Effect of Nitric Oxide on Seed Dormancy

A state of a plant where it stops growing further due to unfavourable conditions is known as seed dormancy. Seed dormancy breaks if we use various methods like providing favourable conditions. Chemical compounds like nitric oxide can induce dormancy. These compounds break dormancy and induce seed germination. In this article, we will learn how to break seed dormancy and induce seed germination. 

What Is Seed Dormancy? 

Dormancy occurs when seeds or tubers fail to germinate despite the presence of the necessary conditions (temperature, moisture, oxygen, and light). Impermeability of the hard seed coat or a lack of supply and activity of enzymes required for germination (internal dormancy) can boost dormancy. It also stops the production of many field crops. Organic material (seeds/tubers) is subjected to several physical and chemical pre-treatments to overcome dormancy.

Seed Dormancy Patterns

There are two types of seed dormancy:

• Natural dormancy

It is the condition of seeds in which they cannot germinate even when ideal conditions for seedling growth are met. In some species, this inability to germinate may be due to the embryo being underdeveloped at dissipation.

• Imposed Dormancy

It is an ailment of seeds in which the seeds cannot germinate due to environmental constraints such as insufficient moisture, oxygen, light, and temperature.

• Induced Dormancy

This form of seed dormancy occurs whenever a seed has consumed water but is located in remarkably undesirable germinating seed circumstances. The seed fails to germinate even under more optimal circumstances.

Things That Can Prevent Dormancy

Some seeds that are dormant when harvested become productive after some time naturally. On the other hand, a few species initiate some pre-treatment. For specific genera, several methods are used.

1. Breaking Seed-Coat Dormancy

• Piercing, chipping, filing and nicking the seed coat with a knife, needle, or sandpaper is the preferred method of overcoming seed dormancy. 

• Manual scarification is efficient at any juncture on the seed coat, but the micropylar area should be prevented because it is the most vulnerable area of the seed and contains the radicle.

• If seed-covering prevents embryo growth, eliminate them to enable germination.

• The seed coat may contain inhibiting substances that delay or stop the germination; these substances can be drawn out by immersing the seed in a significant amount of water that is filled every six to twelve hours or by putting the seed under the tap or water for several hours. 

• The International Seed Testing Association recommends sacrificing the seed coat with the help of concentrated sulphuric acid for 2-45 minutes. But the usage of this method depends solely on the species. This technique, however, is expensive and risky and should be used with care.

• Place the seeds in 75°C water for 3 to 6 minutes to understand the waxy coating and allow imbibition. It is essential never to use high temperatures for extended periods of time or to boil the seeds.

2. Breaking Embryo Dormancy

You can break the dormancy of the embryo in several ways. These ways include pre-chilling for species found in cold temperate and high altitudes; this method is also called cold stratification. Another method is preheating species of low concentration using Gibberellic acid (GA₃) and adding potassium nitrate (KNO₃). 

• Pre-Chilling (cold stratification)

In this process, a moist substrate is taken, and the seed is placed upon it in a container. This seed is refrigerated for 3°-5° C. If the seed is too dormant, the treatment can be extended to 14 days. Once stratification is complete, the containers are transferred to incubators, and the seeds are allowed to germinate under the recommended conditions.

You can preheat the seeds for 7 days at a temperature of 40°C in the presence of air. 

• Gibberellic Acid

In this method, the test paper is soaked in Gibberellic acid (GA₃) with a concentration of 0.05 per cent. This solution is formed by dissolving 500 mg of GA₃ in 1 litre of water. After that, germination is continued under the suggested circumstances.

• Sodium Nitrate

The germination paper is kept moist when this experiment is started, and a 0.2 per cent solution of potassium nitrate (KNO₃) is prepared by dissolving 2 g KNO₃ in 1 litre of water. In the recommended conditions, germination continues.

Effect Of Nitric Oxide On Seed Dormancy

Nitric oxide is developed to decrease dormancy and encourage germination; it is a component that appears to be dependent on crosstalk with the ABA signalling network. Several independent studies conducted over the last two years have revealed that NO gates the ABA signalling network at multiple points, ensuring redundant and successfully irreversible control of plant growth.

Studies were conducted to inspect how compounds such as nitric oxide can reduce the dormancy of Arabidopsis thaliana. A simple method for transferring the results of SNP photolysis through the gaseous state was developed. 

Along with nitric oxide, SNP, as well as potassium ferricyanide and potassium ferricyanide, can decrease dormancy and induce seed germination. Nitrate and nitrite also help decrease Arabidopsis seed dormancy and increase germination rates significantly. 

Nitric oxide scavenger c-PTIO prevented the effects of CN, nitrite, and nitrate on dormancy. Using purified nitric oxide gas, it was demonstrated that nitric oxide plays a role in reducing seed dormancy. 

Conclusion

Seed dormancy is a mature seed property that prevents seed germination during unsuitable conditions. Several chemical methods can help to break this dormancy. One of these methods is spraying nitric oxide. This article explains ways that help in breaking dormancy and boosting seed germination.