Evaluation of salinity stress on some photosynthetic characteristics in five Kochia (Kochia scoparia (L.) Schrad.) ecotypes

Background and objectives:
inFunction of the photosynthetic apparatus of halophytes plays an important role in their salinity tolerance. Kochia as a halophyte, is of high ability in biomass production in salinity stress conditions. Thus study photosynthesis and the related factors salinity stress can provide appropriate physiological view for better understanding of the plant mechanisms of in stress conditions. So a field experiment for evaluation photosynthesis and related factors at salinity stress in the real condition was done.
Materials and methods:
So an experiment was conducted as split-plot based on Complete Randomized Block Design with three replications to evaluate some photosynthetic characteristics of halophyte plant, Kochia scoparia, in different salinity levels at the Salinity Research Station of Ferdowsi University of Mashhad, Iran in 2009. Salinity as the main plot had two levels of 5.2 and 16.5 dSm-1 and five kochia ecotypes including Urmia, Isfahan, Borujerd, Birjand and Sabzevar were allocated as sub-plots.
Results:
Results indicated that increased salinity level had significant effect on stomatal conductance, transpiration and photosynthetic activity. With increasing levels of salinity from 5.2 to 16.5 dSm-1, stomatal conductance, transpiration rate and photosynthesis activity increased 29%, 0.41 mM.m-2 and 22.5% respectively. In the other hand increased salinity level had no significant effect on chlorophyll a, chlorophyll b, carotenoids content, spad, Ci, quantum yield of photosystem II, biomass, water use efficiency and potassium and sodium concentration in leaf and stem. There were significant effect observed between ecotypes in water use efficiency and potassium and sodium concentration in leaf and stem. Urmia and Borujerd with 52.7 percent different respectively, minimum and maximum in stem sodium and 75 percent different respectively had highest and lowest in leaf sodium. Interaction between salinity levels and ecotypes showed the significant effect only in stomatal conductance and water use efficiency. Stomatal conductance increasing in all ecotypes, except of Sabzevar ecotype with increased salinity, this rate of increase in Birjand, Borujerd and Urmia, ecotypes respectively 64.9, 39.0, 38.8 and 13.0 percentage. water use efficiency increased by increasing salinity in Urmia and Boroujerd ecotypes and in other ecotypes, this trend were decline and Isfahan ecotype has highest decline rate. Significant correlation observed between chlorophyll a with chlorophyll b, carotenoids and total pigments in 5.2 dSm-1. Among the photosynthetic pigments, chlorophyll a to chlorophyll b ratio, showed a positive significant correlation with biomass.
Conclusion :
Generally, the variation of photosynthetic characteristics responses to salinity stress in Kochia ecotypes was high which increases the possibility of using these characteristics in breeding programs.