# Effects of Different Planting Environments on the Fragrance of _Dalixiang_ (_Oryza sativa_ L.)
## 4 Discussion
\begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Soil Nutrient**} & \multicolumn{2}{c}{**Planting Point**} \\ \cline{2-3}  & **MT** & **GY** \\ \hline Ammonium nitrogen (mg/kg) & 9.42 \(\pm\) 0.072 b & 10.73 \(\pm\) 0.122 a \\ Nitrate nitrogen (mg/kg) & 0.118 \(\pm\) 0.006 a & 0.125 \(\pm\) 0.003 a \\ pH & 6.73 \(\pm\) 0.017 b & 6.88 \(\pm\) 0.039 a \\ Organic matter (g/kg) & 26.38 \(\pm\) 0.167 b & 41.89 \(\pm\) 0.163 a \\ Total nitrogen (g/kg) & 2.54 \(\pm\) 0.109 b & 3.45 \(\pm\) 0.062 a \\ Total phosphorus (g/kg) & 0.645 \(\pm\) 0.011 a & 0.644 \(\pm\) 0.029 a \\ Total potassium (g/kg) & 11.49 \(\pm\) 0.129 a & 9.57 \(\pm\) 0.052 b \\ Available phosphorus (mg/kg) & 31.75 \(\pm\) 0.296 a & 15.42 \(\pm\) 0.225 b \\ Fast-acting potassium (mg/kg) & 124.43 \(\pm\) 3.766 a & 58.82 \(\pm\) 0.513 b \\ Alkaline hydrolyzable nitrogen (mg/kg) & 128.19 \(\pm\) 0.386 b & 212.52 \(\pm\) 0.696 a \\ \hline \hline \end{tabular} Note: (1) Different lowercase letters indicate significant differences at the \(p\) < 0.05 level. (2) MT: Meitan planting site; GY: Guiyang planting site.  
\end{table} 
Table 2: Differences in nutrient content of soil in different ecological environments. suggests that the Guiyang environment promotes MG biosynthesis, thereby enhancing 2 AP accumulation. Other studies have proposed alternative pathways for 2 AP synthesis. Proline may be converted into 2 AP through the action of proline dehydrogenase (ProDH), which is encoded by the _OsProDH_ gene [32]. Similarly, ornithine can potentially be transformed into 2 AP via the activity of ornithine aminotransferase (OAT), encoded by the _OsOAT_ gene [33, 34]. Our data reveal that _Dulixiang_ rice from the Guiyang planting site had significantly higher levels of proline, ornithine, _OsProDH_ and _OsOAT_ gene expression, as well as ProDH and OAT enzyme activities compared to the Meitan site (Figures 3B,C, 4B,C and 5B,C). This indicates that the Guiyang environment is likely modulated to the levels of proline and ornithine, as well as the expression of associated genes and enzyme activities, contributing to increased 2 AP production. Notably, [PERSON] et al. [35] reported that ornithine can also be converted into 2 AP through a pathway involving ornithine decarboxylase (ODC) and diamine oxidase (DAO), which successively convert ornithine to putrescine and then to \(\gamma\)-aminobutyraldehyde (GAB-ald). [PERSON] et al. [36] further demonstrated that mutations in the _OsODC_ gene lead to a more pronounced increase in 2 AP content, possibly by enhancing ornithine availability. Future research should explore whether similar mechanisms exist for the _OsProDH_ and _OsOAT_ genes. Regarding glutamate, it can potentially be converted into 2 AP through a pathway involving _OsP5 CS_-encoded Delta1-pyrroline-5-carboxylic acid synthetase (P5 CS), which forms Delta1-pyrroline-5-carboxylic acid (P5C), a precursor to 2 AP. However, P5C can also be reduced back to glutamate by Delta1-pyrroline-5-carboxylic acid dehydrogenase (P5 CDH) [37, 38]. Our study showed that _Dulixiang_ rice from Guiyang had significantly lower glutamate levels but higher _OsP5 CS_ gene expression and P5 CS enzyme activity compared to Meitan (Figures 3D, 4D and 5D). We speculate that the Meitan environment promotes the conversion of P5C back to glutamate via P5 CDH, which explains the higher glutamate levels in _Dulixiang_ rice with lower 2 AP content.