Effect of seed treatment on growth of royal palm seedlings [Roystonea regia (Kunth)]

Introduction

Arecaceae is a palm family that include 2400-2600 plant species. Palm have been bred for several generations being an integral part of human existence and adding a lot to the world economy. People living in tropical areas have been depended on palm species for their sustenance and source of income because the palms has been known to be useful for a diverse of commercial products such as food products, cosmetics, bio fuel etc. Functionality of many palm species is manifold integrated into the cultural and socioeconomic environment of many countries worldwide. Royal palm which is also known as Roystonea regia is a member of this family. Royal palm fruit is purplish in colour having only one seed. Generally, the fruit wall (pericarp) consists of the exocarp, mesocarp and endocarp. The endocarp or 'shell' may be thick and stoney (drupe) to thin, papery or fleshy (berry); in some taxa, it is undifferentiated (Corner, 1966; Uhl and Dransfield, 1987; Tomlinson, 1990) [1,9,8] . Seed dormancy in most of the palm species may be due to seeds contain immature embryos or small embryos and covering layers or integuments restricting water inhibition or hard seed coat or gas presence penetrability or leaching of inhibition of growth regulators etc. in general palm seeds do not imbibe sufficient moisture for germination due to nature of hard seed coat which impermeable to water generally palm seeds do not imbibe sufficient moisture for germination. Hard seed coats are reason for causing impermeable to water. (Ingole et al., 2020) [4] .

Materials and Methods

The experiment was conducted at the Flower and Ornamental Nursery, College of Horticulture, Anand Agricultural University, Anand. Seeds were collected from palms of the same age and growth stage and then uniformly sown in seed bags. The experiment was done by using eleven seed treatments viz., T 1: control T 2: Scarification 3 min 30 second, T 3: GA 3 1000 ppm for 2 days, T 4: GA 3 1500 ppm for 2 days, T 5: Bio-NP 10 ml for 2 days, T 6: Bio-NP 20 ml for 2 days, T 7: Cow urine 50% for 2 days, T 8: Bijamrut for 2 days, T 9: H 2 SO 4 10% for 5 minutes, T 10: Scarification + GA 3 1000 ppm for 2 days, T 11: Scarification + Bio-NP 10 ml for 2 days.

Results and Discussion

Effect of seed treatment on plant height of royal palm seedlings The data about the impact of seed treatment on plant height in royal palm is shown in Table 1. Observation of plant height was taken at 120 and 150 DAS. Significant difference in plant height was observed at 120 and 150 DAS in royal palm seedlings. The significantly highest plant height was reported in seeds treated with T 4 GA 3 1500 ppm (31.93 cm and 39.91 cm) at 120 and 150 DAS respectively, which was at par with seeds treated with T 10 scarification and GA 3 1000 ppm and T 2 scarification. In contrast seeds treated with T 1 control produced the reduced plant height (13.40 cm and 17.97 cm) at 120 and 150 DAS respectively. The reason for the rise in seedling height following GA 3 treatment was that the hormone enhanced osmotic uptake of nutrients, which led to cell elongation and multiplication in the cambium tissue of internodal region, thus increasing the plant height (Shanmugavelu, 1970) [7] .

Effect of seed treatment on width of leaves of royal palm seedlings

Table 1 presents a comprehensive analysis of the effects of different seed treatment methods on leaf width. Leaf width was measured twice at 120 and 150 days after sowing (DAS). A significant variation in leaf width was observed at both the times. The highest leaf widths were recorded (1.510 cm and 1.70 cm) under treatment T 4 GA₃ at 1500 ppm at 120 DAS and 150 DAS respectively. It was statistically at par with T 10 scarification and GA₃ at 1000 ppm and T 2 scarification, indicating their comparable effectiveness in promoting leaf expansion. In contrast the lowest leaf widths (0.780 cm and 1.19 cm) were observed in the seeds kept as control treatment T 1 at 120 and 150 DAS respectively. The increase in leaf width was attributed to the stimulatory effect of GA₃ on cell elongation and expansion, which contributes to a larger photosynthetic surface area. Consistent results were also reported by Rani and Singh (2013) [6] in tuberose seed treated with GA₃ at 150 ppm resulted in the maximum leaf width. [3] . It was demonstrated that treatment GA 3 1500 ppm produced the highest number of roots per plant and was determined to be markedly more successful than all other treatments in the study. By enhancing auxin sensitivity and lateral root development, GA 3 increases surface area available for nutrition and water intake. Higher number of leaves in GA 3 treated seeds might be due to presence of GA 3 may have increased the number of leaves because its action to produces more nucleoprotein, which increases leaf initiation and expansion.

Effect of seed treatment on number of leaves of royal palm seedlings

Effect of seed treatment on Fresh weight of royal palm seedlings

Table 2 presents the results regarding the impact of seed treatment on the fresh weight of royal palm. Fresh weight of the plants was recorded at 150 days after sowing (DAS). At the end of the study period, a significant variation in fresh weight was observed among all the treatments. The maximum fresh weight (3.708 g) at 150 DAS was recorded in treatment T 4 GA₃ 1500 ppm, which was statistically at par with treatment T 10 scarification and GA₃ 1000 ppm, indicating their effectiveness in promoting vegetative growth. In contrast, the minimum fresh weight (0.677 g) at 150 DAS was observed in the control treatment T 1 . Similar findings were reported in royal palm by Ingole et al.

(2021) [3] , who observed that treatment with GA₃ at 1500 ppm resulted in the highest fresh plant weight, significantly outperforming all other treatments evaluated in the study.

The enhanced fresh weight was attributed to the role of GA₃ in promoting biomass accumulation through improved photosynthetic efficiency and increased water uptake, ultimately contributing to vigorous plant growth.

Effect of seed treatment on dry weight of royal palm seedlings

Table 2 presents the data illustrating the effect of different seed treatments on the dry weight of royal palm at 150 DAS. A significant variation in dry weight was observed among seeds treated with various treatments in royal palm. The highest dry weight (0.943 g) was recorded in treatment T 4 GA₃ at 1500 ppm, which was statistically at par with T 10 scarification and GA₃ at 1000 ppm, indicating their effectiveness in enhancing biomass accumulation. In contrast, the lowest dry weight (0.256 g) was observed in the seeds kept in control treatment, highlighting the beneficial role of seed treatment in promoting dry matter production.

Biomass accumulation in plants is the net outcome of the dynamic interaction between various anabolic and catabolic processes. Among plant growth regulators, gibberellic acid (GA₃) has demonstrated a significant influence on the accumulation of dry matter across different plant organs. This effect can be attributed to the ability of GA₃ to stimulate key physiological processes, including cell division, cell elongation, enhanced auxin metabolism, increased cell wall plasticity and improved cell membrane permeability. Collective effect of these mechanisms might have contribute to enhanced vegetative growth and higher dry matter production in seeds treated with GA 3 (1500 ppm).

Effect of seed treatment on root-shoot ratio of royal palm seedlings

Data were recorded at 150 days after sowing (DAS). A significant variation in the root-shoot ratio was observed among the treatments at the conclusion of the study. The lowest root-shoot ratio (0.62 g) was recorded under treatment T 4 GA₃ at 1500 ppm, which was statistically the lowest and found to be at par with treatments T 10 scarification and GA₃ at 1000 ppm, T 3 GA₃ at 1000 ppm, T 11 scarification and Bio NP 10 ml, T 6 Bio NP at 20 ml and T 5 Bio NP at 20 ml. In contrast, the highest root-shoot ratio (0.88 g) was recorded in the control treatment T 1 , indicating the influence of seed treatments in modulating the allocation of biomass between root and shoot components. Gibberellic acid (GA₃) seed treatment often results in a reduced root-to-shoot ratio in royal palm (Roystonea regia) due to its targeted influence on shoot growth in initial stage of seedling growth. GA₃ is a plant hormone known to significantly promote cell elongation, particularly in the stems and leaves, thereby enhancing shoot development at a faster rate than root growth (Hedden & Thomas, 2012) [2] . This differential stimulation leads to a greater allocation of biomass to the aerial parts of the plant, consequently lowering the root-to-shoot ratio.

Effect of seed treatment on seedling vigour index of royal palm seedlings

Table 2 presents the data on the effect of various seed treatments on the seedling vigour index of royal palm. Seedling vigour index was assessed at 150 days after sowing (DAS) to evaluate the influence of seed treatments on early seedling performance in royal palm. At the conclusion of the study, significant differences in seedling vigour index were observed among the treatments. The highest seedling vigour index (5478.19) was recorded in treatment T 4 GA₃ at 1500 ppm, which was markedly superior to all other treatments, indicating its effectiveness in promoting robust seedling growth. In contrast, the lowest seedling vigour index (1712.45) was observed in the control treatment T 1 , underscoring the beneficial impact of GA₃ application on seedling vigour. The enhanced seedling vigour observed with GA₃ treatment can be attributed to several physiological and biochemical mechanisms. GA₃ promotes the development of larger embryos, accelerates respiration rates and enhances overall metabolic activity. This leads to improved mobilization and utilization of stored metabolites to active growth sites. Additionally, increased enzyme activity stimulated by GA₃ facilitates key metabolic processes such as oxidative reactions, protein hydrolysis and sugar mobilization, all of which contribute to vigorous seedling growth (Puls and Lambeth, 1974) [5] . These hormonal and enzymatic mechanisms collectively support the superior seedling vigour index observed in GA₃ treated.

Conclusion

The present investigation concluded that gibberellic acid enhanced the growth of royal palm seedlings. Seed treated with gibberellic acid 1500 ppm for 2 days provide healthier seedling growth attributed to higher plant height, number of leaves, width of leaves, root length, number of rootlets and biomass of plant.

References

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