The effects of the combination of salinity and excess boron on the water relations of tolerant tomato (Solanum lycopersicum L.) cv. Poncho Negro, in relation to aquaporin functionality

Abstract

As elevated levels of boron (B) are accompanied by conditions of excessive salinity with drastic consequences for crops,
it is crucial to find a crop that is tolerant to these conditions. In this work, the interaction between salinity and excess B
with respect to aquaporin-mediated changes by blockade of mercury and water relations were studied as well as the osmotic adjustment of the plants. The treatments, for tomato ‘Poncho Negro’ cultivated hydroponically in a controlled environment chamber, were control (75 and 150 mM) NaCl and/or 5 mg L–1 or 20 mg L–1 B. Hydraulic conductance (L0) of detached exuding root systems exhibits large variations in response to abiotic stimuli. No additive (synergic) effects of B and salinity were observed. Under salinity, the plants increased their turgor, compensating for the decrease in the leaf water potential through the reduction in the leaf osmotic potential by the accumulation of soluble sugars and proline. The involvement of Hg2+-insensitive aquaporins or the osmotic gradient as the main force for water flow through the apoplastic pathway must be contemplated. Finally, all the data reveal the tomato cv. Poncho Negro to be a germplasm of agronomic interest and a good alternative for cultivation areas with high content of salts and the excess B of the soil and irrigation water.