Oxygen isotope ratio of leaf and grain material correlates with stomatal conductance and grain yield in irrigated wheat

Abstract

Theory (Craig and Gordon 1965; Dongmann et al. 1974; Sternberg et al. 1986; Farquhar and Lloyd 1993) suggests that the oxygen isotope ratio (d 18 O) of plant material should reflect the evaporative conditions under which the material was formed, so that differences in stomatal conductance should show up in plant d 18 O. To test this theory we measured the oxygen isotope ratio of organic matter from flag leaves at anthesis and grain at harvest from eight cultivars of spring wheat (Triticum aestivum L.) grown under irrigation in each of three seasons in Mexico. The cultivars ranged widely in stomatal conductance and in average grain yield, with which conductance was positively correlated. Supporting theory, the oxygen isotope ratio of flag leaves (d 18 Ol) was found to correlate negatively with stomatal conductance for two of the three seasons. The significant correlations are consistent with high conductance cultivars having lower leaf temperatures and kinetic fractionation factors, and higher vapour pressure fractionation factors and Péclet numbers, all of which combine to result in less enriched d 18 Ol. Yield (grain weight per square meter) was also found to be significantly negatively correlated with d 18Ol in two of the three seasons. d 18 Ol was as good a predictor of yield as stomatal conductance, and significantly better than carbon isotope discrimination. Correlations between grain d 18 O (d 18 Og) and physiological parameters were less clear. Significant negative correlations between d 18 Og and stomatal conductance, leaf temperature and yield were found only during the first season. By measuring the oxygen isotope ratio of cellulose extracted from leaf samples, the difference in fractionation factors (ecp) for cellulose and whole leaf tissue was assessed. ecp was found to be variable, and more negative when d 18 Oc and d 18 Ol were lower. Cultivar means for d 13 C and d 18 O of whole leaf material were found to be significantly positively related, and the factors required to produce such a relationship are discussed.

Maize Production in a Changing Climate

“…Recently Cabrera--Bosque et al (2009a;2009b) proposed oxygen is 18 O) and kernel ash content as new physiological traits to improve maize yields in drought--prone environments. Both traits provide an integrative measurement of physiological traits during the crop growth cycle, with 18 O reflecting plant evaporative conditions throughout the crop cycle (Barbour et al, 2000) while kernel ash content provides information on integrative photosynthetic and retranslocation processes during grain filling (Araus et al, 2001). Together these tools have potential to be used in the characterization and identification of key drought tolerant donors to be used in breeding programs.…”

Impact of traffic on δ15N, δ13C and δ18O of needles and annual tree rings of Norway spruce (Picea abiesL.)

“…In particolare, l'albero più vicino all'autostrada (indicato con T 1 ), mostra un evidente aumento del δ 13 C e, meno pronunciatamente, del δ 18 O, a partire dagli anni '60, fino agli anni '80. Questo risultato potrebbe indicare una minore attività stomatica (Barbour et al 2000, Scheidegger et al 2000, con conseguente riduzione delle perdite di acqua per traspirazione, ed una maggiore efficienza dell'attività assimilativa, suggerendo un'elevata efficienza d'uso dell'acqua. Una delle spiegazioni di questa risposta positiva della pianta potrebbe essere in parte legata all'aumento delle emissioni di NO 2 registrato in Svizzera proprio a partire dagli anni '60 ( fig.…”

“…L'albero T 2 mostra un simile andamento del δ O. Il minore arricchimento isotopico dell'ossigeno suggerirebbe un elevato tasso traspirativo, accompagnato da un maggiore "Peclet effect" (Barbour et al 2000). Questo potrebbe indicare una minore sensibilità stomatica alle emissioni si NO 2 per quest'albero che si trova più distante dall'autostrada rispetto a T 1 .…”

Do Oxygen Isotope Values in Collagen Reflect the Ecology and Physiology of Neotropical Mammals?

“…In addition, the δ 18 O values of plants are positively related to height in stratified canopies (Sternberg et al, 1989;Ometto et al, 2005). These patterns are primarily driven by varying temperature, humidity, light, vapor pressure deficit, and the δ 18 O of atmospheric water vapor beneath the forest canopy (Farquhar and Sharkey, 1982;Ometto et al, 2005;Barbour et al, 2007). Given that isotopic differences in canopy and understory vegetation are transmitted to the animals that forage in these strata, it is plausible that oxygen isotopes can distinguish arboreal species from those that feed on or near the forest floor (Krigbaum et al, 2013;Nelson, 2013;Carter and Bradbury, 2015).…”

“…Folivores have higher δ 18 O values than other groups at SSR, which would be expected if they consume leaves that are affected by 18 O enrichment during evapotranspiration (Yakir, 1997). Lack of evidence for 18 O-enriched folivores at EZ may result from the elevated soil moisture and relative humidity at this site, which likely lead to less evaporative enrichment in leaves than at SSR (Ometto et al, 2005;Barbour et al, 2007). Oxygen isotope values are effective at distinguishing arboreal and terrestrial species (Figure 3; Table 4).…”