Table 23. Response of shoredune panicum transplants 

 to salinity level under greenhouse conditions. 



Soil salinity (/Limho/cm) 1 



Live shoots per seven pots 2 



610 



51a 3 



1,540 



38 a, b 



2,200 



24 b 



2,330 



10 c 



3,280 



5c 



3,350 



4 c 



4,480 



3c 



4,580 



0c 



1. 1:2 sand-water mixture. 



2. Five plants per pot at beginning of study. 



3. Values with the same letter are not significantly 

 different at the P _ 05leveL 



c. Dormancy. High concentrations of carbohydrates in roots and rhizomes of grasses are 

 indicative of dormancy. During periods of accelerated growth, a plant draws on these 

 reserves, causing a substantial reduction in the amount stored (Weinmann, 1961). Since 

 survival is likely to be influenced by food reserves stored in the transplant, monthly root 

 and rhizome samples were collected from bitter panicum and sea oats from 1970-74, and 

 also from saltmeadow cordgrass, shoredune panicum, and seashore dropseed from 1970-72. 

 The total available carbohydrates (TAC) were extracted from the planting material as 

 described by Smith, Paulsen, and Raguse (1964), except that 0.2 normal hydrochloric acid 

 was used instead of 0.2 normal sulfuric acid. Monthly TAC values for both bitter panicum 

 and sea oats from north Padre, 1972-74, are plotted in Figure 27; complete data are 

 included in Table 24. Month to month TAC variation of both species fails to exhibit a well 

 defined seasonal pattern, since growth may occur year round in this climate, and is 

 influenced by irregular drought and rainfall. A period of winter dormancy in both species is 

 shown by high values in both 1972-73 and 1973-74, followed by a pronounced depletion in 

 spring (Fig. 27). Winter 1973-74 was much nrilder than the previous winter, and this is 

 probably the reason for the spring TAC decline 1 month earlier than in 1972-73. However, 

 this pattern is not evident in winter 1971-72. Sea oats exhibited a better defined annual 

 cycle than bitter panicum. 



d. Drifting Sand. Drifting sand accumulating on actively growing plants is essential for 

 dune growth. Established clumps of sea oats and bitter panicum not only tolerate but thrive 

 under the accumulation of a foot or more of sand deposited during a short period. However, 

 freshly transplanted culms are adversely affected by accumulating sand before active 

 transplant growth has begun. Apparently, this is because a buried transplant must deplete its 



86 



