Original Papers

Photosynthetica

, Volume 44, Issue 3, pp 439-446

Photoinhibition and xanthophyll cycle activity in bayberry (Myrica rubra) leaves induced by high irradiance

  • Y. -P. GuoAffiliated withDepartment of Horticulture, College of Agriculture and Biotechnology, Zhejiang UniversityKey Laboratory of Horticultural Plant Development and Biotechnology, Ministry of Agriculture Email author 
  • , D. -P. GuoAffiliated withDepartment of Horticulture, College of Agriculture and Biotechnology, Zhejiang UniversityKey Laboratory of Horticultural Plant Development and Biotechnology, Ministry of Agriculture
  • , H. -F. ZhouAffiliated withDepartment of Horticulture, College of Agriculture and Biotechnology, Zhejiang University
  • , M. -J. HuAffiliated withDepartment of Horticulture, College of Agriculture and Biotechnology, Zhejiang University
  • , Y. -G. ShenAffiliated withInstitute of Plant Physiology and Ecology, The Chinese Academy of Sciences

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Abstract

The effect of high irradiance (HI, photosynthetically active photon flux density of 1 300 µmol m−2 s−1) on net photosynthetic rate (P N), chlorophyll fluorescence parameters, and xanthophyll cycle components were studied in fruit tree bayberry leaves. HI induced the photoinhibition and inactivation of photosystem 2 (PS2) reaction centres (RCs), which was characterized by decreased P N, maximum yield of fluorescence after dark adaptation (Fm), photochemical efficiency of PS2 (Fv/Fm) and quantum yield of PS2 (ΦPS2), and increased reduction state of QA (1-qP) and non-photochemical quenching (NPQ). Initial fluorescence (F0) showed a decrease after the first 2 h, and subsequently increased from the third hour exposure to HI. Furthermore, a greater increase in the ratio (Fi-F0)/(Fp-F0) which is an expression of the proportion of the QB non-reducing PS2 centres, whereas a remarked decrease in the slope of Fi to Fp which represents the rate of QA reduction was observed in leaves after HI exposure. Additionally, HI caused an increase in the pool size of the xanthophyll cycle pigments and sustained elevated contents of zeaxanthin (Z), antheraxanthin (A), and de-epoxidation state (DES) at the end of the irradiation period. During HI, decreased Fm, Fv/Fm, ΦPS2, NPQ, slope of Fi to Fp, V+A+Z, and DES, and increased F0, 1-qP, ratio (Fi-F0)/(Fp-F0), and V were observed in dithiothreitol (DTT)-fed leaves compared to control ones under the same conditions. Hence photoinhibition caused by HI in bayberry was probably attributed to inactivation of PS2 RCs, and photoprotection from photodamage were mainly related to the xanthophyll cycle-dependent heat dissipation in excess photons.

Additional key words

chlorophyll fluorescence dithiothreitol intercellular CO2 concentration net photosynthetic rate photosystem 2 reaction centres