general age-associated state of the individual as a whole up to the time of the 

 formation of the part in question. 



"10. The mechanism and intensity of the aging process differ in resting 

 and in dividing cells." 



Krenke was of the opinion that the slowest aging of all is exhibited by rest- 

 ing meristematic cells, which retain their capacity for energetic division. 

 Among such tissue elements are the points of growth of sleeping and adventive 

 [tr.: ?] buds and the growth points of germinating seeds. The aging process 

 proceeds at the highest rate in "stormy" cell divisions. 



"11. The age-associated variability has its regular morphologicphysiologic 

 and biochemical expression, being characterized by curves with ascending and 

 descending branches or with evident derivatives of these curves, i.e., on the 

 ascending and descending branches, the development of aging is expressed — 

 in general — in an opposite way." 



Krenke made a sharp distinction between two concepts of age: inherent 

 and general age and maturity. "The inherent age of a part of a plant is that 

 time that has elapsed from the moment of its formation to the time under con- 

 sideration, whereas the general age of this same part is determined by its in- 

 herent age and the age of the individual as a whole to the time of formation of 

 the element in question. 



"The term maturity is used to designate the actual vital capacity of the 

 individual and its parts at the time under consideration, which is not usually 

 fully correlated with their calendar age." He supports this position by the 

 following example: 



"As a rule, with the same inherent maturity, those simple organs or parts 

 of them that possess a greater general maturity will be older. For example, 

 month-old leaves of young tea or mulberry plants will be definitely younger 

 than month-old leaves, developing under the same conditions, of old individuals 

 of the same races of plants." 



Krenke's theory has had a certain importance in selection (especially of 

 perennial plants), in the multiplication of plants (especially vegetative), in 

 plant surgery and phytopathology. It has doubtless enriched contemporary 

 ideas about the very concept of age and the character of age-associated changes 

 in plant organisms, i.e., in objects in relation to which these concepts are espe- 

 cially complex and least investigated. A plant is a much less "compact" and 

 indivisible biological system than an animal. In the plant world, we find most 

 strongly represented a "dismemberment" and a considerable independence of 

 the parts of the organism. In addition to this, we find in plants the greatest 

 contrasts in the duration of life: from several minutes or hours in primitive 

 microscopic plants to several thousand years among the Macrozamia, in Wel- 

 lingtonia, the yew, the oak, the baobab, the Lebanese cedar, the Australian 

 eucalyptus, and the Mexican cypress. 



The ontogenesis of plants is highly dependent on their passing through 

 various states (the "staged" character of their development is very pronounced), 

 and this also complicates the establishment of a unitary theory of their age- 

 associated development. 



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