Work

Heat stress reduces stomatal numbers in Ginkgo biloba: Implications for the stomatal method of palaeo-atmospheric [CO2] reconstruction during episodes of global warming

Year: 2024

Type: article

Abstract: The stomata of fossil plants are commonly used as proxies to reconstruct palaeo-atmospheric carbon dioxide concentrations (palaeo-[CO 2 ]). Stomatal reconstruction of palaeo-[CO 2 ] during global greenhouse periods or episodes of global warming, are particularly important to our understanding of the role of CO 2 as a climate system driver. However, the efficacy of the ‘stomatal method’ for palaeo-[CO 2 ] reconstruction depends upon the strength of the inverse relationship between stomatal number and the [CO 2 ] in which the leaf developed. However, the impact of heat stress on stomatal initiation and development are largely unknown. Ginkgo biloba , a living fossil species, seedlings were grown in controlled environment chambers under 20/25 °C and 30/35 °C night/day temperature regimes. Heat stress in the 30/35 °C treatment impaired photosynthetic function, decreased stomatal conductance ( G s ), and reduced stomatal index (SI), indicative of lower stomatal initiation. Modelled theoretical G s did not correlate with observed measured G s , undermining the utility of palaeo-[CO 2 ] reconstructions based on stomatal diffusion modelling. The lower stomatal initiation of G. biloba leaves from the higher temperature resulted in greater estimates of [CO 2 ] based on SI values using the nearest living equivalent and SI-[CO 2 ] transfer function approaches. Heat stress may diminish the effectiveness of the stomatal method in reconstructing palaeo-[CO 2 ] during intervals of global warming marked by floral turnover in Earth history. • The ‘stomatal method’ is widely used to reconstruct palaeo-[CO 2 ] over Earth history. • Reliable palaeo-[CO 2 ] is important during periods of rising global temperatures. • Ginkgo biloba is often used as a nearest living equivalent for fossil Ginkgoales. • Heat stress induced a reduction in stomatal initiation in Ginkgo biloba . • Measured and modelled stomatal conductance did not correlate under heat stress. • Stomatal palaeo-[CO 2 ] reconstructions may be affected by heat stress.

Source: The Science of The Total Environment

DOI: 10.1016/j.scitotenv.2024.177962