Characteristics of chlorophyll fluorescence in ten garden shrub species under flooding stress

Chlorophyll fluorescence imaging is an effective method of studying the effects of stress on plants. Notably, flooding stress is one of the most important forms of abiotic stress in plants. The present study explored the spatial and temporal variations in the chlorophyll fluorescence parameters in leaves, and analyzed the various response strategies of different plants under flooding stress. We monitored the changes in the SPAD (Soil and Plant Analyzer Development) values, the chlorophyll content and chlorophyll fluorescence imaging. So that the non-destructive measurement of the changes in the physiological state of ten garden shrub species under flooding stress were performed. The results showed that there were significant correlations between the SPAD value and the measured chlorophyll fluorescence parameters (p < 0.05). Additionally, the rank of the tested species based on comprehensive analysis of the flooding tolerance was listed as follows: Hibiscus syriacus > Euonymus kiautschovicus > Chaenomeles speciosa > Lagerstroemia indica > Sorbaria kirilowii > Euonymus japonicus > Lonicera maackii > Rosa xanthina > Amygdalus triloba > Syringa oblata. The findings revealed that the chlorophyll content assumed a continuous downward trend under flooding stress. Moreover, fluorescence imaging illustrated that the leaves of different plants behaved differently under flooding stress given that some showed spotty damaged areas while others were damaged from the leaf margin. Furthermore, the variation in the chlorophyll fluorescence parameters indicated that the flooding tolerance of plants was probably related to the stability of the maximum light quantum yield (QY_max), increase in the steady-state non-photochemical fluorescence quenching (NPQ_Lss) and the time point of the initial increase.