22 



MISCELLANEOUS PUBLICATION 1271, U.S. DEPARTMENT OF AGRICULTURE 



40- 



30 



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111 



£ 20 



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 a 



10 



TOTAL PLANT 

 15 



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LEAF 

 BLADES 



STEMS and 

 PETIOLES 



5 10 O 5 



TIME (days) 



Figure 7. — Dry weight of bean plants and plant parts 

 as affected by growth in salinized solutions for vary- 

 ing periods of time. Same conditions and symbols as in 

 figure 6. 



then this effect will predominate. The case for a 

 minimum turgor pressure necessary for cell en- 

 largement has been well established (7, 8). In 

 the absence of reduced turgor, however, the 

 growth reduction is due to something else. It is 

 in these cases that I propose the acceleration of 

 senescence to be of importance. Furthermore, the 

 increased osmotic pressure in the osmotically ad- 

 justed plant probably is the cause of this effect. 

 There already exists good data to support this 

 hypothesis (14, 20). 



Literature Cited 



(1) Anderson, W. P., D. P. Aikman, and A. Meiri. 

 1970. excised root edudation-a standing gradient 

 osmotic flow. Proc. Roy. Soc. Lond. B. 174 : 

 445-458. 



(2) Bernstein, L. 



1961. osmotic adjustment of plants to saline 

 media, i. steady state. Amer. J. Bot. 48 : 

 909-918. 



(3) 



1963. osmotic adjustment of plants to saline 

 media, n. dynamic phase. Amer. J. Bot. 50 : 

 360-370. 



— , and H. E. Hayward. 



(4) — 

 1958. physiology of salt tolerance. Ann. Rev. 



Plant Physiol. 9: 25-46. 



(5) Black, R. F. 



1960. effects of nacl on the ion uptake and 

 growth of atriplex vesicaria heward. Aus- 

 tral. J. Biol. Sci. 13: 249-266. 



(6) Boyer, J. S. 



1965. EFFECTS OF OSMOTIC WATER STRESS ON META- 

 BOLIC RATES OF COTTON PLANTS WITH OPEN 



stomata. Plant Physiol. 40: 229-234. 



(7) 



1968. RELATIONSHIP OF WATER POTENTIAL TO GROWTH 



of leaves. Plant Physiol. 43: 1056-1062. 



(8) 



1970. LEAF ENLARGEMENT AND METABOLIC RATES IN 

 CORN, SOYBEAN, AND SUNFLOWER AT VARIOUS 



leaf water potentials. Plant Physiol. 46 : 

 233-235. 



(9) Burstrom, H. G., Inger Uhrstom, and R. Wurscher. 

 1967. growth, turgor, water potential, and 



young's modulus in pea internodes. Phys- 

 iol. Plant. 20: 213-231. 



(10) Dale. J. E. 



1968. cell growth in expanding primary leaves 

 of phaseolus. J. Expt. Bot. 19: 322-332. 



(11) Eaton, F. M. 



1927. THE water requirement and cell sap con- 

 centration OF AUSTRALIAN SALTBUSH AND 

 WHEAT AS RELATED TO THE SALINITY OF THE 



soil. Amer. J. Bot. 14: 212-226. 



(12) 



1942. TOXICITY AND ACCUMULATION OF CHLORIDE AND 



sulfate salts in plants. J. Agr. Res. 64 : 

 357-399. 



(13) Fischer, R. A., and R. M. Hagen. 



1965. PLANT WATER RELATIONS, IRRIGATION MAN- 

 AGEMENT, AND CROP YIELD. Expt. Agr. 1 I 



161-177. 



(14) Flowers, T. J., and J. B. Hanson. 



1969. THE EFFECT OF REDUCED WATER POTENTIAL ON 



soybean mitochondria. Plant Physiol. 44 : 

 939-945. 



(15) Gale, J., H. C. Kohl, and R. M. Hagan. 



1967. changes in the water balance and photo- 

 synthesis OF .onion, bean and cotton 

 plants under saline conditions. Physiol. 

 Plant. 20: 408-420. 



