We explored the C-value between the ecologically contrasting slopes at the “Evolution Canyon”, lower Nahal Oren, Israel.

Measurements were done by DAPI flow cytometry at the Department of Botany, Masaryk University in Brno under supervision of RNDr. Petr Bureš, PhD.

We found significantly more DNA in adult trees growing on the more illuminated, warmer, drier, microclimatically more fluctuating south-facing slope than in trees on the opposite, less illuminated, cooler and more humid, north-facing slope in spite of an interslope distance of only 100 m at the canyon bottom and 400 m at the top (Figure 1). In addition, the amount of DNA was significantly negatively correlated with the leaf length and tree circumference.

 

The most probable reason for the interslope differences is, in our opinion, the operating natural selection. In fact, the results do not fit with the expectation of the nucleoskeletal theory suggesting that nuclear size is selected to meet the needs of the cells for balanced growth. Contrary to the expectation of the nucleoskeletal theory the leaf cells are smaller at SFS but contain more DNA in comparison with NFS where leaves are bigger and contains smaller amount of DNA.

As a byproduct of our investigation we reported naturally occurring triploids and tetraploids of Ceratonia siliqua. For more details, see Bureš et al. (2004)