Sucrose uptake and accumulation by internode tissue of high and low sugar cultivars of sugarcane from exogenously supplied sucrose medium

Sucrose uptake and accumulation from exogenously supplied sucrose medium by internode tissue of two contrasting sugarcane cultivars i.e. CoJ64 (high sugar and early maturing) and Co1148 (low sugar and late maturing) was studied. Cell sap sucrose concentration of the tissued from 3rd internode of Co1148 after incubation for 3 h in 100 mM sucrose solution increased from 99 mM to 116 mM while in CoJ64 it decreased from 223 to 205 mM. However, when the tissued was osmotically equilibrated prior to incubation in sucrose medium with PEG-6000 of equivalent osmolarity as that of the sucrose bathing medium, both the cultivars actively took up sucrose and final cell sap sucrose concentration increased many folds after incubation for 24h. From 400 and 200 mM sucrose bathing medium similar final cell sap sucrose concentration was maintained by both the cultivars. However, from 100 and 50 mM sucrose bathing medium, tissue from CoJ64 attained 529 and 227 mM final cell sap sucrose concentration as compared to 183 and 94 mM attained by tissue from Co1148. Lower concentration (25 mM) of the bathing medium caused a decrease in final cell sap sucrose concentration in both the cultivars. When tissue from internodes of variable age after osmotic equilibration with PEG-6000, were incubated in 200 mM sucrose bathing medium, the younger internodes of both the cultivars were more efficient in sucrose uptake and the two cultivars were similar in final cell sap sucrose concentration. However, The 5th and lower internodes down the stalk of CoJ64 showed no significant change in final cell sap sucrose concentration as compared to pre-incubation cell sap sucrose concentration. In Co1148 where the initial cell sap sucrose was less, the tissue continued increasing the sucrose in the lower internodes as well. The results are discussed in context of sugar content and maturity group of the two cultivars.