**2. Key factors in the induction/maintenance of dormancy and initiation of germination**

#### **2.1 Environmental factors**

The stimuli needed for seed germination include chemical or hormonal signals or environmental signals such as temperature, soil nitrate levels, or light [1]. It is important to keep in mind when dealing with dormancy and germination that a seed is never just under the control of one factor in nature, but many factors concurrently [5].

#### *2.1.1 Temperature*

Seed germination is a complex process involving many individual reactions and phases, each of which is affected by temperature. Because temperature influences both the percentage and rate of germination of seeds, it is one of the most critical factors affecting seed germination. Although seeds of each species have optimal temperatures for attaining maximum germination, between 30 and 40°C for most palms [14]. Alternating temperatures are preferred to constant temperatures because they can overcome shallow seed dormancy and enhance uniform germination. In the wild, most tropical tree seeds generally require higher temperatures to germinate; for example Soil temperatures above 38°C, but below 42°C can reduce the time required for germination of seeds of *E. guineensis* from years to weeks [15, 16].

#### *2.1.2 Water*

Water is a basic requirement for germination and its role as a medium for biochemical processes leading to germination, such as weakening the seed coat, activating enzymes, and breaking down food reserves, scarcely requires emphasis. Physical dormancy has been attributed to a hard or water-impermeable seed cover [17], such as a fibrous mesocarp and/or a stony endocarp, which are very common among palms [18]. It is generally recognized that seed germination is more sensitive to moisture stress than its subsequent seedling development [19]. Though moisture favors germination, excess of it may also become an obstacle to germination due to

improper ventilation for the physiological process of germination [18]. While inadequate moisture results in delayed and poor germination, excessive moisture will hinder germination due to decreased aeration. Metabolic activation, preparation for cell elongation, radicle emergence, and seedling growth are subsequent events of seed germination and require different levels of hydration [20].
