SUMMARY 

 O2 UPTAKE 



Juvenile Hormosira 



100 



Adult Hormosira 



12 4 8 



HOURS AFTER IMMERSION 



16 



Fig. 210 Respiration rate of juvenile and adult Hormosira hanksii 

 and Ecklonia radiata after desiccation and re-immersion. Note that 

 the adult Hormosira and Ecklonia return to the control value (non- 

 dehydrated plants) but the juvenile Hormosira does not. (After 



Bergquist.) 



appeared as a result of the habitat they occupy. In the case of Hor- 

 mosira the rate of water loss is correlated with bladder size (see 

 p. 213)5 the larger the bladder the slower the rate of water loss (Fig. 

 209A). Plants with large bladders occur at the higher levels on the 

 shore so that morphology provides protection in this species. A 

 further feature that has received very littie attention is the effect of 

 desiccation upon the major metaboHc processes, respiration and 

 photosynthesis. A recent study upon Hormosira (Bergquist, 1957) 

 has shown that the effects may be quite different in the sporehng 

 as compared with the adult (Fig. 210). This may be of profound 

 significance and further work is clearly required. It appears that the 

 respiration rate decreases with increasing desiccation (Bergquist, 



1957). 

 For comparison with the water relations of fucoids, reference 



may be made to the work of Anand (1937) on the marine algae of 



the Dover cliffs. Here two important belts are dominated, the one 



by Enteromorpha and the other by Chrysophyceae. Anand found 



that the Enteromorpha mat lost 25 per cent of its moisture in the 



first 3 hours of exposure, whilst the Chrysophyceae belt lost 8-4 



per cent. The relative loss by evaporation from these two belts is 



shown in Fig. 21 lA, whilst the corresponding loss due to drainage 



is shown in Fig. 21 IB. The measurements were obtained by the 



390 



