Gas exchange and time to reach maximum rate of photosynthetic rateand their relationship with whole-plant traits in sugarcane in water abundant Louisiana, USA

Abstract

Variety development of sugarcane (Saccharum spp. hybrids) is necessary to continue improving sugar yields and selecting photosynthetic traits can improve sugar production through increased carbon inputs. In this study, gas exchange and whole-plant measurements were made on 55 sugarcane genotypes in Louisiana. Variation in the relationship between photosynthetic rate and stomatal conductance suggests that sugarcane exhibits variation in both photosynthetic capacity and CO2 substrate availability. Genotypes that reached maximum photosynthetic rate (TRMPR) in the gas-exchange cuvette more quickly had greater CO2 assimilation during transitory periods. Temporary shading and fluctuating light are common transitory conditions in the field, so increasing TRMPR can improve photosynthesis in water-abundant regions. Canopy leaf area was positively correlated with stalk mass, but gas-exchange traits were not correlated with whole-plant traits. A better understanding of the relationship between leaf and whole-plant traits is necessary to identify physiological traits that lead to increased genetic gain.

Keywords

• gas exchange
• phenotyping
• photosynthesis
• stomatal conductance
• stomatal propensity to remain open
• sugarcane