Impact of Cultivar and Grafting on Nutrient and Water Uptake by Sweet Pepper (Capsicum annuum L.) Grown Hydroponically Under Mediterranean Climatic Conditions

Andreas Ropokis; Georgia Ntatsi; Constantinos Kittas; Nikolaos Katsoulas; Dimitrios Savvas

doi:10.3389/fpls.2018.01244

Impact of Cultivar and Grafting on Nutrient and Water Uptake by Sweet Pepper (Capsicum annuum L.) Grown Hydroponically Under Mediterranean Climatic Conditions

Front Plant Sci. 2018 Aug 24:9:1244. doi: 10.3389/fpls.2018.01244. eCollection 2018.

Authors

Andreas Ropokis¹, Georgia Ntatsi^{1

2}, Constantinos Kittas³, Nikolaos Katsoulas³, Dimitrios Savvas¹

Affiliations

¹ Laboratory of Vegetable Production, Department of Crop Science, Agricultural University of Athens, Athens, Greece.
² Institute of Plant Breeding and Genetic Resources, Hellenic Agricultural Organization - ELGO DEMETER, Thessaloniki, Greece.
³ Laboratory of Agricultural Constructions and Environmental Control, Department of Agriculture Crop Production and Rural Environment, School of Agricultural Sciences, University of Thessaly, Volos, Greece.

Abstract

In closed-cycle hydroponic systems (CHS), nutrients and water should be delivered to the plants at identical ratios to those they are removed via plant uptake, to avoid their depletion or accumulation in the root zone. For a particular plant species and developmental stage, the nutrient to water uptake ratios, henceforth termed "uptake concentrations" (UC), remain relatively constant over time under similar climatic conditions. Thus, the nutrient to water uptake ratios can be used as nutrient concentrations in the nutrient solution (NS) supplied to CHS to compensate for nutrient and water uptake by plants. In the present study, mean UC of macro- and micronutrients were determined during five developmental stages in different pepper cultivars grown in a closed hydroponic system by measuring the water uptake and the nutrient removal from the recirculating NS. The experiment was conducted in a heated glasshouse located in Athens Mediterranean environment and the tested cultivars were 'Orangery,' 'Bellisa,' 'Sondela,' 'Sammy,' self-grafted and 'Sammy' grafted onto the commercial rootstock 'RS10' (Capsicum annuum). 'Sondela' exhibited significantly higher NO₃^-, Mg²⁺, Ca²⁺ and B UC, while Bellisa exhibited higher K UC in comparison with all other cultivars. The UC of all nutrients were similar in the grafted and the non-grafted 'Sammy' plants, which indicates that this Capsicum annum rootstock does not modify the uptake of nutrients and water by the scion. The UC of macronutrients estimated in the present study (mmol L^-1) ranged from 2.4 to 3.7 for Ca, 1.0 to 1.5 for Mg, 6.2 to 9.0 for K, 11.7 to 13.7 for N, and 0.7 to 1.1 for P. The UC of N, K, Ca, and Mg were appreciably higher than the corresponding values found in Dutch tomato glasshouse, while that of P was similar in both locations during the vegetative stage and higher in the present study thereafter. The UC of Fe, Zn and B tended to decrease with time, while that of Mn increased initially and subsequently decreased slightly during the reproductive developmental stage.

Keywords: bell pepper; calcium; iron; magnesium; rootstock; scion; soilless culture.