Lack of genetic variation in tree ring δ13C suggests a uniform, stomatally-driven response to drought stress across Pinus radiata genotypes

Abstract

We assessed the variation in δ13C signatures of Pinus radiata D. Don stemwood taken from three genetic trials in southern Australia. We sought to determine the potential of using δ13C signatures as selection criteria for drought tolerance. Increment cores were taken from P. radiata and were used to determine the basal area increment and the δ13C signature of extracted cellulose. Both growth increment and cellulose δ13C were affected by water availability. Growth increment and δ13C were negatively correlated suggesting that growth was water-limited. While there was significant genetic variation in growth, there was no significant genetic variation in cellulose δ13C of tree rings. This suggests that different genotypes of P. radiata display significant differences in growth and yet respond similarly to drought stress. The δ13C response to drought stress was more due to changes in stomatal conductance than to the variation in photosynthetic capacity, and this may explain the lack of genetic variation in δ13C. The lack of genetic variation in cellulose δ13C of tree rings precludes its use as a selection criterion for drought tolerance among P. radiata genotypes.