Control of Tundra Plant Allocation Patterns and Growth 



163 



Vegetative Tiller 



Flowering Tiller 



Inflorescence 



o 

 o 



o 



i 

 ■o 



E 



-2- 



FIGURE 5-9. Simulated seasonal changes in rates of growth and main- 

 tenance respiration, and in dry weight gain by gross (Pc) and net (Pn) 

 photosynthesis, and translocation to rhizomes (Tr), leaves (Yl) and in- 

 florescences (T,) for vegetative (V2) and flowering tillers o/ Dupontia 

 during 1973. (Calculated from Lawrence et al. 1978.) 



increases in parallel with biomass. The translocation rate represents a net 

 import from other members of the system, because there are no leaves 

 and hence no photosynthesis in a VO. 



Simulations suggest that the rhizome of a vegetative tiller (Figure 

 5-9) has a significantly negative growth rate, i.e. decreases in weight, 

 through July and recovers through August and early in September. The 

 simulated seasonal course of growth in blade tissue is negatively cor- 

 related with growth of the belowground organs, changing from positive 

 values early in the season to negative ones in late August. Calculations 

 predict accurately the observed seasonal changes in biomass. The simu- 

 lated seasonal changes in maintenance respiration reflect changes in size 



