200 A. M. MAYER 



tion? My second question: is a case known in plants, similar to 

 that in insects, where the life history of one stage of development 

 may affect the dormancy of the next stage? 



Klein: Some seeds will only germinate on the surface of the 

 soil and need light for it. It is, however, not a heat effect, as a 

 short illumination with weak red light will give this effect. The 

 effect of white light preventing germination might be protective 

 for seeds germinating underground. As to your second question, 

 there are cases where the photoperiodic regime of the mother 

 plant has an influence on the seeds. 



Koller: a case of the photoperiodic regime of the mother 

 plant, affecting the dormancy of the seed has been reported by 

 Lona on Amaranthus; seeds formed on long days were more 

 dormant than seeds form.ed on shorter days. 



Hestrin : I would like to point out that botanists working in 

 morphology describe plant structures in their minutest detail. 

 Once, however, they deal with biochemistry, they are satisfied 

 with effects caused by whole organisms. For example, increases 

 and decreases in activity were noted and ascribed to mito- 

 chondria in lettuce seeds, without any indication as to the 

 origin of these mitochondria, the work being performed on a 

 mixture of tissues. It seems to me that this biological work can 

 be brought to a biochemical level by the use of single cells or of 

 homogeneous tissue. Would unicellular algae or pollen grains 

 be suitable in the study of the dormant state? 



I would also like to propose a hypothesis as to the mechanism 

 responsible for induction and breaking of dormancy: suppose 

 the cell contains in one compartment nutrients and in another 

 enzymes. The breaking of dormancy would be the rupture of 

 the separating wall, the induction of dormancy the erection of 

 such a separating wall. 



Poljakoff-Mayber : The lettuce seed we have been working 

 on consists of the embryo and tissues which are to a large 

 extent degenerated. It follows that the mitochondria must have 

 come from the embryo. Within the embryo the concentration 

 of mitochondria may vary, but such observations would require 



