ArticleThe peculiarities of CO2 exchange in the leaves of ornamental evergreen plant species
that are common in the Southern coast of Crimea were studied: Nerium oleander L., Laurus
nobilis L., Aucuba japonica Thunb., and Melissa officinalis L. The results of approximation of
the most commonly used four models of PN/I curves with the measured data were compared. The
values of the parameters , (), , , which were calculated from the modified
Michaelis-Menten model in comparison with the measured values were higher by 5–15%, and
those that were calculated by the hyperbolic tangent model – lower by 3–13%. The use of a
modified rectangular hyperbola model, which is capable of describing the photoinhibition by the
nonrectangular hyperbola and the modified nonrectangular hyperbola model, showed a high
degree of adequacy of the proposed models for describing the true dependence between the rate
of photosynthesis and the light intensity for Nerium oleander L., Laurus nobilis L., Aucuba
japonica Thunb. and Melissa officinalis L. Measurements of CO2 exchange in leaves under
similar environmental conditions showed significant differences in the parameters of the PN/I
curves: the light compensation point, the rate of photosynthesis and dark respiration, light
saturation, and quantum yield. The highest values of photosynthesis efficiency were observed in
Nerium oleander, the lowest values in Aucuba japonica – the light saturation was noted at a very
low photosynthetically active radiation. The lower values of the light compensation point and the
saturation constants in Laurus nobilis and Aucuba japonica indicate their effective use of the
photosynthetically active radiation, which allows them to survive in conditions of durable shade
