Browsing by Author "Sesay, Abu Dim Din"

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Cyanide-Resistant Respiration in Light- and Dark-Grown Soybean Cotyledons
(Oxford University Press, 1988-07-01) Sesay, Abu Dim Din
Measurements of respiration were made on intact tissue and mitochondria isolated from soybean (Glycine max \[L.\] Merr. cv ;Corsoy') cotyledons from seedlings of different ages grown in light and darkness. Effects of cyanide (KCN) and salicylhydroxamic acid (SHAM) on O(2) uptake rates were determined. O(2) uptake was faster in light-grown tissue and was inhibited by both KCN and SHAM in all except light-grown tissue older than 9 days. Both inhibitors stimulated O(2) uptake in tissues more than 9 days old. Mitochondria in which O(2) uptake was coupled to ATP synthesis were isolated from all tissues. O(2) uptake by mitochondrial preparations from light- and dark-grown cotyledons was equally sensitive to KCN. Similarly, age did not affect KCN sensitivity, but sensitivity to SHAM declined with age both in the presence and absence of KCN. Estimated capacities of the cytochrome and alternative pathways of the mitochondrial preparations indicated considerably larger cytochrome than alternative pathway capacities. The cytochrome pathway capacities paralleled the state 3 mitochondrial respiration rates, which increased from day 5 to day 7 then declined thereafter. The alternative pathway capacities were not affected by light. The uncoupler, p-trifluoromethoxycarbonylcyanide phenylhydrazone (FCCP), increased the flow of electrons through the cytochrome pathway at the expense of flow through the alternative pathway in isolated mitochondria. However, the combined capacities did not exceed the rate in the presence of FCCP. The results are interpreted to indicate that the stimulation of respiration by KCN and SHAM observed in the 12-day-old green cotyledons and previously observed in older soybean leaves is not explained by characteristics of the mitochondria.
Effects of KCN and Salicylhydroxamic Acid on Respiration of Soybean Leaves at Different Ages
(Oxford University Press, 1986-10-01) Sesay, Abu Dim Din
Measurements of respiration were made on leaf discs from glasshouse-grown soybean (Glycine max \[L.\] Merr. cv ;Corsoy') plants in the presence and absence of cyanide (KCN) and salicylhydroxamic acid (SHAM). O(2) uptake by mature leaves measured at 25 degrees C was stimulated by 1 millimolar KCN (63%) and also by 5 millimolar azide (79%). SHAM, an inhibitor of the alternative oxidase and a selection of other enzymes, also stimulated O(2) uptake by itself at concentration of 10 millimolar. However, in combination, KCN and SHAM were inhibitory. The rate of O(2) uptake declined consistently with leaf age. The stimulation of O(2) uptake by KCN and by SHAM occurred only after a certain stage of leaf development had been reached and was more pronounced in fully expanded leaves. In young leaves, O(2) uptake was inhibited by both KCN and SHAM individually. The uncoupler, p-trifluoromethoxy carbonylcyanide phenylhydrazone, stimulated leaf respiration at all ages studied, the stimulation being more pronounced in fully expanded leaves. The uncoupled rate was inhibited by KCN and SHAM individually. The capacity of the cytochrome path declined with leaf age, paralleling the decline in total respiration. However, the capacity of the alternative path peaked at about full leaf expansion, exceeding the cytochrome capacity and remaining relatively constant. These results are consistent with the presence in soybean leaves of an alternative path capacity that seems to increase with age, and they suggest that the stimulation of O(2) uptake by KCN and NaN(3) in mature leaves was mainly by the SHAM-sensitive alternative path. The stimulation of O(2) uptake by SHAM was not expected, and the reason for it is not clear.
Handbook of plant and crop physiology
(Elsevier BV, 1995-10-01) Sesay, Abu Dim Din
Plant infection and yield loss associated with cercospora leaf spots of groundnut (Arachis hypogaeaL.) in Sierra Leone
(Taylor & Francis, 1992) Sesay, Abu Dim Din
Infection and yield loss induced by groundnut leaf spots were determined with benomyl during the 1989 and 1990 crop seasons under natural disease pressure in the field in Sierra Leone. Weather conditions in both years were highly favourable to leaf spot infection and development. In 1989 benomyl, applied at weekly intervals and at the rate of 0.15 kg a.i. ha−1 for a total of 10 applications, effectively controlled leaf spots and increased both pod and haulm yields by 85%. An estimated potential pod yield loss of 46% was recorded, indicating the importance of the diseases as major constraints to groundnut production in Sierra Leone. In 1990, however, a higher level of leaf spots severity was observed causing extensive damage of the foliage. Benomyl, applied at bi‐weekly intervals and at the rate of 0.225 kg a.i. ha−1 for a total of five applications failed to effectively control the diseases, increasing pod yield by only 27%.