Boron deficiency and toxicity altered the subcellular structure and cell wall composition architecture in two citrus rootstocks

Abstract

Abstract Trifoliate orange and citrange are two important rootstock resources to citrus, and citrange has a stronger tolerance to boron (B) deficiency and toxicity than trifoliate orange. In this study, we described how B deficiency and toxicity depressed the variations of cell wall B location, subcellular structure, cell wall components and structure of the two citrus rootstocks, to evaluate the mechanisms of different B tolerance of rootstocks on the cellular and structural levels. The results showed that citrange had better growth and lower symptoms of B stresses than trifoliate orange. What is more, citrange had a stronger ability to allocate more B to cell walls than trifoliate orange at deficient-B level. Under B deficiency and excessive conditions, severe damages in subcellular structure with obvious irregular thickening of cell walls and higher accumulation of plastoglobulus were observed in leaf cells of both two rootstocks. Additionally, it also showed obvious variations in the mode of hydrogen bonding, and more accumulation of cellulose, phenols and carbonhydrates in cell walls of trifoliate orange leaf under B starvation, while lighter changes on cell wall components were observed in citrange. As for B toxicity, comparing to trifoliate orange, citrange showed a lighter damage on pectin crosslinking structure in cell walls of leaf tissue. These results gained some novel mechanisms of different citrus rootstocks to B stress tolerance, and provide a theoretical basis for cultivating improved citrus rootstocks.