COMPARISON OF LEAF-CLIPPING AND LEAF-PIERCING TECHNIQUES AS APPLIED TO THE SEAGRASS SYRINGODIUM FILIFORME

摘要

Leaf elongation rates of the seagrass Syringodium ftliforme (Kuetz., 1860) were assessed at two sites in a subtropical lagoon of Texas on eleven occasions from January 1996 to April 1997 using two methods, clipping and leaf piercing (marking) to estimate leaf growth. Pierced shoots grew at a significantly faster rate than clipped shoots irrespective of site. Clipping underestimated leaf elongation by 30%-38%, although differences at individual sites were as high as 69%-72%. Underestimation of leaf growth rate derived by clipping could be corrected using a site-specific linear regression relationship between leaf growth rates determined by clipping and piercing methods. The percent difference in overall leaf growth rate during the 14-mo study was 55% (4.47 mm d~(-1) pierced vs 2.44 mm d~(-1) clipped leaves). Fastest growth occurred during summer with rates of pierced leaves ranging from 8 to 11 mm d~(-1), which was generally two to three times that of clipped leaves. Highest leaf growth rates for clipped leaves never exceeded 4 mm d~(-1), regardless of site. We suggest that use of the leaf-clipping method in S. filiforme is appropriate when leaf growth rates are to be compared among sites or treatments and when true growth rate values are not critical.