Study on Nitrate Reductase of Winter Jujube(Ziziphus jujuba var.inermis) NITROGEN STORAGE AND DISTRIBUTION AND REUSE OF ~(15)N-UREA APPLIED IN AUTUMN ON DIFFERENT BRANCH LEAVES OF WINTER JUJUBE(Zizyphus jujuba Mill. var. inermis Rehd) TREES Pattern of spatial distribution and sampling technique of winter jujube black spot Damage of mirid bug Apolygus lucorum to winter jujube at different growth stages