Comparative Study On Heat Tolerance Of Different Inbred Maize At Seedling Stage

In this study,four maize（Zea mays L.）inbred lines PH6 WC,PH4CV,S122 and Chang 7-2 were used as materials and seedlings were subjected to heat stress at 32°C,36°C,38°C and 40°C when they had three leaves and one-cord.The changes of chlorophyll,reactive oxygen species（ROS）and the photosynthetic rat e under heat stress were analyzed.The response of photosynthetic system in inbred maize lines to heat stre ss were studied by chlorophyll fluorescence technology,which is beneficial to select heat-resistant parental materials.The results were as follows.（1）The response of maize inbred lines to temperature was different.Plants were injured more seriousl y with increasing time and temperature.Compared with other three varieties,Chang 7-2 was able to mai ntain much higher net photosynthetic rate（Pn）,relative water content（RWC）,chlorophyll and proline con tent at 40°C.The intracellular accumulation of O2·-and H2O2 was also less than that of other three lines.（2）The maximum photochemical efficiency（Fv/Fm）and photosynthetic performance index(PI_abs)o f four varieties decreased with the treatment time extended.PIabs of PH6 WC,PH4CV,S122 and Chang7-2 decreased to the lowest values of 0.23,0.66,0.44 and 0.83 after treated with 40°C for 2 h,respectively.V j and Vi increased and Fo and Fm decreased at 40°C.Compared with other varieties Fv/Fm,PIabs,ABS/CS m,TRo/CSm and ETo/CSm were much higher in Chang 7-2 to mitigate the damage of excess light energy t o photosynthetic mechanism,which can coordinate the electron transfer of photosystems and maintain the s tability of photosynthetic system structure and function.（3）The heat resistance of Chang 7-2 was the best among four varieties.PH4 CV and S122 had moderat e heat tolerance under heat stress,and PH6 WC was more sensitive to high temperature.Under heat stress,mitigating the reduction of the photosynthetic electron transport chain by thermal dissipation can protect t he photosynthetic system in Chang 7-2.The light protection in PH6 WC was at a low level and could not co ordinate electron transport in photosystems under heat stress,and induced photoinhibition.Tangsipingtou g roup chang7-2 maize inbred line can be used as male or female parent for breeding or improvement of hea t resistant lines,which lays a foundation for cross breeding.