20 N. H. Agr. Experiment Station [Bulletin 280 



beans, tomatoes, and potatoes to study the effect of strength of mix- 

 ture and rate of drying. Results obtained to date indicate that the 

 rate of drying has little or no effect on the degree of injuiy produced. 

 (Adams Fund) 



Hardier Potatoes Grown at Low Temperatures 



A growing temperature averaging around 58 degrees Fahrenheit is 

 more conducive to hardiness in potatoes than a mean temperature 10 

 degrees higher, according to studies continued by Stuart Dunn on the 

 effect of growing temperatures, mineral nutrition and vegetative se- 

 lection on plant hardiness. His work indicates that northern-grown 

 potatoes are likely to have greater resistance to early frosts. 



Cabbage and potatoes were both grown at mean temperatures of ap- 

 proximately 68 degrees and 58 degrees. After reaching sufficient size 

 plants of both vegetables were frozen, the cabbages at 23 degrees and 

 the potatoes at 29 to 30 degrees. Both were kept at these respective 

 temperatures for 24 hours. 



In the case of cabbage the temperature at which the plants were 

 grown did not appreciably effect their resistance to injury from freez- 

 ing. 



All the potato plants grown at 68 degrees, were injured when sub- 

 jected to freezing, 12 per cent of them severely, 48 per cent markedly 

 and 40 per cent slightly. 



The plants raised under 58 degrees temperature showed only slight 

 injury at most from freezing; 88 per cent were hardy enough to with- 

 stand this test. 



The potatoes used in this experiment were obtained from stock orig- 

 inally from the same source, which had been grown to maturity at 

 58 and 68 degrees for three generations. 



In studying the effect of mineral nutrition on resistance to freez- 

 ing, sand cultures of cabbage were treated with high and low levels 

 of nitrogen, potassium and phosphoiiis. Results were generally incon- 

 clusive, although apparently pointing to greater resistance in the case 

 of high-level cultures. 



In the work on vegetative selection the greenhouse plant, Bryophyllu, 

 was mainly used, although potato and Jerusalem artichoke are also 

 being tried. This system consists of raising plants from leaf cuttings 

 rather than seed so as to hold to a pure strain. 



In starting this research cuttings were grown from ordinary green- 

 house plants of Bryophyllum and frozen for 24 hours at 1.1 degrees 

 below zero. Centigrade. From the few which survived cuttings were 

 eventually obtained. These produced 63 plants which were frozen with 

 the following results: 35 uninjured, 11 slightly injured and 17 killed. 

 (Adams Fund) 



Leafroll, Mosaic Studies Continued 



Studies of mosaic and leafroll of potatoes are being continued. No 

 new data have been obtained other than that reported a year ago. 

 (Puniell Fund) 



