The effect of salinity and high boron on growth, photosynthetic activity and mineral contents of two ornamental shrubs

Abstract

Simultaneous salinity and boron (B) excess often occur due to irrigation with water containing high levels of salts, including B. The effects of excess of NaCl and B in the nutrient solution on some agronomical and physiological parameters of Viburnum tinus (laurustinus) and Metrosideros excelsa (metrosideros) were studied. Potted plants were grown in a factorial combination of B (1 and 6 mg/l) and NaCl (2 and 6 dS/m). B toxicity (6 mg/l) caused tip/edge burn in the lower leaves of laurustinus, while these symptoms were absent in metrosideros. Toxicity by B reduced dry biomass in the two species, particularly the aerial part in metrosideros and the roots in laurustinus. Metrosideros accumulated a similar content of B in all leaves, while the laurustinus tended to accumulate more B in the lower leaves. The leaf B content in laurustinus was reduced by salinity to a greater extent than in metrosideros; however, this was not sufficient to prevent injuries to the laurustinus photosynthetic system.