Enhancing germination and seedling growth of jamun (Syzygium cumini L.) through pre‑sowing growth regulator treatments

Dormancy releasing factors only control whether seeds can germinate in the specific climacteric conditions. Seeds quickly lose its viability hence it should be sown immediately after the harvesting of fruits 2-3 weeks when stored at 25-30 °C Uttamrao et al. (2022) [3] . Singh et al. (2019) [7] reported that jamun seeds are recalcitrant in nature. The hard seed coat imposes physical dormancy which delays germination under optimal condition 24-61 days. Even though Many researchers have made significant attempts to improve Jamun seed germination Bareke et al. (2018) [1] . Whereas pre-sowing of different treatments using different combinations which are not existing by using different combinations with dormancy breaking seed germination process can be accelerated. This study aims to determine the best dormancy breaking method simultaneously maintaining viability. It also helps in healthy seedlings production intern leads to a year-round supply of quality planting material to local farmers as well as researchers.

Materials and Methods

This research was carried out in the Shade Net facility, North Farm, under the Division of Horticulture at Karunya Institute of Technology and Sciences' School of Agricultural Sciences in Coimbatore during 2025-2026. Seeds required for this experiment were collected in and around Karunya Nagar from the healthy tress. The Seeds were collected from healthy Jamun (Syzygium cumini) trees at medium aged trees (20-40 years old) and fruits were harvested during peak season (typically June-July in Tamil Nadu), ensuring optimal seed maturity followed by a floatation test in distilled water where sinking seeds (viable) were selected and floating seeds (non-viable) were discarded. Freshly extracted seeds were then subjected to different treatments and three replication with complete randomized block design viz., T 1 -control (distilled water); T 2 -hydropriming (12 h); T 3 -scarification (sandpaper); T 4 -hot water (100 °C, 5 s); T 5 -GA 3 (250 mg L⁻¹, 10 min); T 6 -KNO 3 (0.5%, 10 min); T 7thiourea (500 mg L⁻¹, 10 min); T 8 -scarification + GA 3 (250 mg L⁻¹); T 9 -KNO 3 (0.5%) + GA 3 (250 mg L⁻¹); T 10 -thiourea (500 mg L⁻¹) + GA 3 (250 mg L⁻¹). Treated seeds were sown during last week of September in polythene bags of size 4" x 6" filled with potting mixture of vermicompost, soil, sand, and cocopeat in 2:1:1:1 ratio. Watering was done immediately after sowing and at regular intervals of (1-2 days). Observations were recorded at 30, 45, and 60 days after sowing (DAS). From the first day onwards, days to first germination and days to 50% germination were assessed; seedling height (from base to tip, measured with a ruler and expressed in cm), root length (from seed to primary root tip, measured with a ruler and expressed in cm), number of leaves (averaged and expressed as numbers), fresh weight of roots and shoots (five plants per replication, weighed separately and expressed in grams), and dry weight of roots and shoots (five plants per replication, dried in a hot air oven at 60 °C for 1 hour and expressed in grams) were recorded.

Results and Discussion

Seedling Height

The treatment T 9 (GA₃ + KNO₃) significantly enhanced plant height in comparison to control (T 1 ), recorded the highest values of 22.13 cm at 30 days, 28.94 cm at 45 days and 38.73 cm at 60 days, while T 1 gives the minimum values of 10.93 cm, 14.92 cm, and 19.87 cm at the respective intervals. This increase may be assign to GA₃ inducing α-amylase activity for starch hydrolysis, thereby mobilizing stored reserves, while KNO₃ supplies nitrogen for protein synthesis and activates nitric oxide signalling that loosens cell walls, promoting cell expansion and shoot elongation. Such synergistic action enhances dormancy relief and shoot growth resulting in taller seedlings. These findings are in line with Patil et al. (2018) [5] who reported the highest plant height of (41.37 cm) and the lowest of (27.43 cm) under their respective treatments.

Root Length

Root length was significantly he treatment T 9 (GA₃ + KNO₃), which recorded the highest values of 23.36 cm at 30 days, 31.29 cm at 45 days, and 41.16 cm at 60 days, while the control T 1 yielded the minimum values of 13.39 cm, 17.22 cm, and 22.28 cm at the respective intervals. This improvement can be attributed to GA₃ enhancing root meristem activity by degrading DELLA repressors, thereby sustaining cell divisi on in the root apical meristem, while KNO₃ supplies nitrate that supports primary root elongation, auxin biosynthesis, and gravitropic signalling. This interaction promotes stronger geotropic bending and greater lateral root formation, resulting in longer and more profuse root systems. Sonkar et al. (2025) [9] similarly documented the maximum root length (35.42 cm) and the minimum (19.99 cm) across their treatments, showing the growthpromoting effects of GA₃-based applications on root development.

Number of leaves

Treatment T 9 (GA₃ + KNO₃) significantly enhanced the number of leaves in comparison to the control (T 1 ), Which records the highest values of 13.42 at 30 DAS, 20.26 at 45 DAS, and 23.81 at 60 DAS, while T 1 showed the minimum values of 6.51, 10.61, and 14.71 at the respective interval among all seed treatments. This is due be to GA₃ promoting the initiation and development of leaf primordia initiation and expansion, while KNO₃ improves nitrogen availability and enhances chlorophyll synthesis and leaf production. Uttamrao et al. (2022) [3] similarly reported the highest number of leaves (10.6) and the lowest of (8.4) under their respective treatments.

Root Fresh Weight and Dry weight

Root fresh and dry weight were recorded at 30,45 and 60 days after sowing (DAS), with the GA₃ + KNO₃ (T 9 ) treatment producing the highest root fresh weight and dry weight values of 0.994 g and 0.095 g at 30 DAS, 1.386 g and 0.135 g at 45 DAS, and 1.98 g and 0.189 g at 60 DAS, respectively. In contrast, the control (T 1 ) recorded the lowest values of 0.318 g and 0.028 g at 30 DAS, 0.434 g and 0.042 g at 45 DAS, and 0.62 g and 0.058 g at 60 DAS among all seed treatments. This improvement can be due to GA₃ stimulating root meristem activity and cell division, whereas KNO₃ enhances nitrogen nutrition and metabolic processes which promots greater root biomass accumulation and better nutrient uptake. Whereas the combined effect led to increase cellular expansion, root elongation, and more efficient translocation of assimilates to the root system, resulting in higher fresh and dry weights. Bordoloi et al. (2025) [2] has found similar trends where one treatment gave the highest

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