The overlooked ion: Unraveling the effects of magnesium-specific toxicity on willows under sulphate salinity

Abstract

Among all the current stressors on global agricultural systems, soil salinity is one of the most significant and continues to escalate. Traditionally, sodium chloride is the salt employed for studying salt stress in plants, but for many regions, sulphates are the predominant salts that cause soil degradation and curtail agricultural production. Willow trees (Salix spp.) have been identified as potential candidates for multipurpose establishment on salinity-affected marginal agriculture fields. To compare the impacts of sodium and magnesium sulphate salts, 12 native and hybrid willow genotypes were subjected to four sodium and magnesium sulphate salt treatments for 12 weeks. Magnesium sulphate treated willows showed more significant growth impacts, and displayed treatment-specific inhibition of photosynthesis, increased disruption of mineral nutrient balance, and greater inhibition of sulphur assimilation, compared to the trees treated with same level of sodium and same treatment osmolality. In addition, it was apparent that sulphate treatments encouraged sulphur uptake and translocation to the leaves, where it was partitioned to organic sulphur, but did not pool in small organic sulphur-containing compounds. The advantages and disadvantages of two different salt tolerance strategies were compared through a case study with two native willows, a sodium excluder and a sodium accumulator.