Physiological responses and flowering attributes of Goldenrod (Solidago canadensis L.) under different bio-stimulants

Introduction

Goldenrod (Solidago canadensis L.), belonging to the family Asteraceae, is an important ornamental cut foliage crop valued for its attractive golden yellow flower spikes, excellent filler value in floral arrangements and long vase life (Patil et al., 1997) [12] . Owing to its adaptability, ease of cultivation and increasing market demand, it is widely grown for the cut flower industry. Besides its commercial importance, Goldenrod is an excellent landscape plant and serves as a rich source of nectar and pollen, attracting honey bees, butterflies and other beneficial pollinators (Moron et al., 2019) [10] . In recent years, bio-stimulants have gained importance as eco-friendly inputs that enhance nutrient uptake, plant growth, flowering, quality and yield while improving tolerance to abiotic stress (Traon et al., 2014) [23] . However, information on the comparative performance of different bio-stimulants in Goldenrod is limited. Therefore, the present investigation was carried out to study the effect of bio-stimulants on the growth and flowering of Goldenrod. at 30, 60 and 90 days after transplanting (DAT). Standard cultural practices were followed throughout the crop period. Observations were recorded from five randomly selected and tagged plants for growth parameters viz., plant height, number of leaves per plant, leaf area per plant, leaf area index, plant spread (E-W and N-S directions), number of branches per plant, number of suckers per plant, stem girth, internodal length and flowering parameters viz., days taken for flower bud initiation, first flower opening, 50 per cent flowering and flower stalk harvesting.

Results and Discussion

The findings of the present investigation were interpreted and are presented in Tables 1 and2 based on the observations recorded during the study. A. Growth parameters Significant variation was observed in the growth parameters of Goldenrod under different bio-stimulant treatments. The maximum plant height (101.70 cm), number of leaves per plant (138.33), leaf area (4975.50 cm²), leaf area index (5.53), plant spread in east-west (38.67 cm) and north-south (34.50 cm) directions, number of branches per plant (20.17), number of suckers per plant (20.33), stem girth (8.37 mm) and internodal length (4.62 cm) were recorded in the treatment T7 (Samras @ 0.3%). The superior growth performance under Samras @ 0.3 per cent may be attributed to the presence of free amino acids and bioactive peptides, which enhance nutrient uptake, nitrogen metabolism, protein synthesis, enzymatic activity and endogenous phytohormone activity, thereby promoting cell division, cell elongation, chlorophyll biosynthesis, photosynthetic efficiency and assimilate production. These physiological responses collectively favour leaf initiation and expansion, canopy development, lateral shoot and sucker formation, stem thickening and internode elongation, resulting in vigorous vegetative growth. These results are in confirmity with Rakesh (2022) [17] in Goldenrod, Harish et al. (2019) [3] and Manasa et al. (2017) [8] in Gladiolus, Taih et al. (2023) [22] in Pot marigold, Bhargavi et al. (2018) [1] , Suchitha et al. (2021) [21] and Sainath et al. (2014) [18] in Chrysanthemum, Hegde et al. (2021) [5] in Dendrobium orchid, Ragini et al. (2019) [16] in Asiatic lily, Praveen et al. (2021) [14] in Floribunda rose, Shukla et al. (2023) [20] in Dahlia, Kumar et al. (2015) [7] and Munikrishnappa and Chandrashekar (2014) [11] in China aster and Patra et al. (2015) [13] in Gerbera.

B. Flowering parameters

The flowering behaviour of Goldenrod was significantly influenced by the application of different bio-stimulant treatments. The treatment T 7 (Samras @ 0.3%) recorded the minimum days taken for flower bud initiation (59.07), first flowering (70.10), 50 per cent flowering (81.00) and flower stalk harvesting (102.37), indicating its effectiveness in promoting early flowering. The earliness in flowering under Samras @ 0.3 per cent may be attributed to the presence of free amino acids and bioactive peptides, which enhance physiological and biochemical processes, improve nutrient assimilation and promote the transition from vegetative to reproductive growth. The bio-stimulant may also enhance endogenous phytohormone activity and efficient translocation of photosynthates towards developing floral buds, thereby promoting early floral differentiation, flower opening and stalk maturity. These results are in conformity with Rakesh (2022) [17] and Youssef et al. (2022) [24] in Goldenrod, Munikrishnappa and Chandrashekar (2014) [11] in China aster, Memon et al. (2014) [9] and Khan et al.

(2020) [6] in Zinnia, Hasan (2019) [4] in Pot marigold, Salem et al. (2016) [19] in Gerbera, Pruthvi et al. (2017) [15] and Suchitha et al. (2021) [21] in Chrysanthemum, Chaithra et al.

(2020) [2] in Spider lily and Hegde et al. (2021) [5] in Dendrobium orchid.

Conclusion

The present investigation revealed that foliar application of bio-stimulants significantly improved the growth and flowering performance of Goldenrod. Among the treatments, Samras @ 0.3 per cent (T 7 ) recorded superior growth and the earliest flowering compared to other treatments. Hence, the treatment (Samras @ 0.3%) applied at 30, 60 and 90 DAT can be recommended for commercial cultivation of Goldenrod and offers an effective and sustainable approach for enhancing crop growth and flowering performance.

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