14 



EFFECT OF SOLUBLE SALTS UPON PLANTS. 



A third experiment in which the leaves were weighed at more 

 frequent intervals gave results as follows, the weights being expressed 

 in milligrams: 



Table IV. — Transpiration from leaves of plants grown in a saline and in a nonsaline 

 soil as shown by the results of weighings at frequent intervals. 



Conditions oi loaves and soil in which grown. 



With bloom (grown in a soil containing 1.5 



per cent oi soluble salts> 



Without bloom (control) 



Weight s at intervals of one-half to three-fourths hour. 



12.45 



1.15 



1.45 



2.15 



2.45 



3.30 



4.15 



p. in. 



p. m. 



p. m. 



p. m. 



p. m. 



p.m. 



p. m. 



mg. 

 281 



mg. 

 276 



mg. 

 27'J 



mg. 

 272 



mg. 

 270 



mg. 

 268 



mg. 

 267 



251 



227 



220 



215 



211 



205 



200 



The leaves with bloom lost a total of 14 milligrams, or about 5 per 

 cent of their original weight, while those without bloom lost 51 milli- 

 grams, or about 21 per cent of their original weight. 



Whether the retardation of loss of water from the leaves of plants 

 grown in soils containing considerable quantities of soluble salts 

 when cut from the stems and exposed to the air is due to the presence 

 of the bloom that develops on the leaf under these conditions or to 

 the concentration of the cell sap, or to a combination of these factors, 

 remains to be determined. The above-described results demonstrate, 

 however, that leaves of wheat plants grown in saline soils containing 

 as much as 1.-3 per cent of salts lost considerably less moisture when 

 cut oil" and allowed to dry than leaves of plants of the same species 

 grown in a soil where no excess of salts was present but under similar 

 conditions otherwise. Since in the former case, however, a relatively 

 thick deposit of wax had developed upon the surface of the leaves, it 

 is reasonable to assume that the presence of this bloom played some 

 pari in the decreased transpiration." 



"Sachs i^Fhysiology of Plants) says: "The epidermis affords a protection against 

 i he excessive evaporation of the water from the leaves and voting shoot-axes by means 

 of the cuticle and the waxy coatings, which it is true do not absolutely prevent the 

 evaporation of water from the epidermis cells, hut render it exceedingly slow." 



Reynold- (The Effect oi Bloom on the Transpiration of Leaves. Bulletin No. 9, 

 Oberlin College. 1898) found that the leaves of Agave utahensis, A. verschafelti, A. sp., 

 Echevera peacocMi, and Cotyledon sp. from which the bloom had been removed lost 

 about one-third more water than the same plants from which the bloom had not been 

 removed. The results of Reynolds agree with those of Fr. Haberlandt (yWissensch 

 praktische UntersuchungeD auf dem Gebiete des Pflanzenbaues, 3: L56, 1877), who 

 claims to have proved that the bloom on rape leaves is formed as a check upon transpira- 

 tion, and with Garreau i Ann. d. Sci. Nat.. L3: 322, L849), who says that the removal 

 of any waxy covering the leaf may possess favors transpiration. 

 134 



