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30 www.HortiWorld.nlFlower TECH 2006, vol. 9/no. 8
With the increasing useof coloured shade onfoliage and plant
pro-duction in general, experimentshave been conducted at
theExperimental Station FbioBaudrit, part of the Universidadde
Costa Rica, analyzing theeffect of different colours onornamental
crops. In one ofthem, Gerard Ducca Jimnezevaluated the effect of
six col-oured shades on 20 foliage spe-cies of economical
importance(encompassing six botanicalfamilies), for 30
months.During this period the evaluat-
ed plant variables were tipgrowth, number, width andlength of
leaves, among others.
The observed climate variable was the Red: Far Red ratio as
ameasure of light quality.
Background andexperiment
The visible part of light lies within the range 400 to 700nm,
and the Red (640 to 740nm) and the Far Red (700 to740 nm) fractions
are in itsextreme. The quotient R: FR iscommonly used as an
indicatorof light quality since it affects
the phytochrome, apigment involved inthe control of
plantmorphogenesis andits adaptability to
the environment.Near the tropics andunder full sunlightthis
ratio is around1: 1 to 1: 2.However, it can alsobe altered; using
col-oured nets for exam-ple, causing changesto stem elongation,etc.
Portions of theglobal radiation
emitted by the sun are eitherfiltered, refracted, reflected
orabsorbed by the nets, accordingto its colour, % shade and
otherfactors. Climatic and seasonalfactors also influence
lightquality, including the R: FRratio ( Table 1 ).
During the trial period a year-ly average of 6.02 GJ of
globalradiation was measured at thestation, and the
experimentalplot covered an area of 1536m 2. Six colours were used,
all
with 60% shade: red, yellow,
silver, grey, black and blue, thecontrol being black. When
allmeasurements are consideredmore than 50 plant characteris-tics
were observed, thereforeonly a selection of the resultsare
described here.
Leaf-producing plants Asparagus virgatus highest
monthly leaf production wasunder yellow, with an average
of 3.8. As far as rachis- andleaf-length were measuredthere were
no statistical differ-ences. Anthurium most leaves were
equally produced under grey,blue and red, all with 2.6 newleaves
in a month; the samethree colours were statisticallythe same for
leaf- and rachis-length. For leaf blade lengthand width, red and
grey tookequal first position.
Rumhora adiantiformis nostatistical differences for nei-
ther the number of leaves long-er than 30 cm nor leaf
bladelength, whereas yellow pro-duced the most leaves under 30cm.
Both the longest rachis andleaf were found under red.
Davallia the most leavesgreater than 30 cm were meas-ured under
yellow, as well asfor the leaf category under 30cm. In three other
measure-ments both yellow and red
The use of relatively simple technical solutionsadapted to the
local conditions is a trademark ofthe plant sector in Costa Rica.
The drive towardscoloured nets is a good example; growers
areinterested in it and research is providinginformation for
important local crops.
By Mauricio Mathias Email: [email protected]
Choice of screen colourdepends on traits desired
Shade colour R: FR Ratio * Dry season Rainy seasonRed 1,0643 a
1,0723 a
Yellow 1,0936 b 1,0754 a
Silver 1,1238 c 1,1347 b
Grey 1,1635 e 1,1880 d
Black 1,1696 f 1,1902 de
Blue 1,1755 g 1,1939 e
*Averages with the same letter do not differ statistically,
Duncan test at 5%.
Source: Gerardo Ducca Jimnez, 2005.
Table 1. Red: Far red light ratio measuredunder different colour
shade.
The coloured arrows highlight the coloured shade nets being
tested.
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Flower TECH 2006, vol. 9/no. 8 3 www.HortiWorld.nl
were statistically first; thelengths of leaf, rachis and
leafblade.
Philodendrum no statisticaldifference under any of the col-ours,
with a monthly average of5.1 leaves/plant, with meanlength of 38.5
cm. Aspidistra again no statistical
differences, average leafnumber was 3.8 for all colours,and the
mean length 37.7 cm.
Tip-producing plantsCodiaeum variegatum the
most and the longest tips werefound under yellow for all
three tested varieties, eventhough statistical differences
varied.Dracaena sanderiana no sta-
tistical differences for thenumber of tips under any ofthe
colours for both tested vari-eties. For tip length, red andrey came
first for the var. sand-eriana, but for var. gold it wasred and
blue.
Schefflera arboricola no sta-tistical differences for thenumber
of tips; for length oftips red, blue and yellow camefirst but did
not differ amongsteach other.
Schefflera actynophila equallyhigh tip production under blueand
black, top length of tipsunder black, yellow and red
were alike.Dracaena deremensis no sta-
tistical differences under anycolour for the number of tips,nor
for tip length.
Ornamental palmsPhoenix roebelenii red pro-duced the tallest
plant as wellas the longest leaf, whereas sil-
ver, black and yellow gave thebest results regarding thenumber
of leaves.
Dypsis lutescens var. Areca again under red the plants
weretallest, and the mean leaflength was the longest. Themost
leaves however, wereunder blue.
Chamaedora costarricana red,blue and grey tied on top forplant
height; red, blue andblack for number of leaves, butred alone came
on top for leaflength.
Chamaedora cataractarum no statistical differences forplant
height, or leaf length, butthe most leaves were producedunder blue
and grey alike.
Gerardo Ducca concludes thatlight quality and intensity
cansignificantly alter plant charac-teristics, but the choice of
amost suitable colour willdepend on the final resultintended by the
grower, since it
depends on species, or even variety. This decision
influencesplant morphology and devel-opments, and should be
gearedtowards the specific demands
of markets. For further studieson the influence of
colourshading, he recommends stud-ies to assess its impact on
pestsand diseases. n
Chlorophyll content is measured as an indicator of foliage
colour.
