Utilising cold plasma seed treatment technologies to delay cotyledon senescence in tomato seedlings

Abstract Cotyledon senescence is an important problem in industrialized seedling production. The effects of cold plasma (CP) treatments with different power levels from 0 to 100 W on the cotyledon chlorosis ratio and abscission ratio of tomato (Solanum lycopersicum L.) seedlings were investigated under normal conditions. CP treatment with 25 W resulted in the lowest ratios of chlorosis and abscission, which significantly inhibited cotyledon senescence. Further study of dark-induced cotyledon senescence indicated that 25 W CP treatment inhibited chlorophyll breakdown, the loss of photosystem II function, and the transcription of senescence-related genes SAG12 and ORE1 during darkness. Transcripts of RBOH1, MAPK1/2 and hydrogen peroxide (H2O2) concentrations were induced by CP treatment under normal conditions and early periods of darkness. However, both antioxidant enzymes and ascorbate-glutathione cycle were activated by CP treatment in late periods of darkness. In addition, the levels of three kinds of cytokinins (CKs) were enhanced, and ethylene concentrations were inhibited by CP treatment during darkness. Taken together, these physiological changes, which were caused by CP treatment, led to a senescence-delayed phenotype of tomato cotyledons. The present study provides a novel CP treatment approach for delaying cotyledon senescence in tomato seedlings, which is an easy, effective, and industrial technology that can significantly improve tomato seedling quality.