Enhanced assimilation rate and water use efficiency with latitude through increased photosynthetic capacity and internal conductance in balsam poplar (Populus balsamifera L.)

Abstract

In outdoor common gardens, high latitude populations of deciduous tree species often display higher assimilation rates (A) than low latitude populations, but they accomplish less height. To test whether trends in A reflect adaptation to growing season length or, alternatively, are garden growth artefacts, we examined variation in height increment and ecophysiological traits in a range-wide collection of Populus balsamifera L. populations from 21 provenances, during unconstrained growth in a greenhouse. Rooted cuttings, maintained without resource limitation under 21 h photoperiod for 90 d, displayed increasing height growth, A, leaf mass per area and leaf N per area with latitude whereas stomatal conductance (gs) showed no pattern. Water-use efficiency as indicated by both gas exchange and d 13 C increased with latitude, whereas photosynthetic nitrogenuse efficiency decreased. Differences in d 13 C were less than expected based on A/gs, suggesting coextensive variation in internal conductance (gm). Analysis of A-Ci curves on a subset of populations showed that high latitude genotypes had greater gm than low-latitude genotypes. We conclude that higher peak rates of height growth in high latitude genotypes of balsam poplar are supported by higher A, achieved partly through higher gm, to help compensate for a shorter growing season.

Long-term acclimation of mesophyll conductance, carbon isotope discrimination and growth in two contrasting Picea asperata populations exposed to drought and enhanced UV-B radiation for three years

“…In the populations analyzed, carbon isotope discrimination calculated from leaf ı 13 C ( L ) was always lower than expected on the basis of laboratory gas-exchange results ( i ), suggesting coextensive variation in g m (Soolanayakanahally et al, 2009). Both C i /C a and C c /C a had a negative effect on ı 13 C, but C i /C a always showing a stronger effect under well-watered conditions.…”

“…Flexas et al (2007) emphasized that comparisons of g m in different natural plant populations, and its possible influence on the efficiency of water and nitrogen use should be a research priority. However, the importance of g m to water use efficiency (WUE) is still neglected in most studies (Soolanayakanahally et al, 2009). Carbon isotope composition (ı 13 C) recorded in tissues of C 3 plants has been demonstrated to be a useful tool for assessing WUE (for a review, see Farquhar et al, 1989;Brendel et al, 2002).…”

Local Selection Across a Latitudinal Gradient Shapes Nucleotide Diversity in Balsam Poplar, Populus balsamifera L

“…The 24 sampled accessions are part of the AgCanBaP collection growing in Indian Head, Saskatchewan, Canada (for collection details, see Soolanayakanahally et al 2009). We identified P. balsamifera homologs of A. thaliana phenology genes using BLASTN searches against the P. trichocarpa genome (Tuskan et al 2006).…”

Balsam Poplar (<i>Populus balsamifera</i>; Salicaceae) Beyond the Tree Line in the Western Canadian Mainland Arctic (Northwest Territories)

“…It would also be useful to better our understanding of their ecology, demography, and genetic structure within and among populations in the region, in comparison to the Alaskan North Slope stands, and throughout the range of balsam poplar (e.g., Breen et al, 2009;Keller et al, 2010;Olson et al, 2010). Similar comparative studies of their ecophysiology and phenology could also provide new insight (e.g., Landhäusser et al, 1996;Soolanayakanahally et al, 2009;Keller et al, 2011). Since the whole-genome sequencing of Populus trichocarpa (Tuskan et al, 2006), the first sequenced tree genome, poplar has been established as an important model organism for genomic studies.…”