Madras Agric. J., 96 (1-6): 113-115, June 2009

Short Note

Estimation of Total Leaf Area by Non-destructive Methods in Horse-eye Bean, Mucuna pruriens Ga. Dheebakaran* and R. Jagannathan Agro Climate Research Centre, Tamil Nadu Agricultural University, Coimbatore-641 003 A simple, accurate, time saving and non destructive method of leaf area determination for Mucuna pruriens, a medicinal plant, was made at Tamil Nadu Agricultural University, Coimbatore, India. The results revealed that irrespective of stages, the third leaf from the top has high correlation with total leaf area of the plant. It was further observed that the area of the middle leaflet had significant relationship with total area of trifoliate leaf. The correction factors to find out the total leaf area of a plant from the leaflet area measurements were also worked out. The correction factor of 0.74 could be used for the leaflet area using length and breadth of middle leaflet and 0.96 has to be used when the same was found out using leaf area meter. The middle leaflet area of the third leaf from the top has to be multiplied with correction factor and number of leaves to get total leaf area of the plant. Key words: Leaf area, trifoliate leaf, nondestructive, velvet bean, mucuna

Mucuna pruriens (L.) DC. is a climbing legume with long, thin branches and opposite, lanceolate leaves of 15 to 30 cm in length and produces 2-3 racemose flowers. Leaf area production is essential for energy transfer and dry matter accumulation in crop plants through photosynthetic activity which decides final yield of a crop. Measuring leaf area is also useful in the analysis of canopy architecture as it allows determination of leaf area index, which is important for light interception, radiation use efficiency, plant growth, etc. Although many methods are available for leaf area measure ments, the use of leaf area as a variable in plant growth analysis and physiological studies is limited owing to the cumbersome process involved in its measurement. The use of sophisticated electronic instruments provides accurate and fast leaf area measurement, its availability in developing countries is rare phenomena. This warrants development of economically cheaper and technically easier but sound method for leaf area measurement (Korva and Forbes, 1997). Simple, accurate, and

*Corresponding author email: [email protected]

nondestructive methods of determining leaf area of plants are important for many experimental comparisons. Montgomery (1911) first suggested that leaf area of corn plant can be calculated from linear measurement of leaves using a general relationship A = b × L × W where b is a coefficient (A=area, L=Length, W=Width). Such a mathematical equation for estimating leaf area reduces sampling effort and cost, likely to increase precision where sample of leaf size are difficult to handle. The leaves of Mucuna pruriens are alternate, pinnately trifoliate, distant, and oblong petioles; leaflets entire, ovate, acute, smooth above, hairy beneath; lateral ones oblique at the base, middle one slightly rhomboidal. Thus it is very difficult to measure the leaf area and literature review in this regard also indicated non availability of techniques for estimation of leaf area through nondestructive methods. Therefore, in the present investigation an attempt was made to develop a simple technique which is accurate and time saving for leaf area estimation of Mucuna pruriens.

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Materials and Methods A trial was conducted in the eastern block of Tamil Nadu Agricultural University, Coimbatore, India during August 2003 to December 2004 under irrigated condition. The mucuna seeds were planted in ridges with a spacing of 60cm between ridges and 30 cm between plant to plant. Observations were made on randomly selected 10 plants per replication during each observation at 15 days interval. The length (L), width (W) and real leaf area of middle leaf let (RLAm) of 2nd,3rd,4th and 5th trifoliate leaf , real leaf area of whole plant (RLAw) and total number of trifoliate leaves plant-1 (N) were recorded. Leaf length (cm) was measured along the lamina midrib, from the point of lamina attachment to the tip, and leaf width (cm) was

measured perpendicularly to lamina midrib, from edge to edge at the widest part of the lamina. The real leaf area (RLA) was determined with a Deccan leaf area meter (LAM) calibrated to 1.0 cm2. Following equations were used to calculate the leaf area per plant (LAc). L*W method (LAc) = L x W x 3 x N LAM method (LAc) = RLAm x 3 x N (+ Since leaf is trifoliate, the area of leaf let is multiplied by three to get single leaf area) For the calculation of correction factor (CF) following equation was used CF = RLAw /LAc Results and Discussion The observed and calculated data of the experiments are presented in Table 1. The result

Table 1. Development of correction factor for total leaf area plant -1 of Mucuna pruriens

Growth Stage

Leaf No. Length from the (cm) top

Width LAM Calculated Leaf Correction factor (cm) (cm2) area (cm2) (cf) LxB

30 DAS

45 DAS

60 DAS

75 DAS

90 DAS

LAM

LxB

LAM

2 5.6 4.2 16.1 1259 871 1.81 2.61 3 9.8 6.2 43.1 3289 2325 0.69 0.98 4 10.1 6.7 47.2 3683 2549 0.62 0.89 5 10.0 6.8 46.2 3663 2494 0.62 0.91 Total No. of Leaves =18 Real leaf area of whole plant = 2276 cm2 2 5.6 4.3 16.3 2923 2002 1.65 2.41 3 9.4 5.7 43.1 6637 5289 0.73 0.91 4 9.6 6.2 47.1 7353 5789 0.66 0.83 5 10.0 6.1 49.0 7447 6019 0.65 0.80 Total No. of Leaves =41 Real leaf area of whole plant = 4832 cm2 2 5.0 3.1 11.0 3811 2694 2.39 3.38 3 8.6 5.6 38.0 11799 9338 0.77 0.98 4 9.5 5.9 42.9 13714 10547 0.66 0.86 5 9.7 6.0 44.3 14172 10891 0.64 0.84 Total No. of Leaves =82 Real leaf area of whole plant = 9112 cm2 2 6.9 4.3 21.2 9920 7049 1.37 1.93 3 9.1 5.7 42.1 17284 14010 0.79 0.97 4 10.1 5.7 46.4 19228 15451 0.71 0.88 5 9.9 5.7 46.7 18962 15552 0.72 0.88 Total No. of Leaves =112 Real leaf area of whole plant = 13628 cm2 2 5.3 3.7 14.2 7927 5710 1.87 2.60 3 8.9 5.6 39.2 20026 15742 0.74 0.94 4 9.1 5.6 40.8 20631 16422 0.72 0.90 5 9.3 5.9 41.5 21970 16675 0.68 0.89 Total No. of Leaves =134 Real leaf area of whole plant = 14861 cm2

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indicated the usefulness of LxW method for in situ measurements of leaf area that is inexpensive, simple and precise as being followed in may other crops elsewhere. Estimations using L and W showed good relationships with Leaf Area of plant, which demand less effort and time at field as it involved single dimension measurement. Accurate and simple mathematical models thus eliminate the need for leaf area meters or time-consuming, geometric reconstructions (Gamiely et al., 1991). The non-destructive methods based on linear measurements as described here are quicker and easier to be executed and present good precision for the study of plant growth in several crops (Silva et al., 1998; Guo and Sun, 2001). Table 2. Stagewise correction factor for calculating total leaf area -1 of Mucuna pruriens for 3rd leaf from top.

Days after sowing

Where, N is total number of leaves plant-1; L,W and LAM are length, width and leaf area meter reading of middle leaflet of 3rd trifoliate leaf from top. The XLW and XLAM are correction factor for L x W method and LAM method. The correction factors for different stages of the crop as well as for the entire crop period are furnished in Table 2. Irrespective of the stages of the crop the correction factor is close to one for leaf area meter method while in L x W method it is around 0.75. Conclusion It is concluded that irrespective of stages, the third leaf from the top has high correlation with total leaf area of the plant and the area of middle leaflet had significant relationship with total area of the trifoliate leaves in velvet bean. Reference

Correction factor LW

LAM

30 DAS

0.69

0.98

45 DAS 60 DAS 75 DAS 90 DAS <60 DAS >60 DAS

0.73 0.77 0.79 0.74 0.71 0.77

0.91 0.98 0.97 0.94 0.95 0.96

Grand Average

0.74

0.96

The result concluded that for mucuna middle leaflet of 3rd leaf from the top had absolute value nearer to actual total leaf area plant-1 and could be used as reference leaflet for measuring total leaf area of the whole plant, irrespective of stages and methods similar to the index leaf in many other crop for this purpose. The correction factors for the total leaf area plant-1, for entire crop duration are 0.74 and 0.96 for Length x Width (LxW) and Leaf Area Meter (LAM), respectively. The simple prediction equations for total leaf area plant-1 (TLA) are TLALW

= N x L x W x 3 x XLW

TLALAM

= N x LAM x 3 x XLAM

Gamiely, S., Randle, W.M., Mills, H.A. and Smittle, D.A. 1991. A rapid and nondestructive method for estimating leaf area of onions. Hort. Sci., 26: 206. Guo, D.P. and Sun, Y.Z. 2001. Estimation of leaf area of stem lettuce (Lactuca sativa var angustana) from linear measurements. Indian J. Agric. Sci., 71 : 483-486. Montgomery, E.G. 1911. Correlation studies in corn. Annual report 24, Nebraska Agricultural Experiment Station, Nebraska, p.108-159. Korva J. T. and Forbes, G. A. 1997. A simple and low cost method for leaf area measurement of detached leaves. Exp. Ag., 33: 65–72. Silva, N.F., Ferreira, F.A., Fontes, P.C.R. and Cardoso, A.A. 1998. Modelos para estimar a área foliar de abóbora por meio de medidas lineares. Revista Ceres, 45: 287-291.

Manuscript number

:

73/08

Date of receipt

:

May 23, 2008

Date of acceptance

:

May 27, 2009