A temporal relationship between tissue firmness and cell wall compositions in radish roots (Raphanus sativus L.)

Individual radish roots from 13 cultivars were divided into three sections from the hypocotyl to the bottom end. When firmness was measured in terms of compressibility or shear force, the differences in the magnitude of root firmness among cultivars remained the same. Root tissue firmness was the highest in the 'Altari' type and lowest in the 'Spring Season' type. Dry matter, cell wall and starch contents were relatively higher in the 'Altari' type, showing 8%, 1.5% and 0.15% of fresh mass, respectively. Cellulose was the most abundant component of radish cell walls, ranging from 3.3 to 7.6 mg per gram of fresh mass. The amount of polyuronide in cell walls from the cultivars tested was between 2.0 and 5.7 mg per gram of fresh mass, and the total non-cellulosic neutral sugars (NCNS) content in cell walls was between 0.5 and 1.7 mg per g fresh mass of root tissue. Starch content varied from 0.00 to 0.15% of fresh mass. It was found that tissue firmness correlated with the amount of tissue dry matter (r=0.97), starch (r=0.82), and cell wall content (r=0.88). For cell wall composition, total noncellulosic neutral sugar (r=0.94), although the least abundant fraction, was most highly correlated with root firmness, followed by the polyuronide (r=0.83) and cellulose (r=0.52) contents.