Understanding drought responses of sugarcane cultivars controlled under low water potential conditions

Drought resistance mechanisms of sugarcane (Saccharum officinarum L.) vary with different conditions and locations. Understanding physiological and morphological responses of sugarcane cultivars grown under uniform and controllable conditions needs to be established. Therefore, the objective of this study was to investigate the mechanisms of drought responses of sugarcane cultivars grown under low water potential conditions via polyethylene glycol (PEG) induction. The hydroponic experiment was conducted under open greenhouse conditions. A split-plot in a randomised complete block design with three replicates was used. The PEG rates (0% and 1%) were assigned as main factor. Six sugarcanes cultivars differing in drought-resistance levels were sub-plot factors. To understand drought mechanisms, physiological and morphological traits were measured during stress and recovery periods. Drought mechanisms clearly evidenced only low water potentials at early growth stages, but not terminal drought stress. The six cultivars used in this study could be classified into two groups based on responses of shoot mass after exposure to early drought, consisting of reduced shoot dry weight when exposed to early drought stress and insensitive to early drought stress. In recovery phase, shoot DM of reduced shoot dry weight cultivar ('KKU99-03') was 754.6 and 499.5 g pl(-1) under control and PEG treatments, respectively, whereas shoot DM of insensitive group did not differ from control conditions. Drought resistance mechanisms, which can maintain aboveground DM of sugarcane cultivars under this condition, varied. Good adaptations for maintenance shoot mass under hydroponics were photosynthesis, stomatal conductance, partitioning of dry weight, root dry weight and green leaf munber proportions. The ability to perform well with acclimation of these traits might be useful for improving drought resistance genotypes in the future.