Mineral Nutrition; Major Elements • 111 



tant compounds. In the investigation cited, the effect on flowering 

 was about the same whether the diffusate was made by soaking 

 the seeds at 23° or at 4° C; since only the latter temperature would 

 vernalize, the activity cannot be considered to represent a vernalin 

 (Chapter Five). 



MINERAL NUTRITION; MAJOR ELEMENTS 



The question of the relationship between mineral nutrition 

 and flowering is embodied more in practical lore, and less in experi- 

 mental data, than almost any other aspect of flowering physiology. 

 Because of this, relatively little can be said here. Not that such 

 lore is necessarily incorrect, but it is usually uncertain and often 

 extremely local. One reason is that distinctions between relatively 

 specific effects on (lowering and those simply associated with changes 

 in vegetative growth are usually not made, as indeed they do not 

 need to be, for many practical purposes. Thus one frequently finds 

 that nutritional conditions that simply favor optimal growth will 

 be recommended to increase flowering and fruiting. 



Interestingly enough, one of the commonest examples of such 

 practical lore is the opposite belief, that flowering may result from 

 conditions causing poor vegetative growth or restraining growth 

 in some way. Although this may be simply an inverse recognition 

 of the fact that in many plants flowering and fruiting are associated 

 with and may cause a reduction in vegetative growth (see Leopold 

 et al., 1959), there may be more to it. The clearest recent study 

 on this question has nothing to do with mineral nutrition, but 

 tends to confirm the view that, at least in certain plants, growth 

 restraint can promote flowering. Kojima and Maeda (1958) studied 

 a variety of radish (Raphanus) in which flowering is hastened by 

 vernalization. In unvernalized seedlings, flowering and bolting 

 were promoted by several treatments that greatly impeded the 

 growth of the stem apex. The most effective was to imbed the 

 upper part of the seedling for several days in gypsum; another was 

 to immerse the seedlings in relatively concentrated sugar solutions, 

 which inhibited growth osmotically. The mechanism by which a 

 growth restraint might promote flowering is unknown, but the data 

 seem clear and suggest that such notions are better tested than 

 dismissed. 



