A whole canopy gas exchange system for the targeted manipulation of grapevine source-sink relations using sub-ambient CO2

Abstract

BackgroundElucidating the effect of source-sink relations on berry composition is of interest for wine grape production as it represents a mechanistic link between yield, photosynthetic capacity and wine quality. However, the specific effects of carbohydrate supply on berry composition are difficult to study in isolation as leaf area or crop adjustments can also change fruit exposure, or lead to compensatory growth or photosynthetic responses. A new experimental system was therefore devised to slow berry sugar accumulation without changing canopy structure or yield. This consisted of six transparent 1.2 m3 chambers to enclose large pot-grown grapevines, and large soda-lime filled scrubbers that reduced carbon dioxide (CO2) concentration of day-time supply air by approximately 200 ppm below ambient.ResultsIn the first full scale test of the system, the chambers were installed on mature Shiraz grapevines for 14 days from the onset of berry sugar accumulation. Three chambers were run at sub-ambient CO2 for 10 days before returning to ambient. Canopy gas exchange, and juice hexose concentrations were determined. Net CO2 exchange was reduced from 65.2 to 30 g vine− 1 day− 1, or 54%, by the sub-ambient treatment. At the end of the 10 day period, total sugar concentration was reduced from 95 to 77 g L− 1 from an average starting value of 23 g L− 1, representing a 25% reduction. Scaling to a per vine basis, it was estimated that 223 g of berry sugars accumulated under ambient supply compared to 166 g under sub-ambient, an amount equivalent to 50 and 72% of total C assimilated.ConclusionsThrough supply of sub-ambient CO2 using whole canopy gas exchange chambers system, an effective method was developed for reducing photosynthesis and slowing the rate of berry sugar accumulation without modifying yield or leaf area. While in this case developed for further investigations of grape and wine composition, the system has broader applications for the manipulation and of study of grapevine source-sink relations.

Differential response of the accumulation of primary and secondary metabolites to leaf‐to‐fruit ratio and exogenous abscisic acid

“…This might be because of preferential allocation of carbon to sugar accumulation rather than anthocyanin biosynthesis under carbon limitation, as suggested by Bobeica et al (2015). Smith et al (2019) developed a system, however, to directly manipulate whole vine carbon assimilation without affecting canopy size or bunch environment via reduced air CO 2 concentration, finding no impact on the ratio of anthocyanins to sugars during maturation, despite a 50% reduction in maturation rate (Edwards et al 2017). Therefore, the decoupling seen here may be because of a more extreme difference in L/F or be influenced by additional factors, possibly interactively with L/F.…”

The Effect of Elicitors and Canopy Management in the Chemical Composition of Vitis vinifera Red Varieties in Warm and Hot Areas in Spain

“…The sprawling system accumulated a larger concentration of reducing sugars (8%). In other studies, contrary to what has been observed, the minimal modification of the canopy has led to a slowdown in the accumulation of sugars as a consequence of the photosynthetic response of the vine [27]. In this case, the microclimate, besides the CO 2 exchange and the berries' exposure, may have had an impact on the chemical composition of the berries.…”

“…These results are the opposite of other studies, where more reducing sugar with heavy canopy management (12.97%) was obtained. Despite this, differences between the control and canopy management cultivars can be observed [27]. Other statistical differences between trimming trials can be seen in the concentrations of malic acid and tartaric acid.…”

Effects of intra-vineyard variability and soil heterogeneity on vine performance, dry matter and nutrient partitioning

“…Ample withinyear variation of these parameters is not surprising at all. Taking example of TSS vs total anthocyanins behaviour, while both are quite sensitive to crop load, it is well understood that TSS primarily react to whole-canopy photosynthesis (Salazar-Parra et al 2018;Smith et al, 2019), whereas colour accumulation is more heavily impacted by local micro-climate conditions and cultural practices affecting light distribution in the fruiting area and, most importantly, cluster temperature (Haselgrove et al, 2000;Poni et al, 2018). Nonetheless, inter-annual spatial variability in this study was definitely minor regardless of any involved growth, yield or fruit quality parameters.…”