Abstract:
The decline in availability of fresh water in the region of Ierapetra, Crete, Greece
has resulted in the increased use of saline water for irrigation of greenhouse crops.
The aim of this work is to study the responses of four greenhouse pepper hybrids, that
are widely used in this region ( Capsicum annuum L., Drago, Sammy, Kappy and
Gracia ), to NaCl salinity during in hydroponic culture ( perlite ) and culture in soil of
young plants and during in vitro germination and seedling growth. Salinity treatments
were imposed by adding NaCl either to the irrigation solution, or the substrate of the
in vitro culture, at concentrations of 0, 12.5, 25, 50, 100, 150, 200 mM. High
concentrations of NaCl affected the growth of the plants in hydroponic culture and in
soil culture and the growth of seedlings in vitro in all four hybrids. Growth parameters
such as height, number of leaves, fruits and flowers per plant and plant weight were
significantly reduced in all hybrids. The percentage germination in the in vitro culture
of the seeds was 100% for all hybrids on all NaCl concentrations.
The photosynthetic rate (Po), the stomatal conductance, the intercellular CO2
concentration and the transpiration were significantly affected at high concentrations
of NaCl in Drago and in Sammy. The Fv/Fm values of the leaves, which are related
to the chlorophyll fluorescence, were significantly reduced at 100-200 mM NaCl,
more in Kappy and Gracia and less in Drago and Kappy. The chlorophyll content in
the leaves was negatively affected in all hybrids.
NaCl caused a decrease in the soluble proteins in all hybrids. The decrease was
significant in Drago, Kappy and Gracia in the greenhouse experiment while in vitro
the protein content was less affected by the increasing concentrations of NaCl.
Soil salinity positively affected the activity of GDH at 100 mM to 200 mM NaCl
more in Kappy and Gracia and less in Sammy and Drago. In the vitro experiments
there was a small increase in the higher concentrations of salt in all hybrids.
The presence of NaCl affected the antioxidant enzyme GPX in Sammy Kappy
and Gracia, SOD in Drago and POD in Kappy while APX was not affected.
In general Sammy was the least affected by NaCl followed by Kappy , Drago,
and Gracia.