*2.1.3 Oxygen*

Seeds of many species will not germinate well at an oxygen level considerably lower than that normally present in the atmosphere [19]. From the physiological point of view studies are still to prove that inadequate oxygen supply induces dormancy [21]. Nevertheless, it has been acknowledged that oxygen is required to break chemical dormancy caused by germination restriction substances located in the endocarp [22]. However, insufficient oxygen supply under excessive moisture in a growth medium delays initiation of germination [23, 24]. In the tropics oxygen availability is usually not a limiting factor since germination usually takes place at room temperatures [25]. It has been reported that germination of oil-palm seed is dependent upon a minimal threshold concentration of oxygen in the embryo [22].
