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Not AvailableThe study showed that application of different doses of inorganic nutrients had considerable influence on growth, yield and downy mildew interaction in isabgol (Plantago ovata). It included three levels of nitrogen (0, 30, 60 kg N ha−1), two levels of phosphorous (0, 30 kg P ha−1) and two levels of potash (0, 40 kg K ha−1) for 2 consecutive years. The highest N supply (60 kg ha−1) caused more than 65% increase in disease severity compared with the control. However, application of 40 kg K ha−1 reduced percent disease index (PDI) by more than 10% compared with 0 kg K ha−1 treatment. Seed yield was influenced by N but not by P or K. In both years, the highest seed yield was obtained from 60 kg N ha−1. Total sugar concentration in leaf tissue increased with the application of N, but the concentration of phenol and OD phenol decreased. On the other hand, growth of the plant was positively influenced by N. As a result, leaf area index (LAI) increased by 40.91% and 51.01% compared with the control when 30 and 60 kg N ha−1, respectively, were applied. Leaf chlorophyll content and net photosynthesis also increased in the N-treated plants. Seed yield and disease reaction to different fertiliser treatments are discussed in relation to the different physiological and biochemical parameters studied.Not Availabl

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Not AvailablePlantago ovata is commercially grown in India for its dietary fibre. The crop is affected by downy mildew caused by Peronospora plantaginis Underwood leading to severe yield loss. A study was undertaken to assess the impact of downy mildew on host photosynthesis under field conditions. The results showed that primary photosynthetic pigments (total chlorophyll) were reduced by 34.74% and 62.11% in slight and severe chlorotic leaves, respectively, compared to healthy leaves. Net photosynthetic rate (Pn) was also significantly reduced in diseased leaves. The diurnal photosynthesis measurement showed that peak Pn in the diseased leaves was short lived as compared to healthy leaves. Infection caused an increase in dark respiration (Rd) and intracellular CO2 concentration (Ci), while stomatal conductance (gs) was similar to that of healthy leaves during peak photosynthetic period of the day. Infection caused a reduction in soluble sugar content accompanied by an increase in leaf starch content. Vitality index (Fv/Fm) of the diseased leaves was reduced by 24.39% in slight chlorotic and 44.90% in severe chlorotic leaves as compared to healthy leaves. Further, quantum yield of photosystem (PS) II (FPSII) showed severe reduction, which was correlated with the Pn. Our study suggests that carbon assimilation in the diseased leaves is mainly limited by PSII function. Disease induced reduction in chlorophyll content appears to be one of the causes for reduction in PSII yield. Increase in starch accumulation in infected leaves appears to be a cause for reduction in photosynthesis in infected leaves.Not Availabl