What is the most prominent factor limiting photosynthesis in different layers of a greenhouse cucumber canopy?

• Published in: Annals of botany Vol. 114; no. 4; pp. 677 - 688
• Main Authors: Chen, Tsu-Wei, Henke, Michael, de Visser, Pieter H. B, Buck-Sorlin, Gerhard, Wiechers, Dirk, Kahlen, Katrin, Stützel, Hartmut
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01.09.2014; Oxford University Press (OUP)
• Subjects: Agricultural sciences; biochemical-model; Biochemistry; canopy; co2 assimilation; Computer Simulation; crop yield; cropping systems; Cucumbers; Cucumis sativus; Cucumis sativus - growth & development; Cucumis sativus - physiology; Cucumis sativus - radiation effects; diffuse-radiation; Forest canopy; greenhouses; Horticulture; Leaf area; leaf nitrogen; leaves; Life Sciences; Light; light-absorption; Mesophyll; mesophyll conductance; Models, Biological; Photons; Photosynthesis; Photosynthetically active radiation; Plant Leaves - growth & development; Plant Leaves - physiology; Plant Leaves - radiation effects; Plant Stems - growth & development; Plant Stems - physiology; Plant Stems - radiation effects; rubisco turnover; Simulations; structural plant-model; use efficiency; Vegetation canopies; water-stress; quantitative limitation analysis; FvCB model; cucumber; diffuse light; functional–structural plant model; graphics processing unit; photosynthetic limitations; GroIMP; Cucumis sativus; canopy photosynthesis; GPU
• ISSN: 0305-7364; 1095-8290
• DOI: 10.1093/aob/mcu100

Background and AimsMaximizing photosynthesis at the canopy level is important for enhancing crop yield, and this requires insights into the limiting factors of photosynthesis. Using greenhouse cucumber (Cucumis sativus) as an example, this study provides a novel approach to quantify different components of photosynthetic limitations at the leaf level and to upscale these limitations to different canopy layers and the whole plant.MethodsA static virtual three-dimensional canopy structure was constructed using digitized plant data in GroIMP. Light interception of the leaves was simulated by a ray-tracer and used to compute leaf photosynthesis. Different components of photosynthetic limitations, namely stomatal (SL), mesophyll (ML), biochemical (BL) and light (LL) limitations, were calculated by a quantitative limitation analysis of photosynthesis under different light regimes.Key ResultsIn the virtual cucumber canopy, BL and LL were the most prominent factors limiting whole-plant photosynthesis. Diffusional limitations (SL + ML) contributed <15 % to total limitation. Photosynthesis in the lower canopy was more limited by the biochemical capacity, and the upper canopy was more sensitive to light than other canopy parts. Although leaves in the upper canopy received more light, their photosynthesis was more light restricted than in the leaves of the lower canopy, especially when the light condition above the canopy was poor. An increase in whole-plant photosynthesis under diffuse light did not result from an improvement of light use efficiency but from an increase in light interception. Diffuse light increased the photosynthesis of leaves that were directly shaded by other leaves in the canopy by up to 55 %.ConclusionsBased on the results, maintaining biochemical capacity of the middle–lower canopy and increasing the leaf area of the upper canopy would be promising strategies to improve canopy photosynthesis in a high-wire cucumber cropping system. Further analyses using the approach described in this study can be expected to provide insights into the influences of horticultural practices on canopy photosynthesis and the design of optimal crop canopies.