Killing of Plant Tissue by Low Temperature 



163 



It may be said, however, that the solutions all reduced the 

 growth of the plants, as indicated by the following weights: 



Average weight of plants watered with Potassium Chloride 2.27 grams 



Average weight of plants watered with Sodium Chloride 1 . 89 grams 



Average weight of plants watered with Magnesium Chloride 2.33 grams 



Average weight of plants watered with Ammonium Chloride 1 . 78 grams 



Average weight of plants watered with Sodium Nitrate 1 . 68 grams 



Average weight of plants watered with Distilled Water 2 . 63 grams 



The percentage of killing will thus be seen to be as much in 

 proportion to growth as in inverse proportion to depression. 



Corn seedlings were also grown where water was withheld, 

 being watered only when it was necessary to keep them from dying. 

 The following table gives the results: 



Table 4. Showing Effect of Withholding Water on Sap Den- 

 sity AND Hardiness of Zea Mays. 



It will be seen again that withholding water increased the sap 

 density (depression) and lowered the killing temperature. It also 

 reduced the rate of growth and probably the size of the cells, so we 

 can not conclude with certainty that the greater hardiness is due only 

 to the greater sap density. 



Tomatoes were grown in the same way except that there were 

 three lots some well watered, others watered only when it was 

 necessary to keep them from dying, and some others grown outside 

 at a temperature considerably lower than that in the greenhouse. 

 The folUnving table gives the results: 



