Rubber is one of Indonesia's most valuable plantation commodities, supporting millions of livelihoods and supplying raw materials for the automotive, manufacturing, and medical industries. Despite its economic importance, producing high-quality rubber seedlings remains a challenge because the seeds often germinate slowly and unevenly. The hard outer seed coat restricts the movement of water and oxygen into the embryo, delaying germination and reducing nursery efficiency.
Improving germination is increasingly important as demand for rubber planting materials continues to grow. Faster and more uniform seedling emergence enables nurseries to produce healthy planting stock more efficiently, helping farmers establish productive plantations while reducing production delays.
A Simple Chemical Treatment Tested Under Controlled Conditions
The research team carried out the experiment at the Seed Technology Laboratory of Universitas Methodist Indonesia in Medan. They evaluated how different concentrations of sulfuric acid and varying soaking durations affected the germination performance of rubber seeds.
The experiment followed a factorial Completely Randomized Design using:
- Three sulfuric acid concentrations: 1%, 2%, and 3%
- Three soaking durations: 10, 15, and 20 minutes
- Nine treatment combinations
- 450 carefully selected rubber seeds distributed across 90 experimental units
Researchers measured three primary indicators of seed performance:
- Germination percentage
- Germination time
- Number of normal seedlings
The data were analyzed statistically using Analysis of Variance (ANOVA), followed by Duncan's Multiple Range Test to determine significant differences among treatments.
Higher Sulfuric Acid Concentration Produced Better Germination
The results consistently demonstrated that both sulfuric acid concentration and soaking duration significantly influenced rubber seed germination. The interaction between these two factors also played a critical role in determining seed performance.
Among all treatments, the combination of 3% H₂SO₄ and 20 minutes of soaking produced the best overall performance.
Key findings include:
- The highest germination percentage was achieved with the 3% sulfuric acid treatment combined with longer soaking periods.
- The fastest germination time occurred when seeds were soaked in 3% sulfuric acid for 20 minutes.
- The greatest number of normal seedlings was also recorded under the same treatment combination.
- Longer soaking periods generally improved seed performance across all sulfuric acid concentrations.
The researchers explained that sulfuric acid softens the hard seed coat, allowing water and oxygen to penetrate more easily. This process accelerates imbibition the initial absorption of water and activates enzymes responsible for converting stored nutrients into energy for embryo growth. As a result, roots and shoots emerge sooner, leading to faster and more uniform seedling development.
Unlike stronger chemical treatments reported in some previous studies, the relatively low concentration of 3% H₂SO₄ was sufficient to improve germination without causing significant damage to the developing embryo. This balance between effectiveness and safety makes the treatment particularly attractive for practical nursery operations.
Why the Findings Matter
Efficient seed germination is essential for commercial rubber production. Delayed or uneven germination increases labor costs, prolongs nursery management, and reduces the availability of uniform planting materials.
The findings suggest that a carefully controlled sulfuric acid treatment can help overcome these limitations by:
- Producing seedlings more quickly
- Improving germination uniformity
- Increasing the number of healthy seedlings
- Enhancing nursery productivity
- Supporting more efficient large-scale rubber propagation
These benefits may ultimately contribute to higher plantation productivity and more reliable supplies of quality planting materials for Indonesia's rubber sector.
Beyond rubber cultivation, the research also provides useful insights for other crops with hard-coated seeds that experience physical dormancy. Similar scarification techniques could potentially improve propagation in a range of economically important plant species.
Authors Recommend Careful Application
The researchers emphasize that the treatment should be applied carefully because excessive sulfuric acid concentrations or prolonged soaking periods may damage seed embryos and reduce germination quality.
As Saragih, Panataria, Sinambela, and Sitorus of Universitas Methodist Indonesia conclude, chemical scarification using sulfuric acid effectively weakens the seed coat, enhances water absorption, activates embryo metabolism, and significantly improves rubber seed germination when applied at the appropriate concentration and soaking duration. They recommend further studies exploring additional acid concentrations, soaking periods, and combinations with physical or biological scarification methods to develop even safer and more scalable nursery practices.
Author Profiles
Meylin Kristina Saragih is a researcher in the Department of Agriculture at Universitas Methodist Indonesia, with research interests in seed technology and crop production.
Lince Romauli Panataria, M.P. is a lecturer and researcher in the Department of Agriculture at Universitas Methodist Indonesia, specializing in agronomy, seed science, crop cultivation, and nursery technology.
Anre Meyksen Sinambela is a researcher in the Department of Agriculture at Universitas Methodist Indonesia, focusing on crop production and agricultural technology.
Efbertias Sitorus is a researcher in the Department of Agriculture at Universitas Methodist Indonesia, whose work centers on agricultural science and plant propagation.
Source
Article Title: Effect of H₂SO₄ Concentration and Seed Soaking Time on Breaking Dormancy of Rubber Seeds (Hevea brasiliensis Muell. Arg.)
Authors: Meylin Kristina Saragih, Lince Romauli Panataria, Anre Meyksen Sinambela, Efbertias Sitorus
Journal: Formosa Journal of Science and Technology (FJST)
Publication Year: 2026
DOI: https://doi.org/10.55927/fjst.v5i7.105
Official Journal: https://journalfjst.my.id/index.php/fjst
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