ABSTRACT Salinity stress predominantly affects negatively charged cell wall polymers, for example, pectin. Excess Na + ions interact physically and affect growth in stress‐sensitive plants. However, the salinity resistance of sugar beet cell walls remains unclear. To get a better understanding of cell wall assembly, we investigated arabinogalactan‐proteins (AGPs), extensins and pectic polysaccharides (homogalacturonan, rhamnogalacturonan‐I and rhamnogalacturonan‐II), in relation to underlying physiological mechanisms and growth expansion with low and adequate boron (B) under salinity. Findings revealed that salt stress affects AGPs and reduces cross‐linking of RG‐II, resulting in the softening of the sugar beet plant's cell wall. Adequate B compensates for plant growth by improving water flow into the cell, as indicated by the transpiration rate and stomatal conductance. In particular, the higher reduction of the Na + /Ca 2+ ratio in the young leaves and apoplastic fluids and higher RG‐I content and dimeric RG‐II pectin (a key component of cell wall integrity) offered by adequate B, hint at protection against cell wall defects. However, no influence of B was detected for AGPs and extensins. This suggests that adequate B rescues cell wall integrity, thereby conferring strengthening and acid growth.
Chowdhury et al. (Thu,) studied this question.