The evolution of the concepts of growth, development and other related, during the last decades

Abstract

The evolution of such terms as growth, differentiation, development, morphogenesis etc. is discussed. It is proposed that the term (notion) development should be understood to comprise "growth", "differentiation" and even "abscission, abortion and necrosis". The term "development" is already used in such a way by some authors. The relations among the phenomena denoted by the above terms are presented in a graphic form to show that they partly overlap. The concept that growth and development represent quantitative and qualitative aspects (respectively) of plant augmentation is criticized. The newly introduced terms "development hormone" or "development regulator" seem more suitable than "growth hormone" and "growth regulator", however, these later ones are correct and may be used. The traditional term "phytohormone" and the newly introduced one "phytoregulator" seem convenient, but it must be kept in mind that such substances may transmit information both on a chemical basis as well as on a biophysical one. An example here can be auxin; a change in the wavy character of its transport may serve as information. In some cases a complex of two or more substances may play the role of a hormone, for instance ACC and ethylene, of which one is easily transportable but little active and the other is very active but exerts its action rather locally. Other combinations of activities may exist in other such pairs.