Kularatne, J.D.J.S.

Mathes, D.T.

Ranasinghe, C.S.

Silva, L.R.S.

Coconut Research Institute Repository

cocos (2000-2002), 14 1-5Prillted ill Sri LankaA NON-DES.TRUCTIVE METHOD FOR DETERMINING THE AREA OFUNSPLIT LEAVES OF COCONUT SEEDLINGSC S RANASINGHE, D T MATHES, L R S SILVA AND J D J S KULARATNECoconut Research Institute, Lunuwila, Sri LankaABSTRACTA rapid, non-destructive and accurate method for determining the leaf areaof unsplit leaves of coconut seedlings (var. CRIC 60 and CRIC 65) isproposed using two regression models y =25.85 + 0.99 x (for CRIC 60) andy = 38.36 + 1.04 x (for CRIC 65) with reliabilities of 99.3% and 96.9 %,respectively, where y is the area of the leaf and x = (c + d) {(e + ...j (f 2 + 9 2 /4)) /2}, c, d, and g are the breadths while e and f are lengths at differentpositions of the leaf.INTRODUCTIONLeaf is the major plant organ responsible for photosynthesis, transpirationand consequently, the total plant productivity (Linder, 1985). Therefore, it isof utmost importance to study the leaf area development of a plant. Thevigor of a coconut (Cocos nucifera L.) seedling is also to some extentindicated by the length and width of a leaf and the number of leaves. Theseparameters are in effect related to the total leaf area of a seedling. Instudies done by the plant physiologists, botanists and agronomists, leaf areaof a young coconut seedling is frequently used as an index of the plant'sresponse to environmental changes (Ranasinghe et al., 1999).Coconut seedlings are often used in research studies. Very often destructivesampling is not possible. For such situations, the most common method ofdetermining the leaf area is by mathematical regression equations usingeasily measurable leaf parameters. Several acceptable non-destructivemethods are available for determining the leaf area of split leaves in coconutseedlings (Mathes et al., 1989; Satheesan et al., 1983) and adult coconutpalms (Jayasekara and Mathes 1992; Ramadasan and Jacob Mathew(1987). However, a method to determine the leaf area of seedlings withunsplit leaves in which the leaflets are not separated is yet to be developed.Hence it has become necessary to find a method of estimating the leaf areaof such seedlings by a non-destructive method. 'There is a large variation in the morphology of leaves among the cultivarsand hybrids of coconut (Ramadasan and Kasturi Bai , 1999). Th is maynecessitate developing different regression equations to determine the leafIarea of seedlings of Tall and Dwarf -Green x Tall varieties. The aim of thisstudy wa·s to develop a common equation or different equations to estimateleaf area of unsplit leaves of seedlings of Tall Dwarf Green x Tall varieties .MATERIALS AND METHODSEight-month-old seedlings from Tall x Tall (CRIC 60) and Dwarf Green x Tall(CRIC 65) varieties were randomly selected for the study from two coconutnurseries, Kirimatiyana and Thabbowa. From each nursery, 15 seedlings ofeach variety were selected and six unsplit leaves from each seedl ing weretaken for measurements. The most mature leaf of each seedling wasnumbered 1 and the other leaves were numbe red in the descending orde r ofmaturity. Measurements were taken at different posit ions of each leaf inorder to develop a suitable equat ion to estimate the total area of a unsplitleaf. The measurements finally used for the development of the mostefficient regression equation or equations were c, d, e, f and g (Fig. 1).Fig. 1: Diagram of an unsplit leaf showing the measured parameters c. d, e,f and g.The model takes the form ;Where, Yi is the actual area of the leaf and Xi to describe later , a and bareconstants. The actual area of each leaf was measured destructively usingan electronic leaf area meter (L1-COR 3000 , USA).2Statistical analytical procedureConsider the area ABC of the unsplit . leaf in Fig. 1. This area is bestdescribed as proportional to one half the area def ined by,c {(AB +BC) 12}ie; c {{AB +BC) 12}= c {(e + " (f 2 + e 2/4)) 12}.Similarly the area of ABO is proportional to, d {(e +" (f 2 + g2/4)) 12}Thus the total area x = (c + d){(e + " (f 2 + g 2/4)) 12}Let x = (c + d) {(e +"(f 2 + g 2/4)) 12)Let y = the actual leaf area of each leaf measured by leaf area meterThus for each leaf, the leaf area (Yi) and calculated value (Xi) will beavailable and the regression equation developed accordingly.RESULTSSeparate regression equations were developed for the varieties CRIC 60and CRIC65 and are described below .CRIC 60 : y =25.85 + 0.99 x,CRIC 65 : y =38.36 + 1.04 x,Where y = actual leaf areax = (c + d) {(e + " (f 2 + g 214)) 12}r2 =99.3%r2 =96.9 %The regression coefficients showed significant (p=0 .001) dependency of yon x. The high r2 values indicate the prediction value of the two equationsand the extent to which the variation in y is explained by x.A further test was carried out to see whether a common equation could befitted for the two var ieties. The test however showed that there is asignificant difference between the 'a ' values and the 'b' values. Thissuggests that leaf area of the seedlings of the two varieties is best describedby the two regression equations.3DISCUSSIONLeaves are the most important organs for plant production due to the ir rolein intercepting and absorbing radiant energy and building this energy intoorganic substances through the processes of photosynthesis. Thephysiological aspects such as rates of photosynthesis and transpiration of aplant are commonly expressed as CO2 uptake and H20 loss per unit leafarea. The value of leaf area in the study of plant growth and otherphysiological aspects is so significant that researchers from time to time hadtried various methods in evaluating the leaf area of coconut seedlings bynon-destructive methods. Mathes et al (1989) developed a regressionequation to est imate area of the leaves of coconut seedlings up to threeyears of age and observed that the third leaf could be used as therepresentative leaf to measure the total leaf area of seedlings. However ,their method could not be applied for seedlings with unsplit leaves. Basedon results of the present study, the following non-destructive method couldbe proposed for obtaining the area of the unsplit leaves of seedlings in the'field planting stage'. The measurements of c, d, e, f and g of each unsplitleaf have to be taken , irrespective of the age of the leaf, and used in theequation developed to estimate the area of each leaf. Total leaf area of theseedling can thus be estimated by adding individual leaf areas.In conclusion , the equations developed from this study could be used todetermine the leaf area of unsplit leaves of Tall and Dwarf Green x Tallseedlings and applied to studies of growth analysis and in the evaluation ofcultivars at the seedling stage for the ir potential to adopt to differentenvironmental conditions.REFERENCESJayasekara C and Mathes D T (1992) . A method to determine leaf area ofa frond and the whole canopy of an adul t coconut palm . Indian CoconutJournal 23, 7-13.Linder S (1985) Potential and actual production in Australian forest stands.In: Landsberg J J, Parson W (Eds.) Research for Forest Management,CSIRO, Melbourne, 11-35 .Mathes D T, Liyanage L V K, Randeni G (1989). A method fordetermining leaf area of one, two and three year old coconut seedl ings (var .CRIC60). Cocos 7,21-25.Ramadasan A, Jacob Mathew (1987). Leaf area and dry matterproduction in adult coconut palms. Journal of Plantation Crops 15 (1), 59-63.4Ramadasan Ii., Kasturi Bai K V (1999). Leaf area, dry matter productionand yield. In: Advances in plant physiology and biochemistry of coconutpalm (Eds. Rajagopal V and Ramadasan A). Publisher APCC, PP 30-35.Ranasinghe C S, Weerakoon L K, Liyanage Y M H, Mathes D T (1999) .Physiological aspects of in vitro-grown coconut (Cocos nucifera L.) plantsduring acclimatization. CORD XV (2),46-67.Satheesan K V, Narasimhayya G, Ramadasan A (1983). A rapid methodfor estimation of leaf area of one-year-old seedlings of tall variety of coconutpalms. Journal of Plantation Crops 11 (1), 47-49.5

A non-destructive method for determining the area of unsplit leaves of coconut seedlings

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A non-destructive method for determining the area of unsplit leaves of coconut seedlings

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