Coconut Research Institute Repository

Ekanayake, G.K.

Perera, S.A.C.N.

Dassanayake, P.N.

Everard, J.M.D.T.

Identification, characterization and conservation of new coconut phenotypes from southern Sri Lanka

Nadheesha, M.K.F.

Monthly pattern of nutrient removal by the coconut palm

Nainanayake, A.D.

Morison, J.I.L.

A case study on physiology-based drought screening of coconut with selected accessions

Senarathne, S.H.S.

Sangakkara, U.R.

Influence of selected environmental factors on germination and emergence of Hyptis suaveolens of plantations in Sri Lanka

Yalegama, L.L.W.C.

Jayasekara, C.

Upali, S.A.R.

Abeygunawardhana, M.J.

COCOS (2007), 18  67 - 76 
Printed in Sri Lanka 
ORGANOLEPTIC AND CHEMICAL PROPERTIES OF COCONUT AND 
SESAME OILS AND THEIR BLENDS 
 
L.L.W.C. Yalegama, C. Jayasekara, S.A.R. Upali1, M.J. 
Abeygunawardhana1 
 
Coconut Research Institute, Lunuwila 1 University of Peradeniya, Peradeniya 
 
ABSTRACT 
 
The chemical properties of six blends of coconut and sesame oils, and the 
organoleptic qualities of the blends and foods prepared with them were 
studied. The blends prepared for testing were: (1) 100% coconut oil; (2) 90 
% coconut and 10 % sesame; (3) 75 % coconut and 25 % sesame; (4) 50 % 
coconut and 50 % sesame; (5) 25 % coconut and 75 % sesame; and (6) 100 
% sesame oil.  
 
In sensory evaluations, on a Five-point Hedonic scale, all the oil blends were 
found to be acceptable for deep frying of fish and oil cakes, and shallow 
frying of noodles. Oil blends 1, 2 and 3, in descending order, received high 
sensory scores (4.2-3.8) for taste of deep fried fish; blends 6, 4 and 5 scored 
less (3.0 points each), but were acceptable. Blend 3 received the highest 
score of 4.3 for taste of both oil cakes and noodles; other blends ranged from 
3.6-3.9.  
 
Colour and smell of oil blends 6, 5 and 4 scored only 2.2-2.5 and were not 
acceptable. Blends with 75% or more of coconut oil scoring 4.2-3.8 for 
colour and 3.7-3.3 for smell, were acceptable. All the oil blends stored well 
up to five months without exceeding the prescribed SLS standard for FFA 
values for edible coconut (white oil) and sesame oils. Blends 1, 2 and 3, 
containing less than 50 % sesame oil, can be stored for 6 months. After 6 
months FFA levels showed an increasing trend. Iodine value did not change 
significantly but Peroxide values increased steadily during storage. Oil 
blends with higher proportions of coconut oil had relatively low peroxide 
values. Fatty acid composition of coconut oil can be altered by blending with 
sesame oil to increase the unsaturated fatty acid content of coconut oil 
without affecting its organoleptic qualities.  
 
Key words: sesame oil, saturated fatty acids, monounsaturated fatty acids, 
polyunsaturated fatty acids, oil blends 
 
 
 67
INTRODUCTION 
 
Fats and oils are of major importance in human nutrition. They provide 
energy, helps the body absorb fat soluble vitamins, A, D, E and K, and 
supply essential fatty acids. Essential fatty acids are fatty acids that cannot be 
synthesized in the human body from precursors and therefore have to be 
provided in the diet. Fats and oils improve the texture and palatability, and 
also add characteristic flavours to food preparations.  
 
Coconut being an extensively cultivated plantation crop in Sri Lanka, its oil 
is the most popular cooking oil in the country. Coconut oil is widely used for 
both shallow and deep frying, in domestic and commercial scale food 
preparation. Coconut oil imparts desirable flavour, texture and taste to food. 
Sesame oil is also used as a cooking oil in Sri Lanka. Sesame is cultivated 
and processed on a small scale in the drier parts of Sri Lanka and a limited 
quantity of the unrefined oil is available in the market. Sesame oil is 
traditionally used by the Tamil community in Sri Lanka and it is their 
preferred cooking oil. Most others find its smell and taste less than agreeable.  
 
Coconut oil is categorized as a lauric oil, and contains a high percentage of 
lauric acid, a medium chain fatty acid, and very small amounts of essential 
fatty acids. Approximately 60 % of the fatty acids in coconut oil are short 
and medium chain saturated fatty acids. Short and medium chain fatty acids 
are easily digestible. All the other vegetable oils are rich in essential fatty 
acids and contain high amounts of long chain fatty acids. Nutritionists advice 
the intake of an oil that contains saturated, monounsaturated and 
polyunsaturated fatty acids in the ratio 1:1:1 (Bockisch, 1998). A vegetable 
oil with a balanced fatty acid composition is rare or non-existent and brings 
to the fore the importance of blended vegetable oils. In many countries edible 
oil is marketed as a blend of two or three oils (Murthi et al, 1987). For 
example, Lokdhara is a blend of 67 % palm olein and 33% ground nut oil 
(Semwal and Arya, 2001). 
 
Sesame oil is a highly unsaturated oil, rich in essential fatty acids (Bockisch, 
1998). Thus, blending coconut and sesame oils to produce a cooking oil with 
a desirable composition of fatty acids, including essential fatty acids, and 
with acceptable organoleptic properties appears to be a feasible proposition. 
Therefore a study was undertaken to prepare different blends of coconut oil 
and sesame oil and evaluate the organoleptic and chemical properties of the 
oil blends, and also foods prepared with the blends. As coconut oil is by far 
the most popular cooking oil in Sri Lanka the blends would target coconut 
oil users.  
 68
MATERIAL AND METHODS 
 
Coconut oil used in the study was obtained from the Coconut Research 
Institute and the sesame oil was procured from a sesame oil mill in Kekirawa 
area in Anuradhapura District. Both oils were unrefined. Four oil blends with 
different proportions of coconut and sesame oils were prepared for testing 
along with the straight oils as references. The oils were mixed for 20 minutes 
with a magnetic stirrer and stored in glass bottles at ambient conditions. The 
coconut oil to sesame oil ratios of the blends and their colour are given in 
Table 1. 
 
Table 1. Ratio of coconut oil to sesame oil in the blends and their colour 
 
Blend No. Ratio Coconut : Sesame Colour 
01 100 : 0 Light yellow 
02 90 : 10 Light yellow 
03 75 : 25 Yellow 
04 50: 50 Brownish yellow 
05 30 : 70 Brownish yellow 
06 0: 100 Light brown 
 
Chemical properties of oil blends such as Free fatty acid (FFA) content, 
Peroxide value and iodine value were measured over six months at monthly 
intervals as per AOCS (1990). The blends were analysed for their fatty acid 
composition using Gas Chromatography (AOCS, 1990). 
 
Organoleptic qualities of the oil blends were evaluated in four sensory 
evaluation tests:  one to evaluate the colour and smell of the oil blends, and 
three sensory tests to evaluate deep fried and shallow fried foods prepared 
with the oil blends. The evaluations were made by 21 semi-trained panelists. 
Five point hedonic scale, with a score of 5 for ‘like very much’, 4 for “like 
slightly”, 3 for “neither like nor dislike” 2 for “dislike slightly   and 1 for 
‘dislike very much’ was used to evaluate the degree of liking, for a particular 
quality attribute. A score of 3.0 or higher denotes that the attribute is 
generally acceptable. 
 
Randomized complete block design was used to evaluate chemical properties 
and the Friedman Ranking test was used for sensory evaluations. Analysis of 
variance (P< 0.05) was performed on the sensory evaluation scores using the 
MINITAB statistical package (MINITAB Inc., State Collage, PA). 
 
 
 69
RESULTS AND DISCUSSION 
 
Organoleptic qualities of the oil blends 
 
The sensory evaluation carried out for the degree of liking of colour and 
smell of the oil blends showed significant differences (P< 0.05) between 
them. Blends 1, 2 and 3 with 100% coconut oil, 90% coconut & 10% sesame, 
and 75% coconut & 25% sesame, had scores greater than 3 for both colour 
and smell indicating their acceptance by the consumer (Table 2). Blends 4, 5 
and 6 which contained 50%-100% sesame oil scored less than 3, and were 
not acceptable. The 100% coconut oil was light yellow and 100% sesame oil 
was light brown in colour (Table 1). Blend No.2 (90% coconut & 10% 
sesame) had  the highest score for colour (4.2 out of 5.0).  
 
Table 2. Degree of liking of the colour and smell of oil blends, scored on a 
Five-point hedonic scale.  
 
Estimated medians Blend No. Blend composition Colour Smell 
01 100% coconut 3.8 3.7 
02 90% coconut : 10% sesame 4.2 3.3 
03 75% coconut : 25% sesame 3.8 3.3 
04 50% coconut : 50% sesame 2.5 2.3 
05 30% coconut : 70 % sesame 2.5 2.2 
06 100% sesame 2.2 2.2 
 
Organoleptic qualities of foods prepared with the oil blends 
 
Fried fish 
 
Fresh fish was deep fried in the different oil blends and evaluated for 
organoleptic qualities of appearance, crispness and taste on the five-point 
hedonic scale. All six oil blends scored 4.0 out of 5.0 for appearance, and 
approximately 4.0 for crispness, with blend No. 2 (90% coconut & 10% 
sesame) and blend No. 5 (30% coconut & 70% sesame) receiving the highest 
and lowest scores respectively (Table 3). Fried fish prepared with 100% 
coconut oil and blend No. 2 (90% coconut & 10% sesame) received 4.2 and 
4.0 respectively for taste; blend No.3 (75% coconut & 25% sesame) scored 
 70
3.8 and the other blends scored 3.0. In the five-point hedonic scale a score of 
3.0 is regarded as acceptable. Therefore all six blends tested were acceptable 
for deep frying of fish.  
 
Kevum (Oil cake) 
 
The oil blends were tested for their suitability for preparing a traditional food 
like oil cake (Kevum). Oil cakes prepared with different blends were 
evaluated for their smell and taste. All six oil blends scored 3.8 out of 5.0 for 
the smell of Kevum (Table 3) but the scores for taste differed. Kevum 
prepared with blend No. 3 (75% coconut & 25% sesame) was the most 
preferred scoring 4.3 for taste. All the other blends received scores of 3.6 to 
3.9. Thus all six oil blends are acceptable for the preparation of Kevum.  
 
Table 3. Degree of liking for the sensory attributes of foods prepared with oil 
blends, scored on a five-point hedonic scale.  
 
Estimated medians 
Fried fish Oil cake Noodles Blend No. Appearance Crispness Taste Smell Taste Smell Taste 
01 4.0 3.9 4.2 3.8 3.9 3.8 3.6 
02 4.0 4.1 4.0 3.8 3.7 3.8 3.7 
03 4.0 3.9 3.8 3.8 4.3 3.8 4.3 
04 4.0 3.9 3.0 3.8 3.6 3.8 3.9 
05 4.0 3.8 3.0 3.8 3.6 3.8 3.6 
06 4.0 3.9 3.0 3.8 3.6 3.8 3.6 
 
Noodles  
 
The oil blends were tested for their suitability for shallow frying by 
preparing a popular food like noodles. Noodles prepared with different oil 
blends were evaluated for their smell and taste. All six oil blends scored 3.8 
out of 5.0 for the smell of noodles. Blend No. 3 (75% coconut & 25% 
sesame) was the most preferred for taste, scoring 4.3 out of 5. All the other 
blends were acceptable and received scores of 3.6 to 3.9. Accordingly, while 
all the blends tested are acceptable, blend No. 3, 75% coconut & 25% 
sesame is the best blend for preparation of shallow fried foods like noodles. 
It is interesting to note that for shallow frying the oil blends were superior to 
the straight oils, which received the lowest scores. 
  
 
 71
Chemical properties of the oil blends 
 
Free fatty acid content 
 
Free fatty acid (FFA) content is an indicator of the keeping quality of a 
cooking oil. The  SLS standard for the FFA content of edible coconut (white 
oil) and sesame oil is less than 1%, and 3% respectively. The FFA content of 
the oil blends recorded, at monthly intervals, over the six-month storage 
period are presented in Fig. 1. The initial FFA values conform to the SLS 
standard. The initial FFA values of the blends were raised with the addition 
of sesame oil. The FFA content of 100% coconut oil increased from 0.032% 
up to 0.930% and 100% sesame oil increased from 2.46% up to 3.7%, during 
the six month storage period.  
 
Change of free fatty acids during storage
0
0.5
1.5
2.5
 
1
 
2
 
3
3.5 
4
1 2 3 4 5 6 7
Time (months) 
100 %CNO 90% CNO:10%SO 75% CNO:25%SO
50%CNO:50%CNO 30%CNO:70%SO 100%SO
Fr
ee
 fa
tty
 a
ci
ds
 c
on
te
nt
 
(%
as
 la
ur
ic
 a
ci
d)
 
 
 
Figure 1. Effect of storage on the free fatty acid content of oil blends 
 
Peroxide value 
 
Initial peroxide values of 100% coconut oil and 100% sesame oil was 3.08 
meqv/kg and 1.68 meqv/kg respectively. The peroxide values of oil blends 
recorded, at monthly intervals, over the six-month storage period are 
presented in Fig. 2. Peroxide values of all the oil blends increased rapidly 
during storage. This could be ascribed to the oils being unrefined. Relatively 
low peroxide values were recorded in the blends containing high percentages 
of coconut oil (100 % to 75 % coconut oil). Peroxide values of these blends 
appeared to reach an equilibrium state, while the others showed a steady 
increase during the storage period.  
 72
 0 
5 
100 %CNO
 
 
Figure 2: Effect of storage on the Peroxide value of the oil blends 
 
Iodine value 
 
The initial iodine values of coconut oil and sesame were 7.3 and 103.3 
respectively, which indicates that sesame oil is highly unsaturated compared 
to coconut oil. As to be expected, the iodine value of the blends increased as 
the proportion of sesame oil increased. Iodine values of the pure oils and 
their blends did not change significantly during storage.  
 
Change of Iodine value during storage
0
20
40
60
80
100
120
1 2 3 4 5 6 7
Storage time (Months)
Io
di
ne
 v
al
ue 100 %CNO
90% CNO:10%SO
75% CNO:25%SO
50%CNO:50%CNO
30%CNO:70%SO
100%SO
 
Figure 3: Effect of storage on the Iodine value of oil blends 
 
 
 
10
15
 
 
20 
1 2 3 4 5 6 7
90%
CNO:10%SO
75%
CNO:25%SO
50%CNO:50%C
NO
30%CNO:70%S
O
100%SO
Pe
ro
xi
de
 V
al
ue
 m
eq
/K
g 
Time (Months) 
 73
Fatty acid composition of oil blends 
 
Percentage content of fatty acids, and of the saturated, monounsaturated and 
polyunsaturated fatty acid types (SFA, MUFA and PUFA), in the oil blends, 
are presented in Tables 3 and 4 respectively. The major constituent of 
coconut oil was Lauric acid (48.96%). Oleic acid (41.83%) and Linoleic acid 
(43.62%) were the major constituents of sesame oil. Increasing the sesame 
oil content in the blend decreases Lauric acid content and increases Oleic and 
Linoleic acid content. For instance, Blend No. 3 with 75 % coconut oil and 
25 % sesame oil, has 41.03 % Lauric acid , 11.04 % Oleic acid and 11.10 % 
Linoleic acid, and a SFA:MUFA:PUFA ratio of 78: 11:11. There was a 
better balance of fatty acids in Blend No. 5 (30% coconut oil  and 70% 
sesame oil) with 21.27% Lauric acid, 25.69% Oleic acid and 27.34 % 
Linoleic acid, and a SFA:MUFA:PUFA ratio of 47: 26:27.  
 
Table 3: Percentage content of fatty acids in the oil blends 
 
Blend No. Fatty acid 1 2 3 4 5 6 
Caproic (C6:0)  2.11 2     
Caprilic (C8:0)  8.65 7.79 7.45 4.36 3.06  
Capric (C10:0)  5.52 4.97 4.96 2.75 2.27  
Lauric (C12:0) 48.96 44.06 41.03 24.85 21.27  
Myristic (C14:0) 17.4 14.76 14.23 9.2 7.68  
Palmitic (C16:0) 7.14 7.82 7.37 9.65 8.86 9.36 
Stearic (18:0) 2.32 2.61 2.82 4 3.83 5.19 
Oleic (C18:1) 6 9.28 11.04 22.43 25.69 41.83 
Linoleic (C18:2) 1.9 6.71 11.1 22.76 27.34 43.62 
 
1 - 100 % coconut oil, 2 - 90 % coconut oil and 10 % sesame oil, 3 - 75 % 
coconut oil and 25 % sesame oil, 4 - 50 % coconut oil and 50 % sesame oil, 
5 - 30 % coconut oil and 70 % sesame oil, 6 - 100 % sesame oil 
 
 
 
 
 
 
 
 
 
 74
Table 4. Percentage content of SFA, MUFA and PUFA in the oil blends 
 
Blend No. Fatty acid 1 2 3 4 5 6 
SFA  92 84 78 55 47 15 
MUFA  6 9 11 22 26 42 
PUFA  2 7 11 23 27 44 
 
SFA – Saturated fatty acids; MUFA – Monounsaturated fatty acid; PUFA – 
Polyunsaturated fatty acids 
1 - 100 % coconut oil, 2 - 90 % coconut oil and 10 % sesame oil, 3 - 75 % 
coconut oil and 25 % sesame oil, 4 - 50 % coconut oil and 50 % sesame oil, 
5 - 30 % coconut oil and 70 % sesame oil, 6 - 100 % sesame oil 
 
The deficiency in essential fatty acids is the main disadvantage of coconut oil. 
Pure coconut oil (Blend No.1) contains only 6% MUFA and 1.9% PUFA 
while pure sesame oil (Blend No. 6) contains 41.83% MUFA and 43.62% 
PUFA. MUFA and PUFA contain essential fatty acids that are necessary for 
growth. These essential fatty acids are not synthesized in the human body 
and have to be supplied by way of food. If a blend of sesame and coconut 
oils, such as Blend No. 5, is used in food preparation it would provide a good 
source of essential fatty acids. In this regard it is noteworthy that in sensory 
evaluations Blend No 5 proved to be acceptable for preparation of oil cakes, 
deep frying of fish and shallow frying of noodles.  
 
CONCLUSIONS 
 
Blends of coconut and sesame oil stored well for approximately 6 months. 
The chemical parameters, FFA, iodine value and peroxide value increased 
during storage. However, the FFA content of the blends did not exceed the 
limits specified for the pure oils. Fatty acid composition of the highly 
saturated coconut oil (92.1% SFA) can be altered by blending with sesame 
oil to increase the unsaturated fatty acid content, without affecting its 
organoleptic qualities. A blend of 30% coconut oil and 70% sesame oil had a 
SFA:MUFA:PUFA ratio of 47:26:27 and contained 21.27% Lauric acid, 
25.69% Oleic acid and 27.34% Linoleic acid. The blended oils were suitable 
for preparing a wide range of foods. They can be used for deep frying of fish, 
preparation of oil cake and stir-frying noodles. In sensory evaulations the 
organoleptic qualities of food prepared with oil blends were found to be 
acceptable.  
 
 
 75
REFERENCES 
 
Bockisch, M. (1998). Importance of fats in Fats and oils hand book. AOCS 
press, Champaign, Illinois. 
 
Semwal, A. D., Arya, S.S. (2001) Studies on the stability of some edible oils 
and their blends during storage. J. Food Sci. Technol., 38 (5): 515-
518. 
 
Murthi, T.N., Sharma, M., Devadhara, V.D., Chatterjee, S., Chakraborty, 
B.K. (1987). Storage stability of edible oils and their blends. J Food 
Sci. Technol 24: 84-87. 
 
AOCS (1990). Official methods and recommended practices of the American 
Oil Chemist’s Society, 4th Edn. Champaign, Illinois 
 76


Organoleptic and chemical properties of coconut and sesame oils and their blends

Madurapperuma, W.S.

Mendis, H.

Ranasinghe, C.S.

Premasiri, N.

Gunawardena, M.

COCOS (2007), 18  21 - 30 
Printed in Sri Lanka 
A COMPARATIVE STUDY OF WATER MOVEMENT IN LEAF SCORCH 
DECLINE AFFECTED AND HEALTHY COCONUT PALMS USING 
LITHIUM AS A NON-RADIOACTIVE TRACER 
 
W.S. Madurapperuma, H. Mendis, C.S. Ranasinghe, 
N. Premasiri and M. Gunawardena 
 
Coconut Research Institute, Lunuwila, Sri Lanka 
                                                                                                                                                  
ABSTRACT 
 
Obstructions to the movement of water, by physical blockages in the 
vascular system, are a possible cause of the Leaf Scorch Decline (LSD) 
disorder of coconut palms. This hypothesis was tested by comparing the 
pattern of water movement in healthy and LSD-affected coconut palms, 
using Lithium, a non-radioactive tracer, as an indicator. Pattern of water 
transport in the leaf canopy of healthy and LSD-affected palms was similar 
but the quantities transported were different. Less water movement in 
moderate-LSD palms than in healthy and mild-LSD palms suggest the 
development of obstructions to water movement when the disorder increases 
in severity. Uptake of water into the root system was not affected by the LSD 
disorder. However, in moderate-LSD palms more water was retained in the 
roots than in healthy and mild-LSD palms. This also points to restrictions to 
water movement in the moderate-LSD palms. The relatively high amounts of 
Li retained in the roots of healthy and mild-LSD palms need further 
investigation. 
 
Key words: Leaf Scorch Decline, visible symptoms, pattern of water 
movement, non-radioactive tracer 
 
INTRODUCTION 
 
The characteristic visible symptom of the Leaf Scorch Decline (LSD) 
disorder is leaf scorch that starts from the tips of the leaflets and advances 
towards the midrib of the frond (Davis, 1962; Ekanayake, 1964, Rajapaksha 
and Fernando, 1995; Madurapperuma et al, 2004; Ranasinghe, 2005). Scorch 
first appears on the physiologically less active mature fronds (mild stage of 
LSD), and advances progressively to the younger fronds of the middle whorl 
of the canopy (moderate LSD) and to still younger fronds (severe stage). The 
other symptoms that develop progressively in moderately and severely 
affected palms are: a reduction in the length of newly emerging  fronds; 
number and size of inflorescences; nut set and yield; and bearing abnormally 
 21
elongated nuts, and tapering of the trunk (Peries, 1968; Rajapaksha and 
Fernando, 1995; Madurapperuma et al., 2004; Ranasinghe, 2005). 
 
Physiological studies with LSD-affected coconut palms have demonstrated a 
significant reduction in the transpiration rate, photosynthesis and leaf water 
potential (LWP); and an increase in leaf stomatal resistance and ABA 
concentration in the xylem sap, in comparison to healthy palms (Jayasekara 
et al., 1989; Ranasinghe, 2005). This suggests that LSD-affected palms are 
water stressed. Even with the soil moisture level at field capacity (FC), the 
LWP of LSD-affected palms was lower than in healthy palms (Jayasekara et 
al., 1989), which points to an internal water deficit condition in LSD palms. 
This condition could be attributed to either poor water absorption due to a 
paucity of live roots in LSD-affected palms (Jayasekara and Premasiri, 1986; 
Mahindapala and Chandrasena, 1975; Ranasinghe et al., 2002), or physical 
blockages in the water transport tissues.  
 
Physical barriers in the vascular system limiting the movement of water to 
plant tissues will also restrict the supply of nutrients to these tissues and 
retard growth. Nutrients absorbed by the roots are moved upwards with the 
transpiration stream. Hence the efficiency of nutrient uptake will depend on 
the physiological status of plants (Vidanaarachchi and Nor, 1994).  
 
Clearly, in plants under physiological stress the uptake of water and nutrients 
is inevitably reduced. Generally, when the stress factors are removed the 
plants recover. However, LSD-affected coconut palms suffer from water 
stress even under optimum environmental conditions. It may, therefore, be 
assumed that physical blockages in the vascular system are involved. The 
foregoing leads to the hypothesis: water movement from roots through the 
trunk to the crown of LSD-affected palms is restricted by physical blockages 
in the vascular system. This study aims to test the hypothesis, and identify 
the zones where restrictions occur, using Lithium as a non-radioactive tracer. 
 
MATERIALS AND METHODS 
 
Li, a non-radioactive tracer, was used to study the water transport pattern in 
LSD-affected coconut palms. The advantages of Li are its low cost, 
availability of simple analytical methods, and that it is measurable at very 
low concentrations (0.01 or even lesser). Moreover, Li occurs naturally in 
soils at very low concentrations, and when added to the soil it is taken up 
freely into the shoot system (Martin et al., 1982). Hence, the concentration of 
Li in different plant tissues, after application of Li, will be a measure of the 
 22
amount of Li as well as the amount of water that has moved into different 
tissues (Ranasinghe and Wijerathne, 2005). 
 
The experiment was conducted at Poththukuluma Research Station in the 
agro climatic region IL3. Thirty-year–old coconut palms, of the Tall variety 
(var. typica), uniformly managed as per recommendations of the Coconut 
Research Institute were selected for the study. Six palms each with mild-
LSD and moderate-LSD (as described in Ranasinghe, 2005) and apparently 
healthy palms were selected for the experiment. Palms that had advanced 
beyond the moderate stage of LSD were not selected for this study as their 
response to treatments was poor (unpublished data). A Randomized 
Complete Block Design with six replicates per treatment was used for the 
experiment. 
 
A sunny day (light intensity between 1200-1500 µmol m-2s-1) was selected 
for root feeding. A 100 ml of 1% LiCl solution was prepared for root feeding 
of palms. A mature, brown coloured, active root, growing at an angle of 
about 60o from the soil surface, was selected and prepared for root feeding. 
Only one root was selected for root feeding per palm assuming that all active 
roots were functioning equally well, and that a single active root is a 
representative sample. The root was severed with a smooth sharp cut and the 
cut end covered with moist cotton wool to prevent the entry of air bubbles. 
Immediately thereafter the root was inserted into a 1% solution of LiCl, 
contained in a polythene bag. The polythene bag with the LiCl solution was 
tightly tied to the root in a manner that ensures the cut end is always 
immersed in the solution, even when the solution level falls due to uptake.  
 
Three days after root feeding, leaf, nut and root sampling was carried out. 
Root samples were collected from the fed roots, and from untreated roots on 
the opposite side to determine lateral movement within the root system. The 
amount of LiCl taken up by roots was calculated by measuring the amount 
left in the bags. Leaf samples were taken from the 3rd, 6th, 9th, 14th, 18th and 
22nd fronds, and nuts were taken from the 5th, 8th and 12th bunches. Water of 
the harvested nuts was filtered using Whatman 42 filter paper, frozen at -20 
oC and stored until the Li concentration was determined. Leaflets, without 
the mid rib, husks, cut into small pieces, and the root samples were dried at 
80oC for three days and powdered using a Cyclotec (1093) plant sample 
grinder with 1 mm size sieve.  
 
 
 
 
 23
Determination of Li 
 
Ten milliliters of defrosted nut water was used to determine Li in the nut 
water. For the analysis of Li in leaf, husk and roots, 1 g each of the powdered 
sample was used. Samples were measured into 250 ml conical flasks, and 
after adding 20 ml of deionized water they were shaken for two hours and 
filtered using Whatman 42 filter paper. Li content in the filtrate and in 
defrosted nut water was determined (Ranasinghe and Wijerathene, 2005) 
using an Atomic Absorption Spectrophotometer (Shimadzu AA-6200, 
Japan). The Li concentration in a particular organ indicates the amount of Li 
that has moved into it, along with water, from the treated root. 
 
Analysis of Data 
 
Data was analysed by ANOVA, using the GLM procedure of SAS. 
 
RESULTS 
 
Determination of Li in Roots 
 
In healthy, mild-LSD and moderate-LSD palms, the Li concentration in 
treated roots (10-13 µg/g) was significantly higher than in untreated roots 
(0.05-0.2 µg/g). The high Li concentration in the treated roots of both 
healthy and LSD palms indicates that the uptake of water is not obstructed 
when it is supplied directly to the roots. However, the low concentration of 
Li in untreated roots shows that the lateral movement of water within the root 
system is restricted. In untreated roots, the highest concentration of Li was 
observed in mild-LSD palms (0.2 µg/g) while the lowest concentration in 
moderate-LSD palms (0.05 µg/g), whereas in the treated roots, the highest Li 
concentration was in moderate-LSD palms (12.56 µg/g), with appreciable 
concentrations in the mild-LSD (8.1 µg/g) and healthy palms (8.7 µg/g) (Fig 
1). 
 
 
 
 
 
 
 
 
 
 24
 
1a 
 
1b 
Treated
0
2
4
6
8
10
12
14
Healthy Mild Moderate
LSD disorder stages
Li
 C
on
c 
(u
g/
g)
Untreated
0
0.05
0.1
0.15
0.2
0.25
Healthy Mild Moderate
LSD disorder stages
Li
 C
on
c 
(u
g/
g)
 
Figure 1. : Li concentration in treated roots (1a) and untreated roots (1b) in 
healthy, mild-LSD and moderate-LSD palms, after root feeding 
with 1% LiCl. 
 
Determination of Li in nut water and husk 
 
Li content in the nut water and husk of healthy and LSD affected palms, was 
not significantly different in any of the maturity stages tested (5, 8 and 12 
months old nuts). The pattern of Li transport to nuts in healthy and LSD 
palms was similar, with the highest Li concentration of 0.03µg/g in the nut 
water of 5 month tender nuts), declining to 0.018-0.02 µg/g in the 8 and 12 
month nuts (Figure 2a). The inverse pattern was observed in the husk, with 
the lowest concentration of Li (0.015 µg/g) in the husk of 5 month nuts 
gradually increasing to 0.03 µg/g in 12 month nuts (Figure 2b). 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 25
2a. 2b. 
0
0.008
0.016
0.024
0.032
0.04
5M 8M mature
Age of nuts
Li
 C
on
c 
(u
g/
g)
Healthy Mild Moderate
 
0
0.01
0.02
0.03
0.04
5M 8M mature
Age of nuts
Li
 C
on
c 
(u
g/
g)
Healthy Mild Moderate
 
Figure 2: Li concentration in the nut water (2a) and husk (2b) of nuts of 
different age (5M=5 months, 8M=8 months and mature=12 
months), in healthy, mild-LSD and moderate-LSD palms, after 
root feeding with 1% LiCl 
 
Determination of Li in leaves 
 
The Li content in the leaves of healthy and LSD-affected palms, was not 
significantly different in any of the fronds tested (3rd, 6th, 9th, 14th, 18th and 
22nd fronds). The pattern of Li movement, and hence water movement to the 
fronds, was similar in healthy and LSD palms: a gradual increase up to the 
14th frond and declining thereafter. In all the fronds tested, the lowest 
concentration of Li in all ages of fronds was in the moderate-LSD palms 
while the highest concentration was in the mild-LSD palms, an interesting 
feature that merits further investigation (Figure 3). 
 
 26
00.04
0.08
0.12
3rd 6th 9th 14th 18th 22nd
Frond
Li
 c
on
c.
 (u
g/
g)
Healthy mild moderate
 
Figure 3: Li concentration in fronds of different maturity, in healthy, mild-
LSD and moderate-LSD palms, after root feeding with 1% LiCl 
 
DISCUSSION 
 
The gradual increase of Li concentration up to 14th frond and decline 
thereafter shows that the pattern of water transport in leaves, as measured by 
Li concentration, is in keeping with their physiological maturity. The 
demand for water of the younger fronds in the canopy is greater as they are 
physiologically more active than the mature fronds. This pattern of water 
transport was common to healthy, mild-LSD and moderate-LSD palms, 
showing that the demand of individual fronds has a greater bearing than the 
LSD status of the palms. However, in terms of the quantity of water 
transported, the leaf Li concentration, in all the fronds tested, was 
consistently lower in the moderate-LSD palms than in healthy and mild-LSD 
palms. This is suggestive of obstructions to water movement in moderate-
LSD palms.  It appears that while there are no obstructions to water 
movement in mild-LSD palms, restrictions to water transportation could 
develop as the disorder condition increases in severity. 
 
LI analysis shows that water movement into nut water behaves in a similar 
manner to that of fronds. The Li concentration in nut water is at a peak in the 
5 month tender nuts and decreases in the nuts of the more mature bunch 
indicating a greater movement of water to the tender nuts. Li concentrations 
in the water of 5 month tender nuts were nearly identical in healthy, mild-
LSD and moderate-LSD palms which indicates that water transport into the 5 
month nuts was not affected by the disorder. However, the somewhat higher 
 27
Li concentrations in the water of more mature nuts of healthy palms than in 
LSD-affected palms suggests that water movement into the nut water of LSD 
palms is restricted.  
   
The very high Li concentration in treated roots compared to untreated roots 
shows that lateral movement of water within the root system is limited. In the 
untreated roots, Li concentration was relatively high in healthy and mild-
LSD palms, and low in moderate-LSD palms, which suggests that while 
water movement is not affected in healthy and mild-LSD palms it is 
restricted in moderate-LSD palms. The accumulation of Li in the treated 
roots of moderate-LSD palms also supports this contention.  
 
The results of this study show that the uptake of water by the roots, and the 
pattern of water movement from the root system to crown tissues are not 
affected by the LSD disorder. However, the quantum of water moved up to 
the fronds is restricted in moderate-LSD palms possibly due to the presence 
of obstructions. Restrictions in the root system may at least partially account 
for the reduced water movement to the crown tissues in moderate-LSD 
palms. Water movement in mild-LSD palms is free of restrictions. The 
higher stomatal diffusive resistance in moderate and severe LSD palms and 
the increasing internal water deficit with the increasing severity of the LSD 
disorder, observed by Ranasinghe, 2005, support the present findings. 
Further studies on water transport patterns at different heights along the trunk 
would provide interesting information. 
 
As Li is not a plant nutrient, plant tissues are not a sink for Li. Therefore, 
higher levels of Li in the tissues indicate that a greater amount of water has 
moved into the plant parts. Although the Li concentration in roots of healthy 
and mild-LSD palms, in this study was less than of moderate-LSD palms, it 
was still a considerably high level. In a similar experiment to study the water 
transport pattern in palms affected by Coconut Rapid Decline, the Li 
detected was very much lower in the healthy roots, and higher in the canopy 
level tissues than in the present study (Ranasinghe and Wijerathene, 2005). 
These differences indicate the need for more investigations on the fate of Li 
in plant tissues and use of Li in water transport studies in LSD-affected 
palms, including the reasons for retaining large amounts of Li in roots of 
healthy and mild-LSD palms.  
 
 
 
 
 28
CONCLUSION 
 
Studies using Li as a tracer show that uptake of water into coconut roots, and 
the pattern of water movement from the roots to the crown tissues, are not 
influenced by the LSD disorder. However, in moderate-LSD palms water is 
retained in the roots, and the movement of water to the crown level is 
restricted.  
ACKNOWLEDGEMENT 
 
The financial assistance received from the Council for Agricultural Research 
Policy (Grant No. 12/537/408) is gratefully acknowledged. 
 
REFERENCES 
 
Davis, T.A. (1962). Coconut Withering Disease of Ceylon. Coconut 
Research Institute of Sri Lanka Bulletin, No.22. Lunuwila, Sri Lanka. 
 
Ekanayake, U.B.M. (1964). Annual Report of the Crop Protection Division, 
Coconut Research Institute of Sri Lanka (1963). Ceylon Cocon. 
Quart. 15, pp 50-57.   
 
Fox, R.L. and Lipps, R.C. (1964). A comparision of stable strontium and 32P 
as tracers for estimating alfalfa root activity. Plant and Soil, 20, 337-
350. 
 
Jayasekara, C. and Premasiri, R.D.N. (1989). Report of the Plant Physiology 
Division. Annual Report of the Coconut Research Institute, Sri 
Lanka, 175-179.  
 
Lipps, R.C. Fox, R.L. and Kochier, F.E. (1957). Characterizing root activity 
of alfalfa by radioactive tracer techniques. Soil Sci. 84: 195-204. 
 
Madurapperuma, W.S., Ranasinghe, C.S., Mendis, H., Premasiri, N., Seram, 
A., Gunawardena, M., (1994). Application methods of Zn and the 
effect of macro and micro nutrient applications on the expression of 
leaf scorch decline symptoms in coconut (Cocos nucifera L) In: 
Proceedings II; International conference, 75th Anniversary, Coconut 
Research Institute of Sri Lanka.  237-247 pp. 
 
 29
Mahindapala, R. and Chandrasena, A.M. (1975). Yield and drupe 
characteristics of coconut palms affected with Leaf Scorch Decline. 
Ceylon Coconut Quarterly 26:73-76. 
 
 Martin, M.P.L.D. Snaydon, R.W. and Drennan, D.S.H. (1982). Lithium as a 
non-radioactive tracer for roots of intercropped species. Plant and 
Soil. 64, 203-208.   
 
Nethsinghe,  D.A. (1966). The application of isotopes in fertilizer research 
on the coconut palm. Ceylon Coconut Quart. 17:61-72. 
 
Peries, O.S. (1968). Studies on Leaf Scorch Decline of coconut palms. 
Ceylon Coconut Quarterly 3: 109-115. 
 
Rajapaksha, C.N.K. and Fernando, L.C.P. (1995). Leaf Scorch Decline of 
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Lethal Yellowing-like Diseases of Coconut, Ghana 5-9 November 
1995., 97-104. 
 
Ranasinghe C.S. and Wijerathene, A.J. (2005). Vegetative, reproductive and 
physiological changes in coconut palms affected by Coconut Rapid 
Decline. Cocos 17, 01-10.  
 
Ranasinghe, C.S. (2005). Changes in the physiological performance of Leaf 
Scorch Decline (LSD) affected coconut (Cocos nucifera) palms. 
Experimental Agriculture 41, 255-265. 
 
 Ranasinghe, C.S., Wijesekara, R. and Wimalasekara,R. (2002). Rapid 
Decline Syndrome of Coconut (Cocos nucifera L.) - Preliminary 
report of a new condition. Palms 46:167-171. 
 
Vidanaarachchi, L and Nor, Y.M. (1994). Influence of palm oil sludge on 
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95-99. 
 
 
 
 
  
 30


A comparative study of water movement in leaf scorch decline attached and healthy coconut palms using lithium a non-radioactive tracer

Fernando, L.C.P.

Introduction of an electronic device to detect red weevil infested palms

Services offered by soils and plant nutrition division

Pathiraja, P.M.E.K.

Fernando, M.T.N.

Idirisinghe, I.M.S.K.

Subasinghe, S.D.J.N.

Exploring the potential for home-gardening of coconuts in urban and semi-urban areas of Sri Lanka-a case study

National Science Foundation of Sri Lanka

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