Stomatal Frequency Change Over Altitudinal Gradients: Prospects for Paleoaltimetry

Abstract

Recently, a novel paleoaltimetry method was presented using leaf stomatal frequency response to the decline in CO 2 partial pressure with altitude, and tested on California black oak (Quercus kelloggii) (McElwain 2004). Here, we present new data detailing the infl uence of other climatic variables on leaf stomatal frequency change with altitude in the context of more fully characterizing how stomatal frequencies can be used to infer paleoelevations. A clear increase in stomatal density and stomatal index is observed with increasing elevation for Q. kelloggii (black oak) leaves, and Nothofagus solandri var. cliffortioides (mountain beech) growing over an altitudinal transect on the slope of Mt. Ruapehu (New Zealand). Modern leaves growing in full direct sunlight versus shaded diffuse light for both species show substantial differences in stomatal density and index, however, growth chamber experiments that vary light intensity have revealed that the magnitude of natural increase in radiation with altitude is likely insuffi cient to explain the overall increase in stomatal frequency (density and index) with elevation. Furthermore, temperature does not have a signifi cant infl uence on black oak stomatal frequency in growth chamber experiments. Rather changes in stomatal density and index with altitude appear to refl ect an adaptation to counteract the limited photosynthetic potential due to the CO 2 partial pressure decrease, further limited by shorter growing seasons and/or increased UV radiation. Our review of the uncertainties associated with the stomatal frequency paleoaltimeter from the literature, together with results from the new plant growth experiments indicate that if sea-level paleoatmospheric CO 2 concentration can be well-constrained, the stomatal frequency method has the potential for very low error margins.

Augmentation de la capacité photosynthétique avec l’altitude: mesures d’échanges gazeux à pressions partielles de CO2 ambiante et constante

“…Therefore, photosynthetic capacity seems to be under strong selective pressures typically observed at high elevation. Genetic adaptation to high elevation conditions could be a result of maintaining of higher leaf nitrogen, chlorophyll content (Oleksyn et al, 1998), stomatal density (Kouwenberg et al, 2007) and carboxylation efficiency (Körner and Diemer, 1987), and would allow trees to adapt to their local conditions.…”

“…In addition, Terashima et al (1995) only found no effect of partial pressure on photosynthesis at low temperature; this effect reached 23% at higher leaf temperatures (35 • C) for an elevation of 3000 m. Whereas this last study suggested that changes in the photosynthetic capacity of alpine plants can be attributed mostly to low temperature, we suggest that low CO 2 partial pressure at high elevation could also play a role in plant adaptation. Indeed, the decrease in CO 2 partial pressure is expected to increase stomatal density and stomatal conductance (Kouwenberg et al, 2007;Woodward and Bazzaz, 1988) and therefore maximum assimilation rate.…”

Adaptive variation in physiological traits of beech provenances in Central Europe

“…Several studies reported changes in stomatal traits with increasing altitude in various plant species including beech; PCI, guard cell length or stomatal density were observed to increase with altitude (Hovenden & Brodribb 2000, Kouwenberg et al 2007, Bresson et al 2009, Paridari et al 2013, presumably compensating for a decrease of CO2 partial pressure, which limits photosynthetic potential across altitudinal gradients, shorter growing seasons and/or increasing UV radiation (Woodward & Bazzaz 1988, Kouwenberg et al 2007. The increase in stomatal density and index with altitude could be also result of opening up of the higher altitude landscape, which increases the amount of intercepted radiation (Hovenden & Brodribb 2000).…”

Cuticle and subsurface ornamentation of intact plant leaf epidermis under confocal and superresolution microscopy

“…6). In the standard approach to cuticle analysis, leaves are macerated to separate the upper and lower cuticles using aqueous oxidizing agents (e.g., sodium hypochlorite, Cr(VI)O 3 , Schultz's solution; Kouwenberg et al, 2007), then stained with safranin O, bismuth brown, or toluidine blue, and then mounted on glass slides for transmitted light microscopy (Dilcher, 1974). Another common method is the use of scanning electron microcopy (SEM), a destructive approach where the leaves are similarly macerated, but then permanently mounted on stubs for imaging (Barclay and Wing, 2016;Stockey and Frevel, 1997;Stockey et al, 1998).…”

“…SLW0907; USNM617420). These were more firmly adhered to the rock, and thus were "peeled" off the rock using the polyester overlay technique adhering the upper leaf surface to the overlay, leaving the lower surface exposed (Kouwenberg et al, 2007). Silicate minerals were removed by immersing the fossil 1 overlay in concentrated hydrofluoric acid overnight.…”