الفهرس 
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Abstract
The objective of this study was to investigate the effects of two nitrogen fertilizers (potassium nitrate and / or urea) on shoot and root growth parameters as well as some metabolic activities of (Vigna sinensis) and Helianthus annuus plants, throughout two vegetative stages. Whereas, transmission electron microscopy for mature leaves for plants was also carried out but at the second vegetative stage only. During the two vegetative stages of cowpea growth, there was a non-significant decrease in shoot parameters in response to 100% urea and 50% potassium nitrate + 50% urea treatments, & 100% potassium nitrate +100%urea treatments at first stage, in leaves area in response to 100% potassium nitrate & 100% urea treatments at second vegetative stage, whereas the other treatments induced a general significant increase in the all tabulated growth parameters as compared to control values. During the two vegetative stages of Helianthus annuus L. growth, a general significant increase in the all tabulated shoot growth parameters in response to the all used treatment as compared to control values. Total chlorophyll and total pigments were increased by the used treatments at first stage of cowpea growth while these parameters were decreased during the second stage and vice versa in case of sunflower plant. In most cases, the determined carbohydrates increased by the used nitrogen treatments during the two vegetative stages of the used plants (cowpea & sunflower). The treatment with 100% potassium nitrate + 100% urea caused a non-significant decrease in the all determined shoot nitrogen fractions. The other treatments led to a general significant increase in the shoot nitrogen fractions at first vegetative stage of cowpea plant as compared to control values. During second vegetative stage of Vigna sinensis L. growth, except for the observed non-significant increase in the all determined shoot nitrogenfractions in response to treatment with 50% potassium nitrate + 50% urea, the other treatments induced a significant decrease in all determined shoot nitrogen fractions as compared to control values (Table 4).Throughout the two vegetative stages of sunflower plant growth, ageneral significant increase in the all determined shoot nitrogen fractions in response to the all used treatment as compared to control values (Table 10). At first vegetative stage of cowpea plant growth, except for the observed significant decrease in total nitrogen, total protein, total soluble nitrogen andphosphorus (in response to treatment with 50% potassium nitrate + 50% urea), the other treatments induced a general significant increase in all nitrogen fraction and phosphorus as compared to control values (Table 5). During second vegetative stage of vigna sinensis L. growth, except for the observed non-significant decrease in the phosphorus in response to treatment with 100% urea &100% potassium nitrate + 100% urea, the other treatments induced asignificant increase in all nitrogen fraction and phosphorus ascompared to control values (Table 5). 15 The obtained results in table (11) showed that, during the first vegetative stages of Helianthus annuus L.growth, the all used treatments induced asignificant decrease in total nitrogen, total protein, total soluble nitrogen & phosphorus in root as compared to control values. At second vegetative stage, except for the significant decrease in total nitrogen, total protein & total soluble nitrogen response to 100% potassium nitrate and in response to 50% potassium nitrate + 50% urea (phosphorus), the other treatments induced a general significant increase in the all nitrogen fraction and phosphorus as compared to control values (Table 11).The treatment with 100% potassium nitrate + 100% urea caused a non- significant decrease in the all determined shoot nitrogen fractions. The other treatments led to a general significant increase in the shoot nitrogen fractions at first vegetative stage of cowpea plant as compared to control values. During second vegetative stage of Vigna sinensis L. growth, except for the observed non-significant increase in the all determined shoot nitrogen fractions in response to treatment with 50% potassium nitrate + 50% urea, the other treatments induced a significant decrease in all determined shoot nitrogen fractions as compared to control values (Table 4). Throughout the two vegetative stages of sunflower plant growth, ageneral significant increase in the all determined shoot nitrogen fractions inresponse to the all used treatment as compared to control values (Table 10). At first vegetative stage of cowpea plant growth, except for the observedsignificant decrease in total nitrogen, total protein, total soluble nitrogen and phosphorus (in response to treatment with 50% potassium nitrate + 50% urea),the other treatments induced ageneral significant increase in all nitrogen fraction and phosphorus as compared to control values (Table 5). During second vegetative stage of vigna sinensis L. growth, except for the observed non-significant decrease in the phosphorus in response to treatment with 100% urea &100% potassium nitrate + 100% urea, the other treatments induced a significant increase in all nitrogen fraction and phosphorus ascompared to control values (Table 5). The obtained results in table (11) showed that, during the first vegetative stages of Helianthus annuus L. growth, the all used treatments induced asignificant decrease in total nitrogen, total protein, total soluble nitrogen & phosphorus in root as compared to control values. At second vegetative stage, except for the significant decrease in total nitrogen, total protein & total soluble nitrogen response to 100% potassium nitrate and in response to 50% potassium nitrate + 50% urea (phosphorus), the other treatments induced a general significant increase in the all nitrogenfraction and phosphorus as compared to control values (Table 11).•The treatment with 100% potassium nitrate + 100% urea caused a non- significant decrease in the all determined shoot nitrogen fractions. The other treatments led to a general significant increase in the shoot nitrogen fractions at first vegetative stage of cowpea plant as compared to control values. During second vegetative stage of Vigna sinensis L. growth, except for the observed non-significant increase in the all determined shoot nitrogen fractions in response to treatment with 50% potassium nitrate + 50% urea, the other treatments induced a significant decrease in all determined shoot nitrogen fractions as compared to control values (Table 4).Throughout the two vegetative stages of sunflower plant growth, ageneral significant increase in the all determined shoot nitrogen fractions in response to the all used treatment as compared to control values (Table 10).At first vegetative stage of cowpea plant growth, except for the observed significant decrease in total nitrogen, total protein, total soluble nitrogen and phosphorus (in response to treatment with 50% potassium nitrate + 50% urea), the other treatments induced a general significant increase in all nitrogen fraction and phosphorus as compared to control values (Table 5). During second vegetative stage of vigna sinensis L. growth, except for the observed non-significant decrease in the phosphorus in response to treatment with 100% urea &100% potassium nitrate + 100% urea, the other treatments induced a significant increase in all nitrogen fraction and phosphorus as compared to control values (Table 5). 15•The obtained results in table (11) showed that, during the first vegetative stages of Helianthus annuus L. growth, the all used treatments induced asignificant decrease in total nitrogen, total protein, total soluble nitrogen & phosphorus in root as compared to control values. At second vegetative stage, except for the significant decrease in total nitrogen, total protein & total soluble nitrogen response to 100% potassiumnitrate and in response to 50% potassium nitrate + 50% urea (phosphorus), the other treatments induced a general significant increase in the all nitrogen fraction and phosphorus as compared to control values (Table 11).The treatment with 100% potassium nitrate + 100% urea caused a non- significant decrease in the all determined shoot nitrogen fractions. The other treatments led to a general significant increase in the shoot nitrogen fractions atfirst vegetative stage of cowpea plant as compared to control values. During second vegetative stage of Vigna sinensis L. growth, except forthe observed non-significant increase in the all determined shoot nitrogen fractions in response to treatment with 50% potassium nitrate + 50% urea, the other treatments induced a significant decrease in all determined shoot nitrogen fractions as compared to control values (Table 4). Throughout the two vegetative stages of sunflower plant growth, ageneral sign response to the all used treatment as compared to control values (Table 10). At first vegetative stage of cowpea plant growth, except for the observed significant decrease in total nitrogen, total protein, total soluble nitrogen and phosphorus (in response to treatment with 50% potassium nitrate + 50% urea), the other treatments induced a general significant increase in all nitrogen fraction and phosphorus as compared to control values (Table 5). During second vegetative stage of vigna sinensis L. growth, except for the observed non-significant decrease in the phosphorus in response to treatment with 100% urea &100% potassium nitrate + 100% urea, the other treatments induced asignificant increase in all nitrogen fraction and phosphorus as compared to control values (Table 5). 15 The obtained results in table (11) showed that, during the first vegetative stages of Helianthus annuus L. growth, the all used treatments induced asignificant decrease in total nitrogen, total protein, total soluble nitrogen & phosphorus in root as compared to control values. At second vegetative stage, except for the significant decrease in total nitrogen, total protein & total soluble nitrogen response to 100% potassium nitrate and in response to 50% potassium nitrate + 50% urea (phosphorus), the other treatments induced a general significant increase in the all nitrogenfraction and phosphorus as compared to control values (Table 11).The treatment with 100% potassium nitrate + 100% urea caused a general non- significant decrease in the all determined shoot nitrogen fractions ,on the other hand the treatment with 50% potassium nitrate + 50% urea led to a general significant increase in these fractions during two vegetative stages of cowpea plant as compared to control values. Throughout the two vegetative stages of sunflower plant growth, a general significant increase in the all determined shoot nitrogen fractions in response to the all used treatments as compared to control values. Concerning the starch granules, the examination of the ultrastructure changes in cowpea leaves cleared the presence of two starch granules in response to 100% potassium nitrate and 100% potassium nitrate + 100% urea treatment also detected in the control. On the other hand disappearance of the starch granules in response to 100% urea as well as increment of starch to three granules in response to 50% potassium nitrate + 50% urea was detected. Despite of the starch granules non detected in the leaves of the untreated sunflower the treated leaves showed appearance of starch granules which have the highest number by 50% potassium nitrate + 50% urea and the most volume with 100% potassium nitrate. The result of this study demonstrated that, nitrogen fertilizers has an overall positive influence on growth, photosynthetic pigments , sugars and nitrogen fractions especially in case of using (50% potassium nitrate + 50% urea) and the magnitude of response was more pronounced in case of cowpea plant.