196 1. MALONATE 



bition produced by ^ra ws-aconitate. The injection of 50 milf malonate into 

 the leaf petioles, however, increases infectivity so that a more significant 



effect on the host tissue is evident. The development of Puccinia rust on 

 wheat seedling leaves is inhibited by 10 mM malonate, but the leaf tissue 

 is damaged (Samborski and Forsyth, 1960). In this particular case the 

 phytotoxicity is greater than the rust suppression so that malonate could 

 not be used commercially. Malonate esters have been tested for inhibition 

 of mold growth in syrups, but 13 mM does not have much effect over 144 hr 

 (Lord and Husa, 1954); however, these esters are used as fungistatic agents 

 in soy sauce in Japan (Tsukamoto, 1951). Another instance of growth stim- 

 ulation by malonate was reported for Endamoeba histolytica (Nakamura 

 and Baker, 1956); the average cell count per field at the end of 3-4 days 

 was 1 in the control and 16 in the presence of 12.8 mM malonate, indicating 

 possible metabolism of the malonate by these organisms. 



Plant Growth 



Avena coleoptile growth is sometimes stimulated and sometimes depressed 

 by malonate, the response depending on the strain of oats used, the pH, 

 and whether the sodium or potassium salt of malonate is used. The marked 

 inhibition (61%) reported by Commoner and Thimann (1941) for 10 mM po- 

 tassium malonate over 24 hr has not been observed by others. Albaum and 

 Eichel (1943) found only stimulation (around 30%) from 1-5 niM potassium 

 malonate over a period of 160 hr, and it was felt that malonate was serving 

 as a substrate, which was substantiated by the higher respiration in the 

 presence of malonate. Thimann and Bonner (1948) provided further evi- 

 dence for this by the finding that malonate at 1 mM, having little effect by 

 itself, antagonizes the marked inhibition produced by iodoacetate. How 

 much of this is due to malonate and how much to potassium is difficult 

 to say. Cooil (1952) confirmed the counteraction of iodoacetate inhibition 

 by potassium malonate, but found that the sodium salt is not nearly as 

 potent, implicating the potassium ion. The failure of malonate to inhibit 

 the growth is probably the result of poor penetration, as shown by the 



