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Acta Prataculturae Sinica ›› 2020, Vol. 29 ›› Issue (8): 116-125.DOI: 10.11686/cyxb2020072

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Changes in photoinhibition and fatty acid composition in the thylakoid membrane of kidney bean leaves under low temperature and weak light stress

WANG Yu-ping1, 2, *, GAO Chun-xiao1, WANG Sheng-xiang1, HE Xiao-tong2   

  1. 1. Gansu Key Laboratory of Crop Improvement & Germplasm Enhancement, Gansu Provincial Key Laboratory of Aridland Crop Science, Gansu Agricultural University, Lanzhou 730070, China;;
    2. College of Horticulture, Gansu Agricultural University, Lanzhou 730070, China
  • Received:2020-02-21 Revised:2020-04-07 Online:2020-08-20 Published:2020-08-20

Abstract: This research investigated the changes in photoinhibition and fatty acid composition in thylakoid membrane under combined stresses of low temperature and weak light in two varieties of kidney bean, ‘British big red’ and ‘Shanxi small red’, which have different sensitivity to low temperature and weak light. The main lipids in the thylakoid membrane are monogalactosyl diglyceride (MGDG), digalactosyl diglyceride (DGDG), phosphatidylcholine, phosphatidylglycerol (PG) and sulphoquinovosyl diglyceride (SQDG). The fatty acid composition of the thylakoid membrane, together with photosynthetic and chlorophyll (Chl) fluorescence parameters were determined during stress and recovery. It was found that with increase in stress duration, the content of Chl a, Chl b and Chl (a+b) decreased while the ratio of Chl a/b increased. Compared to the control, the maximum quantum yield of PSⅡ (Fv/Fm), the efficiency of excitation capture by open PSⅡ reaction centers (Fv'/Fm'), the photochemical quenching coefficient (qP) and the actual PSⅡ efficiency (ΦPSⅡ) declined, but Chl a/b and the non-photochemical quenching (NPQ) increased. With more prolonged stress duration MGDG, DGDG and SQDG, and thylakoid membrane content of linolenic acid (C18:3) were substantially reduced and the content of palmitic acid (C16:0) was concomitantly increased. These changes with increased stress duration represented an increased content of saturated fatty acids, and a decreased content of unsaturated fatty acids (UFA), polyunsaturated fatty acids (PUFA) and degree of membrane unsaturation in the thylakoid membrane lipids. However, there were also changes in the PG fraction which contributed to maintaining the overall degree of unsaturation in membrane lipids. This pattern was reversed during the recovery period. The correlation coefficients between PUFA and Fv/Fm of ‘British big red’ and ‘Shanxi small red’ kidney beans were 0.8621 and 0.8392, respectively. Compared to ‘British big red’ kidney beans, stress caused more serious photoinhibition in PSⅡ of ‘Shanxi small red’ kidney bean leaves. Therefore, it can be postulated from these results that the reason for the increased the stability of the thylakoid membrane and reduced photoinhibition of PSⅡ in ‘British big red’ kidney beans may be the higher membrane content of UFA, especially PUFA.

Key words: red kidney bean, low temperature and weak light, thylakoid membrane, polyunsaturated fatty acids, chlorophyll fluorescence