Effect of pruning dates and micronutrient strengths on leaf physiological parameters in jasmine

Introduction

Jasmine (Jasminum sambac Ait.) represents a significant commercial loose flower crop in India, esteemed for its beautiful and fragrant blossoms which are utilized in religious rituals, garlands, hair accessories, as well as in the perfume, cosmetic and essential oil sectors. The success of flower production is heavily reliant on effective crop management practices, with pruning being particularly crucial. This process entails the removal of older shoots to encourage vigorous new growth, enhance light availability and air circulation, decrease disease prevalence, and improve flowering outcomes (Gibson, 1984; Anderson, 1991) [3,2] . Prior research has indicated that performing pruning during December or January leads to notable improvements in both growth and flower yield for J. sambac. However, the ideal timing for pruning can differ based on cultivar and agro-climatic factors (Singh and Moe, 1980; Pal and Bose, 1981; Pawar et al., 2019; Khanchana and Jawaharlal, 2019) [16,10,12,6] . In addition to pruning, balanced nutrition is critical for enhancing plant growth, flowering capabilities, and flower quality. Among secondary and micronutrients, elements such as iron, zinc and magnesium are essential for processes including chlorophyll production, photosynthesis enhancement, enzyme activation, auxin generation, protein metabolism, carbohydrate conversion, and pollen development (Wallihan et al., 1958; Thorne, 1957; Shukla et al., 2009; Mengel and Kirkby, 2001; Marschner, 2012) [20,19,14,9,8] . A lack of these nutrients can negatively impact plant development and flower output. While there has been considerable research into the individual impacts of pruning and nutrient management separately, knowledge regarding their combined effects remains scarce. Consequently, this study was conducted to assess how varying pruning dates alongside foliar applications of iron, zinc, and magnesium influence the physiological characteristics and yield of J. sambac cv. CO.1 Gundumalli.

Materials and Methods

The research was carried out from August 2024 to July 2026 in the Floriculture and Landscaping department at the College of Horticulture, Dr. Y.S.R. Horticultural University, located in Venkataramannagudem. A Factorial Randomized Block Design (FRBD) with two replications was employed for the experiment. The first factor involved four different pruning dates (P 1 , P 2 , P 3 , and P 4 ), while the second factor included four levels of micronutrient applications (M 1 , M 2 , M 3 , and M 4 ).

Description of treatments (P1 M1) :

25 th December + (FeSO4 @ 0.3% + ZnSO4 @ 0.3% + MgSO4 @ 0.3%) (P1 M2) :

25 th December + (FeSO4 @ 0.4% + ZnSO4 @ 0.4% + MgSO4 @ 0.4%) (P1 M3) :

25 th December + (FeSO4 @ 0.5% + ZnSO4 @ 0.5% + MgSO4 @ 0.5%) (P1 M4) :

25 th December + Water spray (P2 M1) :

15 th January + (FeSO4 @ 0.3% + ZnSO4 @ 0.3% + MgSO4 @ 0.3%) (P2 M2) :

15 th January + (FeSO4 @ 0.4% + ZnSO4 @ 0.4% + MgSO4 @ 0.4%) (P2 M3) :

15 th January + (FeSO4 @ 0.5% + ZnSO4 @ 0.5% + MgSO4 @ 0.5%) (P2 M4) :

15 th January + Water spray (P3 M1) :

5 th February + (FeSO4 @ 0.3% + ZnSO4 @ 0.3% + MgSO4 @ 0.3%) (P3 M2) :

5 th February + (FeSO4 @ 0.4% + ZnSO4 @ 0.4% + MgSO4 @ 0.4%) (P3 M3) :

5 th February + (FeSO4 @ 0.5% + ZnSO4 @ 0.5% + MgSO4 @ 0.5%) (P3 M4) :

5 th February + Water spray (P4 M1) :

25 th February + (FeSO4 @ 0.3% + ZnSO4 @ 0.3% + MgSO4 @ 0.3%) (P4 M2) :

25 th February + (FeSO4 @ 0.4% + ZnSO4 @ 0.4% + MgSO4 @ 0.4%) (P4 M3) :

25 th February + (FeSO4 @ 0.5% + ZnSO4 @ 0.5% + MgSO4 @ 0.5%) (P4 M4) :

25 th February + Water spray A new J. sambac cultivar named CO.1 Gundumalli, also referred to as 'Nine Budded Gundumalli,' has been introduced by the Department of Floriculture and Landscape Architecture at Tamil Nadu Agricultural University in Coimbatore (Fig. 1). This distinct variety is noted for its increased yield of nine-budded cymes per plant, demonstrating greater productivity compared to the traditional Ramanathapuram Gundumalli variety. Rooted cuttings aged ten months were transplanted into the main field with a spacing of 1.2 x 1.2 meters. Pruning was conducted according to the established schedule up to a height of 50 cm above ground level, followed by monthly foliar applications of micronutrients post-pruning.

Regular observations were made on the pruned plants over two years (2024-25 and 2025-26), during which data were collected regarding various physiological leaf parameters such as Relative Water Content (RWC) (%), leaf area (cm²), chlorophyll content (measured in SPAD units), total phenol content (mg g⁻¹), soluble protein content (mg g⁻¹) and yield metrics like the number of flower cymes per plant. The data analysis was performed using ANOVA methods as described by Panse and Sukhatme (1985) [11] .

Results and Discussion Relative water content (RWC) and leaf area

The pooled data presented in Table 1 revealed that pruning dates, micronutrient strengths and their interaction significantly influenced relative water content (RWC) and leaf area of J. sambac. Among the pruning dates, P₃ recorded the highest mean RWC (81.61%), followed by P₂ (79.85%) and P₁ (77.17%), whereas the lowest RWC was observed in P₄ (53.93%). With respect to micronutrient strengths, M₁ registered the highest mean RWC (79.53%), followed by M₂ (77.56%), while the untreated control (M₄) recorded the lowest value (63.14%). The interaction effect was also significant, with the highest RWC (88.17%) recorded in the P₃M₁ treatment combination, whereas the lowest value (45.91%) was observed in P₄M₄. A similar trend was observed for leaf area. Among the pruning dates, P₃ produced the maximum mean leaf area (24.90 cm²), followed by P₂ (24.28 cm²) and P₁ (23.17 cm²), while P₄ recorded the minimum (20.48 cm²). Among the micronutrient treatments, M₁ resulted in the highest mean leaf area (25.10 cm²), followed by M₂ (23.62 cm²) and M₃ (22.48 cm²), whereas M₄ recorded the lowest value (21.62 cm²). The interaction between pruning dates and micronutrient strengths was significant, with the maximum leaf area (28.03 cm²) recorded under P₃M₁, while the minimum (19.71 cm²) was obtained under P₄M₄.

Chlorophyll content, total phenols and soluble proteins

The pooled data (Table 2) indicated that chlorophyll content and total phenols were significantly affected by pruning dates, micronutrient strengths and their interaction. Among the pruning dates, P₃ recorded the highest mean chlorophyll content (53.78 SPAD units), followed by P₂ (51.82 SPAD units) and P₁ (48.77 SPAD units), whereas the lowest value (38.31 SPAD units) was observed under P₄. Among the micronutrient strengths, M₁ produced the highest mean chlorophyll content (54.04 SPAD units), followed by M₂ (51.80 SPAD units), while the untreated control (M₄) registered the lowest value (41.64 SPAD units). The interaction effect was significant, and the maximum chlorophyll content (61.79 SPAD units) was recorded in P₃M₁, whereas the minimum (36.93 SPAD units) was observed in P₄M₄. The trend for total phenols was similar. The pooled results presented in Table 3 showed that soluble protein content were significantly influenced by pruning dates, micronutrient strengths and their interaction. Among the pruning dates, P₃ recorded the highest mean soluble protein content (12.27 mg g⁻¹), followed by P₂ (11.79 mg g⁻¹) and P₁ (11.28 mg g⁻¹), whereas the lowest value (9.59 mg g⁻¹) was recorded under P₄. Among the micronutrient strengths, M₁ produced the highest mean soluble protein content (12.25 mg g⁻¹), followed by M₂ (11.82 mg g⁻¹) and M₃ (10.74 mg g⁻¹), while M₄ recorded the minimum (10.12 mg g⁻¹). The interaction effect was significant, with the highest soluble protein content (13.84 mg g⁻¹) recorded under P₃M₁, whereas the lowest (9.14 mg g⁻¹) was recorded under P₄M₄.

Early pruning (P 1 ) markedly increased chlorophyll content, relative water content, total phenol content and soluble protein accumulation as compared those under later pruning dates. This might be due to rejuvenating effect by pruning, producing younger, physiologically active shoots with higher photosynthetic potential. Pruning also improved light penetration and canopy aeration, supporting chlorophyll synthesis and effective assimilate utilization. Kumaresan et al. (2017) [7] in J. sambac observed similar increases in chlorophyll and soluble protein after pruning. Sanjay et al.

(2010) [13] in mango reported comparable improvements in physiological and biochemical attributes following the operation of pruning as evident from vigorous shoot and leaf development in their study. The steady rise in micronutrient concentration from M 1 to M 3 corresponded with increases in all physiological and biochemical parameters. Iron and magnesium are directly involved in chlorophyll formation, whereas zinc activates numerous enzymes linked to photosynthesis, protein synthesis and carbohydrate metabolism. Adequacies in supply of these elements enhanced chloroplast formation, pigment accumulation and metabolic activity, elevating chlorophyll content under the high dose of M 3 . Srividhya et al. (2021) [17] in jasmine recorded higher SPAD chlorophyll readings and improved physiological efficiency after foliar micronutrient application. Shyala et al. (2019) [15] also reported chlorophyll increases from micronutrient nutrition in ornamentals. Among treatment combinations, P 1 M 3 recorded the highest values for all physiological and biochemical traits, whereas P 4 M 4 produced the lowest. The superior performance of P 1 M 3 suggests that optimal pruning combined with balanced foliar nutrition enhanced physiological efficiency and metabolic functioning.

Relative water content, an indicator of plant water status and cellular hydration, was higher under P 1 M 3 , reflecting improved water uptake, efficient translocation and maintenance of cellular turgor. Magnesium aids in osmotic regulation, while zinc helps to preserve membrane stability and stomatal function, collectively improving tissue water retention. Elevated RWC sustains physiological processes and delays dehydration. Zahed et al. (2006) [21] in gladiolus and Thamaraiselvi (2009) [18] in J. sambac linked higher tissue water content with better physiological performance and delayed senescence. Significantly greater phenol content as recorded under P 1 M 3 might be due to enhanced secondary metabolism stemming from favourable nutritional and physiological conditions. Phenolic compounds act as antioxidants and protectants against oxidative stress. Micronutrients serve as cofactors for enzymes in the phenylpropanoid pathway, promoting phenol biosynthesis. Sanjay et al. (2010) [13] in mango and Kaushik et al. (2020) [5] in peach reported increased total phenols with improved canopy management and pruning. Soluble protein content was found to increase with every increase in micronutrient levels, peaking under M 3 . This might be due to improved nitrogen assimilation, enzyme production and protein metabolism. Zinc regulates enzymes involved in protein synthesis, iron participates in nitrate reduction and amino acid formation; and magnesium supports ribosomal function and protein assembly. Hence, optimal micronutrient application could encourage greater soluble protein accumulation in leaves. Kumaresan et al.

(2017) [7] recorded similar increases in soluble proteins in J. sambac under treatments that enhanced physiological efficiency. Srividhya et al. (2021) [17] also reported higher nitrate reductase activity and protein content following foliar micronutrient application in jasmine.

Number of cymes per plant

The pooled results presented in Table 3 showed that number of cymes per plant were significantly influenced by pruning dates, micronutrient strengths and their interaction. The number of cymes per plant varied significantly among the treatments. Among the pruning dates, P₃ recorded the highest mean number of cymes (772.65 plant⁻¹), followed by P₂ (727.12 plant⁻¹) and P₁ (647.97 plant⁻¹), whereas P₄ recorded the lowest (418.38 plant⁻¹). Among the micronutrient strengths, M₁ produced the highest mean number of cymes (772.77 plant⁻¹), followed by M₂ (707.50 plant⁻¹) and M₃ (584.94 plant⁻¹), while M₄ registered the minimum (500.91 plant⁻¹). The interaction between pruning dates and micronutrient strengths was significant, with the highest number of cymes (957.00 plant⁻¹) observed in P₃M₁, whereas the lowest (364.87 plant⁻¹) was recorded under P₄M₄.

The greater numbers of buds per cyme and cymes per plant under P 1 M 3 may be due to improved sink establishment during reproduction. Bud formation depends on the availability of actively growing shoots capable of differentiating floral primordia. Early pruning increased productive shoot numbers, while optimal micronutrient nutrition ensured a steady nutrient supply for ongoing bud differentiation. Better nutritional status also reduced premature bud abortion, allowing more number of initiated buds to maturity and transformation into marketable buds. Abdou and Badran (2003) [1] in J. sambac observed similar increases in cymes and buds with pruning through improved assimilate availability. Jennoah et al. (2012) [4] reported that increased leaf production after pruning boosted carbohydrate reserves, resulting in higher bud production in jasmine.: FeSO4 @ 0.3% + ZnSO4 @ 0.3% + MgSO4 @ 0.3% M2: FeSO4 @ 0.4% + ZnSO4 @ 0.4% + MgSO4 @ 0.4% M3: FeSO4 @ 0.5% + ZnSO4 @ 0.5% + MgSO4 @ 0.5% M4: Water spray

Conclusion

Early pruning, when combined with the appropriate application of foliar micronutrients, significantly improved the physiological, biochemical and yield characteristics of J. sambac. The treatment combination P₁M₃ consistently demonstrated higher relative water content, chlorophyll levels, total phenols, soluble proteins and the number of cymes per plant, reflecting enhanced plant vigour and metabolic efficiency. Therefore, implementing early pruning alongside balanced micronutrient nutrition is advisable for optimizing growth, physiological performance, and flower production in jasmine.

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