Figure 4.

SAG12, SAG19, MT1, and Atgsr2 transcript levels were not altered by O₃ treatment. Fifteen-day-old Arabidopsis plants were exposed to 0.15 μL L⁻¹ O₃ for 6 h d⁻¹ or remained nontreated. Samples were prepared as in Figure 3. Each lane contains RNA extracted from the fifth and sixth leaves pooled from six plants. The samples shown are one representative replicate from a total of three. Sen, RNA sample extracted from yellowing (senescent) leaves older than 30 d; C, control, nontreated plants; O₃, O₃-treated plants.