Reply to Schnyder, Kavanova and Nelson

We agree with Schnyder et al. (2009) that “Cell division rates cannot be estimated with the continuity equation if independent measurements of displacement velocity and cell length distribution are not available”. To our knowledge, there is still a lack of information on the effect of salinity on the cell division rate in the division zone of grass leaves in published reports. Based on the study of the salt effect on the epidermal cell number in the mature wheat leaves (Hu and Schmidhalter 2007), the results showed that, depending on the cell types, the total cell number in the abaxial epidermis was reduced by 16–23%. However, the estimation from a study on the leaf elongation and final cell length in the leaf of wheat under saline conditions showed a reduction in cell production by about 6% (Hu and Schmidhalter 2008). To measure the cell division rate in the cell division zone of grass leaves, Schnyder et al. (2009) have suggested that “Since the information on growth rates in the meristem is so difficult to obtain, the alternative approaches all depend on the measurement of some cell division marker, which can be grouped in two categories: (i) those that assessed average division rates of cells in the meristem (e.g. Fiorani et al. 2000; Kavanova et al. 2006) and (ii) those that also resolved the spatial distribution of cell division rates in the meristem (Beemster et al. 1996).”

(Handling editor: Jinxing Lin)