Study of the variation in chlorophyll a fluorescence parameters in two durum wheat cultivars in response to salinity

Physiological characteristics commonly employed for selection of tolerant and sensitive plant genotypes to environmental stresses are mainly time consuming and expensive. Since، development of alternative accurate and time–saving assay methods is inevitable. Owing to above mentioned facts، two durum wheat cultivars; Egypt 449 (tolerant) and Turky506 (sensitive) were cultured under aeroponic conditions for the evaluation of their chlorophyll a fluorescence parameters under salinity conditions. During 4-5 leafy stage، wheat seedlings were exposed to 200 mM salinity stress for 10 days. Chlorophyll a fluorescence was assayed in both salinity treated and control plants. In Turky506، OJIP-test curve area coverage، evaluation factor for quinones pool volume and photosystem II initial efficiency were significantly reduced under salinity conditions compared to control. Moreover، study of the parameters related to energy flow towards the reaction center showed that in Turky506، due to reduced ratio of active reaction center to cross section under salinity condition، parameters of energy absorption in reaction center، energy trapping ratio related to reaction center and electron flow toward reaction center were increased under salinity situations. However، blocked flow of electron transport toward reaction center in Turky506 led to increased energy waste in reaction center due to salinity. On the other hand، indexes such as energy trapping to energy absorption، electron transmission rate to trapped energy and electron transmission rate to absorptive energy rate in Turky506 were significantly reached under salinity conductions. Although، performance index under salinity was declined in both cultivars، but، the studied traits revealed than Turky506 was sensitive to salinity and also، had low efficiency. Overall، it is worthy of note that، study of the chlorophyll a fluorescence may be a validate physiological index for selection of wheat cultivars in response to salinity.