دانشگاه کاشان مهندسی اکوسیستم بیابان 2538-6336 7 شماره 1 انگلیسی 2018 08 23 Comparative Functioning of Photosynthetic Apparatus and Leaf Water Potential in Zygophyllum eurypterum (Boiss & Bushe) During Phenological Phases and Summer Drought Comparative Functioning of Photosynthetic Apparatus and Leaf Water Potential in Zygophyllum eurypterum (Boiss & Bushe) During Phenological Phases and Summer Drought 60 53 114053 FA ابوالفضل رنجبر فردویی Department of desert control and management Journal Article 2018 06 22 Background: In arid regions, seasons are often marked by differences in rainfall, with life-history 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 (F<sub>v</sub>/F<sub>m</sub>), photochemical efficiency of photosystem II (ΦPSII), effective quantum yield (F<sub>v</sub>'/F<sub>m</sub>'), photochemical dissipation of absorbed energy (qP) and non-photochemical 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 photo-inactivation of the PSII reaction centers, or expresses thermal dispersion from the antenna pigment-protein 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 <em>cab </em>gene family or destruction of light harvesting chlorophyll ‘<em>a</em>’ or ‘<em>b</em>’ pigment protein systems. Conclusions: we can say that <em>Z. eurypterum</em>can 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. Background: In arid regions, seasons are often marked by differences in rainfall, with life-history 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 (F<sub>v</sub>/F<sub>m</sub>), photochemical efficiency of photosystem II (ΦPSII), effective quantum yield (F<sub>v</sub>'/F<sub>m</sub>'), photochemical dissipation of absorbed energy (qP) and non-photochemical 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 photo-inactivation of the PSII reaction centers, or expresses thermal dispersion from the antenna pigment-protein 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 <em>cab </em>gene family or destruction of light harvesting chlorophyll ‘<em>a</em>’ or ‘<em>b</em>’ pigment protein systems. Conclusions: we can say that <em>Z. eurypterum</em>can 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. phenophase Photoinhibition photosystem pigment quenching Water deficit https://deej.kashanu.ac.ir/article_114053_8ad375355f8d5a08c1a908ee5d354d21.pdf