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Article

Coordinated Regulation of Photosynthesis, Stomatal Traits, and Hormonal Dynamics in Camellia oleifera During Drought and Rehydration

by
Linqing Cao
1,2,
Chao Yan
1,2,*,
Tieding He
1,2,
Qiuping Zhong
1,2,
Yaqi Yuan
1,2 and
Lixian Cao
1,2
1
Experimental Center of Subtropical Forestry, Chinese Academy of Forestry, Xinyu 338000, China
2
Key Laboratory of Cultivation and Utilization for Oil-Camellia Resources, Xinyu 338000, China
*
Author to whom correspondence should be addressed.
Biology 2025, 14(8), 965; https://doi.org/10.3390/biology14080965
Submission received: 6 June 2025 / Revised: 30 June 2025 / Accepted: 29 July 2025 / Published: 1 August 2025
(This article belongs to the Section Plant Science)
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Simple Summary

Camellia oleifera is an important woody oil plant in southern China. However, its cultivation in subtropical mountainous regions is often constrained by seasonal droughts. Therefore, it is crucial to evaluate the physiological and ecological response mechanisms of Camellia oleifera under drought and rehydration conditions. In this study, we systematically characterized the photosynthetic performance, stomatal morphology, and endogenous hormone responses of two Camellia oleifera cultivars with contrasting drought resistance under simulated natural drought–rehydration cycles. The drought-tolerant cultivar exhibited enhanced physiological recovery and a pronounced photosynthetic compensation effect following rehydration, highlighting its superior drought adaptability and physiological resilience. This aids in revealing the mechanism of plant adaptation to drought–rehydration.

Abstract

Camellia oleifera, a woody oilseed species endemic to China, often experiences growth constraints due to seasonal drought. This study investigates the coordinated regulation of photosynthetic traits, stomatal behavior, and hormone responses during drought–rehydration cycles in two cultivars with contrasting drought resistance: ‘CL53’ (tolerant) and ‘CL40’ (sensitive). Photosynthetic inhibition resulted from both stomatal and non-stomatal limitations, with cultivar-specific differences. After 28 days of drought, the net photosynthetic rate (Pn) declined by 26.6% in CL53 and 32.6% in CL40. A stable intercellular CO2 concentration (Ci) in CL53 indicated superior mesophyll integrity and antioxidant capacity. CL53 showed rapid Pn recovery and photosynthetic compensation post-rehydration, in contrast to CL40. Drought triggered extensive stomatal closure; >98% reopened upon rehydration, though the total stomatal pore area remained reduced. Abscisic acid (ABA) accumulation was greater in CL40, contributing to stomatal closure and Pn suppression. CL53 exhibited faster ABA degradation and gibberellin (GA3) recovery, promoting photosynthetic restoration. ABA negatively correlated with Pn, transpiration rate (Tr), stomatal conductance (Gs), and Ci, but positively with stomatal limitation (Ls). Water use efficiency (WUE) displayed a parabolic response to ABA, differing by cultivar. This integrative analysis highlights a coordinated photosynthesis–stomata–hormone network underlying drought adaptation and informs selection strategies for drought-resilient cultivars and precision irrigation.

1. Introduction

Drought is a major abiotic stressor that limits plant growth, development, and geographical distribution [1]. Plants adopt multifaceted resistance to counter water deficit, including drought escape, avoidance, and tolerance mechanisms [2]. Osmotic adjustment under drought stress is achieved by accumulating compatible solutes (e.g., proline, soluble proteins), which help maintain cell turgor. Simultaneously, activation of antioxidant defense systems, including superoxide dismutase (SOD) and peroxidase (POD), mitigates oxidative damage and maintains membrane integrity [3,4,5]. Abscisic acid (ABA) is central in mediating stomatal closure and inducing stress-responsive gene expression among endogenous hormones. Other phytohormones, including auxins (IAA) and gibberellins (GA), also contribute to drought adaptation [6]. As key regulators of CO2 uptake and water vapor loss, stomata undergo dynamic adjustments to balance photosynthesis and transpiration under drought conditions [7]. Drought-induced stomatal closure, governed by changes in guard cell wall mechanics, ion channel activity, and cytoskeletal organization [8], reduces water loss but concurrently restricts photosynthetic carbon assimilation, inhibiting growth. Photosynthesis is highly sensitive to drought, with inhibition arising from stomatal and non-stomatal limitations [9]. Under mild stress, reduced stomatal conductance (Gs) limits CO2 availability, lowering the net photosynthetic rate (Pn). Under moderate-to-severe stress, stomatal and non-stomatal constraints disrupt photochemical activity, often through impaired mesophyll function, Rubisco inactivation, and damage to photosystem II (PSII) [10,11]. Following rehydration, photosynthesis limited by stomatal factors typically recovers quickly, sometimes with compensatory overcorrection. In contrast, the recovery of non-stomatal limitation requires cells to complete damage clearance, molecular regeneration, membrane system reconstruction, and metabolic network rebalancing. These processes are far more complex and time-consuming than regulating stomatal conductance, and the extent of recovery varies depending on the drought resistance of the species [12,13].
Camellia oleifera, a major woody oilseed crop in southern China, produces seed oil rich in unsaturated fatty acids and vitamin E, offering significant nutritional, medicinal, and cosmetic value [14]. However, its cultivation in subtropical mountainous regions is frequently constrained by seasonal droughts that impair photosynthetic efficiency, disrupt flower bud differentiation, and compromise fruit development [11,15,16,17], ultimately threatening yield stability and quality. Severe and prolonged drought can even lead to tree mortality. Although previous studies have examined drought effects on C. oleifera morphology [18,19], physiology [20,21,22,23], and molecular responses [24,25,26], the following critical knowledge gaps remain. (1) Most investigations address isolated stress phases, overlooking integrated responses among photosynthesis, stomatal behavior, and hormonal regulation during dynamic drought–rehydration cycles. (2) Drought resistance is often assessed using static indicators, lacking systematic analysis of post-rehydration physiological recovery, and (3) the mechanistic basis underlying cultivar-specific differences in drought resistance remains poorly characterized, limiting progress in elite cultivar selection and cultivation strategies.
To address these gaps, we employed two C. oleifera cultivars with contrasting drought resistance, ‘CL53’ (tolerant) and ‘CL40’ (sensitive), as model systems. By simulating natural drought–rehydration cycles and integrating analyses of photosynthetic traits, stomatal responses, and endogenous hormone dynamics, we aimed to achieve the following: (1) elucidate the coordinated regulatory network linking photosynthesis, stomatal conductance, and hormone signaling under drought and rehydration; and (2) identify physiological recovery strategies distinguishing drought-tolerant and drought-sensitive cultivars. These findings offer a theoretical framework for evaluating drought resistance, improving water management, and guiding post-drought recovery in C. oleifera cultivation.

2. Materials and Methods

2.1. Study Area and Plant Material

The experiment was conducted at the Experimental Center of Subtropical Forestry, Chinese Academy of Forestry (27°33′–28°08′ N, 114°29′–114°51′ E), located at No. 460, Qianshan West Road, Fenyi County, Xinyu City, Jiangxi Province, China. This region experiences a subtropical humid monsoon climate, characterized by an average annual sunshine duration of 1655.4 h, a mean annual temperature of 17.2 °C (maximum recorded: 40.1 °C), and average annual precipitation of 1594.8 mm. Rainfall distribution is uneven across seasons, with over 60% occurring between April and June, often resulting in recurrent autumn droughts.
Two C. oleifera cultivars with contrasting drought resistance were selected, ‘CL53’, a drought-tolerant cultivar with a dwarf growth habit, open canopy architecture, and thick, leathery leaves, and ‘CL40’, a drought-sensitive cultivar characterized by vigorous growth, upright canopy structure, and moderate drought tolerance. Three-year-old container-grown saplings, established in early 2018 under uniform fertilization and irrigation conditions, were used for the study. Twelve healthy and morphometrically uniform individuals per cultivar were selected for experimentation (Table 1).

2.2. Experimental Design

The experiment was initiated in July, 2022 to simulate natural drought conditions using mobile rainout shelters that were deployed during rainfall and retracted during sunny periods. Test trees were bordered by protective rows of C. oleifera (Figure 1). Soil relative water content (RWC) was monitored weekly at depths of 0–20 cm, 20–40 cm, and 40–60 cm using the ring knife method. After approximately three months, soil RWC stabilized at ~25%, at which point two treatment groups were established—one maintained under continued drought and the other subjected to rehydration. The rehydrated group received an initial irrigation of 100 L per plant, followed by four weekly irrigations of 50 L each, administered between 16:00–17:00. Four treatment groups were thus implemented: drought-stressed CL53 (DS-53), rehydrated CL53 (RW-53), drought-stressed CL40 (DS-40), and rehydrated CL40 (RW-40). As shown in Figure 2, RWC in rehydrated soils was maintained between 50% and 65% for seven days post-irrigation, whereas RWC in drought-stressed soils declined from 25% to ~16%. Photosynthetic and related physiological parameters were measured at 0, 7, 14, 21, and 28 days after rehydration initiation.

2.3. Determination of Leaf Relative Water Content

Leaves were sampled from the upper 3–5 whorls of C. oleifera spring shoots under similar growth conditions, with three biological replicates and 10 leaves per treatment. Following surface cleaning, fresh weight (Wf) was recorded immediately. Leaves were then immersed in distilled water for 24 h, blotted dry with absorbent paper, and weighed to obtain the saturated weight (Wt). Subsequently, leaves were blanched at 105 °C for 15 min, dried at 80 °C to constant weight, and the dry weight (Wd) recorded. Leaf relative water content (LRWC) was calculated as LRWC (%) = [(Wf − Wd)/(Wt − Wd)] × 100.

2.4. Measurement of Photosynthetic Parameters

Photosynthetic parameters were assessed in three C. oleifera plants per treatment. Six fully expanded, mature leaves were selected from the upper-middle canopy of each plant. Measurements were conducted between 09:00–11:00 on cloudless days using a Li-6800 portable photosynthesis system (LI-COR, Lincoln, NE, USA), under standardized chamber conditions: photosynthetic photon flux density at 1000 μmol·m−2·s−1, CO2 concentration (Ca) at 400 μmol·mol−1, leaf chamber temperature at 25 °C, and relative humidity maintained between 55% and 65%. Measured parameters included Pn, transpiration rate (Tr), Gs, and intercellular CO2 concentration (Ci). Derived indices included water use efficiency (WUE = Pn/Tr) and stomatal limitation (Ls = 1 − Ci/Ca).

2.5. Stomatal Characteristic Measurements

Leaves of comparable developmental stage were harvested from the upper 3–5 whorls of spring shoots on day 28 post-treatment initiation. Lamina segments (5 × 5 mm) adjacent to the midrib (Figure 3) were excised and immediately fixed in FAA solution (70% ethanol:formaldehyde:glacial acetic acid, 90:5:5 v/v), then stored at 4 °C. After ≥24-h fixation, samples were rinsed three times (15 min each) with 0.1 M phosphate buffer (PB, pH 7.4), post-fixed in 1% osmium tetroxide (in PB) under dark conditions for 1–2 h at room temperature, and rinsed again with PB. Samples were dehydrated in a graded ethanol series (30% to 100%, 15 min per step), transitioned through isopentyl acetate, and subjected to critical point drying. Specimens were gold-coated for 30 s using an ion sputter coater and observed under an SU8100 field-emission scanning electron microscope (Hitachi, Tokyo, Japan). For each treatment, five replicates were examined across three randomly selected fields of view. Stomatal density and aperture dimensions were quantified using Imageview 1.0 software (iRay, Shanghai, China). Stomatal area (SA) was calculated assuming elliptical geometry: SA = 1/2 SL × 1/2 SW × π, where SL and SW denote stomatal length and width, respectively [27]. Total stomatal pore area per unit leaf area was derived from the product of mean individual stomatal area and open stomatal density.

2.6. Endogenous Hormone Assays

Leaves with comparable developmental conditions were sampled from the upper 3–5 whorls of spring shoots. Twenty leaves per treatment were immediately wrapped in aluminum foil, flash-frozen in liquid nitrogen, and stored at −80 °C for subsequent analysis. ABA and gibberellic acid (GA3) levels were quantified using high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) (HPLC: Agilent Technologies Inc., Santa Clara, CA, USA; MS/MS: SCIEX, Framingham, MA, USA) [28], with three biological replicates per treatment.

2.7. Data Analysis

Data were analyzed using Microsoft Excel 2016 (Microsoft Corporation, Redmond, WA, USA) and SPSS 26.0 (IBM SPSS, Chicago, IL, USA). One-way ANOVA followed by Duncan’s multiple range test were used to assess differences in photosynthetic parameters, stomatal characteristics, and hormone concentrations among treatments (p < 0.05). An independent samples t-test was used to analyze the significant differences in stomatal structure among different varieties (p < 0.05). Five function models, exponential, linear, logarithmic, polynomial, and power, were evaluated for fitting ABA and photosynthetic parameter dynamics. Graphical representations were generated using Origin 2021 (OriginLab, Northampton, MA, USA).

3. Results

3.1. Effects of Drought and Rehydration on Leaf Relative Water Content in C. oleifera

Under drought stress, both C. oleifera cultivars exhibited a progressive decline in leaf relative water content (LRWC) (Table 2). No significant reduction in LRWC was observed during the initial 14 days of drought. Compared to initial values (Day 0), DS-53 and DS-40 showed decreases of 6.75% and 3.96%, respectively, on the 28th day of drought. Rehydration triggered significant recovery in both cultivars. CL53 demonstrated rapid restoration, with LRWC increasing from 75.37% to 81.69% within 7 days and subsequently stabilizing. In contrast, CL40 exhibited a more gradual recovery, with LRWC increasing from 75.21% to 83.39%. Throughout drought and rehydration phases (except Day 28), CL53 consistently maintained higher LRWC than CL40, indicating a stronger leaf water retention capacity.

3.2. Effects of Drought and Rehydration on Photosynthetic Parameters of C. oleifera

Drought and rehydration significantly influenced photosynthetic performance in both C. oleifera cultivars (Figure 4A). During the early drought phase (0–7 days), DS-53 showed a non-significant decline in Pn from 4.59 to 4.29 μmol·m−2·s−1 (−6.5%). Prolonged drought (28 days) led to a further reduction to 3.37 μmol·m−2·s−1 (–26.6%; p < 0.05), indicating cumulative inhibition. DS-40 was more sensitive, with significant reductions at all time points and an overall decline of 32.6% (from 4.42 to 2.98 μmol·m−2·s−1). CL53 exhibited superior drought tolerance, with attenuated Pn reductions and non-significant variation during later drought stages (14–28 days). Upon rehydration, both cultivars showed differential recovery. In RW-40, Pn plateaued after day 14 (8.15 μmol·m−2·s−1), whereas RW-53 exhibited a sustained, phased recovery, reaching 8.99 μmol·m−2·s−1 by day 21. Thus, CL53 demonstrated dual adaptive advantages: reduced Pn inhibition under drought and enhanced post-rehydration recovery.
Tr in both cultivars decreased progressively under drought (Figure 4B), stabilizing near 0.5 mmol·m−2·s−1. Rehydration significantly restored Tr, with peak recovery observed between days 14 and 21 after rewatering. Compared to initial values (Day 0), RW-53 and RW-40 showed increases of 458.6% and 383.2% at the peak recovery stage (Day 21), respectively.
Gs remained strongly suppressed under drought but increased markedly upon rehydration (Figure 4C). Compared to initial values (Day 0), RW-53 and RW-40 showed increases of 348.87% and 313.05%, respectively, on the 28th day of rehydration. Gs dynamics closely mirrored Tr trends, underscoring the role of stomatal limitation in constraining both gas exchange and transpiration during drought.
Ci declined in both cultivars during drought (Figure 4D). In CL53, changes were non-significant, whereas CL40 exhibited a significant 17.95% decrease (from 259.84 to 213.21 μmol·mol−1). Rehydration induced a rapid Ci increase in CL53 (+13.29% over 0–14 days), followed by a gradual rise, whereas CL40 displayed a slower, steady increase.
Ls increased gradually under drought, with significant early elevation (0–14 days) in CL40 but not in CL53 (Figure 4E). Rehydration progressively reduced Ls, with CL53 showing a larger overall reduction (29.69% vs. 18.55%) compared to initial values (Day 0). CL53 exhibited a more rapid initial decline, significant within 0–14 days, compared to the non-significant, slower decrease observed in CL40.
WUE declined under drought and, to a lesser extent, during rehydration (Figure 4F). Despite the stress-induced decrease, CL40 consistently maintained higher WUE than CL53 throughout the experiment.

3.3. Effects of Drought and Rehydration on Stomatal Characteristics of C. oleifera

Stomata in C. oleifera leaves, confined to the abaxial epidermis, regulate transpiration and gas exchange via elliptical to nearly circular apertures controlled by paired guard cells. Significant inter-cultivar differences in stomatal morphology and density were observed (Table 3). CL53 exhibited a lower stomatal density (230.37 mm−2, compared to 285.37 mm−2 of CL40) but significantly larger stomatal dimensions (length: 24.25 μm, width: 20.19 μm, area: 383.97 μm2) than CL40 (21.87 μm, 18.60 μm, 319.91 μm2, respectively). Drought–rehydration cycles markedly affected stomatal behavior. Drought stress induced widespread stomatal closure and aperture narrowing (Figure 5), while rehydration effectively restored stomatal functionality.
Prolonged drought significantly reduced both the stomatal density and aperture opening rate in both cultivars (Figure 6A). Under drought, CL53 had an aperture opening rate of 39.67% and a stomatal density of 97.01 mm−2, while CL40 exhibited a lower opening rate (33.42%) and slightly reduced density (95.47 mm−2); differences between cultivars were not statistically significant. After 21 days of rehydration, stomatal reopening exceeded 98% in both cultivars. However, stomatal density in rehydrated CL40 (280.18 mm−2) was significantly higher than in CL53 (219.77 mm−2).
Measurements of unit stomatal area under drought and rehydration (Figure 6B) revealed significant treatment-dependent variation. Drought stress substantially reduced stomatal pore area per unit leaf area: in CL53, the area declined to 1900.58 μm2·mm−2 (a 77.61% reduction vs. RW-53, 8489.94 μm2·mm−2); in CL40, the value decreased to 2464.15 μm2·mm−2 (a 76.74% reduction vs. RW-40, 10,594.55 μm2·mm−2). These results indicate that drought promotes stomatal closure as a water conservation mechanism. Although rehydration significantly restored stomatal area in both cultivars, the extent of recovery was cultivar dependent.

3.4. Effects of Drought and Rewatering on Endogenous Hormones in C. oleifera

Under drought conditions, ABA levels significantly increased in both C. oleifera cultivars (Table 4). After 28 days of sustained drought, ABA concentrations rose by 22.74% in ‘CL53’ and 30.65% in ‘CL40’. Following rewatering, ABA levels progressively declined, stabilizing after 21 days with reductions of 63.05% (CL53) and 66.78% (CL40) relative to drought-induced peaks. This dynamic modulation underscores the central role of ABA in coordinating drought stress responses and recovery.
Concurrently, GA3 content declined gradually in both cultivars under drought stress (Table 5), although changes were not statistically significant until Day 21. After rewatering, GA3 levels increased steadily, stabilizing after 14 days. Notably, CL53 exhibited a more rapid recovery in GA3 content, reflecting superior drought resilience.

3.5. Correlation Between Photosynthetic Characteristics and ABA Content in C. oleifera

Given the pronounced responsiveness of ABA to drought and rewatering, and its established role in regulating stomatal aperture through signal transduction pathways, we further evaluated the relationship between ABA content and photosynthetic parameters in C. oleifera (Figure 7). Five regression models (exponential, linear, logarithmic, polynomial, power) were tested, with the best-fitting model selected for each cultivar-variable combination.
A significant negative correlation was observed between ABA content and Pn (Figure 7A). For CL53, the data best fit an exponential decay model (y = −2.8095 + 15.8521 × e−0.0296x; R2 = 0.9212), while CL40 followed a polynomial model (y = 11.5058 − 0.2756x + 0.0019x2; R2 = 0.9629). The sharper decline in Pn in CL40 suggests greater ABA sensitivity compared to CL53.
Tr also exhibited significant negative correlations with ABA in both cultivars, conforming to power function models (Figure 7B): CL53 (y = 267.5508 × x–1.8375; R2 = 0.7896) and CL40 (y = 77.9072 × x−1.4251; R2 = 0.9763). The stronger fit in CL40 indicates a more pronounced ABA-mediated reduction in Tr.
Gs was significantly negatively correlated with ABA content (Figure 7C), with a power function best describing the trend in CL53 (y = 6.2072 × x−1.5224; R2 = 0.8596) and an exponential model fitting CL40 (y = 0.0209 + 0.3334 × 0.9103x; R2 = 0.9202).
Ci declined significantly with increasing ABA (Figure 7D), modelled linearly in CL53 (y = 329.9571 − 3.1528x; R2 = 0.9401) and polynomially in CL40 (y = 273.4619 + 1.0372x − 0.0482x2; R2 = 0.8909).
A significant positive correlation was observed between ABA and Ls (Figure 7E), fitting a linear model for CL53 (y = 0.1751 + 0.0079x; R2 = 0.9401) and a polynomial model for CL40 (y = 0.3163 − 0.0026x + 1.2054 × 10−4x2; R2 = 0.8909).
The relationship between ABA content and WUE followed polynomial trends in both cultivars (Figure 7F): CL53 (y = −9.8040 + 1.4304x − 0.0288x2; R2 = 0.8158) and CL40 (y = −2.0233 + 0.6158x − 0.0088x2; R2 = 0.8722). The parabolic curves suggest that WUE initially increased then declined with rising ABA concentrations, with CL40 attaining peak WUE at higher ABA levels than CL53.

4. Discussion

Drought is a predominant abiotic stressor affecting plant development and productivity [29,30]. Although C. oleifera is considered drought-tolerant, its cultivation in southern China’s hilly and mountainous regions is frequently challenged by hot, dry summers that limit growth and yield [31,32]. Plants exhibit intrinsic adaptive mechanisms under drought, enabling physiological and biochemical assessment of stress responses [33].
Photosynthesis, the central physiological process supplying carbon and energy substrates, is highly susceptible to drought-induced disruption of carbon metabolism [34,35,36]. In this study, drought markedly inhibited photosynthetic capacity in both C. oleifera cultivars, with distinct varietal responses reflecting underlying mechanistic complexity. During early drought (0–7 days), reduced Pn was primarily attributable to decreased Gs, indicating that stomatal limitation predominated [11]. After 28 days of sustained drought, the reduction in Pn was lower in CL53 (26.6%) than in CL40 (32.6%). The lack of significant changes in Ci indicates that the observed reduction in photosynthesis was predominantly attributable to impaired photosynthetic capacity within mesophyll cells. In contrast, the Pn of CL53 showed only a minor decrease, indicating that the mesophyll cells of CL53 could still sustain a high level of photosynthetic capacity under drought conditions [37].
Post-rehydration, recovery of Pn diverged between cultivars: CL53 showed a progressive increase, reaching 8.99 μmol·m−2·s−1, whereas CL40 plateaued after 14 days. The higher recovery rate and evident photosynthetic compensation in CL53 [38] contrast with the delayed response in CL40, which may reflect more severe chloroplast ultrastructural damage [9]. Ci dynamics in CL53 further indicated more complete alleviation of stomatal limitation, consistent with its greater drought resistance. Although WUE decreased during drought in both cultivars, CL40 consistently exhibited higher WUE than CL53, possibly because of greater stomatal pore density and more precise transpiration control [7]. However, this advantage did not translate to stronger drought resistance, suggesting that sustained photosynthetic carbon assimilation outweighs short-term water conservation during prolonged drought [39,40,41].
As key gas exchange regulators, stomata play a central role in drought adaptation [7,42]. In C. oleifera, drought induced pronounced stomatal closure, an adaptive response that restricts CO2 diffusion and limits photosynthesis [43]. Upon rehydration, both cultivars achieved >98% stomatal aperture reopening, but the recovery of open stomatal density and pore area per unit leaf surface differed. CL40 exhibited higher post-rehydration stomatal density and larger unit area pore size, which may facilitate more rapid gas exchange and photosynthetic recovery [44]. Differences in stomatal density may also impact plant responses to drought stress [45]. However, significant inter-varietal differences in stomatal morphology were observed. CL53 had fewer but larger stomata (greater length, width, and area) than CL40. These traits likely underlie cultivar-specific differences in stomatal regulation and drought responses [46], with drought-tolerant cultivars potentially optimizing stomatal dimensions to maintain higher conductance and photosynthetic rates under stress [47].
Endogenous phytohormones play essential roles in drought signaling, modulating synthesis, transport, and hormonal balance to regulate adaptive responses [33,48]. ABA accumulation is a hallmark of drought response, promoting stomatal closure and restricting growth and metabolism [49]. Drought significantly increased ABA levels in both cultivars, consistent with its role as a central regulator of stomatal behavior and stress-responsive gene expression [50,51]. Interestingly, the drought-sensitive CL40 accumulated more ABA than CL53, possibly reflecting excessive signaling that disrupts physiological coordination [52]. Following rehydration, ABA levels declined rapidly in both cultivars, with CL53 exhibiting faster ABA degradation and more pronounced GA3 recovery. This suggests that drought-tolerant cultivars more effectively reactivate gibberellin biosynthesis to support cell elongation and photosynthetic recovery [53]. GA3, an essential hormone for promoting plant growth, opposes ABA in the plant’s response to drought stress. GA3 facilitates stomatal opening, boosts CO2 absorption, and enhances photosynthetic efficiency [54]. This study revealed that drought induced a progressive decrease in GA3 levels in both varieties of C. oleifera, which was followed by a gradual increase upon rehydration. However, the extent of these changes was relatively minor, suggesting a less significant regulatory role for GA3 in photosynthetic capacity. Although CL40 maintained higher GA3 concentrations, potentially supporting vigorous growth, elevated GA3 under drought may exacerbate carbon expenditure and impair drought tolerance, contrasting with ABA-mediated conservation responses.
Significant correlations were identified between ABA and photosynthetic parameters: negative correlations with Pn, Tr, Gs, and Ci, consistent with previous findings [13], and a parabolic relationship with WUE (initial increase followed by decline). These relationships reinforce the regulatory role of ABA in C. oleifera photosynthesis. Varietal differences in ABA–photosynthesis correlations further reflect inherent divergence in drought resistance mechanisms and adaptive physiological strategies.

5. Conclusions

This study systematically characterized the photosynthetic performance, stomatal morphology, and endogenous hormone responses of two C. oleifera cultivars with contrasting drought resistance under simulated natural drought–rehydration cycles. The drought-tolerant cultivar exhibited enhanced physiological recovery and a marked photosynthetic compensation effect following rehydration, underscoring its superior drought adaptability and physiological resilience. These findings provide a theoretical basis for the selection of drought-tolerant cultivars and the implementation of precision water management practices. Future research should focus on elucidating the signal transduction pathways and gene regulatory networks underlying cultivar-specific drought responses. Additionally, integrating these insights with climate change models and water-use optimization strategies will be essential for establishing comprehensive frameworks to support the sustainable development of the C. oleifera industry.

Author Contributions

Conceptualization, L.C. (Linqing Cao) and C.Y.; methodology, L.C. (Linqing Cao); software, L.C. (Linqing Cao) and C.Y.; validation, Y.Y., L.C. (Lixian Cao) and T.H.; formal analysis, L.C. (Linqing Cao); investigation, T.H., Y.Y., L.C. (Linqing Cao) and L.C. (Lixian Cao); data curation, C.Y. and T.H.; writing—original draft preparation, L.C. (Linqing Cao); writing—review and editing, C.Y. and Q.Z.; supervision, Q.Z.; project administration, L.C. (Linqing Cao). All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the Fundamental Research Funds of CAF (CAFYBB2023ZA001-2), the Key R&D Program “Unveiling and Leading” Projects of Jiangxi Province (20223BBF61012), the Natural Science Foundation of Jiangxi Province (20242BAB20302), and the Oil-Camellia Special Research Project of the Jiangxi Provincial Department of Forestry (JXYCZX [2023]010201).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available within the article.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
ABAabscisic acid
ANOVAanalysis of variance
Caambient CO2 concentration
Ciintercellular CO2 concentration
CL53Camellia oleifera cultivar ‘CL53′
CL40Camellia oleifera cultivar ‘CL40′
DSdrought-stressed treatment
FAAformalin–acetic acid–alcohol fixative
GA3gibberellin A3
Gsstomatal conductance
LRWCleaf relative water content
Lsstomatal limitation value
PBphosphate buffer
Pnnet photosynthetic rate
PODperoxidase
PSIIphotosystem II
RWCsoil relative water content
SAindividual stomatal area
SODsuperoxide dismutase
SEMscanning electron microscopy
SLstomatal length
SWstomatal width
Trtranspiration rate
WUEwater-use efficiency

References

  1. Zhou, Q.; Li, Y.; Wang, X.; Yan, C.; Ma, C.; Liu, J.; Dong, S. Effects of different drought degrees on physiological characteristics and endogenous hormones of soybean. Plants 2022, 11, 2282. [Google Scholar] [CrossRef]
  2. Gupta, A.; Rico-Medina, A.; Caño-Delgado, A.I. The physiology of plant responses to drought. Science 2020, 368, 266–269. [Google Scholar] [CrossRef]
  3. He, F.; Liu, P.; Wang, L.; Du, L.; Qing, J.; Du, Q.; Du, H. Effect of drought stress and rewatering on physiological characteristics of Eucommia ulmoides seedling. Plant Physiol. J. 2021, 57, 661–671. [Google Scholar]
  4. Jin, S.; Peng, Z. Changes in response of carbon and water physiological parameters of Robinia pseudoacacia seedlings to long-term drought and re-hydration. J. Beijing For. Univ. 2023, 45, 43–56. [Google Scholar]
  5. Yu, X.; Wang, J.; Ma, W.; Yi, F.; Zhang, P. Synergy of osmotic adjustment and antioxidant activity in Catalpa bungei: Alleviating persistent drought stress from SL to NSL. Front. Plant Sci. 2025, 16, 1536795. [Google Scholar] [CrossRef] [PubMed]
  6. Ullah, A.; Manghwar, H.; Shaban, M.; Khan, A.H.; Akbar, A.; Ali, U.; Ali, E.; Fahad, S. Phytohormones enhanced drought tolerance in plants: A coping strategy. Environ. Sci. Pollut. Res. Int. 2018, 25, 33103–33118. [Google Scholar] [CrossRef] [PubMed]
  7. Driesen, E.; De Proft, M.; Saeys, W. Drought stress triggers alterations of adaxial and abaxial stomatal development in basil leaves increasing water-use efficiency. Hortic. Res. 2023, 10, uhad075. [Google Scholar] [CrossRef] [PubMed]
  8. Yang, Y.J.; Bi, M.H.; Nie, Z.F.; Jiang, H.; Liu, X.D.; Fang, X.W.; Brodribb, T.J. Evolution of stomatal closure to optimize water-use efficiency in response to dehydration in ferns and seed plants. New Phytol. 2021, 230, 2001–2010. [Google Scholar] [CrossRef]
  9. Gao, G.; Feng, Q.; Zhang, X.; Si, J.; Yu, T. An overview of stomatal and non-stomatal limitations to photosynthesis of plants. Arid. Zone Res. 2018, 35, 929–937. [Google Scholar]
  10. Hu, L.; Wang, Z.; Huang, B. Diffusion limitations and metabolic factors associated with inhibition and recovery of photosynthesis from drought stress in a C perennial grass species. Physiol. Plant. 2010, 139, 93–106. [Google Scholar] [CrossRef]
  11. Huang, Z.; Zhong, Q.; Cao, L.; Guo, H.; Yan, C.; Yuan, T.; Yuan, Y.; Luo, S. Effects of drought stress on photosynthesis of adult Camellia oleifera forest. Nonwood For. Res. 2017, 35, 72–79. [Google Scholar]
  12. Diao, Z.; Chen, H.; Feng, J.; Liu, W.; Wang, Y. Effects of drought stress on physiological and biochemical characteristics of Camellia oleifera seedlings. J. Anhui Agric. Univ. 2014, 41, 642–646. [Google Scholar]
  13. Zhao, N.; Lyu, J.; Li, S.; Xu, X.; Li, B.; Zhao, J.; Lu, S. Relationship between photosynthetic characteristics and endogenous abscisic acid content of Robinia pseudoacacia and Platyclus orientalis under different drought treatments. Acta Ecol. Sin. 2024, 44, 2100–2114. [Google Scholar]
  14. Tan, X.; Yan, C.; Zhong, Q.; Wan, X.; Yuan, Y.; Guo, H.; Cao, L.; Wang, J.; Ge, X.; Wang, J.; et al. Breeding, Promotion and application of improved oil-tea cultivar in China. World For. Res. 2023, 36, 108–113. [Google Scholar]
  15. Guo, P.R.; Wu, L.L.; Wang, Y.; Liu, D.; Li, J.A. Effects of drought stress on the morphological structure and flower organ physiological characteristics of Camellia oleifera flower buds. Plants 2023, 12, 2585. [Google Scholar] [CrossRef]
  16. Ding, S.; Zhong, Q.; Yuan, T.; Cao, L.; Yan, C.; Yuan, Y. Effects of endogenous hormones on Camellia oleifera leaves and fruit growth under drought stress. For. Res. 2016, 29, 933–939. [Google Scholar]
  17. Wang, R.; Zhong, F.; Liao, W.; Li, T. Effects of soil moisture on fruit growth of Camellia oleifera. Sci. Silvae Sin. 2014, 50, 40–46. [Google Scholar]
  18. Cao, L.; Zhong, Q.; Luo, S.; Yuan, T.; Guo, H.; Yan, C.; Yuan, Y. Variation in leaf structure of Camellia oleifera under drought stress. For. Res. 2018, 31, 136–143. [Google Scholar]
  19. Ding, S.; Zhong, Q.; Yuan, T.; Cao, L.; Yan, C.; Yuan, Y.; Z, X.; Lin, J. Effects of drought stress on flower bud growth and yield in Camellia oleifera. J. Nanjing For. Univ. (Natl. Sci. Ed.) 2017, 41, 197–202. [Google Scholar]
  20. Luo, Z.; Wang, H.; Chen, M.; Yuan, J. Effects of drought stress on physiological and biochemical characteristics of four Camellia oleifera varieties seedlings. Nonwood For. Res. 2019, 37, 104–113. [Google Scholar]
  21. Dong, B.; Hong, W.; Huang, Y.; Xue, L.; Gong, H.; Wei, X.; Lan, L. Physiological responses of four Camellia oleifera clones of Guangxi province in seeding stage under drought stress. J. Cent. South Univ. For. Technol. 2018, 38, 1–8. [Google Scholar]
  22. Feng, S.; Cheng, H.; Li, Q.; Zhou, Q.; Jia, X.; Ding, C. Physiological responses of three Camellia oleifera in seedling stage under drought stress. Acta Bot. Boreali-Occident. Sin. 2013, 33, 1651–1657. [Google Scholar]
  23. Yang, D.; Chen, Y.; Wang, R.; He, Y.; Ma, X.; Shen, J.; He, Z.; Lai, H. Effects of exogenous abscisic acid on the physiological and biochemical responses of Camellia oleifera seedlings under drought stress. Plants 2024, 13, 225. [Google Scholar] [CrossRef]
  24. Cao, R.; Li, Z.; Ouyang, W.; Hu, D.; Zhou, Z.; Su, W.; Chen, X.; Liu, J. Identification of NAC gene in Camellia oleifera and analysis of its response to drought stress. Acta Agric. Univ. Jiangxiensis 2021, 43, 1357–1370. [Google Scholar]
  25. Zhang, Z.; Xu, Y.; Liu, C.; Chen, L.; Zhang, Y.; He, Z.; Wang, R.; Xun, C.; Ma, Y.; Yuan, X.; et al. Cataloging the genetic response: Unveiling drought-responsive gene expression in oil tea camellia (Camellia oleifera Abel.) through transcriptomics. Life 2024, 14, 989. [Google Scholar] [CrossRef]
  26. He, Z.; Liu, C.; Zhang, Z.; Wang, R.; Chen, Y. Integration of mRNA and miRNA analysis reveals the differentially regulatory network in two different Camellia oleifera cultivars under drought stress. Front. Plant Sci. 2022, 13, 1001357. [Google Scholar] [CrossRef]
  27. Zhang, Q. Studies on the Mechanisms of the Responses of Stomatal Conductance and Photosynthesis to Different Light Environments in Oryza. Ph.D. Dissertation, Huazhong Agricultural University, Wuhan, China, 2020. [Google Scholar]
  28. Liu, N.; Zhao, H.; Hou, L.; Zhang, C.; Bo, W.; Pang, X.; Li, Y. HPLC-MS/MS-based and transcriptome analysis reveal the effects of ABA and MeJA on jujube (Ziziphus jujuba Mill.) cracking. Food Chem. 2023, 421, 136155. [Google Scholar] [CrossRef]
  29. Muhammad, I.; Shalmani, A.; Ali, M.; Yang, Q.H.; Ahmad, H.; Li, F.B. Mechanisms regulating the dynamics of photosynthesis under abiotic stresses. Front. Plant Sci. 2021, 11, 615942. [Google Scholar] [CrossRef]
  30. Daniel, V.C.; Eloy, N.L.; María, J.I.R.; Begoña, B.; Juan, M.R. Enhancing drought tolerance in lettuce: The efficacy of the seaweed-derived biostimulant cytolan® stress applied at different growth stages. Horticulturae 2025, 11, 157. [Google Scholar] [CrossRef]
  31. Lu, K.; Gu, Y.; Du, Y.; Yao, Y.; Tan, X.; Wu, L.; Zhou, J.; Yuan, J. NAC transcription factors are key regulators of brassinolide-enhanced drought tolerance in Camellia oil tree. BMC Plant biol. 2025, 25, 625. [Google Scholar] [CrossRef] [PubMed]
  32. Wang, Y.; Guo, P.R.; Sheng, S.; Li, J.; Yan, J. Identification of codreb genes for drought and cold tolerance in Camellia oleifera. Int. J. Plant Biol. 2023, 14, 228–241. [Google Scholar] [CrossRef]
  33. Zhao, N.; Zhao, J.; Li, S.; Li, B.; Lv, J.; Gao, X.; Xu, X.; Lu, S. The response of endogenous ABA and soluble sugars of Platycladus orientalis to drought and post-drought rehydration. Biology 2024, 13, 194. [Google Scholar] [CrossRef]
  34. Yang, F.; Lv, G. Responses of Calligonum leucocladum to prolonged drought stress through antioxidant system activation, soluble sugar accumulation, and maintaining photosynthetic homeostasis. Int. J. Mol. Sci. 2025, 26, 4403. [Google Scholar] [CrossRef] [PubMed]
  35. Yang, Y.; Fu, G.; Hao, W. Physiological responses and transcriptome analysis of Ammopiptanthus nanus to drought stress. Acta Ecol. Sin. 2025, 45, 854–865. [Google Scholar]
  36. Chen, X.; Wu, X.; Liu, S.; Hu, X.; Liu, C. Effects of AMF on photosynthetic characteristics and gene expressions of Tea plants under drought stress. Acta Hortic. Sin. 2024, 51, 2358–2370. [Google Scholar]
  37. Liu, B.; Liang, J.; Tang, G.; Wang, X.; Liu, F.; Zhao, D. Drought stress affects on growth, water use efficiency, gas exchange andchlorophyll fluorescence of Juglans rootstocks. Sci. Hortic. 2019, 250, 230–235. [Google Scholar] [CrossRef]
  38. Meng, Z.; Song, F.; Liu, Z.; Zhang, F. Effects of drought and re-watering at seedling stage on photosynthesis and chlorophyll fluorescence characteristics in rapeseed. Chin. J. Oil Crop Sci. 2012, 34, 40–47. [Google Scholar]
  39. Li, S. Study on the Mechanisms Underlying the Effects of Drought on Leaf Photosynthesis and Carbon Dioxide Diffusion Efficiency. Ph.D. Dissertation, Chinese Academy of Agricultural Sciences, Beijing, China, 2021. [Google Scholar]
  40. Chen, M.; Li, Y.; Wang, L.; Zhang, L.; Li, D.; Ju, J.; Yu, H. Photosynthetic responses to drought and subsequent re-watering in seedlings from two different provenances of Quercus variabilis Bl. Chin. J. Ecol. 2019, 38, 2950–2958. [Google Scholar]
  41. You, R.; Deng, X.; Hu, Y.; Ouyang, S.; Chen, L.; Xiang, W. Progress on physiological and ecological responses of trees to drought stress and re-watering. Sci. Silvae Sin. 2023, 59, 124–136. [Google Scholar]
  42. Chen, M.; Chen, L.; Li, S.; Xie, H.; Song, Y. Effects of drought stress on physiological characteristics and stomatal morphology of different cassava seedlings. J. Sichuan Agric. Univ. 2024, 42, 1049–1056+1084. [Google Scholar]
  43. Jin, S.; Peng, Z.; Zhang, S. The impact of varying degress of drought stress and re-hydration treatment on the physiological indicators of Robinia pseudoacacia seedlings. J. Northeast. For. Univ. 2024, 52, 27–39. [Google Scholar]
  44. He, X.; Zhou, W.; Qiu, F.; Gong, C.; Xu, L.; Xiao, X.; Wang, Y. Responses of different Camellia oleifera varieties to drought stress and the comprehensive evaluation of their drought resistance. J. Cent. South Univ. For. Technol. 2023, 43, 1–14. [Google Scholar]
  45. Zhong, Z.; Zhang, L.; Gao, S.; Peng, T. Leaf cytological characteristics and resistance comparison of four citrus rootstocks under drought stress. Acta Hortic. Sin. 2021, 48, 1579–1588. [Google Scholar]
  46. Zhou, Y.; Liu, H.; Zhang, S.; Liu, F.; Liu, N. Adaptation strategies of 29 species to sropical soral islands based on leaf anatomical traits. J. Trop. Subtrop. Bot. 2023, 31, 747–756. [Google Scholar]
  47. Cheng, L. Morphological Difference in Leaves of Various Apple (Malus Domestic) Cultivars and Its Correlation with Water-Use Efficiency Under Drought Stress. Master’s Thesis, Northwest A&F University, Xi’an, China, 2011. [Google Scholar]
  48. Zhu, B.; Xu, Q.; Ma, S.; Liu, B.; Duan, M.; Wang, L. Effect of potassium deficiency on endogenous hormones, photosynthesis and characteristics of chlorophyll fluorescence in Brassica napus under drought stress. Chin. J. Oil Crop Sci. 2022, 44, 570–580. [Google Scholar]
  49. Ali, S.; Hayat, K.; Iqbal, A.; Xie, L.N. Implications of abscisic acid in the drought stress tolerance of plants. Agronomy 2020, 10, 1323. [Google Scholar] [CrossRef]
  50. Mega, R.; Abe, F.; Kim, J.S.; Tsuboi, Y.; Tanaka, K.; Kobayashi, H.; Sakata, Y.; Hanada, K.; Tsujimoto, H.; Kikuchi, J.; et al. Tuning water-use efficiency and drought tolerance in wheat using abscisic acid receptors. Nat. Plants 2019, 5, 153–159. [Google Scholar] [CrossRef] [PubMed]
  51. Shen, J.; Zhang, J.; Zhou, M.; Zhou, H.; Cui, B.; Gotor, C.; Romero, L.C.; Fu, L.; Yang, J.; Foyer, C.H.; et al. Persulfidation-based modification of cysteine desulfhydrase and the NADPH oxidase RBOHD controls guard cell abscisic acid signaling. Plant Cell 2020, 32, 1000–1017. [Google Scholar] [CrossRef]
  52. Chen, Q.; Hu, T.; Li, X.; Song, C.P.; Zhu, J.K.; Chen, L.; Zhao, Y. Phosphorylation of SWEET sucrose transporters regulates plant root:shoot ratio under drought. Nat. Plants 2022, 8, 68–77. [Google Scholar] [CrossRef]
  53. Hu, J.; Cui, S.; Yan, X.; Xu, H.; Huang, X. Effects of exogenous gibberellic acid on physiological characteristics of Hedera nepalensis var. sinensis under drought stress. J. Yunnan Agric. Univ. (Nat. Sci.) 2024, 39, 110–118. [Google Scholar]
  54. Liao, Z.; Zhang, Y.; Yu, Q.; Fang, W.; Chen, M.; Li, T.; Liu, Y.; Liu, Z.; Chen, L.; Yu, S.; et al. Coordination of growth and drought responses by GA-ABA signaling in rice. New Phytol. 2023, 240, 1149–1161. [Google Scholar] [CrossRef] [PubMed]
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Figure 1. Experimental design of the drought–rehydration treatment.
Figure 1. Experimental design of the drought–rehydration treatment.
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Figure 2. Changes in relative soil water content in Camellia oleifera under drought and rehydration treatments. DS, drought-stressed group; RW, rehydrated group. Soil layers represent depths of 0–20 cm, 20–40 cm, and 40–60 cm, respectively.
Figure 2. Changes in relative soil water content in Camellia oleifera under drought and rehydration treatments. DS, drought-stressed group; RW, rehydrated group. Soil layers represent depths of 0–20 cm, 20–40 cm, and 40–60 cm, respectively.
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Figure 3. Stomatal morphology of C. oleifera leaf surfaces.
Figure 3. Stomatal morphology of C. oleifera leaf surfaces.
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Figure 4. Photosynthetic responses of C. oleifera leaves to drought and rewatering. (A) Net photosynthetic rate (Pn). (B) Transpiration rate (Tr). (C) Stomatal conductance (Gs). (D) Intercellular CO2 concentration (Ci). (E) Stomatal limitation value (Ls). (F) Water use efficiency (WUE). Different lowercase letters indicate significant differences within the same treatment across time points (p < 0.05).
Figure 4. Photosynthetic responses of C. oleifera leaves to drought and rewatering. (A) Net photosynthetic rate (Pn). (B) Transpiration rate (Tr). (C) Stomatal conductance (Gs). (D) Intercellular CO2 concentration (Ci). (E) Stomatal limitation value (Ls). (F) Water use efficiency (WUE). Different lowercase letters indicate significant differences within the same treatment across time points (p < 0.05).
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Figure 5. Representative scanning electron microscopy (SEM) images of stomata on C. oleifera leaves after 28 days of drought or rewatering treatment. Images show stomatal morphology at ×2000, ×1000, and ×500 magnifications (left to right).
Figure 5. Representative scanning electron microscopy (SEM) images of stomata on C. oleifera leaves after 28 days of drought or rewatering treatment. Images show stomatal morphology at ×2000, ×1000, and ×500 magnifications (left to right).
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Figure 6. Effects of drought and rewatering on stomatal traits of C. oleifera leaves. (A) Density of open stomata (left) and stomatal opening ratio (right). (B) Unit stomatal area. Different lowercase letters indicate significant differences between treatments (p < 0.05).
Figure 6. Effects of drought and rewatering on stomatal traits of C. oleifera leaves. (A) Density of open stomata (left) and stomatal opening ratio (right). (B) Unit stomatal area. Different lowercase letters indicate significant differences between treatments (p < 0.05).
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Figure 7. Correlation between abscisic acid (ABA) content and photosynthetic parameters in C. oleifera cultivars under drought–rewatering treatment. (A) Net photosynthetic rate (Pn). (B) Transpiration rate (Tr). (C) Stomatal conductance (Gs). (D) Intercellular CO2 concentration (Ci). (E) Stomatal limitation value (Ls). (F) Water use efficiency (WUE).
Figure 7. Correlation between abscisic acid (ABA) content and photosynthetic parameters in C. oleifera cultivars under drought–rewatering treatment. (A) Net photosynthetic rate (Pn). (B) Transpiration rate (Tr). (C) Stomatal conductance (Gs). (D) Intercellular CO2 concentration (Ci). (E) Stomatal limitation value (Ls). (F) Water use efficiency (WUE).
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Table 1. Basic information on the Camellia oleifera test cultivars.
Table 1. Basic information on the Camellia oleifera test cultivars.
VarietyForest Age (a)Average Base Diameter (cm)Average Tree Height (cm)Average Crown Width (cm)
CL5376.2 ± 0.40135.4 ± 11.3162
CL4075.7 ± 0.35172.8 ± 13.5134
Table 2. Effects of drought and rehydration on leaf relative water content in C. oleifera.
Table 2. Effects of drought and rehydration on leaf relative water content in C. oleifera.
TreatmentLeaf Relative Water Content (%)
0 d7 d14 d21 d28 d
DS-5376.61 ± 0.64 ab75.95 ± 1.02 ab77.44 ± 1.11 a74.17 ± 1.80 b71.43 ± 2.26 b
RW-5375.37 ± 1.28 b81.69 ± 1.34 a81.46 ± 0.75 a81.36 ± 1.17 a82.48 ± 0.85 a
DS-4075.54 ± 0.50 a75.86 ± 0.61 a74.08 ± 1.24 ab72.27 ± 2.11 b72.54 ± 1.29 b
RW-4075.21 ± 0.66 d78.34 ± 1.38 c80.19 ± 1.39 bc81.24 ± 1.87 b83.39 ± 1.00 a
In each row, different lowercase letters indicate statistically significant differences at p < 0.05.
Table 3. Stomatal characteristics of different C. oleifera cultivars.
Table 3. Stomatal characteristics of different C. oleifera cultivars.
VarietyStomatal Density (mm−2)Stomatal Apparatus Length (μm)Stomatal Aperture Width (μm)Stomatal Apparatus Area (μm2)
CL53230.37 ± 11.94 b24.25 ± 1.39 a20.19 ± 1.49 a383.97 ± 32.47 a
CL40285.37 ± 12.23 a21.87 ± 1.06 b18.60 ± 1.88 b319.91 ± 40.43 b
Different lowercase letters indicate statistically significant differences at p < 0.05 in each column.
Table 4. Effects of abscisic acid levels in C. oleifera leaves under drought and rehydration conditions.
Table 4. Effects of abscisic acid levels in C. oleifera leaves under drought and rehydration conditions.
TreatmentABA Content/(ng·g−1)
0 d7 d14 d21 d28 d
DS-5326.12 ± 0.73 d27.77 ± 0.52 c29.65 ± 1.21 b29.50 ± 0.49 b32.06 ± 1.01 a
RW-5328.45 ± 0.89 a17.66 ± 0.46 b13.51 ± 0.90 c10.51 ± 0.51 d13.33 ± 0.55 c
DS-4036.51 ± 0.84 d38.65 ± 0.30 c38.04 ± 1.09 c44.36 ± 1.02 b47.70 ± 0.69 a
RW-4031.83 ± 0.36 a17.82 ± 0.72 b16.79 ± 0.73 c10.57 ± 0.58 d9.83 ± 0.17 d
In each row, different lowercase letters indicate statistically significant differences at p < 0.05.
Table 5. Effects of drought and rehydration on gibberellin levels in C. oleifera leaves.
Table 5. Effects of drought and rehydration on gibberellin levels in C. oleifera leaves.
TreatmentGA3 Content/(ng·g−1)
0 d7 d14 d21 d28 d
DS-532.96 ± 0.12 a2.79 ± 0.15 a2.68 ± 0.13 ab2.66 ± 0.13 ab2.42 ± 0.28 b
RW-532.58 ± 0.11 c3.39 ± 0.16 b3.98 ± 0.08 a3.80 ± 0.19 a3.89 ± 0.36 a
DS-406.77 ± 0.31 a6.58 ± 0.30 a6.49 ± 0.24 a6.50 ± 0.29 a5.91 ± 0.34 b
RW-406.42 ± 0.25 b6.45 ± 0.24 b7.15 ± 0.27 a7.43 ± 0.18 a7.51 ± 0.18 a
In each row, different lowercase letters indicate statistically significant differences at p < 0.05.
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Cao, L.; Yan, C.; He, T.; Zhong, Q.; Yuan, Y.; Cao, L. Coordinated Regulation of Photosynthesis, Stomatal Traits, and Hormonal Dynamics in Camellia oleifera During Drought and Rehydration. Biology 2025, 14, 965. https://doi.org/10.3390/biology14080965

AMA Style

Cao L, Yan C, He T, Zhong Q, Yuan Y, Cao L. Coordinated Regulation of Photosynthesis, Stomatal Traits, and Hormonal Dynamics in Camellia oleifera During Drought and Rehydration. Biology. 2025; 14(8):965. https://doi.org/10.3390/biology14080965

Chicago/Turabian Style

Cao, Linqing, Chao Yan, Tieding He, Qiuping Zhong, Yaqi Yuan, and Lixian Cao. 2025. "Coordinated Regulation of Photosynthesis, Stomatal Traits, and Hormonal Dynamics in Camellia oleifera During Drought and Rehydration" Biology 14, no. 8: 965. https://doi.org/10.3390/biology14080965

APA Style

Cao, L., Yan, C., He, T., Zhong, Q., Yuan, Y., & Cao, L. (2025). Coordinated Regulation of Photosynthesis, Stomatal Traits, and Hormonal Dynamics in Camellia oleifera During Drought and Rehydration. Biology, 14(8), 965. https://doi.org/10.3390/biology14080965

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