Temperature effect on carbon partitioning in two commercial cultivars of sugarcane

Abstract

The effect of temperature upon plant growth and partitioning of dry matter in sugarcane (Saccharum spp.) was determined. Sugarcane plants of two commercial cultivars, Q117 and Q138 were grown under constant conditions for 72 days then subjected to one of four different ambient temperature regimes, 14, 18, 22 or 26°C. Plants were harvested before the imposition of the treatments, then at 85, 120, 155 and 190 days after planting (DAP) for biomass and sugar partitioning. Following the imposition of temperature treatments, the increase in stalk length and node number was linear and notably different between the temperature regimes for both cultivars. When the data was described in terms of thermal time (growth temperature (C) × number of days), the number of internodes produced per unit of thermal time was the same irrespective of the temperature in which the plants were grown and internode number increased in a linear manner with an increase in total thermal input. Stalk dry matter accumulation over time was linear at the log-scale and highly significant, (P < 0.001) for both Q117 and Q138. The linear rate of accumulation increased with temperature ranging from 1.39 g day–1 at 14°C to 5.31 g day–1 at 26°C for Q117, whereas in Q138 it ranged from 2.24 g day–1 to 4.39 g day–1 at temperatures of 14 and 26°C, respectively. The pattern of total sucrose accumulation also followed an exponential trend, with little difference evident until 155 DAP where rates increased with temperature for both varieties. However, the increase between 14 and 26°C was more profound for Q117. The sucrose/hexose ratio also differed between the cultivars. This difference was most pronounced in plants grown at both 14 and 18°C where the ratio of sucrose/hexose in Q117 was double that measured in Q138. The production of phytomeric units in sugarcane is clearly a function of accumulated degree-days and influenced by cultivar. The elongation of internodes is influenced by temperature and varietal interaction but is not a function of degree-days.