Ultrasonic Priming of Seeds: How Sonication Improves Germination

Ultrasonic priming of seeds and grains result in a more complete and faster germination and higher crop yields. Ultrasonication perforates the seed testa (seed coating) and increases the uptake of water, nutrients and oxygen into the seed grains. The ultrasonic priming of seeds is a simple low-cost method to enhance germination rate and speed of seedlings.

Ultrasonically Improved Seed Germination

Priming is a pre-treatment method used to shorten the germination time of seedlings. Various seed priming processes such as osmotic priming, hydropriming and ultrasonic priming have been developed to induce the early germination processes to take place. Ultrasonic priming is a very advantageous method of seed preparation since the sonication treatment is fast, energy-saving and water-saving.
Primed seeds that have completed the first germination processes, show a higher germination percentage and an faster emergence time (the time it takes for seeds to rise above the surface of the soil), a higher emergence rate (the number of seeds that make it to the surface), and better growth, suggesting that the head-start helps them get a good root system down early and grow faster. This method can be useful to farmers because it saves them money, labour and time spent on fertilizers, re-seeding, and weak plants.
The process can also allow for more uniform, even germination of the treated seeds. It can also increase germination over a wider temperature range and reduce disease incidence in seeds.

Ultrasonic priming improves seed germination percentage, seed vigor index (SVI), root and shoot lengths of seedlings. The sonication and priming process enforces the uptake of water and/or other beneficial substances into a seed grain. Furthermore, the ultrasonic waves activate enzymatic and other biologic reactions in the plant cell resulting in a faster and more uniform germination. Even weak seeds/grains can be activated so that the overall yield of the sowing is improved.

Scarification and Seed Germination

Scarification is crucial for seeds with tough, impermeable coats that hinder water and gas exchange, thereby delaying germination. Traditional methods include mechanical, thermal, and chemical scarification, each designed to make the seed coat more permeable to water and gases. Sonication, as an innovative scarification method, leverages ultrasonic waves to achieve similar, if not superior, results.

Mechanisms of Power Ultrasound on Seeds and Seed Priming

• Cavitation in Water:
  – Ultrasonic waves in water induce cavitation, a phenomenon where micro-bubbles are created. These bubbles collapse, generating localized mechanical pressure.
  – This pressure acts on the seed coat, causing mechanical disruption.
• Formation of Micro-Pores and Micro-Cracks:
  – The mechanical pressure from cavitation creates micro-pores and micro-cracks on the seed coat.
  – These micro-pores and cracks increase the seed coat’s permeability, allowing more water and oxygen to penetrate.
• Enhanced Water Uptake and Oxygen Availability

  1. Increased Porosity:
  – Studies have shown that sonication increases the porosity of seeds, such as mung beans, making them more receptive to water and oxygen.
  – Enhanced water uptake leads to better hydration of the seed tissues, which is essential for activating metabolic processes necessary for germination.

  2. Improved Oxygen Entry:
  – The increased permeability to gases ensures that the developing embryo receives adequate oxygen, crucial for cellular respiration during germination.

• Boosted Enzymatic Activity

  1. Hydration and Enzyme Activation:
  – Enhanced hydration due to increased water uptake activates various enzymes involved in germination.
  – Specifically, alpha-amylase activity is significantly increased, which is pivotal for the hydrolysis of starch into sugars, providing energy for the growing seedling.

  Improved Germination Outcomes

  1. Higher Germination Percentage:
  – The combined effect of increased water and oxygen availability, along with boosted enzymatic activity, results in a higher percentage of seeds successfully germinating.
  – Research indicates that sonication improves the germination rates across various plant species.
  2. Faster Germination Speed:
  – Sonication not only increases the percentage of germinated seeds but also accelerates the germination process.
  – The quicker hydration and enzyme activation facilitate a faster transition from seed to seedling.

Sonication significantly benefits seed priming by enhancing water, oxygen and nutrient uptake, boosting enzymatic activities, and consequently improving both the speed and success rate of seed germination.

Longer sonication results in the better germination of the Calanthe hybrids. The longer the sonication, the faster was the sprouting. This indicates the positive effects of ultrasonication on seed germination.
(study and picture: ©Shin et al. 2011)

How Does Ultrasonic Seed Priming Work?

Ultrasonic priming of seeds and grains results in a more complete and faster germination. These results are achieved by the following ultrasonic effects:

• Ultrasonics increases the porosity of the seed by acoustic cavitation improving water uptake and oxygen availability (ultrasonic hydropriming / steeping).
• Ultrasonics increases the uptake of nutrients and fertilizer into the seeds.
• Ultrasonic priming enhances mass transfer: the extra-absorbed water reacts freely and readily with the cell embryo. Thereby, gibberellic acid is released and causes an increase in the rate of metabolic processes in aleurone cells.
• Sonication helps the mobilisation of endosperm nutrients by cell membrane disruption. (Miano et al. 2015)
• Ultrasonics activates enzymatic and other biologic reactions.

Sonication promotes grain/seed germination and increases the crop yield. Besides crops and fruit seedings, the ultrasonic seed priming has been successfully tested for flower seeds (orchids, lotus, calanthe), too. Ultrasonication enhances the permeability of the cell walls so that the seed shows a significantly higher uptake of water and nutrients (e.g. fertilizer).
It has been shown that the soaking time chickpeas, sorghum and navy beans was significantly reduced by the use of sonication.

Sonicated lentils (40Ws/g w/ UP200St) in comparison with non-sonicated lentils: The sonicated lentils show a higher gemination rate and longer shoots.

Ultrasonic Seed Priming Systems

Take advantage of Hielscher sonicators for enhanced seed priming! Hielscher Ultrasonics supplies various bench-top and industrial ultrasonicators for seed and grain priming. The advantages of using Hielscher sonicators for seed priming are manifold. Firstly, the precise control over ultrasonic parameters such as amplitude, intensity, and duration allows for optimized treatment tailored to specific seed types and conditions. Secondly, all process results achieved can be linearly scaled to larger throughputs.
Whether you are interested in testing and optimizing your ultrasonic priming process in the lab or want to process large seed lots in continuous throughput, Hielscher has the ideal sonicator for your seed processing requirements. Hielscher sonicators are designed for scalability and can handle large volumes of seeds efficiently, making them suitable for both research and commercial applications. The equipment is user-friendly, with intuitive controls and robust construction, ensuring long-term durability and low maintenance requirements. Additionally, sonication is a non-chemical method, which makes it an environmentally friendly option for seed treatment. It reduces the need for chemical scarification agents, contributing to sustainable agricultural practices. Of course, all sonicators can be run 24/7.

Advantages of Hielscher Sonicators for Seed Priming:

• Low Costs
• Water-Saving
• Fast Processing
• Low Energy Consumption
• Easy & Safe Operation

Contact us today! We will be glad to discuss your process requirements with you!