Abstract: Gerbera jamesonii Bolus (Rionegro) was subjected to dynamic high temperature (32°C/22°C, 35°C/25°C, 38°C/28°C and 41°C/31°C) and duration (4d, 6d, 8d and 10d) treatments in an artificial control experiment with day/night temperatures of 28°C/18°C as control (CK). The physiological indicators related to the photosynthetic, fluorescence, and senescence characteristics of gerbera leaves were measured under different treatments. Based on the results of the correlation analysis and principal component analysis, authors constructed risk indexes for high temperature and heat damage (HT & HD) in Gerbera applicable to the greenhouse in southern China. Combining meteorological data from 366 stations and greenhouse microclimate data from 1990−2019, BP neural network was used to simulate the maximum daily temperature in greenhouses in the southern region as a way to carry out the risk zoning of HT & HD in greenhouse cultivation in the southern gerbera planted region. The results showed that: (1) to create the heat stress index (HSI) of gerbera in the greenhouse, Pn, Pmax, PItotal, Fv/Fm, and POD were extracted as key indicators by principal component analysis. They were classified into three levels: mild (0.2＜HSI≤0.4), moderate (0.4＜HSI≤0.6), and severe (HSI＞0.6), which were then used to determine its heat stress meteorological indicators. (2) The southern China gerbera planting area experienced mild HT & HD on average every 0.19 to 0.90 years between 1990 and 2019, with the majority of these outbreaks occurring in Sichuan and Yunnan's eastern and western regions. In contrast to the mild, moderate HT & HD on average decreased in frequency throughout the south, with a maximum frequency of 0.54 occurring mostly in Guangxi and Guangdong areas. Severe HT & HD occurred 0 to 0.58 times less frequently than mild disasters. (3) In the southern China, the HT & HD to gerbera in the greenhouse from 1990 to 2019 revealed a general trend of high in the south and low in the north. Among these, the Sichuan basin and the eastern and western areas of Yunnan are at low risk, whereas Chongqing, Hubei, Hunan, Jiangxi, Guangxi, Guangdong, Fujian, and Zhejiang are, to a great extent, high-risk regions. Other areas are at medium risk of HT & HD to the gerbera in the greenhouse.

Key words: Gerbera, High temperature and heat damage, BP neural network, Southern China region, Risk zoning