Gibberellin-induced perturbation of source-sink communication promotes sucrose accumulation in sugarcane.

Constant removal of sugars from the site of synthesis (i.e., leaves), in response to elevated sink (culm) demand, may perhaps prevent damping of photosynthesis, by sugar, and hence promote further sucrose accumulation in the culm. In this study, gibberellic acid (GA) induced nearly 42.3% enlargement in cell size and about 39.3% increase in internodal length (sink capacity), 177% escalation in reducing sugar level (sink strength), amplified the expression of sucrose-metabolizing enzymes (sink demand), viz., 7.5-fold for SAI, 4.5-fold for CWI, sixfold for SPS, all demonstrating facilitation of augmented sucrose accumulation in the culm. The GA-treated BO 91 cane (late maturing sugarcane variety) exhibited an elevated final sucrose concentration (40.54-41.6%) as compared to control (30.44-38.8%). The GA-sprayed cane of early maturing Co J64 also showed such a boost, but it was lost by the end of maturity, perhaps due to inversion and/or the less effective GA treatment. Thus, results demonstrated the role of GA in augmenting sucrose content of cane culm, possibly by influencing source-sink dynamics in sugarcane.