请问细胞生物学文献里的图谁能看得懂，帮我解释下。谢谢

文献：Repurposing CRISPR as an RNA-guided platform for sequence-specific control of gene expression里

(E) CRISPRi regulation is reversible. Both dCas9 and sgRNA (NT1) are under the control of an aTc-inducible promoter. Cell culture was maintained during exponential phase. At time T = 0, 1 μM of aTc was supplemented to cells with OD = 0.001. Repression of target mRFP starts within 10 min. The fluorescence signal decays in a way that is consistent with cell growth, suggesting that the decay is due to cell division. In 240 min, the fluorescence reaches the fully repressed level. At T = 370 min, aTc is washed away from the growth media, and cells are diluted back to OD = 0.001. Fluorescence starts to increase after 50 min and takes about 300 min to rise to the same level as the positive control. Positive control: always without the inducer; negative control: always with 1 μM aTc inducer.

两个LOG（OD600）的小图，T与R代表的意思，还有negative control如何实现。这3个地方完全不明白，谢谢解答