Elevated carbon dioxide plus chronic warming causes dramatic increases in leaf angle in tomato, which correlates with reduced plant growth

Authors: JAYAWARDENA, DILEEPA - University Of Toledo; HECKATHORN, SCOTT - University Of Toledo; BISTA, DEEPESH - University Of Toledo; Boldt, Jennifer

Submitted to: Plant Cell and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2018
Publication Date: 11/25/2018
Publication URL: http://handle.nal.usda.gov/10113/6336614
Citation: Jayawardena, D.M., Heckathorn, S.A., Bista, D.R., Boldt, J.K. 2018. Elevated carbon dioxide plus chronic warming causes dramatic increases in leaf angle in tomato, which correlates with reduced plant growth. Plant Cell and Environment. 42(4):1247-1256. https://doi.org/10.1111/pce.13489.
DOI: https://doi.org/10.1111/pce.13489

Interpretive Summary: Leaf hyponasty, the upward bending of the petiole or blade during growth, can be induced by high temperatures or high carbon dioxide (CO2). We observed the combination of high temperature + elevated CO2 induces severe leaf hyponasty in Solanum lycopersicum L. (tomato). It increased slightly with either high temperature or elevated CO2, but increased dramatically with the combination of warming + high CO2. Also, it was slowly reversible when plants were returned to ambient temperatures and CO2. This increase in leaf angle corresponded to decreases leaf area and biomass, which likely is the result of decreased light interception as the leaves became more vertically oriented. Petiole hyponasty and leaf-blade cupping were also observed with warming + elevated CO2 in other species with compound leaves (marigold and soybean, respectively) but not in species with simple leaves (sunflower and okra). If severe leaf hyponasty is found to be common under warming + elevated CO2, this may have serious consequences for plant productivity and yield in coming decades as the climate changes.

Technical Abstract: Limited evidence indicates that moderate leaf hyponasty (upward bending of petiole or blade during growth) can be induced by high temperatures or un-naturally-high carbon dioxide (CO2). Here we report that the combination of high temperature plus elevated CO2 induces severe leaf hyponasty in Solanum lycopersicum L. (tomato). To characterize this phenomenon, well-watered and -fertilized tomato plants were grown at two levels of CO2 (400 vs. 700 ppm) and two temperature regimes (near-optimal, 30oC vs. supra-optimal, 37oC) for 16-18 days. Leaf hyponasty increased dramatically with the combination of warming and high CO2, but increased only slightly with either factor alone, and was slowly reversible upon transfer to control temperatures and CO2. Increases in leaf angle were not correlated with leaf temperature, leaf water stress, or heat-related damage to photosynthesis (Pn). However, steeper leaf angles were correlated with decreases in leaf area and biomass, which we could be explained by decreased light interception, and thus in situ Pn, as leaves became more vertically oriented. Petiole hyponasty and leaf-blade cupping were also observed with warming + elevated CO2 in marigold and soybean, respectively, which are compound-leaved species like tomato, but no such hyponasty was observed in sunflower and okra, which have simple leaves. If severe leaf hyponasty is common under high CO2 and warming, then this may have serious consequences for food production in coming decades.