The Developmental Stages of Sugarcane Stalk are Equivalent between Plants of Different Chronological Ages

Sugarcane stalks sequentially produce internodes, with the most immature and mature internodes at the top and base of the stalk, respectively. Resulting in a range of internodes at different developmental stages in each stalk. When sampling similar developmental internodes, replicate plants may differ in chronological age due to various reasons, including different germination rates, regeneration from tissue culture, and treatments affecting growth. To date, there has been no research to test if internodes of the same developmental age are equivalent between plants of different chronological age, for example to demonstrate that internode 4 from a 6-month-old plant is functionally equivalent to internode 4 from a 9-month-old plant. Internodes 4, 6 and 11 were assessed in two varieties, Q117 and Q208, across a range of chronological ages from 6 to 9 months. This study utilised a combination of tissue morphology measurements, gene expression and metabolite abundance results to discern chronological/developmental variation. Some genes and metabolites were measured in both varieties and some were unique to each variety. When results from the two varieties were pooled together the internodes had more overlap between samples; highlighting that the uniqueness between the varieties was greater than internode similarity or that a different range of genes/metabolites is required when comparing different varieties. Analysis of the measurements for each variety independently did result in similar internode samples clustering together regardless of chronological age, with minimal overlap. These results illustrate that samples of similar developmental stage (± 1 internode) are similar between stalks of different chronological age. With this knowledge, researchers can now reliably compare internodes from plants of different chronological age, with confidence that results are not confounded by plant age.