AUTHOR=Wang Guangyang , Bi Aoyue , Amombo Erick , Li Huiying , Zhang Liang , Cheng Cheng , Hu Tao , Fu Jinmin 

TITLE=Exogenous Calcium Enhances the Photosystem II Photochemistry Response in Salt Stressed Tall Fescue

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.02032

DOI=10.3389/fpls.2017.02032

ISSN=1664-462X

ABSTRACT=<p>Calcium enhances turfgrass response to salt stress. However, little is known about PSII photochemical changes when exogenous calcium was applied in salinity-stressed turfgrass. Here, we probe into the rearrangements of PSII electron transport and endogenous ion accumulation in tall fescue (<italic>Festuca arundinacea</italic> Schreber) treated with exogenous calcium under salt stress. Three-month-old seedlings of genotype “TF133” were subjected to the control (CK), salinity (S), salinity + calcium nitrate (SC), and salinity + ethylene glycol tetraacetic acid (SE). Calcium nitrate and ethylene glycol tetraacetic acid was used as exogenous calcium donor and calcium chelating agent respectively. At the end of a 5-day duration treatment, samples in SC regime had better photochemistry performance on several parameters than salinity only. Such as the Area (equal to the plastoquinone pool size), N (number of <inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>Q</mml:mtext></mml:mrow><mml:mrow><mml:mtext>A</mml:mtext></mml:mrow><mml:mrow><mml:mo>-</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula> redox turnovers until F<sub>m</sub> is reached), ψE<sub>0</sub>, or δRo (Efficiencdy/probability with which a PSII trapped electron is transferred from Q<sub>A</sub> to Q<sub>B</sub> or PSI acceptors), ABS/RC (Absorbed photon flux per RC). All the above suggested that calcium enhanced the electron transfer of PSII (especially beyond <inline-formula><mml:math id="M2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>Q</mml:mtext></mml:mrow><mml:mrow><mml:mtext>A</mml:mtext></mml:mrow><mml:mrow><mml:mo>-</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula>) and prevented reaction centers from inactivation in salt-stressed tall fescue. Furthermore, both grass shoot and root tissues generally accumulated more C, N, Ca<sup>2+</sup>, and K<sup>+</sup> in the SC regime than S regime. Interrelated analysis indicated that ψE<sub>0</sub>, δRo, ABS/RC, C, and N content in shoots was highly correlated to each other and significantly positively related to Ca<sup>2+</sup> and K<sup>+</sup> content in roots. Besides, high salt increased <italic>ATP6E</italic> and <italic>CAMK2</italic> transcription level in shoot at 1 and 5 day, respectively while exogenous calcium relieved it. In root, <italic>CAMK2</italic> level was reduced by Salinity at 5 day and exogenous calcium recovered it. These observations involved in electron transport capacity and ion accumulation assist in understanding better the protective role of exogenous calcium in tall fescue under salt stress.</p>