Effects of drought and shading on instantaneous water use efficiency and δ13C of Pinus massoniana seed-lings
Water use is a key process of photosynthetic carbon sequestration in plants.δ13C is a key indicator for long-term water use efficiency(WUE),reflecting the adaptive ability of plants to stressful environments.It is thus of great significance to reveal the long-term relationship between plants and environment.In this study,we exam-ined the effects of drought and shading on instantaneous WUE and δ13C in Pinus massoniana seedlings under four treatments,including drought(30％saturated water content of soil moisture),shading(30％of full light intensi-ty),drought+shading(30％saturated water content of soil moisture and 30％of full light intensity),and CK(70％saturated water content of soil moisture and full light intensity).The instantaneous WUE in the current-year needles significantly increased by 67.96％and 60.78％under drought and combined stress,respectively.δ13C sig-nificantly increased by 14.35％under drought,but did not significantly change under shading and combined stress.However,the δ13C values did not significantly change in the 1-year-old needles under three treatments.This indica-ted that the changes of instantaneous and long-term water use efficiency were not synchronized in P.massoniana,with WUE responded earlier to drought.The δ13C value in sink organs was higher than that in the source needles under all treatments.Moreover,δ13C in stems and roots had significant correlation with that in needles,which was significantly positively correlated with that in 1-year-old needles.The δ13C value in sink organs was also mainly influenced by the supply of source needles.These results implied that the changes in WUE caused by changing envi-ronments could further affect δ13C in each sink organ,which would provide a reference for the understanding the mechanism underlying the responses of P.massoniana seedlings to climate change.
droughtshadingwater use efficiencyδ1 3CPinus massoniana seedling
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