| Huang Kum Pear (Pyrus pyrifolia Nakai) belongs to the family Rosaceae. It is a new variety introduced from South Korea to China. The fruit is becoming famous by its high quality like good appearance and delicious taste. So, it has high potential to develop. The area under cultivation is 219.1khm~2 and 1042.4 khm~2 in Hebei and China respectively. Whereas production of Hebei is 255.2mt and China is 930.9mt. Hebei has been contributing 22.9% production of the China. Thus, in the recent years, there has been growing problem of the shortage of fruit production for consumers in the country. Whereas salicylic acid (SA) is an important signal substance, known as a new phytohormone, classified as endogenous plant growth regulator and disease resistance. It has been established that the substance is widely distributed in the plants. Relationship of SA with senescence in this fruit was not very clear. So, influence of SA on different physiological indexes of the pear fruit for delaying senescence was analyzed in this experiment while considering SA might be useful for availability of fruit produce throughout the year. The results are as follows.1. Results revealed, SA significantly enhanced maximum SOD and POD activity by 57.46% and 25% than control at 0.02mmol/L 4hrs and 0.002mmol/L 12 hrs dip while reducing MDA contents by 82.86% at 0.002mmol/L 12 hrs dip respectively. Perhaps controlling the level of lipid peroxidation and improving defensive mechanism in tissues. However, some of SA concentrations 2, 0.02, 0.2mmol/L 24hrs, decreased POD activity than ck to damaging level and treatments within 24 hrs showed non-significance difference for MDA contents indicating precarious situation. So, as concerned for SOD enzymeactivity the situation expressed, shorter dip duration with lower SA concentration found effective and, for POD and MDA contents lower concentration with longer dip time remained better than others.2. Data portrayed that activity of cell wall hydrolytic enzymes PME, PG and senescence controlling enzyme LOX were significantly inhibited at SA 0.002mmol/L 12hrs, 0.02mmol/L 4hrs and, 0.2 & 2.0mmol/L for 4 hrs dip than control by 20.56%, 38.89% and 34.25% among other treatments while reducing cell wall pectin degradation. These enzymes also presented precarious situation like PME indicated non-significant results within all the treatments of 4 and 24hrs dip, PG expressed accelerated activity by 0.2 and 2.0mmol/L SA for all dip hrs and, LOX showed increased activity by 0.002mmol/L 12hrs and 0.2mmol/L 24hrs dip, perhaps causing loss of fruit by cell wall deterioration. The data revealed that for PME lower SA concentration with longer dip time, for PG lower concentration with shorter dip hours and for LOX higher concentration with shorter dip time presented better results than others.3. Observations indicated, significantly the highest concentration of SA was 2.0mmol/L with 12hrs dip of fruit discs, inhibited maximum ethylene gas production by 75.51% as compared to control valued 0.147 ul /g, converting ACC to ethylene by ACC oxidase in fruit tissue. Although for other SA concentrations ethylene inhibition positive but these were lesser than above SA level. In the experiment, fruit discs were dip for 12hrs in different SA concentrations like 0.002, 0.02, 0.2, 2.0mmol/L and control was distilled water. Hence, overall results suggested that the highest concentration of SA was found to be the best treatment.4. Data regarding this factor revealed as SA concentration improved to the highest level, respiration of fruit discs was strongly inhibited. The highest treatment 2.0mmol/L for 24, 4, 12 hrs dip, reduced respiration up to lowest level of 95.23, 85.41% 75.74% in sequence respectively. Whereas for 12 hrs at 0.02mmol/L results were negative as compared to ck. SA also inhibited respiration peak in fruit by keeping slow the metabolic rate. As results showed, higher the SA concentration, lesser the respiration rate than ck.
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