FACTORS AFFECTING SALT ABSORPTION 71 



that if any two plants even of the same species were placed under 

 identical conditions, they would each absorb salts in the same 

 proportions or at the same total rate. Individuals of the same 

 clone may be expected to show the smallest differences between one 

 another, while varieties, species and genera show increasing marked 

 contrasts in the pattern of absorption. Species within genera, 

 however, sometimes have features in common; for example, the 

 characteristic accumulation of selenium in species of Astragalus 

 referred to above (Chapter 1, p. 4), and of sodium in Atriplex spp. 

 (Fig. 25). On the other hand, species of a single genus sometimes 

 differ markedly in the relative amounts of potassium and sodium 

 absorbed from a given environment as is the case in Plantago 

 lanceolata and Plantago maritima (Fig. 25) and species of Valonia 

 (Table 17 B, p. 153). Genetic factors affect not only the sap com- 

 position of Valonia species in a given environment, but they can also 

 modify the influence exerted by other factors, such as light intensity, 

 upon it (see Chapter 9, pp. 153-4). 



For further reading 



Broyer, T. C. (1951). The nature of the process of inorganic solute accumu- 

 lation in roots. In Mineral Nutrition of Plants (Ed. E. Truog). (Chap. 8, 

 pp. 187-260). Univ. of Wisconsin Press. 



EpsTErN, E. (1956). Uptake and ionic environment (including external pH) 

 Encycl. Plant Physiol. II, 398-408. 



Epstein, E. (1956b). Mineral Nutrition of Plants: Mechanisms of uptake and 

 transport. Ann. Rev. Plant Physiol. 1. 1-24. 



Kramer, P. J. (1956a). The uptake of salts by plant cells. Encycl. Plant Physiol. 

 n, 290-315. 



Steward, F. C. and Sutcliffe, J. F. (1959). Plants in relation to inorganic 

 salts. In Plant Physiology. A Treatise (Ed. F. C. Steward). (Vol. II.) 

 (pp. 253-478). Academic Press, New York. 



