Unraveling the Relationship Between Respiratory Metabolism and Post-priming Deterioration in Rice

Seed priming has emerged as an effective and low-cost option to enhance rice seed vigor. However, the fast post-priming deterioration limits its adoption in rice production. The deterioration rate of primed rice seeds was varied across different priming methods, but whether this variation was associated with changes in seed respiratory metabolism remains unknown. In the present study, seeds of rice (Oryza sativa L.) cv. Chuangliangyou627 were subjected to hydro-priming (HP) and osmo-priming with 5% (OP5), 15% (OP15) and 25% (OP25) polyethylene glycol, non-primed seeds were used as control (NP). Subsequent artificial accelerated aging was conducted for 0 h, 48 h and 96 h. Seed deterioration rate, oxygen consumption rate (OCR), respiratory control ratio (RCR), enzyme activities involved in glycolysis and TCA cycle were measured. Results showed that HP accelerated seed deterioration as compared with NP, while OP significantly reduced post-priming deterioration compared to HP, and this protective effect became more pronounced as the OP concentration increased. Similarly, respiratory metabolism was greatly reduced in HP seeds during aging with respect to OCR, RCR and enzymatic activity, whilst OP partially mitigated those negative effects. Furthermore, partial least squares path modeling (PLS-PM) indicated that glycolysis exerted a negative effect on post-priming deterioration, whereas aerobic respiration showed a positive effect. These findings were validated using respiratory inhibitors. Suppressing the TCA cycle during priming significantly retarded deterioration by lowering reactive oxygen species (ROS) accumulation and lipid peroxidation, whereas inhibiting glycolysis accelerated aging. The present study denotes the important role of respiratory metabolism in regulating primed rice seeds deterioration. However, further research is required to elucidate changes in mitochondrial ultrastructure and specific ETC function, as well as to precisely characterize the spatiotemporal patterns of mitochondrial ROS generation during the aging of primed rice seeds.