Method of determination of pear leaf area on linear measurements by calculation of correction factors and variation statistics approach

Morphological study of foliage in fruit crops are mainly conducted to study photosynthetic activity as related to leaf area. Currently, there are different methods to determine this parameter with varying accuracy. In the paper, we first compared the accuracy of assessing leaf area in pear by two methods based on a relationship between the leaf size (S) and its linear dimensions, the length (L) and the width (W). These ways were the use of a conversion factor (correction coefficient) and the regression analysis. The following 10 pear genotypes of different ripening were involved to measure the leaf linear parameters: Pirus communis L. - varieties Beurre Giffard, Vega (early ripening); varieties Williams, Chernomorskaya Yantarnaya (summer ripening); Beurre Bosk, Rassvet, hybrid ¹ 8520, Nart; Pirus serotina Rehd. - varieties Kilchu and Choo-chen-sok (autumn ripening). The correction by means of conversion factor was based on a similarity of the investigated leaf shape to relevant geometrical figure. Under this model, the leaf area calculation as S = 0.69 ½ (LW) was the most exact. This formula allows us to fast and exactly estimate the intact leaf size in pear trees and in other fruit crops with the same leaf shape to determine its changes throughout long time without destruction. Under the regression analysis procedure, the independent variables were L, W, L2, W2, and LW. Of these, the latter (LW) was optimum, resulting in a linear regression equation Y = 0,922581 + 0,660898 ½ (LW) based on which the MS Excel 7.0 program has been developed. This program allows us to find the sum of leaf areas or to determine an individual leaf area. Additionally, we found the indicators of leaf size and shape, and the averages for the sample, and also suggested graphics displaying leaf area. The scale for estimation was developed as a nomogram. Radial diagram with the special scale marked as area units against L and W units was also offered to simplify extensive research when more than 50-100 estimations required. Thus, due to close positive correlation between leaf linear dimensions and area, it is possible to practically apply conversion factor and regression equations, including developed nomogram and radial diagram, for calculation of leaf areas with the minimum error under natural conditions. The developed models may be helpful to measure area of oval, ovoid and unlobed leaves in southern fruit crops (e.g. apple, pear, cherry, plum), subtropical crops (citrus, feijoa, persimmon, tea), and ornamental wood bushes and grassy plants used for landscape gardening. Computerized technology promotes acceleration and simplification of the calculations.