Light interception and conversion efficiencies and biomass partitioning in sugarcane varieties with varying canopy architecture under subtropical conditions

Crop yield is determined by available solar energy and crop efficiency in intercepting light and converting such energy into biomass. However, such processes remain poorly understood in field-grown sugarcane under subtropical conditions. We aimed to estimate the efficiencies underlying crop yield in four sugarcane varieties with varying canopy architecture, revealing the genotypic variation and how environmental conditions affect the light interception efficiency (εi), light conversion efficiency (εc) and partitioning efficiency (εp). Classical growth analysis and measurements of incident and transmitted light through sugarcane canopies and leaf nitrogen content were done along the crop cycle. At harvest, technological analyses were performed in stalks, and cane and sugar yields were determined for IACSP95-5000 and IACSP94-2094 (planophile-like canopy), IACSP94-2101 and SP79-1011 (erectophile-like canopy) varieties. IACSP95-5000 and IACSP94-2101 are responsive to water availability and present high yield, while IACSP94-2094 and SP79-1011 are drought-resistant and recommended for limiting environments. Planophile-like varieties exhibited higher εi compared to erectophile-like ones, with the latter ones showing εi below 0.8. The highest εi was noticed in IACSP95-5000, reaching 0.9. Conversely, the highest εc of 0.097JJ-1 was found in IACSP94-2101, an erectophile-like variety. All varieties exhibited decreased εc under water deficit and low temperature, which happened during the winter season. Additionally, low leaf nitrogen content was found to contribute to low εc in IACSP95-5000 and IACSP94-2101. Reductions in εc were associated with the phenomenon of reduced growth, for the first time reported in Brazilian varieties. There were no differences in εp among sugarcane varieties, ranging from 0.86 to 0.88. However, the sugar yields of IACSP95-5000, IACSP94-2101 and IACSP94-2094 were higher than one found for SP79-1011. Notably and despite IACSP94-2101 having the highest εc, its sugar yield was comparable to that of IACSP95-5000, which exhibited the highest εi. Both εi and εc determined sugarcane yield, with high εi compensating low εc and vice-versa in varieties differing in canopy architecture. Erectophile-like varieties improved light distribution within the canopy, but planophile-like varieties exhibited superior canopy development and light interception. IACSP95-5000, IACSP94-2101, and IACSP94-2094 achieved higher sugar yields compared to SP79-1011, which