GiESCO 2019 banner
IVES 9 IVES Conference Series 9 GiESCO 9 Diffuse light due to wildfire smoke enhances gas exchange of shaded leaves

Diffuse light due to wildfire smoke enhances gas exchange of shaded leaves

Abstract

Context and purpose of the study – The risk of wildfires is increasing as the frequency and severity of drought and heat waves continue to rise. Wildfires are associated with the combustion of plant materials and emit smoke. In the atmosphere, smoke may spread readily across large areas. Smoke is composed of solid and liquid phase particulates and gases and has been identified as a causal agent of “smoke taint” in wine. On a smoky day, the intensity of direct light decreases because these particulates scatter sunlight. Even though this effect is frequently assumed to decrease plant photosynthesis, this assumption ignores the potential changes in diffuse light and may be based on scant evidence. This study compared leaf gas exchange on the sunny and shaded sides of a grapevine canopy during a very smoky, and thus hazy, day.

Material and methods – Five own-rooted Cabernet Sauvignon vines were used in a north-south oriented vineyard row in warm and arid eastern Washington during wildfire events in North America. Vines were drip-irrigated, spur-pruned, and trained to a loose vertical shoot-positioning system. Leaves at a height of 1.5 m were sampled on both sides of the canopy. Leaf temperature, light intensity, stomatal conductance, and gas exchange were measured with a portable infrared gas analyzer on 9 August 2018, in the afternoon about 4:00 PM. The diffuse light was estimated by blocking the direct light to the quantum sensor facing the sun.

Results – Diffuse light accounted for 40% of the incoming light. On the sun-exposed west side of the canopy, the light intensity in the afternoon was 1000 µmol m-2 s-1, while on the east side the light intensity was slightly above 100 µmol m-2 s-1. Leaves on the west-facing side of the canopy were 2°C warmer than leaves on the other side, and the former also had higher photosynthesis and transpiration rates, but leaves on both sides had the same stomatal conductance. Only receiving 10% sunlight, the shaded leaves maintained positive net carbon assimilation and had photosynthesis rates of 25% compared to the fully exposed leaves. While the leaves on the west side transpired at a rate of 7.6 mmol m-2 s-1, their counterparts on the east side maintained a rate of 6.1 mmol m-2 s-1.Therefore, the water use efficiency (WUE) was 27% lower for the east-facing canopy than for the opposite side. These results indicate leaves on the sunny side still received light at saturation level and leaves on the shaded side may provide surplus photosynthates on a smoky day. Further, in a well-watered vineyard, shaded leaves open their stomata once there is enough sunlight for photosynthesis even if the leaves are operating at lower WUE.

DOI:

Publication date: September 18, 2023

Issue: GiESCO 2019

Type: Poster

Authors

Ben-Min CHANG1, Markus KELLER1*

Washington State University-Irrigated Agriculture Research & Extension Center, 24106 N. Bunn Rd., Prosser, Washington, USA

Contact the author

Keywords

photosynthesis, transpiration, stomata conductance, water use efficiency, light intensity

Tags

GiESCO | GiESCO 2019 | IVES Conference Series

Citation

Related articles…

Adapting the vineyard to climate change in warm climate regions with cultural practices

Since the 1980s global regime shift, grape growers have been steadily adapting to a changing climate. These adaptations have preserved the region-climate-cultivar rapports that have established the global trade of wine with lucrative economic benefits since the middle of 17th century. The advent of using fractions of crop and actual evapotranspiration replacement in vineyards with the use of supplemental irrigation has furthered the adaptation of wine grape cultivation. The shift in trellis systems, as well as pruning methods from positioned shoot systems to sprawling canopies, as well as adapting the bearing surface from head-trained, cane-pruned to cordon-trained, spur-pruned systems have also aided in the adaptation of grapevine to warmer temperatures. In warm climates, the use of shade cloth or over-head shade films not only have aided in arresting the damage of heat waves, but also identified opportunities to reduce the evapotranspiration from vineyards, reducing environmental footprint of vineyard. Our increase in knowledge on how best to understand the response of grapevine to climate change was aided with the identification of solar radiation exposure biomarker that is now used for phenotyping cultivars in their adaptability to harsh environments. Using fruit-based metrics such as sugar-flavonoid relationships were shown to be better indicators of losses in berry integrity associated with a warming climate, rather than solely focusing on region-climate-cultivar rapports. The resilience of wine grape was further enhanced by exploitation of rootstock × scion combinations that can resist untoward droughts and warm temperatures by making more resilient grapevine combinations. Our understanding of soil-plant-atmosphere continuum in the vineyard has increased within the last 50 years in such a manner that growers are able to use no-till systems with the aid of arbuscular mycorrhiza fungi inoculation with permanent cover cropping making the vineyard more resilient to droughts and heat waves. In premium wine grape regions viticulture has successfully adapted to a rapidly changing climate thus far, but berry based metrics are raising a concern that we may be approaching a tipping point.

Application to the wine sector of European Convention on the landscapes

The landscape is defined by the European convention of the landscape (Florence, October 20, 2000) like part of the territory as perceived by the populations, whose character results from the action of natural and/or human factors and their interrelationships. This convention is based on the contribution cultural, ecological, environmental, social of the landscapes and aims at a reinforcement of the tools of protection and valorization in particular in the agricultural policies, of regional planning and town planning. Moreover, it encourages a step of identification and qualification of the landscapes and underlines the need for developing the sensitizing and the training of the actors concerned.

EUGENOL AS QUALITY MARKER OF WINES AND SPIRITS FROM HYBRID VINES: IMPACT OF DIFFERENT WINEMAKING AND DISTILLATION PROCESSES

Eugenol, widely spread in various plants notably cloves, basil and bay, was identified too in wines from hybrid grapes without contact with oak wood. This aromatic molecule presents a strong spicy note of clove and also antifongic properties. Eugenol was described as an endogenous compound of Baco blanc, from the grapes to the spirits of Armagnac area. Moreover, this compound is a chemical marker of Baco blanc products quality.
Influences of harvest time and different winemaking processes (settling, use of enzymatic preparations, lees content and stock time before distillation) on Baco blanc wine eugenol contents were explored using a two-levels full factorial Design of Experiments (DoEs).

Are all red wines equals regarding their vulnerability to Brettanomyces bruxellensis ?

Odours deemed harmful by the consumer and described as “stable”, “horse sweat” or “burnt plastic” can be found in wines. The responsible molecules are volatile phenols, produced by a spoilage yeast: brettanomyces bruxellensis. This species is particularly well adapted to the wine environment and can resists many stresses such as a high alcohol level, a low ph or high levels of SO2, more or less efficiently depending on the strain considered.

Influence of withering on valpolicella docgs grapes volatile composition

The blend of grapes used in the production of the four Valpolicella PDOs red wines, namely Valpolicella, Valpolicella Classico Superiore, Recioto della Valpolicella and Amarone della Valpolicella is quite unique, and includes two main varieties Corvina and Corvinone, and other minor varieties. To a very large extent all these grapes are only grown in the province of Verona. One of the main characteristics of Valpolicella is the use of grapes that are submitted to post-harvest withering. The aim of this study was therefore to evaluate the evolution of the free and glycosidically-bound volatile compounds in Corvina and Corvinone grapes under real production conditions.