BOOKS AND CURRE:NT LITERATURE 



Frost Injury. — Those who are interested in the physico-chemical 

 interpretation of plant phenomena and in the general principles of 

 pln'siological response to environmental changes, will be especially 

 pleased and encouraged by Harvey's'- account of his studies on tissue- 

 hardening and frost injury. Students of horticulture, etc., who deal 

 with the practical aspects of frost resistance and frost injury in plants 

 wiJl also find much valuable information and stimulation in this paper. 

 The work was well-planned, well carried out and the results are very well 

 presented. A bibliography of 50 titles accompanies the presentation. 



The experimentation was largely with cabbage and tomato plants. 

 An idea of the scope of the paper may be had from the following list 

 of the main subheadings. First indications of frost injury and their 

 development in cabbage and tomato, Mechanism of freezing. Growth 

 development in the injected areas, Peroxidyse changes in the injected 

 areas of cabbage leaves, Plasmolytic behavior of tumor cells, Physio- 

 logical changes in cabbage during the hardening process. Time and 

 temperature factors in acquiring or losing hardiness. Freezing point 

 and expression of cabbage juices, Chemical changes during hardening, 

 Changes in hydrogen-ion concentration of a plant sap on freezing. 

 Changes of reaction on plasmolysis, Potentiometric determination of the 

 changes in hydrogen-ion concentration on freezing. Buffer effect of 

 juice from midrib and rest of leaf. Hydrogen-ion concentration neces- 

 sary for normal condition of the proteins. Precipitation of the proteins 

 of hardened and nonhardened cabbage on freezing, and on addition of 

 acid. 



A significant point is that ''wax on the leaf surface prevents the 

 inoculation [by ice-crystals] of the undercooled tissue and thus pre- 

 vents injury from freezing," when the temperature is not too low or 

 the exposure too long. The tissue liquids are capable of much under- 

 cooling and water on the surface of the leaf has little of this capacity; 

 hence if water occurs on the surface it freezes before the tissue liquids 



1 Harvey, R. B. Hardening process in plants and developments from first 

 injury. Jour. Agric. Res. 16: 83-111. 3 figs, (showing graphs), PI. 7-11 (half- 

 tones) and A (colored). Oct. 14, 1918. 



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THE PLANT WORLD, VOL. 21, NO. 11 



