Feb. 9, 1924 
Resistance of Wheat to Puccinia graminis tritici 383 
Ward (5#), Arthur (4), and Stakman (50) emphasized the importance 
of the effect of the physiologic condition of the host plant on the develop¬ 
ment of rust. Their general conclusion was that the vigor of the parasite 
is directly proportional to the vigor of the host. Biffen (6) concluded 
that the virulence of P. glumarum is dependent on the amount of fertili¬ 
zer used. 
It has long been considered that the plane of metabolism of the 
host profoundly influenced the degree of development of rust. See Raines 
(42). See also paper of Stakman and Aamodt in the present number of 
this Journal. The opinion has been prevalent that heavy applications 
of nitrogen increased the susceptibility of cereals to rusts. See Sorauer 
(48), Hiltner (23), Comes (10), Spinks (49), Little (29), Bolley (7), 
Anderson (3), Remer (43), Freeman (14) f Cobb (8), Stakman and Aamodt 
(53). It has also been thought that potassium and phosphates rendered 
them more resistant. See Montemartini (35), Muller and Molz (36) , Sorauer 
(48) , Hiltner ( 23 ), Comes (10) , Spinks (49), Remer (43) . On the other hand, 
Pantanelli (39) found that excess phosphate in relation to nitrogen increased 
resistance only when it checked the growth of the host plants. Stakman 
(32) states that large amounts of nitrogenous fertilizers, particularly 
on soils which do not need them badly, will permit greater rust damage. 
Plants so fertilized have a weak straw which crinkles badly when rust 
attacks it. The development of a stiff straw is desirable, and plants 
fertilized with potassium or phosphate fertilizers usually yield better 
in bad rust years than those heavily fertilized with nitrogen. 
As to the influence of certain physicochemical properties of the sap 
of the host plant upon rust development, Comes (10) concludes that 
resistance of wheat to P. glumarum is increased by superphosphate 
fertilizer but is weakened by nitrogenous, fertilizer, and suggests that 
this increased resistance might be due to an increase in the acidity of 
the sap. He states that the sap of “Rieti’ ’ wheat is more acid than 
that of any other Italian wheat. This variety is particularly resistant 
to rust. Kirchner (27) and Henning ( 22 ) also call attention to the 
importance of high acidity of the cell sap in resistance to rust. Gortner 
(17) reports that excess fertilization with sodium nitrate decreased the 
hydrogen-ion concentration in Haynes Bluestem wheat. Grimaldi (ip) 
and Hurd (24) question the importance of the acidity of the cell sap in 
resistance of wheat to rust, pointing out that there is no positive cor¬ 
relation between the two. The latter shows that environmental con¬ 
ditions may cause greater differences in the acidity of the cell sap of a 
single variety than usually occur between different varieties grown under 
the same conditions. Pantanelli (39) states that the organs of the 
wheat plant most susceptible to rust are those richest in sugars, acids, 
and in soluble compounds of phosphorus and nitrogen. 
Mains (32) and others have shown that the carbon metabolism of the 
host is important in the development of rust. Kirchner (27) and Hen¬ 
ning (22) give tables of the sugar content of the saps of resistant and 
susceptible varieties. These tables indicate that the concentration of 
glycose or reducing sugars is higher in the more susceptible varieties. 
EXPERIMENTAL BATA 
Studies have been made on the entrance of germ tubes of Puccinia 
graminis into the host, the morphology of the wheat plant as related to 
rust resistance, the relation of nutrient salts to the development of stem 
