PLANT GENETICS 



17 



developed to explain Mendelian heredity, it will be necessary to 

 give some of the main facts of reproduction in plants. 



The Mode of Sexual Reproduction in Flowering Plants. 

 Nearly all higher plants produce seeds as the result of the union 

 of sexual cells or gametes. Each body cell which is capable of 

 further division contains a nucleus in which the chromatin is 

 located. This chromatin, which is composed of a definite number 

 of parts or chromosomes, gains its name from the fact that it 

 takes a dark stain with certain reagents when other parts of the 



Male 



Archesporial or megaspore 

 mother cell 



eduction division 



Period 



Nucleus with of 



chromosomes divisio 



Embryo sac 



Archesporial, cell 



Synergids 

 Egg cell or female gamete/ 



Embryo sac 



Polar or endosperm nuclei 

 Antipodal cells of 

 nutritional value 



2-celled stage 

 or diad 



4 -celled stage 

 or tetrad 



Pollen 

 grain 



nucleus 

 Generative 

 nucleus 



FIG. 3. Diagram to illustrate production of male and female gametes. A, 

 In some forms as Lilium this megaspore mother cell functions directly as the 

 embryo sac". Reduction division in Lilium occurs at the first nuclear division 

 within the embryo sac. 



cell are unstained. In the soma or body of the plant the nucleus 

 of each cell contains a definite number of chromosomes, half of 

 which were obtained from the male sexual cell and half from the 

 egg cell. Each new body cell results from the longitudinal 

 division of the chromosomes of a preceding body cell. Thus 

 all of the somatic cells of a plant contain the same number of 

 chromosomes. 



Preparatory to the formation of the germ cells or gametes, 

 the chromosomes assume a paired condition, one member of each 



