Estimation of leaf area in selected Hypericum species

The genus Hypericum has attracted scientific interest for recent years, since it is a source of a variety of compounds including hypericin. The present study was conducted out to develop leaf area prediction models for some Hypericum species containing hypericin, namely H. pruinatum, H. perfoliatum, H. aviculariifolium subsp. depilatum var. depilatum (endemic), H. montanum, H. montbretii, H. linarioides, H. triquetrifolium, H. bithynicum and H. perforatum growing wild in Northern Turkey. Lamina width, length and leaf area were measured without destroying to develop the models. The actual leaf areas of the plants were measured by Placom digital planimeter, and multiple regression analysis with Excel 7.0 computer package program was performed for the plants separately. The produced leaf area prediction models in the present study were formulised as LA = (a) + (b 1 × L) + [b 2 × (L × W)] + (b 3 × L 2 ) + (b 4 × W 2 ) + [b 5 × (L × W 2 ] + [b 6 × (L 2 × W)] + [b 7 × (L 2 + W 2 )] where LA is leaf area, Wis leaf width, L is leaf length and a, b 1 , b 2 , b 3 , b 4 , b 5 , b 6 , and b 7 are coefficients. R 2 values varied with species from 0.80 in H. aviculariifolium subsp. depilatum var. depilatum to 0.97 in H. pruinatum . All R 2 values and standard errors were found to be significant at the p < 0.001 level