comparative functioning of photosynthetic apparatus and leaf water potential in zygophyllum eurypterum (boiss & bushe) during phenological phases and summer drought

Background: in arid regions, seasons are often marked by differences in rainfall, with lifehistory events, along with phenological stages. materials and methods: three phenological phases were distinguished as vegetative phase (vp), flowering phase (fp) and seeding phase (sp). chlorophyll fluorescence parameters (chl. fps) such as maximum quantum yield of psii photochemistry (fv/fm), photochemical efficiency of photosystem ii (φpsii), effective quantum yield (fv’/fm’), photochemical dissipation of absorbed energy (qp) and nonphotochemical dissipation of the absorbed energy (npq) along with pigment contents and predawn leaf water potential (ψl) were determined. results:all chl. fps changed along drought stress gradient and phenological phases, with significant changes at sp. discussion: a significant change in the mentioned parameters explains the happening of severe photoinhibition because of photoinactivation of the psii reaction centers, or expresses thermal dispersion from the antenna pigmentprotein compound. a remarkable alteration in pigment content was noticed at the sp. decrease in the chlorophyll content under drought stress can be due to a reduction in synthesis of pigment complexes encoded by the cab gene family or destruction of light harvesting chlorophyll ‘a’ or ‘b’ pigment protein systems. conclusions: we can say that z. eurypterumcan protects the psii reaction center from damage at the middle stage of drought stress (end of july) and can be qualified as a drought tolerant species.