Inorganic solute accumulation in noni (Morinda citrifolia Linn) under salt stress during initial growth

Noni (Morinda citrifolia) is a fruit species which is well adapted to different soil and climate conditions, and may be a good option for farmers in arid and semi-arid regions. To evaluate the tolerance of noni plant in the initial phase to salinity and the accumulation of inorganic solutes in its organs, an experiment was carried out in a greenhouse under hydroponic system. The experimental design was completely randomized, with five levels of NaCl (0, 25, 50, 75 or 100 mM) in the nutrient solution, and four replicates. Plant height, stem diameter, number of leaves, dry matter of leaves, stems and roots, leaf area, leaf succulence, sclerophylly index and the contents of Na+, Cl- and K+ in different plant organs were evaluated after 40 days of stress. Salinity reduced the growth of all plant organs in the initial phase, in contrast, leaf succulence and sclerophylly index increased by 32% at the highest saline level, compared with control plants. The contents of Na+ and Cl- in leaves, stems and roots increased, while K+ contents decreased with the increment in salinity. The highest K+ contents were observed in the roots and the highest Na+ and Cl- contents were observed in the leaves. Salinity induced disturbances in the ionic homeostasis of noni plants, which can explain, at least in part, the salt-induced growth reduction. Key words: Salinity, sodium chloride, toxic ion.