Interactive Effects of Exogenous Hormones, Sucrose, and Environmental Factors on the Growth of Phyllostachys edulis Shoots

Abstract

The growth of bamboo shoots during the rapid growth phase critically determines overall bamboo height development. While exogenous hormones and sugars promote plant growth, their interactions with environmental factors and regional variations remain unclear. This study examined moso bamboo (Phyllostachys edulis) from Anhui and Hubei provinces using random forest and Bayesian hierarchical models to analyze direct and interactive effects of auxin, gibberellin, sucrose, auxin transport inhibitors, mTOR signaling pathway inhibitors, and environmental factors on shoot height. Results identified mean temperature, minimum temperature, precipitation, and subsurface runoff as key environmental drivers. Regional adaptations were evident: Anhui bamboo showed positive correlations with temperature factors, while Hubei bamboo exhibited negative correlations. Subsurface runoff consistently promoted growth, whereas precipitation negatively impacted development. Gibberellin and auxin treatments significantly enhanced bamboo responsiveness to favorable environmental conditions, while inhibitor treatments reduced these responses. This research elucidates complex interactions among exogenous hormones, sugars, and environmental factors affecting bamboo shoot growth. The findings reveal distinct regional adaptation patterns and demonstrate how hormone treatments can modulate environmental responsiveness. These insights provide theoretical foundations and practical guidance for optimizing regional bamboo forest management strategies and improving yield outcomes.

1. Introduction

Bamboo represents a diverse group of monocotyledonous perennial plants belonging to the subfamily Bambusoideae within the Poaceae family, characterized by a unique semelparous reproductive strategy. Based on culm characteristics and flowering patterns, bamboos are classified into woody and herbaceous types, constituting one of the world’s most important forest resources. China possesses the world’s most abundant bamboo resources, with forest coverage spanning 64,116 square kilometers [1], and serves as the largest global producer, consumer, and exporter of bamboo products. In 2020, China’s bamboo product import and export trade totaled USD 2.21 billion [2]. The economic value of bamboo is directly correlated with culm height, making the height growth of moso bamboo (Phyllostachys edulis) a consistently important research focus [3,4,5].

Auxin represents one of the most crucial endogenous hormones in plants, extensively participating in growth and developmental processes, including cell division, elongation, and differentiation. Auxin plays a pivotal role in phototropism, gravitropism, and organ development, exerting significant influence on plant height and morphogenesis. During bamboo growth, auxin is recognized as a key regulator of internode elongation and culm height increase. Research demonstrates that auxin concentrations during bamboo’s rapid growth phase are closely associated with internode elongation [6]. Beyond auxin, gibberellin represents another critical hormone affecting plant growth. Gibberellin was initially discovered from the rice pathogenic fungus Gibberella fujikuroi; it is naturally produced within plants as an endogenous regulator, a finding that catalyzed the first Green Revolution. Gibberellin exhibits diverse roles in plant development, including seed germination and flower and fruit formation and development [7,8]. Notably, gibberellin’s most pronounced effect occurs during the growth phase, where it regulates stem length and internode elongation through induced cell division and elongation, as confirmed in Arabidopsis thaliana, rice (Oryza sativa), maize (Zea mays), elephant grass (Pennisetum purpureum), and alfalfa (Medicago sativa) [9,10,11,12]. In agriculture, gibberellin is commonly employed to regulate plant height for improving crop yield and lodging resistance. Conversely, bamboo requires greater plant height to enhance economic and ecological value. Currently, research on gibberellin’s effects on bamboo growth remains limited. Studies on moso bamboo seedlings have revealed that gibberellin-treated seedlings exhibit longer internodes and greater plant height [13], with faster growth rates and longer internode cells compared to controls [14].

Carbohydrates serve not only as primary photosynthetic products but also as the principal form of carbohydrate storage in many higher plants. Sucrose plays a vital role in bamboo’s rapid growth. Starch and soluble sugar catabolism significantly increases in moso bamboo spring shoots [15]. Bamboo sheaths utilize water as a medium to transport organic acids, sugars, and other compounds to internodes, promoting bamboo shoot growth [16]. Research on Fargesia yunnanensis demonstrates that starch content in buds is insufficient to meet bamboo shoot consumption during rapid growth phases, necessitating additional carbohydrate acquisition from parent culms [17]. Before the conclusion of rapid growth phases in F. yunnanensis, sucrose becomes undetectable, with transported sucrose to internodes being completely hydrolyzed, suggesting that energy in bamboo shoots may be insufficient to fully support rapid internode elongation.

In natural environments, bamboo shoot growth is regulated not only by hormones and carbohydrates but also influenced by environmental factors such as temperature, precipitation, and light availability. Despite extensive research on bamboo shoot nutritional composition [18,19], the mechanisms by which hormones, carbohydrates, and environmental factors collectively influence rapid bamboo shoot growth in field conditions, and whether complex interactive effects exist, remain insufficiently understood. This study selected wild moso bamboo shoots from Guangde City, Anhui Province, and Xianning City, Hubei Province, implementing treatments with exogenous auxin (IAA), auxin transport inhibitor (TIBA), sucrose (SUC), mTOR signaling pathway inhibitor (AZD, used to modulate cellular energy metabolism affecting sucrose utilization), and gibberellin (GA) while measuring height changes across different growth periods. Simultaneously, using random forest models and Bayesian hierarchical models, we systematically analyzed the effects of ten key environmental factors, including temperature, air humidity, net solar radiation, and runoff, on bamboo shoot growth during the rapid growth phase (March to May), as well as interactive effects between environmental factors and hormones and carbohydrates on bamboo shoot growth regulation mechanisms. This study aims to elucidate the synergistic mechanisms by which exogenous hormones and environmental factors influence rapid bamboo shoot growth, providing theoretical foundations for scientific bamboo forest cultivation and management.

2. Materials and Methods

2.1. Study Area

All experimental subjects in this study were selected from pure P. edulis forests in southern China (Figure 1). Experimental sites were located in Guangde City, Anhui Province (30°47′56.4″ N, 119°23′2.4″ E) and Xianning City, Hubei Province (29°48′54″ N, 114°18′46.8″ E). Soils in the survey areas are primarily yellow soils, with annual average temperatures of 15.6–19.5 °C and annual total precipitation of 1436.6–1876.2 mm, representing major domestic distribution areas for moso bamboo.

2.2. Field Experiments

At each experimental site, we randomly selected and marked 300 bamboo shoots with heights of approximately 50 cm and measured their basal diameters (12.82 ± 2.07 cm), ensuring similar initial sizes across all experimental units. In late March 2021, we began applying experimental treatments to these shoots. Prior to the formal experiment, we conducted preliminary tests using concentration gradients ranging from 5 μM to 100 μM to determine optimal working concentrations. Based on these preliminary results, 20 μM was selected as the standardized concentration for all treatments, as it produced measurable physiological responses without causing adverse growth inhibition effects across all tested compounds. The standardized concentration approach facilitated direct comparison of different regulatory pathways’ effects on bamboo shoot development while ensuring experimental consistency across multiple field sites. Shoots were randomly divided into six groups of 60 individuals each. Injections were administered at the middle portion (fifth internode from the base).

The treatment groups were as follows: Auxin (IAA) treatment group: 60 shoots injected with 50 mL of 20 μM auxin solution (Shanghai Yuanye Biotechnology Co., Ltd., Shanghai, China, Product No. S18031; https://www.shyuanye.com/search.php?encode=YToyOntzOjg6ImtleXdvcmRzIjtzOjY6IlMx-ODAzMSI7czoxODoic2VhcmNoX2VuY29kZV90aW1lIjtpOjE3NTUyMjc1ODY7fQ==, accessed on 10 May 2025).

Auxin transport inhibitor (TIBA) treatment group: Same method and sample size with 20 μM auxin transport inhibitor solution (Product No. B65101; https://www.shyuanye.com/search.php?encode=YToyOntzOjg6ImtleXdvcmRzIjtzOjY6IkI2NTEwMSI7czoxODoic2VhcmNoX2VuY29kZV90aW1lIjtpOjE3NTUyMjc3ODE7fQ==, accessed on 10 May 2025). This compound specifically blocks polar auxin transport to examine auxin-independent growth responses.

Sucrose (SUC) treatment group: Same method and sample size with 20 μM sucrose solution (Product No. S11055; https://www.shyuanye.com/search.php?encode=YToyOntzOjg6ImtleXdvcmRzIjtzOjY6IlMxM-TA1NSI7czoxODoic2VhcmNoX2VuY29kZV90aW1lIjtpOjE3NTUyMjc2OTU7fQ==, accessed on 10 May 2025).

mTOR signaling pathway inhibitor (AZD) treatment group: Same method and sample size with 20 μM mTOR signaling pathway inhibitor solution (Product No. S80013; https://www.shyuanye.com/search.php?encode=YToyOntzOjg6ImtleXdvcmRzIjtzOjY6IlM4MDAxMyI7czoxODoic2VhcmNoX2VuY29kZV90aW1lIjtpOjE3NTUyMjc3MTc7fQ==, accessed on 10 May 2025). This mTOR kinase inhibitor modulates cellular energy metabolism and affects sucrose utilization pathways.

Gibberellin (GA) treatment group: Same method and sample size with 20 μM gibbeellin solution (Product No. S28506; https://www.shyuanye.com/search.php?encode=YToyOntzOjg6ImtleXdvcmRzIjtzOjY6IlMyODU-wNiI7czoxODoic2VhcmNoX2VuY29kZV90aW1lIjtpOjE3NTUyMjc3NzI7fQ==, accessed on 10 May 2025).

Control group: Same method and sample size with 50 mL pure water.

Injections were administered using commercially available medical syringes from 29 March to 15 April 2021, at approximately three-day intervals for five total applications at each study site. When bamboo shoots reached approximately 50 cm in height at the commencement of treatments, injections were positioned at approximately 25–30 cm above ground level. This injection height was selected because the basal portion of shoots was too rigid for effective penetration, while the apical portion remained too tender and vulnerable for injection procedures. Subsequent injections were administered at approximately the same height range on each shoot, though not at precisely identical positions, as shoots continued their rapid vertical growth throughout the treatment period. External solution application typically involves foliar spraying. However, bamboo shoots during the shoot stage grow rapidly and reach heights unsuitable for manual spraying within short periods. Therefore, we did not employ spraying for exogenous treatments.

During bamboo shoot growth periods, we conducted multiple height measurements using a TruPulse 200X laser rangefinder (Laser Technology Inc., Centennial, CO, USA). This device operates based on trigonometric principles, measuring slope distance and inclination to calculate actual bamboo shoot height with an accuracy of ±4 cm. Measurements were taken from a minimum distance of 15 m from each shoot, with operators first targeting the shoot base and then the apex, allowing the device to automatically calculate and display height data. The measurements were conducted across sites on the following dates: Guangde City: 7, 11, 12, and 15 April; Xianning City: 29, 31 March, 3, and 6 April. Due to different emergence periods at different locations, measurement timing differed between regions.

2.3. Data Analysis

We performed one-way analysis of variance (ANOVA) on bamboo shoot heights across different dates and locations, using Tukey HSD post-hoc tests to compare significant differences between treatment groups. Environmental factor data for ten variables were obtained from the European Centre for Medium-Range Weather Forecasts ERA5 reanalysis dataset [20]. We calculated correlation coefficients and significance levels between bamboo shoot height and environmental factors, generating correlation heatmaps for different treatment groups.

Multicollinearity issues were reduced by removing variables with high Variance Inflation Factor (VIF) values, ultimately retaining four environmental factors as independent variables with bamboo shoot height as the dependent variable to establish random forest models [21]. Mean squared error increase percentages were calculated as variable importance indicators.

We employed Bayesian Markov Chain Monte Carlo (MCMC) generalized linear mixed models (GLMM) to analyze relationships between variables. Bayesian modeling methods offer numerous advantages, including flexible distribution family specification based on data characteristics and effective data fitting even under small sample conditions [22,23]. Consequently, Bayesian methods are widely applied across multiple disciplines [24,25]. We employed Bayesian hierarchical linear regression models to investigate effects of exogenous treatment methods (auxin treatment, auxin inhibitor treatment, sucrose treatment, sucrose inhibitor treatment, gibberellin treatment) and environmental factors (mean temperature, minimum temperature, subsurface runoff, precipitation) on bamboo shoot height. Models included interaction terms between exogenous treatment methods and environmental factors. To mitigate potential individual differences affecting bamboo shoot height, we incorporated each shoot’s basal diameter as a random effect. For each model, we established four independent chains with intervals of 1, obtaining 5000 posterior samples from each chain after 5000 iterations. All model prior distributions employed default settings from the brms software package version 2.17.0 [26]. We assumed statistical significance when 95% credible intervals for variables excluded zero. R-hat values were calculated for all parameters, verifying values below 1.01. All data analysis and visualization were completed using R 4.2.0 [27].

3. Results

3.1. Effects of Different Exogenous Treatments on Bamboo Shoot Height

Figure 2 demonstrates the effects of different treatments on moso bamboo shoot height changes during rapid growth phases. In both the Anhui and Hubei regions, most bamboo shoots showed significant height increases over time, with some individuals growing from initial heights of approximately 50 cm to over 300 cm. In Anhui, IAA treatment groups exhibited significantly greater bamboo shoot heights than controls at all measurement timepoints. AZD treatment groups similarly showed significant height enhancement after one week of application. Other treatment groups did not achieve significant effects on bamboo shoot height. In Hubei, auxin and gibberellin treatment groups demonstrated significantly superior bamboo shoot heights compared to controls at all measurement timepoints. Additionally, SUC treatment significantly promoted bamboo shoot height increases after 4 days. In contrast, TIBA treatment resulted in significantly lower bamboo shoot heights than controls after one week, demonstrating clear inhibitory effects. These results reveal that hormone and nutritional treatments affect bamboo shoot growth differently between regions, prompting comparison of environmental factors between regions.

3.2. Environmental Factor Variation Trends During Bamboo Shoot Rapid Growth Periods

Figure 3 displays temporal variation trends of environmental factors during bamboo shoot rapid growth periods in both regions. Mean temperature, minimum temperature, maximum temperature, and surface temperature in both locations showed clear seasonal increasing trends, with similar overall temperature curve patterns and comparable temperature levels. Multiple precipitation events occurred in both regions, with Anhui experiencing concentrated rainfall with higher peaks reaching approximately 55 mm maximum, while Hubei showed relatively dispersed rainfall with lower peaks. Air humidity remained high with large fluctuations in both regions, showing synchronized overall trends, though Anhui air humidity was slightly lower than Hubei. Surface evaporation maintained negative values in both regions, indicating substantial evaporation. Surface runoff and subsurface runoff in Hubei exhibited higher volatility, particularly subsurface runoff peaking in mid-April, while Anhui subsurface runoff remained relatively stable with lower flow rates. Surface net radiation showed clear fluctuations with similar variation trends between regions.

Overall, Anhui and Hubei showed essentially consistent temperature changes but differed in rainfall and hydrological runoff patterns. Anhui experienced more concentrated and intense rainfall with relatively lower and stable subsurface runoff, while Hubei had more dispersed rainfall with notably higher and more volatile subsurface runoff. These environmental factor differences provided distinct conditions for bamboo shoot growth environments in both regions, potentially affecting growth dynamics and responses to exogenous hormones and nutrients.

3.3. Correlations Between Bamboo Shoot Height and Environmental Factors Under Different Treatments and Variable Selection

Figure 4 presents Pearson correlation coefficients between moso bamboo shoot height and multiple environmental factors under different exogenous treatment conditions in Anhui and Hubei. Results indicate significant differences in correlations between bamboo shoot height and temperature factors (including mean temperature, minimum temperature, maximum temperature, and surface temperature) between regions. Bamboo shoot height in Anhui showed significant positive correlations with temperature factors, indicating that temperature increases favor shoot growth; conversely, Hubei exhibited significant negative correlations, suggesting opposite directional effects of temperature on shoot height between regions.

Precipitation showed significant negative correlations with bamboo shoot height in both Anhui and Hubei, suggesting that increased precipitation inhibits bamboo shoot growth. Air humidity correlations with bamboo shoot height were insignificant in both regions with correlation coefficients near zero, indicating minimal air humidity effects on shoot height. Surface evaporation showed significant negative correlations with bamboo shoot height in Anhui but significant positive correlations in Hubei, reflecting regional differences in water evapotranspiration process effects on bamboo shoot growth. Surface runoff exhibited negative correlations with bamboo shoot height, while subsurface runoff showed positive correlations, patterns consistent across both regions, emphasizing the important supportive role of subsurface runoff as a water source for bamboo shoot growth. Additionally, surface net radiation showed significant positive correlations with bamboo shoot height in Anhui but significant negative correlations in Hubei. These correlation analysis results reveal significant regional differences in moso bamboo shoot responses to environmental factors between Anhui and Hubei.

To further investigate regional differences in environmental factor effects on moso bamboo shoot growth under different treatments, we first screened potential key environmental factors by calculating VIF and removing high-VIF environmental factors to reduce inter-variable collinearity. Simultaneously, variable importance was calculated based on random forest models (Figure 5). Four environmental factors—minimum temperature, mean temperature, subsurface runoff, and precipitation—were selected for subsequent analysis.

3.4. Interactive Effects of Treatment Methods and Environmental Factors on Bamboo Shoot Height

Figure 6 results demonstrate significant differences in moso bamboo shoot height responses to environmental factors between Anhui and Hubei, with minimum temperature and mean temperature showing opposite trends between regions. In Anhui, higher minimum and mean temperatures positively promoted shoot height increases, while Hubei exhibited negative correlations where temperature increases actually reduced shoot height. Fitting curves for Anhui experimental shoots, whether controls or various exogenous treatments, showed upward trends with increasing minimum or mean temperature; conversely, Hubei experimental shoot fitting curves showed downward trends with increasing temperature.

Regarding water factors, bamboo shoot response trends were consistent between regions: increased subsurface runoff significantly enhanced shoot height, while increased precipitation significantly reduced shoot height. Figure 6 shows shoot height increases synchronously with subsurface runoff increases and decreases with precipitation increases, trends unchanged by region. Different colored fitting curves represent different hormone or nutritional treatments.

Table 1. Interactive effects of exogenous treatments and environmental factors on bamboo shoot height.

Model Structure	Anhui				Hubei
	Estimate	Estimate Error	l-95% CI	u-95% CI	Estimate	Estimate Error	l-95% CI	u-95% CI
Minimum temperature × IAA	1.87	2.19	−2.43	6.18	−0.97	1.72	−4.36	2.42
Minimum temperature × TIBA	1.23	2.46	−3.55	6.06	2.39	1.76	−1.09	5.83
Minimum temperature × SUC	1.09	2.18	−3.18	5.40	−1.37	1.63	−4.47	1.81
Minimum temperature × AZD	1.18	2.46	−3.66	5.97	−0.99	1.72	−4.37	2.41
Minimum temperature × GA	−1.16	2.14	−5.32	3.03	−3.26	1.93	−7.09	0.53
Average temperature × IAA	4.53	2.10	0.46	8.68	−0.63	1.05	−2.67	1.43
Average temperature × TIBA	3.45	2.35	−1.18	7.99	1.60	1.07	−0.47	3.66
Average temperature × SUC	5.00	2.39	0.30	9.65	−0.88	0.98	−2.82	1.04
Average temperature × AZD	3.48	2.12	−0.64	7.68	−0.61	1.06	−2.70	1.45
Average temperature × GA	0.24	2.11	−3.89	4.38	−2.10	1.15	−4.35	0.13
Subsurface runoff × IAA	3.30	3.95	−4.28	11.11	3.08	2.40	−1.64	7.83
Subsurface runoff × TIBA	2.57	4.46	−6.31	11.38	−10.35	2.50	−15.19	−5.35
Subsurface runoff × SUC	2.34	4.02	−5.49	10.12	4.22	2.28	−0.24	8.81
Subsurface runoff × AZD	2.85	4.56	−6.00	11.56	2.56	2.43	−2.18	7.36
Subsurface runoff × GA	−1.30	3.97	−9.19	6.51	11.15	2.71	5.97	16.47
Precipitation × IAA	−0.82	0.57	−1.93	0.29	−1.16	1.61	−4.29	2.03
Precipitation × TIBA	−0.60	0.64	−1.86	0.68	2.75	1.65	−0.50	5.96
Precipitation × SUC	−0.62	0.57	−1.74	0.50	−1.57	1.53	−4.54	1.45
Precipitation × AZD	−1.10	0.64	−2.34	0.15	−1.08	1.64	−4.25	2.07
Precipitation × GA	−0.45	0.56	−1.58	0.64	−3.63	1.80	−7.16	−0.15

Treatment abbreviations: IAA = Auxin treatment, TIBA = Auxin transport inhibitor treatment, SUC = Sucrose treatment, AZD = mTOR signaling pathway inhibitor treatment, GA = Gibberellin treatment. Statistical significance is indicated when the confidence interval does not include zero.

displays interactive effects of exogenous treatments and environmental factors on bamboo shoot height. Different regression line slopes (estimate) under various treatments indicate varying response intensities, with some results achieving statistical significance, demonstrating that different exogenous treatments modulate bamboo shoot response strength to environmental factor changes.

4. Discussion

This study analyzed the effects of exogenous sucrose, auxin, and gibberellin hormones and their inhibitors on bamboo shoot height growth during rapid growth phases, incorporating key environmental factors including temperature, precipitation, and subsurface runoff to preliminarily elucidate regional environmental responses and complex interactions with hormones and carbohydrates in bamboo shoot growth. Our findings reveal that bamboo shoot height exhibits significant regional differential responses to temperature factors, reflecting response strategies of moso bamboo shoot height growth to temperature thresholds. Simultaneously, a stable water supply from subsurface runoff universally promotes bamboo shoot growth, while excessive precipitation inhibits growth. Hormone and carbohydrate exogenous treatments not only significantly enhance bamboo shoot growth rates but also modulate plant sensitivity to environmental factors, strengthening bamboo shoot utilization of favorable environmental conditions.

4.1. Environmental Factors Governing Bamboo Shoot Growth

Temperature, as a core environmental variable for plant growth, reflects the complexity of moso bamboo adaptation to regional climates through its effects on bamboo shoot height. In Anhui, increases in mean and minimum temperatures showed significant positive correlations with bamboo shoot growth, suggesting that shoots in this region may operate within optimal temperature ranges. Temperature elevation can accelerate cell cycles, promote microtubule and cell wall reorganization, and enhance cell elongation rates [28]. However, temperature effects on bamboo shoot growth in Hubei experimental areas exhibited significant negative correlations. Mean temperatures in Hubei experimental areas were approximately 5 °C higher than in Anhui, potentially approaching or exceeding optimal ranges for moso bamboo shoot rapid growth phases. Moreover, higher temperatures may accelerate soil moisture evaporation and plant transpiration, causing rapid soil moisture loss and indirectly inducing drought stress [29], further inhibiting bamboo shoot growth. These temperature threshold effects and complex environment-physiology interactions fully demonstrate differential adaptation strategies of moso bamboo under varying climatic conditions, emphasizing potential regulatory roles of local microclimates on bamboo shoot growth.

Water availability represents one of the key limiting factors for rapid bamboo shoot growth. Our study found that subsurface runoff volume showed significant positive correlations with bamboo shoot height, exhibiting consistent promotional effects in both regions. Subsurface runoff, as an important soil moisture supplement, provides stable and continuous water sources, ensuring turgor pressure maintenance and nutrient transport, thereby supporting cell wall elongation and division [30]. This finding aligns with previous research, demonstrating high dependency of bamboo shoot growth periods on soil moisture [31]. Additionally, subsurface runoff regulates soil temperature and humidity through reducing extreme environmental fluctuation impacts, providing more stable ecological environments for bamboo shoot growth [32]. Conversely, precipitation exerted negative effects on bamboo shoot height, suggesting that excessive rainfall may reduce oxygen diffusion in soil, inhibiting root respiration and nutrient uptake [33,34]. Furthermore, excessive precipitation may exacerbate soil nutrient loss, reducing soil fertility and affecting bamboo shoot growth environment stability [35,36,37]. Rainfall typically accompanies overcast conditions, leading to decreased light intensity and duration. Research indicates that bamboo sheaths possess certain photosynthetic capabilities, providing auxiliary carbon sources for rapidly elongating bamboo shoots [38]. Therefore, under conditions of adequate available water resources, heavy rainfall may actually negatively impact bamboo shoot growth, serving as a negative regulatory factor limiting rapid growth.

The contrasting environmental factor correlations (Figure 4) between regions can be explained through thermal performance curve theory, where plant growth peaks at optimal temperatures and declines on either side [39]. This framework clarifies why identical temperature changes produce opposite growth responses between our study sites. Similarly, the reversed evaporation patterns reflect different thermoregulatory strategies. In cooler Anhui conditions, evaporation primarily represents water loss stress. However, in warmer Hubei environments where temperatures may exceed optimal ranges, evapotranspiration provides essential cooling benefits that can reduce tissue temperatures by several degrees, helping maintain physiological functions under heat stress [40]. The positive correlation between evaporation and growth in Hubei suggests bamboo shoots actively utilize transpirational cooling to mitigate temperature stress when operating beyond their thermal optimum. These regional differences highlight how identical environmental changes can trigger contrasting physiological responses depending on baseline climatic conditions.

4.2. Exogenous Growth Regulators and Their Effects on Shoot Development

Auxin polar transport regulates cell polar growth, playing crucial roles in plant growth and tissue construction [41,42], while gibberellin promotes cell wall plasticity changes through regulating cell wall loosening enzyme expression, achieving rapid internode elongation [43,44]. Carbohydrates, as important carbon compounds, provide essential energy for cell growth and metabolism. In this study, exogenous addition of auxin, gibberellin, and sucrose all promoted bamboo shoot height growth to varying degrees; however, auxin inhibitors significantly reduced bamboo shoot height only in Hubei experimental areas, while sucrose inhibitors showed no significant negative effects on bamboo shoot height growth. The dosages of exogenous auxin inhibitors we applied may have been insufficient to counteract endogenous auxin effects in bamboo. Simultaneously, the growth of bamboo shoots during rapid growth phases depends not only on self-synthesized carbohydrates but more extensively on photosynthetic product supply from parent culms through physiological integration. The continuous carbohydrate influx from parent culms provides substantial metabolic resources that support sustained growth. This external carbohydrate supply through physiological integration masks the potential growth-limiting effects of hormone and carbohydrate inhibitors, explaining why these treatments did not significantly impede bamboo shoot growth.

4.3. Interactive Mechanisms and Implications for Bamboo Forest Management

This study preliminarily reveals complex interactive regulatory mechanisms between environmental factors and exogenous hormone and carbohydrate treatments on moso bamboo shoot height growth. Results indicate that single environmental factors or single hormone treatments cannot comprehensively explain bamboo shoot growth dynamics, while their interactions significantly affect bamboo shoot response sensitivity to temperature, moisture, and other environmental changes. Gibberellin and auxin treatments significantly enhanced bamboo shoot utilization of favorable temperature and subsurface runoff conditions. In contrast, TIBA treatment inhibiting auxin polar transport and sucrose inhibitor treatment significantly weakened these responses, suggesting that effective transport and utilization of endogenous hormones and carbohydrates may represent key elements enabling bamboo shoots to adapt to different environments and complete rapid growth.

These interactive mechanisms reflect plant capabilities to integrate external environmental signals through internal physiological regulation during rapid growth stages, representing typical strategies for plant adaptation to complex and variable environments [45]. In natural ecosystems, environmental factors often change simultaneously, with single hormone or nutrient effects limited by external conditions [46,47], while environmental condition fluctuations affect growth performance through influencing hormone synthesis, transport, and signaling pathways [48,49]. This study provides new insights for understanding environment physiology coupling mechanisms in bamboo shoot growth, not only helping to elucidate bamboo shoot growth adaptability under different regional environments but also providing theoretical foundations for optimizing bamboo forest production through regulating exogenous hormone and nutritional management strategies.

The regional differences observed in temperature responses suggest that moso bamboo populations may have undergone local adaptation to their respective climatic conditions [50]. The positive temperature response in Anhui and negative response in Hubei likely reflect different positions along the species’ thermal tolerance curve, with implications for bamboo forest management under climate change scenarios. Future research should investigate the molecular mechanisms underlying these regional differences, particularly the role of heat shock proteins [51], antioxidant systems [52], and metabolic adjustments in determining temperature response thresholds [53].

The consistent positive effects of subsurface runoff across regions highlight the importance of soil hydrology in bamboo forest ecosystems. This finding has practical implications for silvicultural practices, suggesting that maintaining soil permeability and sustainable water table levels may be more critical for bamboo productivity than increasing surface water availability. The negative effects of precipitation may be mediated through complex interactions involving soil aeration, pathogen pressure, and nutrient leaching, warranting further investigation.

5. Conclusions

The differential responses to hormone treatments between regions suggest that endogenous hormone homeostasis may vary with environmental conditions. This has important implications for developing region-specific management practices and understanding how bamboo forests may respond to changing environmental conditions. Future studies should examine endogenous hormone profiles across different environmental gradients to better understand these interactions.