Fig. 2.

Limited storage capacity for nitrate causes day-length-dependent growth reduction. (A) The vha-a2 vha-a3 phenotype is severe if plants are grown under short-day conditions (8 h). Upon extended illumination periods (16 and 24 h) the growth phenotype is attenuated. Pictures show 7-week-old (8 h light) and 3-week-old (16 and 24 h light) plants. (B) Impaired vacuolar nitrate storage causes a reduction of the nitrate content in vha-a2 vha-a3. (C) Maximum nitrate reductase activity and (D) increased glutamine content in vha-a2 vha-a3 are shown. (B–D) HPLC analysis and NR assay were performed on rosette leaves of 3-week-old plants grown in soil under 16-h light/8-h dark cycles. The plant material was collected 5 h after illumination started. Error bars represent SD of four biological replicates.