38 PHYSIOLOGICAL ROLE OF MINERAL NUTRIENTS. 



THE PHYSIOLOGICAL IMPORTANCE OF LIME SALTS IN PLANTS. 



The greater the leaf surface developed in a given time, the more lime 

 is necessary. A normal crop of wheat requires per hectare (nearly 2.5 

 acres) about 11.6 kilos; sugar beets, 30.2 kilos; grass, 4!). 4 kilos; 

 clover, 111.8 kilos, and tobacco, 153.7 kilos, while a normal growth of 

 wood needs annually about 20 kilos of lime, besides 7 to 16 kilos of 

 magnesia, 2 to 10 kilos of potash, and <>.s to 4 kilos of phosphoric acid. 

 When the large demand by plants for lime .salts is taken into consider- 

 ation, it is easily understood that an absence or deficiency of lime 

 becomes apparent very early. 



Stohmann" kept maize shoots alive for some time in a culture solu- 

 tion free from lime, but all development gradually ceased with the 

 consumption of the stored-up lime. However, when at the end of 

 several weeks some calcium nitrate was added, a very striking effect 

 was noticed, hardly five hours elapsing before new buds pushed out 

 from the sickly looking tips. 



Heiden'' observed that maize and peas in culture solutions without 

 lime lived only four weeks, and reached respectively only 18.9 and 27 

 cm. in height. In culture solutions without magnesia, however, maize 

 lived ten to twelve weeks and peas lived eight weeks and attained a 

 height of 11 and 30 cm. respectively. In solutions without potasea or 

 phosphoric acid, but otherwise complete, such plants lived from eight 

 to twelve weeks. The absence of lime, therefore, was felt first, owing 

 probably to the relatively small amount of lime in the reserve store of 

 the seeds.. 



Palladin" placed etiolated leaves of Viciafaha on the surface of dis- 

 tilled water, on a 10 per cent cane-sugar solution, and on solutions of 

 0.3 per cent calcium nitrate with and without the addition of cane 

 sugar, but a noticeable growth was observed only where both sugar 

 and calcium nitrate were present. The same author"' has found that 

 etiolated leaves of Vicia faba contain less lime than do green leaves. 

 His analysis showed that there were contained in 1,000 parts of green 

 leaves 13.3 parts of lime, but in 1,000 parts of etiolated leaves only 

 2.6 parts of lime. The former yielded 10.3 per cent of ash, the latter 

 7. 54 per cent. Stoklasa found in diseased leaves of the sugar beet less 

 than half the amount of lime present in healthy leaves of this plant. 



"Ann. Chem. Pharm., Vol. CXXI. 



6 Centralbl. f. Agr. Chem., Vol. XVII, p. 622. Prianishnikow observed that shoots 

 develop quicker in a solution of gypsum than in distilled water, which fully accords 

 with the writer's observations. Seedlings of Pkaseolus, Pisum, and Cucurbita kept 

 in distilled water die before all the reserve material is consumed. An addition of 

 a calcium salt to the distilled water leads, however, to the perfect exhaustion of the 

 reserve stores (Boehm, Liebenberg). 



cBer. d. Dent. Bot. Ges., 1891, p. 2.30. 



<*Ber. d. Deut. Bot. Ges., Vol. X, p. 179. 



