Abstract
Leaf coloration changes evoke different photosynthetic responses among different poplar cultivars. The aim of this study is to investigate the photosynthetic difference between a red leaf cultivar (ZHP) and a green leaf (L2025) cultivar of Populus deltoides. In this study, ‘ZHP’ exhibited wide ranges and huge potential for absorption and utilization of light energy and CO2 concentration which were similar to those in ‘L2025’ and even showed a stronger absorption for weak light. However, with the increasing light intensity and CO2 concentration, the photosynthetic capacity in both ‘L2025’ and ‘ZHP’ was gradually restricted, and the net photosynthetic rate (Pn) in ‘ZHP’ was significantly lower than that in ‘L2025’under high light or high CO2 conditions, which was mainly attributed to stomatal regulation and different photosynthetic efficiency (including the light energy utilization efficiency and photosynthetic CO2 assimilation efficiency) in these two poplars. Moreover, the higher anthocyanin content in ‘ZHP’ than that in ‘L2025’ was considered to be closely related to the decreased photosynthetic efficiency in ‘ZHP’. According to the results from the JIP-test, the capture efficiency of the reaction center for light energy in ‘L2025’ was significantly higher than that in ‘ZHP’. Interestingly, the higher levels of light quantum caused relatively higher accumulation of QA- in ‘L2025’, which blocked the electron transport and weakened the photosystem II (PSII) performance as compared with ‘ZHP’; however, the decreased capture of light quantum also could not promote the utilization of light energy, which was the key to the low photosynthetic efficiency in ‘ZHP’. The differential expressions of a series of photosynthesis-related genes further promoted these specific photosynthetic processes between ‘L2025’ and ‘ZHP’.
Highlights
With the rapid development of social economy, colored leaf plants are increasingly popular, which have been widely used in road greening, courtyard, and garden embellishment [1]
The different mechanisms of leaf coloration change the physiological and biochemical adaptabilities in plants, especially the photosynthesis, which is often reduced in colored leaf plants to achieve special ecological functions, such as mimic defense and pollination [2]
Photosynthesis is essential for plant growth and development, which incorporates numerous components, including CO2 assimilation pathways, photosynthetic photosystems, and the electron transport system [5,6]
Summary
With the rapid development of social economy, colored leaf plants are increasingly popular, which have been widely used in road greening, courtyard, and garden embellishment [1]. The low photosynthetic capacity restricts the growth and development of colored leaf plants, and the restriction will be further aggravated under adversity stress [3,4], which is considered an important factor, limiting their geographically extensive promotion and application. Photosynthesis is essential for plant growth and development, which incorporates numerous components, including CO2 assimilation pathways, photosynthetic photosystems, and the electron transport system [5,6]. Colored leaf plants are extremely sensitive to the external light environments, which evoke unpredictable effects on photosynthesis. The acclimation of plants to different light environments induces biochemical responses associated with the remarkable plasticity of phenylpropanoid metabolism [9], which provides the possibility for genetic manipulation to improve the photosynthetic efficiency of color leaf plants. Several leaf color-related genes promoting high photosynthetic efficiency have been reported, such as Ygl in Oryza sativa L. ssp
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