Transcription profiling of leaves of four Poplar clones growing in monoculture and stands mixed with Robinia at poor and rich soil sites

P. maximowiczii × P. trichocarpa (Hybride 275), P. maximowiczii × P. trichocarpa (Matrix 11), P. nigra × P. maximowiczii (Max 1) and P. trichocarpa plants were grown in the field, each in monoculture and in stands mixed with Robinia pseudoacacia, at two locations differing in soil nutrient levels. After 2 years of growing under ambient weather conditions, leaf samples were harvested and analyzed by RNA-seq.