Tracking Sodium Inside the Plant: Hydraulic Adjustments to Deal With Salinity

Sorghum is a crop that has become more relevant in recent years due to its uses and properties (biofuel, gluten‐free flour) as well as its versatility to grow in unfavourable environmental conditions. Salinity is one of the main abiotic stresses affecting crop production and yield worldwide. The aim of this work was to study the response of sorghum seedlings to soil salinity in two genotypes with known performance to cope with water stress. Physiological parameters related to plant water status, as well as the sodium content in the plant, were analysed. We studied the possible role of pricklets and microhairs in the response to salt conditions. Our results showed that both genotypes restored their water status parameters after 24 h of salt stress. However, we observed differential physiological responses to salt concentration: at 200 mM NaCl root hydraulic conductivity dropped, while at 100 and 300 mM NaCl it remained unchanged. There was no evidence of the presence of sodium in the microhairs or on the leaf blade surfaces, but the presence of silicon inside the pricklet at 300 mM NaCl after 24 h was detected, although not in the microhair. The mechanisms involved in those physiological responses and the probable involvement of silicon under high salt concentrations (300 mM) still remain unclear.