Estimation of Leaf Area of Two Grapevine Cultivars (Vitis vinifera L.) Using Laminae Linear Measurements and Fresh Weight

Abstract

Leaf area (MLA), measured with a leaf area meter, of potted Chardonnay and Chenin blanc grapevines grown inside a greenhouse (no heat stress) and phytotron (heat stress), was correlated with leaf length (L), width (W), product of length and width (LW) and fresh weight (FW) of the laminae to establish an equation that best estimates entire vine leaf area. LW gave the highest correlation coefficient (r), followed by FW. With both cultivars, linear equations calculated with LW as the independent variable, had the highest coefficient of determination (R²) and smallest standard error of estimate. No significant differences (t-test, p>0.01) between the two experimental sites was found when comparing corresponding equations for each cultivar. New equations using the combined greenhouse and phytotron data were calculated and used to predict leaf area (PLA) for the heat stress experiment; for Chardonnay and Chenin blanc the equations were respectively: PLA = 3.17 + 0.69 WL (R² = 0.9892; standard error of estimate (SE) = 4.74 cm²) and PLA = 2.49 + 0.68 LW (R² = 0.9747, SE = 3.06 cm²). Linear equations using FW as the criterion for estimation of MLA was used to establish calculated leaf area (CLA). For each cultivar, two CLA's were determined; CLA(1) used average fresh weight of three leaf disks of known area sampled from six potted bearing vines of each cultivar grown in the greenhouse. A highly significant correlation was obtained between CLA's and MLA, indicating that when a leaf area meter is not available and non-destructive sampling is required, CLA can substitute for MLA. Linear equations using LW as the estimator of CLA(1) and CLA(2), gave similar R² values (96.3%) for both cultivars using CLA(1), and a slightly higher R² for Chenin blanc using CLA(2) (R² = 97.6%). Polynomial fitting of the data did not substantially improve the coefficients of determination compared to linear analysis.