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Leaf removal is a standard vineyard management technique to influence grape composition or to reduce disease pressure. However, the optimal timing and intensity of leaf removal is variable.
Christopher Bahr and colleagues from Hochschule Geisenheim University examined the effect of leaf removal on light distribution using a functional-structural plant model in a recent in silico Plants article.
The authors used the existing model, Virtual Riesling, which simulates the dynamic growth of Riesling grapevines from bud burst on the cane to end of flowering in daily time steps. They first extended the model by including a method for leaf removal that resembles practical application techniques in vineyards.
They compared two leaf removal scenarios as advised by local experts. All virtual leaves were removed from the east side of canopies from within or above the bunch zone. The respective treatments removed about 26 % and 17 % of the total leaf area of a plant. The control rows had no leaves removed. They then simulated grapevine light absorption and growth of over 1,000 plants.
The effect of leaf removal on light absorption was evaluated over a period of three weeks after leaf removal. On the west side of the row, light absorption increased slightly compared to the control following leaf removal. On the east side, light absorption for both scenarios decreased after leaf removal. Canopies with leaf removal within the bunch zone had less light absorption than those with leaf removal above the bunch zone. Loss compensation for both removal scenarios is evident as absorption following removal converge continuously to the control.
Observations in the 3D-views of the model indicated how this compensation was possible. Gaps in the grapevine canopy caused by leaf removal diminished over time and were negligible at the end of the simulation period as lateral leaves closed the gaps induced by leaf removal and leaves in the proximity of the leaf removal zones were re-exposed to light.
According to Bahr, “results showed similar effects as observed in in vivo studies, hence, we suggest extending these simulations to investigate other effects linked to light distribution such as berry sunburn. Simple modifications of implemented leaf removal techniques also allow for testing different application scopes and their impact on canopy light absorption.”
The Virtual Riesling model is available from the authors upon request.
Christopher Bahr, Dominik Schmidt, Matthias Friedel, Katrin Kahlen, Leaf removal effects on light absorption in virtual Riesling canopies (Vitis vinifera), in silico Plants, Volume 3, Issue 2, 2021, diab027, https://doi.org/10.1093/insilicoplants/diab027
This manuscript is part of in silico Plant’s Functional Structural Plant Model special issue.