关键词: 番茄, 弱光, 光合荧光特性, 气孔, 叶绿体

Abstract:

【Objective】 The chloroplast ultrastructure and photosynthetic physiological characteristics of two tomato cultivars under low light were studied to reveal the difference of the response of different tomato cultivars to low light and explore the potential of Solanum lycopersicum tolerance to low light. 【Method】 The Dutch low-light tolerance cultivar Glorioso and the Chinese low-light sensitive cultivar Jingdan No. 1 were selected as experimental materials, they exposed to normal light (CK, light intensity 300-350 μmol·m ^-2·s^-1) and 50% normal light (low light, light intensity 70-80 μmol·m ^-2·s^-1) for fifteen days. The plant chlorophyll fluorescence imaging, chlorophyll fluorescence and photosynthetic parameters of leaves were detected. We also observed stomatal morphology and chloroplast ultrastructure of leaves after treatment by the scanning electron microscopy (SEM) and transmission electron microscopy (TEM). 【Result】 Compared with the control, the P_n, q_P__Lss, the content of chl. (a+b), SOD activity, stomatal density and spatial scale of regular stomatal distribution of the two cultivars leaves were decreased, which also led to the decrease of dry weight and healthy index, the leaves NPQ__Lss, MDA content increased with plant height and maximum internode spacing. The variation range of Jingdan No. 1 was significantly larger than Glorioso, the QY__Lss, QY (ΦPSⅡ) and chloroplast structure of Glorioso remained unchanged, its P_n in leaves was significantly higher than Jingdan No. 1. In addition, the Glorioso improved the regular distribution of stomata by reducing the value of L(d) between stomata, chl.b content increased and chl.a/b decreased under low light. While the chl.b content of Jingdan No. 1 decreased, chl.a/b increased, the spatial scale and regularity of stomatal regular distribution reduced and the leaves were seriously affected by low light. To sum up, Glorioso has stronger light-harvesting ability than Jingdan No. 1 under low light, and uses more light energy absorbed by photosynthetic pigments for photochemistry transfer, reduced heat dissipation and improves the actual photochemistry rate, light energy conversion rate of PSII, so as to maintain operation of photosynthetic system under low light, which photosynthetic capacity and output are slightly higher than Jingdan No. 1, and has strong low light tolerance.【Conclusion】 The differences of response to low light between the two tomato cultivars were mainly reflected in chl.b content, stomatal spatial distribution pattern, chloroplast structure, SOD activity and photosynthetic fluorescence characteristics, which made the Dutch cultivar Glorioso maintain high photosynthesis efficiency under low light.

Key words: tomato, low light, photosynthetic fluorescence characteristics, stomata, chloroplast