Effect of Salinity on Photosynthetic Properties and Concentration of Leaf Elements of Different Accession of Melons (Cucumis melo L.)

To study the effect of irrigation water salinity on physiological characteristics and the concentration of leaf elements of different accession of melons a split-plot experiment was designed based on RCBD with 3 replicates on two accessions, tolerant (Sooski and Diamond) and two accessions sensitive (Daregazi and Zard Ivanaki) and two salinity levels (tap water  2.3 ds/m (control) and 8 ds/m) according to the salinity of wells) in the field of Isfahan research station in 2016-2017. The results showed that with increasing salinity, the chlorophyll index decreased in all sensitive and tolerant accessions 21 and 16% respectivly. Photosynthesis and stomatal conductance showed the highest and lowest reduction in the Zard Ivanaki and Diamond accessions,62 and 19% respectively in comparison to the control. Stomata conductance was lowest in Zard Ivanaki (0.05) and highest in Diamond (0.39). CO2 substomatal was reduced by 44%, 26%, and 11%, respectively, in the Zard Ivanaki, Sooski and Diamond accessions. Photosynthetic water use efficiency did not have a significant effect with increasing salinity in all accessions. The amount of Na and Cl increased in the Daregazi and Zard Ivanaki accessions compared to the control, and K showed the lowest decrease by 26% in the Diamond accession. The highest reduction K/Na ratio was observed in Daregazi by 71%. The amount of P decreased in all of the accessions, except for the Daregazi, Overall, the results showed that by applying salt stress, photosynthetic parameters, K and P elements decreased, and Na and Cl increased, and this decrease was lowest in Diamonds and highest in Zard Ivanaki. Diamond resistant mass has a higher tolerance to salinity compared to sensitive cultivar through defense mechanism by restricting the uptake or transfer of sodium to aerial parts and also maintaining a good level of potassium and can be used as a tolerant cultivar under salinity conditions.