Growth in General 



19 



In many plants, particularly herbaceous ones, growth is not evenly 

 distributed throughout the length of the stem. Thus in tobacco (Wolf, 

 1947) and in maize (Heimsch and Stafford, 1952) the internodes are 

 progressively longer from the base to about half way up the axis and 

 then are progressively shorter to the apex. The distribution of growth in 

 a developing leaf blade also shows local differences (Avery, 1935). Many 

 alterations in form arise from local changes in growth. 



Determinate and Indeterminate Growth. In most animals, growth is 

 part of a definite life cycle and produces a determinate structure. In many 

 plants, on the other hand, the growth of the body is essentially indetermi- 



A |0 



FULL BLOOM 



DAYS 



Fig. 2-5. Intermittent curves of growth of a cherry fruit from flowering to maturity. 

 ( From L. D. Tukey. ) 



nate and, within certain limits, may go on indefinitely through the activity 

 of terminal and lateral meristems. Even such theoretically unlimited 

 growth (such as that of a tree in height or a vine in length), however, 

 usually reaches a limit and in its growth follows a curve which is S- 

 shaped. In some plants, such as the sunflower and most grasses, height 

 is not indeterminate but is limited by a terminal inflorescence, and stem 

 growth in such cases is typically sigmoid. Lateral organs, such as leaves 

 and fruits, which do not grow by localized meristems have still more 

 definite growth cycles and are quite comparable to single animal indi- 

 viduals and show similar growth curves. Examples of these are fruits 

 (Fig. 2-1), leaves (Wolf, 1947), and ovules and embryos (Rietsma et al, 



