## 3 Results and Discussion
### Quantitative Analysis and Normalized bOCT Contrast
This internal structural change within the seed  
Figure 4: Averaged normalized bOCT contrast of lentil seeds under control, 200 nm, and 2000 nm alumina exposures throughout a 24 h period. might possibly contribute to the increase in the bOCT contrast observed at 0 h to 6 h after exposure, for all alumina treatments. Comparison of bOCT Results with Conventional Measurements to Understand the Reliability and Observation Speed of the bOCT Technique  
To compare and verify the reliability of the obtained bOCT results, a few conventional measurements, such as germination rate, shoot length, root length, shoot fresh weight, and root fresh weight were obtained after the exposure of three different treatments including a control, 100 mg/L 2000 nm, and 200 nm AlNPs. The percentage of seed germination is one of the common, traditional physiological indicators that is widely used to observe the effect of external agents [21]. Lentil seed germination rates under different alumina exposures are shown in Figure 5. Increments of seed germination were observed for both alumina treatments compared to the control. The germination rates after 40 h of exposures were recorded as 75%, 91%, and 100% for the control, the 2000 nm, and the 200 nm AlNPs, respectively. Hence, the highest germination rate was observed for the 200 nm AlNPs exposure, exhibiting a possible size-dependent positive effect. The results were in agreement with those observed in the bOCT results. However, it takes 40 h to observe a significant difference from seed germination, whereas bOCT takes 6 h to exhibit a significant increment. In this study, to make a comparison with those results obtained by bOCT, the effects of AlNPs on root length, shoot length, root fresh weight, and shoot fresh weight were measured, as shown in Figure 6. The same tendency could be observed for all of the parameters, as seen in the seed germination percentage (Figures S2 and S3). Significant increments (\(p<0.01\)) were observed for 200 nm AlNPs exposure compared to the control for both root length and root fresh weight. Furthermore, shoot length and shoot fresh weight also had significant increments (\(p<0.05\)) for 200 nm AlNPs exposure compared to those obtained from the control. The highest significant increment was observed for the smaller particle size, thus emphasizing a possible size-dependent positive effect. The results were in agreement with the observed bOCT results. Figure 5: Percentage of seed germination under control and exposures of 200 and 2000 nm. The conventional measurements follow the same tendency as the bOCT results. Increments of seed germination percentage, root length, shoot length, root fresh weight, and shoot fresh weight were observed for all AlNPs exposures compared to those of the control. A similar positive effect of AlNPs on root elongation was observed for lettuce (_Lactuca sativa_ L.), whereas a low concentration of alumina was able to enhance biomass when compared to the control condition. Moreover, the results of that study emphasize that the AlNPs can absorb root hair and promote the uptake of macronutrients [9]. The effect of alumina on lentil seed germination and growth is inversely proportional to the particle size, which is the same phenomenon as that seen in the bOCT experiments. However, conventional measurements took a minimum of 40 h to exhibit a significant increment, whereas bOCT took only 6 h, thereby emphasizing the relative observation speed and reliability.