Mechanism Of Cold Plasma Seed Priming In Enhancing Tomato Temperature Stress Resistance

Tomato（Solanum lycopersicum L.）,it is an important eggplant vegetable crop in China.It is vulnerable to abiotic stresses such as low temperature and high temperature in off-season cultivation.It is an important problem of scientific and efficient research and development of plant resistance to stress.In this study,the effect and mechanism of cold plasma seed initiation（CP）in inducing temperature stress resistance of tomato were studied,and the following results were obtained:1.Under sub-high temperature stress,the plant height,stem diameter,stem and leaf dry mass,root dry mass,root shoot ratio and strong seedling index of tomato seedlings increased first and then decreased with the increase of CP treatment power,reaching the peak in the CP treatment range of 25-75W respectively.The comprehensive expression of seedling growth is that 75W CP treatment is the best.Compared with the control,CP treatment increased midday net photosynthetic rate（P_n）,transpiration rate（T_r）,stomatal conductance（G_s）,stomatal limit value（L_s）,decreased intercellular CO₂concentration（C_i）,and comprehensively showed higher water use efficiency（WUE）in the daytime.Meanwhile,CP treatment significantly increased the maximum fluorescence（F_m）,potential photochemical activity（F_v/F₀）,maximum photochemical efficiency（F_v/F_m）,excitation energy capture efficiency（F_v’/F_m’）,actual photochemical efficiency(Φ_PSⅡ),photochemical quenching coefficient（q _P）,chlorophyll fluorescence decay rate(R_fd),excitation energy distribution coefficient of PSⅠ（α）and the share（P）of absorbed light energy used for photochemical reactions when compared with control treatment.The minimum fluorescence（F₀）,non photochemical quenching coefficient（NPQ）,relative limiting value of photosynthetic function(L_PFD),excitation energy pressure of PSⅡ（1–q _P）,excitation energy distribution coefficient of PSⅡ（β）,imbalance of excitation energy distribution between PSⅠand PSⅡ（β/α-1）,share of thermal dissipation of antenna（D）and the share of non photochemical dissipation（E_x）were decreased.2.75W CP seed treatment showed the best mitigative effect on low temperture-induced injury of tomato seedlings,as evidenced by the higher maximum photochemical efficiency of PSⅡ（F_v/F_m）,lower ion leakage and chilling injury index.In addition,the cold resistance of tomato decreased after silencing RBOH1 or exogenous removal of H₂O₂,indicating that CP induced low temperature tolerance is related to hydrogen peroxide（H₂O₂）mediated by respiratory burst oxidase homologue1（RBOH1）.CP treatment could promote RBOH1mediated H₂O₂to activate the transcription of 9-cis-cyclocarotenoid dioxygenase 1（NCED1）to increase the content of abscisic acid（ABA）,while the mutation of NCED1 completely inhibited CP induced low temperature stress tolerance.Genetic evidence showed that H₂O₂and ABA were positive regulators of low temperture stress tolerance.CP-induced H₂O₂and ABA cascade signal up-regulated the regulatory genes（ICE1 and CBF1）of cold acclimation,which increased the osmotic adjustment substances（proline and soluble sugar）accumulation and antioxidant enzymes（SOD,APX and CAT）activities.Results indicate that H₂O₂and ABA signals are involved in conferring low temperture stress tolerance induced by CP seed treatment in tomato plants.To sum up:CP seed treatment can improve the temperature adaptability of tomato seedlings,which lays a theoretical foundation for the application of CP seed treatment technology in vegetable industrialized seedling raising.