Figure legends
Figure 1. Effects of E -2-hexenal (0.5 μL L-1, 2.5 μL L-1, 12.5 μL L-1, 25 μL L-1 E2H liquid volume / sealed space volume) and ethylene (12 mg L-1) on tomato colour development at 0 h and 72 h after treatment (A). Effects of E -2-hexenal (12.5 μL L-1) on the longitudinal section appearances (B) and the surface colour characteristics (C) of the tomatoes at 72 h. The storage temperature was at 20 oC.
Figure 2. The Photos of tomato treated with E -2-hexenal (E2H) (24 h), ethylene (ET) (24 h), ET (12 h) and then E2H (12 h), E2H (12 h) and then ET (12 h) and combined E2H and ET (24 h) at 72 h. The concentrations of the treatments used were E2H (12.5 μL L-1) and ET (12 mg L-1). The storage temperature was at 20 oC.
Figure 3. Electron micrographs of plastids during transformation of chloroplasts to chromoplasts at 72 h pretreated withE -2-hexenal (A-D) and the control (E and F).
Standards for four stages of the plastids were listed in the table (I). Four stages (S1: chloroplast; S2: transition stages 1; S3: transition stages 2 and S4: chromosome) were observed and counted in all the cells captured. The statistically results of the proportions in S1, S2, S3 and S4 stages at 72 h pretreated with E -2-hexenal (H) and the control (G) were analyzed. The plastoglobules (pg) count per plastid were compared between E -2-hexenal group and the control (J). TheE -2-hexenal treatments was 12.5 μL L-1 and the storage temperature was at 20 oC. The inner membranes (im), tubular elements (te), plastoglobules (pg) and crystal remnants (cr) were marked in the photos in red arrows.
Figure 4. Effect of E -2-hexenal (2.5 μL L-1 and 12.5 μL L-1) on the a* value (A); the chlorophyll (B), β-carotene (C) and lycopene (D) contents comparted to that of the control. The storage temperature was at 20oC. Each value represents the mean of three replicates. Bars indicate the standard deviation (±SD). The lower-case letters (a, b and c) indicates differences that are significant atP < 0.05.
Figure 5. Relative expression of the LOXCs (A) andHPLs (B) genes detected in tomato pericarps in response toE -2-hexenal (2.5 μL L-1 and 12.5 μL L-1) and the control. The storage temperature was at 20 oC. Histograms representing the average of three biological samples that were independently assessed. Data were normalized relative to the β-actin -housekeeping gene and referred to the control at time zero. Bars indicate the standard deviation (±SD). The lower-case letters (a, b and c) indicates differences that are significant at P < 0.05.
Figure 6. Scheme of the possible mechanisms of carotenoids activated inner membrane structures transformation in the chloroplasts during tomato fruit colour development.
Ten steps were shown at the yellow spots with latin numbers: (I) the carotenoids are biosynthesis before IMS transform in the chloroplasts; (II) the carotenoids are packed into the IMS; (III) free linolenic acids are released from the IMS; (IV) LOXC decompose the free linolenic acids to produce hydroperoxy-linolenic acid; (V) HPL decompose the hydroperoxy-linolenic acid to produce E2Hs; (VI) The E2Hs are released inside or outside the plastid; (VII) The E2Hs altered the structure of the IMS; (VIII) the te, pg or cr structure in the chromoplasts form and accumulate more carotenoids; (IX) The E2Hs outside one plastid transfer to function in the neighbor plastids; (X) Excessive E2H feedback regulates the HPL enzyme to form a balanced level.