Effect of high-temperature on the quality of pakchoi and its simulation

To explore the effects of high-temperature stress on yield and quality of greenhouse pakchoi, a study was conducted from October 2015 to May 2016.In the study, we set three gradients of daytime/nighttime temperatures of 32℃/22℃, 35℃/25℃, 38℃/28℃, with 25℃/18℃ as the control, and the duration of each treatment was 3 d, 6 d, 9 d and 12 d, respectively.The results showed that:(1) the dry weight, fresh weight, leaf fresh weight, leaf length, leaf width, petiole width, SPAD and per unit area yield decreased with increased high-temperature stress.Furthermore, the decline aggravated with increasing treatment duration.(2) Petiole length and rolled leaf rate increased gradually with increased temperature and duration.High-temperature stress increased the content of crude fiber.Under short-term high-temperature stress condition, the contents of soluble sugar, soluble protein and vitamin C did not change obviously, but gradually decreased due to increased temperature degree and stress duration.(3) A mathematical model of rolled leaf rate and per unit area yield of pakchoi was established and validated by independent experimental data.The root mean square error and relative error of model of rolled leaf rate with minimum temperature and treatment time were small-respectively 7.59% and 0.189 4.The model for yield per unit area with maximum temperature and treatment time were smaller-also respectively 274.02 g·m^-2 and 0.073%.Our study suggests that high-temperature stress downgraded pakchoi appearance quality and internal quality with increasing stress time and degree.Besides, we defined high-temperature stress index and determined high-temperature stress degree for greenhouse pakchoi.The results provided scientific basis for the determination of meteorological indicators and for disaster prevention.