Control of Tundra Plant Allocation Patterns and Growth 



141 



GROWTH PATTERNS OF TUNDRA GRAMINOIDS 



Growth Form of Dupontia fisheri 



Dupontia, like most grasses, consists of a prostrate, subterranean 

 branched stem (rhizome), aerial shoots, and roots produced from below- 

 ground nodes (Figure 5-1). Each new tiller is initiated from an axillary 

 bud of a leafing node. As the bud develops and the rhizome elongates be- 

 low ground, the tiller is termed a "VO," a tiller containing only rhizome 

 phytomers. At Barrow a VO tiller seldom reaches the stage of leaf exser- 

 tion in its first season of growth, whereas mid-latitude grasses generally 

 exsert leaves in the same season that rhizome growth begins (e.g. Koller 

 and Kigel 1972). During the second growing season, when the shoot ap- 

 pears above ground, the tiller is designated "VI," a tiller in its first sea- 

 son of shoot production. The tiller then produces three or four new 

 leaves each year. Tillers in their second, third and fourth years of growth 

 above ground are designated "V2," "V3," and "V4," respectively. 



A second VO and sometimes a third or fourth may be produced by 

 any tiller in its first year of leaf production. These subsequently pro- 

 duced tillers are designated as "primes" (for example VO ', VI ') to indi- 

 cate their age class and relationship to other members of that class. Sub- 



FIGURE 5-1. Typical tiller system o/ Dupontia fisheri showing age class- 

 es of component tillers. The letter V with associated number indicates the 

 age class of the tiller (see text). (From Allessio and Tieszen 1975a.) 



