Physiological and growth responses of two dogwoods to short-term drought stress and re-watering

CHNAES-00645; No of Pages 6 Acta Ecologica Sinica xxx (2019) xxx

Contents lists available at ScienceDirect

Acta Ecologica Sinica journal homepage: www.elsevier.com/locate/chnaes

Physiological and growth responses of two dogwoods to short-term drought stress and re-watering Qiang Lu a, Jie Xu a, Xiangxiang Fu a,⁎,1, Yan Fang b a b

Southern Modern Forestry Collaborative Innovation Centre, College of Forestry, Nanjing Forestry University, Nanjing 210037, China Nanjing Forest Police College, Nanjing 210037, China

a r t i c l e

i n f o

Article history: Received 12 October 2018 Received in revised form 21 March 2019 Accepted 17 May 2019 Available online xxxx Keywords: Cornus florida Drought stress Re-watering Physiological parameter Biomass allocation

a b s t r a c t Cornus florida and its cultivars have attracted many attentions by its colorful ornamental features. Suitable moisture condition is a major factor in the success of introduction. However, little is known about dogwoods drought adaptation to seasonal water deficit, and recovery potential from the following rainfall. In this paper, treatment of continuous drought lasted 19 days, followed by re-watering for 7 days was performed on 10-month-old seedlings of C. florida, comparing with native C. kousa. Meantime, well-watered seedlings of two species were regarded as controls. Soil relative water content (SRWC) in stressed seedlings of both dogwoods decreased significantly with drought stress prolonged, and recovered to the normal level after re-watering. As the response to drought stress, significant decline in internal carbon dioxide concentration (Ci), remarkable increment in intrinsic water use efficiency (WUEi) in C. florida, significant increment in chlorophyll content in C. kousa, and notable decline in leaf relative water content (LRWC), maximum quantum efficiency of PSII photochemistry (Fv/ Fm), photochemical quenching (qP), as well as significant increment in malondialdehyde (MDA) content, superoxide dismutase (SOD) activity, soluble sugar content (SSC) in both dogwoods were observed. However, most of physiological variables recovered to the level of control after re-watering. Furthermore, drought stress promoted root volume, root area, root biomass, whereas inhibited seedling height, basal diameter, aboveground biomass, resulting in increase of root/shoot ratio. Our findings indicate that, although C. florida has a weaker performance than C. kousa under drought stress, it can recover to the normal level after re-watering. These results suggest that C. florida and its cultivars possess drought adaptive potential for introducing to southern China. © 2019 Ecological Society of China. Published by Elsevier B.V. All rights reserved.

1. Introduction Drought stress is one of the most abiotic stress factors and limitations for plant growth [1]. Hence, plants tend to develop some adaptive mechanisms to drought stress via complex physiological and molecular changes, which affects the growth, biomass accumulation and allocation of plants [2–4]. The mechanisms of plant in response to drought stress have been demonstrated by many researchers [5–7]. As we know, the growth and physiological behaviour of drought-stressed plants may be altered by water deficit, especially in introduced species [8]. Usually, short-term water deficit is the pivot factor affecting success of introduction for alien species [9,10]. With the increasing demand for ornamental species, more and more attractive ornamental trees are to be introduced to subtropical region of China.

⁎ Corresponding author. E-mail address: [email protected] (X. Fu). 1 Present address: Nanjing Forestry University, Longpan 159#, Nanjing 210037, China. Email address: [email protected]

Dogwoods belong to genus of Cornus with two groups: East Asia group including C. kousa has 10 species; and North America group contains C. florida and C. nuttallii [11]. They play a vital role in forest ecosystems [12]; more importantly, their cultivars are widely used as ornamental plants in gardens and urban landscapes due to attractive horticultural traits, such as petal-like bracts of red, pink or white in the spring, bright red berries and colorful leaves in the fall [13]. To date, N100 cultivars selected from C. florida, C. nuttallii, C. kousa and their hybrids have enjoyed considerable success as a flowering shrub for use in gardens and urban landscaping in the United States, Canada, Mexico and Japan. As an original habitat of Eastern Asian dogwoods, China is a potential suitable region to introduce cultivars of dogwoods originating from North America group [14,15]. However, water deficit events occur frequently in the middle and lower reaches of the Yangtze River, southern China, where drought is usually caused by short-term extreme high temperature and/or periodic no rain in summer, and relieved by the following rainy autumn. For dogwoods of North America group, which are likely to grow in the subtropical and Marine Westcoast climate of the United States [13], adaptability of North America group to where it is

https://doi.org/10.1016/j.chnaes.2019.05.001 1872-2032/© 2019 Ecological Society of China. Published by Elsevier B.V. All rights reserved.

Please cite this article as: Q. Lu, J. Xu, X. Fu, et al., Physiological and growth responses of two dogwoods to short-term drought stress and rewatering, Acta Ecologica Sinica, https://doi.org/10.1016/j.chnaes.2019.05.001

Q. Lu et al. / Acta Ecologica Sinica xxx (2019) xxx

introduced should be considered emphatically. Although numerous documents have revealed the response mechanisms of plant to drought stress [5–7], little is known about the responses of dogwoods to water deficit, especially to the following re-watering. Thus, the objective of this study was to investigate how drought stress and re-watering affect physiological parameters, growth and biomass accumulation of the introduced C. florida, in comparison with the native C. kousa. The results will provide the basis for understanding the abilities and mechanisms of drought tolerance in dogwoods. We also evaluate the possibility of successful introduction for C. florida and its cultivars to southern China. 2. Materials and methods 2.1. Plant material and growth conditions We sowed seeds of C. florida and C. kousa in Nov. 2014 that came from Louisiana of the United States and Japan, respectively. 10-monthold seedlings of both species were cultivated in containers (D × H: 20 cm × 20 cm) filled with a mixture of peat soil: yellow brown soil: perlite: carbonized rice husk (5:3:1:1, v/v/v/v, pH 6.40) in a greenhouse. 240 homogenous seedlings in morphology were selected as experimental materials in early Aug. 2015. The seedlings were 30–50 cm and 40–55 cm in height, 0.40–0.65 cm and 0.45–0.80 cm in basal diameter for C. florida and C. kousa, respectively. A 2-week acclimatization period was conducted after the seedlings were transferred into an artificial climate chamber, where controlled conditions were at a 30 °C day/25 °C night temperatures, photoperiod of 12 h at 550 μmol m−2 s−1 light intensity, and relative humidity at 60–70%.

100 80

SRWC (%)

2

C. florida C. kousa Control of both species

60 40 20 0

0

5

8

13

14

15

16

17

18

19

27

Day Fig. 1. Changing patterns of SRWC with the process of drought and re-watering treatments in C. florida and C. kousa seedlings. Continuous drought for 19 days, then re-watering for one week.

respectively. SRWC was calculated as follows: SRWC ð%Þ ¼ ½ðWfs−WdsÞ=ðWss−WdsÞ  100 A sample of fresh soil from topsoil to subsoil of pot was weighed as fresh soil weight (Wfs), then irrigated saturation and weighed as saturated soil weight (Wss), subsequently oven-dried at 85 °C for 24 h to constant weight (Wds). 2.4.2. LRWC Leaves from the middle of the three seedlings were sampled and mixed on the 19th and 27th day, respectively. LRWC was calculated according to the following formula: LRWC ð%Þ ¼ ½ðWf −WdÞ=ðWs−WdÞ  100

2.2. Drought treatments 60 seedlings with 3 replicates × 20 seedlings, were assigned to controls and drought treatments for two species; well-watered seedlings were regarded as controls. For drought treatments, seedlings suffered continuously drought stress (no watering) for 19 days (soil relative water content reduced to approximately 15%), when temporary wilting on leaves occurred (as a sign to stop drought treatment). Then, fully watering was supplied for another week as a re-watering treatment. 2.3. Sampling for parameters measurement Ten seedlings for each replicate were randomly selected just for monitoring soil relative water content (SRWC), leaf relative water content (LRWC) and growth. During the experiment, fully developed leaves from the middle of the three seedlings for each replicate were randomly collected from remaining containers on the 0th, 8th, 13th, 19th and 27th day, respectively, and stored at −70 °C for subsequently measurements of malondialdehyde (MDA) content, activity of superoxide dismutase (SOD), and soluble sugar content (SSC). Meanwhile, gas exchange and chlorophyll fluorescence were recorded on another three randomly selected seedlings on the 0th, 8th, 13th, 16th, 18th, 19th and 27th day of treatment, respectively. Chlorophyll content was only measured on the 19th day. The dates for determination of above indicators were based on the changing pattern of SRWC: quick loss (0 ~ 13th day) → slow loss (13 ~ 19th day) → quick recovery (after re-watering) (Fig. 1). 2.4. Measurements 2.4.1. SRWC Three marked seedlings from each replicate were weighed on the 0th, 5th, 8th, 13th, 14th, 15th, 16th, 17th, 18th, 19th and 27th day,

Sampled leaves were weighed as fresh weight (Wf), subsequently soaked in distilled water for 24 h at dark as saturated weight (Ws), and oven-dried at 105 °C for 15 min, then dried to constant weight (Wd) at 80 °C. 2.4.3. Growth and biomass Height and basal diameter of each seedlings, were measured on the 0th and 27th day of treatment. The relative growth rate (RGR) was calculated as follows: RGR ð%Þ ¼ ½ðH1 −H2 Þ=H 2   100 where H2 was the height or basal diameter on the 0th day, H1 was the height or basal diameter on the 27th day of treatment. At the end of the experiment, five intact plants (leaves, stem and root) of each replicate were harvested for biomass measurements. The total leaf area, root length, root volume and root area were estimated by a Root Scanner (Perfection 4990 Photo, EPSON Inc., Shanghai, China). Then leaves, stem and root were dried to constant weight in an oven at 80 °C. 2.4.4. Gas exchange and chlorophyll fluorescence Gas exchange was measured using a portable photosynthesis system (LI-6400, LI-COR Inc., Lincoln, Nebraska, USA) equipped with a LED light source. Gas exchange variables, including stomatal conductance (Gs, mol H2O m−2 s−1), net photosynthesis (Pn, μmol CO2 m−2 s−1) and internal carbon dioxide concentration (Ci, μmol CO2 mol−1) were measured under an artificial environment of 400 μmol mol−1 CO2, 500 μmol s−1 air flow rate and 600 μmol m−2 s−1 photosynthetically active radiation white light. Intrinsic water use efficiency (WUEi, μmol CO2 mol−1 H2O) was calculated by Pn/Gs. Maximum quantum efficiency of PSII photochemistry (Fv/Fm) and photochemical quenching (qP) were determined using a pulse

Please cite this article as: Q. Lu, J. Xu, X. Fu, et al., Physiological and growth responses of two dogwoods to short-term drought stress and rewatering, Acta Ecologica Sinica, https://doi.org/10.1016/j.chnaes.2019.05.001

Q. Lu et al. / Acta Ecologica Sinica xxx (2019) xxx

modulation fluorometer (PAM-2500, Walz Inc., Effeltrich, Germany) on the adaxial leaf surface and were calculated according to Baker and Rosenqvist [16]. 2.4.5. Photosynthetic pigment content About 0.2 g of finely cut and well-mixed leaf sample was repeatedly extracted with 8 mL 95% acetone at 4 °C for 24 h in the dark. The extracted solution was merged, filtered and set a volume to 25 mL with brown volumetric flask. The absorbance of supernatant was measured with a spectrophotometer (DU800, Beckman Coulter Inc., California, USA) at 645 nm and 663 nm, respectively. Chlorophyll content was calculated according to Wang and Huang [17] and expressed in mg g−1 fresh weight (FW). 2.4.6. Content of MDA 0.2 g fresh leaves were ground in the 5 mL of 10% trichloroacetic acid (TCA) and then centrifuged at 3000 rpm for 10 min. 2 mL of 0.67% thiobarbituric acid (TBA) was added in 2 mL aliquot of the supernatant. The mixture was heated at 100 °C for 30 min and then quickly cooled in ice bath. After centrifugation (Allegra X-22R Centrifuge, Beckman Coulter Inc., California, USA) at 5000 rpm for 20 min, the absorbance of the supernatant was recorded at 450 nm, 532 nm and 600 nm with a spectrophotometer, respectively. MDA content was calculated according to [17] and expressed in μmol g−1 FW. 2.4.7. Activity of SOD 0.2 g fresh leaf tissue was ground using a mortar and pestle containing 5 mL of grinding media consisting of 0.05 mol L−1 phosphate buffer solution (pH 7.8) and a little of quartz sand at 4 °C. Following centrifugation at 4000 rpm for 10 min at 4 °C. The supernatant was measured with a spectrophotometer at 560 nm. One unit of SOD was defined as the amount needed for 50% inhibition of nitro-blue tetrazolium (NBT) reduction and calculated according to [17] and expressed in U g−1 FW. 2.4.8. SSC 0.2 g finely cut fresh leaves were heated at 100 °C for 30 min twice with 20 mL distilled water. After heating, the insoluble residue was removed by centrifuging at 5000 rpm for 10 min. The supernatant was set a volume to 25 mL with volumetric flask. 0.5 mL sample solution, 1.5 mL distilled water, 0.5 mL anthrone-ethyl acetate reagent and 5 mL sulfuric acid were added in test tube sequentially. After oscillation, the mixed solution was kept for 1 min in boiling water bath. Determination of absorbance at 630 nm after cooling to room temperature. SSC was calculated according to [17] and expressed in mg g−1 FW.

3

significantly higher than that of C. florida on the 19th day (P = 0.02) (Fig. 1), indicating transpiration rate in C. kousa was higher than that in C. florida. However, no significance of SRWC on the 27th day (P = 0.61) was detected between two species. 3.1.2. LRWC T/C of LRWC decreased to 69.72% and 51.38% on the 19th day of treatment, then recovered back to 97.82% and 98.14% in C. florida and C. kousa after re-watering for one week, respectively, showing the changing pattern of LRWC in two species was in sync with that of SRWC (Fig. 1). Moreover, the ability of leaf water-holding in C. kousa was significantly lower than that of C. florida (P = 0.02) under drought stress. However, no significance of LRWCs on the 27th day was observed in C. florida (P = 0.66) and C. kousa (P = 0.32) in comparison with controls, suggesting no substantial damage induced by drought stress. 3.2. Morphological variables 3.2.1. Growth index The decline in T/C of RGR in height, basal diameter and total leaf area was observed in both species (Table 1). Although the reduction in RGR of height in C. florida was apparently more than that in C. kousa, the reduction in total leaf area in C. florida was significantly lower than that in C. kousa. The decrease in basal diameter showed similar tendency with height, however, no significance was found between two species (Table 1). Under drought stress, slightly reduction in total root length, small increase in total root area, and increment in total root volume were observed in both species (Table 1). Independent-samples t-test showed no significant differences for three root variables between two species. 3.2.2. Biomass distribution Generally, adjustment of biomass distribution in root, stem and leaf of plant is an effective way to adapt adversity conditions, especially to drought stress. Apparently, leaves biomass accumulation decreased under drought treatment in both dogwoods, and the reduction in C. kousa was significantly more than that in C. florida (Table 2). However, slight decline of biomass in stem and increment in root of C. florida, and increment in root of C. kousa were measured. Overall, down trends were monitored in total biomass, while promotion in root/shoot ratio occurred in seedlings of both species under drought stress. Independent-samples t-test showed no significant differences between two dogwoods in all biomass values except leaves (Table 2). 3.3. Photosynthetic parameters

2.5. Statistical analysis All data were subjected to a calculation formula: T/C (%) = (value of treatment/value of control) × 100. The Duncan's new multiple range tests, independent-samples t-test, one-way and two-ways analysis of variance (ANOVA) were performed using SPSS 19.0 for Windows 7.0 Software (IBM Corporation). The data were presented as mean ± standard deviation. Differences at P b 0.05 were considered significant. 3. Results 3.1. Water dynamics in soil and leave 3.1.1. SRWC Similar patterns in SRWC for C. florida and C. kousa under drought and re-watering treatments were observed (Fig. 1). During the treatments, SRWC declined quickly on the earlier stage (0 ~ 13th day), then steady declined with slow speed during the interim treatment (13 ~ 19th day), and reached the lowest point on the 19th day. Rapid recovery in SRWC was monitored after re-watering, and went back to the level of controls on the 27th day. Soil water loss rate of C. kousa was

3.3.1. Chlorophyll content Light reduction of chlorophyll content in C. florida (T/C = 98.54%), and significant increment in C. kousa (T/C = 152.99%) were found on the 19th day of drought treatment. Furthermore, a significance was observed in chlorophyll content between two species (P = 0.001), indicating that more chlorophyll was produced in C. kousa than in C. florida in response to drought stress. Table 1 Responses of growth parameters of C. florida and C. kousa seedlings to drought stress. T/C of parameters (%)

RGR of height RGR of basal diameter Total leaf area Total root length Total root volume Total root area

Species

Sig. of interspecies

C. florida

C. kousa

46.65 ± 8.03 68.62 ± 16.23 67.23 ± 11.39 93.51 ± 15.54 110.95 ± 20.56 102.50 ± 8.90

74.08 ± 6.13 80.97 ± 12.57 48.28 ± 8.56 90.02 ± 18.73 115.06 ± 44.86 103.03 ± 5.00

⁎ NS ⁎ NS NS NS

⁎ P b 0.05; NS indicates no significant difference between two species according to independent-samples t-test.

Please cite this article as: Q. Lu, J. Xu, X. Fu, et al., Physiological and growth responses of two dogwoods to short-term drought stress and rewatering, Acta Ecologica Sinica, https://doi.org/10.1016/j.chnaes.2019.05.001

Q. Lu et al. / Acta Ecologica Sinica xxx (2019) xxx

Table 2 Response of biomass allocation to drought and re-watering treatments in C. florida and C. kousa seedlings. T/C of parameters (%)

Dry weight

Leaves Stem Root Total dry weight Root/shoot ratio

Species

Sig. of interspecies

C. florida

C. kousa

82.46 ± 10.54 94.51 ± 14.45 108.00 ± 18.52 91.72 ± 3.23 122.44 ± 23.15

60.56 ± 11.58 100.61 ± 6.98 117.81 ± 29.28 87.49 ± 5.12 149.18 ± 47.33

⁎ NS NS NS NS

C. florida

(a)

103 101

C. kousa

a

a

a

102

T/C of Fv/Fm (%)

4

a

100

bc

ab

a

99

bc

98

cd

ab

97

ab

ab d

96

b

95 94 0

⁎ P b 0.05; NS indicates no significant difference between two species according to independent-samples t-test.

8

13

15

18

19

27

Day 120

(b)

a

3.3.2. Ci and WUEi Stomatal regulation is generally one of the earliest responses of plant to adversity environments. T/C of Ci in C. florida declined significantly on the 19th day of drought treatment (T/C = 51.12%) (Fig. 2a), and did not recover to the level of control after re-watering (on the 27th day). While no significant reduction of T/C of Ci occurred in C. kousa during treatment. Two-ways ANOVA also showed a significance in T/C of Ci (P = 0.0002) between two species, suggesting the response of stomatal adjustment to drought stress in C. florida was quicker than that in C. kousa. Conversely, astonishing increment in T/C of WUEi in C. florida was detected on the 19th day (T/C = 316.75%) (Fig. 2b), but fell back quickly to the level of control after re-watering. The value of WUEi kept relatively stable in C. kousa during treatment. Two-ways ANOVA showed no significance in T/C of WUEi (P = 0.12) between two species, suggesting the similar potential to endure short-term drought for two dogwoods.

Fig. 3. Changing patterns of (a) Fv/Fm and (b) qP during drought and re-watering treatment in C. florida and C. kousa seedlings. Continuous drought for 19 days, then rewatering for one week. Letters with same color indicate statistical results among different stages in same species, the same letter denotes no significant difference among different stages of treatment according to Duncan's new multiple range test (P b 0.05).

3.3.3. Fv/Fm and qP Similar changing tendencies in T/C of Fv/Fm and qP in two dogwoods during drought and re-watering treatments were observed (Fig. 3). Both T/C of Fv/Fm and qP significantly decreased with the continuing

drought, then went back to the level of control after re-watering. No significances in T/C of Fv/Fm (P = 0.52) and qP (P = 0.59) between two species in response to continuous drought stress, suggesting the similar responses to water deficit.

110 100

T/C of qP (%)

ab

ab

ab

a

a

a

90

bc a

80

a cd b

70

d b

60 50 0

8

13

15

18

19

27

Day

3.4. Physiological indicators

T/C of Ci (%)

140

(a)

120

ab

100

a

a

ab

C. florida

ab

C. kousa

ab ab b

80

b

b

b

b

b c

60 40 0

8

13

15

18

19

27

Day 450

(b)

a

T/C of WUEi (%)

400 350 300 250 200

a

150 100

b a

bc

50

a

a

b

bc

a b

a a

c

3.4.1. MDA content, activity of SOD and SSC Similar changing trends in T/C of MDA and SOD occurred in C. florida and C. kousa under drought and re-watering treatments (Fig. 4a–b). During treatment, both MDA and SOD significantly increased, and reached the highest points on the 19th and 13th day, respectively, then recovered to the level of control after re-watering. Moreover, T/C of MDA in C. kousa reached 192.00%, far above 130.61% in C. florida on the 19th day (Fig. 4a), two-ways ANOVA also showed a significance of interspecies (P = 0.01), suggesting more peroxidation of membrane occurred in C. kousa due to prolonged drought. Although T/C of SOD in C. kousa was slightly higher than that in C. florida on the 13th day, no significance (P = 0.12) was detected between two species (Fig. 4b). Notably, T/C of SODs in both dogwoods slightly declined on the 19th day, showing the rate of reactive oxygen species (ROS) production in two species almost exceeded scavenging ability. Apparently, outstanding increments of T/C of SSC in C. florida (T/C = 193.03%) and C. kousa (T/C = 315.26%) were found on the 19th day (Fig. 4c). Moreover, T/C of SSC in C. kousa was down significantly, while it kept high level in C. florida after re-watering. However, no significance (P = 0.24) between two species was observed.

0 0

8

13

15

18

19

27

4. Discussion

Day Fig. 2. Changing patterns of (a) Ci and (b) WUEi during drought and re-watering treatment in C. florida and C. kousa seedlings. Continuous drought for 19 days, then re-watering for one week. Letters with same color indicate statistical results among different stages in same species, the same letter denotes no significant difference among different stages of treatment according to Duncan's new multiple range test (P b 0.05).

4.1. Fluctuation of photosynthetic indicators is the initial response to drought stress Stomatal closure is one of the earliest responses to drought stress and mainly controlled by chemical signals – abscisic acid [6]. Stomata

Please cite this article as: Q. Lu, J. Xu, X. Fu, et al., Physiological and growth responses of two dogwoods to short-term drought stress and rewatering, Acta Ecologica Sinica, https://doi.org/10.1016/j.chnaes.2019.05.001

Q. Lu et al. / Acta Ecologica Sinica xxx (2019) xxx

T/C of MDA (%)

C. florida

(a)

220

C. kousa

a

200 180 160 140 120

bc

100 80

b

a

b

b

b

c

b 8

13

19

27

Day

T/C of SOD (%)

(b)

110

a ab

ab a

105

b

100

b abc

ab

bc

c

95 90

0

8

13

19

27

Day (c)

450

a

T/C of SSC (%)

400 350

a

300 250 200

b b

100 50 0

b

ab

b b 8

Day

4.2. Increment of SOD activity, MDA and SSC content enhancing drought tolerance Increment of antioxidant enzymes activities in stressed-plants can protect photosynthetic apparatus against unfavorable effects of ROS [34]. Among these indicators, SOD plays a crucial role and is regarded as the first line of defense scavenging active oxygen free radicals [35,36]. MDA content reflects the degree of membrane lipid peroxidation [37]. In two dogwoods, opposite changes in SODs and MDAs happened when suffered from moderate to severe drought stress (13 ~ 19th day) (Fig. 4a–b). Such negative correlation between SODs and MDAs also was observed in rice under Cd stress [38]. Compared with native C. kousa, responses of SOD and MDA to drought stress in introduced C. florida seemed to be weaker (Fig. 4a–b). It is vital physiological adaptation mechanisms for plants through osmotic adjustment in terms of accumulating compatible low molecular weight osmolytes under drought condition [39]. In the present study, SSCs of dogwoods increased gradually to maximum on the 19th day of drought treatment (Fig. 4c). However, high SSC in C. florida after rewatering shows hysteresis phenomenon of osmotic adjustment recovery.

a

b

150

drought stress was related to the biological characteristics of species and the increase of chlorophyll content might be a physiological adaptation mechanism of maintaining photosynthetic rate under drought stress [31]. The significant increment in chlorophyll content of C. kousa in this study was consistent with that of Ren et al. [32]. Therefore, more chlorophyll content accumulation in drought-stress seedlings of C. kousa suggests that it has more effective ways to avoid the damage of photo-oxidation and ROS induced by drought than C. florida [33].

c

0

115

5

13

19

27

Fig. 4. Changing patterns of (a) MDA, (b) SOD and (c) SSC during drought and re-watering treatments in C. florida and C. kousa seedlings. Continuous drought for 19 days, then rewatering for one week. Letters with same color indicate statistical results among different stages in same species, the same letter denotes no significant difference among different stages of treatment according to Duncan's new multiple range test (P b 0.05).

are regarded as a key to the control of water balance in plants under water deficit stress [18], and their closures limit water loss and CO2 assimilation, thereby reducing Pn, Gs and Ci, as well as improving WUEi in drought-stressed plants [19]. Reduction in Ci and increment in WUEi of C. florida on the 19th day of drought stress, followed by recovery on the 27th day (Fig. 2) are in parallel to the seedlings of Torreya grandis [20] and Pinus halepensis [21]. Compared with native C. kousa, the rapid stomatal closure and the increase of WUEi were the responses of C. florida to drought stress. Moreover, recover quickly after re-watering also suggests it has the adaptive potential to prolonged drought. Such result is supported by Chartzoulakis et al. [22] and Pourghayoumi et al. [23]. Chlorophyll fluorescence can be used as a probe of photosynthesis and indicator of stress resistance under adverse conditions [24]. Drought-tolerant plants endure drought by down-regulating Fv/Fm avoiding oxidative stress [25,26]. In this study, similar downregulating trends in Fv/Fm and qP were observed in drought-stressed seedlings of two dogwoods (Fig. 3), which are consistent with the reports in Vetiveria zizanioides [27], Fagus sylvatica [28], Sinocalycanthus Chinensis [29] and Ziziphus mauritiana [9]. Additionally, photosynthetic pigment is the material basis of plant photosynthesis, and its composition and content directly affect the photosynthesis of leaves [30]. The change of chlorophyll content under

4.3. Changes in morphological variables are both the cause and result of drought stress The declining tendencies of LRWCs in response to drought stress are similar in two dogwoods, in parallel to the findings in Dendrobium moniliforme [40]. Earlier closures of stomata (on the 8th day) induced lower stomatal conductance and transpiration rate, resulting in higher LRWC and SRWC in C. florida than in C. kousa on the 19th day of treatment (Fig. 1, Fig. 2a). To prohibit the loss of water and absorb more water from soil, drought-tolerant plants tend to shrink aboveground parts (leaf and stem) and develop more enormous root system [41,42]. It is proved by results in Callistemon [8], C. kousa [43], and our results in dogwoods (Table 1; Table 2). Moreover, similar biomass distribution in upregulation T/C of root/shoot ratio in two dogwoods provides stronger support for alien C. florida with the possibility of successful introduction. 5. Conclusions Overall, C. florida displays a weaker performance than C. kousa under drought stress. However, most of physiological parameters can recover to the normal level after re-watering. Therefore, we guess that flowering dogwood (C. florida) and its cultivars possess drought adaptive potential for introducing to southern China. Besides drought stress, high temperature and high humidity during summer in southern China may be the other fatal climatic factors for C. florida survival. Thus, more effective ways, such as grafting on East-Asia dogwoods with strong resistance, should be considered to improve survival rate and ornamental value of flowering dogwoods and its cultivars. Declarations of interest None.

Please cite this article as: Q. Lu, J. Xu, X. Fu, et al., Physiological and growth responses of two dogwoods to short-term drought stress and rewatering, Acta Ecologica Sinica, https://doi.org/10.1016/j.chnaes.2019.05.001

6

Q. Lu et al. / Acta Ecologica Sinica xxx (2019) xxx

Acknowledgements This research was funded by “948” Project (grant number 2015-414), Jiangsu Provincial Independent Innovation Funds of Agricultural Science and Technology (Project Number CX (16) 1005) and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD). References [1] C.A. Jaleel, P. Manivannan, A. Wahid, M. Farooq, H.J. Al-Juburi, R. Somasundaram, R. Panneerselvam, Drought stress in plants: a review on morphological characteristics and pigments composition, Int. J. Agric. Biol. 11 (1) (2009) 100–105 (doi:08–305/ IGC-DYT/2009/11–1–100–105.). [2] F.K. Farooq, H.S. Mohammad, E. Ahmad, Changes in some physiological and osmotic parameters of several pistachio genotypes under drought stress, Sci. Hortic. 198 (2016) 44–51, https://doi.org/10.1016/j.scienta.2015.11.028. [3] A. Nosalewicz, J. Siecińska, M. Śmiech, M. Nosalewicz, D. Wiącek, A. Pecio, D. Wach, Transgenerational effects of temporal drought stress on spring barley morphology and functioning, Environ. Exp. Bot. 131 (2016) 120–127, https://doi.org/10.1016/j. envexpbot.2016.07.006. [4] E.M. Fard, B. Bakhshi, R. Keshavarznia, N. Nikpay, M. Shahbazi, G.H. Salekdeh, Drought responsive microRNAs in two barley cultivars differing in their level of sensitivity to drought stress, Plant Physiol. Biochem. 118 (2017) 121–129, https://doi. org/10.1016/j.plaphy.2017.06.007. [5] Ş. Akıncı, D.M. Lösel, Plant water-stress response mechanisms, in: I.M.M. Rahman, H. Hasegawa (Eds.), Water Stress, InTech Publishers, Croatia 2012, pp. 15–42. [6] S.Y.S. Lisar, R. Motafakkerazad, M.M. Hossain, I.M.M. Rahman, Water stress in plants: causes, effects and responses, in: I.M.M. Rahman, H. Hasegawa (Eds.), Water Stress, InTech Publishers, Croatia 2012, pp. 1–14. [7] S. Bhattacharjee, A.K. Saha, Plant water-stress response mechanisms, in: R.K. Gaur, P. Sharma (Eds.), Approaches to Plant Stress and their Management, Springer Publishers, India 2014, pp. 149–172. [8] S. Álvarez, A. Navarro, E. Nicolás, M.J. Sánchez-Blanco, Transpiration, photosynthetic responses, tissue water relations and dry mass partitioning in Callistemon plants during drought conditions, Sci. Hortic. 129 (2) (2011) 306–312, https://doi.org/10. 1016/j.scienta.2011.03.031. [9] M. Kulkarni, B. Schneider, E. Raveh, N. Tel-Zur, Leaf anatomical characteristics and physiological responses to short-term drought in Ziziphus mauritiana (Lamk.), Sci. Hortic. 124 (3) (2010) 316–322, https://doi.org/10.1016/j.scienta.2010.01.005. [10] Y. Tugendhaft, A. Eppel, Z. Kerem, O. Barazani, A. Ben-Gal, J.W. Kadereit, A. Dag, Drought tolerance of three olive cultivars alternatively selected for rain fed or intensive cultivation, Sci. Hortic. 199 (2016) 158–162, https://doi.org/10.1016/j.scienta. 2015.12.043. [11] Q.Y. Xiang, S.J. Brunsfeld, D.E. Soltis, P.S. Soltis, Phylogenetic relationships in Cornus based on chloroplast DNA restriction sites: implications for biogeography and character evolution, Syst. Bot. 21 (4) (1996) 515–534. [12] M.A. Jenkins, P.S. White, Cornus florida L. mortality and understory composition changes in western great smoky mountains national park, J. Torrey Bot. Soc. 129 (3) (2002) 194–206, https://doi.org/10.2307/3088770. [13] F.S. Santamour Jr., A.J. McArdle, Cultivar checklists of the large-bracted dogwoods: Cornus florida, C. kousa, and C.Nuttallii, J. Arboric. 11 (1985) 29–36. [14] X.X. Fu, H.N. Liu, X.D. Zhou, X.L. Shang, Seed dormancy mechanism and dormancy breaking techniques for Cornus kousa var. chinensis, Seed Sci. Technol. 41 (3) (2013) 458–463, https://doi.org/10.15258/sst.2013.41.3.12. [15] X.X. Fu, H.N. Liu, J. Xu, J.J. Tang, X.L. Shang, Primary metabolite mobilization and hormonal regulation during seed dormancy release in Cornus japonica var. chinensis, Scand. J. Forest Res. 29 (6) (2014) 542–551, https://doi.org/10.1080/02827581. 2014.922608. [16] N.R. Baker, E. Rosenqvist, Applications of chlorophyll fluorescence can improve crop production strategies: an examination of future possibilities, J. Exp. Bot. 55 (403) (2004) 1607–1621, https://doi.org/10.1093/jxb/erh196. [17] X.K. Wang, J.L. Huang, Principles and Techniques of Plant Physiological Biochemical Experiment, 3rd ed. Higher Education Press, Beijing, 2015. [18] C. Belin, S. Thomine, J.I. Schroeder, Water balance and the regulation of stomatal movements, in: A. Pareek, S.K. Sopory, H.J. Bohnert, Govindjee (Eds.), Abiotic Stress Adaptation in Plants: Physiological, Molecular and Genomic Foundation, Springer Publishers, Dordrecht 2010, pp. 283–305, https://doi.org/10.1007/978-90-4813112-9_14. [19] W.L. Gonzáles, L.H. Suárez, M.A. Molina-Montenegro, E. Gianoli, Water availability limits tolerance of apical damage in the Chilean tarweed Madia sativa, Acta Oecol. 34 (1) (2008) 104–110, https://doi.org/10.1016/j.actao.2008.04.004. [20] C.H. Shen, Y.Y. Hu, X.H. Du, T.T. Li, H. Tang, J.S. Wu, Salicylic acid induces physiological and biochemical changes in Torreya grandis cv. Merrillii seedlings under drought stress, Trees 28 (4) (2014) 961–970, https://doi.org/10.1007/s00468-014-1009-y.

[21] T. Klein, G.D. Matteo, E. Rotenberg, S. Cohen, D. Yakir, Differential ecophysiological response of a major Mediterranean pine species across a climatic gradient, Tree Physiol. 33 (1) (2013) 26–36, https://doi.org/10.1093/treephys/tps116. [22] K. Chartzoulakis, A. Patakas, G. Kofidis, A. Bosabalidis, A. Nastou, Water stress affects leaf anatomy, gas exchange, water relations and growth of two avocado cultivars, Sci. Hortic. 95 (1) (2002) 39–50, https://doi.org/10.1016/S0304-4238(02)00016-X. [23] M. Pourghayoumi, D. Bakhshi, M. Rahemi, A.A. Kamgar-Haghighi, A. Aalami, The physiological responses of various pomegranate cultivars to drought stress and recovery in order to screen for drought tolerance, Sci. Hortic. 217 (2017) 164–172, https://doi.org/10.1016/j.scienta.2017.01.044. [24] Y.B. Jiang, Y.R. Yang, Q.H. Zheng, Effects of exogenous nitric oxide on antioxidase and chlorophyll fluorescence of seedling of alfalfa under drought stress, Agric. Res. Arid Areas. 26 (2) (2008) 65–68. [25] I. Voss, S. Bobba, R. Scheibe, A.S. Raghavendra, Emerging concept for the role of photorespiration as an important part of abiotic stress response, Plant Biol. 15 (4) (2013) 713–722, https://doi.org/10.1111/j.1438-8677.2012.00710.x. [26] K. Taïbi, del.A.D. Campo, A. Vilagrosa, J.M. Bellés, M.P. López-Gresa, D. Pla, J.J. Calvete, J.M. López-Nicolás, J.M. Mulet, Drought tolerance in Pinus halepensis seed sources as identified by distinctive physiological and molecular markers, Front. Plant Sci. 8 (2017) 1–13, https://doi.org/10.3389/fpls.2017.01202. [27] Y. Liu, Q.Q. Huang, B.Y. Ma, L.G. Xu, Changes of photosynthesis and physiological index in Vetiveria zizanioides under heat and drought stress, Forest Res. 19 (5) (2006) 638–642, https://doi.org/10.13275/j.cnki.lykxyj.2006.05.019. [28] A. Gallé, U. Feller, Changes of photosynthetic traits in beech saplings (Fagus sylvatica) under severe drought stress and during recovery, Physiol. Plant. 131 (3) (2007) 412–421, https://doi.org/10.1111/j.1399-3054.2007.00972.x. [29] S.S. Ke, Z.X. Jin, Effect of drought stress and water recovering on physiological characteristics of Sinocalycanthus Chinensis seedlings, Plant Nutr. Fert. Sci. 13 (6) (2007) 1166–1172. [30] H. LI S, M. LI, D. ZHANG W, Y.M. Li, X.Z. Ai, B.B. Liu, Q.M. Li, Effects of CO2 enrichment on photosynthetic characteristics and reactive oxygen species metabolism in leaves of cucumber seedlings under salt stress, Acta Ecol. Sin. 39 (6) (2019) 1–9, https:// doi.org/10.5846/stxb201712212296. [31] R. Rosales-Serna, J. Kohashi-Shibata, J.A. Acosta-Gallegos, C. Trejo-López, J. OrtizCereceres, J.D. Kelly, Biomass distribution, maturity acceleration and yield in drought stressed common bean cultivars, Field Crop Res. 85 (2/3) (2004) 203–211, https://doi.org/10.1016/S0378-4290(03)00161-8. [32] L. Ren, X.L. Zhao, J. Xu, H.Y. Zhang, Y.H. Guo, F.L. Guo, C.L. Zhang, J.H. Lü, Varied morphological and physiological responses to drought stress among four tea Chrysanthemum cultivars, Acta Ecol. Sin. 35 (15) (2015) 5131–5139, https://doi.org/10. 5846/stxb201401220164. [33] A. Vilagrosa, F. Morales, A. Abadía, J. Bellot, H. Cochard, E. Gil-Pelegrin, Are symplast tolerance to intense drought conditions and xylem vulnerability to cavitation coordinated? An integrated analysis of photosynthetic, hydraulic and leaf level processes in two Mediterranean drought-resistant species, Environ. Exp. Bot. 69 (3) (2010) 233–242, https://doi.org/10.1016/j.envexpbot.2010.04.013. [34] H. Upadhyaya, B.K. Dutta, L. Sahoo, S.K. Panda, Comparative effect of Ca, K, Mn and B on post-drought stress recovery in tea [Camellia sinensis (L.) O. Kuntze], Am. J. Plant Sci. 3 (4) (2012) 443–460, https://doi.org/10.4236/ajps.2012.34054. [35] R.G. Alscher, N. Erturk, L.S. Heath, Role of superoxide dismutases (SODs) in controlling oxidative stress in plants, J. Exp. Bot. 53 (372) (2002) 1331–1341, https://doi. org/10.1093/jexbot/53.372.1331. [36] M. Tian, L.B. Rao, J.Y. Li, Reactive oxygen species (ROS) and its physiological functions in plant cells, Plant Physiol. J. 41 (2) (2005) 235–238, https://doi.org/10. 13592/j.cnki.ppj.2005.02.038. [37] F.F. Khoyerdi, M.H. Shamshiri, A. Estaji, Changes in some physiological and osmotic parameters of several pistachio genotypes under drought stress, Sci. Hortic. 198 (26) (2016) 44–51, https://doi.org/10.1016/j.scienta.2015.11.028. [38] X.F. Zhang, D.Y. Wang, K.F. Chu, C.G. Yang, R.X. Mou, M.X. Chen, Z.W. Zhu, Q.F. He, X.Y. Liao, Changes of SOD activity and MDA content in rice exposed to Cd stress as affected by genotype, Chinese J. Rice Sci. 20 (2) (2006) 194–198, https://doi.org/ 10.16819/j.1001-7216.2006.02.014. [39] J.M. Morgan, Osmoregulation and water stress in higher plants, Annu. Rev. Plant Biol. 35 (1) (2003) 299–319, https://doi.org/10.1146/annurev.pp.35.060184. 001503. [40] X.L. Wu, J. Yuan, A.X. Luo, Y. Chen, Y.J. Fan, Drought stress and re-watering increase secondary metabolites and enzyme activity in Dendrobium moniliforme, Ind. Crop. Prod. 94 (30) (2016) 385–393, https://doi.org/10.1016/j.indcrop.2016.08.041. [41] C.M. Hudak, R.P. Patterson, Root distribution and soil moisture depletion pattern of a drought-resistant soybean plant introduction, Agron. J. 88 (3) (1996) 478–485, https://doi.org/10.2134/agronj1996.00021962008800030020x. [42] H. Ding, Z.M. Zhang, L.X. Dai, T. Kang, D.W. Ci, W.W. Song, Effects of drought stress on the root growth and development and physiological characteristics of peanut, Chinese J. Appl. Ecol. 24 (6) (2013) 1586–1592, https://doi.org/10.13287/j.10019332.2013.0335. [43] F. Wang, H. Yamamoto, Transpiration surface reduction of Kousa dogwood trees during serious water imbalance, J. Forestry Res. 20 (4) (2009) 337–342, https:// doi.org/10.1007/s11676-009-0057-4.

Please cite this article as: Q. Lu, J. Xu, X. Fu, et al., Physiological and growth responses of two dogwoods to short-term drought stress and rewatering, Acta Ecologica Sinica, https://doi.org/10.1016/j.chnaes.2019.05.001