CHAPTER X 



THE INITIATION OF THE REPRODUCTIVE PROCESSES 



The initiation of the reproductive processes of the plant should be 

 considered in the light of chemical conditions and the concurrent mor- 

 phological changes. 



THE DEVELOPMENT OF THE FRUITFUL CONDITION 



There is much evidence that conditions associated with carbohydrate 

 accumulation have an important relation to fruitfulness in plants. 



The Response of the Plant to Changes in Relative Amounts of 

 Nitrogen and of Carbohydrates. — Kraus and Kraybilli^^, studying the 

 effects on the tomato of various treatments, found that striking differences 

 in chemical composition and in behavior with respect to fruitfulness and 

 vegetative growth could be produced by controlling the environmental 

 conditions. They summarize their work as follows: 



"1. Plants grown with an abundant supply of available nitrogen and the 

 opportunity for carbohydrate synthesis, are vigorously vegetative and unfruit- 

 ful. Such plants are high in moisture, total nitrogen, nitrate nitrogen and low in 

 total dry matter, free reducing substances, sucrose and polysaccharides. 



"2. Plants grown with an abundant supply of nitrogen and then transferred 

 and grown with a moderate supply of available nitrogen are less vegetative but 

 fruitful. As compared with the vegetative plants, they are lower in moisture, 

 total nitrogen, and nitrate nitrogen, and higher in total dry matter, free reducing 

 substances, sucrose and polysaccharides. 



'•'3. Plants grown with an abundant supply of nitrogen and then transferred 

 and grown with a very low supply of available nitrogen are very weakly vegeta- 

 tive and unfruitful. As compared with the vegetative plants, they are very much 

 lower in moisture and total nitrogen and are lacking in nitrate nitrogen; they 

 are much higher in total dry matter, free reducing substances, sucrose, and poly- 

 saccharides." 



Three typical effects, measured principally in terms of total nitrogen, 

 carbohydrate and moisture have been produced by these three distinct 

 environments. The first is characteristic of vigorous vegetative growth. 

 "An abundance of moisture and mineral nutrients, including nitrates, 

 coupled with an available carbohydrate supply, makes for increased 

 vegetation, barrenness and sterility." ^^^ The second condition represents 

 a readjustment through which the plant must pass before it becomes 

 fruitful. "A relative decrease in nitrates in proportion to the carbo- 

 hydrates makes for an accumulation of the latter; and also for fruitful- 



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