Influence of canopy architecture on the light interception, photosynthetic and biomass productivity in irrigated elite Sri Lankan rice varieties

Abstract

Purpose: Canopy light interception and extinction play a crucial role in determining crop yield. Developing new rice varieties with improved canopy architecture along with modified intrinsic photosynthetic mechanisms will ensure the global food security. However, a comprehensive understanding of local rice varieties addressing on such avenues have not been reported. Hence, our pioneering experiments were carried out to elucidate such underlying properties among locally developed two elite rice varieties viz; At-362 and Bg 94-1 grown in the Ampara district of Sri Lanka. Research Method: The field experiment was carried out at the Agro Tech Park, Malwatta (7°20'N and 81°44'E altitude 16.0 m above sea level) between October 2019 to January 2020 implemented with Randomized Complete Block Design with four replicates. The Photosynthetically Active Radiation (PAR) distribution on the above and below canopy level was measured during the pre and post-anthesis stages. Then leaf stomatal conductance, chlorophyll fluorescence parameters and the chlorophyll content were also measured. At harvest, the final biomass produced were compared. Findings: The result revealed that variety At-362 had a higher Leaf Area Index (LAI) of 2.64 at pre anthesis and tend to decline at the latter part of their growth cycle. The striking feature was the extinction coefficient (k) seems to be much lower (0.47) in the At-362 variety than the Bg 94-1 (0.60) depicting that the former has produced vertical leaves (erect-leaf type) while the latter tends to produce horizontal leaf plans in the canopy. Hence, light attenuation was high and eventually, the bottom canopy layer received much lower PAR. Furthermore, LAI had a strong negative correlation with understory PAR indicating that the canopy architecture with an improved light interception will lead to permit more light penetration and utilization through the improved quantum yield efficiencies than the horizontal canopies. Hence significantly (p<0.05) improved above-ground biomass and panicle weight were observed in At-362. Originality/value: This experiment depicts that rice yield could be further improved through introgression of canopy architectural features along with improved photosynthetic traits.