Malbec responses to light quantity and quality

Abstract

Plant acclimation to the light environment involves changes in plant morphology, carbon- and water-
physiology, yield and quality of harvestable organs. Many cultural practices and crop management
decisions alter light quantity and quality. Canopy shade signals include low PPFD, R:FR ratios, UV-B
and blue light levels which are perceived by photoreceptors. Grapevine responses to light intensity have
been assessed in diverse varieties; whereas responses to light quality perceived by phytochromes have
only been evaluated in Syrah and Torrontés Riojano. This study aimed to investigate the effect of light
quantity and light quality perceived by phytochromes on shoot architecture, biomass, leaf morphology
and dry matter partitioning in Malbec. We cultivated potted plants under high (750-800 μmolm-2s-1) and low (250 – 300 μmolm-2s-1) PPFD in a greenhouse. Additionally, we supplemented plants with lateral far red radiation (730 nm) to test low vs. ambient R:FR (0.2 vs 1). Low PPFD did not induce changes in shoot and internode length, and neither affected aboveground plant biomass. However, reduced PPFD increased petiole length and diameter, and individual leaf area (LA), which resulted in a higher LA ratio.
Furthermore, low PPFD decreased leaf thickness, and leaves and lateral shoot biomass. By contrast, low
R:FR did not affect any morphological trait, neither dry matter partitioning. Malbec plants morphology
varied in response to variation in light intensity but not to variations in light quality perceived by
phytochromes, confirming our previous findings in Syrah and Torrontés. We suggest that light signals,
other than R:FR, triggers grapevine acclimation to low light.