Transcription profiling of developing xylem of Populus maximowiczii × P. trichocarpa and P. nigra × P. maximowiczii growing pure and mixed with Robinia at poor and rich soil sites

P. maximowiczii × P. trichocarpa and P. nigra × P. maximowiczii plants were grown in the field, each pure and mixed with Robinia pseudoacacia, at two locations differing in soil nutrient levels. After 3 years of growing, samples of developing xylem were harvested and analyzed by RNA-seq.