2.1 Vegetative and floral examination

The vegetative and floral parameters for each treatment were observed in selected healthy plants such as plant height (cm), stalk length (cm), No of flowers per plant, Fresh and Dry weight of flower (g), flower size and Days to first floral harvest etc. Digital Image Analysis was done as described by O’Neal et al. (2002).

2.2 Vase life of flower (days).

Vase life of flowers was estimated by counting the days taken to observable wilting and twisting of cut stems more than 90° (He et al., 2006).

2.3 Total chlorophyll contents, chlorophyll a, chlorophyll b, carotenoids

Chlorophyll and carotenoids contents were estimated as described by Krishnan et al. (1996). 100 mg of leave sample was mixed with 20 mL of acetone (80%) in graduated tube and incubated at 4C° ± 2C° in dark place. The mixture was shaken for efficient extraction of pigments. The extract liquid was filtered by glass wool after 48 h of incubation and transferred to another tube by removing leaf pieces. The extracted liquid then was marked volume up to 25 mL with 80% acetone. 3 mL of this solution was taken in a sealed quartz-glass cuvettes and absorption was recorded at 1 nm wavelength in UV visible spectrophotometer (Optizen Pop, Mecasys – Korea). The quantity of pigments was calculated using the equations cited by Dere et al. (1998).

Chlorophyll a = 11.75 A662 − 2.350 A645

Chlorophyll b = 18.61 A645 − 3.960 A662

Chlorophyll total= (Chl.a + Chl.b)

Carotenoids = 1000 A470 − 2.270 Chlorophyll a − 81.4 Chlorophyll b/227

2.4 Proline (µm mg⁻¹)

Proline content was measured in leaves at three growth stages as described by Bates et al. (1973).

2.5 Phenols (mg GAE/g of extract)

Folin-Ciocalteu method was used to estimate phenolic contents in rose extract (Marquele et al., 2005). 1 mL of extract was mixed with 2 mL of 1 M Folin-Ciocalteu agent and allow to rest for 5 mins. Then 2 mml of sodium carbonate (7.5%) was mixed to the solution and kept for 30 mins at room temperature followed by centrifugation @ 2000 rpm for 10 mins spectrophotometric absorbance of supernatant was noted at 760 nm wavelength. 1 M Folin-Ciocalteu reagent was used as blank. Gallic acid curve was used to estimate the phenolic contents expressed as gallic acid equivalents.

2.6 Flower quality

Flower quality (flower shape, growth of bud, diameter size and color) were evaluated by using method showed by Cooper and Spokas (1991).

2.7 Statistical analysis

The data recorded was subjected to Analysis of variance following Steel et al. (1997) through Statistix 8.1. Significance of differences among treatment means was checked at α = 5% using LSD test.

3.1 Vegetative and floral examination

In this experiment, statistically data was recorded that plant height, showed significant variances amongst PGR treatments. Application of both Ascorbic acid and HA caused significant increase in plant height. Among the four levels of PGR in first year maximum plant height was showed T2 (123.5 cm ± 0.1a) followed by T3 (118.4 cm ± 0.1a) as compared to T1 (88.5 cm ± 0.3d). In second year, maximum plant height was observed in T2 followed by T4 as compared to control. The treatment T2 was expressed max flower diameter in first year than control. In second year, max flower diameter revealed by T2 (12.4 cm ± 0.1a) and min in T1 (5.3 cm ± 0.2c). In both years flower stalk length, no of flower per plant was recorded highest in T2 as compared to T1 (Fig. 1).

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Fig. 1

Effect of different plant growth regulators on physical characteristics of Rosa hybirda plants during 2017/2018 and 2018/2019 season.

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3.2 Fresh and dry weight of flower

Different PGR at same concentration (60 mg L⁻¹) showed max fresh and dry weight of flower as compared to control. The highest fresh weight of flower exhibited by T2 (15.95 g ± 0.8a) in first year and T2 (17.45 g ± 0.8a) in second year. In both years, rose flower treatment T2 showed the max dry weight (2.20 g ± 0.2a) and (1.74 g ± 0.6a) as compared to control T1.

3.3 Vase life of flower (days)

Statistical analysis of the data for vase life of the spikes revealed significant differences among the PGRs, their concentrations and interaction between these two factors. Both the PGRs significantly improved the vase life of flower as compared to control and were similar in their effect. Among the PGR concentrations, the ascorbic acid @ (60 mg L⁻¹) resulted in maximum vase life of flower in both years. Some PGR increase the vase life but some decrease the vase life of flower. The minimum vase life was recorded in the case of control (T1), followed by (T5) in both years (Table 1).

3.4 Total chlorophyll and carotenoids contents

Statistical analysis of the data for the parameters indicated significant differences among PGRs and their interaction. The chlorophyll content was increased remarkably by the different PGRs at same level applied. Ascorbic acid application resulted in maximum leaf chlorophyll content, followed by the humic acid application in both seasons. However, the control plants (T1) had the minimum chlorophyll contents, carotenoids in their leaves. The concentration of these PGRs (i.e. 60 mg L⁻¹) resulted in significantly higher chlorophyll content and carotenoids in T2, T3, followed by T4 in both years’ data were recorded. Among the interaction means, results revealed that ascorbic acid used at 60 mg L⁻¹ resulted in maximum chlorophyll contents, carotenoids clearly indicating the dominating effect of ascorbic acid and humic acid on the rose plant as compared to control (Table 2).

3.5 Proline (µm mg⁻¹)

Considerable increase in proline contents of leaves was observed in response to exogenous application of plant growth regulators (Table 3). The maximum value for proline contents of leaves was recorded in plants receiving treatments (T2, T3) applied at flowering stage in both seasons (Table 3). The lowest proline content in leaves treatments (T1) followed by (T5) showed in first year values (Table 3). Second years values were recorded min proline content of rose plant in T1 followed T5 (Table 3).

3.6 Phenols (mg GAE/g of extract)

Significant variation was observed in Phenolic contents of rose Flower Extracts in response to treatment with PGRs, ranging from 86.66 ± 1.2d to 101.07 ± 3.0a mg GAE/g. Total phenolic content of second year treatments of the rose flower were measured, ranging from 52.6 ± 0.1c to 73.1 ± 0.2a mg GAE/g (Table 3).

3.7 Flower quality

Quality of cut flower also showed positive response to PGRs application at various stages of growth and development. Maximum value for flower quality index (4.6 ± 0.2a) was noted in response to T2 in comparison to while lowest value (3.7 ± 0.2b) in T1 (control). In second year, highest flower quality (5.0 ± 0.6a) was recorded in T2 as compared to T1. Maximum scores were obtained by T2 followed by T3 and T4 while minimum scores were obtained by T1 (control) in both years (Table.1).

3.8 Days of first flower harvest (days)

Ascorbic acid and humic acid significantly influenced the days of first flower harvest. Among different PGRS treatment revealed maximum days in T2 followed by T3. Data were recorded during the both years of rose plant maximum days (87.1 ± 1.9a) and (77.2 ± 1.9a). Whereas, minimum days (76.6 ± 1.9c) and (66.6 ± 1.9c) were observed in T1 for Rose hybrida (Table 3).

4.1 Vegetative and floral examination

Positive effect of salicylic acid on plant height, plant vigor, plant biomass accumulation and dry weight has been well documented in marigold, basil, eggplant, sweet pepper, marjoram and many other ornamental plants (Basit et al., 2018).

Likewise exogenous application of ascorbic acid is reported to increase vegetative growth, flowers per plant, flower weight (fresh and dry) and bio-accumulation of nutrients in Italian cypress, cut gerbera and rose mellow (Farahat et al., 2007; Samaneh et al., 2013). Humic acid is also reported to increase plant height in canola and flower number & quality, dry weight of flower in marigold (Behzad and Zarchini, 2014; Ehsan et al., 2012). Moreover, application of thiourea is documented to increase flower number and quality in oriental lily. Foliar application of humic acid increased the number of flowers and dry weight of marigold (Ehsan et al., 2012). Application of humic acid increased the spike diameter and longer stem in gladiolus (Ahmad et al., 2013). Application of thiourea and salicylic acid increased the diameter of spike and flower stalk length in gladiolus (Pawar et al., 2018).

4.2 Vase life of flower (days)

Results showed that vase life of flower was increased by the application of different plant growth regulators at same concentration. Ascorbic acid enhanced the vase life of cut flower lisianthus (Sheikh et al., 2015). By the application of thiourea (1%) and salicylic acid (150 ppm) longer the vase life of flower in gladiolus (Pawar et al., 2018). HA and NPK application as foliar spray increase the shelf life in Essential. Humic acid act as auxin and enhance uptake & bioaccumulation of nutrients resulting in increased vase life of cut stem of gerbera (Baldotto and Baldotto, 2013).

4.3 Chlorophyll and carotenoids contents

Chlorophyll (a & b) and carotenoids contents increase significantly in response to foliar spray of humic acid. This increase may be attributed to accelerated nitrogen and phosphorus uptake from soil; increased biosynthesis of protein (Haghighi et al., 2012).

Foliar spray of ascorbic acid significantly influenced the total chlorophyll contents, chlorophyll a, chlorophyll b in Cupressus sempervirens L (Farahat et al., 2007). Foliar spray of thiourea helpful to increase the chlorophyll contents of leaves in coriander (Shanu et al., 2013). In Brassica napus foliar application of salicylic acid significantly enhanced the cholorophyll contents of leaf (Ghai et al., 2002).

4.4 Proline (µm mg⁻¹)

The foliar application of ascorbic acid increased the proline contents in sugarcane (Batool et al., 2012). By the application of 5% humic acid helpful to increase the proline contents in faba bean (Dawood et al., 2020). Foliar application of salicylic acid helpful to increase the proline contents in linseed (Bakry et al., 2012). Taramani et al. (2020) revealed that thiourea gives beneficial response to proline contents in maize and wheat.

4.5 Phenols (mg GAE/g of extract)

Application of 5% humic acid was helpful to increase the phenolic contents in faba bean (Dawood et al., 2020). Perveen et al. (2016) reported that thiourea increased the total phenolic contents in mung bean. Ascorbic acid at 300 ppm concentration increased the phenols in zinnia (Naglaa et al., 2018). Foliar application of Salicylic acid improved the phenols contents in maize plant (Amin et al., 2013).

4.6 Flower quality

Similarly, thiourea treatment causes internal physiological changes like assimilate distribution within the plant system which resulted in to an improvement in the quality of gladiolus flowers due to which turgidity of spikes was maintained and vase life of cut flower might have been increased (Hatamzadeh et al., 2012). Humic acid application with NPK to enhance the flower quality of gladiolus flower (Ahmad et al., 2013). Salicyclic acid and ascorbic acid significantly improved the flower quality of gladiolus (Ravanbakhsh et al., 2017).

4.7 Days to first flower harvest

Regardless, with the application of different PGR reduce the days to flower harvest. Humic acid implication proved earlier emergence of spike and more florets per spike in gladiolus (Ahmad et al., 2013). Thiourea applied at 1000 ppm concentration reduces the days to flower harvest in tuberose (Patil and Jadhav, 2010). Foliar spray of salicylic acid significantly affect the days of flowering in aster as compared to control (Kumar et al., 2017).