Responses of semi-vigorous apple rootstocks (MM106 and MM111) to different nitrate and ammonium ratios under soilless culture

Abstract

In this study, the effects of nitrate (NO₃⁻) to ammonium (NH₄⁺) ratios on vegetative growth parameters, mineral uptake, physiological and biochemical responses of two semi-vigorous apple rootstocks (MM106 and MM111) in hydroponically grown under greenhouse conditions were evaluated. Treatments were five nutrient solutions of differing NO₃⁻:NH₄⁺ ratios as follows (100:0, 80:20, 60:40, 40:60, 20:80) and two apple rootstocks. After 120 days of treatment, parameters were determined. The NO₃⁻:NH₄⁺ ratios significantly affected the vegetative growth of MM106 and MM111 rootstocks. Rootstocks fertilized with a high NH₄⁺ ratio produced larger leaves, longer roots, stems, and diameter, while the plants under NO₃⁻ treatment alone had smaller and shorter roots. N-form significantly influenced the uptake and utilization of essential plant nutrients in both rootstocks. Leaf concentrations of nitrogen (N), potassium (K), and calcium (Ca) were highest with NO₃⁻. Leaf concentrations of phosphorous (P), magnesium (Mg), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) increased as NH₄⁺ supplied more of the N-ratio. The highest chlorophyll a and b and total chlorophyll were observed at the 20:80 NO₃⁻:NH₄⁺ ratio. In comparison, the lowest content was at the highest dose of NO₃⁻ (100:0) treatment. The highest soluble sugars were obtained in the leaves of MM106 and MM111 at the ratio of 80:20. Soluble sugars in the root of both rootstocks decreased by increasing the NH₄⁺ ratios in the nutrient solution. Our results show that supplying rootstocks with high NO₃⁻ as N form can affect vegetative growth and mineral uptake at this stage of growth.

Keywords:

• Chlorophyll
• MM106
• nitrogen
• soluble sugars
• vegetative growth

Acknowledgments

We would like to thank Urmia University for financial support and Academic Center for Education, Culture and Research (ACECR), for providing apple rootstocks.

Disclosure statement

No potential conflict of interest was reported by the authors.

Credit authorship contribution statement

Conceptualization, Investigation, Formal Analysis, Writing -Original Draft, Visualization, Software, Data Curation, Writing - Review & Editing., Project administration, Methodology, Validation, Resources, Supervision, Funding Acquisition.