Exclusion of solar UV radiation increases the yield of curcuminoid in Curcuma longa L.

• Influence of PAR and UV solar exclusion in C. longa physiology was investigated.
• Total phenol content, POD and PAL activity decrease under UV exclusion.
• PAs content varies in plants under UV solar exclusion and full sun.
• Photosynthesis and biomass decrease under full sun.
• First report on enhancement in curcuminoid yield due to UV exclusion.

In this study, we grew Curcuma longa in field conditions under a range of shade levels and the exclusion of solar UV wavelengths to determine the effects of solar UV exclusion during cultivation on the physiology and production of curcuminoids. To broaden the biochemical characterization, the activities of l-phenylalanine ammonia-lyase (PAL) and peroxidase (POD), as well as total phenol content (TP) and polyamines (PAs), were considered. We discovered that the curcumin and DMC content remain unaltered, however BDMC was higher in the turmeric under 50% shading, comparing with UV exclusion. Although the total curcuminoid content remain unaltered, UV exclusion led to higher CO2 net assimilation, biomass production and consequently, a notable 21% increase of total curcuminoid yield, compared with the best result obtained by standard shading; thus UV exclusion improved total curcuminoid yield and this result may be important to the development of C. longa with high rhizome yield and with high curcuminoid content. This finding underlines the importance of selective wavelengths in C. longa cultivation.