Plant materials and growth conditions
Tomato cultivar ‘Heinz 1706’, ‘Moneymaker’ and ‘Ailsa Craig’ seeds were obtained from Tomato Genetics Resource Center (https://tgrc.ucdavis.edu/) and US National Plant Germplasm System (www.ars-grin.gov/) respectively, and propagated in the greenhouse. Seeds were sterilized in 75% alcohol for 1 minute and 8% NaClO solution for 15 minutes, and washed with autoclaved water for five times, and planted on Murashige and Skoog (MS), non-MS (NMS) and MS with sugar (MSS) medium plates. Dry seeds were directedly sown at the different depth of soil mix containing 40% organic matters. All seedlings were grown in growth chamber at 25°C with 12-hour dark and 12-hour light condition.
Treatments with different lights, salt, heat and plant hormones
For light treatment, sterilized tomato seeds planted on MS growth medium were grown in red and blue light with the intensity of 100 μmol m−2 s−1 for 7 days, respectively. For salt stress and plant hormone treatment, sterilized tomato seeds were planted on MS growth medium supplemented with 150 mM NaCl or plant hormones of different concentrations and grown for 7 days. For heat treatment, sterilized tomato seeds were planted on MS growth medium and grown at 33°C for 7 days.