WATER RELATIONS OF SOME PSAMMOPHYTES 



193 



5 hours of the experiment, no fundamental change in the pattern of the 

 curve took place after the plants were supplied with water. 



The daily variations in transpiration among the control group of 

 Corynephorus canescens (Fig. 3) differ from both the microchmatic factors 

 and the curve of Festuca dominii in the position of the second-day noon 

 maximum, which is shifted to the morning hours and followed by a 

 depression of transpiration. The curve of the third day, however, does not 

 show any depression, and the transpiration values are even somewhat 



55 



% 



10 

 5 



IS 



2A 



12 



18 



2A 



12 



\. 



"1- 



FiG. 2. Water relations of Festuca dominii during the three days of experiment. Upper 

 graph: Daily variations of transpiration. Water loss is expressed in parts per thousand, 

 i.e. in mg per i g of water content of the leaves during i niin. Middle graph: Water 

 content of the leaves (as percentage of fresh v^eight). Lower graph: Water content of 

 the rhizosphere of grass tufts (as percentage of dry weight). The 50 hours of experiment 

 are marked on the x-axis. The full Une and dots belong to plants supphed with water. 

 The dotted hne and crosses belong to the control group (observed under natural 

 conditions). 



higher than those of the preceding day. The night minima do not fall to 

 zero and are approximately equal. The pattern of the curve is, however, 

 somewhat different for plants supphed with water. The noon maximum 

 of the second day is higher, shifting towards the midday hours, and 

 markedly exceeds the noon transpiration of the third day. Compared with 

 that of the control group, the morning increase in the third-day rate of 



