Photosynthetic and Physiological Characteristics of the Evergreen Ligustrum japonicum and the Deciduous Cornus officinal
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ORIGINAL RESEARCH
Photosynthetic and Physiological Characteristics of the Evergreen Ligustrum japonicum and the Deciduous Cornus officinalis Young Seok Sim1 · Sung Hwan Yim1,2 · Yeon Sik Choo1,2 Received: 11 November 2019 / Revised: 22 September 2020 / Accepted: 23 September 2020 © Korean Society of Plant Biologist 2020
Abstract The evergreen, broad-leaved, Ligustrum japonicum and the deciduous Cornus officinalis are distributed in the central and southern parts of Korea and are widely used as landscape plants. In this study, we observed changes in the physiological characteristics of the two species across seasons by observing the changes in leaf photosynthesis; chlorophyll fluorescence; chlorophyll, carotenoid, and carbohydrate contents, osmolality and total ions. With a low soil moisture content due to low rainfall in June, the deciduous C. officinalis showed a 0.3 mmol m−2 s−1 stomatal conductance and open stomata allowing for photosynthesis. However, the evergreen L. japonicum showed a 0 mmol m−2 s−1 stomatal conductance and almost completely closed stomata, indicating a high water use efficiency. Cornus officinalis exhibited a higher leaf net photosynthetic rate (PN), stomatal conductance (gs), transpiration (E), and carbon fixation efficiency (CE) than L. japonicum in all months except for November at which time its leaves fell from senescence. In winter, L. japonicum showed a dramatic decrease in its photosynthetic rate and Fv/Fm ratio under conditions of lower than average air temperature and soil moisture; furthermore, it showed a high ratio of the photochemical quantum yield Y(NO) and almost no photosynthetic activity despite it having leaves. Ligustrum japonicum appears to be tolerant to water stress and low temperature by a maintenance of osmosis through the increase and accumulation of soluble carbohydrates in winter. In conclusion, the two species showed different physiological characteristics under a water stress environment. Keywords Ligustrum japonicum · Cornus officinalis · Photosynthesis · Chlorophyll fluorescence · Fv/Fm ratio · Water use efficiency
Introduction Photosynthesis is a basic plant metabolic process and involves the acquisition of energy using light (e.g., solar radiation) (Gunderson 2000). It is influenced by various environmental conditions such as atmospheric temperature and rainfall (Kratsch and Wise 2000). Trees are classified into evergreen species and deciduous species depending on the life cycle of their leaves. Evergreen trees have a physiology that enables photosynthesis throughout the year, which is attributed in part to their persistence of leaves for more * Yeon Sik Choo [email protected] 1
School of Life Sciences, Graduate School, Kyungpook National University, Daegu, Korea
Department of Biology, Kyungpook National University and Research Institute for Dok-do Ulleung-do Island, Daegu 41944, Korea
2
than a year (Öquist and Huner 2003). On the other hand, deciduous trees have survival strategies that involving leaf senescence as a means to reduce unwanted pl
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