Journal of Ecology and Environment

pISSN 2287-8327 eISSN 2288-1220

Article

Home Article View

Research

Published online August 25, 2023
https://doi.org/10.5141/jee.23.039

Journal of Ecology and Environment (2023) 47:10

Photosynthetic characteristics and chlorophyll of Vitex rotundifolia in coastal sand dune

Byoung-Jun Kim1† , Sung-Hwan Yim1,2† , Young-Seok Sim1 and Yeon-Sik Choo1,2*

1Department of Biology, Kyungpook National University, Daegu 41566, Republic of Korea
2Research Institute for Dok-do Ulleung-do Island, Kyungpook National University, Daegu 41566, Republic of Korea

Correspondence to:Yeon-Sik Choo
E-mail yschoo@knu.ac.kr

These authors contributed equally to this work.

Received: July 3, 2023; Revised: August 5, 2023; Accepted: August 6, 2023

This article is licensed under a Creative Commons Attribution (CC BY) 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ The publisher of this article is The Ecological Society of Korea in collaboration with The Korean Society of Limnology

Background: This study analyzed the physiological adaptations of a woody plant, Vitex rotundifolia, in Goraebul coastal sand dunes from May to September 2022. Environmental factors and physiological of plants growing under field and controlled (pot) conditions were compared.
Results: Photosynthesis in plants growing in the coastal sand dunes and pots was the highest in June 2022 and July 2022, respectively. Chlorophyll fluorescence indicated the presence of stress in the coastal sand dune environment. The net photosynthesis rate (PN) and Y(II) were highest in June in the coastal sand dune environment and July in the pot environment. In August and September, Y(NPQ) increased in the plants in the coastal sand dune environment, showing their photoprotective mechanism. Chlorophyll a and b contents in the pot plant leaves were higher than those in the coastal sand dune plant leaves; however, chlorophyll-a/b ratio was higher in the coastal sand dune plant leaves than in the pot plant leaves, suggesting a relatively high photosynthetic efficiency. Carotenoid content in the coastal sand dune plant leaves was higher in August and September 2022 than that in the pot plant leaves. Leaf water and soluble carbohydrate contents of the coastal sand dune plant leaves decreased in September 2022, leading to rapid leaf abscission. Diurnal variations in photosynthesis and chlorophyll fluorescence in both environments showed peak activity at 12:00 hour; however, the coastal sand dune plants had lower growth rates and Y(II) than the pot plants. Plants in the coastal sand dunes had higher leaf water and ion contents, indicating that they adapted to water stress through osmotic adjustments. However, plants growing in the coastal sand dunes exhibited reduced photosynthetic activity and accelerated decline due to seasonal temperature decreases. These findings demonstrate the adaptation mechanisms of V. rotundifolia to water stress, poor soils, and high temperature conditions in coastal sand dunes.
Conclusions: The observed variations indicate the responses of the V. rotundifolia to environmental stress, and may reveal its survival strategies and adaptation mechanisms to stress. The results provide insights into the ecophysiological characteristics of V. rotundifolia and a basis for the conservation and restoration of damaged coastal sand dunes.

Keywords: chlorophyll, chlorophyll fluorescence, coastal dune plant environmental stress, photosynthesis

Coastal dunes are ecological transformation areas where the characteristics of coastal areas and inland areas are common (Kim and Hong 2009). The ecological and functional characteristics of coastal sand dunes include a buffering role to protect coastal ecosystems from wave action (Arun et al. 1999; Mascarenhas and Jayakumar 2008), underground freshwater storage, storage of sand carried by the wind, and prevention of sand from drifting further inland by sand dune vegetation (Dahm et al. 2005). The metabolism and survival of plant species growing in coastal sand dunes are affected by various environmental stresses, such as drought, salt, flooding, high temperatures, low water acceptability of sand, low nutrient and water availability in coastal dune environments (Hesp 1991; Lawlor and Cornic 2002; Maun 1998). In particular, water scarcity is one of the major stresses in coastal sand dunes, and frequent water scarcity is caused by high evaporation rates that limit plant growth, development, and survival (Bae et al. 2013). Plants respond physiologically and biochemically to varying moisture stress levels by exhibiting reduced moisture content and osmotic potential, reduced relative water content (WC), osmotic regulation, leaf withering, high leaf temperatures, stomatal closure, cell enlargement, and reduced growth (Kumar and Singh 1998; Pasban Eslam et al. 2000; Shao et al. 2007). In addition mosture stress alters various physiological processes such as photosynthesis, respiration, transpiration, ion absorption, carbohydrate metabolism, stomatal conductivity, and electron transport (Acevedo et al. 1971; Angelopoulos et al. 1996; Flexas et al. 1998; Lu and Zhang 1998; Clifton-Brown et al. 2002; Munns 2002; Silva et al. 2007). Coastal sand dune plants are an important factor in the formation of coastal dunes, understanding coastal dunes’ responses to environmental stresses such as dryness, salinity, temperature, and light changes is important for explaining and predicting the distribution of plant colonies in coastal sand dunes, and can also play an important role in protecting natural vegetation through effective management (Hwang and Choo 2017). Plants continuously exposed to environmental stimuli have developed various adaptation strategies to settle and perpetuate within their habitats (Flowers and Colmer 2008), and in general, both stress avoidance and stress tolerance strategies in plants include various plant mechanisms that provide plant viability under environmental stress conditions (Levitt 1980). In this study, research was conducted through various analysis items to identify the physiological characteristics of coastal dune plants. Photosynthesis is the most basic physiological process in which plants obtain energy using light, and is affected by various environments such as atmospheric temperature and rainfall (Kratsch and Wise 2000). Photosynthetic ability is used as an indicator to investigate physiological properties of plants, and chlorophyll fluorescence, which can quantify changes in photosynthetic ability, such as pore opening and water utilization efficiency and photochemical reactions, can provide useful information for investigating plant reactions (Baker 2008; Gunderson 2000; Krause and Weis 1991; Murchie and Lawson 2013).

Coastal sand dune plants are known to be resistant to high-temperature dry environments that can occur for a variety of reasons, including salt, drying, high evaporation, and osmotic bonding of water (Ishikawa et al. 1990; Larcher 2003; Mooney et al. 1983). However, defining factors is a challenge because plant species avoid or adapt to environmental stress through various mechanisms.

Therefore, this study aimed to investigate seasonal variations in physiological characteristics, including photosynthetic raates, chlorophyll fluorescene, and chlorophyll contents, of the perennial sand dune plant species Vitex rotundifolia growing under field (coastal sand dunes) and controlled (pots) conditions to determine its adaptive mechanisms to environmental stress. This species was selected because it is a dominant species in the Goraebul coastal sand dune area of the East Sea in Korea.

Furthermore, sand plants are essential for the formation of coastal sand dunes, and V. rotundifolia is one of the key species (Park et al. 2009). The results of this study are expected to provide valuable information to guide coastal sand dune conservation and management in the future.

Study area and plant materials

Vitex rotundifolia, which is distributed acoss the Goraebul coatal sand Dunes, a representative coastal sand dune area of the Korean East Coast (36°35´03.5˝N 129°24´41.4˝E), was planted in a three large pots (R = 1.0 m, H = 0.9 m) in a greenhouse at the Biology Center of Kyungpook National University (35°53´12.0˝N 128°36´20.8˝E) and allowed to settle for approximately 1 year. In addition, water was supplied periodically to maintain the moisture content of the soil at approximately 5%, and 2 L of modified Hoagland’s solution was modified and treated at 2 L per pot every week (0.5 mM NH4NO3, 0.5 mM MgSO4∙7H2O, 0.5 mM KH2PO4, 0.5 mM CaCl2∙2H2O, 0.5 mM K2SO4, 19 mM Fe- EDTA and trace elements) was added to each pot every week. The physiological traits of plants growing in coastal sand dunes and pots were analyzed. The experiments were repeated at least three times for individual plants under good growth conditions to account for seasonal changes.

Physiological characteristics according to seasonal changes

(1) Photosynthesis indicators

To investigate the monthly photosynthesis pattern of V. rotundifolia, from May 2022 to September 2022, a portable photosynthesis measurement device, LCi Portable, was used by using three good leaves from each individual in the coastal sand dune environment were selected every month and subjected to this analysis. After stabilization for approximately 5 minutes with the Photosynthesis system (ADC Bioscientific Ltd., Hoddesdon, UK), net photosynthetic rate (PN), stomatal conductance (gs), transpiration rate (E), and inter-cellular CO2 concentration (Ci) were measured, and water use efficiency (WUE) was analyzed as the ratio of PN and E (PN/E), and carboxylation efficiency (CE) was analyzed as the ratio of PN and Ci (PN/Ci).

(2) Chlorophyll fluorescence

To investigate the monthly chlorophyll fluorescence pattern, a portable chlorophyll fluorescence measuring device, Portable Chlorophyll Flourometer (PAM-2500; Heinz Walz GmbH, Effeltrich, Germany), was used to measure the follwing chlorophyll fluorescence-related parameters: minimum fluorescene (Fo), maximum fluorescence (Fm), maximum photochemical quantum yield of PSII (Fv/Fm), quantum yield of photochemical energy conversion in PSII (Y[II]), quantum yield of regulated nonphotochemical energy loss in PSII (Y[NPQ]), and quantum yield of nonregulated nonphotochemical energy loss in PSII (Y[NO]).

(3) Leaf moisture content and sample solution extraction

The measured leaves were collected, the fresh weight (FW) was measured, dried in a dryer at 70°C for more than 3 days, and the dry weight (DW) was measured. The WC of the leaves was calculating with the formula.

WC (%) = [(FW – DW)/ FW] × 100

The plant sample liquid was ground into a homogeneous powder by grinding dried plant leaves with a pulverizer UDY cyclone sample mill (UDY Corperation, Fort Collins, CO, USA), and then 1 g of the sample was put into a 25 mL measuring flask and then incubated in a water bath at 95°C for 1 hour. After sufficient cooling at room temperature, the final volume was adjusted to 10 mL and extracted by filtering with a GF/C filter (pore size 1.2 µm).

(4) Chlorophyll content

A certain area (cm2) of the leaf was collected and chlorophyll was extracted for 48 hours using 5 mL of dimethyl sulfoxide. The extracted chlorophyll was measured using a UV/VIS Spectrophotometer OPTIZEN 2120 (Mecasys, Daejeon, Korea), and the content of chlorophyll a and b was calculated using the formula of Wellburn (1994) based on the absorbance at 663 nm and 645 nm, and the absorbance at 480 nm for the content of carotenoids.

Ca = 12.47 A665.1 – 3.62 A649.1

Cb = 25.06 A649.1 – 6.5 A665.1

Cx+c = (1,000 A480 – 1.29 Ca – 53.78 Cb) / 220

(5) Osmolarity, total ion content, soluble carbohydrate content

The osmotic concentration was measured with an Osmometer (Micro-Osmometer 3MO; Advanced Instruments, Norwood, MA, USA) using the principle of freezing point enhancement by taking 50 μL of the extracted sample solution. The total ion content was measured using the conductivity method (MX300 X-mate pro: Mettler Toledo, Columbus, OH, USA) by diluting 4 mL of distilled water in 1 mL of the extracted sample solution, and the value was obtained using the NaCl equivalent of Na+ and Cl ions. Soluble carbohydrate content was measured by adding 400 µL of 5% phenol solution and 2 mL of H2SO4 stock solution to a solution of 20 µL of plant extract sample solution and 780 µL of distilled water, mixing well after 10 minutes, cooling at room temperature for 30 minutes. Absorbance at 490 nm was measured using a UV/VIS Spectrophotometer OPTIZEN 2120. Glucose (20–800 µL in 1,000 µL) was used as a standard solution, and based on this, the sugar content was quantified (Chaplin and Kennedy 1994).

(6) Environmental factors

Meteorological data for the study period was obtained from local meteorological stations, and soil moisture content in areas inhabited by V. rotundifolia was measured using the ML3 ThetaProbe Soil Moisture Sensor (Delta-T Devices, Cambridge, UK).

Physiological characteristics of V. rotundifolia in response to diurnal variations

(1) Photosynthesis

To analyze the diurnal change pattern, three good leaves of plant growing in the coastal sand dunes environment on August 26, 2022 and in the large pot were collected on August 26, 2022 and August 28, 2022, respectively, at 3-hour intervals from 06:00 to 18:00 (i.e., five times a day). After stabilization for approximately 5 minutes, PN, gs, E, and Ci in mesophyll cells were measured using the LCi Portable Photosynthesis system (ADC Bioscientific Ltd.), a portable photosynthesis measuring device. WUE was analyzed as PN/E and CE was analyzed as PN/Ci.

(2) Chlorophyll fluorescence

The diurnal change pattern in the coastal sand dunes on August 26, 2022 and in the large pot on August 28, 2022 was measured at 3 hours intervals (5 times in total) from 06:00 hour to 18:00 hour using a portable chlorophyll fluorescence measuring device, Portable Chlorophyll Flourometer PAM-2500. The foloowing chlorophyll fluorescence-related parameters were measured: (1) Fo, (2) , (3) Fv/Fm, (4) the quantum yield of photochemical energy conversion in PSII (Y[II]), (5) the quantum yield of regulated non-photochemical energy loss in PSII (Y[NPQ]), and (6) the quantum yield of non-regulated, non-photochemical energy loss in PSII (Y[NO]). Fv/Fm was calculated as (Fo) / .

(3) Leaf moisture content, chlorophyll content and solutes

Leaves were collected from plants growing in coastal sand dunes on August 26, 2022 and from plants growing in pots on August 28, 2022. Leaf moisture content, chlorophyll content, osmolarity, total ion content, and soluble carbohydrate content were determined.

Seasonal changes in photochemical indicators

Environmental factors during the seasonal change measurement period

The meteorological conditions of the coastal dune area during the study period are shown in Figure 1A, B. The average temperature was the highest in July and August 2022 (24.7°C) and the lowest at 14.4°C in October 2022 (14.4°C). The average maximum temperature was the highest in July 2022 (29.6°C), whereas the average minimum temperature was the lowest in May 2022 (11.8°C). Monthly precipitation was the lowest in May 2022 (5.4 mm) and the highest in September 2022 (141.5 mm). In addition, it was investigated that the soil moisture content in the coastal sand dunes was considerably low (0.1%–0.5%) (Fig. 1A, B).

Figure 1. Seasonal variations in (A) average air temperature (°C), lowest air temperature (°C), highest air temperature (°C), (B) daily precipitation (mm), relative humidity (%) during the survey period (May–September 2022), (C) average air temperature (°C), lowest air temperature (°C), highest air temperature (°C), (D) daily precipitation (mm), relative humidity (%) during the study period (May–September 2022). Meteorological data were obtained from the Yeongdeok and Daegu meteorological observatory.

The weather conditions of Daegu, where the pot experiments were performed, are shown in Figure 1C, D. The average temperature was the highest in July 2022 (27.4°C) and the lowest in May 2022 (20.7°C). The average maximum temperature was the highest in July 2022 (32.4°C), whereas the average minimum temperature was the lowest in May 2022 (14.1°C). Monthly precipitation was the lowest in May 2022 (4.2 mm) and the highest in August 2022 (143.3 mm), (Fig. 1C, D). In the pot experiments, the soil moisture content was maintained at 4.5%–5.5% through regular water supply, and it was higher than that in the coastal sand dune environment (Fig. 2A). Photosynthetically active radiation (PAR) values for the pot plants were higher than those for the coastal sand dune plants, except for July 2022, and PAR values had a similar range at the time of measurement in both environments (Fig. 2B).

Figure 2. Seasonal variations in environmental factors in the coastal sand dune (solid line) and the pot (dashed line). (A) Soil moisture content (%), (B) photosynthetically active radiation (PAR) (μmol m–2s–1). Data are presents as mean values with standard deviation.
Photosynthesis indicators

Photosynthesis patterns in coastal dunes and large pot environments measured from May to September 2022 are shown in Figure 3. Light is essential for photosynthesis, and plants can convert solar energy into chemical energy through a metabolic process. The net photosynthetic rate is highly dependent on the amount of light absorbed by plants (Ueda et al. 2000). The PN of plants growing in coastal sand dunes exhibited an increasing trend from May to June 2022 and then decreased. The PN of plants growing in pots exhibited an increasing trend from May to July 2022; however, a decreasing trend was observed after August 2022 (Fig. 3A). A high photosynthetic rate was observed in V. rotundifolia grown in pots with continuous water supply due to a higher soil moisture content than that in the coastal sand dunes (0.1%–0.5%) (Figs. 2A and 3A). The PN, gs, and Ci of plants growing in pots increased from May to July 2022 with an increase in temperature but decreased after August 2022 with a decrease in temperature (Fig. 3A-C). In contrast, the PN, gs, and Ci of plants growing in coastal sand dunes increased from May to June 2022 but decreased after July and August 2022 when the temperature was high (Fig. 3A-C). Water is essential for photosynthesis, but transpiration, which cause water loss in plants, occurs during CO2 absorption through the stomata (Pallardy 2010). The Moisture content of leaves is regulated by the opening and closing of stomata, and stomata are known to regulate the rate of transpiration and photosynthesis of plants through gas and water exchange (Sim et al. 2021). In addition, stomatal conductance is a key factor that influences the resistance to diffusion of water, which affects transpiration in leaves. The degree of stomatal opening and closing varies with the physiological status of plants in various environments and it can be determined (Collatz et al. 1991). The stomatal conductance of V. rotundifolia leaves under pot conditions increased from 0.255 mmol m–2s–1 to 0.278 mmol m–2s–1 in July 2022, and transpiration was also recovered accordingly, resulting in an increase in the net photosynthetic rate from 17.1 μmol m–2s–1 to 19.2 μmol m–2s–1 (Fig. 3A, B). Conversely, stomatal conductance of plant leaves in the coastal sand dunes decreased from 0.130 mmol m–2s–1 to 0.113 mmol m–2s–1, and transpiration decreased accordingly, resulting in a decrease in the net photosynthetic rate from 15.6 μmol m–2s–1 to 12.6 μmol m–2s–1 (Fig. 3A, B, and D). Plants close their stomata under water stress conditions to reduce water loss from leaves, which prevents CO2 entry into the leaves, thereby reducing intracellular CO2 concentration and photosynthetic rate (Gimenez et al. 1992). The plant hormone abcisic acid (ABA) promotes stomatal closure via a signaling pathway (Arena et al. 2008). The intracellular CO2 concentration of V. rotundifolia leaves in the coastal dunes and pots exhibited the highest values in June 2022 and July 2022, respectively (Fig. 3C). WUE of V. rotundifolia growing in coastal sand dunes was higher than that of plants growing in pots (Fig. 3E). The high WUE observed in plants growing in coastal sand dunes suggests that these plants closed their stomata to overcome water strss due to the low soil moisture content of the habitat, CE exhibited a trend similar to that of PN (Fig. 3A, E, and F). The indicators of photosynthetic activity in the pot plants exhibited higher values than those in the coastal sand dune plants during the study period. The highest values of photosynthetic activity indicators were observer in plants growing in coastal sand dunes and pots in June 2022 and July 2022, respectively, indicating that CO2 consumption was efficiently achieved by photosynthesis (Fig. 3).

Figure 3. Seasonal variations in (A) net photosynthetic rate (PN), (B) stomatal conductance for CO2 (gs), (C) intercellular CO2 concentration (Ci), (D) stomatal transpiration rate (E), (E) water use efficiency (WUE), and (F) carboxylation efficiency (CE) of Vitex rotundifolia growing in coastal sand dune and the pot. Data are presented as mean values with standard deviation.
Chlorophyll fluorescence

The light energy absorbed by chlorophyll is released in the form of heat or fluorescence or used for photosynthesis, and the physiological state of the plant can be determined by calculating the ratio. This ratio is calculated as the values of Y(II), Y(NPQ), and Y(NO), which represent the ratio of energy use in photosystem II, and the value of Y(II) + Y(NPQ) + Y(NO) is 1 (Klughammer and Schreiber 2008). This rate of energy use provides crucial information about plant photosynthesis (Klughammer and Schreiber 2008). Y(II) means the quantum yield of photochemical energy conversion in PSII and has a high correlation with the rate of photosynthesis (Baker 2008). It means the mechanism of photoprotection that protects leaves by releasing excited energy generated under stress environment in the form of heat by active dissipation of regulated non-optical energy (Müller et al. 2001). In this study, V. rotundifolia exhibited a similar photosynthetic efficiency, with Y(II) ratios of 0.34 and 0.39 in May 2022 in the coastal sand dunes and large pot environments (Fig. 4). However, the Y(II) ratio (0.41) of the coastal sand dune plants was the highest in June 2022 when the photosynthetic rate was the highest, whereas that of pot plants was the highest 0.56 in July 2022 (Fig. 4A, B). The Y(II) rations in both environments initially increased to a peak and subsequently decreased, indicating a decrease in photosynthetic efficiency. The Y(NPQ) ratio of coastal sand dunes plants tended to increase. Studies suggest that more energy is used for the photoprotection mechanism that protects leaves by releasing the energy received in the form of heat to overcome the stress caused by the high temperature. Fluorescence emitted from chlorophyll is extremly sensitive to environmental stress and is widely known as an indicator of the physiological state of plants in response to environmental changes. In particular, it is known that the ratio of Fv/Fm ration indicaters the photochemical efficiency and the state of photosystem II (Falqueto et al. 2010). The Fv/Fm values of plants that are not under environmental stress ranges from 0.75 to 0.85 (Peterson et al. 1988). No stress was observed in V. rotundifolia grown in pots when Fv/Fm values were relatively low 0.70–0.75 in the coastal sand dune plants (Fig. 5). The results could be associated with the stress caused by insufficient soil moisture content and high temperature conditions in the coastal sand dunes. Furthermore, it could be due to the fact that leaf abscission was more rapid in the coastal sand dune plants than in the pot plants.

Figure 4. Seasonal variations in chlorophyll fluorescence parameters; (A) Y(II), Y(NPQ), and Y(NO) of Vitex rotundifolia in coastal sand dune, (B) Y(II), Y(NPQ), and Y(NO) of V. rotundifolia in the pot. Data are presented as mean values with standard deviation. Y(II): the quantum yield of photochemical energy conversion in PSII; Y(NPQ): the quantum yield of regulated non-photochemical energy loss in PSII; Y(NO): the quantum yield of non-regulated, non-photochemical energy loss in PSII.
Figure 5. Seasonal variations in chlorophyll fluorescence parameters; (A) Fo, (B) , (C) Fv/ of Vitex rotundifolia growing in coastal sand dune and the pot. Data are presented as mean values with standard deviation.
Chlorophyll content

Chlorophyll is an essential pigment for photosynthesis in plants and is a key factor regulating plant physiological processes. Plant leaves consist of chlorophylls a and b, which are the main elements constituting the light harvesting complex (LHC), and the chlorophyll a/b ratio indicates their composition. Chlorophyll a constitutes the reaction center and the LHC of photosystems I and II, whereas chlorophyll b serves as an antenna pigment that absorbs light and transmits it to the reaction center (Taiz and Zeiger 2006). According to the results, chlorophylls a, b, a + b contents in leaves of plants grown in pots were higher than those of plants growing on the coastal sand dunes during the study period, except for September 2022 (Fig. 6A-C). Chlorophyll a/b ratio, which is used as an indicator of photosynthetic capacity, was higher value in the coastal sand dune plants than in pot plants during the study period, with a marked increase being observed in September 2022 (Fig. 6D). The results suggest that V. rotundifolia growing on the coastal sand dunes maintains a high photosynthetic rate by increasing the photosynthetic efficiency under water stress conditions. Carotenoids assist chlorophylls in absorbing sunlight and transferring the energy to the reaction center. Carotenoid also enhence photoprotection of plants by preventing the formation of singlet oxygen through photooxidation in a high light intensity environments (Sarijeva et al. 2007). In this study, carotenoid contents of pot plants were higher between May and July 2022 than those of coastal sand dune plants (Fig. 6E). However, carotenoid content of coastal sand dune plants was relatively high in August and September 2022 (Fig. 6E). The high considered content is considered to be a photoprotective mechanism against the high temperature and intense light on coastal sand dunes (Kyparissis et al. 2000) and may be associated with the high Y(NPQ) value observed during the same period (Figs. 4 and 6).

Figure 6. Seasonal variations in (A) chlorophyll a content, (B) chlorophyll b content, (C) chlorophyll a + b content, (D) chlorophyll a/b ratio, and (E) carotenoid content in the leaves of Vitex rotundifolia growing in coastal sand dune and the pot. Data are presented as mean values with standard deviation.
Leaf water content, osmolality, total ion content, and soluble carbohydrate content

Various in leaf water content (LWC) are not only used to indicate plant health, but also tolerance to dry environmental conditions (Chyliński et al. 2007). The LWC of pot plants was constant during the study period, whereas that of coastal sand dune plants increased in August 2022 and then decreased substantially in September 2022 (Fig. 7A). This observation could be attributed to water stress and high temperature in the coastal sand dunes, and is also believed to influence early leaf detachment.

Figure 7. Seasonal variations in (A) leaf water content (B) osmolality, (C) total ion content, and (D) carbohydrate content in the leaves of Vitex rotundifolia growing in coastal sand dune and the pot. Data are presented as mean values with standard deviation.

Variations in osmolality, total ion content, and soluble carbohydrate content in the leaves of V. rotundifolia growing in the coastal sand dune and pot environments are shown in Figure 7. Osmolality in coastal sand dune plants was higher than that in pot plants between May and September 2022. Both environments exhibited increased osmolality and total ion content in September 2022 when the temperature was low (Fig. 7B, C). Generally, plants cope in stressful environments by increasing the content of readily available inorganic solutes and decreasing water potential by accumulating various ions in their vacuoles (Edwards and Dixon 1995). Specifically, leaf water potential increases with a decrease in WC under water stress, which makes it difficult to regulate the osmotic pressure of cells. Consequently, the stomata are closed and photosynthetic activity reduces, thereby inhibiting carbohydrate and nitrogen metabolism (Hsiao and Bradford 1983). To overcome water stress, plants have developed various adaptive mechanisms (Chaves et al. 2003). We speculate that V. rotundifolia maintains WC and responds to water stress by accumulating ions or osmotic compounds, such as soluble carbohydrates. Osmolarity and total ion content of the coastal sand dune plants increased in September 2022, although the soluble carbohydrate content decreased (Fig. 7B-D). Osmolarity, total ion content, and soluble carbohydrate content of the pot plants increased during the same period (Fig. 7B-D). Vitex rotundifolia may have adapted to low moisture content and low temperatures in low stress environments through osmotic adjustment and accumulation of soluble carbohydrates.

Physiological characteristics in response to diurnal variations

Environmental factors during diurnal variation

The PAR values for plants growing in coastal sand dunes and pots based on measurement time was the highest at 12:00 hour in August 2022, except for the values observed at 09:00 hour, which were similar (Fig. 8A). The PAR value for the pot plants was lower than that for the coastal sand dune plants at 09:00 hour, and higher in pot plants at 15:00 hour (Fig. 8A). The leaf temperature of V. rotundifolia growing on the coastal sand dunes ranged from 21.9°C to 34.7°C, with the highest value being observed at 12:00 hour (Fig. 8B). The leaf temperature of V. rotundifolia grown in pots ranged from 23.2°C to 39.5°C, with the lowest value being observed at 09:00 hour and the highest value at 15:00 hour under the influence of PAR (Fig. 8B).

Figure 8. Diurnal variations in environmental factors of Vitex rotundifolia growing in coastal sand dune and the pot. (A) Photosynthetically active radiation (PAR) (μmol m–2s–1), (B) leaf temperature (°C). Data are presented as mean values with standard deviation.
Diurnal variations in photosynthetic parameters

The diurnal variations in photosynthetic parameters of V. rotundifolia in August 2022 are shown in Figure 9. The net photosynthetic rate exhibited a bell-shaped normal distribution, with the highest value being observed at 12:00 hour in both environments (Fig. 9A). Furthermore, stomatal conductance and transpiration rate exhibited a similar trend (Fig. 9B, D). The photosynthetic rate of the coastal sand dune plants was lower than that of the pot plants (Fig. 9A). A similar trend was observed for gs and E, which affected PN (Fig. 9B, D). CE also exhibited a trend similar to that of PN, with the highest value being observed at 12:00 hour in the coastal sand dune plants and at 15:00 hour in the pot plants and decreasing thereafter (Fig. 9F).

Figure 9. Diurnal variation of (A) net photosynthetic rate (PN) , (B) stomatal conductance for CO2 (gs), (C) intercellular CO2 concentration (Ci), (D) stomatal transpiration rate (E), (E) water use efficiency (WUE), and (F) oxylation efficiency (CE) of Vitex rotundifolia growing in coastal sand dune and the pot. Data are presented as mean values with standard deviation.
Diurnal variations in chlorophyll fluorescence

Chlorophyll fluorescence and related parameters of V. rotundifolia leaves were measured in August 2022, and the results revealed that the diurnal Fv/Fm value in both environments ranged from 0.75 to 0.81, indicating that the plant was not affected by stress (Fig. 10). The diurnal Y(II) ratio of pot plants ranged from 0.31 to 0.37, and the photosynthetic rate of coastal sand dune plants was lower than that of pot plants at 12:00 hour (Figs. 9A and 11). Y(II) decreased, whereas the Y(NO) ratio increased (Fig. 11). Vitex rotundifolia was affected by the high temperature at 12:00 hour (Fig. 8). The results imply that most of the absorbed light energy is not used as effective photochemical energy and the ratio of energy lost passively in the form of fluorescence in the reaction center of PSII increases (Sim et al. 2021).

Figure 10. Diurnal variation in chlorophyll fluorescence parameters: (A) Fo, (B) , (C) Fv/ of Vitex rotundifolia growing in coastal sand dune and the pot. Data are presented mean values with standard deviation.
Figure 11. Diurnal variations in chlorophyll fluorescence parameters; (A) Y(II), Y(NPQ), and Y(NO) of Vitex rotundifolia in coastal sand dune. (B) Y(II), Y(NPQ), and Y(NO) of V. rotundifolia in the pot. Data are presented as mean values with standard deviation. Y(II): the quantum yield of photochemical energy conversion in PSII; Y(NPQ): the quantum yield of regulated non-photochemical energy loss in PSII; Y(NO): the quantum yield of non-regulated, non-photochemical energy loss in PSII.
Chlorophyll content

Comparison of the chlorophyll contents of V. rotundifolia in the coastal dune environment and those in the large pot environment, revealed that the contents of chlorophyll a, chlorophyll b, and chlorophyll a + b were higher in V. rotundifolia in the plants in the pot environment than in those in the coastal sand dune environment (Table 1). However, the chlorophyll a/b ratio, which is used as an indicator of photosynthetic ability, was higher in the coastal sand dune environment than in the pot environment (Table 1). It is believed that the ratio of chlorophyll a increased to increase the photosynthetic efficiency in the coastal sand dune environment where environmental stress existed. In addition, the carotenoid content was higher in the coastal sand dune environment than in the pot environment, indicating a photoprotective mechanism against high light intensity in the coastal sand dune environment (Table 1).

Table 1 . Chlorophyll contents in the leaves of Vitex rotundifolia growing in coastal sand dune and the pot.

Chlorophyll contentsCoastal sand dunePot
Chl a (μg ml–1)3.852 ± 0.2683.988 ± 0.787
Chl b (μg ml–1)0.649 ± 0.0810.729 ± 0.170
Chl a + b (μg ml–1)4.501 ± 0.2954.717 ± 0.952
Chl a/b ratio5.997 ± 0.7275.518 ± 0.361
Carotenoid (μg ml–1)1.268 ± 0.1411.186 ± 0.166

Data are presented as mean ± standard deviation.


Leaf water content, osmolarity, total ion content, and soluble carbohydrate content

The leaf LWC of V. rotundifolia in the coastal dune environment was 82.8% and that in the pot environment was 66.5% (Table 2). Therefore, it was found that more water was contained in the coastal dune environment.

Table 2 . Leaf water content and solute contents in Vitex rotundifolia leaves in coastal sand dune and the pot.

ParameterCoastal sand dunePot
Leaf water content (%)82.8 ± 2.266.5 ± 0.8
Osmolality (uosmol/g pw)400.77 ± 0.0081.41 ± 7.05
Total ions (umol/g pw)316.84 ± 0.9565.60 ± 8.87
Carbohydrate (umol/g pw)182.65 ± 45.9772.73 ± 19.10

Data are presented as mean ± standard deviation.



In addition, revealed that osmolality, total ion content, and soluble carbohydrate content of V. rotundifolia growing on the coastal dunes were higher than those of plants grown in pots (Table 2). Therefore, In the coastal sand dune environment where water stress is present due to low soil WC, it is believed that V. rotundifolia maintains the WC and responds to water stress through the accumulation of ions or osmotic substances such as soluble carbohydrates.

After transplanting the primary colony of V. rotundifolia in the Goraebul sand dunes located on the east coast of Gyeongsangbuk-do, to a large pot in a greenhouse at the Kyungpook National University and allowing it to settle for 1 year, data for the natural habitat and controlled environment were collected. Moreover, physiological characteristics such as photosynthetic rates and variations in chlorophyll fluorescence, leaf chlorophyll content, carotenoid content, LWC, osmolality, total ion content, and soluble carbohydrate content were investigated.

Seasonal variations in photosynthetic activity indicators, including gs and PN, were observed between plants growing in coastal sand dunes and pots. gs and PN of V. rotundifolia growing in coastal sand dunes were the highest in June 2022 but decreased in July 2022 when the temperature was the highest. However, gs and PN of V. rotundifolia grown in pots initially increased, reached a peak in July 2022 when the temperature was the highest, and subsequently decreased. In both environments, there was a temporal difference, but after the peak of photosynthetic activity in V. rotundifolia, it showed a tendency to decrease according to the change of seasonal time. Photosynthetic activity of the coastal sand dune plants was rapidly reduced when compared to that of pot plants. In addition, a high WUE was observed in plants growing on the coastal sand dunes with low soil moisture content than in plants grown in pots, suggesting the physiological characteristics of V. rotundifolia that facilitate its adaptation to water stress environments.

Based on the chlorophyll fluorescence results, plants in the coastal sand dune environment were stressed, whereas those grown in pots were not substantially stressed, and the Y(II) ratio exhibited a trend similar to that of PN. In addition, it exhibited a decreasing trend over time after peaking in June 2022 in the sand dune environment; however, it of plants grown in pots exhibited a decreasing trend after reaching a peak in July 2022, which was consistent with the trend of photosynthetic rate. The results revealed a decrease in photosynthetic efficiency of the coastal sand dune plants when compared to that of pot plants. The Y(NPQ) of the coastal the sand dune plants increased in August and September 2022, and the energy absorbed was not used for photosynthesis but was instead released as heat as a photoprotective mechanism. The observation is associated with the effect of environmental stress caused by high temperature and high light intensity on the coastal sand dunes.

Chlorophyll a, b, and a + b contents in the leaves of pot plants were higher than those of the coastal sand dune plants during the study period, except for September 2022; however, chlorophyll a/b ratio, which is used as an indicator of photosynthetic efficiency, was higher in the coastal sand dune plants than in the pot plants during the study period. The observation is a response mechanism of V. rotundifolia to environmental stress, where an increase in the chlorophyll a/b ratio increases photosynthetic efficiency. According to the results of LWC, osmolarity, total ion content, and soluble carbohydrate content, V. rotundifolia growing on the coastal sand dunes did not exhibit osmotic adjustment. The results revealed that leaf abscission in the coastal sand dune plants was more rapid than that in pot plants.

Furthermore, the diurnal variations in photosynthetic parameters of V. rotundifolia revealed physiological differences based on the plant environment, with photosynthetic parameters of plants grown in pots having high values at 12:00 hour (when photosynthetic rate was the highest) when compared to those of plants growing on the coastal sand dunes. Stomatal conductance (gs) and transpiration rate (E) also exhibited a similar trend. Chlorophyll fluorescence analysis revealed that the Y(II) ratio of the coastal sand dune plants decreased at 12:00 hour. Therefore, we conclude that V. rotundifolia has adapted to the coastal sand dune environment, which experiences water stress due to insufficient soil moisture, by accumulating osmotic compounds in the cells.

This study revealed that the photosynthetic rate of V. rotundifolia grown in pots initially increased owing to relatively low environmental stress but decreased in July 2022 when the temperature was the highest. Based on the diurnal variations in photosynthetic parameters, the photosynthetic rate increased substantially at 12:00 hour. Conversely, the photosynthetic rate of plants growing in coastal sand dunes, where environmental stress exists, was the highest in June 2022 and then decreased in July and August 2022 when the temperature was high, with a slight increase observed at 12:00 hour. The lack of moisture, oligotrophic soils, and high temperature conditions in coastal sand dunes hinder the photosynthetic activity of V. rotundifolia, leading to decreased photosynthesis due to temperature changes. Furthermore, V. rotundifolia growing in coastal sand dunes had higher WUE, Y(NPQ), chlorophyll a/b ratio, and carotenoid content in August and September 2022 than those grown in pots. The results indicate the survival strategies of V. rotundifolia in coastal sand dunes associated with environmental stress. Vitex rotundifolia exerts a positive effect on the biodiversity of the coastal sand dunes by adapting to the barren environment, facilitating the maintenance, stability, and formation of coastal sand dunes. The findings of this study can guide the conservation of coastal sand dunes and restoration of damaged sand dunes in the future.

WC: Water content

WUE: Water use efficiency

CE: Carboxylation efficiency

FW: Fresh weight

DW: Dry weight

PAR: Photosynthetically active radiation

LHC: Light harvesting complex

LWC: Leaf water content

Y(II): The quantum yield of photochemical energy conversion in PSII

Y(NPQ): The quantum yield of regulated non-photochemical energy loss in PSII

Y(NO): The quantum yield of non-regulated, non-photochemical energy loss in PSII

BJK did data curation, investigation, and writing-original draft. SH did data curation, funding acquisition, writing-review and editing. YS did data analysis, writing-review and editing. YS did conceptualization, supervision, writing-original draft, and writing-review and editing. All the authors approved the manuscript.

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2016R1A6A1A05011910 & 2016R1D1A1B03934927), and by grants from the National Institute of Ecology (NIE-A-2023-20 & NIE-B-2023-02).

  1. Acevedo E, Hsiao TC, Henderson DW. Immediate and subsequent growth responses of maize leaves to changes in water status. Plant Physiol. 1971;48(5):631-6. https://doi.org/10.1104/pp.48.5.631.
    Pubmed KoreaMed CrossRef
  2. Angelopoulos K, Dichio B, Xiloyannis C. Inhibition of photosynthesis in olive trees (Olea europaea L.) during water stress and rewatering. J Exp Bot. 1996;47(8):1093-100. https://doi.org/10.1093/jxb/47.8.1093.
    CrossRef
  3. Arena C, Vitale L, Santo AV. Photosynthesis and photoprotective strategies in Laurus nobilis L. and Quercus ilex L. under summer drought and winter cold. Plant Biosyst. 2008;142(3):472-79. https://doi.org/10.1080/11263500802410819.
    CrossRef
  4. Arun AB, Beena KR, Raviraja NS, idhar KR Sr. Coastal sand dunes - a neglected ecosystem. Curr Sci. 1999;77(1):19-21.
  5. Bae CY, Hwang JS, Bae JJ, Choi SC, Lim SH, Choi DG, et al. Physiological responses of Calystegia soldanella under drought stress. J Ecol Environ. 2013;36(4):255-65. https://doi.org/10.5141/ecoenv.2013.255.
    CrossRef
  6. Baker NR. Chlorophyll fluorescence: a probe of photosynthesis in vivo. Annu Rev Plant Biol. 2008;59:89-113. https://doi.org/10.1146/annurev.arplant.59.032607.092759.
    Pubmed CrossRef
  7. Chaplin MF, Kennedy JF. Carbohydrate analysis: a practical approach. 2nd ed. Oxford: ILR Press; 1994.
  8. Chaves MM, Maroco JP, Pereira JS. Understanding plant responses to drought - from genes to the whole plant. Funct Plant Biol. 2003;30(3):239-64.
    Pubmed CrossRef
  9. Chyliński WK, Łukaszewska AJ, Kutnik K. Drought response of two bedding plants. Acta Physiol Plant. 2007;29(5):399-406. https://doi.org/10.1007/s11738-007-0073-y.
    CrossRef
  10. Clifton-Brown JC, Lewandowski I, Bangerth F, Jones MB. Comparative responses to water stress in stay-green, rapid- and slow senescing genotypes of the biomass crop, Miscanthus. New Phytol. 2002;154(2):335-45. https://doi.org/10.1046/j.1469-8137.2002.00381.x.
    Pubmed CrossRef
  11. Collatz GJ, Ball JT, Grivet C, Berry JA. Physiological and environmental regulation of stomatal conductance, photosynthesis and transpiration: a model that includes a laminar boundary layer. Agric For Meteorol. 1991;54(2-4):107-36. https://doi.org/10.1016/0168-1923(91)90002-8.
    CrossRef
  12. Edwards DR, Dixon MA. Mechanisms of drought response in Thuja occidentalis L. I. Water stress conditioning and osmotic adjustment. Tree Physiol. 1995;15(2):121-7. https://doi.org/10.1093/treephys/15.2.121.
    Pubmed CrossRef
  13. Falqueto AR, Silva FSP, Cassol D, Magalhães AM Jr, Oliveira AC, Bacarin MA. Chlorophyll fluorescence in rice: probing of senescence driven changes of PSII activity on rice varieties differing in grain yield capacity. Braz J Plant Physiol. 2010;22(1):35-41. https://doi.org/10.1590/S1677-04202010000100004.
    CrossRef
  14. Flexas J, Escalona JM, Medrano H. Down-regulation of photosynthesis by drought under field conditions in grapevine leaves. Funct Plant Biol. 1998;25(8):893-900. https://doi.org/10.1071/PP98054.
    CrossRef
  15. Flowers TJ, Colmer TD. Salinity tolerance in halophytes. New Phytol. 2008;179(4):945-63. https://doi.org/10.1111/j.1469-8137.2008.02531.x.
    Pubmed CrossRef
  16. Gimenez C, Mitchell VJ, Lawlor DW. Regulation of photosynthetic rate of two sunflower hybrids under water stress. Plant Physiol. 1992;98(2):516-24. https://doi.org/10.1104/pp.98.2.516.
    Pubmed KoreaMed CrossRef
  17. Gunderson LH. Ecological resilience-in theory and application. Annu Rev Ecol Syst. 2000;31:425-39. https://doi.org/10.1146/annurev.ecolsys.31.1.425.
    CrossRef
  18. Hesp PA. Ecological processes and plant adaptations on coastal dunes. J Arid Environ. 1991;21(2):165-91. https://doi.org/10.1016/S0140-1963(18)30681-5.
    CrossRef
  19. Hsiao TC, Bradford KJ. Physiological consequences of cellular water deficits. In: Taylor HM, Jordan WR, Sinclair TR, editors. Limitations to efficient water use in crop production. Madison: American Society of Agronomy, Inc. Crop Science Society of America, Inc. Soil Science Society of America, Inc.; 1983. p. 227-65. https://doi.org/10.2134/1983.limitationstoefficientwateruse.c15.
    CrossRef
  20. Hwang JS, Choo YS. Solute patterns and diurnal variation of photosynthesis and chlorophyll fluorescence in Korean coastal sand dune plants. Photosynthetica. 2017;55(1):107-20. https://doi.org/10.1007/s11099-016-0232-8.
    CrossRef
  21. Ishikawa S, Oikawa T, Furukawa A. Photosynthetic characteristics and water use efficiency of three coastal dune plants. Ecol Res. 1990;5(3):377-91. https://doi.org/10.1007/BF02347012.
    CrossRef
  22. Kim JE, Hong SK. Landscape ecological analysis of coastal sand dune ecosystem in Korea. J Korea Soc Environ Restor Technol. 2009;12(3):21-32.
  23. Kratsch HA, Wise RR. The ultrastructure of chilling stress. Plant Cell Environ. 2000;23(4):337-50. https://doi.org/10.1046/j.1365-3040.2000.00560.x.
    CrossRef
  24. Krause GH, Weis E. Chlorophyll fluorescence and photosynthesis: the basics. Annu Rev Plant Physiol Plant Mol Biol. 1991;42:313-49. https://doi.org/10.1146/annurev.pp.42.060191.001525.
    CrossRef
  25. Kumar A, Singh DP. Use of physiological indices as a screening technique for drought tolerance in Oilseed Brassica Species. Ann Bot. 1998;81(3):413-20. https://doi.org/10.1006/anbo.1997.0573.
    CrossRef
  26. Kyparissis A, Drilias P, Manetas Y. Seasonal fluctuations in photoprotective (xanthophyll cycle) and photoselective (chlorophylls) capacity in eight Mediterranean plant species belonging to two different growth forms. Funct Plant Biol. 2000;27(3):265-72. https://doi.org/10.1071/PP99037.
    CrossRef
  27. Lawlor DW, Cornic G. Photosynthetic carbon assimilation and associated metabolism in relation to water deficits in higher plants. Plant Cell Environ. 2002;25(2):275-94. https://doi.org/10.1046/j.0016-8025.2001.00814.x.
    Pubmed CrossRef
  28. Levitt J. Responses of plant to environmental stress. Volume II: water, radiation, salt and other stresses. New York: Academic Press; 1980.
  29. Lu C, Zhang J. Effects of water stress on photosynthesis, chlorophyll fluorescence and photoinhibition in wheat plants. Funct Plant Biol. 1998;25(8):883-92. https://doi.org/10.1071/PP98129.
    CrossRef
  30. Mascarenhas A, Jayakumar S. An environmental perspective of the post-tsunami scenario along the coast of Tamil Nadu, India: role of sand dunes and forests. J Environ Manage. 2008;89(1):24-34. https://doi.org/10.1016/j.jenvman.2007.01.053.
    Pubmed CrossRef
  31. Maun MA. Adaptations of plants to burial in coastal sand dunes. Can J Bot. 1998;76(5):713-38. https://doi.org/10.1139/b98-058.
    CrossRef
  32. Mooney HA, Field C, Williams WE, Berry JA, Björkman O. Photosynthetic characteristics of plants of a Californian cool coastal environment. Oecologia. 1983;57(1-2):38-42. https://doi.org/10.1007/bf00379559.
    Pubmed CrossRef
  33. Müller P, Li XP, Niyogi KK. Non-photochemical quenching. A response to excess light energy. Plant Physiol. 2001;125(4):1558-66. https://doi.org/10.1104/pp.125.4.1558.
    Pubmed KoreaMed CrossRef
  34. Munns R. Comparative physiology of salt and water stress. Plant Cell Environ. 2002;25(2):239-50. https://doi.org/10.1046/j.0016-8025.
    Pubmed CrossRef
  35. Murchie EH, Lawson T. Chlorophyll fluorescence analysis: a guide to good practice and understanding some new applications. J Exp Bot. 2013;64(13):3983-98. https://doi.org/10.1093/jxb/ert208.
    Pubmed CrossRef
  36. Pallardy SG. Physiology of woody plants. 3rd ed. Cambridge: Academic Press; 2010.
  37. Park JM, Park CM, Ezaki T. Ecological study on the Vitex rotundifolia communities in Korea. J Jpn Soc Coast For. 2009;8(1):17-23.
  38. Pasban Eslam B, Shakiba MR, Neyshabouri MR, Moghadam M, Ahmadi MR. Evaluation of physiological indices as a screening technique for drought resistance in oilseed rape. Pak Acad Sci J. 2000;37(2):143-52.
  39. Peterson RB, Sivak MN, Walker DA. Relationship between steady-state fluorescence yield and photosynthetic efficiency in spinach leaf tissue. Plant Physiol. 1988;88(1):158-63. https://doi.org/10.1104/pp.88.1.158.
    Pubmed KoreaMed CrossRef
  40. Sarijeva G, Knapp M, Lichtenthaler HK. Differences in photosynthetic activity, chlorophyll and carotenoid levels, and in chlorophyll fluorescence parameters in green sun and shade leaves of Ginkgo and Fagus. J Plant Physiol. 2007;164(7):950-5. https://doi.org/10.1016/j.jplph.2006.09.002.
    Pubmed CrossRef
  41. Shao HB, Chu LY, Lu ZH, Kang CM. Primary antioxidant free radical scavenging and redox signaling pathways in higher plant cells. Int J Biol Sci. 2007;4(1):8-14. https://doi.org/10.7150/ijbs.4.8.
    Pubmed KoreaMed CrossRef
  42. Silva MA, Jifon JL, Silva JAG, Sharma V. Use of physiological parameters as fast tools to screen for drought tolerance in sugarcane. Braz J Plant Physiol. 2007;19(3):193-201. https://doi.org/10.1590/S1677-04202007000300003.
    CrossRef
  43. Sim YS, Yim SH, Choo YS. Photosynthetic and physiological characteristics of the evergreen Ligustrum japonicum and the deciduous Cornus officinalis. J Plant Biol. 2021;64(1):73-85. https://doi.org/10.1007/s12374-020-09284-0.
    CrossRef
  44. Taiz L, Zeiger E. Plant physiology. 4th ed. Sunderland: Sinauer Associates, Inc.; 2006.
  45. Ueda Y, Nishihara S, Tomita H, Oda Y. Photosynthetic response of Japanese rose species Rosa bracteata and Rosa rugosa to temperature and light. Sci Hortic. 2000;84(3-4):365-71. https://doi.org/10.1016/S0304-4238(99)00138-7.
    CrossRef
  46. Wellburn AR. The spectral determination of chlorophylls α and β, as well as total carotenoids, using various solvents with spectrophotometers of different resolution. J Plant Physiol. 1994;144(3):307-13. https://doi.org/10.1016/S0176-1617(11)81192-2.
    CrossRef

Share this article on

Related articles in JEE

Close ✕

Journal of Ecology and Environment

pISSN 2287-8327 eISSN 2288-1220