The line intersection method to estimate total foliage length in Potamogeton pectinatus L.

A non-destructive line intersection method, earlier used to measure total l ength of roots of terrestrial plants, is described to estimate the total fo liage length of individual plants of Potamogeton pectinatus L. Plant foliag e was spread over an acrylic plate, and copied using a photocopier. Photoco pied stems and leaves that intersected horizontal and vertical lines of thr ee sizes of transparent grids (1 cmx1 cm, 2 cmx2 cm, 3 cmx3 cm) were counte d, added and multiplied by a conversion factor (F: 0.0078, 0.0158 and 0.023 3 m per intersection for the three grid sizes, respectively) to obtain tota l foliage length (in meters). Estimates obtained using the line intersectio n method and measurements of actual length made using an opisometer were si gnificantly correlated (p<0.001; minimum r(2)=0.992). The regression parame ters alpha (Y-intercept) and beta (slope) for the 3 cmx3 cm grid size did n ot differ significantly from zero and one, respectively (p>0.25). Estimated values (+/-S.E.) were 0.19m (+/-0.22) for the Y-intercept, and 0.99 (+/-0. 01) for the slope. From the results obtained, it can be concluded that the line intersection method using a 3 cmx3 cm grid is a workable alternative t o estimate total foliage length in fine-leaved and branched plants, owing t o its high precision and accuracy, and the short time required for preparin g and measuring the plant material. (C) 2000 Elsevier Science B.V. All righ ts reserved.