Delayed seed germination and inhibited shoot emergence in glutinous corn (Zea mays L.) due to induced drought stress

In the fields of the Philippines, corn is more than just a crop; it is a lifeline for farmers who rely on it for food, livestock feed, and income. Often planted after the rice harvest, corn faces a critical challenge: the dry season. When the soil lacks sufficient moisture, the seeds struggle to wake up from their dormant state. This lack of water slows down the internal chemical processes that allow a seed to sprout, often delaying the emergence of the tiny root and shoot that must push through the earth. If the seed cannot establish itself quickly, the entire crop suffers, leaving farmers with poor harvests. To combat this, scientists have long looked for ways to give seeds a head start. One such method is seed priming, a technique where seeds are soaked in water or a specific solution for a set time before planting. This process wakes up the seed's internal machinery without letting it fully sprout, so that when it is finally planted, it can grow faster and stronger, even if the soil is dry.

Researchers at Mariano Marcos State University recently put this idea to the test with glutinous corn, a specific variety popular in the region. They wanted to see if soaking the seeds in water or a mild salt solution could help them survive a simulated drought. The team took healthy, uniform seeds and divided them into groups. Some were left dry as a control, while others were soaked in plain water, a method known as hydropriming. Another group was soaked in a solution of potassium nitrate, a chemical compound often used to help plants grow. Each group was soaked for different lengths of time: eight hours, twelve hours, and twenty-four hours. After soaking, the seeds were dried back to their original state and then planted in boxes. To mimic a drought, some boxes were treated with a substance that made the water in the soil difficult for the seeds to absorb, creating a low-water environment, while other boxes received normal water to serve as a comparison.

The results revealed a clear picture of how these seeds react to stress and how priming can help. When the seeds faced the dry conditions, they took longer to germinate than those in the wet boxes, regardless of whether they had been soaked beforehand. The drought stress slowed everything down, delaying the moment the seedlings broke through the surface. However, the soaking treatments did make a difference in the quality of the seeds that did manage to grow. The primed seeds were better at surviving the dry spell than the unsoaked ones, showing that the pre-treatment helped them cope with the lack of water. Interestingly, while the soaking helped the seeds get started, it did not speed up the germination process itself under drought conditions; the seeds still took longer to sprout than they would have in ideal conditions.

The most significant findings appeared in how the young plants grew after they emerged. The dry conditions stunted the growth of the shoots, the green parts that reach for the sky. In the wet conditions, soaking the seeds for eight hours in the potassium nitrate solution produced the longest shoots. But when the water was scarce, the shoots remained short no matter what treatment was used. The story was different for the roots. In the wet environment, soaking the seeds in plain water for twelve hours produced the longest roots. However, under the stress of drought, the roots of most seeds were shorter and fewer in number. There was one standout exception: seeds soaked in the potassium nitrate solution for just eight hours managed to grow longer roots than any other group, even in the dry soil. This suggests that this specific treatment helped the plant reach deeper for the limited water available.

The researchers also counted how many small side-roots the seedlings produced. In normal conditions, the soaked seeds grew many more side-roots than the dry ones, creating a dense network to gather nutrients. But in the dry boxes, the number of these roots dropped dramatically, and the soaking treatments could not fully prevent this loss. Despite this, the overall health of the seedlings was better in the primed groups. The team measured a "vigor index," a way to combine how well the seeds germinated with how big and heavy the resulting plants were. The seeds soaked in plain water for twelve hours produced the most vigorous seedlings in normal conditions, showing strong growth in both length and weight. In the dry conditions, the eight-hour potassium nitrate soak helped produce the longest roots, while a twelve-hour soak in either water or the salt solution resulted in the strongest overall seedlings.

The study concludes that while drought stress inevitably slows down corn germination and limits growth, seed priming offers a practical way to improve the outcome. Farmers do not need to choose between complex chemicals and simple water; both methods showed promise. The potassium nitrate soak was particularly effective at helping roots grow longer when water was scarce, while the plain water soak was excellent for producing strong, vigorous seedlings in general. Given that plain water is free and readily available, the researchers suggest that hydropriming is the most practical option for farmers. By simply soaking the seeds for the right amount of time, growers can give their corn a better chance to establish itself and survive the dry spells that threaten their harvests.