title: Effect of leaf dehydration duration and dehydration degree on PSII photochemical activity of papaya leaves.
abstract: Although the effect of dehydration on photosynthetic apparatus has been widely studied, the respective effect of dehydration duration and dehydration degree was neglected. This study showed that, when leaves dehydrated in air, the PSII activities of leaves decreased with the decline of leaf relative water content (RWC). Unexpectedly, when leaves dehydrated to same RWC, the decreases in Fv/Fm, Ψo and RC/CSm were lower in leaves dehydrating at 43 °C than those at 25 °C. However, to reach the same RWC, leaves dehydrating at 43 °C experienced 1/6 of the dehydration duration for leaves dehydrating at 25 °C. To distinguish the respective effect of dehydration degree and dehydration duration on photosynthetic apparatus, we studied the PSII activities of leaves treated with different concentration of PEG solutions. Increasing dehydration degree aggravated the decline of Fv/Fm, Ψo and RC/CSm in leaves with the same dehydration duration, while prolonging the dehydration duration also exacerbated the decline of Fv/Fm, Ψo and RC/CSm in leaves with identical dehydration degree. With the same dehydration degree and duration, high temperature enhanced the decrease of Fv/Fm, Ψo and RC/CSm in the leaves. When leaves dehydrated in air, the effect of high temperature was underestimated due to reduction of dehydration duration. The results demonstrated that, dehydration degree and duration both play important roles in damage to photosynthetic apparatus. We suggest that, under combined stresses, the effects of dehydration degree and duration on plants should be considered comprehensively, otherwise, partial or incorrect results may be obtained.
authors.affiliation: State Key Lab of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an 271018, Shandong, China.
authors.forename: Meijun
authors.initials: M
authors.lastname: Liu
authors.affiliation: State Key Lab of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an 271018, Shandong, China.
authors.forename: Zishan
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: State Key Lab of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an 271018, Shandong, China. Electronic address: gaohy@sdau.edu.cn.
authors.forename: Huiyuan
authors.initials: H
authors.lastname: Gao
authors.affiliation: State Key Lab of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an 271018, Shandong, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Yang
authors.affiliation: State Key Lab of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an 271018, Shandong, China.
authors.forename: Xingli
authors.initials: X
authors.lastname: Fan
authors.affiliation: College of Life Science, Northeast Forestry University, Harbin 150040, Heilongjiang, China.
authors.forename: Dandan
authors.initials: D
authors.lastname: Cheng
mesh_terms: D029441:Carica / Q000378:metabolism* / Q000502:physiology*; D003681:Dehydration / Q000378:metabolism; D010788:Photosynthesis / Q000502:physiology; D045332:Photosystem II Protein Complex / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism* / Q000502:physiology*; D013696:Temperature
chemical_list: D045332:Photosystem II Protein Complex
keywords: Dehydration degree; Dehydration duration; PEG; PSII photochemical activity; Papaya