, branching and flowering in ornamentals (Oren-Shamir et al., 2001), we have applied the colored netting to deciduous fruit trees. The experiments were carried out in commercial apple and peach orchards, using ColorNets with reduced shading factors (15-30%, compared with the 50-80% used in ornamentals). The first year results show positive effects on flowering, fruit-set, fruit size, colour and internal quality, in addition to non-specific reduction of water stress, superficial damage, and sunburn. This approach opens new perspectives for improved performance of fruit tree orchards under specialized protection.
The role of light quality and quantity in regulating growth and differentiation of Prunus persica plants was evaluated using different coloured filters in an outdoor experiment. Examination of total growth showed that neutral shading (80% of transparent control) did not affect shoot length, internode elongation, leaf number, and branching, but strongly influenced the anatomical characteristics of leaves. The combination blue + far red (B + FR) acted quite differently from the combination red + far red (R + FR) and caused a general inhibition of growth phenomena. Shorter and more compact plants were produced under B + FR tunnels where the reduction in shoot elongation was consistent with the reduction in internode length. Furthermore, light transmitted through the B + FR filter resulted in lower branching and in smaller and thinner leaves compared with those grown under the other light treatments. The number of flowers was not affected by either light quality or quantity. The negative effect on growth and development of the light environment under B + FR was associated with low P(fr) (far red light absorbing form of phytochrome) and with the action of blue light.
The involvement of photomorphogenic photoreceptors in anthocyanin synthesis was investigated in apple fruits under UV light from 280 to 320 nm (UV-B) and red light (R). Short-term R treatment was ineffective in the induction of anthocyanin synthesis but the involvement of phytochrome was indicated by the results of long-term irradiation (18 h) with R. The inductive effect of 18 h UV-B on anthocyanin synthesis was stimulated synergistically by subsequent irradiation with R for 15 min, and the R, far-red light (FR) photorevesibility of this effect indicated the involvement of phytochrome in this synergism. The effect of UV-B on anthocyanin synthesis was not influenced by subsequent irradiation with FR, suggesting that the effect of UV-B was independent of phytochrome, and that a specific photoreceptor for UV-B was involved. When R was given simultaneously with UV-B (18 h), anthocyanin was synthesized at a much higher rate than it was after sequential irradiation with UV-B and R. Photosynthesis was shown to be involved inthis synergistic increase in the synthesis of anthocyanin, although the involvement of phytochrome in the expression of this response, at least in part, was suggested by a reduction in the rate of anthocyanin synthesis by FR.