Effect of Urea and Nano-nitrogen Spray Treatments on Some Citrus Rootstock Seedlings.

A factorial experiment was conducted during two consecutive seasons (2020 –2021( and (2021–2022) using seedlings of Volkamerlemon (Citrus volkameriana) and Sour orange (Citrus aurantium L.) potted in the citrus seedling nursery of Horticulture Research Institute, Giza, Egypt. Two nitrogen sources (urea & nano particles) each at 2 concentrations (500 & 750 ppm) and water spray were foliar sprayed three times at one month interval. Obtained results revealed that various growth parameters (plant height, stem diameter, no. of leaves, leaf area, fresh & dry weights of three plant parts)and Chemical analysis (leaf total free amino acids, photosynthetic pigments, leaf  protein electrophoresis, N, Pand K contents)have responded differently to each of the investigated factors (N spray treatments or rootstock) or to both (interaction effect).Anyhow, except for leaf area, Volkamerlemon growth parameters were superior and its leaves had richer chlorophyll, a & b contents. Meanwhile, Sour orange leaf chemical components (carotenoids, free amino acids, N, P, and K %) revealed the superiority. Moreover, four N solutions significantly increased all growth measurements and leaf chemical composition (except P %) over control. The specific effect of both investigated factors reflected directly on their interaction effects. Therefore, higher N concentration regardless of source caused Volkamer lemon growth characteristics to be superior. While the richest leaf chemical contents resulted from Sour orange leaves sprayed with 750 mg/L N. The total numbers of generated bands across the three treatments of each rootstock were thirteen. Herein, with Sour orange 9 bands were common (monomorphic), while 4 other ones were unique Polymorphic with 30.8% polymorphism, whereas 3 of them were negative and only one was positive. As for Volkamer lemon eleven bands from the 13 generated ones were monomorphic and two other ones were Polymorphic with 15.38% Polymorphism, one of them was negativeand other was positive.