Fig. 6.

Histochemical staining of β-glucuronidase (GUS) and microscopic observations. a non-transgenic tobacco; b transgenic line Z4-12, uidA is regulated by the promoter of Arabidopsis thaliana XYLOGEN PROTEIN 1; c enlargement of the xylem in (b) showing GUS enzyme activity in xylem elements; d transgenic line Z5-2, uidA is regulated by the chimeric promoter 35S-Px; e enlargement of the xylem in (d) showing GUS enzyme activity in xylem elements; f enlargement of the external phloem in (d) showing GUS enzyme activity in phloem cells; g transgenic line 35S-6, uidA is regulated by the cauliflower mosaic virus 35S promoter. Tobacco vein sections were stained with X-gluc. Scale bar = 100. x xylem; p phloem; M meristem; xp xylem ray parenchymal cell; pc parenchymal cell