Volume 35, Issue 3
March 1952, pages 111-142
pp 111-121 March 1952
pp 122-131 March 1952
Studies in the physiology of phanerogamic parasitism with special reference toStriga lutea, Lour. andS. Densiflora, Benth. onAndropogom sorghum, Hack - I. The osmotic pressure of the host and parasite in relation to the nutrition of the host
While studying the influence of nutrition of the host on the susceptibility ofAndropogon sorghum to attack by the phanerogamic root-parasitesStriga lutea andS. densiflora, the host along with the parasites were grown in sand cultures watered by four different concentrations of the same nutrient solution for a period of nearly five months,i.e., from sowing to harvest. These studies were utilised for testing the ability of the parasite to adjust its osmotic pressure to that of the host.
From the results obtained it was found that the severity of attack was the highest at the lower concentration and lowest at the higher concentration of the nutrient solution. Similarly the damage done byStriga plants as determined by the reduction in yield of grain of theSorghum plants was the greatest at the lower concentrations. The differences in yields of straw were not significant.
The osmotic pressures of the leaves ofSorghum plants, attacked byS. lutea andS. densiflora and freeSorghum plants were determined by the plasmolytic method. The osmotic values of the leaves of the parasites were measured at the same time. It was found that the osmotic pressure of the parasite was always much greater than its host at the lower concentrations but at the highest concentration, the host and parasite have practically the same osmotic pressure.
pp 132-142 March 1952
Vitamin C and Vitamin C-Cu complex inhibit urease activity, the inhibition being very marked in the latter case.
The inhibition of urease activity of Vitamin C is not due to dehydro-ascorbic acid as the degree of inhibition produced by it is negligible compared to that produced by Vitamin C at equal concentration.
A variety of compounds other than cysteine, like 8-hydroxy-quinoline, sodium-diethyl-dithio-carbamate and potassium cyanide, which are known to protect Vitamin C against oxidation catalysed by Cu++, are shown to protect the urease from inactivation by Vitamin C and Vitamin C-Cu. showing that the inactivation of urease by Vitamin C is related to the oxidation of the vitamin.
A well marked correlation between the inactivation of urease on the one hand and the oxidation of Vitamin C on the other has been established.
It is suggested that the inactivation of urease by Vitamin C catalyzed by Cu++ may be due to any intermediate products like Cu2O formed during the oxidation.