Coconut Research Institute Repository

Jayasinghe, J.A.A.K.

Marikkar, J.M.N.

Jayasundra, J.M.M.A.

Gajanayake, K.G.M.C.P.B.

Exploring constraints and motivations of HACCP adoption in the virgin coconut oil and white edible copra industries of Sri Lanka

Jayalath, K.V.N.N.

Jayasinghe, U.K.

Fernando, M.T.N.

Price and production risk in coconut industry in Sri Lanka:a comparison with the leaders in the world market

Jayathilake, R.

Perera, L.

Coconut seedling certification:a move from CRI to ensure growers good quality coconut seedlings

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 
coconut in Sri Lanka in Proceedings on International Workshop on 
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 
physical properties of soil and growth characterization of oil palm 
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95-99. 
 
 
 
 
  
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National Science Foundation of Sri Lanka

Not a member yet

Exploring constraints and motivations of HACCP adoption in the virgin coconut oil and white edible copra industries of Sri Lanka

Price and production risk in coconut industry in Sri Lanka:a comparison with the leaders in the world market

Coconut seedling certification:a move from CRI to ensure growers good quality coconut seedlings

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

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

Is required water available for coconut cultivation in North Western province

Microbiological methods of Biomass C, Biomass N, Microbial Activity and net n mineralization

Impact of the coconut mite (Acerria guerreronis keifer) on the coconut industry in Sri Lanka

Influence of environmental factors on seed germination and emergence of Chromoleana odorata in coconut plantations in Sri Lanka

Exploring constraints and motivations of HACCP adoption in the virgin coconut oil and white edible copra industries of Sri Lanka

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