CHAPTER 11 



Seed Germination 



Michael Evenari 

 Hebrew University, Jerusalem 



Introduction: Historical — Definitions of terms used. Photoblastism as a function of 

 external conditions: Temperature — Quantity and quality of light — Chemicals. Photo- 

 blastism as conditioned by pretreatment: Photo- and skotodormancy — Pretreatment with 

 different temperatures — Presoaking and drying — Climatic conditions during ripening of 

 seeds. Photoblastism as a function of inner conditions: Influence of coats enveloping 

 embryos — Afterripening — Photoblastism and metabolism. Conclusions: Summary of 

 facts — Theories — Suggestions for further work. Addendum. References. 



1. INTRODUCTION 



1-1. HISTORICAL 



Caspary (1860) was the first botanist to observe the beneficial influ- 

 ence of light on germination. But it was not until 1881 that Stebler 

 (1881a,b,c) investigated the problem of light germination in a systematic 

 manner. Using the achenes of different grasses, he proved that the grains 

 of a number of grass species germinate much better in light than in dark- 

 ness. In 1903 Heinricher reported the first case of germination inhibition 

 caused by light {Acanthostachys strohilacea) ; his paper was followed in 

 1904 by a paper by Remer, who showed that the seeds of Phacelia tana- 

 cetifolia, which have since been used frequently, germinate better in dark- 

 ness than in light. 



Since then the research on the influence of radiation on germination 

 has developed along two different lines. On the one hand, agriculturists, 

 seed testers, and others have reported a steadily mounting number of 

 species whose germination is influenced by light (reviews given by Kinzel, 

 1907 to 1915b; Niethammer, 1928, 1934). Besides being of considerable 

 practical importance, these investigations have shown that, far from being 

 isolated curio cases, the effect of light upon germination is a widely spread 

 biological phenomenon. This is clearly shown by the very large number 

 of species whose germination is influenced by light, as well as by the fact 

 that, when investigated carefully, such seeds as wheat, corn, and rye, 

 whose germination had been considered to be indifferent to light, were 

 shown to be photosensitive (Burgerstein, 1913; Niethammer, 1928; 



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