Correlations of carbon isotope discrimination with element and ash contents in two Sabina evergreen trees in northwest China: patterns and implications

Abstract

Foliar carbon isotope discrimination (Δ) is widely used as an integrator of physiological plant responses to environmental change. However, the relationship between foliar Δ and mineral nutrient accumulation is still not well-known. The foliar Δ, K, Ca, Mg, Si and ash contents of S. przewalskii Kom. (SP) and S. chinensis (Lin.) Ant. (SC), two over-winter trees distributed on high altitude plateaux and lower altitude plains, respectively, were measured at monthly intervals over two years under the same growing conditions to examine the genetic and seasonal variation in foliar nutrient concentrations in relation to foliar Δ. The foliar Δ, Mg, K and ash contents were markedly lower in SP than in SC, and the foliar Si content was significantly higher in SP than SC, while the differences in Ca contents between the two Sabina trees were not significant. There was higher foliar Δ in winter than in summer for both Sabina trees. Close negative correlations of foliar Δ with K and Mg content, and significant positive correlations between foliar Δ and Si contents, were observed in SP but not in SC. Thus, higher water-use efficiency of SP than of SC is related to higher Si and lower Mg and K contents that have positive effects on the reduction of transpiration rates or stomatal conductances. The results obtained by the present study will advance the understanding of the adaptive strategies of mineral nutrition and water use in harsh environments.

Interactions between soil water and fertilizer on leaf photosynthesis and δ13C of Catalpa bungei seedlings

“…The δ 13 C signature of plant is determined by a complex series of functions that which begin with the import of atmospheric 13 CO 2 through the stomata followed by its incorporation into the tissues through a chain of physical and biochemical processes. This sequence of steps is strongly influenced by soil water and fertiliser availability, leaf nutrient status, and water potential (Ehleringer et al, 1991;Welker et al, 1993;Kao & Tsai, 1998;Zhang et al, 2011) through effects on photosynthetic rate and the stomatal mechanism. Plants reduce transpiration through stomatal closure when soil water availability and leaf water potentials are low, thereby increasing leaf δ 13 C values (Cao et al, 2009).…”