عنوان مقاله [English]
ABSTRACT To study the effect of defoliation stress and nitrogen on some quantitative and qualitative characteristics of filed pumpkin an experiment was conducted at Tarbiat Modares University Research Field of Agriculture Faculty. Three levels of defoliation including 0, 50 and 100% and three levels of plant nitrogen fertilizing including 50, 100 and 150 kg/h were studied in a randomized complete block design in three replications with factorial arrangement. Defoliation in the milky stage and of nitrogen fertilizers in two equal split applications were applied at two-leaf and flowering stages. Harvesting was carried out in mid of October. Fruit and grain weight, grain length, width and diameter, oil content, fatty acids linoleic, oleic, palmitic and stearic were evaluated. Grain morphological characteristics were influenced by nitrogen fertilization. Using of excessive nitrogen fertilizer had no positive effect on studied traits. The effect of defoliation stress on fruit and grain weight, grain width and diameter were highly significant (P ≤0.01). Under stress conditions, the highest percentages of linoleic, oleic, palmitic and stearic acid were achieved as 5.44, 3.28, 2.17 and 2.5%, respectively and also the minimum amount of those in complete defoliation were observed as 41, 24.9, 14.5, and 4.25%, respectively. On the whole, removal of photosynthesis unit by reducing production, production disruptions and assimilates allocation, was significantly reduced between different parts of the plant's production. increased levels of fertilizer did not increase yield. Nitrogen fertilizer in 50 kg/ha and no defoliation treatments have been recommended as the most suitable treatments for access to maximum seed yield.