Leaf area prediction in two Quercus species: validation of the Montgomery equation under bilateral asymmetry

Key message : The Montgomery equation accurately estimates leaf area in two Quercus species using either midrib-based or conventional leaf length measurements, even under bilateral asymmetry. 

Abstract: Estimation of leaf area is crucial for assessing photosynthetic potential and light interception in plants. The Montgomery equation (ME), which assumes a proportional relationship between leaf area (A) and the product of leaf length (L) and width (W), i.e., A ∝ LW, is widely used, but its validity under leaf bilateral asymmetry requires further testing, particularly when using a midrib-based length definition. Using over 300 leaves each from Quercus acutissima and Q. chenii, we compared a midrib-based approach (curvilinear midrib length as L, and maximum width perpendicular to the midrib tangent as W) with the conventional approach (straight-line distance from leaf apex to base as L). Leaf asymmetry was quantified using two indices. Quercus chenii exhibited significantly greater bilateral asymmetry than Q. acutissima (p < 0.05). Both methods predicted leaf area accurately, with mean absolute percent errors (MAPE) below 5%. The midrib-based approach showed slightly better statistical performance, but the conventional approach remained highly accurate. The ME is valid for estimating leaf area in asymmetric leaves. The conventional approach is recommended for its practicality and sufficient accuracy in field applications.