Non-destructive mathematical models to estimate leaf area in noni ( Morinda citrifolia )

Noni is one of the most economically and medicinally important species of the family Rubiaceae grown in tropical countries. The leaf area (LA) estimation is important to understanding light interception, which regulates physiological processes such as respiration, transpiration, photosynthesis, nutrient usage and mobilisation. Elliptic to elliptic-ovate shaped noni leaves were observed in different sizes-small (surface area < 228 cm 2 ), medium (228–346.4 cm 2 ) and large (> 347 cm 2 ). Reliable and accurate mathematical models for estimating the leaf area of noni were developed that were based on non-destructive measurements of midrib length (ML) and maximum leaf width (MW). A significant positive correlation between maximum width and midrib length r = 0.993 and S = 0.123 was observed. Maximum correlation coefficient ( r = 0.999) and minimum standard error (S = 0.200) were observed in estimated leaf area based on maximum width and measured leaf area. This finding revealed that the estimated leaf area from maximum width is superior to the estimated leaf area with the help of midrib length. The developed models estimated the leaf area of small, medium, and large leaves of noni accurately. This non-destructive mathematical model is low in cost, accurate and fast to estimate leaf area for the understanding of light interception and management of nutrients for healthy plant growth and development.