Seeds are a vital component of the world's diet. Cereal grains alone, which comprise -90% of all cultivated seeds, contribute up to half of the global per capita energy intake. Not surprisingly then, seed biology is one of the most extensively researched areas in plant physiology (Bewley 1997).
With the seed, the start of the next generation of plants begins. The seed, containing the embryo, is structurally and physiologically adapted in its role as a dispersal unit and has ample food reserves to sustain the growth in the seedling until it establishes itself as a self-sufficient, autotrophic organism. The function of all seed is to establish a new plant; therefore it may seem peculiar that dormancy, a natural block to germination, exists. However it may not be advantageous for the seed to germinate freely, even in what may seem to be optimal conditions. For example, germination of annuals in the spring allows time for vegetative growth and the subsequent production of off-spring, whereas germination in similar conditions in the autumn could lead to the demise of the vegetative plant during the winter. Thus, dormancy is an adaptive trait that optimises the distribution of germination over time in a population of seeds (Bewley 1997).
By definition, germination incorporates the events that commence with the uptake of water by the quiescent dry seed and terminate with the elongation of the embryonic axis. (Bewley et al 1994).
The visible sign that germination is complete is usually the penetration of the structures surrounding the embryo by the radicle; the result is often called visible germination. Subsequent events, including the mobilisation of the major storage reserves, are associated with growth of the seedling. Nearly all of the cellular and metabolic events that are known to occur before the completion of germination of non-dormant seeds also occur in imbibed dormant seeds; indeed, the metabolic activities of the latter are frequently only subtly different from those of the former. Hence, a dormant seed may achieve virtually all of the metabolic steps required to complete germination, yet for some unknown reason, the embryonic axis (i.e., the radicle) fails to elongate (Bewley 1997).
Abstract,Introduction,Germination,Dormancy,Temperature,Light,Ecotypes
Ecotype-Storage,Soil preperation,Seed Sowing,Germination-Conditions,Measurement of Results
Cond1,Cond1rep,Cond2,Cond3,Cond4,Cond5,Cond6,Cond6rep,Cond7,Cond8
Discussion,Future-experiments,References