Benefits of selenium foliar application on morphological, flowering and biochemical attributes of chrysanthemum upon water-deficit stress

Abstract

Background

Selenium (Se) acts as a vital stress ameliorant, significantly mitigating the negative impacts of environmental stressors. Chrysanthemum, a globally renowned flowering and landscaping plant, experiences substantial declines in growth and yield under water-deficit conditions. Consequently, this study was performed to evaluate the efficacy of foliar selenium application in alleviating the adverse effects of drought on the growth, flowering, and biochemical profiles of Dendranthema grandiflora (cv. ‘Poornima White’). The research followed a split-plot design within a Randomized Complete Block Design (RCBD) with three replicates. Main plots consisted of three soil water capacity (SWC) levels (100%, 80%, and 60%), while sub-plots received four selenium concentrations (Se₀, Se₁₀₀, Se₁₅₀, and Se₂₀₀). The experiment was conducted at a private nursery in Damanhour, Beheira Governorate, Egypt, during the 2024 and 2025 growing seasons.

Methods

The changes in biometric characteristics including plant height, plant fresh weight and plant dry weight under water-deficit stress with exogenous Se application were characterized at the bud initiation stage. Additionally, the flowering and yield traits such as time to flowering, length of stalk, diameter of flower, flower weight and number of inflorescences per plant were recorded at the flowering stage. Also, biochemical constituents e.g., chlorophyll a, chlorophyll b, carotenoids, proline, GA₃, ABA as well as contents of N, P and K were determined.

Results

Results indicated that water-deficit stress showed a notable decrease in various biometric, flowering and biochemical characteristics in chrysanthemum plants, and the deficiency was evident with the lowest SWC level (60%). Exogenous Se application as foliar spraying, especially at 200 mg/l markedly enhanced notably growth, flowering and biochemical traits in stressed or well-watered plants.

Conclusions

Selenium (Se) supplementation exerts useful properties on drought-induced detrimental impacts in chrysanthemum plants, which improves various growth, flowering related traits and biochemical in stressed or well-watered plants, and the improvement was consistent with increasing selenium concentration from 100 mg/l Se up to 200 mg/l.

Introduction

Ornamental plants are horticultural merchandise in high desire because they have diverse colors and shapes. It contributes to decorating and beautifying the environment. Ornamental plants also contribute to satisfying mental needs and decorating the indoor space [1, 2]. Chrysanthemum plant (Dendranthema grandiflora Tzvelve.) cv.” Poornima white” is one of the most important flower species in Asteraceae family and runs significant value for its different forms, multiple colors and long vase life [3]. It ranks the second position among the ten most important cut flowers after roses [4]. Chrysanthemum flowers have a high economic value in different countries as they represent a major share in the export market. Irrigation is a vital practice for Chrysanthemum growing, but its sufficient handling has been disregarded by growers, leads to decreased productivity and poor quality of the final product [5]. Water represents about 80–95% of the plant fresh weight, because of its various physiological roles including many aspects of metabolism, plant growth and development [6, 7]. The amounts and intervals of irrigation for chrysanthemum have a great impact on flower characteristics such as flower stem length, diameter and weight, flowers number, vase life and root length [8]. On the other hand, drought stresses reduce plant biomass, leading to changes in the biochemical and physiological processes in plants, which affects the growth and productivity [9]. Abscisic acid (ABA) signaling plays a vital role in root systems, it has various functions such as preserving the elongation of the primary root and suppressing lateral root formation under conditions of water scarcity [10]. The longest stem and heaviest plant fresh weight with more flowers were achieved on chrysanthemum irrigated four times weekly when compared with those irrigated twice weekly [11]. The results of [12] indicated that maintained chrysanthemum plants under 100% FC showed a greater of flowers number compared with plants cultivated under 70% FC. They pointed out that chrysanthemum plant performed better at a higher moisture level than 70% FC. Therefore, improving chrysanthemum tolerance to water-deficit stress has become essential for enhancing of the growth, flowering and quality of valuable flowering plants.

Selenium (Se) belongs to the oxygen group in periodic table and a non-metallic element. Various studies have indicated that selenium is not an essential element for plants but can be taken up and metabolized by plants. It enhances photosynthetic pigments in plants [13] and exhibits antioxidant activities [14]. The findings of [15] showed that Se spraying promoted the accumulation of above-ground dry biomass and improved photosynthetic pigment over control treatment. They added that Se application improved the activity and contents of protective enzymes and osmolytes. Plants being exposed to water deficit causes damage to their biomolecules such as proteins, lipids, carbohydrates, and nucleic acids; and therefore, declining the respiration, photosynthesis and plant growth [16]. Exogenous Se supplementation on soybean boosted the contents of protective enzymes, improved stomatal conductance and cell ultrastructure of mesophyll, and mitigated the adverse impacts of drought stress [15] . Adding selenium improves the compatible solutes in drought-affected plants, thus decreasing the oxidative stresses in plants. When these osmolytes accumulate, the cellular dehydration is reduced in plants [17]. Senescence is induced in plants as a result of the protection of oxidative stress, which contributes producing the ROS enzymes with the addition of selenium to the plant [18, 19]. The application of selenium induces the synthesis and production of proline and peroxidase through antioxidant action. Also, its addition can reduce the degradability of membrane and increase enzymes activity [20]. Moreover, selenium application can improve plant growth, decrease damage of oxidative stresses, induce the oxidative stresses and regulate the water balance in plants to alleviate drought stresses [21]. Selenium exhibits beneficial properties in Gentiana macrophylla plants under drought stress by improving photosynthesis indexes and inducing growth of drought-stressed plants [22]. Application of selenium as nanoparticles on Echinacea purpurea plants produced higher pigments and enzymes under drought stresses and mitigated the adverse effect of drought stresses as well as improved productivity and growth characteristics [23]. Although, many previous studies have shown that insufficient irrigation of chrysanthemum reduces plant productivity and quality [5–26], the extent to which these negative effects can be mitigated by using selenium may be negligible. Therefore, the present investigation aimed to evaluate the effect of selenium as foliar application on the morphological, physiological, and biochemical traits of chrysanthemum cv.” Poornima white” grown under drought stress.

Materials and methods

Experimental site and plant material

The experiment was conducted under poly house in a private nursery in Damanhour, Beheira Governorate, Egypt, throughout the two growing seasons of 2024 and 2025 (Longitude 30.28º, 5.63” E, latitude 31.02º 2.69” N) to evaluate the influence of supplementation selenium (Se) on the growth, flowering and physiological characteristics of Chrysanthemum (Dendranthema grandiflora Tzvelve.) cv.” Poornima white” under different irrigation regimes. The average temperature, rainfall, daylight and relative humidity of the two seasons, from Meteorological station of Damanhour, Egypt as shown in Table 1. Two months old plants of chrysanthemum cv. ‘Purnima’ individually grown in 30 cm diameter PVC pots of 5 kg soil capacity filled with a clay loam soil as a medium in 20th June for the two studied seasons. The physical and chemical characteristics of the clay loam soil were analyzed at the Soil and Water Research Institute, Agricultural Research Center, Egypt as shown in Table 2. The transplants of the tested cultivar were obtained from a commercial nursery in Al-Qanater El-Khayreya area of Cairo, Egypt. For plant nutrition, a chemical fertilization was added as spraying on foliage with 20:20:20 (NPK) fertilizer, at rate of 1.5 g/l as three equal applications at one-month interval from the beginning of experiment [27]. The chemical fertilizer NPK was obtained from Ismaelia Company for Chemicals Products, Egypt. The PVC pots were watered regularly for two weeks, then the plants were treated with different experimental treatments in 5th July, including Se applications and irrigation regime levels. Thirty days after planting, the plants were pinched by removing the growing tip to encourage the growth of lateral shoots. The weeds were removed manually from time to time to keep the pots weed-free.

Table 1.

Average temperature, rainfall, daylight and relative humidity of Damanhour, Beheira Governorate, Egypt as average of 2024 and 2025 (Meteorological station in Damanhour, Egypt)

Month	Average temperature (°C)	Rainfall (mm)	Daylight (hours)	Relative humidity (%)
January	13.30	25.5	10.0	73.8
February	13.75	21.3	11.0	72.5
March	15.90	9.4	12.0	71.7
April	19.30	4.5	13.0	71.3
May	22.90	3.4	13.0	72.5
June	25.20	0.0	14.0	74.4
July	26.40	0.0	13.0	74.9
August	26.70	0.0	13.0	72.3
September	25.40	0.0	12.0	70.8
October	23.15	5.4	11.0	71.5
November	19.50	13.3	10.0	72.6
December	15.30	22.5	10.0	72.4

Table 2.

The physical and chemical analysis of the used soil, as average of two seasons

Character	Value	Character	Value
Particle size distribution
Sand %	21.70	OM %	1.50
Silt %	26.00	CaCO3%	2.00
Clay %	52.30	Total N %	0.15
Texture	Clay loam	Available P (mg kg− 1)	6.00
pH (1:2.5 extract)	7.70	Available K (mg kg− 1)	180.0
EC (1:2.5 extract) dSm− 1	0.40	Available S (mg kg− 1)	3.20
Available EDTA extractable micronutrients (mg kg− 1)
Zn	11.00	Mn	11.00
Fe	9.00	Cu	1.00

Experimental design and treatments

The applied treatments of this experiment were followed the completely randomized block design (RCBD) in a split-plot arrangement with three replications; each experimental unit contains three pots totaling 108 PVC pots. The main plots including the irrigation regime levels of the soil water capacities (SWC) i.e. 100, 80 and 60%; to achieve these levels, the transplants were irrigated every three days at a rate of 300, 240 and 180 ml/pot, respectively. Irrigation is done using tap water from water tank. Meanwhile, the sub-plots containing four concentrations of selenium (Se) as spraying i.e. 0 = Se₀, 100 mg Se/l = Se₁₀₀, 150 mg/l Se = Se₁₅₀ and 200 mg/l Se=Se₂₀₀. The used selenium (Se) was as sodium selenate (Na₂SeO₄). and was obtained from Agro Science Company, Egypt. Weeds are removed from the pots manually during the growing seasons. Selenium treatments were sprayed four times per season, on 5th July, 5th August, 5th September and 5th October. Also, different irrigation regime treatments were started from 5th July until the end of planting season at the end of October for the two seasons. The soil water capacity (SWC) is calculated according to the [28] method. This procedure involves tagging 500 g of soil sample completely saturated with distilled water and leaving it to drain the excess water for 24 h. The weight of saturated soil sample is calculated (Ww) and dried in an oven for 24 h at 105^◦C. The oven dry weight (Wd) is estimated and then the soil water capacity is calculated as follows:

Recorded data

The flowers were collected at weekly intervals, when the central whorl of petal was in opened stage. Four flower collection were taken. These flowers were collected from all experimental units. Five chrysanthemum plants were selected from each treatment to measure the growth, flowering, and chemical characteristics. The vegetative parameters represented by the plant height (cm), plant fresh weight (g) and plant dry weight (g) were recorded at the stage of bud initiation. While flowering measurements, including days to flowering (days), length of stalk (cm), diameter of flower (cm), fresh weight of individual flower (g) and inflorescences number per plant were measured at the flowering stage.

Photosynthetic pigments

The photosynthetic pigments i.e. chlorophyll a & b and carotenoids were determined as mg/g FW of leaves by using spectrophotometer (T60 UV–Visible spectrophotometer, PG Instruments Limited, Uk) method described by [29].

Ion determination

About 0.1 g sample of dried leaves with 4 ml of conc. sulphuric acid were put in the digestion flasks, and incubated overnight at laboratory conditions. 1 mm of 1:1 v/v HClO₃:H₂SO₄ was poured down throughout the perimeters of digestion flasks, well mixed, then put at 250 °C onto the hot plate awaiting fume formation. Above processes were repetitive with the addition of 1 ml mixture of HClO₃/H₂SO₄ once required till the solution was colorless. Then the extract is put in the volumetric flask and made the volume up to 50 mm, and the extract was filtered and used for determining nitrogen, phosphorus and potassium. Total N and K were estimated by micro-Kjeldahl methods and using a fame photometer [30]. P was calculated by ascorbic acid protocol and ammonium molybdate [31].

Proline determination

Proline in the dry leaves was extracted and determined following the method of [32], using acid ninhydrin reagent. Proline level was estimated from a standard curve and expressed as mg/gDW.

Phytohormones

In this experiment, endogenous hormones included gibberellic acid (GA₃) and abscisic acid (ABA) were analyzed in chrysanthemum leaves using GLC (Varien Vesta, 6000). The extraction and estimation of the two endogenous hormones were followed the method of Ünyayar et al. [33].

Statistical analysis

The data were collected, tabulated, and the average of two seasons was taken. Statistical analysis was performed using Costat software, 1085, according to the method of [34], and the least significant difference test (LSD) at 5% level was calculated. The data in tables are presented as mean ± SE (Standard Error). The correlation analysis was performed according to Pearson correlation coefficients (p ≤ 0.05 and p ≤ 0.01).

Results

Effect of Soil Water Capacities levels (SWC)

Effects on growth characteristics

Data in Table 3 showed the response of plant height, plant fresh and plant dry weight of chrysanthemum plants as affected by soil water capacities (SWC). Significant differences between growth characteristics were detected as a result of various levels of SWC. The highest values of plant height (58.63 ± 1.14 cm), plant fresh weight/plant (150.97 ± 2.42 g) and plant dry weight/plant (54.46 ± 1.93 g) were noticed with the normal level of SWC (100%), while the lowest ones were registered with the lowest SWC level (60%).

Table 3.

Response of the plant growth parameters of chrysanthemum plants (Mean ± SE) as affected by different Soil Water Capacities levels (SWC)

	Plant height (cm)	Plant fresh weight/plant (g)	Plant dry weight/plant (g)
	Mean ± SE
100	58.63 ± 1.14	150.97 ± 2.42	54.46 ± 1.93
80	50.65 ± 1.52	127.94 ± 2.67	46.48 ± 1.73
60	38.13 ± 1.09	75.23 ± 4.21	41.72 ± 0.69
LSD 5%	5.41	2.11	7.46

Effects on flowering characteristics

Results in Table 4 showed the response of flowering traits of chrysanthemum plants as influenced by SWC levels. Decreasing SWC levels resulted in a significant decrease in these characteristics. Applying 100% SWC produced the highest values of stalk length (13.68 ± 0.25 cm), flower diameter (6.77 ± 0.07 cm), individual flower weight (5.84 ± 0.10 g) and number of inflorescences/plant (48.08 ± 1.81) as compared to the other SWC levels. Contrary, applying the least SWC level (60%) resulted in the lowest values of stalk length (9.50 ± 0.07 cm), flower diameter (5.44 ± 0.08 cm), individual flower weight (4.51 ± 0.07 g) and number of inflorescences/plant (25.60 ± 0.67).

Table 4.

Response of the flowering parameters of chrysanthemum plants (Mean ± SE) as affected by different Soil Water Capacities levels (SWC)

SWC (%)	Stalk length (cm)	Flower diameter (cm)	Individual flower weight (g)	Number of inflorescences/plant
	Mean ± SE
100	13.68 ± 0.25	6.77 ± 0.07	5.84 ± 0.10	48.08 ± 1.81
80	11.19 ± 0.10	6.50 ± 0.09	5.02 ± 0.08	40.32 ± 1.69
60	9.50 ± 0.07	5.44 ± 0.08	4.51 ± 0.07	25.60 ± 0.67
LSD 5%	0.29	0.09	0.21	9.68

Effects on phytohormones

Results in Table 5 showed the response of phytohormones in terms of GA₃ and ABA of chrysanthemum plants as influenced by SWC levels. Decreasing SWC levels resulted in a significant decrease in GA₃ content and a significant increase in ABA content. Applying 100% SWC produced the highest values of GA₃ (4.47 ± 0.17 mg/g) and the least value of ABA (0.95 ± 0.03 mg/g) as compared to the other SWC levels.

Table 5.

Response of GA₃ and ABA contents (mg/g) of chrysanthemum plants (Mean ± SE) as affected by different Soil Water Capacities levels (SWC)

SWC (%)	GA3	ABA
	Mean ± SE
100	4.47 ± 0.17	0.95 ± 0.03
80	3.94 ± 0.12	1.05 ± 0.04
60	3.08 ± 0.19	1.12 ± 0.04
LSD 5%	0.28	0.24

Effects on chlorophylls and carotenoids

Figures 1, 2 and 3 showed that the maximum concentrations of chlorophyll a (0.40 ± 0.01 mg/g FW), chlorophyll b (0.38 ± 0.01 mg/ g FW) and carotenoids (0.46 ± 0.01 mg/g FW) in the chrysanthemum plant were detected under well-watered plants (SWC 100%), while the lowest ones (0.13 ± 0.00, 0.16 ± 0.00 and 0.24 ± 0.01 mg/g FW) were recorded under severe water stress (SWC 60%), respectively. Additionally, the concentrations of chlorophyll a, chlorophyll b and carotenoids were decreased by 52.27%, 27.30% and 26.35% under moderate water stress (SWC 80%), respectively. The concentrations of chlorophylls reduced under both severe and moderate water stress.

Fig. 1.

Response of the chlorophyll a (mg/g FW) of chrysanthemum plants as affected by Selenium (Se) concentrations grown under different Soil Water Capacities levels (SWC)

Fig. 2.

Response of the chlorophyll b (mg/g FW) of chrysanthemum plants as affected by Selenium (Se) concentrations grown under different Soil Water Capacities levels (SWC)

Fig. 3.

Response of the carotenoids (mg/g FW) of chrysanthemum plants as affected by Selenium (Se) concentrations grown under different Soil Water Capacities levels (SWC)

Effects on N, P and K%

As shown in Figs. 4, 5 and 6, ions percentage in terms of N, P and K of chrysanthemum plant significantly decreased with decreasing soil water capacities (SWC) levels. The highest values of N, P and K contents (3.24%, 1.28% and 1.49%) and the lowest values (1.45%, 0.64% and 0.69%) were observed in SWC 100% and SWC 60%, respectively.

Fig. 4.

Response of the N% in shoots of chrysanthemum plants as affected by Selenium (Se) concentrations grown under different Soil Water Capacities levels (SWC)

Fig. 5.

Response of the P % in shoots of chrysanthemum plants as affected by Selenium (Se) concentrations grown under different Soil Water Capacities levels (SWC)

Fig. 6.

Response of the K % in shoots of chrysanthemum plants as affected by Selenium (Se) concentrations grown under different Soil Water Capacities levels (SWC)

Effects on proline content

Figure 7 showed the proline concentration in chrysanthemum plants as affected by SWC levels. The highest concentration of proline (1.55 mg/g DW) was detected under severe water stress (SWC 60%) compared to well-watered plants (0.93 mg/g DW).

Fig. 7.

Response of the proline content (mg/g DW) of chrysanthemum plants as affected by Selenium (Se) concentrations grown under different Soil Water Capacities levels (SWC)

Effect of Se levels

Effects on growth characteristics

Significant differences between plant growth measurements were detected with Se concentrations. Results proved that increasing Se level up to Se₂₀₀ resulted in the highest values of plant height (53.91 ± 3.23 cm), plant fresh weight (131.28 ± 9.74 g), and plant dry weight (51.30 ± 2.71 g), while the lowest ones were recorded with untreated plants (Table 6).

Table 6.

Response of the plant growth parameters of chrysanthemum plants (Mean ± SE) as affected by Selenium (Se) concentrations

Se levels (mg/l)	Plant height (cm)	Plant fresh weight/plant (g)	Plant dry weight/plant (g)
	Mean ± SE
Se0	44.21 ± 2.79	109.86 ± 12.11	44.00 ± 2.32
Se100	47.92 ± 3.00	112.47 ± 11.99	46.26 ± 2.24
Se150	50.49 ± 3.29	118.59 ± 11.80	48.64 ± 2.34
Se200	53.91 ± 3.23	131.28 ± 9.74	51.30 ± 2.71
LSD 5%	0.95	3.95	0.66

Effects on flowering characteristics

Significant differences in flowering characteristics were detected with Se concentrations as shown in Table 7. Chrysanthemum plants received Se₂₀₀ have the highest stalk length (12.02 ± 0.72 cm), flower diameter (6.57 ± 0.20 cm), individual flower weight (5.47 ± 0.22 g), and number of inflorescences/plant (41.67 ± 4.47) as compared to other Se concentrations. Each increase in Se concentration resulted in a significant increase in the flowering measurements.

Table 7.

Response of the flowering parameters of chrysanthemum plants (Mean ± SE) as affected by Selenium (Se) concentrations

Se levels (mg/l) (B)	Stalk length (cm)	Flower diameter (cm)	Individual flower weight (g)	Number of inflorescences/plant
	Mean ± SE
Se0	10.93 ± 0.56	5.90 ± 0.21	4.81 ± 0.19	33.81 ± 3.01
Se100	11.27 ± 0.57	6.14 ± 0.21	4.98 ± 0.18	37.30 ± 3.34
Se150	11.60 ± 0.61	6.33 ± 0.20	5.23 ± 0.20	39.22 ± 3.36
Se200	12.02 ± 0.72	6.57 ± 0.20	5.47 ± 0.22	41.67 ± 4.47
LSD 5%	0.36	0.09	0.08	2.36

Effects on phytohormones

Significant differences in phytohormones contents were detected with Se concentrations (Table 8). Chrysanthemum plants received Se₂₀₀ have the highest GA₃ (4.50 ± 0.20 mg/g) and lowest ABA (0.88 ± 0.01 mg/g) as compared to other Se concentrations.

Table 8.

Response of GA₃ and ABA contents (mg/g) of chrysanthemum plants (Mean ± SE) as affected by Selenium (Se) concentrations

Se levels (mg/l) (B)	GA3	ABA
	Mean ± SE
Se0	3.16 ± 0.20	1.14 ± 0.05
Se100	3.55 ± 0.26	1.16 ± 0.03
Se150	4.09 ± 0.17	0.97 ± 0.02
Se200	4.50 ± 0.20	0.88 ± 0.01
LSD 5%	0.61	0.14

Effects on chlorophylls and carotenoids

As expected, the presented results in Figs. 1, 2 and 3 indicated that the maximum concentration of chlorophyll a (0.270 mg/g FW), chlorophyll b (0.309 mg/ g FW) and carotenoids (0.398 mg/g FW) in the chrysanthemum plant was obtained with the application of Se₂₀₀. In addition, the concentrations of photosynthesis pigments were improved by 27.96%, 30.40% and 32.67% with the application of 200 mg/l Se (Se₂₀₀), respectively as compared to the control.

Effects on N, P and K%

Data presented in Figs. 4, 5 and 6 showed the influence of Se supplementation on photosynthetic pigments of chrysanthemum. The highest values of N, P and K (2.57%, 1.03% and 1.23%) were produced from applying Se at 200 mg/l (Se₂₀₀), while the lowest ones were achieved with the control.

Effects on proline content

Figure 7 showed results concerning the effect of Se levels. The highest proline concentration (1.40 ± 0.10 mg/g DW) as compared to without applying Se (1.07 ± 0.08 mg/g DW). Also, the other Se concentrations (Se₁₀₀ and Se₁₅₀) improved proline contents when compared with the control.

Effect of interaction between SWC and Se levels

Effects on growth characteristics

The interaction between growth parameters was significantly different as a result of combination between SWC and Se levels (Table 9). Plants treated with 100% SWC plus Se₂₀₀ had the highest plant height (62.93 ± 1.15 cm), plant fresh weight (160.20 ± 3.93 g) and plant dry weight (59.87 ± 3.53 g) when compared to the other combinations. On the other hand, results showed that the lowest values of the plant growth measurements were registered with interaction between 60% level of SWC plus Se₀.

Table 9.

Response of the plant growth parameters of chrysanthemum plants (Mean ± SE) as affected by interactions between Selenium (Se) concentrations and different Soil Water Capacities levels (SWC)

SWC (%) (A)	Se levels (mg/l) (B)	Plant height (cm)	Plant fresh weight/plant (g)	Plant dry weight/plant (g)
		Mean ± SE
100	Se 0	53.47 ± 1.54	143.70 ± 4.08	50.43 ± 3.83
	Se 100	57.83 ± 0.74	147.63 ± 3.47	52.30 ± 3.75
	Se 150	60.27 ± 0.24	152.33 ± 3.03	55.23 ± 3.88
	Se 200	62.93 ± 1.15	160.20 ± 3.93	59.87 ± 3.53
80	Se 0	44.17 ± 1.00	121.77 ± 4.09	43.00 ± 3.75
	Se 100	48.50 ± 1.05	122.00 ± 4.41	45.40 ± 3.76
	Se 150	53.00 ± 1.27	129.33 ± 3.62	47.80 ± 3.46
	Se 200	56.93 ± 1.14	138.67 ± 3.56	49.70 ± 3.61
60	Se 0	35.00 ± 2.22	64.10 ± 6.00	38.57 ± 0.41
	Se 100	37.43 ± 1.54	67.77 ± 5.53	41.07 ± 0.37
	Se 150	38.20 ± 1.26	74.10 ± 5.73	42.90 ± 0.44
	Se 200	41.87 ± 2.23	94.97 ± 2.14	44.33 ± 0.78
LSD 5%		5.58	6.28	7.52

Effects on flowering characteristics

The interaction between SWC plus Se treatments was significant for flowering parameters (Table 10). Chrysanthemum plants supplied with 100% SWC plus Se₂₀₀ had the highest flowering parameters in terms of stalk length (14.73 ± 0.09 cm), flower diameter (7.07 ± 0.09 cm), individual flower weight (6.30 ± 0.06 g) and number of inflorescences/plant (55.37 ± 1.00) relative to the other combinations. Meanwhile, the lowest values of stalk length (9.20 ± 0.06 cm), flower diameter (5.10 ± 0.06 cm), individual flower weight (4.23 ± 0.09 g) and number of inflorescences/plant (24.13 ± 1.24) were produced with the interaction between 60% SWC level with Se₀.

Table 10.

Response of the flowering parameters of chrysanthemum plants (Mean ± SE) as affected by interaction between Selenium (Se) concentrations and different Soil Water Capacities levels (SWC)

SWC (%) (A)	Se levels (mg/l) (B)	Stalk length (cm)	Flower diameter (cm)	Individual flower weight (g)	Number of inflorescences/plant
		Mean ± SE
100	Se 0	12.90 ± 0.55	6.50 ± 0.06	5.50 ± 0.06	42.10 ± 2.65
	Se 100	13.30 ± 0.06	6.70 ± 0.06	5.60 ± 0.06	46.70 ± 2.74
	Se 150	13.77 ± 0.27	6.80 ± 0.06	5.97 ± 0.09	48.17 ± 3.36
	Se 200	14.73 ± 0.09	7.07 ± 0.09	6.30 ± 0.06	55.37 ± 1.00
80	Se 0	10.70 ± 0.06	6.10 ± 0.06	4.70 ± 0.06	35.20 ± 4.23
	Se 100	11.10 ± 0.06	6.40 ± 0.06	4.93 ± 0.09	39.60 ± 2.97
	Se 150	11.43 ± 0.12	6.67 ± 0.07	5.13 ± 0.12	41.97 ± 3.09
	Se 200	11.53 ± 0.09	6.83 ± 0.09	5.30 ± 0.06	44.50 ± 1.80
60	Se 0	9.20 ± 0.06	5.10 ± 0.06	4.23 ± 0.09	24.13 ± 1.24
	Se 100	9.40 ± 0.06	5.33 ± 0.09	4.40 ± 0.06	25.60 ± 1.37
	Se 150	9.60 ± 0.06	5.53 ± 0.03	4.60 ± 0.06	27.53 ± 1.60
	Se 200	9.80 ± 0.06	5.80 ± 0.06	4.80 ± 0.06	25.13 ± 0.83
LSD 5%		0.60	0.17	0.25	10.25

Effects on phytohormones

The interaction between SWC plus Se treatments was significant for phytohormones contents. Chrysanthemum plants supplied with 100% SWC plus Se₂₀₀ had the highest GA₃ content (5.21 ± 0.07 mg/g) and lowest ABA content (0.85 ± 0.02 mg/g) relative to the other combinations (Table 11).

Table 11.

Response of GA₃ and ABA contents (mg/g) of chrysanthemum plants (Mean ± SE) as affected by interaction between Selenium (Se) concentrations and different Soil Water Capacities levels (SWC)

SWC (%) (A)	Se levels (mg/l) (B)	GA3	ABA
		Mean ± SE
100	Se 0	3.69 ± 0.05	0.95 ± 0.03
	Se 100	4.31 ± 0.06	1.10 ± 0.04
	Se 150	4.65 ± 0.06	0.90 ± 0.02
	Se 200	5.21 ± 0.07	0.85 ± 0.02
80	Se 0	3.40 ± 0.03	1.20 ± 0.04
	Se100	3.80 ± 0.04	1.15 ± 0.05
	Se 150	4.11 ± 0.05	0.95 ± 0.01
	Se 200	4.45 ± 0.05	0.88 ± 0.02
60	Se 0	2.40 ± 0.02	1.28 ± 0.03
	Se 100	2.55 ± 0.03	1.23 ± 0.02
	Se 150	3.50 ± 0.04	1.05 ± 0.02
	Se 200	3.85 ± 0.08	0.92 ± 0.01
LSD 5%		0.91	0.41

Effects on photosynthetic pigments

Data in Figs. 1, 2 and 3 showed that the combination between SWC 100% plus Se₂₀₀ resulted in the highest values of chlorophyll a (0.435 mg/g FW), chlorophyll b (0.425 mg/ g FW) and carotenoids (0.540 mg/g FW) in the chrysanthemum plant when compared to the other combinations. In contrary, the lowest values of chlorophyll a, chlorophyll b and carotenoids were recorded in SWC 100% without Se application.

Effects on N, P and K%

Regarding the effect of combination between SWC and Se levels, results revealed that the highest values of N, P and K (3.58%, 1.38% and 1.63%) were recorded with well-watered plants plus application of 200 mg/l Se relative to the other interactions (Figs. 4, 5 and 6).

Effects on proline content

Figure 7 showed the effect of interaction between SWC and Se levels on the proline content. The highest proline concentration (1.75 mg/g DW) was related to combination between SWC 60% plus applying Se₂₀₀. Meanwhile, interaction between well-watered plants (SWC 100%) plus Se₀ produced lowest values of proline content (0.78 mg/g DW).

Correlation of characters

The correlation analysis revealed that plant height had a significant positive correlation with plant fresh weight, plant dry weight, stalk length, flower diameter, individual flower weight, number of inflorescences/plant, and GA₃, with Pearson correlation coefficients (r) ranging from 0.912 to 0.977 (Table 12). Gibberllic acid (GA₃) has a strong positive effect on various characteristics. Results showed that GA₃ is positively correlated (0.01 level) with all tested traits, including plant height, plant fresh weight, and plant dry weight, with (r) values ranging from 0.840 to 0.912. Hormonal interaction as ABA showed strong negative correlation (-0.839) between GA₃ and ABA. This is physiologically expected as GA₃ promotes growth while ABA typically inhibits it or mediates stress. ABA shows an antagonistic relationship with growth characteristics in this study. There is a significant negative correlation between ABA and plant height, plant fresh weight and plant dry weight. For instance, its correlation with dry weight is -0.757. Higher levels of ABA (often triggered by stress) are statistically linked to a reduction in the physical dimensions and weight of the plant. Proline is negatively correlated (0.05 level) with plant height (-0.649) and plant fresh weight (-0.728). This suggests that as the plant accumulates more proline, there is a corresponding decrease in growth. It has a weak non-significant correlation with GA₃ (-0354). It shows a very weak positive correlation with ABA (-0.790), which is not statistically significant in this case. In conclusion, the data suggests that, while GA₃ drives growth and different traits, the increase in ABA and proline serves as a marker for growth retardation, likely due to underlying a drought stress factor.

Table 12.

Correlation coefficients for growth, flowering and biochemical traits of chrysanthemum. *and ** show significance at 1 and 5% levels, respectively. Plant Height (PH), plant Fresh Weight (FW), plant Dry Weight (DW), Stalk Length (SL), Flower Diameter (FD), Individual Flower Weight (IFW), Number of Inflorescences/plant (NI), GA3, ABA and Proline (P)

Correlations
	PH	FW	DW	SL	FD		IFW	NI	GA3	ABA	P
PH	1
FW	0.967**	1
DW	0.953**	0.896**	1
SL	0.948**	0.930**	0.969**	1
FD	0.976**	0.974**	0.895**	0.888**	1
IFW	0.957**	0.914**	0.997**	0.979**	0.900**		1
NI	0.977**	0.955**	0.934**	0.953**	0.959**		0.936**	1
GA3	0.912**	0.869**	0.920**	0.840**	0.917**		0.911**	0.873**	1
ABA	-0.716**	-0.650*	-0.757**	-0.618*	-0.716**		-0.750**	-0.612*	-0.839**	1
P	-0.649*	-0.728**	-0.580*	-0.760**	-0.603*		-0.619*	-0.711**	-0.354	0.079	1

**. Correlation is significant at the 0.01 level (2-tailed)

*. Correlation is significant at the 0.05 level (2-tailed)

Discussion

In our study, it was indicated that after the exogenous supplementation of Se in non-and-stressed chrysanthemum plants, improved growth and flowering were noticed. Under drought conditions, the growth and development of the plant is inhibited as a result of decreasing in extensibility and turgor of the cell wall [35]. Less moisture condition level led to induce abscisic acid hormone of roots, the responsible for reducing leaf growth and production [36]. Supplying chrysanthemum plants with the lower irrigation regime resulted in reducing the vegetative growth traits as compared to the higher one [10]. In the present study, high level of SWC improved the growth traits of chrysanthemum plant, while the low one (60%) reduced the plant growth characteristics. These findings were in accordance with that found by [37] indicated that exposing plants to drought stress inhibits CO₂ assimilation because it damages the membrane, closes the stomata, and disrupts the action of enzymes, leading to a lack of carbohydrates necessary for growth and development of the plant. It is known that plant growth and production are better with optimal irrigation level, while exposing plant to drought reduces growth and productivity [9, 38, 39]. On the other hand, results pointed out that applying Se levels resulted in mitigate water deficit stress and improve growth parameters of chrysanthemum plant [22]. revealed that selenium, as an important stress ameliorant, has a beneficial impact on alleviating detrimental impacts of the environmental threats. The suggested that, the ameliorative effect of selenium was suggested by improved content of soluble sugar and proline, content of loganinic acid and gentiopicroside in roots, and mitigated the inhibition in growth characteristics of Gentiana macrophylla plants. Selenium plays a vital role in mitigating the harmful effect of drought stresses on plants by inducing different physio-biochemical and metabolic processes [40, 41]. This study demonstrated that water stress in chrysanthemum plant reduced GA₃ content and increased ABA content, while spraying with Se improved GA₃ content and reduced ABA. The same findings were previously reported by [42]. Also, our findings were in agreement with that of [23], who revealed that Se application on Echinacea purpurea plants under drought stress conditions mitigated the adverse effect of drought stress and improved vegetative growth and productivity traits due to the positive effects on antioxidant properties.

Our findings indicated that well-watered chrysanthemum plants produced higher flowering traits than under other irrigation treatments. Ngouajio et al. [43, 44] clarified that optimum application of water irrigation, soil nutrients and photosynthetic rate were responsible for producing maximum tomato yield. Previous researches have also perceived a comparable improvement in flowering traits of chrysanthemum when applying optimum irrigation [10, 44]. On the other side, supplying Se at different concentrations leads to improving flowering characteristics in chrysanthemum, whether for plants exposed to water stress or well-irrigated [45]. reported that selenium mitigated the adverse effects of strawberry plant under drought stress, which may be ascribed to the fact that Se has direct or indirect functions on physiological mechanisms of the plant. Also [46], exhibited that selenium acts as an activator in canola plant under drought stress and causes the improvement of the plant tolerance. Selenium improves the uptake of important substances, preserves the stability of plasma membranes, and induces the activity of different antioxidant enzymes, so mitigating the adverse effects in plant under abiotic stresses [47].

Exposing plants to drought stress leads to increase the contents of reactive oxygen species (ROS), which causes an improvement of the lipid peroxidation of the membranes and decomposition of the chlorophylls in the plants [48]. Moreover, the decline in chlorophyll contents under drought stress conditions may be due to the reduction of nutrient absorption that negatively impacts the biosynthesis of chlorophylls [49]. Chlorophyll contents are generally lower under drought stress conditions due to the decrease in chlorophyllase activity, an enzyme involved in the chlorophyll formation [50]. Our findings were in good line with those of [51] on Lallemantia iberica plants and [52] on Ocimum basilicum plants. On the other side, applying selenium levels resulted in enhancing the concentrations of chlorophylls and carotenoids. Supplying stress-modulating compounds such as selenium decreased the lipid peroxidation of membranes and the negative effect of water stress, thereby influencing the contents of photosynthetic pigments in the plant cells [53]. These results were in accordance with those obtained by [54], who indicated that the application of selenium improved the content of photosynthetic pigments in the Chrysanthemum morifolium plant.

Water stress conditions usually reduce the soil nutrient accessibility and ultimately lessen the ion content in the plant tissue [55]. Water stress situations reduced uptake of plant nutrition [56]. The reducing in N % was considered as the main responsible factor for leaf senescence and photosynthesis decline [57]. Moreover, there was a significant reduction in leaf P % in Ocimum gratissimum [58] and reduce in P % and K % in Thymus daenensis under water stress conditions [59]. The decreasing in N, P and K content occurs in leaves because water stress disturbs guard cell turgidity and stomata movement, which leads to reduce photosynthesis and, then produced plant biomass [60]. On the other hand, application of selenium levels resulted in improve ions percentage in chrysanthemum plant. Se applications regulate the uptake and transfer of these vital ions, and it may help to activate antioxidants that lower ROS levels, enabling plant to better survive within stress conditions [61]. Se supplementation to the plants increased the levels of N, P and K. These results agree with [62–64], who observed a gradual rise in the distribution of macro- and microelement in plants through exogenous Se treatment under stress.

Therefore, the increasing proline and soluble sugars under water stress conditions maintain the ROS level within the normal range (detoxification of ROS), decreasing lipid peroxidation, stabilizing the membranes and increasing cell turgor [65]. It has been suggested that the application selenium under water stress conditions prevents the oxidative stresses by decreasing the ROS content in a normal range and inducing the expression of stress-responsive proteins [66]. In addition, applying of selenium improved the soluble sugars and proline contents, which may be due to the vital role of Se in reducing chlorophyll decomposition and inducing the photosynthesis rate, which improves the contents of carbohydrate and other biomolecules under drought-stress conditions [62]. Moreover, synthesis of stress proteins in the plant in pervasive responses against various stresses as water stress [67]. The improvement of proteins induces accumulation of proline content and then, induces drought tolerance [68, 69].

Conclusion

Water deficit stress is one of the abiotic stress problems that disrupt the plant development and growth and thus lead to productivity decline. Supplementation of selenium under water deficit conditions can cause plant to adapt to water deficit. The present study indicated that the application of selenium at different concentrations modulates the negative effects of water deficit conditions by improving chlorophylls, carotenoids, and proline contents. In addition, applying of selenium improved the growth, flowering and yield traits of chrysanthemum plant. It can be concluded that supplementation of selenium, especially at 200 mg/l Se, improved plant tolerance and increased the growth, flowering and yield of chrysanthemum plant under water deficit conditions.

Authors’ contributions

Conceptualization, M.M.; methodology, M.M., E.M.S. and M.A.A.A.; software, H.B.G., T.M.E.; validation, A.A.M.; investigation, A.M.A. and E.A.S.; resources, M.M. and A.M.A.; data curation, S.D.A.; writing—original draft preparation, M.M.; writing—review and editing, E.M.S., M.A.A.A. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no funding.

Data availability

The datasets analyzed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.