Reyhaneh Pordel, Masoud Esfahani, Mohammad Kafi, Ahmad Nezami
Department of Agronomy Faculty of Agriculture, Ferdowsi university of Mashhad, Mashhad, Iran
Department of Agronomy and Plant Breeding, Faculty of Agriculture Sciences, University of Guilan, Rasht, Iran
Key words: Stevia; Root Surface Area Density; Root volume and hypoxi.
This research studied the effect of waterlogging level and duration, nitrogen fertilizer and terminal drought stress on root and shoot growth of Stevia. Treatments included four waterlogging levels; (0, -5, -10 cm from soil surface and with normal irrigation as control), in periods of 2 and 4 days of waterlogging, two levels of nitrogen (6‰ and 0) from source of urea and two levels of terminal drought stress. Results showed measured root and shoot traits include root dry weight, root length, root area, root volume, root length density, root surface area density, dry root mass density, root diameter, leaf area, plant height, number of SPAD, number of lateral shoot, number of leaves were significantly different among treatments. Root dry weight, root length and root volume in -10 waterlogging level treatment( 16.24 g, 24.8 cm and 27.7 ml, respectively) and in fertilizer treatment (17.9 g, 25.5 cm and 22.1 ml, respectively) shown the least decrease. Moreover, interaction between drought stress treatment and nitrogen fertilizer for root dry weight and root length (18.4 g and 26.5 cm, respectively)and in shoot traits, number of leaves, leaf area and plant height (237, 64.07 cm2 and 87 cm) showed the minimum difference with control treatments. Generally, the results of this experiment showed that increase of waterlogging either level or duration decrease the amount of root and shoot characteristics. Nitrogen fertilizer resulted in higher root and shoot traits in applying treatment. By contrast, terminal drought stress led to decrease in all root and shoot traits.