# Comprehensive Assessment of the Dynamics of Banana Chilling Injury by Advanced Optical Techniques
## 3 Results  
### Chlorophyll-Fluorescence Analyses  
Irrespective of the device used, the basic fluorescence parameters \(F_{\text{m}}\) and \(F_{\text{v}}\), and especially F\({}_{0}\) (therefore data not shown) remained approx. constant during the entire cold storage in controls (13 \({}^{\circ}\)C) and in fruit stored at 11.5 \({}^{\circ}\)C and rapidly declined completely during simulated shelf-life (Figure 2). At 10 \({}^{\circ}\)C and, more pronounced, at 5 \({}^{\circ}\)C, these parameters continuously declined during cold storage and, again very rapidly in shelf life, as measured with both CFI and with the FluorPen. Differences in these parameters between low temperature treatments (5 \({}^{\circ}\)C and 10 \({}^{\circ}\)C) and controls became significant on day 5. Results obtained with the PAM fluorometers differentiated less clearly treatment effects due to highly variable data. Nevertheless, \(F_{\text{m}}\) and \(F_{\text{v}}\) were also lowest here since day 5. On the other hand, \(F_{\rm v}/F_{\rm m}\) did not or only slightly (5 \({}^{\circ}\)C on day 12, spot measurements) change in all cold-stored samples. \(F_{\rm v}/F_{\rm m}\), however, rapidly declined to very low values within six days of shelf-life at 18 \({}^{\circ}\)C.  
Obtained from the OJIP test analyses of the polyphasic rise of the rapid chlorophyll-fluorescence induction curve with the FluorPen, the performance index (\(PI_{\rm abs}\)) of all samples tended to decline slowly during storage (Figure 3). While this parameter clearly and significantly distinguished between fruit stored at 13 \({}^{\circ}\)C and at 5 \({}^{\circ}\)C, the differences between controls (13 \({}^{\circ}\)C) and bananas kept at 11.5 \({}^{\circ}\)C and 10 \({}^{\circ}\)C were not significant. \(PI_{\rm abs}\) of samples stored at 5 \({}^{\circ}\)C were always lowest except on the first day of storage. Anyway, the performance index of all samples became zero during simulated shelf life. Although the maximum primary yield of PSII (\(F_{\rm v}/F_{\rm o}\)) of bananas stored at 5 \({}^{\circ}\)C also continuously declined, that of the other samples did not. Differences in this parameter were significant only at the 12 th d of experiment. In shelf life, \(F_{\rm v}/F_{\rm o}\) also rapidly declined to (almost) zero. Figure 2: Means (\(\pm\)SD; \(n>6\)) of maximum (\(F_{\rm m}\)) and variable (\(F_{\rm v}\)) fluorescence and of the potential maximum photochemical efficiency of PSII (\(F_{\rm v}/F_{\rm m}\)) of banana fruit measured with FluorCam (**left column**; pixel means of the entire fruit), FluorPen (**mid column**) and with PAM-fluorometer (**right column**) during cold storage (\(\Circ\) circles: 5 \({}^{\circ}\)C; \(\square\) squares: 10 \({}^{\circ}\)C; \(\Delta\) triangles: 11.5 \({}^{\circ}\)C; \(\Diamond\) diamonds: 13 \({}^{\circ}\)C) and shelf life. The vertical dashed line indicates the end of cold storage on day 12 of the experiment. The filled circles reflect the means (the grey horizontal bar shows the respective SD) of all bananas (\(n=76\)), measured before storage. Different small letters indicate significant (\(p<0.05\)) differences between means. Both the maximum photosynthetic quantum yield (\(\alpha\)) and, especially, the maximum light saturated electron transport rates (\(ETR_{\text{max}}\)) of samples stored at 13 \({}^{\circ}\)C tended to increase during the initial storage compared to \"fresh\" untreated fruit (Figure 4). Both parameters were almost always higher in optimally stored controls than in all other samples. During prolonged storage at cold temperatures, values of both parameters started to decline slowly, though changes were statistically insignificant. In contrast to the others, particularly that at 10 \({}^{\circ}\)C, \(ETR_{\text{max}}\) of fruit stored at 5 \({}^{\circ}\)C remained constant during cold storage. For technical reasons, only the latter samples could be measured during simulated shelf life.