Determination of leaf fresh mass after storage between moist paper towels: constraints and reliability of the method

To ensure comparability among leaf fresh mass measurements it is important to handle the leaves in a standardized manner. In the present work constraints of a commonly used method to achieve full turgor, storage between damp paper towels, were investigated. After overnight rehydration in a saturated atmosphere, the fresh mass of leaves of 14 species was measured, and the leaves were stored between paper towels (two treatments: moist and wet) at 4 degrees C. Their mass was measured after 24, 48, and 72 h. Leaf fresh mass increased during the first 24 h of storage between moist paper towels by an average of 1.8%, between wet towels by 3.3%. Among the species, the increase of leaf fresh mass between moist towels correlated with the species' desiccation propensity, indicating that it was rehydration from water loss during initial handling. On the other hand, between wet towels the fresh mass increase was associated with the species' leaf tissue structure, and it continued to increase beyond 24 h, indicating that the increase was a result of water penetration into the leaf air spaces. It is concluded that storage between moist paper towels results in reliable values of leaf fresh mass, and that desiccated leaves rehydrate well between moist towels. However, care has to be taken to avoid too wet conditions as they may lead to erroneously high fresh mass values, especially in species with large air spaces. Furthermore, exposure to unsaturated atmospheric conditions during handling has to be minimized.