Studies on the Physiology of Host‐parasite Relationship in Orobanche. III. Carbohydrate and Nitrogen Metabolism of Host and Parasite

Abstract

Determination of different carbohydrate and nitrogen fractions was made in tomato (Lycopersicum esculentum Mill.) and mustard (Brassica campestris L.) serving as hosts for Orobanche cernua and O. aegyptiaca respectively. Shoots of Orobanche were also subjected to such analyses. Infection raised the level of total reducing and total sugar in the host with a simultaneous decrease in the level of acid‐hydrolyzable and total carbohydrates in the constituent organs of infected hosts. This has been explained to be due to predominance of hydrolytic activity in the infected host. Infection also brought about a depression in the proportion of sucrose to the pool of total sugar in the host. This was also possibly due to predominance of hydrolytic processes and retardation in the synthetic processes. Higher concentration of acid‐hydrolyzable and total carbohydrates in Orobanche than in the host indicated a high demand for sugars by the parasite. The insignificant differences between the relative proportions of different nitrogen fractions to the pool of total nitrogen in healthy and infected hosts indicated that nitrogen metabolism was not deranged in any way due to infection. Orobanche always had a lower concentration of total soluble and total nitrogen than the host root.

Effects of Light Level and Nitrogen Supply on the Red Clover–Orobanche Minor Host–Parasite Interaction

“…However, our soluble sugar data showed the opposite trend, with parasitised plants exhibiting significantly higher concentrations than controls. The reason for this is not clear, but similar increases in soluble sugar levels have also been found in tomato plants parasitised by O. cernua [26]. It is plausible that these elevated soluble sugar concentrations are a result of reduced sugar loading into the phloem, or a strategy to shift the plants’ osmotic balance towards the leaves.…”

Growth, Yield and Chemical Composition of Rosemarinus Officinalis L. Plant as Affected With Sulphur, Nitrogen and Phosphorus Fertilization Under Saline Water Irrigation

“…2.1-Sulphur fertilizer was added to the soil, after rooting of the cuttings at three different concentrations as follows 23.7, 47.4 Total carbohydrate percent and total soluble sugars in the dried material were determined according to Dubois et al, (1956). Reducing sugars were determined according to Nelson's calorimetric method (1944), and sucrose was calculated according to the following equation mentioned by Singh et al, (1972) as follows Sucrose = (total soluble sugarstotal reducing sugars) x 0.95 Total nitrogen, Potassium and phosphorus were determined (on a dry matter basis) according to (Jackson, 1985). Sulphur was determined according to Dewis and Freitas (1970).…”

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“…Orobanche species also vary in their potential to cause damage since morphology, height/stature, infection ability varies across the species. Singh et al (1972) reported higher concentrations of acid-hydrolyzable and total carbohydrates in Orobanche than the host caused higher demand for sugars by the parasite (Singh et al 1972). Orobanche always had a lower concentration of total soluble and total nitrogen than the host root.…”