IN VITRO grown potato cultivars shoots were used to understand
….. how polyvinyl pyrrolidone (PVP) and three levels of potassium
interact with two levels of salinity to determine Na+ and K+ contents,
and antioxidant enzyme activities leading to control survival,
multiplication and growth of cultured plant shoots. Explant survival
and the number of regenerants/explant decreased with the increase of NaCl
concentration but increased K+ content of the culture medium from 20
mM to 30 mM improved explants survival frequency and the growth
parameters estimated under relatively high salt stress (80 mM NaCl) in
both cultivars. Also, number of regenerants was influenced by K+ level
where it was higher in medium containing 40 mM NaCl and 30 mM
K+ than other cultured on the same NaCl concentration with 20 mM
K+. The positive effect of 30 mM K+ on the previous parameters was
associated with increase shoot K+ content leading to decrease Na+/K+
ratio and increase of some antioxidant enzymes (SOD, POX and CAT
in Agria or SOD, POX and APX in Hermes) activity, especially under
relatively high salt stress. PVP application increased K+ content and
activities of some antioxidant enzymes (CAT and APX) but decreased
Na+/K+ ratio of shoots subjected to relatively high salt stress in Agria
but under both salt stresses in Hermes. Consequently, sufficient
potassium supply was necessary to conserve low Na+/K+ ratio and
efficient scavenging system by antioxidant agent (PVP) application or
increase the endogenous antioxidant enzymes activities leading to
minimize the negative effect of salt stress on in vitro grown potato.