Elongation patterns of basal internodes in sweet sorghum (Sorghum bicolor Moench)

Abstract

Based on the plant age (AL) indicated by leaf number, we analyzed the elongation patterns of basal internodes from the third internode (IN3) through IN10. Using two cultivars, Syrup sorgo 2 (S2, late-maturing) and high-sugar sorgo (HI, early-maturing) grown under field conditions in 1993, 20 plants were sampled when the leaf blade of the 4th through the 14th just fully expanded, and every internode length in the main stem was recorded. All internodes in IN9 and IN10 were classified as 'elongated internodes' (EIN: defined as that with final length more than 1.0 cm), while those from IN3 through IN6 were classified as non 'elongated internodes' (non-EIN: defined as that with final length less than 1.0 cm). In IN7 and IN8, both EIN and non-EIN existed. The EIN rapidly elongated from AL (n+1) when the (n+1) the leaf had just expanded to AL(n+3) and reached its maximum length by AL (n+4). This elongation pattern was similar to that of IN10 through IN19 as we reported previously. The non-EIN elongated from AL (n+2) and reached its maximum length by AL (n+3). At log phase of internode growth, the elongation rate of non-EIN was remarkably lower than that of EIN. It was suggested that the formation of intercalary meristem did not occur in the non-EIN. It is not likely that the elongation pattern of EIN and that of non-EIN were influenced by the cultivars.