Analyses of the photosynthetic characteristics, chloroplast ultrastructure, and transcriptome of apple (Malus domestica) grown under red and blue lights

Zhiqiang Li,Qiaojing Chen,Wenjun Liu,Aiyun Gao,Zhuoxin Mei,Zijing Chen,Lei Yu,Youyan Xin,Xuesen Chen,Nan Wang

doi:10.1186/s12870-021-03262-5

Abstract

BackgroundLight quality significantly affects plant growth and development, photosynthesis, and carbon and nitrogen metabolism. Apple (Malus domestica Borkh.) is a widely cultivated and economically important fruit crop worldwide. However, there are still few studies on the effects of different light qualities on the growth and development of apple seedlings.ResultsIn this study, we explored the effects of blue and red light treatments on the growth and development, photosynthetic characteristics, leaf chloroplast ultrastructure, and carbon and nitrogen metabolism of apple seedlings. Blue light significantly inhibited apple plant growth and leaf extension, but it promoted the development of leaf tissue structures and chloroplasts and positively affected leaf stomatal conductance, the transpiration rate, and photosynthetic efficiency. The red light treatment promoted apple plant growth and root development, but it resulted in loosely organized leaf palisade tissues and low chlorophyll contents. The blue and red light treatments enhanced the accumulation of ammonium nitrogen in apple seedlings. Moreover, the blue light treatment significantly promoted nitrogen metabolism. Additionally, an RNA-seq analysis revealed that both blue light and red light can significantly up-regulate the expression of genes related to carbon and nitrogen metabolism. Blue light can also promote amino acid synthesis and flavonoid metabolism, whereas red light can induce plant hormone signal transduction. The expression of a gene encoding a bHLH transcription factor (MYC2-like) was significantly up-regulated in response to blue light, implying it may be important for blue light-mediated plant development.ConclusionsConsidered together, blue and red light have important effects on apple growth, carbon and nitrogen metabolism. These findings may be useful for determining the ideal light conditions for apple cultivation to maximize fruit yield and quality.

Highlights

Light quality significantly affects plant growth and development, photosynthesis, and carbon and nitrogen metabolism
A spectral scan of the apple root system revealed that the total root length, root volume, and number of lateral roots of plants treated with red light were respectively 1.3, 1.7, and 1.6-times greater than the corresponding data for the plants treated with white light
There were no significant differences in the root indices between the plants treated with blue light and the plants treated with white light (Table 1)

Summary

Introduction

Light quality significantly affects plant growth and development, photosynthesis, and carbon and nitrogen metabolism. There are still few studies on the effects of different light qualities on the growth and development of apple seedlings. Light, which is one of the most important environmental factors affecting plant growth and development, is an essential source of energy for plant activities; it influences plant morphogenesis, photosynthesis, metabolism, and signal transduction [1]. Photoreceptors enable plants to sense changes in the external light environment [3]. The photoreceptors that have been identified can be roughly divided into phytochrome, cryptochrome, phototropin, and ultraviolet-B (UV-B) photoreceptors [4, 5]. Phytochrome photoreceptors mainly sense red light and far-red light, cryptochrome and phototropin photoreceptors sense blue light, and UV-B photoreceptors sense UV-B light [5,6,7]. Signaling cascades and transcriptional regulatory networks combine to complete the light response process and regulate plant development [6, 8]

Methods

Results

Discussion

Conclusion