Effect of nano-silicon priming on germination dynamics, morpho-physiological changes, osmotic adjustment and yield responses of late sown Indian mustard (Brassica juncea L.) var. Kesari Gold and TBM-143

In the vast fields of India, mustard is more than just a crop; it is a cornerstone of the nation's food security, providing the oil that cooks millions of meals daily. Yet, this vital plant faces a persistent enemy: the calendar. When farmers are forced to plant their seeds later than the ideal time, the crop struggles to establish itself, often facing a harsh, hot finish to its growing season that stunts its growth and shrinks the harvest. This delay creates a physiological bottleneck, where the seeds take longer to wake up, the young shoots grow weak, and the plant's internal machinery for fighting stress fails to fire on all cylinders. For decades, scientists have searched for a way to give these late-planted crops a head start, looking for a method to toughen the seed before it even touches the soil.

Enter a new tool from the world of nanotechnology: silicon dioxide nanoparticles. While silicon is a common element found in sand and soil, in its microscopic, nano-sized form, it behaves differently. These tiny particles are small enough to penetrate the hard outer shell of a seed, acting like a microscopic key that unlocks the seed's potential. They do not feed the plant in the traditional sense but rather act as a regulator, helping the seedling grow stronger roots, build better defenses against heat, and convert sunlight into energy more efficiently. The question researchers asked was simple yet critical: could soaking mustard seeds in a solution of these tiny particles help them survive and thrive even when the planting season has been pushed too late?

To find the answer, a team of scientists at Visva-Bharati University in India set up a rigorous experiment during the winter of 2024 and 2025. They chose two popular varieties of Indian mustard, known locally as Kesari Gold and TBM-143, and subjected them to a series of treatments. The researchers prepared a suspension of silicon dioxide nanoparticles in water, creating five different concentrations ranging from a plain water control to solutions containing up to 100 milligrams of particles per liter. They took healthy, uniform seeds of both varieties and soaked them in these solutions for five hours, a process known as priming, before letting them dry. This was not just a laboratory exercise; the seeds were then planted in a research farm in Sriniketan, a region with a sub-humid tropical climate, to see how they would perform under real-world conditions where the sowing date was deliberately delayed to mimic the stress farmers often face.

The results were striking and consistent. The seeds that had been primed with the nanoparticles woke up faster and more reliably than those soaked in plain water. In the control group, where seeds received no special treatment, germination was delayed and less uniform. However, the nano-primed seeds, particularly those treated with concentrations between 25 and 50 milligrams per liter, burst forth with greater speed. The variety Kesari Gold showed a remarkable response, achieving a germination rate of nearly 93 percent, while the TBM-143 variety reached about 88 percent. More importantly, the time it took for the seeds to sprout was significantly reduced, meaning the field was covered with green shoots sooner, a crucial advantage when the growing season is short.

As the seedlings grew, the benefits of the nano-priming became even more visible. The plants treated with the silicon solution developed longer roots and taller shoots compared to their unprimed counterparts. The roots, which are the plant's anchor and water-gathering system, were not only longer but also occupied more volume in the soil, suggesting a more robust ability to hold onto nutrients and moisture. The shoots grew taller and carried more leaf mass, indicating that the plants were building a stronger structure to support future growth. The variety Kesari Gold consistently outperformed TBM-143 in almost every measure of growth, producing taller plants with larger leaves and heavier biomass, but both varieties showed a clear improvement over the untreated controls.

Inside the leaves, the chemical changes were just as significant. The nano-primed plants accumulated higher levels of chlorophyll, the green pigment responsible for capturing sunlight. This meant the plants were more efficient at photosynthesis, turning light into the energy needed to grow. Furthermore, the plants showed a heightened ability to manage stress. They produced more proline, a natural compound that acts like a protective shield for cells, helping them retain water and withstand the heat of a late-season sun. They also increased their stores of sugars and phenolic compounds, which serve as antioxidants to neutralize the damaging effects of heat stress. These internal adjustments allowed the plants to maintain their vigor even when the weather turned against them.

The ultimate test, however, was the harvest. The researchers measured the final yield by counting the number of seed pods, known as siliquae, and weighing the seeds they produced. The plants that had been primed with the nanoparticles produced significantly more siliquae per plant, and these pods were longer and contained more seeds than those from the untreated plants. The variety Kesari Gold, when treated with the optimal concentration of nanoparticles, produced a total yield of nearly 786 kilograms per hectare, a substantial increase over the control group. Even the TBM-143 variety saw a marked improvement, though it did not reach the same heights as Kesari Gold. The test weight, a measure of seed quality and density, also improved, indicating that the seeds were not only more numerous but also heavier and of better quality.

The study concluded that soaking mustard seeds in a solution of silicon dioxide nanoparticles is a practical and effective way to mitigate the damage caused by late sowing. It is a technique that does not require complex machinery or expensive inputs, making it accessible to farmers who might otherwise lose their crop to a delayed planting schedule. By simply treating the seeds before they are planted, farmers can help the crop establish itself more quickly, grow stronger, and withstand the heat stress that typically plagues late-season mustard. While the yield under these late conditions did not match what would be achieved with perfect, early planting, the significant gains in stress tolerance and productivity suggest that this method offers a reliable safety net. It bridges the gap between the ideal and the inevitable, offering a way to secure the harvest even when the calendar does not cooperate.