Abstract: 【Objective】 The purpose of this study is to explore the relationship between the photosynthetic performance and the decrease in chlorophyll content, and to provide a theoretical basis to breed long duration of active photosynthesis hybrids.【Method】 By simultaneously analyzing chlorophyll a fluorescence transient and light absorbance at 820 nm as well as analyzing net photosynthetic rate and chlorophyll content, the photosynthetic behavior including light absorption, energy transformation and the photo-activities of PSⅡ and PSⅠ during senescence in the stay green inbred line of maize (Zea mays L.) Q319 and the quick-leaf-senescence inbred line of maize HZ4 was studied. 【Result】 Results showed that the net photosynthetic rate, light absorption, energy transformation, the activities of PSⅡ acceptor side and donor side and the PSⅠ activities decreased much slower in stay green inbred line Q319 than in quick-leaf-senescence inbred line HZ4 during the ethephon-induced senescence. Although the chlorophyll content decreased faster in HZ4 with decrease of chlorophyll content induced by ethephon, the photosynthetic performance of Q319 deteriorated much more severely than that of HZ4. 【Conclusion】 The above results indicate that the retention of light absorption, energy transformation and activity of electron transfer contribute to the extended duration of active photosynthesis in the stay green inbred line. It was concluded that attention should be paid to two favorable characteristics in breeding long duration of active photosynthesis hybrids: 1) maintaining more chlorophyll content during senescence and 2) maintaining higher photosynthetic activity during the loss of chlorophyll.

Key words: maize, stay green, senescence, chlorophyll, photochemistry activity, chlorophyll a fluorescence transient