**1. Introduction**

Generally, the concept of dormancy is centered on the absence of growth in any plant organ having a meristem like bulbs, corms, axillary buds, seeds and even in other living organisms like fungi spore, spirogyra zygospore etc. In the discipline of seed biology, dormancy could be considered simply as a block to the completion of germination of an intact viable seed under favorable conditions. The process might look simple but several authors have reported that dormancy is one of the least understood phenomena in the field of seed biology and needs further elucidation [1, 2]. The resting condition of many seeds, especially those of different grasses and garden crops, is maintained only as long as the seeds are in dry storage. As soon as a suitable

moist medium and a favorable temperature are provided germination proceed almost immediately. Dormancy is a seed characteristic, manifesting as a block or series of blocks that prevent germination under otherwise favorable moisture, temperature and gaseous conditions. Dormancy is thus considered as an adaptive life history trait to seasonally unfavorable environmental conditions [3]. Dormancy is just one among quite a wide range of reasons why a seed may not germinate [4]. The concept of dormancy signifies that the miniature plant has life but require other factors beyond external factors like temperature and water to resume growth. Inhibition of germination is therefore completely or partially linked to a combination of three seed borne mechanisms, notably Chemical inhibitors that prevent growth, physical barriers that prevent the uptake of water, gases or chemicals and incomplete development of embryo prior to seed dispersal. In the later mechanism, the embryo of the seed needs extra time after dispersal to ripen [5, 6], and optimum levels of internal hormones [7]. Seed germination is the most critical part in the life cycle of seed bearing plants and seed dormancy is an excellent capability to increase the chance of survival by optimizing the distribution of germination in time or space [8].

The significance of seed dormancy can be seen from the ecological and agronomic stand points. Ecologically, seed dormancy can be beneficial for propagation and dissemination of plant populations while in agronomic systems, dormancy is a problem for seed evaluation and seedling establishment. For example it has been reported that when seed dormancy level is too low, it can trigger pre harvesting sprouting leading to either yield loses in cereals or germination before the start of a favorable growth season, risking seedling mortality. In contrast, deep seed dormancy levels limiting production in many field crops as it turn to delay germination and reduce the length of the growing season [3, 9].

#### **1.1 Definition**

There is yet no consensual definition for dormancy therefore many definitions and classifications exist [1]. It is a situation whereby a viable seed fails to germinate though given presumably favorable conditions [10]. Dormancy in a strict sense will refer to the inability of an intact viable seed to resume growth even when the environmental conditions are most favorable [1, 11]. Dormancy is delay of a viable seed to germinate, under a given set of environmental conditions and will only germinate if restricting factors are eliminated either via natural or artificial means [12]. Based on the later definition, it is evident that the state of dormancy can only be experimentally proven when the seed is placed under suitable external growth conditions and nonetheless germination process is not initiated, even though embryo is a life. The process is thus complex as it is difficult to appreciate the degree of restriction imposed by each seed borne characteristics contributing to delay resumption of growth by the embryo.

#### **1.2 Significance of dormancy**

Whether a seed should remain dormant or proceed to germination under certain circumstances is important in two aspects; first with respect to its survival as a species under specific ecological conditions and secondly relating to its economic and agronomic importance. From an ecological viewpoint, dormancy is an important survival mechanism that favors propagation and dissemination of seeds to establish plant populations. Because specific conditions are required to break dormancy, it may favor germination and seedling emergence under more favorable conditions [2]. *Seed Dormancy: Induction, Maintenance and Seed Technology Approaches to Break Dormancy DOI: http://dx.doi.org/10.5772/intechopen.106153*

Heterogeneous and asynchronous seed germination in the soil over years due to dormancy is an extra advantage to the survival of some species. This is because individual seeds in a seed population usually have different levels of dormancy, spreading their germination over time. This delay avoids unfavorable environmental events such as a drought that would eliminate the population if all the seeds were to germinate at same time on one hand and intra-specific competition for the available resources within the ecosystem on the other [13]. This explains why weeds are difficult to eliminate in a field because the seed banks provide a vast array of seeds with differing levels of dormancy. Although deep seed dormancy is considered problematic in agricultural species, some level of dormancy is desirable to prevent vivipary, a phenomenon rampant in cereals in which pre-harvest sprouting occurs. Vivipary causes losses in seed quality and quantity in agricultural plants. Regardless of all the advantages of dormancy for natural plant populations, it is an undesirable trait for most economic crops because it makes rapid and uniform germination during crop establishment difficult.
