Meiosis and Chromosomal Segregation 



25 



Pericarp 



Aleurone 



Endosperm 

 Embryo 



figure 2-8. Life cycle of corn, Zea mays. See text for description. 



days. Adults can live as long as 10 weeks, 

 during which a female can lay several thou- 

 sand eggs. 



2. Zea mays 4 



Corn or maize, like the bean and the 

 garden pea, usually produces both male and 

 female sex organs on the same plant and is 

 therefore monoecious ("one house"). Since 



4 See the Appendix to this chapter, on p. 29, for 

 references to corn experiments and literature. 



the diploid corn plant produces male and 

 female spores, microspores and megaspores 

 respectively, it represents the sporophyte 

 stage of the life cycle (Figure 2-8). The 

 microspores are produced in tassels at the 

 end of the stem. Here diploid microspore 

 mother cells, or microsporocytes, each un- 

 dergo meiosis to produce four haploid micro- 

 spores (A), each of which develops into a 

 pollen grain (B). 



Since the haploid microspores give rise to 

 the haploid gametes, these two points in the 



