Plant responses to far-red supplementation and photosynthetically active radiation in an olive cultivar common to super high-density orchards

LADUX, FEDERICO J.; GONZÁLEZ, C.V.; TRENTACOSTE, EDUARDO R.; SEARLES, PETER S.; ROUSSEAUX, M. CECILIA

Rosario

Congreso; XXXIV Argentinian Meeting of Plant Physiology; 2023

Cultivation of olive trees in super high-density (SHD) hedgerows leads to a rapid increase in photosynthetic leaf area and yield, but also increases shading within and between trees. Such canopy shading both reduces photosynthetic active radiation (PAR) and red-to-far red ratio (R/FR). The objective of this study was to assess plant morphology, biomass, and photosynthetic pigment responses to different PAR and R/FR combinations in an olive cultivar Arbequina, common to SHD hedgerows. The four experimental combinations were low (L) or high (H) PAR with either supplemental lateral FR (+FR) or no FR supplementation (-FR). The L and H treatments were obtained using a 25% and 90% transmittance shade cloth, respectively. The +FR and –FR were achieved by using or not a light-emitting diodes that reduced the R/FR ratio from about 0.90 to 0.25. The internode length and main stem elongation were lower under L than H, and were higher in L+FR than L-FR. Axillary shoots were more vertically-oriented under L+FR than the other treatments, while leaf angle was more vertical with +FR at both PAR levels. Based on a principal component analysis of all the measured variables, the +FR plants did not differ from -FR under H, but they did differ from -FR under L. These findings suggest that young, cv. Arbequina olive trees do not anticipate imminent shading when PAR is still high through early low R/FR signals. However; different plant morphology, architecture and photosynthetic pigment traits were modified that could affect light absorption and penetration into the hedgerow later in orchard development when low PAR through direct shading is prominent